Spinal anesthesia with meperidine: will epinephrine prolong its duration?

Meperidine (Demerol) has local anesthetic properties separate from its opioid receptor agonist effect. Unlike morphine, meperidine is structurally similar to local anesthetics. Therefore, it is not surprising that it possesses some characteristics of local anesthetics. If meperidine acts like a local anesthetic, binding to the same receptor sites and inhibiting nerve conduction, then drugs that alter the action and duration of local anesthetics may have a similar effect on it. This double-blinded investigation used low-dose meperidine as the sole intrathecal agent to determine the effect of epinephrine on the duration of sensory blockade. Thirty male ASA physical status I through III patients between the ages of 58-81 years who were scheduled for transurethral resection of the prostate or of bladder tumors were randomly assigned to receive meperidine with or without epinephrine. A continuous spinal technique was utilized, and meperidine 0.5 mg/kg was administered after ascertaining the proper position of the catheter. Fourteen of the patients received epinephrine, and 16 patients did not. There were no statistically significant differences between the two groups in terms of age, height, weight, and ASA physical status. No statistically significant prolongation of the sensory blockade was observed with the addition of epinephrine. There were no statistically significant differences between the two groups with regard to onset time or the incidence of complications. The occurrence of a full motor block in the group that did not receive epinephrine was statistically significant.