Inhibition of postoperative pain by continuous low-dose intravenous infusion of lidocaine.

Intravenous lidocaine has been reported previously to inhibit postoperative pain when given either as single injections or as short infusions in amounts usually causing adverse reactions. To determine the efficacy of a continuous low-dose (2 mg/kg) intravenous infusion of lidocaine, postoperative pain (visual analogue pain scale) and the requirements for postoperative analgesics were measured in a double-blind randomized trial in 20 patients after cholecystectomy. Lidocaine infusion was started 30 min before the operation and continued for 24 hr after surgery (n = 10). Saline was infused in a comparable group of ten patients. The lidocaine-treated patients had significantly lower pain scores during the first day after surgery (P less than 0.001) and required significantly less meperidine during the first (P less than 0.02) and second postoperative days (P less than 0.01). No adverse reactions to lidocaine were observed. Whole blood levels of lidocaine ranged between 1 and 2 micrograms/ml. The results suggest that low-dose continuous infusions of lidocaine decrease the severity of postoperative pain and are devoid of side effects.