Propofol causes pain and clinically far less relevant, hypotension on injection. Both magnesium (Mg) and ketamine are an antagonist of the N-methyl-d-aspartate (NMDA) receptor ion channel. In view of the analgesic activity of Mg and ketamine, we tested the hypothesis that i.v. magnesium sulphate would be equally effective with ketamine in reducing pain due to propofol injection.

Two hundred ASA I–III adults undergoing elective ophthalmic surgery were randomly assigned into four groups of 50 each. Group M received magnesium sulphate 2.48 mmol, Group K received ketamine 10 mg, Group L received lidocaine 1% (30 mg) and Group C received normal saline, all in a volume of 5 mL followed by 5 mL of 1% propofol 30 s later. Pain was assessed on a four-point scale: 0 = no pain, 1 = mild pain, 2 = moderate pain, and 3 = severe pain at the time of pretreatment and propofol injection.

Eighty-eight percent of patients in the control group had pain during i.v. propofol as compared to 34%, 28%, and 18% in the magnesium, ketamine, and lidocaine groups respectively (P < 0.01). Incidence of mild, moderate, and severe pain was significantly lower in Groups K, L, and M compared with Group C (P < 0.05). Ketamine, lidocaine, and magnesium pretreatments were equally effective in attenuating pain during the propofol i.v. injection (P > 0.05).

Intravenous magnesium, ketamine, and lidocaine pretreatment are equally effective in attenuating propofol-induced pain.

Source: Source: doi:10.1016/j.acpain.2008.01.001