Effect of Ondansetron on the Incidence of Spinal Anaesthesia-Induced Hypotension in Elderly Patients Undergoing Fracture Hip Surgery

November 3, 2026 updated by: Mina Nagy Shoukrallah, Assiut University

Effect of Ondansetron on the Incidence of Spinal Anaesthesia-Induced Hypotension in Elderly Patients Undergoing Fracture Hip Surgery: A Randomized, Double-Blind, Controlled Clinical Trial

This study aims to compare prophylactic intravenous ondansetron 4 mg versus placebo regarding the incidence of spinal anaesthesia-induced hypotension, defined as mean arterial pressure (MAP) fall >20% from baseline or systolic blood pressure (SBP) <90 mmHg/fall >20% from baseline, in elderly patients undergoing fracture hip surgery. The hypothesis is that a significant difference exists.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Spinal anesthesia is widely used for fracture hip surgery because it provides effective surgical anesthesia while avoiding many physiological effects associated with general anesthesia. However, spinal anesthesia-induced hypotension (SIH), defined as a mean arterial pressure (MAP) decrease >20% from baseline or systolic blood pressure (SBP) <90 mmHg or a >20% decrease from baseline, is one of its most common complications. It primarily results from sympathetic blockade, causing vasodilation, reduced venous return, decreased cardiac output, and subsequent arterial hypotension. This may be particularly significant in elderly patients because of reduced cardiovascular, arterial, and autonomic reserve, together with a higher prevalence of cardiovascular disease and polypharmacy.

A sudden reduction in left-ventricular preload may activate cardiac mechanoreceptors and trigger the Bezold-Jarisch reflex (BJR). Serotonin-sensitive 5-HT3 receptors located on intracardiac vagal nerve endings may enhance vagal activity, contributing to bradycardia defined as heart rate (HR) < 50 beat per minute (bpm) and hypotension.

Ondansetron, a selective 5-HT3 receptor antagonist widely used as an antiemetic, has been investigated to attenuate the BJR and reduce SIH. Several randomized trials and meta-analyses have reported that prophylactic intravenous ondansetron, commonly given at 4-8 mg shortly before spinal injection, reduces post-spinal hypotension, bradycardia, and rescue vasopressor requirements, including in elderly surgical patients. An exploratory analysis suggested a greater preventive effect in patients aged ≥65 years.

However, the elderly subgroup was small and a 8 mg dose was used, leaving uncertainty regarding the optimal dose.

Spinal anesthesia technique The conduct of spinal anesthesia will be standardized across the two groups. On arrival to the operating room, standard ASA monitors including a pulse oximetry, electrocardiography and non-invasive blood pressure will be applied and the patients will be continuously monitored.

Baseline hemodynamics will be recorded at one, three, and five minutes before the studied drug administration, and the average will be taken as a baseline.

After an intravenous (IV) access is secured, all patients will receive an intraoperative infusion of 5-10 ml/kg Ringer's lactate or Normal saline solution per hour.

With the parturient in a sitting position, spinal anaesthesia will be conducted using the midline or paramedian approach after proper antiseptic cleaning and draping in the lumbar vertebral interspace of L3-L4 or a level below using a 25 or 22-gauge Quincke needle. After confirming free flow of cerebrospinal fluid, a 3 mL of hyperbaric bupivacaine 0.5% will be injected intrathecal in both Groups the same dose, Then all patients will be then made to lie supine.

Block-level will be tested every five minutes using a frozen plastic ampule of sterile water along the midclavicular line to check the response to cold, and the highest sensory level obtained will be registered.

Motor level will be assessed every five minutes using the Modified Bromage Scale, where Grade 0 indicates full movement of the hip, knee, and ankle; Grade 1 indicates inability to raise the extended leg while retaining the ability to flex the knee and move the ankle; Grade 2 indicates inability to flex the knee while retaining ankle movement; and Grade 3 indicates complete motor block with inability to move the hip, knee, or ankle. The highest Modified Bromage grade obtained will be recorded.

Surgeons will be allowed to proceed with surgery after attaining a block level of at least up to T10.

Data collection

  1. Patient characteristics including, age, sex, weight, height, and ASA status.

  2. Hemodynamic parameters including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and oxygen saturation (SpO2) will be recorded at the following time points:

    • Before injection of the study drug (baseline);
    • At interval of 0 (baseline) and 5 minutes after the study drug administration and before intrathecal injection;
    • At two-minutes intervals up to 20 minutes after intrathecal injection,
    • Every 5 minutes until end of surgery.
    • Postoperative hemodynamics at 2, 4, 6, 8, 12, 24 hours after surgery.

  3. Bradycardia (HR <50 bpm) will be treated with atropine 0.5 mg. Clinically significant hypotension, defined as MAP fall > 20% from baseline, or systolic blood pressure < 90 mmHg / fall > 20% from baseline, and if developed will be treated with IV ephedrine sulfate boluses of 6 mg as required. Amount of atropine and ephedrine required, sensory level achieved at 15 min of Spinal anaesthesia.

  4. Duration of surgery (minutes), total fluid intake (ml), and length of PACU stay (minutes).

  5. Side effects including hypotension (defined as MAP fall > 20% from baseline, or systolic blood pressure < 90 mmHg / fall > 20% from baseline), hypertension, bradycardia (HR < 50 bpm), tachycardia (HR > 100 bpm), hypoxemia (defined as a SpO2 level of less than 94% with a need for oxygen supplementation), respiratory depression, hallucinations, nystagmus, postoperative nausea and vomiting (PONV), and shivering will be treated and recorded.

The incidence of postoperative nausea and vomiting (PONV) episodes will be assessed in the first 24 h (at 2, 4, 6, 8, 12, 24 hours after surgery).

Patients who will develop shivering will be warmed with heated blankets.

Study Type

Interventional

Enrollment (Estimated)

142

Phase

  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Egypt
      • Asyut, Egypt
        • Assiut University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

65 years and older (Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Age ≥ 65 years
  • American Society of Anesthesiologists (ASA) physical status I, II, III (according to the American Society of Anesthesiologists classification).
  • Scheduled for elective hip fracture surgery under spinal anaesthesia.

Exclusion Criteria:

  • Patient refusal or inability to provide informed consent.
  • Contraindication to spinal/neuraxial anaesthesia (coagulopathy, local infection at injection site, patient refusal, severe spinal deformity).
  • Known hypersensitivity or contraindication to ondansetron (e.g., congenital long-QT syndrome).
  • Baseline cardiac arrhythmia, significant conduction abnormality, or QTc > 450-470 ms on preoperative ECG.
  • Severe cardiovascular disease (decompensated heart failure, recent myocardial infarction, severe valvular disease), ASA IV-V.
  • Baseline bradycardia (heart rate < 50 bpm) or use of a permanent pacemaker.
  • Concurrent use of medications that significantly affect heart rate or QT interval (e.g., class III antiarrhythmics), or of another 5-HT3 antagonist within 24 hours.
  • Emergency surgery, or planned combined spinal-general anaesthesia/conversion anticipated.
  • Pregnancy (not applicable in most cases given the population) and cognitive impairment precluding valid consent or symptom reporting.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Group O (Ondansetron)

Ondansetron 4 mg diluted in 10 mL 0.9% normal saline over 60-90 seconds prior to spinal injection
Drug: Ondansetron

4 mg diluted in 10 mL 0.9% normal saline.
Placebo Comparator: Group P (Placebo)

IV bolus of 10 mL 0.9% normal saline over 60-90 seconds prior to spinal injection
Drug: 0.9% Normal Saline placebo

10 mL IV 0.9% normal saline

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Effect of prophylactic intravenous ondansetron versus Placebo on the incidence of spinal anaesthesia-induced hypotension
Time Frame: From induction of spinal anaesthesia until completion of surgery.

Compare the effect of prophylactic intravenous ondansetron 4 mg versus Placebo on the incidence of spinal anaesthesia-induced hypotension, defined as MAP fall > 20% from baseline, or systolic blood pressure < 90 mmHg / fall > 20% from baseline, in elderly patients undergoing fracture hip surgery under spinal anaesthesia.
From induction of spinal anaesthesia until completion of surgery.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The incidence of severe hypotension
Time Frame: From induction of spinal anaesthesia until completion of surgery.

Severe hypotension, defined as systolic blood pressure (SBP) dropping to <60% of baseline
From induction of spinal anaesthesia until completion of surgery.
The number of episodes of intraoperative hypotension.
Time Frame: From induction of spinal anaesthesia until completion of surgery.

The percentage of people who experience hypotension, defined as MAP fall > 20% from baseline, or systolic blood pressure < 90 mmHg / fall > 20% from baseline, intraoperatively
From induction of spinal anaesthesia until completion of surgery.
The incidence of bradycardia
Time Frame: From induction of spinal anaesthesia until completion of surgery.

The Percentage of people who experience Bradycardia, defined as heart rate (HR) <50 bpm, intraoperatively
From induction of spinal anaesthesia until completion of surgery.
The total rescue vasopressor (ephedrine) and atropine requirements between groups
Time Frame: From induction of spinal anaesthesia until completion of surgery.

Total dose of intraoperative ephedrine or atropine if hypotension or bradycardia occurs
From induction of spinal anaesthesia until completion of surgery.
The incidence of postoperative nausea and vomiting (PONV)
Time Frame: Up to 24 hours postoperatively

PONV was evaluated using the PONV grading scale in the post-anesthesia care unit (PACU) at 2, 4, 6, 8, 12, and 24 hours

PONV will be assessed using a four-grade scale: Grade 0 indicates no PONV; Grade I indicates nausea without vomiting; Grade II indicates nausea with vomiting occurring fewer than three times per day; and Grade III indicates vomiting occurring three or more times per day.
Up to 24 hours postoperatively
The incidence of intraoperative and postoperative shivering between groups
Time Frame: From induction of spinal anaesthesia up to 24 hours postoperatively

Assess the presence of shivering intraoperatively and postoperatively
From induction of spinal anaesthesia up to 24 hours postoperatively
Sensory block characteristics (onset and duration) between groups.
Time Frame: From induction of spinal anaesthesia until completion of surgery.

Block-level will be tested every five minutes using a frozen plastic ampule of sterile water along the midclavicular line to check the response to cold, and the highest sensory level obtained will be recorded Surgeons will be allowed to proceed with surgery after attaining a block level of at least T10.
From induction of spinal anaesthesia until completion of surgery.
Motor block characteristics (onset, Modified Bromage score, and duration) between groups.
Time Frame: From induction of spinal anaesthesia until completion of surgery.

Motor level will be assessed every five minutes using the Modified Bromage Scale, where Grade 0 indicates full movement of the hip, knee, and ankle; Grade 1 indicates inability to raise the extended leg while retaining the ability to flex the knee and move the ankle; Grade 2 indicates inability to flex the knee while retaining ankle movement; and Grade 3 indicates complete motor block with inability to move the hip, knee, or ankle. The highest Modified Bromage grade obtained will be recorded.

Surgeons will be allowed to proceed with surgery after attaining a block level of at least T10.
From induction of spinal anaesthesia until completion of surgery.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Assiut University

Investigators

  • Study Chair: Sherif Sayyed Abdelrahem, PhD, Assiut University
  • Study Director: Abdelrahman Hamdy Mohamed, PhD, Assiut University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

December 1, 2026

Primary Completion (Estimated)

December 1, 2028

Study Completion (Estimated)

March 1, 2029

Study Registration Dates

First Submitted

October 28, 2026

First Submitted That Met QC Criteria

November 3, 2026

First Posted (Actual)

November 4, 2026

Study Record Updates

Last Update Posted (Actual)

November 4, 2026

Last Update Submitted That Met QC Criteria

November 3, 2026

Last Verified

November 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 04-2026-201911

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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