When combined with
nalbuphine,
local anesthetics show a longer duration of
nerve block without increasing complications. However, no evidence is available concerning the effect of
nalbuphine on the
cardiotoxicity of
local anesthetics. The objective of this work is to investigate whether
nalbuphine pretreatment can increase the lethal dose threshold of
ropivacaine in rats. Anesthetized Sprague Dawley rats were pretreated with different doses of
nalbuphine (0.4, 0.8, 1.5, 3.0, 5.0 mg/kg) or NS (
normal saline, negative control) or 30% LE (
lipid emulsion, positive control) 2 ml/kg/min for 5 min (n = 6). Then 0.5%
ropivacaine was infused at a rate of 2.5 mg/kg/min until
asystole occurs. Time of
arrhythmia, 50% mean arterial pressure- and 50% heart rate-reduction, and
asystole were recorded, and
ropivacaine doses were calculated.
Nalbuphine (0.4-5.0 mg/kg) did not affect
ropivacaine-induced
arrhythmia, 50% mean arterial pressure-reduction and 50% heart rate-reduction, and
asystole in rats compared with NS pre-treatment. The
asystole dose threshold (in milligrams per kilogram) of group LE was higher than that of group NS (NS 28.25(6.32) vs. LE, 41.58(10.65); P = 0.04; 95% confidence interval 0.23 to 26.45), while thresholds of
arrhythmia, 50% mean arterial pressure-reduction, and 50% heart rate-reduction were not affected by LE.
Nalbuphine doses of 0.4-5.0 mg/kg pretreatment did not increase the threshold of
ropivacaine cardiotoxicity compared with NS control; 30% LE increases the lethal dose threshold of
ropivacaine in rats.