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

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

2. 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.

3. 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.

4. 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

5. 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 anaesthesiaans maximize fitness. • Check anaesthesia/analgesia type with anesthesia.

6. Preoperative assessment and premedication

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

8. 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

9. Corticosteroids – extra cover might be needed • Diuretics – might have hypokalaemia • Insulin – careful monitoring of plasma glucose • Antibiotics: tetracycline and neomycin may ↑ neuromuscular blockade.

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

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

12. 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)?

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

14. Per-op investigation of elective patients

15. 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

16. 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

17. 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

18. American Society of Anesthesiologists (ASA) classification

19. 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)

20. 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

21. Pre-medication • 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

22. 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.

23. 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.