Ondansetron attenuates the decrease in blood pressure due to spinal anesthesia in the elderly: a double blind, placebo-controlled study.

BACKGROUND: Ondansetron was effectively used to prevent spinal anesthesia-induced hypotension in the general population and women anesthetised for cesarean section. The aim of this study was to test the hypothesis that blocking type 3 serotonin receptors with intravenous ondansetron administration reduces hypotension and bradycardia induced by spinal anesthesia in elderly patients. METHODS: Fifty-three patients participated in the study with 26 in the ondansetron group (received 8 mg intravenous ondansetron) and 27 in the placebo group (received 0.9% NaCl solution). The heart rate and arterial blood pressure were measured every 5 minutes after spinal anaesthesia, which was performed with 2.5 to 3 mL of 0.5% hyperbaric bupivacaine solution. RESULTS: Decreases in both the heart rate and mean systolic, as well as diastolic, arterial pressure compared to the baseline values were noted in both groups. The minimum diastolic and mean blood pressure values obtained over a 20-minute observation period were significantly higher in the ondansetron group. There were no significant differences in the systolic blood pressure and heart rate values between the groups. CONCLUSION: Administration of intravenous ondansetron prior to spinal anesthesia in geriatric patients attenuates the drop in the diastolic and mean arterial pressure without substantially affecting the systolic blood pressure.

Influence of promethazine on cardiac repolarisation: a double-blind, midazolam-controlled study.

Drugs used in anaesthesia may provoke torsadogenic changes in cardiac repolarisation. The aim of this study was to assess the effect of promethazine on the parameters of ventricular repolarisation: QTc interval and transmural dispersion of repolarisation. Forty patients were randomly allocated to receive promethazine (25 mg) or midazolam (2.5 mg). Changes in the ECG and arterial blood pressure were recorded. Correction of QT interval was calculated using Bazett's formula and Fridericia's correction; transmural dispersion of repolarisation was determined as T(peak)-T(end) time. Significant prolongation of QT interval, corrected with both formulae, was detected in patients receiving promethazine, while no change in the QTc value was observed in the midazolam group. There were no significant differences in T(peak)-T(end) time either between or within the groups. In conclusion, promethazine induces significant QTc prolongation but the lack of influence on transmural dispersion of repolarisation makes the risk of its torsadogenic action very low.