Evaluation of some drug combinations for intravenous regional analgesia in rabbits

Abstract

The present study was designed to evaluate and compare the clinical effects of intravenous regional analgesia (IVRA) with lidocaine, alone, or in a combination of lidocaine and various opioids. The study was conducted on forty-eight New Zealand white rabbit. Rabbits were randomly divided into four groups. Group L received 0.5% lidocaine (3 mg/kg) without epinephrine, group LM received meperidine plus 0.5% lidocaine (15 mg + 1.5 mg/kg), group LT received tramadol plus 0.5% lidocaine (15 mg + 1.5 mg/kg), group LF received fentanil plus 0.5% lidocaine (15 μg + 1.5 mg/kg). Time to onset of analgesia, duration of analgesia and motor blockade were recorded. In addition, some cardiovascular and respiratory variables were measured. Degree of sedation before and after tourniquet release was evaluated. Onset of analgesia with opioid combinations was significantly shorter than that with lidocaine alone. Duration of motor blockade and analgesia were significantly longer in group LM than in the other groups. In addition, duration of analgesia in group LT was also significantly longer than in group L. Although respiratory rate of the groups L, LM and LF reduced following tourniquet release, sedation scores of these groups was raised. However, respiratory rate was significantly lower in group LM than in group L. Sedation scores in groups L, LM and LF were also significantly higher than in group LT. Heart rate gradually decreased after the tourniquet release in the groups L, LT and LF. Heart rate of group LM following tourniquet release was also significantly higher than those in other groups. In conclusion, a mixture of meperidine and lidocaine solution would appear to be a better choice for IVRA than lidocaine-fentanil and tramadol combination, also for its few side effects.