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.

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.

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