Subcutaneous morphine for postoperative analgesia.

ABSTRACT

OBJECTIVE: a. To confirm the efficacy of subcutaneous morphine infusion for postoperative analgesia and compare this effect with three-hourly subcutaneous bolus injections of morphine. b. To evaluate the suitability of a simple micro-infusion set to deliver subcutaneous infusion, as conventional infusion pumps are expensive and not readily available. SETTING: Double blind, prospective controlled clinical trial. PATIENTS 21 patients belonging to the American Society of Anaesthesiologists' (ASA) classes I or II, who underwent major elective abdominal surgery were studied in an intensive care unit. INTERVENTION All patients were given loading doses of morphine intravenously (iv) followed by subcutaneous (sc) infusion in two groups and three-hourly sc bolus injections in the third group. The doses were titrated on an individual basis. The infusion was delivered by a power driven pump in one group and by a microinfusion set in the other. Those with significant pain during this regime were given morphine supplements intravenously. MEASUREMENT Pain scoring was done hourly using a modified verbal rating scale. The percentage of patients who required intravenous supplements in each group was compared to draw statistical conclusions. RESULTS: 1. Subcutaneous infusion provided adequate analgesia in 86% of the patients studied. 2. There was no significant difference between the groups in terms of additional iv supplement requirement. 3. The microinfusion set required frequent readjustments to maintain constant flow. CONCLUSIONS: Intermittent subcutaneous bolus injections of morphine given through an indwelling butterfly needle is a simple, safe, and effective method for postoperative analgesia after major abdominal surgery. Simple infusion sets are not suitable to deliver subcutaneous infusions, and the need for infusion pumps makes the infusion technique unsuitable for routine use in wards.