Effect of Patient Position on Bupivacaine Dose Requirement and Hemodynamic Stability in Spinal Anesthesia

This study compares different combinations of local anesthetic doses and patient positions during spinal anesthesia for urogenital surgery. Spinal anesthesia is a common and safe technique where medication is injected into the lower back to numb the body during surgery.

The study will test two different doses of bupivacaine (a numbing medication): a lower dose (8 mg) and a standard dose (12 mg). It will also test two different patient positions after the spinal injection: lying flat (neutral position) and lying with the head slightly lower than the feet (Trendelenburg position).

Participants will be randomly assigned to one of four groups:

• Group 1: Lower dose + lying flat
• Group 2: Lower dose + head-down position
• Group 3: Standard dose + lying flat
• Group 4: Standard dose + head-down position

The study will measure how well the anesthesia works, how high the numbness spreads in the body, and how it affects blood pressure and heart rate. The goal is to find the best combination of dose and position that provides good anesthesia while keeping blood pressure stable.

This research may help doctors choose the safest and most effective anesthesia approach for each patient based on their individual needs.

Study Overview

• Status: Not yet recruiting
• Conditions: Spinal Anesthesia; Hemodynamic Changes; Bupivacaine; Patient Positions
• Intervention / Treatment: Drug: Bupivacaine %0.5 (hyperbaric)

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Hasan Duman, M.D.; Phone Number: +905547317716; Email: hasanduman.1991@gmail.com

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Age 18-70 years
• American Society of Anesthesiologists (ASA) physical status classification I-II
• Scheduled for elective urogenital surgery
• Suitable candidate for spinal anesthesia
• Able to read, understand, and provide written informed consent
• Body Mass Index (BMI) less than 35 kg/m²
• Willing to participate in the study

Exclusion Criteria:

• Contraindications to spinal anesthesia (coagulopathy, infection at injection site, patient refusal)
• History of neurological disease
• Spinal deformity or previous spinal surgery
• History of allergic reaction to local anesthetics (amide-type)
• ASA physical status classification III or higher
• Emergency surgery
• Pregnancy
• Psychiatric illness preventing effective communication
• Refusal to participate in the study
• Unable to understand or provide informed consent

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Factorial Assignment
• Masking: Single

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: 8 mg Bupivacaine + Neutral Position; Participants will receive 8 mg of 0.5% hyperbaric bupivacaine via spinal anesthesia at L3-4 or L4-5 interspace in sitting position. Immediately after injection, participants will be positioned supine in neutral (horizontal, 0°) position and maintained in this position throughout the procedure. Standard hemodynamic monitoring and management protocols will be applied.	Drug: Bupivacaine %0.5 (hyperbaric); 8 mg or 12 mg 0.5% hyperbaric bupivacaine administered intrathecally via spinal anesthesia at L3-4 or L4-5 interspace.
Experimental: 8 mg Bupivacaine + 10° Trendelenburg; Participants will receive 8 mg of 0.5% hyperbaric bupivacaine via spinal anesthesia at L3-4 or L4-5 interspace in sitting position. Immediately after injection, participants will be positioned in 10° Trendelenburg position (head-down tilt) and maintained in this position throughout the procedure. Standard hemodynamic monitoring and management protocols will be applied.	Drug: Bupivacaine %0.5 (hyperbaric); 8 mg or 12 mg 0.5% hyperbaric bupivacaine administered intrathecally via spinal anesthesia at L3-4 or L4-5 interspace.
Active Comparator: 12 mg Bupivacaine + Neutral Position; Participants will receive 12 mg of 0.5% hyperbaric bupivacaine via spinal anesthesia at L3-4 or L4-5 interspace in sitting position. Immediately after injection, participants will be positioned supine in neutral (horizontal, 0°) position and maintained in this position throughout the procedure. Standard hemodynamic monitoring and management protocols will be applied.	Drug: Bupivacaine %0.5 (hyperbaric); 8 mg or 12 mg 0.5% hyperbaric bupivacaine administered intrathecally via spinal anesthesia at L3-4 or L4-5 interspace.
Experimental: 12 mg Bupivacaine + 10° Trendelenburg; Participants will receive 12 mg of 0.5% hyperbaric bupivacaine via spinal anesthesia at L3-4 or L4-5 interspace in sitting position. Immediately after injection, participants will be positioned in 10° Trendelenburg position (head-down tilt) and maintained in this position throughout the procedure. Standard hemodynamic monitoring and management protocols will be applied.	Drug: Bupivacaine %0.5 (hyperbaric); 8 mg or 12 mg 0.5% hyperbaric bupivacaine administered intrathecally via spinal anesthesia at L3-4 or L4-5 interspace.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximum Sensory Block Level	The highest dermatomal level of sensory blockade achieved, assessed using pin-prick test (sharp/dull discrimination). Measured as the specific dermatome level (e.g., T4, T6, T8).	From injection to 30 minutes post-spinal anesthesia
Incidence of Hypotension	Proportion of participants experiencing hypotension, defined as mean arterial pressure (MAP) decrease ≥20% from baseline	From spinal injection through end of surgery
Sensory Block Onset Time	Time required to achieve T10 dermatomal sensory block level, measured from completion of intrathecal injection to confirmation of T10 level by pin-prick test.	From spinal injection through end of surgery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Motor Block Degree	Degree of motor blockade assessed using modified Bromage scale (0=no motor block, able to raise extended leg; 1=unable to raise extended leg, able to flex knee; 2=unable to flex knee, able to flex ankle; 3=complete motor block, unable to move).	From spinal injection through end of surgery
Surgical Adequacy	Proportion of participants with adequate anesthesia for surgical procedure completion, assessed as adequate (surgery completed without supplemental analgesia/sedation) or inadequate (requiring supplemental intervention).	Throughout surgery
Incidence of Bradycardia	Proportion of participants experiencing bradycardia, defined as heart rate <50 beats per minute requiring treatment.	From spinal injection through end of surgery
Incidence of Nausea and Vomiting	Proportion of participants experiencing nausea and/or vomiting during the intraoperative and immediate postoperative period.	From spinal injection through end of surgery

Collaborators and Investigators

• Sponsor: University of Health Sciences Balikesir Hospital Eduation and Research

Study record dates

Study Major Dates

• Study Start (Estimated): January 30, 2026
• Primary Completion (Estimated): May 30, 2026
• Study Completion (Estimated): June 30, 2026

Study Registration Dates

• First Submitted: January 21, 2026
• First Submitted That Met QC Criteria: January 21, 2026
• First Posted (Actual): January 29, 2026

Study Record Updates

• Last Update Posted (Actual): January 29, 2026
• Last Update Submitted That Met QC Criteria: January 21, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: Bupivacaine; Spinal Anesthesia; Patient Positioning; hemodynamic changes
• Other Study ID Numbers: hduman

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