Prilocaine reduces injection pain caused by propofol

Abstract

Propofol, which is commonly used for outpatient anaesthesia, may evoke pain during infusion. Forty-eight patients (ASA I-II) undergoing elective uterine dilatation and curettage received randomly in a standardised fashion: A: Propofol mixed with prilocaine; B: Propofol and lidocaine; C: Propofol with prilocaine + lidocaine (equal amounts) or D: Propofol and saline. The final ratio of propofol: local anaesthetic/saline was 9: 1 in all mixtures. Pain on injection was significantly decreased in the three groups receiving propofol and local anaesthetic(s) compared to the one given propofol and saline. Propofol is required in greater amounts when mixed with lidocaine than when mixed with saline. A binding between the algesic part of the propofol molecule and the local anaesthetic agent may explain these findings. Another twenty-two comparable patients were given 30 mg of ketorolac or an equal volume of saline intramuscularly 45 60 minutes prior to propofol. Ketorolac given before propofol did not reduce pain on injection. This indicates that inhibition of the cyclooxygenase pathway of arachidonic acid metabolism does not play a major role in the reduction of this pain.