Anesthesia and Pain Relief pdf - D. Talib

Anesthesia and Pain relief

Preparation for anesthesia

Recognition  of  general  medical  and  specific  anaesthetic  risk  factors
facilitates  the  implementation  of  pre-emptive  measures  and  improves
patient  safety

. Early assessment, liaison with the anaesthetist and appropriate

investigations  avoid  unnecessary  delays.  In  any  case,  the  anaesthetist  who  is  to
be  present  during  the  operation  should  assess  the  patient  preoperatively  and
participate in the preparation for surgery.

Preoperative evaluation and management

Investigation of the general condition of the patient before surgery should

be specific according to the general history and clinical signs.

Investigations

in fit people are unnecessary and uneconomic, but indicated tests should be
performed as early as possible, preferably before admission.

Routine

haematological and biochemical screens, with electrocardiography and chest
radiography, are prudent investigations in elderly people receiving general
anaesthesia for all but not minor surgery

. The saving of a serum sample for

transfusion cross-match, a check for hepatitis antigen and HIV is amust now , a
sickle-cell screen, if indicated, should not be forgotten.
In Iraq hydatid cyst &TB are common disease so chest xray is indicated in most
general anesthetic operations

Cardiovascular disease

Uncontrolled  hypertension  and  angina,  dysrhythmias  and  cardiac  failure  are
common  reasons  for  postponement  of  elective  procedures.  Correction  of
hypertension and ischaemic heart disease is essential and needs to  be continued
through the operative period, even though the patient may be unable to take oral
drugs.  Fast  atrial  fibrillation  needs  to  be  controlled  before  anaesthesia.
Symptomatic  disorders  of  sinoatrial  conduction  require  pacemaker  insertion
before anaesthesia, as do all cases of either Mobitz type 2 second-degree block or
third-degree  heart  block.  In  an  emergency,  transvenous  temporary  pacing  wires
or  external  pacing  can  be  used.  Modern  variable-rate  demand  pacemakers  may
require resetting to fixed rate  mode, but are generally stable during anaesthesia.
However, a cardiological opinion should be sought, bipolar diathermy employed
if possible and the . diathermy plate should be positioned so that the current does
not cross the heart or pacemaker wires.

Recent  myocardial  infarction  is  a  strong  contraindication  to  elective
anaesthesia. There is a significant mortality from anaesthesia within 3months of
infarction,  and  elective  procedures  should  ideally  be  delayed  until  at  least  6
months have elapsed.

Patients  with  valvular  heart  disease  will  need

corrective treatment of any

preoperative infections, and

appropriate perioperative prophylactic antibiotic

cover, to avoid subacute bacterial endocarditis. And to take

care of

anticoagulants.  Patients  with  cardiac  disease  need  careful  preoperative
evaluation.  Much  can  be  derived  from  a  detailed  history  including  exercise
tolerance  and  drug  history.

Echocardiography has enabled noninvasive

assessment of cardiac function. Any

electrolyte abnormality (especially

hypokalaemia) or

anaemia should be corrected and the circulatory volume

should be maintained at normal level.

Perioperatively, the presence of an

adequate urine output is a useful indicator of adequacy of the circulating volume.
Operative procedures create an

increased demand for oxygen due to pain,

surgical stress and

temperature loss. Patients with cardiac disease may need a

period of elective postoperative mechanical pulmonary ventilation

after

surgery,  until  the  period  of  raised  oxygen  consumption  has  passed.  The  careful
anaesthetist and surgeon plan such care before surgery.


Respiratory disease
Thoracic  surgical  procedures  demand  specific  preoperative  tests  of  respiratory
function  including  spirometry  and  blood  gas  analysis.  In  general  surgical
practice,  respiratory  infection  and  asthma  are  the  common  problems  needing
treatment  before  anesthesia.  In  chronic  respiratory  failure,  careful  attention
should  be  given  to

perioperative physiotherapy,

early mobilization and

treatment of infection.

Measurement of oxygen saturation and

blood gas

tensions preoperatively give a very useful guide to future values on recovery.

The need for postoperative ventilatory support should be anticipated.

Regional anaesthesia as appropriate is advantageous in respiratory disease.

Upper abdominal and thoracic procedures are unsuited to regional anaesthesia
alone, as positive pressure ventilation under general anesthesia is necessary.

Gastrointestinal disease

Aspiration  of  gastric  contents  carries  a  high  risk  of  acid  pneumonitis,
pneumonia and death. Regurgitation in the presence of a hiatus hernia, or from
‘  the  full  stomach  ’  ,  may  result  from  emergency  (non  starved)  cases,  bowel
obstruction  or  paralytic  ileus  and  indicates  mandatory  precautions  during
anaesthesia.  A  rapid  sequence

induction is conducted, in which the

patient  is  ‘  preoxygenated  ’  and  cricoid  pressure  is  applied  from
loss  of  consciousness  until  the  lungs  are  protected  by  tracheal
intubation.
     Bowel obstruction requires preoperative

nasogastric aspiration and

careful

correction of fluid and electrolyte balance before anaesthesia is induced.

H2 -

receptor blocking agents such as ranitidine are administered if there is an
increased risk of regurgitation, ideally at least 2 hours preoperatively.
Anaesthesia in the presence of jaundice

carries a high risk of renal damage.

The

anaesthetist should ensure that

no hypovolaemia occurs and that a

good urine

output is present before induction, by the preoperative infusion of intravenous
crystalloid solutions.

A diuretic agent should only be used if the circulating

volume is first assessed to be adequate.

Metabolic disorders

Familial porphyria and

hyperpyrexia

are hereditary metabolic disorders

associated with high anaesthetic risks.

Phaeochromocytoma

is also associated

with severe anaesthetic complications. The presence of these disorders requires
highly specific preanaesthetic planning.

Diabetes and

adrenal suppression from steroid therapy

are also common

metabolic disorders which complicate anaesthesia. Non insulin-dependent
diabetic patients on diet and oral hypoglycemic agents will need blood sugar الى

هن

-----------------------------------------

measurement

during

anaesthesia.

intravenous infusion of glucose may be required if the long-acting hypoglycemic
effects persist even if the agent was omitted on the day of surgery.

Except for minor surgery, an intravenous infusion of glucose with soluble insulin
is likely to be necessary with close monitoring and control of blood sugar levels.
Insulin-dependent diabetes always needs preoperative conversion to control with
rapidly acting soluble insulin by intravenous infusion on the operative day, and
this is continued until the patient has recovered from the operation.

In practice

for  maintenance  of  blood  sugar  levels,  it  is  best  to  keep  a  constant  infusion  of
5—10  per  cent  glucose  with  potassium  supplementation  through  a  separate
intravenous  channel  at  about  2  litres/24  hours.  Soluble  short-acting  insulin  is
given  continuously  by  intravenous  syringe  pump,  with  the  rate  indicated  by
frequent (1—4-hourly) measurement of blood glucose concentration.

The plasma

potassium level needs careful control. The

circulating volume should be

manipulated independently via a separate infusion of normal saline,

blood or

colloid.

In this way a steady control of blood glucose concentration can be easily

achieved by an experienced nurse.

Patients who are receiving corticosteroids

or who have received them in the past 2 months require

supplemention with

hydrocortisone during and after surgery to avoid adrenal insufficiency
(Addisonian crisis).

Coagulation disorders
Whether iatrogenic (including therapeutic) or pathological in origin,

coagulation

disorders need careful assessment before surgery with a coagulation screen, or
clotting factor and platelet measurements.

In acquired disorders, such as

disseminated intravascular coagulation

(DIC), fresh frozen plasma or

cryoprecipitate and platelets

may be given to the patient by the anaesthetist

perioperatively to control haemorrhage. Patients receiving therapeutic

warfarin

need to cease treatment several days preoperatively and have prothrombin time
(PT) measurement until the International Normalised Ratio

(INR) falls to about

1.5 from the therapeutic range of 2.0—4.2.

At an INR of 1.5, surgical

haemostasis should be achieved.

Vitamin K

can be used to hasten the reversal of

warfarin but it is a long-acting agent and can cause weeks of resistance to
warfarin after surgery, so it is better to avoid it.

When the risk of thrombosis and

embolism is high, an intravenous infusion of heparin can be used to replace
warfarin.

The heparin can be stopped or reversed with

protamine

for the period

of surgery. Rapid control of heparin activity is easy, but it is not so with
warfarin.

Neurological disease
In

cerebral disease and trauma

hypoxia, hypercarbia and respiratory obstruction

raise intracranial pressure and can cause cerebral damage

. In the presence of

deteriorating consciousness, management of the

airway and ventilation

is of

prime importance, and especially so in traumatic injury in which early

endotracheal intubation

and pulmonary ventilation should precede supine

positioning for computed tomography (CT) of the brain. Particular

care of the

neck during intubation is necessary

if a

cervical fracture is suspected.

Skull

traction and awake intubation under local anaesthesia are sometimes used.

Anticonvulsant drugs

must be continued during surgery on

epileptic

patients, and

this may necessitate using intravenous administration.
In peripheral

neuropathies and myopathies

, the

need for prolonged periods of

postoperative ventilation should be anticipated.

Anaesthesia and psychiatric disease

General Anaesthesia. ,

rather than regional, anaesthesia is usually necessary.

Tricyclic antidepressants and monoamine oxidase inhibitor

drugs potentiate

sympathomimetic  agents  so  adrenaline  and  cocaine  must  be  avoided.  Pethidine
can also cause hypertension with these drugs. Other narcotic analgesic agents can
be  used  but  caution  is  necessary  as  their  side  effects  can  be  potentiated,
especially with monoamine oxidase inhibitors.

Starvation before surgery

Standard practice for many years has been 6 hours ’ abstinence from food and 4
hours  ,abstinence  from  fluids.  Recently,  there  has  been  a  shift  to  permit  clear,
non fizzy fluids up to 2 hours preoperatively. These rules apply whenever loss of
protective  laryngeal  reflexes  may  pertain,  as  during  regional  anaesthesia  and
sedation.  Small  children  are  usually  given  a  glucose  drink  about  4  hours
preoperatively to prevent perioperative hypoglycaemia.

Consent for surgery and anaesthesia

Informed consent should be obtained by the surgical team, preferably the
operating surgeon, before any sedation is given, but the anaesthetist should still
explain anaesthetic procedures, especially regional and spinal techniques, and
discuss potential sequelae.

Preoperative drugs and treatment

Preoperative

sedative and analgesic

medication is becoming

much less

common.

Heavy sedative, antiemetic, antitussive, amnesic medication was

previously used for the relatively unpleasant inductions of anaesthesia with
pungent inhalational agents. Except for patients who are already in pain,

opioid

analgesic  agents  are  generally  first  given  during  induction  of  anaesthesia,
administered intravenously for rapid onset of action prior to surgery.
            For reduction of anxiety, oral short-acting

benzodiazepines

are now more

commonly used 2-4 hours preoperatively, especially for children. Oral

trimeprazine

is also still popular for children.

For the increasing numbers of day-

case procedures, preoperative sedation is avoided so as to promote rapid
emergence from anaesthesia and mobilisation.

The

anticholinergic

agents,

atropine, glycopyrronium and hyoscine,

are used to

reduce respiratory and oral secretions. They are not essential with modern
anaesthetic agents, but still useful for

airway surgery and endoscopy

. Atropine

and glycopyrronium also

protect against vagal dysrhythmias

, for which

administration  at  induction  is  just  as  effective,  and  can  cause  alertness  and
tachycardia.  Hyoscine  is  pleasantly  sedative  without  the  cardiac  effects  of
atropine,  but  it  can  cause  excessive  sedation  in  infants  or  the
elderly.

Antithrombotic

prophylaxis is usually initiated preoperatively in major

surgery, commonly by subcutaneous heparin injection. Particular attention must
be given to higher risk patients such as women taking

contraceptive and hormone

replacement drugs,

and those undergoing

pelvic, hip, knee and cancer surgery

Low dose progesterone preparations may be effectively covered by subcutaneous
heparin, but other less commonly prescribed forms of contraceptive hormone
treatment may need to be stopped 1 month before major surgery.

Preoperative chest physiotherapy, possibly with bronchodilator treatment,

may be indicated

. If indicated,

prophylactic antibiotic

agents are given by the

anaesthetist in concert with the surgeon, either with the premedication or
intravenously at induction of anaesthesia.

General anaesthesia

Induction of anaesthesia

Intravenous injection

is most common in contemporary practice, although the

recent introduction of nonpungent sevoflurane has led to renewed use of

Inhalational induction.

Inhalational induction is useful in young

(children, or ‘

needle phobic ’ adults, and may also be used in patients who are at risk of airway
obstruction)

(of, for example, blood) when the patient is put into the lateral

position with head down tilt to drain the fluid away from the trachea.
      For  intravenous  induction,  propofol  with  its  rapid  recovery  is  replacing  the
short-standing  barbiturate  agent,  thiopentone.

. Analgesic agents

are

frequently also injected at the time of anaesthetic induction.

Maintenance of anaesthesia

Following the induction of anaesthesia,

inhalational volatile or intravenous

(anaesthetic agents)

are continuously administered to maintain an adequate depth

of anaesthesia. Adding

nitrous oxide

contributes analgesic and weak anaesthetic

effects, which reduce the concentration of volatile anaesthetic agent required for
maintenance. To provide a safety margin, at least 30 per cent oxygen is added to
the  inspired  mixture.  Although  still employed  in  some  parts  of  the  world,  ether
has  generally  been  replaced  by  halothane,  and  isoflurane.  Desflurane  and
sevoflurane are the most recently introduced agents, conferring the advantages of
fewer  side  effects  and  more  rapid  recovery.  The  use  of  nitrous  oxide  is  slowly
waning,  as  oxygen-enriched  air  with  volatile  or  intravenous  maintenance  gains
popularity.

(type of ventilation)

If compressed sources of oxygen, nitrous oxide or air

are scarce, then air may be drawn into the anaesthetic circuit, either by the
(unparalysed) patient ’ s own respiratory effort or by a mechanical ventilator.
(

(Total intravenous anaesthesia),

a technique undergoing contemporary

resurgence, avoids the use of inhalational anaesthetic agents and is claimed to
provide

enhanced quality and rapidity of recovery.

It is also used when

inhalational anaesthesia may be impractical, such as during

airway laser surgery

endoscopy, and is popular for

cardiopulmonary bypass. It is also indicated in

spinal surgery during neurophysiological monitoring of cord integrity

evoked potential signals are suppressed by inhalational anaesthesia.

Intravenous anaesthesia avoids atmospheric pollution, and is usually

conducted by infusing propofol and a short acting opioid analgesic agent, such as
fentanyl or alfentanil, in combination with neuromuscular block and pulmonary
ventilation with a mixture of air and oxygen.

Management of the airway during anaesthesia

General anaesthesia reduces the tone of the muscles required to preserve
airway patency

, and hence the need for

manual methods

(e.g. jaw thrust), or

devices

such as the

Guedel

laryngeal mask airways

, or

endotracheal tubes

. Sir

Ivan  Magill  developed  the  endotracheal  tube  during  World  War  I  to  facilitate
plastic surgery around the mouth without a face mask. The addition of a cuff to
the  tube  allowed  a  seal  of  the  trachea  to  protect  the  lungs  from  aspiration  of
blood  or  secretions,  and  later

mechanical positive pressure pulmonary

ventilation.

The following means of airway control in the anaesthetised or

unconscious patient are used (Fig. 6.1)
.

Positioning of the tongue and jaw

The  anaesthetist  thrusts  the  jaw  forward,  from  behind  the  temporomandibular
joints, thereby elevating the tongue off the posterior pharyngeal wall, which may
also  be  achieved  by  inserting  an  artificial  oropharyngeal  airway  such  as  the  ‘
Guedel ’ .  The  anaesthetic gases are given through a face  mask.  The

laryngeal

mask airway

(LMA) is also inserted via the mouth, and is positioned with the

mask  over  the  larynx,  sealed  by  an  inflatable  cuff.  It  frees  the  anaesthetist  ’  s
hands  from  holding  the  patient  ’  s  jaw  or  face  mask.  Its  placement  is  less
stimulating than endotracheal intubation. It has proved to be a reliable means of
maintaining  a  patent  airway,  and  is  a  technique  readily  taught  to  non
anaesthetists  for  emergency  airway  management.  It  is  likely  to  replace  the  face
mask for immediate care prior to endotracheal intubation.
The endotracheal tube may be passed into the trachea via either the mouth or the
nose. It is usually placed by direct laryngoscopy, using a laryngoscope, but it is
occasionally  impossible  to  visualise  the  larynx.  A  fibreoptic  technique  may  be
used in which the tracheal tube is ‘ rail-roaded ’ over the flexible laryngoscope,
once the tip has been steered into the trachea. A cuffed endotracheal tube is used
to  facilitate  artificial  ventilation  or  surgery  around  the  face  or  airway,  and  to
protect the lungs if there is a risk of pulmonary aspiration. If fluid may collect in
the  mouth  from  above  (as  in  nasal  surgery),  a  throat  pack  is  placed  in  the
oropharynx.  Although  endotracheal  intubation  is  generally  straight  forward,
complications do occur:
accidental and unrecognised oesophageal intubation;
accidental intubation of a main bronchus;

trauma to larynx, trachea or teeth; aspiration of vomitus during neuromuscular
blockade for intubation;
failure to intubate and loss of airway control; •disconnection or blockage of the
tube;
delayed tracheal stenosis, in children or after prolonged intubation.

Careful observation of physical signs and constant vigilance, aided by pulse
oximetry, capnography of the expiratory gases, inspiratory oxygen concentration
measurement and ventilator disconnection alarms are mandatory to minimise
these risks.

الى هنا
Tracheostomy tube
Anaesthesia can safely be conducted through a tracheostomy tube but it should
have  an  inflatable  cuff  for  airway  control.  Silver  or  fenestrated  tracheostomy
tubes  should  therefore  be  replaced  by  plastic  cuffed  tubes  at  induction  of
anaesthesia.

Endobronchial tube
In  pulmonary  and  open  oesophageal  surgery,  selective  intubation  of  either
bronchus is usual to facilitate deflation of the lung on the operated side. Its use is
essential to protect the normal lung in the presence of a bronchopleural fistula.

Ventilation through a bronchoscope
The lungs can be ventilated during bronchoscopy by intermittent jets of oxygen
down a cannula within the bronchoscope. The oxygen entrains air by the Venturi
effect  to  generate  enough  pressure  and  flow  to  inflate  the  lungs.  The  technique
demands constant observation of the patient’s chest movement.

Neuromuscular blockade during surgery

Pharmacological blockade of neuromuscular transmission provides relaxation of
muscles  to  facilitate  surgery  and  mechanical  positive  pressure  ventilation.
Muscle tone may also be reduced by very deep anaesthesia, but may compromise
the circulation. Neuromuscular blockade demands complete control of the airway
and  ventilation  by  the  anaesthetist.  The  depolarising  muscle  relaxant,
suxamethonium,  rapidly  provides  excellent  intubating  conditions  of  brief
duration,  but  commonly  causes  postoperative  diffuse  muscle  pains,  and  rarely
may  cause  a  prolonged  block  if  the  patient  is  deficient  in  plasma

pseudocholinesterase.  The  competitive  neuromuscular  blocking  agents  such  as
curare and its  modern successors produce a prolonged effect which  may  persist
into  the  postoperative  period.  Atracurium,  cisatracurium,  vecuronium  and
rocuronium  share  more  predictable  activity  profiles  and  are  less  dependent  on
hepato-renal  function.  A  peripheral  nerve  stimulator  is  also  used  to  check  for
adequate depth of blockade during surgery, and to confirm satisfactory recovery
of  neuromuscular  function  prior  to  extubation  of  the  trachea.  The  advent  of
neuromuscular  blockade  in  the  1940s  facilitated  many  advances  in  abdominal
and  thoracic  surgery,  but  introduced  the  risk  of  accidental  patient  awareness
during surgery.

Haemostasis and blood pressure control

Although  the  dangers  of  profound  hypotension  are  nowadays  well  accepted,  a
20—30  per  cent  reduction  of  mean  arterial  blood  pressure  from  the  awake
preoperative  level  in  fit  patients  is  still  deemed  acceptable,  and  can  greatly
improve the quality of the operative field and reduce total blood loss.

Reduction

of venous pressure at the wound by correct patient positioning and avoidance of
any  causes  of  venous  obstruction  ,and  maintenance  of  satisfactorily  deep
anaesthesia  and  slightly  reduced  arterial  carbon  dioxide  tension,  further
contribute  to  providing  a  dry  surgical  field.  Hypotensive  drugs

may be used to

produce deliberate controlled hypotension if there is a clear surgical benefit to be
obtained,  although  preservation  of  cerebral  perfusion  and  oxygenation  remains
paramount.  The  surgeon  must  be  aware  of  the  prevailing  blood  pressure,
particularly  at  the  time  of  ensuring  satisfactory  haemostasis  prior  to  wound
closure. Usually, the anaesthetist will attempt to bring the blood pressure back to
the normal level at this stage of the procedure.

Management of temperature during anaesthesia

Hypothermia  develops  quickly  during  anaesthesia  and  surgery  due  to
vasodilation, cold infusions of fluid, and loss of body heat by radiation and fluid
evaporation from open body cavities. It is a particular hazard in children because
of  the  high  ratio  of  body  surface  area  to  body  mass.  .The  elderly  are  also  at
particular  risk  as  hypothermia  and

shivering

increase oxygen consumption and

vascular resistance, predisposing to myocardial infarction. In high-risk patients
and for long operations, warm air blowers and warming blankets should be used,
and fluids for intravenous infusion, or irrigation of body cavities or organs (such
as the bladder and renal pelvis), should be warmed to body temperature.

Careful intraoperative temperature control greatly reduces postoperative
morbidity.

Monitoring during anaesthesia

Accurate  monitoring  of  vital  functions  during  anaesthesia  is  now  regarded  as
obligatory in all parts of the world. Surgery should not be practised where proper
facilities for monitoring and cardiopulmonary resuscitation are not available. The
basic  parameters  monitored  are  inspiratory  oxygen  concentration,  oxygen
saturation  by  pulse  oximetry,  expiratory  carbon  dioxide  tension  measurement,
blood pressure and the electrocardiogram.
       For major surgery, invasive, direct monitoring of the circulation is used, but
the  potential  value  of  information  gained  must  be  weighed  against  the  possible
dangers of placing intra arterial or central venous or pulmonary artery catheters.
Hourly  observation  of  urine  output  via  a  urinary  catheter  is  most  helpful  in
assessing renal perfusion.   Ventilators should all have airway pressure monitors
and disconnection alarms.
        In  the  UK,  the  Association  of  Anaesthetists  recommends  the  following
standards of routine monitoring in the anaesthetised patient.

•  the continuous presence of an adequately trained anaesthetist;
•  regular blood pressure and heart rate measurements (recorded);
•  continuous  monitoring  of  the  electrocardiography  (ECG)  throughout
anaesthesia;
• continuous analysis of the oxygen content in the inspiratory gas mixture;
•  oxygen supply failure alarm;
•  ventilator disconnection alarm;
•  pulse oximeter;
•  capnography (measurement of end-tidal carbon dioxide content);
•   temperature measurement availability;
•    neuromuscular  monitoring  availability.  In  the  USA,  spirometry  during
anaesthesia is regarded as necessary.

Recovery from general anaesthesia

Recovery  from  general  anaesthesia  should  be  closely  supervised  by  trained
nursing  staff  in  an  area  equipped  with  the  means  of  resuscitation  and  with
adequate monitoring devices. An anaesthetist should be readily available.

For the seriously ill patient, a high dependency unit or intensive care unit may be
necessary  until  the  patient’s  condition  is  satisfactory  and  stable.  The  transition
from  tracheal  intubation  with ventilatory  support  to  spontaneous  breathing  with
an  unprotected  airway  is  a  time  of  increased  risk,  when  respiratory  arrest  or
obstruction may occur.

The common causes of failure to breathe after general anaesthesia are

1-obstruction of the airway.
2-central sedation from opioid drugs or anaesthetic agents
3-hypoxia or hypercarbia of any cause.
4-hypocarbia from mechanical overventilation.
5-persistent neuromuscular blockade.
6-pneumothorax from pleural damage during anaesthesia or surgery.
7-circulatory failure leading to respiratory arrest.

Management of blood pressure in the recovery room

Hypotension

This  may  be  due  to  hypovolaemia,  prolonged  vasodilation  or  myocardial
depressant  effects  of  anaesthetic,  drugs,  cardiac  dysrhythmia  or  hypoxaemia.
Management  is  by  treatment  of  the  cause.

Hypertension

Hypertension is

common postoperatively, usually of brief duration and associated with peripheral
vasoconstriction due to pain, fear, cold or shivering, or pre-existing hypertensive
disease.

Hypertension

predisposes to cerebral and myocardial damage, and needs active management.
If it persists in the presence of adequate pain relief, intravenous hydralazine are
useful.  Rarely,  control  with  more  powerful  intravenous  drugs  such  as  sodium
nitroprusside  or  glyceryltrinitrate  is  necessary,  in  conjunction  with  direct  intra-
arterial blood pressure monitoring.

General anaesthesia for day-case surgery

Day-case management already accounts for about 40 per cent of procedures in
UK hospitals and is intended to reach over

60 per cent

. While the principles

remain the same, it is even more necessary for the day-case patient to recover
rapidly from general anaesthesia and mobilise with the minimum of side-effects.

Longer  and  more  complex  operations  are  now  conducted  as  day  cases,
demanding high-quality anaesthesia and effective analgesic strategies.
Careful  selection  of  patients  is  essential  with  regard  to  coexisting  diseases,  the
nature of the proposed surgery, the availability of a suitable escort and transport
home, and domiciliary care. Well-controlled non debilitating chronic diseases do
not  preclude  day  care,  but  may  require  a  longer  period  of  postoperative
supervision  before  permitting  discharge  home.  General  anaesthesia  combined
with  regional  anaesthesia,  as  for  inguinal  hernia  repair,  is  often  suitable.
Anaesthetics  which  promote  rapid  recovery  such  as  propofol,  sevoflurane  and
desflurane  are  used.  Drugs  with  prolonged  depressant  central  action,  including
premedicant  drugs,  are  avoided  and,  where  possible,  analgesics  should  act
peripherally or be  of short duration if centrally acting.  Where possible, patients
are  managed  with  a  laryngeal  mask  or  face  mask,  although  endotracheal
intubation is the necessary airway control for many day cases such as oral or ear,
nose  and  throat  (ENT)  procedures,  and  is  generally  uncomplicated.  With  the
patient  relatively  isolated  from  immediate  medical  supervision  and  advice,
postoperative analgesia must be carefully tailored to the procedure, especially in
the  case  of  the  more  painful  procedures  (such  as  hernia  repair,
haemorrhoidectomy, tubal surgery, meniscectomy) for which stronger analgesics
and  combinations  should  be  provided.  Regular  postoperative  dosing  is
recommended  to  avoid  breakthrough  pain,  as  may  particularly  occur  following
the initial benefits of local anaesthetic.

General anaesthesia and cardiopulmonary bypass

Anaesthetic agents and oxygen cannot be delivered to the circulation through the
lungs when the lungs are bypassed, so all drugs are given directly into a vein or
into the blood while it passes through the oxygenator.

Local anaesthesia

     Choice  of  a  local  anaesthetic  technique  depends  upon  its  feasibility  for  a
particular  procedure  and  the  patient’s  willingness  and  ability  to  co-operate,  as
well  the  surgeon’s  and  anaesthetist’s  preference.  Local  anaesthesia  may  be  the
reliable and traditional method for some minor surgical procedures which do not
warrant  general  anaesthesia.  One  of  the  main  advantages  is  the  continuation  of
pain  relief  into  the  postoperative  period,  by  either  drugs  with  a  prolonged
duration  of  action  or  delivery  of  further  local  anaesthetic  increments  via  a
catheter.

However,  local  anaesthesia  is  not  infallible,  and  may  be  contraindicated  by
allergy  or  local  infection.  Epidural  and  intrathecal  anaesthesia  includes
sympathetic  blockade  which  may  result  in  vasodilatation  and  systemic
hypotension, and may confer greater intraoperative risk than a carefully managed
general  anaesthetic.  Complications  may  be  local,  such  as  infection  or  haema-
toma,  or  systemic  if  overdosage  or  accidental  intravascular  injection  leads  to
toxic  blood  levels.  The  latter  may  manifest  as

depressed conscious level,

convulsions and/or cardiac arrest (particularly bupivacaine), and may be heralded
by circum-oral paraesthesia and light-headedness.

Addition of adrenaline to the

local anaesthetic solution increases the risk of cardiac arrhythmia associated with
accidental

intravascular

injection.

Prilocaine

overdosage

cuase

methaemoglobinaemia.  Recently  introduced  local  anaesthetics  such  as
ropivicaine and laevobupivacaine are claimed to have enhanced safety profiles.
      Addition of adrenaline (commonly 1:200000-1:125000 concentration) to the
local anaesthetic solution hastens the onset and prolongs the duration of action,
and permits a higher dose of drug to be used as it is more slowly absorbed into
the  circulation.  Adrenaline  should  not  be  used  in  hypertensive

patients, IHD,

cardiac dysrrhythemies or for patients taking either monoamine oxidase inhibitor
or tricyclic antidepressant drugs,

as its cardiovascular effects are potentiated. It

should  not  be  used  in  end  arterial  locations,  where  there  is  no  collateral
circulation, such as ear, penis, fingers, and toes, or around the retinal artery. The
potential  risk  of  life  threatening  sequelae  mandates  the  availability  of
appropriately skilled personnel and resuscitation equipment including oxygen, as
prerequisites  if  local  anaesthesia  is  practised.  The  following  exemplify  sensible
upper dose limits suitable for a 70 kg adult.
الى هنا

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////

• Lignocaine 200 mg (10 ml of 2 per cent) or lignocaine with adrenaline (1:200
000)  500  mg.  Lignocaine  1 per  cent  is  effective  for  most  sensory  blocks  and  ’
addition of adrenaline enables a greater volume to be used. Thus, up to 50 ml of
lignocaine  1  per  cent  with  adrenaline  (1:200  000)  can  be  infiltrated  into  the
tissues.
•   Bupivacaine  150  mg  (30  ml  of  0.5  per  cent).  Addition  of  adrenaline  would
enhance the safety of this high dose.

Bupivacaine  is  more  cardiotoxic  than  lignocaine.  Bupivacaine  0.25  per  cent  is
effective  for  sensory  block  against  moderate  stimulus.  Bupivacaine  must  never
be injected into a vein, and is absolutely contraindicated from use for intravenous
regional  anaesthesia.  (Bier’s  block  is  commonly  used  for  procedures  such  as
reduction of Colle’s fracture and carpal tunnel decompression.) Bupivacaine is a
long-acting drug lasting for about 6 hours.
•   Prilocaine  400  mg  (40  ml  of  1  per  cent).  The  presence  of blue—brown  skin
colour indicates methaemoglobin toxicity.

Topical anaesthetic

agents are used on the skin, the urethral mucosa, nasal mucosa and the cornea.
The agents used are amethocaine, because it is well absorbed by mucosa, cocaine
for its vasoconstrictive properties, lignocaine and prilocatne. A lignocaine and
prilocaine eutectic mixture ( ‘

EMLA

’ cream) is commonly used on the skin of

children before venepuncture.

Local infiltration

This is  the  method  most  commonly used by both surgeons and physicians. It is
not necessary to starve the patient preoperatively unless the procedure carries  a
high risk of intravascular or intrathecal injection. Infiltration of local anaesthetic
drug  may  be  into  or  around  a  wound,  ideally  with  particular  attention  to
neuroanatomical territories and boundaries. Contraindications are local infection
and  clotting  disorder.  Not  only  local  infiltration  will  spread  the  infection,  but
local  anaesthetic  drugs  are  ineffective  in  conditions  of  acidity  as  produced  by
infection.  Local  infiltration  in  the  presence  of  a  clotting  disorder  may  result  in
haemorrhage,  or  may  produce  haematoma,  potentially  fatal  in  the  airway,  as  in
dentistry.

Regional anaesthesia (without general anaesthesia)

   Regional  anaesthesia  involves  blockade  of  major  nerve  trunks  which
innervate the site of surgery. It is usually performed by an anaesthetist with the
necessary  skills.  However,  both  intrathecal  (spinal)  and  epidural  anaesthesia
should  only  be  conducted  by  experienced  practitioners  using  full  aseptic
techniques.  It  is  in  any  case  required  that  a  doctor  other  than  the  operator  is
present  to  monitor  continuously  and  resuscitate  the  patient  if  necessary.  If
regional anaesthesia fails, general anaesthesia may be necessary.

Compensation  for  an  inadequate  regional  block  by  heavy  sedation  carries  great
dangers  including  airway  obstruction  and  pulmonary  aspiration  of  gastric
contents.  These  may  easily  go  unrecognised  by  a  single-handed  operator.  All
patients should be starved preoperatively and monitored. In emergency surgery,
regional  anaesthesia  carries  the  advantage  of  preservation  of  the  protective
laryngeal  reflexes,  particularly  in  emergency  obstetric  anaesthesia,  for  which
epidural  or  spinal  regional  anaesthesia  is  commonly  the  method  of  choice.  The
reduction  in  blood  pressure  with  spinal  and  epidural  anaesthesia  can  be
advantageous  in  reducing  intraoperative  blood  loss,  but  only  if  the  surgeon
strives to achieve haemostasis prior to wound closure and restoration of normal
blood  pressure.  When  sedation  has  been  used  for  surgery  under  regional
anaesthesia, respiratory obstruction may occur postoperatively when the surgical
stimulus  has  ceased.  Oxygen  saturation  measurement  by  pulse  oximetry  is
required  monitoring  during  regional  anesthesia.  Regional  anesthesia  had  a  very
clear  advantage  over  general  anesthesia  when  general  anesthetic  agents  carried
high  morbidity  and  mortality  rates.  In  contemporary  practice  this  advantage  is
less  pronounced  or  even  reversed.  However,  regional  anesthesia  may  be
advantageous  for  patients  who  have  debilitating  respiratory  disease.  In
cardiovascular  disease,  general  anesthesia  with  support  of  the  circulation  and
pulmonary ventilation is often more advantageous than risking hypotension and
tachyarrhythmias  exacerbating  ischaemic  heart  disease  and  resultant  angina,
which  may  occur  with  regional  anaesthesia.  Regional  anaesthesia  does  provide
excellent analgesia into the postoperative period, reducing the need for centrally
acting  analgesic  agents.  The  most  clear  indications  for  spinal  and  epidural
anaesthesia  are  in  obstetric  practice  to  spare  the  mother  from  the  risk  of
pulmonary aspiration because of the full stomach usually present in labour, and
also  to  spare  the  newborn  from  the  depressant  action  of  the  general  anaesthetic
and analgesic drugs.

General and regional anaesthesia combined

       Combining  the  two  methods  of  anaesthesia  in  well-balanced  measure
enables  a  patient  to  receive  a  lighter  general  anaesthetic  and  to  have  the
advantage of good postoperative analgesia. At its simplest, the infiltration of an
abdominal  wound  with  local  anaesthetic  agent  will  facilitate  comfortable
breathing in the recovery room.

Regional local anaesthetic techniques

Spinal,  plexus  and  major  nerve  blockade  may  be  employed  alone  or  in
combination with sedation or general anaesthesia. It is most commonly used for
limb,  abdominal  and  thoracic  surgery,  and  obstetric  analgesia  and  surgery.  It  is
imperative  that  a  second  medical  practitioner,  and  not  the  surgical  operator,  is
responsible  for  supervision  and  monitoring  of  the  patient  during  the  procedure.
Preoperative  patient  preparation  for  elective  regional  anaesthesia  includes  that
required  for  general  anaesthesia,  with  explanation  of  the  local  anaesthetic
procedure. In emergency, it is safer to use regional anaesthesia on an unstarved
patient  rather  than  general  anaesthesia,  for  the  risk  of  aspiration  of  gastric
contents  is  much  reduced  although  not  absent.  Some  forms  of  regional
anaesthesia  with  long  acting  drugs,  such  as  epidural  bupivacaine  anaesthesia,
result in prolonged motor block and may be unsuitable if the patient is expected
to  be  an  ambulant  day  case.  The  recently  introduced  subcutaneous  low-
molecular-weight heparins (LMWH) for prophylaxis for deep venous thrombosis
are  longer  acting  than  heparin,  and  appear  to  have  increased  the  risk  of
intraspinal  haematoma.  Epidural  and  spinal  injections  (and  catheter  insertion  or
removal)  should  only  be  performed  at  least  12  hours  after  a  LMWH  dose,  and
the  next  LMWH  dose  delayed  for  at  least  2  hours.  The  LMWH  doses  must
therefore  be  timed  appropriately.  As  with  many  perioperative  management
issues,  optimal  care  depends  upon  close  liaison  between  anaesthetist  and
surgeon.  Electrocardiogram,  pulse  oximetry  and  blood  pressure  measurements
should  be  performed  during  regional  anaesthesia.  Oxygen  by  face  mask  should
be given to frail or sedated patients during surgery.

Common local anaesthetic techniques

In  awake  patients  the  nerve  blocks  must  provide  comprehensive  numbness
throughout the surgical field. The following field blocks are commonly used.
• Brachial plexus block for surgery on the arm or hand.
•  Field  block  for  inguinal  hernia  repair.  The  iliohypogastric  and  ilioinguinal
nerves are blocked immediately inferomedial to the anterior superior iliac spine.
The  genitofemoral  nerve  is  infiltrated  at  the  midinguinal  point  and  at  the  pubic
tubercle. If a large volume of local anaesthetic is used, the peritoneal sac can be
anaesthetised before the incision, but care  must be taken to avoid drug toxicity.
Local anaesthetic with 1:200 000 adrenaline prolongs the duration of action and
reduces  toxicity  by  producing  vasoconstriction.  The  line  of  the  skin  incision
should be infiltrated with the mixture.

• Regional block of the ankle. This can be used for surgery on the toes and minor
surgery of the foot.

Intravenous regional anaesthesia

The  arm  to  be  operated  on  is  exsanguinated  by  elevation  and/or  compression,
and then isolated from the general circulation by the application of a tourniquet
inflated to a pressure well in excess of the systolic. arterial pressure. The venous
system is then filled with local anaesthetic agent, injected via a previously placed
indwelling  venous  cannula.  The  drug  diffuses  from  the  bloodstream  into  the
nerves to produce an effective block. The arm is more suitable for this procedure
(Bier’s  block)  than  the  leg  because  the  large  volume  of  drug  required  for  the
latter  can  easily  lead  to  toxicity.  (1)The  tourniquet  must  only  be  deflated  after
adequate time has elapsed (at least 20 minutes) to allow for the residual venous
drug  load  to  fall  to  a  safe  level,  before  it  is  washed  back  into  the  general
circulation.  Cardiac  arrest  or  convulsions  may  well  occur  if  the  tourniquet  is
accidentally  released  before  the  drug  is  fixed;  this  was  particularly  noted  with
bupivacaine, which has been banned from use in this procedure after reports both
of a number of deaths and of directly toxic effects on the heart. Prilocaine 0.5 per
cent up to 50 ml is recommended as the safest agent to use. As above, a separate
medical  practitioner  should  supervise  the  block  and  monitor  the  patient,  while
the surgeon operates.

lntrathecal anaesthesia

Spinal anaesthesia in the awake patient is useful for some forms of surgery in
the pelvis or lower limbs. Hyperbaric solutions of bupivacaine are injected as a ‘
single shot ’ into the cerebrospinal fluid, to produce rapidly an intense blockade,
usually within 5 minutes.

Autonomic sympathetic blockade results in

hypotension, necessitating prior intravenous fluid loading and titration of
vasoconstrictor drugs

. If the hypobaric solution is allowed to ascend too high,

severe  hypotension  and  ventilatory  failure  occur.  This  factor  limits  the  use  of
spinal  anaesthesia  to  surgery  below  the  segmental  level  of  T5.  Postoperative
headache,  due  to  cerebrospinal  fluid  leakage  through  the  dural  perforation,  is
nowadays  much  less  common  as  a  result  of  modern  needles  (very  fine  with  a
round or pencil point tip and side aperture) designed to split rather than cut the
dural  fibres.  Spinal  anaesthesia  is  much  used  for  Caesarean  section,
prostatectomy and lower limb surgery.

Intrathecal opioid drugs are used to produce postoperative analgesia but there is a
significant risk of respiratory depression.

Epidural anaesthesia

         Epidural anaesthesia is slower in onset than intrathecal anaesthesia, but has
the  advantage  of  multiple  dosing  and  hence  prolonged  use,  as  an  indwelling
catheter may be threaded into the epidural space. Hence, epidural anaesthesia can
provide  good  pain  relief  extending  into  the  postoperative  period.  Urinary
retention  is  common,  necessitating  catheterisation  of  the  bladder.  Epidural
anaesthesia also includes sympathetic blockade, but it is of slower onset, as is the
resulting  hypotension,  which  may  be  easier  to  control  and  can  be  used  to
advantage  for  the  surgery,  in  reduction  of  blood  loss.  If  a  weak  solution  of
bupivacaine or the newer ropivicaine is chosen, epidural anaesthesia can be used
to produce a predominantly sensory block for analgesia after upper abdominal or
thoracic surgery. The contemporary trend is to combine weak solutions of local
anaesthetic with opioid agents such as the lipid-soluble diamorphine or fentanyl,
the latter producing analgesia by their action on the opioid receptors in the spinal
cord. However, the potential complication of epidural opioid analgesia is delayed
respiratory arrest from rostral spread and central depression, as late as 24 hours
after the last dose. Hence, regular monitoring of conscious level and respiratory
rate, and facility to immediately reverse the opioid with intravenous naloxone or
to resuscitate, are essential prerequisites.

Epidural anaesthesia (with bupivacaine

or ropivicaine) remains the standard method of anaesthesia during painless
labour and interventional delivery. In contrast to local anaesthetic agents,
epidural opioid agents alone do not produce hypotension

, so they are preferable

for patients who are mobile. There is a current trend towards their use in labour
for this reason, but alone they would not produce adequate analgesia for surgical
intervention.

Caudal epidural anaesthesia

is produced by injection of local

anaesthetic agent through the sacrococcygeal membrane. Its main uses are to
supplement general anaesthesia and for very effective postoperative pain relief.
This analgesic technique is much used in paediatric surgery.

Perioperative pain relief (acute pain management)

Optimal management of acute postoperative pain requires planning, patient
and staff education, and tailoring to the type of surgery and the needs of the
individual patient.

Patients vary greatly (up to eight-fold)

in their requirement for

analgesia,  even  after  identical  surgical  procedures.  Under-treatment  results  in
unacceptable levels of pain with tachycardia, hypertension, vasoconstriction and
‘ splinting ’ of the affected part. Painful abdominal and thoracic wounds restrict
inspiration,  leading  to  tachypnoea,  small  tidal  volumes,  and  inhibition  of  the
patient  from  effective  coughing  and  mobilisation.  This  predisposes  to

chest

infection, delayed mobilisation, deep venous thrombosis, muscle wasting and
pressure sores

. However, analgesic administration above the patient’s

requirement  increases  the  risks  of  side  effects  such  as  nausea,  vomiting,
somnolence and dizziness or, if greatly in excess, severe central effects including
depressed  consciousness  and  respiration.  This  is  fortunately  rare,  and  can  be
avoided  by  sensible  initial  dosing  followed  by  titration  until  the  patient  is
comfortable.  Exaggerated  fears  of  opioid  induced  central  depression  and
addiction have led all too commonly to inhibition amongst staff from prescribing
and  administering  adequate  doses  of  opioids.  Intermittent  intramuscular  dosing
also leads to delays in administration of the ‘ controlled ’ opioids compounded
by the time to onset of action. As a result of these common deficiencies, a( Joint
Working  Party  of  the  Royal  Colleges  of  Anaesthetists  and  Surgeons  was
convened,  which  published  the  report  Pain  after  Surgery  in  1990).  It
recommended  the  establishment  of  acute  pain  teams,  comprising  medical  and
nursing  specialists,  to  oversee  the  implementation  of  guidelines  for  practice
including routine recording of pain levels, and educating both staff and patients.

Combinations of analgesic methods [local anaesthesia and nonsteroidal anti-
inflammatory drugs (NSAIDs) with opioid drugs]

were advocated, as were the

more  sophisticated  methods  of  pain  management  such  as  ‘  patient-controlled
analgesia ’ . The Working Party report also encouraged further use of combined
treatments (termed balanced analgesia) such as with:
•local anaesthetic blocks — excellent short-term analgesia, but requires skill and
has  a  small  failure  rate.  Continuous  catheter  techniques  prolong  pain  relief  but
are only appropriate for inpatients;
•spinal  opioids  —  generally  very  useful  for  appropriate  types  of  surgery,  but
again  requires  skill,  and  is  limited  by  concerns  over  severe  respiratory
depression;

•NSAIDs — in combination reduce requirement for opioids and alone are useful
for  moderate  pain,  but  are  limited  by  concerns  over  side  effects,  such  as  renal
impairment,  peptic  ulceration  and  inducing  acute  bronchospasm  in  asthmatics.
They are not adequate as sole analgesic therapy after major surgery.    The report
called  for  further  research  and,  amongst  other  aims,  hoped  for  the  advent  of  a
powerful  analgesic  on  a  par  with  morphine,  but  without  marked  respiratory
depressant  activity.  While  the  development  of  tailor-made  opioid  agonists  with
differential  receptor  activity  has  not  yet  solved  this  problem,  attention  turned
more  to  finding  alternative  pathways  at  which  to  attenuate  the  afferent  pain
impulses.  For  example,  clonidine  has  been  administered  epidurally  to  stimulate
the  spinal  cord  adrenergic  inhibitory  mechanisms.  Severe  acute  pain  increases
morbidity  after  trauma  or  surgery.  Appreciation  of  pain  pathways  and  the  three
main classes of pain — nociceptive, neuropathic/sympathetic and that of mainly
psychological  origin  —  together  with  enhanced  awareness  of  pain,  has  led  to
new and multimodal treatment strategies.

The methods of prevention are:

•adequate analgesia by intravenous narcotic drugs at the time of surgery;
•regional anaesthesia alone or supplementing general anaesthesia during surgery
to prevent excitation of central pathways;
•the  use  of  prostaglandin  inhibitory  drugs  during  surgery.  Diclofenac
suppositories are effective in reducing the pain from tissue damage in bone and
muscle,  and  are  used  at  the  time  of  operation.  These  three  approaches  used
together  are  good  at  preventing  the  cycle  of  pain  and  muscle  spasm  from
becoming established in the recovery period. The same methods can be used for
managing the pain of acute trauma.

Postoperative pain management

Severe  pain  from  a  large  incision  in  a  frail  patient  may  require  high  doses  of
intravenous  opiate  drugs  leading  to  elective  postoperative  endotracheal
intubation  and  ventilation  until  the  patient  is  stable.  This  approach  should  be
used if the patient is likely to become hypoxic through struggling in pain if other
methods  of  pain  relief  are  not  effective.  Other  methods  of  pain  relief,  properly
used, can usually prevent the need for mechanical ventilation even in very major
thoracic  and  abdominal  surgery.  Acute  pain  relief  teams,  using  continuous
methods of pain relief in high dependency areas well equipped with monitoring,
are becoming a routine feature of the postoperative care in both the USA and the

UK. Regular intramuscular morphine injection, supplemented by anti-
inflammatory analgesic drugs and, possibly, a regional anaesthetic block, are
effective treatment for the majority of surgical patients. Each patient should have
a pain relief measurement chart for regular assessment with other routine nursing
observations.

Special methods of pain relief used under close supervision are

• continuous epidural anaesthesia with opiate or local anaesthetic drugs;
• continuous intravenous opiate analgesia;
•  patient controlled analgesia by injection intravenously or epidurally of opioid
analgesia.  The  patient  is  trained  to  give  a  bolus  dose  of  drug  by  pressing  a
control button on a machine whose functions have been regulated by the medical
staff.  The  strength,  frequency  and  total  dose  of  drug  in  a  given  time  are  all
limited  by  computer.  Effective  postoperative  pain  relief  encourages  early
mobilisation and hospital discharge.

Simple analgesic agents

In minor surgery, and when the patient is able to eat after major surgery, aspirin
and  paracetamol  are  often  the  only  drugs  necessary  to  control  pain.  Fear  of
metabolic  acidosis  and  Reye  ’  s  syndrome  of  hepatotoxicity  in  children  have
made paracetamol a preferable drug to aspirin in the younger age group. Codeine
phosphate is the analgesic favoured after intracranial surgery because it does not
have  a  powerful  respiratory  depressant  effect;  itmay  never  be  given  intra-
venously  as  it  causes  profound  hypotension  on  intravenous  injection.  Patients
with  a  tendency  to  peptic  ulceration  may  need  cover  with  omeprazole  or
misoprostol during analgesic treatment with anti-inflammatory agents.

Chronic pain relief

In  surgical  practice,  the  patient  with  chronic  pain  may  present  for  treatment  of
the  cause  (e.g.  pancreatitis)  or  have  concomitant  pathology.  Surgery  itself  may
have been the cause of the now chronic symptom, as acute pain may progress to
chronic pain. There is a developing belief that inadequate treatment of acute pain
may  make  this  more  likely.  Chronic,  intractable  pain  may  be  of  malignant  or
benign origin and of several types.
•

Nociceptive pain

— pain may result from musculoskeletal disorders or cancer

activating cutaneous nociceptors. Prolonged ischaemic or inflammatory
processes results in sensitisation of peripheral nociceptors and altered activity in
the central nervous system leading to exaggerated responses in the dorsal horn of

the spinal cord. The widened area of hyperalgesia and increased sensitivity
(allodynia) has been attributed to increased transmission of afferent pain
impulses consequent upon this spinal cord dynamic plasticity.
•

Neuropathic (or neurogenic) pain

— dysfunction in peripheral or central

nerves (excluding the physiological pain due to noxious stimulation of the nerve
terminals). Neuropathic pain is classically ‘ burning ’ , ‘ shooting ’ or ‘ stabbing ’
,  and  may  be  associated  with  allodynia,  numbness  and  diminished  thermal
sensation.  It  is  poorly  responsive  to  opioids.  Examples  include  trigeminal
neuralgia,  metatarsalgia,  postherpetic  and  diabetic  neuropathy.  Monoaminergic,
tricyclic and anticonvulsant drugs are the mainstay of treatment.
•

Psychogenic pain

— psychological factors play a greater or lesser role in many

chronic  pain  syndromes.  Whichever  the  primary  cause  may  have  been,
(((depressive illness and chronic pain may exacerbate each other))).
The  treatment  of  pain  of  malignant  origin  differs  from  that  of  pain  of  a  benign
cause, and may be the more difficult to overcome. Drugs, preferably, should be
taken  by  mouth,  but  the  patient  must  be  regularly  reassessed  to  ensure  that
analgesia remains adequate as the disease process changes.

Malignant disease

In  intractable  pain,  the  underlying  principle  of  treatment  is  to  encourage
independence of the patient and an active life in spite of the symptoms. The main
guide  to  the  management  of  cancer  pain  is  the  World  Health  Organisation
Booklet (now in its second edition), which portrays three levels of treatment.
The

‘ pain stepladder ’

includes the following treatments:

first rung: simple analgesics — aspirin, paracetamol, NSAIDs, tricyclic drugs

or anticonvulsant drugs;

second rung: intermediate strength opioids — codeine, tramadol or

dextropropoxyphene ± tricyclic drugs or anticonvulsant drugs

third rung: strong opioids — morphine. (Pethidine has been withdrawn from

the second edition.) Oral opiate analgesia is necessary when the less powerful
analgesic agents no longer control pain on movement, or enable the patient to
sleep.

Fear that the patient may develop an addiction to opiates is usually not

justified

in malignant disease.

Oral morphine can be prescribed in shortacting

liquid or tablet form and should be administered regularly every 4 hours until an
adequate dose of drug has been titrated to control the pain over 24 hours. Once
this is established, the daily dose can be divided into two separate

administrations of enteric-coated, slow-release morphine tablets (MST
morphine) every 12 hours. Additional short-acting morphine can then be used to
cover episodes of ‘ breakthrough pain ’ . Nausea is a problem early in the use of
morphine treatment and may need control by antiemetic agents, e.g.

haloperidol,

methotrimeprazine, metoclopramide or ondansetron

. Nausea does not usually

persist, but constipation is frequently a persistent complication requiring regular
prevention by

laxatives

In fusion of subcutaneous, intravenous, intrathecal or epidural opiate drugs
The  infusion  of  opiate  is  necessary  if  a  patient  is  unable  to  take  oral  drugs.
Subcutaneous  infusion  of  diamorphine  is  simple  and  effective  to  administer.
Epidural  infusions  of  diamorphine  can  be  used  on  mobile  patients  with  an
external  pump.  Intrathecal  infusions  are  prone  to  infection,  but  implantable
reservoirs  with  pumps  programmed  by  external  computer  are  being  used  for
long-term  intrathecal  analgesia.  Intravenous  narcotic  agents  may  then  be
reserved for acute crises, such as pathological fractures. Neurolytic techniques in
cancer  pain  These  should  only  be  used  if  the  life  expectancy  is  limited  and  the
diagnosis is certain. The useful procedures are:
1 •  subcostal phenol injection for a rib metastasis;
2 •  celiac plexus neurolytic block with alcohol for pain of pancreatic, gastric or
hepatic cancer. Image intensifier control is essential;
3 •  intrathecal neurolytic injection of hyperbaric phenol this technique is useful
only if facilities for percutaneous cordotomy are not available as it can damage
motor pathways;
4  •   percutaneous  anterolateral  cordotomy  divides  the  spinothalamic  ascending
pain  pathway  —  this  is  a  highly  effective  technique  in  experienced  hands,
selectively eliminating pain and temperature sensation in a specific limited area.
Alternative strategies include:
5 • the development of hormone analogues, such as tamoxifen and cyproterone,
enables effective pharmacological therapy for the pain of widespread metastases
instead of pituitary ablation surgery;
6  •  palliative  radiotherapy  can  be  most  beneficial  for  the  relief  of  pain  in
metastatic disease;
7  •  adjuvant  drugs  such  as  corticosteroids  to  reduce  cerebral  oedema  or
inflammation  around  a  tumour  may  be  useful  in  symptom  control.  Tricyclic
antidepressants,  anticonvulsants  and,  occasionally,  flecainide  are  also  used  to
reduce the pain of nerve injury.

Pain control in benign disease
Surgical patients may have persistent pain from a variety of disorders including
chronic inflammatory disease, recurrent infection, degenerative bone or joint
disease, nerve injury and sympathetic dystrophy.

Chronic pain may result from

persistent excitation of the nociceptive pathways in the central nervous system,
invoking mechanisms such as spontaneous firing of pain signals at N-methyl-o-
aspartate receptors in the ascending pathways

. Such activity is poorly responsive

to  opiates;  neuroablative  surgery  is  unlikely  to  produce  prolonged  benefit  and
may make the pain worse.
   As is well known, amputation of limbs may result in phantom limb pain, the
likelihood  being  further  increased  if  the  limb  was  painful  before  surgery.
Continuous  regional  local  anaesthetic  blockade  (epidural  or  brachial  plexus),
established  before  operation  and  continued  postoperatively  for  a  few  days,  is
believed to reduce effectively the establishment of phantom pain.

The following are treatments for chronic pain of benign origin

• Local anaesthetic and steroid injections — these can be effective around an

inflamed nerve and they reduce the cycle of constant pain transmission with
consequent muscle spasm. Epidural injections are used for the pain of nerve root
irritation associated with minor disc prolapse. This treatment should be in
association with active physiotherapy to promote mobility.

• Nerve stimulation procedures — acupuncture, transcutaneous nerve

stimulation and the neurosurgical implantation of dorsal column electrodes aim
to increase the endorphin production in the central nervous system altering pain
transmission.

3•

Nerve decompression — decompression of the trigeminal nerve at

craniotomy is now performed for trigeminal neuralgia, rather than percutaneous
coagulation  of  the  trigeminal  ganglion,  in  patients  who  are  fit  for  craniotomy.
Treatment  of  pain  is  dependent  on  sympathetic  nervous  system  activity.  Even
minor  trauma  and  surgery  (often  of  a  limb)  can  provoke  chronic  burning  pain,
allodynia,  trophic  changes  and  resultant  disuse.  The  syndrome  has  been
attributed  to  excessive  sympathetic  adrenergic  activity  inducing  vasconstriction
and abnormal nociceptive transmission. Management mayinclude:

4•

test response to systemic alpha-adrenergic blockade using intravenous

phentolamine;

5•

intravenous regional sympathetic blockade using guanethidine, under

tourniquet;

6•

local anaesthetic injection of stellate ganglion or lumbar sympathetic chain.

Percutaneous  chemical  lumbar  sympathectomy  with  phenol  under  radiographic
control  is  practised  by  both  surgeons  and  anaesthetists  for  relief  of  rest  pain  in
advanced  ischaemic  disease  of  the  legs.  It  can  also  promote  the  healing  of
ischaemic ulcers by improving peripheral blood flow.

Drugs in chronic benign pain
Escalating  doses  of  opioid  analgesic  drugs  are  to  be  avoided,  and  certainly  the
patient  must  not  become  dependent  on  analgesic  injections.  However,  for
debilitating  levels  of  chronic  pain,  opioid  drugs  are  indicated.  Combinations  of
drugs  often  prove  useful  to  achieve  the  optimal  combination  of  efficacy  with
minimal  side-effects.  Paracetamol  and  NSAIDs  are  the  mainstay  of
musculoskeletal pain treatment, but NSAIDs are handicapped by gastrointestinal
intolerance  and  peptic  ulceration.  These  carry  significant  levels  of
noncompliance,  contraindication  and  morbidity.  Specific  cyclo  oxygenase  2
inhibition,  with  preservation  of  protective  cyclo-oxygenase  1  activity,  promises
to  improve  tolerability  and  safety  in  nonsteroidal  anti-inflammatory  treatment.
The tricyclic antidepressant drugs and anticonvulsant agents are often useful for
diminishing  the  pain  of  nerve  injury,  although  side-effects  can  prove
troublesome  and  reduce  compliance.  In  the  management  of  chronic  pain  of
benign  cause,  a  multidisciplinary  approach  by  a  team  using  psychologists,
physiotherapists and occupational therapists under medical supervision can often
achieve much more benefit than the use of powerful drugs. To help the chronic
benign  pain  patients  who  do  not  respond  to  conventional  means,  ‘  pain
management  programmes  ’  have  been  devised,  comprising  a  multidisciplinary
approach  of  painspecialists,  psychologists,  physiotherapists  and  occupational
therapists. They help a number of the patients to cope with the pain and resume a
higher quality life.