A comparison of the effects of hyperbaric and isobaric bupivacaine spinal anesthesia on hemodynamics and heart rate variability.

AIM To compare the effects of hyperbaric and isobaric bupivacaine spinal anesthesia on hemodynamics and heart rate variability (HRV) in nonobstetric surgery. MATERIALS AND METHODS Sixty patients were randomly allocated to 2 groups. Group I (n = 30) received 15 mg (3 mL) of hyperbaric bupivacaine and Group II (n = 30) received 15 mg (3 mL) of isobaric bupivacaine for spinal anesthesia. Hemodynamic parameters were recorded before and after spinal anesthesia over 30 min. Analyses of HRV were performed on the day of surgery, after volume loading, and 20 min after spinal injection. Low frequency (LF) values, high frequency (HF) values, and LF/HF ratios were recorded. The incidences of hypotension and alterations of HRV parameters in both groups were investigated. RESULTS The incidence ofhypotension was 26.6% and 23.3% in Groups I and II, respectively. There were no significant differences in the LF and HF values and LF/HF ratios between groups. In Group I, LF/HF ratios were significantly lower and HF values were significantly higher at 20 min after spinal anesthesia, in comparison to the baseline value (P < 0.05). CONCLUSION Hyperbaric bupivacaine caused a significantly greater decrease in LF/HF ratios and a significantly greater increase in HF values.