Prophylactic Ondansetron and Maternal Hemodynamics During Spinal Anesthesia for Elective Cesarean Section

Hypotension (MeSH: D007022), Bradycardia

ondansetron, Serotonin 5-HT3 receptor antagonist, Bezold-Jarisch reflex, Spinal anesthesia, Cesarean section, Spinal anesthesia-induced hypotension, Perfusion index, Pleth variability index, Passive leg raising

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.

No related papers found yet.

Turkey (Türkiye)