PREOPERATIVE ASSESSMENT
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 should be 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
minimize 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 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 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 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
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
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.
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.
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. 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.
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 with 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
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.