Anaesthetists Handbook - MEDICAL EDUCATION at University ...

Pain management and postoperative care• Management of neuropathic pain• Management of pain in opioid tolerant patients• Management of pain in patients who are too sedated withopioids and yet do not have adequate analgesiaInfusion guidelines:This must be prescribed by an anaesthetist.1. Draw up 20 mL from 10 mg mL -1 strength ketamine solution vialand dilute to 50 ml with 0.9% saline. This gives a 4 mg mL -1solution. (If only 50 mg mL -1 strength available, draw up 4 mLand dilute to 50 mL with saline).2. Usual dosage range: younger patients 1-2 mL h -1 (4 to 8 mg h -1 )up to a maximum of 3 mL h -1 (12 mg h -1 ). Smaller doses may berequired in the elderly. (Suggest using half-strength solutioninstead, in this case, as such small volumes are involved withstandard solution.)3. A small initial intravenous bolus of 10-20 mg should be givenvery slowly by an anaesthetist before commencing the infusion.4. Ketamine infusions may be run in the same line as the PCA aslong as a non-return valve is used.5. Routine observations as per PCA chart.6. Discontinue the ketamine infusion when stopping the PCAmorphine.7. In patients at risk of neuropathic pain or patients who are opioidtolerant the infusion may run for 3 to 5 days.8. At the above recommended doses, ketamine should not causeconfusion, sedation, or other mental state changes, orhypertension. If there are any concerns, contact the acute painteam nurses or the anaesthetist on call.ReferenceP.E. Macintyre, B.L. Ready: Acute pain management, a practicalguide (2 nd Ed), London, W.B. Saunders.Anaesthetists Handbook January 2010 99