Aishah Awatif Haziq Pre-operative evaluation and preparation (prior to procedure under general anesthesia)

Introduction Anaesthesia = absence of all sensation Analgesia = absence of pain General anaesthesia = a state where all sensation is lost and the patient is rendered unconscious by drugs. GA should be performed by qualified anasthetists in a hospital setting with access to appropriate medical support.

Assessment of risk Patient should be made as fit as possible for the operation. The anticipated benefit should outweigh the anesthetic and surgical risks involved. Overall mortality rate ≈ 1 in 100 000 Surgical mortality ≈ 1 in 1000

Factors contribute to this mortality: Poor preoperative assessment Inadequate supervision and monitoring in the intraoperative period Inadequate postoperative care

Preoperative assessment and premedication

History Past medical history: Asthma Diabetes Tuberculosis Seizures Chronic organ dysfunction HIV infection Drug allergy DVT Post-operative nausea and vomiting

Drug history Drug interactions Anticoagulant might be contraindicated to spinal, epidural or other regional techniques Anticonvulsants might increase the requirements for anasthetic agents, enflurane should be avoided as it might precipitate seizures Beta-blockers – negative ionotropic effect – hypotension Corticosteroids – extra cover might be needed Diuretics – might have hypokalaemia Insulin – careful monitoring of plasma glucose

Social history Ceasing smoking 12h before surgery can improve the oxygen carrying capacity of the blood. Excessive alcohol – hepatic and cardiac damage

Family history Hereditary traits: Haemophilia Porphyria Cholinesterase abnormalities – prolongation of muscle relaxants such as suxamethonium

Physical examination Full physical examination Especially the upper airway including the teeth and extent of mouth opening and flexibility of the neck – to assess the ease of tracheal tubing

Per-op investigation of elective patients Indications of preoperative investigations Full blood count anaemia females post menarche cardiopulmonary disease possible haematological pathology, e.g. haemoglobinopathies likelihood of significant intraoperative blood loss history of anticoagulants chronic diseases such as rheumatoid disease

Urea and electrolyte concentrations Clotting screen liver disease anticoagulant drugs or a history of bleeding or bruising kidney disease major surgery Urea and electrolyte concentrations major surgery >40 years diabetes mellitis digoxin, diuretics, corticosteroids, lithium history of diarrhoea and vomiting

Liver function tests: these will be carried out when there ECG is any suspicion of liver disease ECG >40 years asymptomatic male or >50 years asymptomatic female history of myocardial infarction or other heart or vascular disease <40 years with risk factors e.g. hyperlipidaemia, diabetes mellitus, smoking, obesity, hypertension and cardiac medication Chest radiography breathlessness on mild exertion suspected malignancy, tuberculosis or chest infection thoracic surgery

Pre-op therapy Pt with respiratory disease – physiotherapy or bronchodilator therapy Infective endocarditis – prophylactic antibiotic Hypertension – adjustment of drug therapy to obtain optimal control (diastolic pressure below 110 mmHg)

Postponement of surgery Pt with acute upper resp tract infection Cardiac/endocrine diseases that are not yet under optimal control Elective surgery should not be undertaken unless: Pt has fasted for 6h for solid food, Infant formula or other milk 4h for breast milk 2h for clear non-particulate and non-carbonated fluids

Premedication benzodiazepines – anxiolysis, anterograde amnesia Anticholinergic drug – reduce excessive secretions in the airway Antiemetic Antihistamine Metoclopramide - enhance gastric emptying Sodium citrate, H2 blockers, proton pump inhibitor – reduce gastric acidity

Preparation for anesthesia