Premedication
"That which cannot be easily treated had better be prevented." Alfred Lee.
Medication should be individualized to the patient and risk factors.
1. Anxiolytic
Building a rapport with the patient is the best anxiolytic.
Drugs needed specially for cardiac, hypertensive, asthmatic patients.
Caution in extremes of age, renal and hepatic failure. c.g. diazepam or midazolam. Use lorazepam in the elderly.
2. Amnesic
To avoid 'awareness' specially with minimal anaesthesia e.g. midazolam, lorazepam in trauma, cardio pulmonary by pass surgery etc.
3. Anti sialogogue
To reduce secretions in oral surgery, in the mentally handicapped e.g. atropine, glycopyrrolate
4. Autonomic suppression
Vagolytic (atropine) for dilatations, squint and retinal surgery, children Beta blocker for hypertension, IHD, and hypotensive anaesthesia
5. Analgesic
Paracetamol, NSAIDs, tramadol (unless regional analgesia is planned) EMLA patch (1 hr before) or ametop (20 min before)
6. Antiemetic/Prokinetics
Patient : migraine, motion sickness, obesity, young, females, cyclic with menstruation, prolonged fasting, full stomach
Surgical : gynaecological, ENT, eye, laparoscopy, chemotherapy
Anaesthetic: opiates, N, O, thiopentone, ketamine, gas in stomach Give metoclopramide (for most), promethazine (for opiates), ondansetron and dexamethasone for chemotherapy or if resistant.
7. Acid aspiration prophylaxis
Risk of aspiration, acidity (pregnancy, obesity, heartbum, etc) Give ranitidine, metoclopramide, sodium citrate
8. Anti thrombotic : DVT prophylaxis (see page 1.7)
9. Adrenal cover : steroids (see page 8.19)
10. Antibiotic prophylaxis : heart disease, contaminated surgery, prosthetic implants, immunocompromised. (see page 10.14)
11. Anti disease medication : antihypertensives, bronchodilators etc
Pre-operative Modification of Patient's
Drug Therapy
Aim To obtain best optimisation and stability peri-operatively
To ensure reversibility and quick control, change to drugs with shorter half lives To minimize withdrawal, side effects, and drug interactions To modify drug, dose, route and anaesthetic for best outcome
• Oestrogens (DVT risk) for 4 weeks pre and post surgery
(may continue if ambulatory, minor operations, or low dose) ACE inhibitors and angiotensin receptor inhibitors for 24 hours
• Clopidogrel for 7 days
Change • MAOI : pargyline, phenelzine, tranylcypromine, isocarboxacid Danger with pethidine, ephedrine (hypertension, fits, coma)
• Tri -cyclic anti-depressants block reuptake, cause tachyarrhythmias Danger with ephedrine, halothane, ketamine, and pancuronium
• Potassium sparing diuretics cause hyperkalaemia Danger with muscle injury, bums, renal disease, suxamethonium • Warfarin : stop for 3 days, convert to heparin, if needed
• Aspirin : stop for 7 days, but weigh risk / benefit (TURP high risk)
Continue. Beta blockers, Ca blockers, clonidine, to avoid hypertensive crises
• Anti-anginal therapy to prevent ischaemia
Bronchodilators to prevent bronchospasm
• Steroids to prevent adrenal crisis
• Anti epileptic therapy to avoid seizures
Caution Sympathomimetics cause hypertension, tachycardia, arrhythmias.
• Enzyme inhibitors (cimetidine) may prolong action of opiates, benzodiazepines, theophylline, LA, beta blockers, anti-coagulants.
• Enzyme inducers: Na valproate, barbiturates, phenytoin, carbamazepine
• Suxamethonium prolonged with ecothiopate, neostigmine, chemotherapy. • Non-depolarizers prolonged with aminoglycosides, Ca antagonists, Mg,
immunosuppressives, anti-arrhythmic drugs.
Amiodarone may cause 3rd degree heart block. • Diuretics causes hypovolaemia and hypokalaemia.
Lithium causes hypokalaemia. Digoxin toxicity with hypokalaemia • Anti-epileptics may have drug interactions due to enzyme induction.