Systemic opioids enhance the spread of sensory analgesia produced by intrathecal lidocaine.
The effect of different doses of fentanyl and nalbuphine on the spread of spinal analgesia produced by lidocaine was studied in 68 patients undergoing transurethral resection of the prostate (TURP) under spinal anesthesia. Patients were randomly assigned to six groups: fentanyl A, B, or C (FA, FB, FC) or nalbuphine A, B, or C (NA, NB, NC), which received intravenous (i.v.) 50, 100, or 150 micrograms of fentanyl or 10, 15, or 20 mg of nalbuphine, respectively, 20 min after spinal anesthesia with lidocaine. We tested the level of spinal analgesia with pinprick sensation 20 min after spinal anesthesia and 10 min after the opioid administration, when 0.4 mg of naloxone was administered i.v. The levels of sensory analgesia were reassessed 10 min after naloxone. Ten minutes after fentanyl or nalbuphine, the level of analgesia increased (1.8 +/- 1.7, 3.1 +/- 1.2, and 4.1 +/- 1.5 cm, in the FA, FB, and FC groups and 1.9 +/- 0.9, 2.6 +/- 1.4, and 3.7 +/- 2.2 cm in the NA, NB, and NC groups, respectively). The increases in the level of analgesia differed significantly between the fentanyl groups (F = 8.0939; df = 2.35; P < 0.001), the increase produced by 150 micrograms being significantly higher than produced by 50 micrograms of fentanyl (limits of confidence -4.236809 and -0.4431909; P < 0.01). Naloxone reversed the effect of fentanyl and 10 min after its administration the fentanyl groups did not differ with regard to the level of spinal analgesia.(ABSTRACT TRUNCATED AT 250 WORDS)