Effect of three different doses of hyperbaric bupivacaine 0.5 % in unilateral spinal anesthesia on cardiovascular parameters : a nexfin monitor study

Background One of the major drawbacks in spinal anesthesia is the hemodynamic and cardiovascular affection. One of the methods used to decrease these side effects is unilateral spinal. Many concentrations of local anesthetics are tried to achieve the best results with the least disturbances. The ccNexfin monitor is a noninvasive monitor used to measure cardiac performance. Materials and methods This prospective randomized study was carried out on 111 patients scheduled for orthopedic or vascular procedures involving one lower limb; patients were divided into three groups, each including 37 patients. The three groups received unilateral spinal anesthesia using the same technique, but with different doses of bupivacaine 0.5% (7.5, 10, and 12.5mg for groups I, II, and III, respectively). Hemodynamic changes were measured in the three groups and also the cardiovascular changes using the noninvasive ccNexfin monitor. In addition, sensory level and motor power were recorded in each group at different time intervals. Data were analyzed statistically. Results The mean arterial pressure and heart rate showed no clinical decrease at all testing times with a dose of 7.5 mg; yet, there were decreases in both parameters when using the higher doses and the decrease was maximal with 12.5 mg. In terms of the cardiac performance, cardiac output, cardiac index, and stroke volume showed no decrease at all testing times with a 7.5mg dose, whereas the higher doses showed a decrease at these parameters that was maximal when using a dose of 12.5 mg. Also, there was a decrease in the systemic vascular resistance with time in the three groups and the decrease was greater in group III. In terms of the sensory level, the dependent limb had a sensory level of midthoracic in most of the patients in both group I and II and upper thoracic in group III. For the nondependent limb, unilateral selectivity was maintained in group I (5.4% with no sensory level), but in groups II and III, unilateral selectivity was lost. For the motor power when using the 7.5mg dose, unilateral selectivity was maintained (89.2% of the nondependent side had a modified Bromage scale of zero) whereas with increasing dose, the selectivity was lost in a dose-dependent manner. Conclusion Unilateral spinal anesthesia using a dose of 7.5mg hyperbaric bupivacaine 0.5% exerts less effects on hemodynamic and cardiac performance with better selectivity than using the higher doses of 10 and 12.5mg in orthopedic and vascula