Effects of Ondansetron Timing During Spinal Anesthesia for Urologic Surgery

Condition(s) studied

Investigational drug(s) / intervention(s)

Ondansetron 8 mg: Ondansetron 8 mg will be administered intravenously according to the assigned study arm. In the early ondansetron arm, the drug will be administered approximately 10 minutes before completion of the intrathecal injection. In the late ondansetron arm, the drug will be administered approximately 5 minutes after completion of the intrathecal injection.

0.9 % sodium chloride: Placebo will be administered intravenously in the same volume and appearance as the active study drug according to the blinded study protocol.

Study summary

This study will evaluate whether the timing of intravenous ondansetron administration affects cerebral oxygenation and hemodynamic stability in older adults undergoing endoscopic urologic surgery under spinal anesthesia.

Participants aged 65 years or older will be randomly assigned to one of three groups: ondansetron administered before spinal anesthesia, ondansetron administered after spinal anesthesia, or placebo. Ondansetron will be administered intravenously at a dose of 8 mg.

Cerebral oxygenation will be assessed using bilateral frontal near-infrared spectroscopy (NIRS). Regional cerebral oxygen saturation (rSO₂) will be recorded before spinal anesthesia and at 5-minute intervals during the first 60 minutes after spinal anesthesia.

The study will also evaluate blood pressure, heart rate, vasopressor requirements, bradycardia, postoperative nausea and vomiting, post-spinal headache, and postoperative delirium.

The aim is to determine whether the timing of ondansetron administration influences cerebral oxygenation and hemodynamic stability after spinal anesthesia.

Eligibility

Primary outcome measure(s)

• Bilateral Frontal Regional Cerebral Oxygen Saturation (rSO₂) — Before spinal anesthesia (baseline) and at 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 minutes after spinal anesthesia
  Regional cerebral oxygen saturation (rSO₂, %) will be measured bilaterally over the frontal cortex using near-infrared spectroscopy. Left and right rSO₂ values will be recorded at each prespecified assessment time point.

Trial sites (1)

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