Careful Preoperative Assessment

PREOPERATIVE ASSESSMENT

Careful preoperative assessment is fundamental to achievinggood surgical outcomes. The same principles apply toboth emergency and elective situations, the only differenceusually being the extent to which preoperative assessmentmust be compromised when an emergency conditionrequires urgent intervention

Assessment of operative fitnessand perioperative riskWhen 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 thepatient for surgery, identify co-morbid conditions, estimateand minmis perioperative risk by optimizing the patient's physicalcondition.

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 extentof the condition requiring surgery by employing appropriateimaging and other investigations. For example, itis important to know that both recurrent laryngeal nervesare functional prior to thyroid surgery as damage is a recognizedcomplication of this type of operation, on theother hand malignant conditions require appropriatestaging to establish the disease extent.

The second objectiveis to identify co-morbid conditions through carefulclinical assessment and through optimization, minimizeperioperative risk.

In the emergency situation this process is condensed.Judging the timing of surgery is crucial. The surgeon mustdetermine which interventions will optimize the patient'scondition while avoiding deterioration due to unnecessarydelay progression of the acute surgical problem

Systematic preoperative assessment1-Cardiovascular systemThe severity of cardiovascular disease is assessed -Angina and previous myocardial infarction indicate significantcoronary artery disease although bypass grafting,angioplasty and coronary artery stenting may amelioratetheir associated risks. Exertional dyspnoea, orthopnoeaand paroxysmal nocturnal dyspnoea may indicate left ventricularfailure, whilst significant dependent oedema couldsignify right sided heart failure.

Clinical examination should detect arrhythmias, carotidartery, heart murmurs, hypertensionand 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 systemIn patients with asthma, chronic obstructivepulmonary disease (COPD) or fibrotic lung disease, purulentsputum may indicate an infective exacerbation. In asthmatics,previous ITU and hospital admissions as well as steroiddependency indicate severe disease. Functional respiratoryreserve is best assessed by exercise tolerance, for examplehow far a patient can walk on the flat, up an incline, or howmany stairs they can climb before needing to rest because ofshortness of breath. Significant dyspnoea should be investigatedwith pulmonary function tests.

Patients with features of acute viral respiratory illnessshould have surgery postponed where possible. This isdue to the increased risk of bronchospasm and susceptibilityto postoperative bacterial pneumonia which is compounded by the effect of general anaesthesia which depresses ciliary activity, reducing the clearance of secretions and pathogens

3-SmokingAll 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 benefitsoccur within hours (reduced circulating nicotine and carboxyhaemoglobin) while others take weeks, months, or evenyears. Despite the significant advantages in the perioperativeperiod, many patients are unable or unwilling to stop smokingprior 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 sputumclearance, helping to protect against infection• Reduced carboxyhaemoglobin so increases oxygen carryingcapacity of blood• Reduced nicotine related systemic and coronary vasoconstriction

4-Alcoholin chronic alcohol abuse, liver enzymes are induced, increasinghepatic drug metabolism. Consequently, increaseddoses of hepatically metabolized drugs, including anaestheticagents are required to achieve therapeutic effect.Conversely, in acute alcohol intoxication reduced anaestheticdoses are required. In addition, the risk of aspirationpneumonia should be anticipated and preventive measurestaken. In patients with a significant alcohol history, the risk of alcohol related liver and cardiac disease and coagulopathy should be anticipated.

5-Nutritional statusAll patients should have their height and weight measuredand 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 woundhealing. For these reasons, it is important to treat malnutrition preoperatively if time permits

6-ObesityObese patients are at increased risk from surgery andanaesthesia and special equipment may be required. Obesepatients are at risk of major associated co-morbidities (e.g.diabetes, obstructive sleep apnoea, degenerative jointdisease and cardiovascular disease)In practice, the majority of patients cannotlose weight without support and referral to the GP anddietician for weight loss programmes, including supervisedexercise, may be beneficial

Drug therapyA drug history should be recorded prior to admission for surgery. Drugs that require special consideration in the perioperative period are.1-Long-term steroid therapyIncreased circulating cortisol is an important part of themetabolic response to surgical stress. .Long-term steroidtherapy may result in hypoadrenalism and the inability tomount an effective response to surgical stress. It is thereforeimportant that patients receive steroid therapy throughoutthe 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 anticoagulantsAntiplatelet therapy with aspirin, clopidogrel and dipyridamoleis common. The risk of thromboembolic events, particularlymyocardial 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 andantiplatelet agents withdrawn only after consultation witha 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 againstthe risk of bleeding in an anticoagulated patient undergoingsurgery. The use of bridging anticoagulation should beconsidered .

Oral contraceptives and hormonereplacement therapyDepending on the type of surgery being planned and thepatient's other risk factors for venous thromboembolism,it may be advisable to discontinue oestrogen-containingdrugs (combined oral contraceptive pills [OCP] and hormonereplacement therapy [HRT]) 4–6 weeks before surgery.

Psychiatric drugsTricyclic 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 themedication outweighs the potential benefits but the anaesthetistshould be aware of the potential complications. It isnot essential that tricyclic antidepressants be stopped preoperatively, but the anaesthetist should be alerted

Lithium should be stopped 24 hours prior to surgery as it mimicssodium, potentiating the action of neuromuscular blockingagents. Monoamine oxidase inhibitors interact with opiatesand vasopressor agents with the potential of neurologicaland cardiovascular complications. Ideally, they should bestopped 2–3 weeks prior to surgery,

AllergiesCommon 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.

PregnancyElective surgery should be avoided in the first and third trimesters of pregnancy. The risk of miscarriage and potentialteratogenicity is high in the first trimester and this is usuallyencountered in relation to surgery for an acute abdomen atthis stage. Third trimester surgery is associated with significantmaternal risks and premature labour .If surgery is necessary, it is best undertaken in the secondtrimester in conjunction with the obstetric team.

Previous operations and anaestheticsDetails of previous anaesthetics including complications,side effects and reactions should be sought and shouldalert the anaesthetist to potential anaesthetic challengesincluding a difficult endotracheal intubation. Previous

major anaesthetic complications or a suspicious familyhistory should alert to the possibility of a rare inheritedabnormality. Pseudocholinesterase deficiency is an inheritedenzyme abnormality also known as scoline apnoea andis characterized by prolonged apnoea requiring prolongedventilation in response to short acting, depolarizing musclerelaxants such as suxamethonium chloride.Malignant hyperpyrexia is an inherited autosomal dominant condition characterized by life-threatening hyperpyrexia

Preoperative investigationsPreoperative investigations are undertaken to assess fitnessfor anaesthetic and identify problems amenable to correctionprior to surgery. Preoperative investigations commonlyinclude haematological, biochemical, radiological, cardiovascularand respiratory tests.

HaematologyFull blood countThe majority of patients undergoing surgery will have apreoperative full blood count. The oxygen carrying capacityof blood (haemoglobin concentration) is importance but the platelet and white cell count are alsoimportant considerations in terms of haemostatic capacity. Any patients undergoing

Wherever possible, anaemia should be corrected preoperativelyto optimize oxygen delivery to the tissues.Preoperative blood transfusion should only be consideredfor haemoglobin concentrations below 8 g/dl. surgery with the potential for significant blood loss shouldhave a full blood count, as should those with signs or symptomsof anaemia, patients with significant cardiorespiratorydisease that may compromise oxygen delivery to the tissuesand those with overt or suspected blood loss (for examplegastrointestinal tract symptoms).


An abnormally elevated white cell count may indicateinfection or haematological disease and should beinvestigated preoperatively. Thrombocythaemia increasesthe risk of thromboembolism and prophylactic measuresshould be taken. Thrombocytopenia may need to becorrected to reduce the risk of bleeding. The UK bloodtransfusion service recommends transfusing to a plateletcount of 50 × 109/l for lumbar puncture, epidural anaesthesia,endoscopy with biopsies and surgery

Coagulation screenThe 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 coagulationare considered below.

BiochemistryUrea and electrolytesAnalysis of urea and electrolytes (U&E) is not necessaryin young patients presenting for minor surgery. Elderlypatients and those presenting for major surgery, as wellas patients with renal dysfunction, cardiovascular disease,fluid balance problems including dehydration and patientson diuretic therapy or any drug therapy that may affectelectrolyte balance or renal function should all have routineblood urea and electrolyte analysis

Liver function testsAll patients with known liver disease, significant alcoholconsumption or signs of liver disease should have liverfunction tests measured.

Cardiac investigationsElectrocardiography (ECG) is of very limited value in predictingthe risk of ischaemic events and generally shouldonly be performed in the elderly (over 65 years), to detectoccult rhythm disorders or signs of previous cardiac events.In younger patients ECG should be restricted to those withsigns of, or known, cardiovascular disease and those withrisk factors for ischaemic heart disease. Routine chest X-rayshould only be performed in the context of cardiovascularassessment where congestive cardiac failure is suspected.Echocardiography is used to assess cardiac function (leftventricular ejection fraction in particular) and may be indicatedprior to major surgery and in patients with suspectedvalvular disease and heart failure.

Cardiopulmonary exercise tests (CPEX). CPEX is a dynamic test of cardiopulmonary reserve that is used selectively to help selectpatients for high risk surgery such as thoracic, vascular andcardiac surgery.

Respiratory investigationsPatients with purulent sputum suspected of having a chestinfection should have sputum culture and antibiotic sensitivityperformed. Preoperative chest X-ray is a useful baselinein patients with known or suspected pulmonary disease,and may demonstrate consolidation, atelectasis and pleuraleffusions. Routine chest X-ray is not indicated, having poorsensitivity to detect new respiratory disease

Pulmonary function tests are useful to gauge severity andreversibility of the obstructive component of respiratorydisease

Informed consentInformed consent is central to the practice of surgery, andhas to be obtained for surgical procedures, other treatmentmodalities, investigations, screening tests and priorto patient participation in research

Capacity exists if a patient can:• understand and retain the information presented• weigh up the implications, including risk and benefit ofthe options• communicate their decision.Circumstances where the capacity to consent may notexist:• children• mental illness• fluctuating or irreversible loss of cognitive function• patients subject to undue coercion.