Predicting Spinal Hypotension in Cesarean Section (prediction)

March 30, 2026 updated by: Kudret Dogru, TC Erciyes University

The Value of Waist Circumference, Body Mass Index, and Modified Shock Index in Predicting Spinal Anesthesia-Induced Hypotension During Cesarean Section: A Prospective Observational Study

This prospective observational study investigates the predictive value of anthropometric and hemodynamic indices for spinal anesthesia-induced hypotension (SAIH) during cesarean section. While spinal anesthesia is preferred for its rapid onset, SAIH remains a frequent complication risking maternal and fetal safety. The study enrolled parturients at Erciyes University, excluding those with hypertension or extreme weight/height. Preoperative measurements included BMI, waist circumference (WC), body roundness index (BRI), and modified shock index (MSI). Following standardized spinal anesthesia with hyperbaric bupivacaine (Harten's dosage), hemodynamic parameters and sensory block levels were monitored. This research aims to determine whether BRI and WC offer superior predictive utility compared with conventional markers such as BMI and MSI to enhance individualized risk assessment in obstetric anesthesia.

Study Overview

Status

Recruiting

Conditions

Detailed Description

Spinal anesthesia is the preferred anesthetic technique for cesarean section due to its rapid onset, reliability, and minimal neonatal drug exposure. However, spinal anesthesia-induced hypotension (SAIH) remains the most common and clinically significant complication, with an incidence ranging between 10% and 80% of parturients. The resulting maternal hypotension can lead to symptoms such as nausea, vomiting, and dizziness. At the same time, severe or sustained decreases in blood pressure may compromise uteroplacental perfusion, causing fetal acidosis and distress. Therefore, early prediction and prevention of hypotension are paramount to ensure maternal and neonatal safety.

Several hemodynamic and anthropometric factors have been investigated as potential predictors of SAIH, including baseline blood pressure, heart rate, and indices reflecting intravascular volume or autonomic tone. Among these, the modified shock index (MSI), calculated as the ratio of heart rate to mean arterial pressure, has been proposed as a noninvasive marker of hemodynamic stability and cardiovascular reserve. Likewise, body mass index (BMI), waist circumference (WC), and the body roundness index (BRI) have been associated with alterations in central blood volume, vascular compliance, and sympathetic responsiveness, which may influence susceptibility to post-spinal hypotension.

Pregnancy induces profound physiological changes, including decreased systemic vascular resistance and increased circulating blood volume, which alter cardiovascular responses to sympathetic blockade. These adaptations may interact with individual body composition and baseline hemodynamic parameters, modifying the risk of hypotension. Despite these associations, the predictive utility of anthropometric indices, such as BRI and WC, alongside conventional measures like BMI and MSI, has not been clearly established in obstetric anesthesia.

Symphyseal fundal height (SFH) and AC measurements indirectly indicate compression of the inferior vena cava (IVC). AC and VCL have previously been found to be highly predictive of block level in operations of non-pregnant patients performed under SA with isobaric bupivacaine.

Therefore, this prospective observational study was designed to evaluate the predictive value of waist circumference, body roundness index, body mass index, and modified shock index in identifying parturients at risk for spinal anesthesia-induced hypotension during cesarean delivery. By determining reliable preoperative indicators, this study aims to contribute to individualized risk assessment and the development of preventive strategies in obstetric anesthesia practice.

The study followed a parallel study strategy. Erciyes University's ethical committee approved the study on 2025/82. Patients provided informed consent before the procedure. Patients with pre-existing or pregnancy-induced hypertension, cardiovascular or cerebrovascular disease, contraindications to spinal anesthesia, weighing < 50 kg or > 110 kg, and heights higher than 170 cm or shorter than 150 cm were eliminated. Informed written consent was acquired from all patients participating in the trial.

There was no premeditation among the patients. The patient had standard monitoring, including non-invasive blood pressure, ECG, and pulse oximetry, with recorded baseline blood pressure and heart rate measurements. Two 20-gauge intravenous cannulas will be inserted, and an IV-balanced solution will be administered using these routes. The patient's age, height, weight, and ASA class were recorded. Height (cm), body weight (kg), waist circumference (WC; cm), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) were measured by assistants using a hemodynamic monitor and tape measure. Body mass index (BMI) was computed as weight (kg) divided by height squared (m²). The girth of the midpoint between the lowest point of the rib and the upper edge of the iliac crest was calculated as the waist circumference (WC). The Body Roundness Index (BRI) was calculated using the formula BRI=364.2-365.5×(√1-((WC/(2π))²/(0.5×Height)²). The modified shock index (MSI) was calculated as follows: MSI (heart rate/MAP). After skin infiltration with lidocaine 2%, a 25-gauge Whitacre spinal cannula, 25 G x 3 1/2" (0.5 x 90 mm), with an introducer spinal needle, was placed at the L3-4 vertebral interspace with the patient in a sitting position. After cerebrospinal fluid aspiration, the following anesthetic solutions were delivered over 5 seconds. Patients received a 0.5% hyperbaric bupivacaine volume, calculated based on their height and weight, at a dose of 0.5%. A dosage was derived using Harten's dose chart formulated for Caucasian parturients.

All patients received supplemental oxygen. Bradycardia (defined as a heart rate < 60 beats/min) was treated with 0.5 mg of intravenous atropine. Hypotension, defined as a reduction in baseline systolic blood pressure of >20%, a systolic blood pressure <100 mmHg, or a mean arterial pressure <65 mmHg, was treated with 10 mg of intravenous ephedrine. In the event of dizziness, nausea, or vomiting, the patient was administered 5 mg of ephedrine. To prevent postoperative nausea and vomiting, 4 mg of intravenous ondansetron was administered. Additionally, 1.5 g of intravenous cefuroxime was given prior to the incision for surgical site infection prophylaxis. A surgical incision was necessary when pinprick sensation was lost bilaterally in the T6 dermatome. If the sensory blockage was inadequate 5 minutes after spinal anesthesia insertion, the assessor placed the patient in a 10-degree head-down tilt. If patients experienced discomfort during the procedure, a 0.5 mg/kg propofol and 0.25 mg/kg ketamine bolus were administered via the venous route. If these efforts proved ineffective, the option of switching to general anesthesia was provided. Following birth, 100 IU carbetocin was administered as a uterotonic by gradual intravenous infusion. Paracetamol IV 1000 mg was administered after the procedure. Postoperative analgesia was constituted by TAP block with 20 ml of 0.25% bupivacaine bilaterally.

The upper sensory level of anesthesia was evaluated by systematically measuring the loss of pinprick sensation at the midclavicular line at 2-minute intervals; additionally, motor block was assessed using the Bromage scale.

Study Type

Observational

Enrollment (Estimated)

321

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 Contact Backup

Study Locations

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

  • Child

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Parturients undergoing cesarean section

Description

Inclusion Criteria:

  1. American Society of Anesthesiologists (ASA) Class II
  2. Having regular antenatal visits
  3. Singleton pregnancy at ≥37 weeks of gestation
  4. Pregnant women aged 18-45 -

Exclusion Criteria:

  1. Those with eclampsia, those with preeclampsia
  2. Undergoing an emergency cesarean section
  3. Those with bleeding diathesis and those receiving anticoagulant therapy
  4. With a history of carotid artery stenosis,
  5. Cardiovascular disease,
  6. Hypertension,
  7. Chronic obstructive pulmonary disease,
  8. Heart rhythm outside of sinus
  9. Patients with a history of cerebrovascular disease
  10. Alcoholism or psychiatric illness
  11. Placenta previa, accreta, and percreta

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

Cohorts and Interventions

Group / Cohort
Spinal Anestezi CS
Spinal Anes Cs

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of Spinal Anesthesia-Induced Hypotension (SAIH)
Time Frame: From the time of spinal bupivacaine administration up to 30 minutes post-administration.
The presence or absence of hypotension (binary variable) will be recorded. The predictive power of the independent variables (BMI, BRI, WC, MSI) for this condition will be evaluated using logistic regression. Nagelkerke's $R^2$ was treated as a component of the analysis procedure, not as a measurement unit.
From the time of spinal bupivacaine administration up to 30 minutes post-administration.

Collaborators and Investigators

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

Sponsor

TC Erciyes University

Investigators

  • Principal Investigator: Kudret Doğru, 1, TC Erciyes 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.

Helpful Links

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 (Actual)

March 16, 2026

Primary Completion (Estimated)

October 20, 2026

Study Completion (Estimated)

November 30, 2026

Study Registration Dates

First Submitted

March 16, 2026

First Submitted That Met QC Criteria

March 25, 2026

First Posted (Actual)

March 30, 2026

Study Record Updates

Last Update Posted (Actual)

March 31, 2026

Last Update Submitted That Met QC Criteria

March 30, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2026/82

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Patient information is considered personal data and its sharing is prohibited due to privacy regulations.

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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