Aishah Awatif Haziq

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  Surgical mortality ≈ 1 in 1000  Factors contribute to this mortality: Poor preoperative assessment Inadequate supervision and monitoring in the intraoperative period Inadequate postoperative care

Aims of Pre-operative evaluation and preparation  To provide diagnostic & prognostic information.  To ensure the patient understands the nature, aim, and expected outcome of surgery.  To relieve anxiety and pain.  Ensure that the right patient gets the right surgery.  Get informed consent.  Assess/balance risks of anaesthesia ans maximize fitness.  Check anaesthesia/analgesia type with anesthesia.

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 Antibiotics: tetracycline and neomycin may ↑ neuromuscular blockade.

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  Assess cardiorespiratory system, exercise tolerance, existing illness, drugs, and allergies.  Is the neck unstable (eg; arthritis complicating intubation?)  Assess past history of; MI, diabetes, asthma, hypertension, rheumatic fever, epilepsy, jaundice.  Assess any specific risk, eg is the patient pregnant? Is the neck/jaw immobile and teeth stable (intubation risk)?

 Has there been previous anaesthesia?  Were there any complications (eg nausea, DVT)?  Is DVT/PE prophylaxis needed?

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

 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 kidney disease diabetes mellitis digoxin, diuretics, corticosteroids, lithium history of diarrhoea and vomiting

 Liver function tests: these will be carried out when there 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

American Society of Anesthesiologists (ASA) classification Class INormally healthy Class IIMild systemic disease Class IIISevere systemic disease that limits activity but is not incapacitating Class IVIncapacitating systemic disease which poses a constant threat to life Class VMoribund: not expected to survive 24h even with operation

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

Pre-medication  benzodiazepines – anxiolysis, anterograde amnesia  Anticholinergic drug – reduce excessive secretions in the airway  Antiemetic  Antihistamine  Metoclopramide - enhance gastric emptying  Sodium citrate, H 2 blockers, proton pump inhibitor – reduce gastric acidity

Preparation for anesthesia  Fast patient. Nil by mouth ≥ 2h pre-op for clear fluid and ≥ 6h for solids  Is there any bowel or skin preparation needed, or prophylactic antibiotic?  Start DVT prophylaxis as indicated, eg: graduated compression stockings + heparin 5000U sc 2h pre-op, then every 8-12h sc for 7d or until ambulant.

 Write up the pre-meds; book any pre-, intra-, or post-operative x-rays or frozen sections. Book post-op physiotherapy.  If needed, catheterize and insert Ryle’s tube before induction. These can reduce organ bulk, making it easier to operate in the abdomen.