Dose-Response Study of Intrathecal Morphine Versus Intrathecal Neostigmine, Their Combination, or Placebo for Postoperative Analgesia in Patients Undergoing Anterior and Posterior Vaginoplasty

Abstract

This study was designed to examine postoperative analgesia with intrathecal neostigmine in a randomized, blinded trial with morphine as the active control in patients undergoing anterior and posterior vaginoplasty.A secondary aim was to provide preliminary data on the interaction between these two drugs. The incidence of adverse effects was also assessed. Forty-eight patients were divided into eight groups (50 micro gram, 100 micro gram, and 200 micro gram morphine [M]; saline; 50 micro gram, 100 micro gram, and 200 micro gram neostigmine [N]; and 50 micro gram morphine + 50 micro gram neostigmine). Anesthesia was provided with a balanced technique. All patients stayed 24 h in the recovery room where adequacy of postoperative analgesia and side effects were assessed. Increasing doses of intrathecal morphine (50 micro gram, 100 micro gram, and 200 micro gram) and intrathecal neostigmine (50 micro gram, 100 micro gram, and 200 micro gram) showed a dose-dependent pattern of analgesia (P < 0.001). The M50 + N50 combination resulted in a better analgesic effect with fewer side effects than M50, N50, and control groups. These preliminary data suggest that spinal neostigmine produces analgesia for vaginoplasty surgery similar in duration to spinal morphine and that the combination of morphine and neostigmine may allow a reduction in the dose of each component for postoperative analgesia. (Anesth Analg 1996;82:1182-7)