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Anesth Essays Res. 2019 Apr-Jun;13(2):340-346. doi: 10.4103/aer.AER_22_19.

Effect of Intravenous Ondansetron on Spinal Anesthesia-Induced Hypotension and Bradycardia: A Randomized Controlled Double-Blinded Study.

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Department of Anaesthesiology, GSL Medical College, Rajahmundry, Andhra Pradesh, India.
Department of Anaesthesiology, MS Ramaiah Medical College, Bengaluru, Karnataka, India.
Department of Anaesthesiology, Rangadore Memorial Hospital, Bengaluru, Karnataka, India.



Spinal anesthesia is a safe anesthetic technique commonly practiced. However, it is associated with hypotension (33%), bradycardia (13%), and shivering which are induced by hypovolemia, sympathetic blockade, and Bezold-Jarisch reflex through intracardiac serotonin (5HT3) receptors and vagus nerve.


To study the effect of intravenous (i.v.) ondansetron on hypotension and bradycardia induced by spinal anesthesia.

Setting and Design:

This was a randomized controlled double-blinded study done in a tertiary care teaching hospital.


Of 140 patients, 70 in Group A received 2 mL of i.v. ondansetron 4 mg and 70 in the Group B received 2 mL of i.v. normal saline. 3 mL of 0.5% hyperbaric bupivacaine was injected intrathecally. Measurements of blood pressure and heart rate (HR) were taken every 3 min for 30 min after spinal anesthesia was performed. Mean arterial pressure (MAP) drop more than 20% was considered as incidence of hypotension and ephedrine 6 mg i.v. was given. HR drop >20% was regarded as bradycardia and atropine 0.5 mg i.v. was given.

Statistical Tests:

Quantitative data were analyzed using ANOVA test and qualitative data were analyzed using Chi-square test.


Both groups are comparable in demographic data. Four (5.7%) patients in Group B and no patients in Group A had incidence of bradycardia and atropine requirement (P = 0.120). There was no statistically significant difference in systolic blood pressure, diastolic blood pressure, and MAP. 19 (27%) patients in Group A and 33 (47.1%) in Group B required ephedrine with P = 0.029. 12 (17.1%) in Group B and no patients in Group A had shivering with P = 0.0001.


Our study indicates that prophylactic use of ondansetron before spinal anesthesia significantly reduces the requirement of ephedrine and shivering.


Bezold–Jarisch reflex; ondansetron; spinal anesthesia

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