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Careful preoperative assessment is fundamental to achieving good surgical
outcomes. The same principles apply to both emergency and elective situations, the
only difference usually being the extent to which preoperative assessment must be
compromised when an emergency condition requires urgent intervention
Assessment of operative fitness and perioperative risk
When making the decision to operate, the risks and potential benefits of surgery
shouldbe
weighed
against
those
of
alternative
or
no
treatment.
The purpose of preoperative assessment is to prepare the patient for surgery,
identify co-morbid conditions, estimate and minmis perioperative risk by optimizing
the patient's physical condition.
The majority of preoperative assessment for elective surgery takes place in the
preoperative assessment one to two weeks before surgery, and culminates in the
admission immediately prior to,on the morning of, surgery.
The first priority is to establish the severity and extent of the condition requiring
surgery by employing appropriate imaging and other investigations. For example, it
is important to know that both recurrent laryngeal nerves are functional prior to
thyroid surgery as damage is a recognized complication of this type of operation, on
the other hand malignant conditions require appropriate staging to establish the
disease extent.
The second objective
is to identify co-morbid conditions through careful clinical assessment and through
optimization, minimize perioperative risk.
In the emergency situation this process is condensed. Judging the timing of surgery
is crucial. The surgeon must determine which interventions will optimize the
patient's condition while avoiding deterioration due to unnecessary delay
progression of the acute surgical problem
Systematic preoperative assessment
1-Cardiovascular system
The severity of cardiovascular disease is assessed -Angina and previous myocardial
infarction indicate significant coronary artery disease although bypass grafting,
angioplasty and coronary artery stenting may ameliorate their associated risks.
Exertional dyspnoea, orthopnoea and paroxysmal nocturnal dyspnoea may indicate
PREOPERATIVE ASSESSMENT
Surgery D.Muhanned L1
left
ventricular
failure,
whilst
significant
dependent
oedema
could
signify right sided heart failure.
Clinical examination should detect arrhythmias, carotid artery, heart murmurs,
hypertension and signs of cardiac failure. Antiplatelet agents and anticoagulants are
widely prescribed in the general population and may need to be stopped or modified
prior to surgery.
2-Respiratory system
In patients with asthma, chronic obstructive pulmonary disease (COPD) or fibrotic
lung disease, purulent sputum may indicate an infective exacerbation. In asthmatics,
previous ITU and hospital admissions as well as steroid dependency indicate severe
disease. Functional respiratory reserve is best assessed by exercise tolerance, for
example how far a patient can walk on the flat, up an incline, or how many stairs they
can climb before needing to rest because of shortness of breath. Significant dyspnoea
should be investigated with pulmonary function tests.
Patients with features of acute viral respiratory illness should have surgery
postponed where possible. This is due to the increased risk of bronchospasm and
susceptibility to postoperative bacterial pneumonia which is compounded by the
effect of general anaesthesia which depresses ciliary activity, reducing the clearance
of secretions and pathogens
3-
Smoking
All patients should be offered support to quit smoking, particularly once the decision
to operate has been made. should be explained to the patient. Some of the benefits
occur within hours (reduced circulating nicotine and carboxyhaemoglobin) while
others take weeks, months, or even years. Despite the significant advantages in the
perioperative period, many patients are unable or unwilling to stop smoking prior to
and after their surgery.
Benefits of preoperative smoking cessation
• Reduced airway hyper-reactivity / bronchospasm
• Reduced sputum production reduces the risk of atelectasis
• Improved ciliary function results in increased sputum clearance, helping to
protect against infection
• Reduced carboxyhaemoglobin so increases oxygen carrying capacity of blood
• Reduced nicotine related systemic and coronary vasoconstriction.
4-
Alcohol
:
in chronic alcohol abuse, liver enzymes are induced, increasing hepatic drug
metabolism. Consequently, increased doses of hepatically metabolized drugs,
including anaesthetic agents are required to achieve therapeutic effect.
Conversely,
in
acute
alcohol
intoxication
reduced
anaesthetic
Surgery D.Muhanned L1
doses are required. In addition, the risk of aspiration pneumonia should be
anticipated and preventive measures taken. In patients with a significant alcohol
history, the risk of alcohol related liver and cardiac disease and coagulopathy should
be anticipated.
5-Nutritional status
All patients should have their height and weight measured and BMI (body mass
index) calculated. It is important to look for signs of malnutrition such as low BMI,
bodyweight < 90% predicted,> 20% weight loss, hypoproteinaemia and
hypoalbuminaemia as they have all been related to increased rates of postoperative
complications (particularly wound infection and pulmonary) as well as delayed
anastamotic and wound healing. For these reasons, it is important to treat
malnutrition preoperatively if time permits.
6-
Obesity
Obese patients are at increased risk from surgery and anaesthesia and special
equipment may be required. Obese patients are at risk of major associated co-
morbidities (e.g. diabetes, obstructive sleep apnoea, degenerative joint
disease and cardiovascular disease) In practice, the majority of patients cannot
lose weight without support and referral to the GP and dietician for weight loss
programmes, including supervised exercise, may be beneficial.
Drug therapy
A drug history should be recorded prior to admission for surgery. Drugs that require
special consideration in the perioperative period are.
1-Long-term steroid therapy
Increased circulating cortisol is an important part of the metabolic response to
surgical stress. .Long-term steroid therapy may result in hypoadrenalism and the
inability to mount an effective response to surgical stress. It is therefore
important that patients receive steroid therapy throughout the perioperative period.
An increased steroid dose is usually necessary to counter surgical stress for all but
minor procedures. High doses (100 mg hydrocortisone every 6 hours) may be needed
if the risk of hypoadrenalism is compounded further by postoperative complications
including infection. Signs of hypoadrenalism include hypotension/ shock,
hyponatraemia and hyperkalaemia.
2-Antiplatelet therapy and anticoagulants
Antiplatelet therapy with aspirin, clopidogrel and dipyridamole is common. The risk
of thromboembolic events, particularly myocardial infarction, if antiplatelet therapys
withdrawn is should be weighed against the risk of surgical haemorrhage if
treatment is continued.
Where possible, surgery should be postponed and antiplatelet agents withdrawn
only after consultation with a cardiologist or vascular surgeon.Anticoagulation with
warfarin, commonly for prevention of embolic events in atrial fibrillation, and for
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treatment of deep vein thrombosis and pulmonary embolism is also frequently
encountered. The risk of a thromboembolic event.
with anticoagulant suspension has to be balanced against the risk of bleeding in an
anticoagulated patient undergoing surgery. The use of bridging anticoagulation
should be considered .
3-
Oral contraceptives and hormone replacement therapy
Depending on the type of surgery being planned and the patient's other risk factors
for venous thromboembolism, it may be advisable to discontinue oestrogen-
containing drugs (combined oral contraceptive pills [OCP] and hormone replacement
therapy [HRT]) 4–6 weeks before surgery.
4-Psychiatric drugs
Tricyclic antidepressants (TCA) and phenothiazines can both cause hypotension and
TCAs are also associated with increased risks of arrhythmia. In the case of
phenothiazines, the risk of stopping the medication outweighs the potential benefits
but the anaesthetist should be aware of the potential complications. It is
not essential that tricyclic antidepressants be stopped preoperatively, but the
anaesthetist should be alerted.
Lithium should be stopped 24 hours prior to surgery as it mimics sodium, potentiating
the action of neuromuscular blocking agents. Monoamine oxidase inhibitors interact
with opiates and vasopressor agents with the potential of neurological and
cardiovascular
complications.
Ideally,
they
should
be
stopped 2–3 weeks prior to surgery.
Allergies
Common examples in the surgical practice include antibiotics, iodine, adhesive
dressings and latex. Full-blown anaphylactic reactions to latex are rare but some
degree of latex sensitivity is common. Special care has to be taken to clear the patient
environment of latex for those with severe allergic responses as it is common in
gloves and other surgical and anaesthetic equipment.
Pregnancy
Elective surgery should be avoided in the first and third trimesters of pregnancy. The
risk of miscarriage and potential teratogenicity is high in the first trimester and this
is usually encountered in relation to surgery for an acute abdomen at
this stage. Third trimester surgery is associated with significant maternal risks and
premature labour . If surgery is necessary, it is best undertaken in the second
trimester in conjunction with the obstetric team.
Previous operations and anaesthetics
Details of previous anaesthetics including complications, side effects and reactions
should be sought and should alert the anaesthetist to potential anaesthetic
challenges including a difficult endotracheal intubation.
Surgery D.Muhanned L1
Previous
major anaesthetic complications or a suspicious family history should alert
to the possibility of a rare inherited abnormality. Pseudocholinesterase deficiency is
an inherited enzyme abnormality also known as scoline apnoea and is characterized
by prolonged apnoea requiring prolonged ventilation in response to short acting,
depolarizing muscle relaxants such as suxamethonium chloride. Malignant
hyperpyrexia is an inherited autosomal dominant condition characterized by life-
threatening hyperpyrexia.
Preoperative investigations
Preoperative investigations are undertaken to assess fitness for anaesthetic and
identify problems amenable to correction prior to surgery. Preoperative
investigations commonly include haematological, biochemical, radiological,
cardiovascular and respiratory tests.
Haematology
Full blood count
The majority of patients undergoing surgery will have a preoperative full blood
count. The oxygen carrying capacity of blood (haemoglobin concentration) is
importance but the platelet and white cell count are also important considerations
in terms of haemostatic capacity
. Any patients undergoing
Wherever possible, anaemia should be corrected preoperatively to optimize oxygen
delivery to the tissues. Preoperative blood transfusion should only be considered
for haemoglobin concentrations below 8 g/dl. surgery with the potential for
significant blood loss should have a full blood count, as should those with signs or
symptoms of anaemia, patients with significant cardiorespiratory disease that may
compromise oxygen delivery to the tissues and those with overt or suspected blood
loss (for example gastrointestinal tract symptoms).
An abnormally elevated white cell count may indicate infection or haematological
disease and should be investigated preoperatively. Thrombocythaemia increases
the risk of thromboembolism and prophylactic measures should be taken.
Thrombocytopenia may need to be corrected to reduce the risk of bleeding. The UK
blood transfusion service recommends transfusing to a platelet count of 50 × 109/l
for lumbar puncture, epidural anaesthesia, endoscopy with biopsies and surgery.
Coagulation screen
The indications for coagulation studies include suspected abnormal clotting,
anticoagulation treatment and consideration of epidural anaesthesia. When
disseminated intravascular coagulation (DIC) is suspected, such as in sepsis,
fibrinogen, fibrinogen degradation products (FDP) and D-dimers should be
measured. The surgical implications of selected disorders of coagulation
are considered below.
Surgery D.Muhanned L1
Biochemistry
Urea and electrolytes
Analysis of urea and electrolytes (U&E) is not necessary in young patients presenting
for minor surgery. Elderly patients and those presenting for major surgery, as well as
patients with renal dysfunction, cardiovascular disease,fluid balance problems
including dehydration and patients on diuretic therapy or any drug therapy that may
affect electrolyte balance or renal function should all have routine blood urea and
electrolyte analysis.
Liver function tests
All patients with known liver disease, significant alcohol consumption or signs of liver
disease should have liver function tests measured.
Cardiac investigations
Electrocardiography (ECG) is of very limited value in predicting the risk of ischaemic
events and generally should only be performed in the elderly (over 65 years), to
detect occult rhythm disorders or signs of previous cardiac events. In younger
patients ECG should be restricted to those wit signs of, or known, cardiovascular
disease and those with risk factors for ischaemic heart disease. Routine chest X-ray
should only be performed in the context of cardiovascular assessment where
congestive cardiac failure is suspected. Echocardiography is used to assess cardiac
function (left ventricular ejection fraction in particular) and may be indicated prior to
major surgery and in patients with suspected valvular disease and heart failure.
Cardiopulmonary exercise tests (CPEX). CPEX is a dynamic test of cardiopulmonary
reserve that is used selectively to help select patients for high risk surgery such as
thoracic, vascular and cardiac surgery.
Respiratory investigations
Patients with purulent sputum suspected of having a chest infection should have
sputum culture and antibiotic sensitivity performed. Preoperative chest X-ray is a
useful baseline in patients with known or suspected pulmonary disease,
and may demonstrate consolidation, atelectasis and pleural effusions. Routine chest
X-ray is not indicated, having poor sensitivity to detect new respiratory disease.
Pulmonary function tests are useful to gauge severity and reversibility of the
obstructive component of respiratory disease.
Informed consent
Informed consent is central to the practice of surgery, and has to be obtained for
surgical procedures, other treatment modalities, investigations, screening tests and
prior to patient participation in research.
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Capacity exists if a patient can:
• understand and retain the information presented
• weigh up the implications, including risk and benefit of
the options
• communicate their decision.
Circumstances where the capacity to consent may not
exist:
• children
• mental illness
• fluctuating or irreversible loss of cognitive function
• patients subject to undue coercion.