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Chapter: Medicine Study Notes : Anaesthetics

Preoperative Assessment

Aim is to investigate and optimise treatment for pre-existing medical conditions before surgery – especially respiratory and CVS.

Preoperative Assessment


·        Aim is to investigate and optimise treatment for pre-existing medical conditions before surgery – especially respiratory and CVS


·        ASA status = American Society of Anaesthetics: 1 = normal, 5 = expected to die, appended E = emergency

·        Cardiovascular conditions requiring assessment:


o   Hypertension: 1/3 develop intraoperative hypotension, and ¼ develop post-operative hypertension. Predisposes to MI, stroke and renal failure. Resting diastolic pressure over 100 mmHg should delay elective surgery until better controlled. Continue previous antihypertensive therapy up to and following surgery to prevent rebound hypertension (esp beta blockers)


o   Coronary vascular disease: IHD ® 10-fold increase of risk of perioperative myocardial infarction. Delay elective GA until 3 (preferably 6) months after an MI

o  Cardiac failure: contra-indication to all but most necessary surgical procedures


o  Arrhythmias: resulting complications more related to underlying pathology rather than rhythm. If cardiac efficiency already reduced, GA can lead to ¯¯ cardiac output (e.g. atrial fibrillation with rapid ventricular response)


o   Valvular and congenital heart disease. E.g. aortic stenosis may require anticoagulant therapy (although this increases haemorrhage risk so stop during operation) and prophylactic antibiotics

·        Respiratory conditions requiring assessment: 

o  Ventilation, gas exchange, cough and mucociliary clearance impaired by GA and into post operative period

o  Major risks: sputum retention, lung collapse, infection, ventilatory failure

o  Preoperative management aims to:

§  Eradicate infection

§  Reduce excess sputum production

§  Treat reversible obstructive disease

§  Treat co-existing right heart failure

§  Optimise ventilatory muscle function 

o  Elective surgery should be cancelled if acute infections up to 5 weeks beforehand. (e.g. viral infections ® ¯mucociliary clearance) 

o   PEFR (Peak expiratory flow rate), FEV1 and VC (Vital capacity) are useful preoperative measures

·        Endocrine:

o  Diabetics are at risk from: 

§  Poor perioperative control: e.g. during pre-operative fasting, stress response, etc. Poor control ® poor wound healing, ­ infection, etc

§  Co-existing cerebral, coronary or renal vascular disease or autonomic neuropathy

o  Hyperthyroid patients at risk of CVS collapse


·        Liver Disease: hepatic function commonly deteriorates post operatively. Infection risk to staff from hepatitis


·        Alcoholism: complications include withdrawal, nutritional abnormalities, existing cardiac and liver disease

·        Anaemia: increases risk of hypotension and hypoxia


·        Drugs: Corticosteroids suppress cortisol, so patients will require supplementation with hydrocortisone at induction and by infusion following




·        GP and RMO should:

o  Determine what medical conditions are present

o  Quantify any impairment and improve as much as possible

o  Make sure appropriate investigations are back in sufficient time before surgery

o  Advise patient of risks and benefits and obtain consent

·        Conditions of note: 

o   Cardiac: MI in previous 6 months, evidence of left or congestive heart failure, unstable or increasing angina, diastolic blood pressure > 110 mmHg, digitalis toxicity, uncontrolled AF

o  Respiratory: respiratory infections, exacerbation of CORD/Asthma

o  Hepatitis

o  Recent stroke

o  Thyroid or adrenal dysfunction

o  Poor control of diabetes

o  Major nutritional disorders

·        Are the following present:

o  Family history of anaesthetic problems

o  Previous anaesthetic problems 

o   Malignant hyperthermia (hypermetabolic response to gases or suxamethonium due to Ca leakage from cytoplasmic reticulum), suxamethonium apnoea, porphyria (thiopentone precipitates a crisis)

o  Abnormal hepatic or renal function

o  Muscle disease

o  Previous jaundice following anaesthesia

o  Allergy to anaesthetic or related drugs

o  Disorders of blood or coagulation

·        On MAOIs or cholinesterase inhibitors


·         Also investigate Hb, U+E, CXR, ECG and Respiratory function if indicated


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