Premedication

• Analgesia: Pre-emptive analgesia aims to dampen the pain pathways before the signals starts to arrive. It is not often used, and effects are hard to determine as few studies are in agreement and there are many variables.
• Antacid: For reflux either ranitidine 150mg PO or omeprazole 40mg PO/IV the night before and then 2h pre-op. Ranitidine reduces both gastric pH and volume. High risk of aspiration in: Emergency surgery, pregnancy, DM, hiatus hernia.
• Anti-emesis
• Antibiotics: Depends on surgery e.g. cefuroxime + metronidazole for colorectal or biliary surgery.
• Anti-autonomic: B-blockers can be used to reduce risk of perioperative ischaemia.
• Steroids: Minor operations 25-50mg hydrocortisone IV at induction, major operations 50mg at induction then repeat 3 times 8 hourly before restarting oral. Ditto if adrenal insufficieny or adrenal surgery, or >10mg prednisolone/day over last 3m.
• Bronchodilators: E.g. salbutamol nebuliser.
• Anxiolytics and Amnesia: Amnesia may add to the unpleasantness of the experience, though it can be useful in those not wanting to know, and children.
  • The most common agents used are benzodiazepines. E.g. lorazepam 2mp PO, temazepam 10-30mg PO, diazepam 5mg PO. Some anaesthetists still use morphine 10mg IM (SE dysphoria) or atropine 0.6mg IM.
  • Children: Midazolam 0.5mg/kg (tastes bitter so often put in Calpol).
    Local anaesthetic creams for children: Tetracaine 4% applied 45min before inserting IVI.
    The presence of a parent at induction is more powerful than any premedication in reducing anxiety.

The patient should be aware of what will happen, where she will wake and how she will feel. Premedication aims to to allay anxiety and contribute to a smooth induction of anaesthesia by decreasing secretions (much less important than when ether was used), promoting amnesia and analgesia, and decreasing vagal reflexes.

Timing: 2h pre-op for oral drugs, 1h pre-op if IM.