[Effects of intravenous naloxone on the secondary effects and analgesia after epidural injection of fentanyl].

On demand intravenous naloxone reverses respiratory depression following epidural morphine but does not have any effect on analgesia. This study aimed to assess the action of a preventive naloxone infusion on the side-effects and analgesia induced by epidural fentanyl. Sixteen patients were studied. Three had isolated uncomplicated flail chest. The thirteen others had undergone thoracotomy, and were included in the protocol at least 6 h after extubation. All patients had two epidural injections, they received an intravenous infusion of either 10 micrograms.kg-1.h-1 naloxone after a 400 micrograms bolus (group F + N) or 5% dextrose (group F), which was randomly allocated. In group F, but not in group F + N PaCO2 increased from the 15th min to the 4th, and sedation occurred from the 15th min to the 6th h. A significant and similar pain relief was noted in both groups. Duration of analgesia was not statistically different in the two groups. This preventive action of intravenous naloxone on the supraspinal adverse effects of epidural fentanyl was not accompanied by a reduction in analgesia. This could lead to widespread use of this analgesic technique.