An interventional study of Ondansetron and Placebo (0.9% sodium chloride) in Hypotension (MeSH: D007022) and Bradycardia, sponsored by Aydin Adnan Menderes University. Completed at 1 site in Turkey (Türkiye). Open to female participants aged 18 Years to 45 Years. Per ClinicalTrials.gov, last updated 2026-10-23.
Sponsored by Aydin Adnan Menderes University · Not applicable, Interventional, and Prevention
Spinal anesthesia is the preferred technique for elective cesarean section, but it is frequently complicated by maternal hypotension and bradycardia. Activation of serotonin type 3 (5-hydroxytryptamine type 3; 5-HT3) receptors on cardiac vagal afferent nerves has been proposed as one mechanism of the Bezold-Jarisch reflex, which may contribute to sudden bradycardia and vasodilation after spinal anesthesia. Ondansetron is a selective 5-HT3 receptor antagonist.
This randomized, double-blind, placebo-controlled trial evaluated whether a single intravenous (IV) dose of ondansetron 4 mg given 5 minutes before spinal anesthesia reduces maternal hypotension, bradycardia and the need for rescue medications (ephedrine and atropine) in women undergoing elective cesarean section. Hemodynamic variables and the pulse oximetry-derived perfusion index (PI) and pleth variability index (PVI) were recorded at predefined time points, including during a passive leg raising (PLR) maneuver before spinal anesthesia.
Design and setting: This was a single-center, prospective, randomized, double-blind, placebo-controlled, parallel-group trial conducted at Aydin Adnan Menderes University Hospital, Aydin, Turkiye, between 16 April 2021 and 16 April 2022. The study was approved by the institutional clinical research ethics committee on 15 April 2021 (protocol no. 2021/02). Written informed consent was obtained from all participants before randomization.
Randomization and blinding: Participants were allocated in a 1:1 ratio using a computer-generated randomization sequence and sequentially numbered, sealed, opaque envelopes. An anesthesiologist not involved in patient care or data collection prepared the study drug (ondansetron 4 mg or 0.9% sodium chloride) in identical 2-milliliter (mL) syringes. Patients, the anesthesiologists performing spinal anesthesia and deciding on rescue treatment, and the investigators recording outcomes were blinded to group allocation.
Procedure: Baseline measurements were obtained with the torso elevated to 45 degrees and the legs horizontal. Passive leg raising (PLR) was then performed (torso horizontal, legs raised to 45 degrees), and measurements were repeated after at least 1 minute. The study drug was administered intravenously (IV), and 5 minutes later spinal anesthesia was performed in the sitting position at the third-fourth lumbar (L3-L4) interspace with a 25-gauge Quincke needle using 10 milligrams (mg) of hyperbaric bupivacaine. Left uterine displacement was applied after the patient was positioned supine. A sensory block level of at least the tenth thoracic dermatome (T10) was required before surgery. Lactated Ringer's solution (planned total volume 2500 mL) was infused from spinal anesthesia until the end of surgery. Oxygen was given at 4 liters per minute via face mask.
Monitoring: Non-invasive blood pressure was measured every 3-4 minutes after spinal anesthesia. Systolic blood pressure (SBP), heart rate (HR), perfusion index (PI) and pleth variability index (PVI) were recorded at baseline, during PLR, at 1, 5, 8, 12 and 15 minutes after spinal anesthesia, and after delivery. PI and PVI were measured with a Masimo Root monitor using a sensor placed on the right thumb.
Definitions and rescue treatment: Hypotension was defined as a decrease in SBP to less than 80% of the baseline value and was treated with 5 mg IV ephedrine boluses. Bradycardia was defined in the protocol as an HR below 45 beats per minute and was treated with 0.5 mg IV atropine; atropine could also be given at the clinical discretion of the blinded attending anesthesiologist.
Sample size: Based on a previously published randomized trial of ondansetron 4 mg in parturients undergoing cesarean section, in which vasopressor requirement was 42.3% with saline and 7.7% with ondansetron, 29 patients per group were required to detect this difference with a two-sided alpha of 0.05 and 80% power (with continuity correction). Allowing for approximately 10% dropout, 33 patients per group (66 in total) were randomized.
1,021 studies on the registry are indexed under Hypotension; 172 are open to participants now.
This study's enrollment of 66 is below the median of 80 across 686 interventional studies indexed under Hypotension.
Browse Hypotension studies →Aydin Adnan Menderes University is the lead sponsor of 240 studies on the registry; 52 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Participants received 2 milliliters (mL) of 0.9% sodium chloride intravenously (IV) 5 minutes before spinal anesthesia.
Drug: Placebo (0.9% sodium chloride)
Participants received ondansetron 4 milligrams (mg) in 2 milliliters (mL) intravenously (IV) 5 minutes before spinal anesthesia.
Drug: Ondansetron
A single intravenous (IV) dose of ondansetron 4 milligrams (mg) in 2 milliliters (mL), administered 5 minutes before spinal anesthesia.
A single intravenous (IV) dose of 2 milliliters (mL) of 0.9% sodium chloride, administered 5 minutes before spinal anesthesia in a syringe identical in appearance to the active drug.
Incidence of maternal hypotension
Number of participants with hypotension, defined as a decrease in systolic blood pressure to less than 80% of the baseline value.
Time frame: From spinal anaesthesia to 15 minutes after spinal anaesthesia
Atropine requirement
Number of participants who received intravenous atropine 0.5 mg.
Time frame: From spinal anaesthesia to the end of surgery
Incidence of bradycardia
Number of participants with heart rate below 45 beats/min.
Time frame: From spinal anaesthesia to 15 minutes after spinal anaesthesia
Total ephedrine dose
Cumulative dose of intravenous ephedrine (mg) administered to treat hypotension.
Time frame: From spinal anaesthesia to the end of surgery
Systolic blood pressure
Systolic blood pressure (mmHg) measured non-invasively.
Time frame: Baseline, during passive leg raising, 1, 5, 8, 12 and 15 minutes after spinal anaesthesia, and after delivery
Heart rate
Heart rate (beats/min).
Time frame: Baseline, during passive leg raising, 1, 5, 8, 12 and 15 minutes after spinal anaesthesia, and after delivery
Perfusion index (PI)
Perfusion index measured with a Masimo Root monitor using a sensor on the right thumb.
Time frame: Baseline, during passive leg raising, 1, 5, 8, 12 and 15 minutes after spinal anaesthesia, and after delivery
Pleth variability index (PVI)
Pleth variability index measured with a Masimo Root monitor using a sensor on the right thumb.
Time frame: Baseline, during passive leg raising, 1, 5, 8, 12 and 15 minutes after spinal anaesthesia, and after delivery
Ability of PLR-induced changes in PI and PVI to predict post-spinal hypotension
Area under the receiver operating characteristic curve (AUC) of the change in PI and PVI from baseline to passive leg raising for discriminating participants who developed hypotension.
Time frame: Baseline and during passive leg raising (before spinal anaesthesia)
Apgar score at 1 and 5 minutes after delivery
Neonatal condition assessed with the Apgar score at 1 and 5 minutes after delivery. The Apgar score evaluates five components (heart rate, respiratory effort, muscle tone, reflex irritability and skin color), each scored from 0 to 2. The total score ranges from a minimum of 0 to a maximum of 10, with higher scores indicating a better outcome.
Time frame: 1 and 5 minutes after delivery
Plan to share: Yes — De-identified individual participant data underlying the results reported in the published article (baseline characteristics, hemodynamic measurements, rescue medication use and neonatal Apgar scores) will be shared.
Supporting information: Study protocol, Statistical analysis plan
Time frame: Beginning after publication of the main results and available for 5 years.
Access criteria: Data will be available to qualified researchers upon reasonable request to the principal investigator, for a methodologically sound proposal, after approval by the institutional ethics committee and signing of a data use agreement.
Ran from Apr 2021 to primary completion in Apr 2022, 12 months.
Of 237 non-industry interventional studies with no phase under Hypotension, half reached primary completion within 12 months of starting (the median), counting those still running; a quarter within 6 and three quarters within 25. This study's 12 months is close to that.
Counting every sponsor, half of 248 studies reached it within 12 months; a quarter within 6 and three quarters within 25.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is completed, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Studies of the drug tested here: Ondansetron
Aydin Adnan Menderes University →