Study of three different doses of epidural neostigmine coadministered withlidocaine for postoperative analgesia

Background Intrathecal neostigmine produces analgesia In volunteers and pat ients. However, the use of epidural neostigmine has not been investigated. The purpose of the current study was to define the analgesic effectiveness of epidural neostigmine coadministered with lidocaine and side effects in p atients after minor orthopedic procedures. Methods: After Institutional Review Board approval and informed consent, 48 patients (n = 12) undergoing knee surgery were randomly allocated to one o f four groups and studied in a prospective way. After 0.05-0.1 mg/kg intrav enous midazolam premedication, patients were randomized to receive 20 rug I ntrathecal bupivacaine plus epidural lidocaine (85 mg) with saline (control group): 1 mu g/kg( epidural neostigmine (1 mu g group); 2 mu g/kg epidural neostigmine (2 pg group); or 4 mu g/kg epidural neostigmine (4 mu g group) . The concept of the visual analog scale, which consisted of a 10-cm line w ith 0 equaling "no pain at all" and 10 equaling "the worst possible pain" w as Introduced Postoperatively, pain was assessed using the visual analog sc ale, and Intramuscular 75 mg diclofenac was available at patient request. Results: Groups were demographically the same and did not differ in intraop erative characteristics (blood pressure, heart rate, ephedrine consumption oxyhemoglobin saturation, sensory loss before start of surgery, or duration of sensory motor block). The visual analog scale score at first rescue ana lgesic and die incidence of adverse effects were similar among groups CP > 0.05). The time (min a SD) to first rescue analgesic was as follows: contro l group: 205 a 48; I-Gig group: 529 +/- 314; 2-mu g group: 504 +/- 284; 4 m u g group: 547 +/- 263 (P < 0.05). The analgesic consumption (number of int ramuscular diclofenac injections [mean, 25th-75th percentile) in 25 h was a s follows: control group: 3 [3 or ii]; 1-mu g group: 1 [1 or 2]; 2-mu g gro up: 2 [1 or 2]; 4-mu g Bn,up: 2 [1-;3] (P < 0.05). The 24-h pain visual ana log scale score Ccm a SD) that represents the overall Impression for the I: last 24 h uns as follows: control, group: 5 a 1.6; 1-mu g group: 1.6 +/- 1. 8: 2-mu g group: l. 1.4 +/- 1.6; 4-Crg group: 2.2 +/- 1.9 (P < 0,005). The incidence of adverse effects was similar among groups (P > 0.05), Conclusions: Epidural neostigmine (1, 2, or 4 mu g/kg) in lidocaine produce d a dose-independent analgesic effect (similar to 8 h) compared to the cont rol group (similar to 3.5 h), and a reduction in postoperative rescue analg esic consumption without increasing the incidence of adverse effects.