Anesthesia and pain relief

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 1corrective treatment of any preoperative infections, and 2appropriate perioperative prophylactic antibiotic cover, to avoid subacute bacterial endocarditis. And to take 3care of anticoagulants. Patients with cardiac disease need careful preoperative evaluation. Much can be derived from a detailed history including exercise tolerance and drug history. 3Echocardiography has enabled noninvasive assessment of cardiac function. Any 4electrolyte abnormality (especially hypokalaemia) or 5anaemia should be corrected and the circulatory volume should be maintained at normal level. 6Perioperatively, the presence of an adequate urine output is a useful indicator of adequacy of the circulating volume.
Operative procedures create an Aincreased demand for oxygen due to pain, Bsurgical stress and Ctemperature 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 1perioperative physiotherapy, 2early mobilization and 3treatment of infection. 4Measurement of oxygen saturation and 5blood 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 1nasogastric aspiration and 2careful correction of fluid and electrolyte balance before anaesthesia is induced. 3H2 -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 Ano hypovolaemia occurs and that a Bgood urine output is present before induction, by the preoperative infusion of intravenous crystalloid solutions. CA diuretic agent should only be used if the circulating volume is first assessed to be adequate.
Metabolic disorders
1-Familial porphyria and 2-hyperpyrexia are hereditary metabolic disorders associated with high anaesthetic risks. 3-Phaeochromocytoma is also associated with severe anaesthetic complications. The presence of these disorders requires highly specific preanaesthetic planning.
4-Diabetes and 5-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 measurement during anaesthesia. An 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 510 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 (14-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).
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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 2.04.2. 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.
The1 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.2Antithrombotic 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 1airway laser surgery or 2endoscopy, and is popular for 3cardiopulmonary bypass. It is also indicated in 4spinal surgery during neurophysiological monitoring of cord integrity, as evoked potential signals are suppressed by inhalational anaesthesia. AAIntravenous 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 or 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.


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 patients 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 2030 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 patients 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 patients willingness and ability to co-operate, as well the surgeons and anaesthetists 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 haematoma, 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.
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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. (Biers block is commonly used for procedures such as reduction of Colles 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 bluebrown 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 (Biers 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 patients 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 intravenously 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:
1- first rung: simple analgesics aspirin, paracetamol, NSAIDs, tricyclic drugs or anticonvulsant drugs;
2- second rung: intermediate strength opioids codeine, tramadol or dextropropoxyphene tricyclic drugs or anticonvulsant drugs
3- 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.
1 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.
2Nerve 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.
3Nerve 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;
5intravenous 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.










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