Body Mass Index and Spinal Anesthesia in Urological Surgery

The Effect of Body Mass Index on Vasopressor Use, Block Dynamics, and Hemodynamic Responses in Urological Surgery Cases Undergoing Spinal Anesthesia: Prospective Observational Study

This single-center prospective observational study investigates the effect of body mass index (BMI) on intraoperative vasopressor requirements and spinal block characteristics in adult patients undergoing urological surgery under spinal anesthesia. Participants are classified into two cohorts according to BMI (<27.5 kg/m² and ≥27.5 kg/m²).Patient enrollment for this prospective observational study started before trial registration; therefore, this record represents a retrospective registration.

Study Overview

• Status: Completed
• Conditions: Body Mass Index; Urologic Surgical Procedures; Vasopressor Therapy

Detailed Description

This is a single-center prospective observational study conducted at a tertiary care hospital between May 2022 and December 2025. The study aims to evaluate the relationship between body mass index (BMI) and intraoperative ephedrine requirements, sensory and motor block characteristics, and hemodynamic responses in adult patients undergoing elective urologic surgery in the lithotomy position under spinal anesthesia. All patients received a standardized intrathecal dose of 3 mL 0.5% hyperbaric bupivacaine, and intraoperative hypotension was treated with intravenous ephedrine according to a predefined protocol. Patient enrollment for this prospective observational study began before registration of the study; therefore, this record represents a retrospective registration. Ethics approval was obtained from the institutional ethics committee prior to patient recruitment, and written informed consent was obtained from all participants.

• Study Type: Observational
• Enrollment (Actual): 120

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Adıyaman Province
    • Merkez, Adıyaman Province, Turkey (Türkiye), 02100
      • Adıyaman University Faculty of Medicine Anesthesiology and Reanimation

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Adult patients (≥18 years) with ASA physical status I-II scheduled for elective urological surgery in the lithotomy position under spinal anesthesia at a tertiary care hospital. All participants had a BMI ≥18.5 kg/m² and were classified into two groups according to BMI (Group L: BMI <27.5 kg/m², Group H: BMI ≥27.5 kg/m²). Patients with contraindications to spinal anesthesia, extreme height (<150 cm or >190 cm), or who declined participation were excluded.

Description

Inclusion Criteria:

• Age 18 years or older
• American Society of Anesthesiologists (ASA) physical status I-II
• Scheduled for elective urologic surgery under spinal anesthesia

Exclusion Criteria:

• Refusal to participate or lack of informed consent
• Contraindications to spinal anesthesia
• Height <150 cm or >190 cm
• BMI <18.5 kg/m²

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
BMI <27.5 kg/m² (Group L); Adult patients undergoing elective urologic surgery under spinal anesthesia with a body mass index (BMI) <27.5 kg/m²
BMI ≥27.5 kg/m² (Group H); Adult patients undergoing elective urologic surgery under spinal anesthesia with a body mass index (BMI) ≥27.5 kg/m².

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intraoperative ephedrine consumption (mg)	Cumulative intravenous ephedrine dose administered to treat hypotension (systolic arterial pressure <90 mmHg or >30% decrease from baseline) from the time of spinal anesthesia induction until the end of the surgical procedure.	From spinal anesthesia induction until completion of surgery.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximum sensory block level	Highest thoracic dermatome level reached after intrathecal injection of 3 mL 0.5% hyperbaric bupivacaine, assessed by pinprick testing every 2 minutes.	During intraoperative monitoring
Time to reach maximum sensory block (minutes)	Time in minutes from the intrathecal injection of hyperbaric bupivacaine until the maximum sensory block level is achieved.	From intrathecal injection to maximum sensory level
Time to two-segment regression of sensory block	Time in minutes from the maximum sensory block level until regression of sensory block by two thoracic dermatomes.	From maximum sensory block to two-dermatome regression
Time to reach Bromage score 3	Time in minutes from the intrathecal injection until development of complete motor block in the lower extremities (Bromage score 3)	From intrathecal injection to complete motor block
Motor block recovery time(minutes)	Time in minutes from the intrathecal injection until the earliest detectable return of motor function in the lower extremities.	From intrathecal injection to earliest detectable return of motor activity
Hemodynamic parameters	Noninvasive systolic and diastolic arterial pressure and heart rate measured at baseline (before spinal anesthesia) and then at 5-minute intervals throughout the surgical procedure.	Baseline and every 5 minutes during surgery.,

Collaborators and Investigators

• Sponsor: Adiyaman University

Study record dates

Study Major Dates

• Study Start (Actual): May 1, 2022
• Primary Completion (Actual): December 1, 2025
• Study Completion (Actual): December 1, 2025

Study Registration Dates

• First Submitted: June 12, 2026
• First Submitted That Met QC Criteria: June 16, 2026
• First Posted (Actual): June 17, 2026

Study Record Updates

• Last Update Posted (Actual): June 17, 2026
• Last Update Submitted That Met QC Criteria: June 16, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Body Mass Index; Ephedrine; Hemodynamic Response; Sensory Block
• Other Study ID Numbers: ADYU-AR-FT-03

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No