Ultrasound Versus Palpation for Determining Spinal Puncture Level in Cesarean Section (USG-SPINE)

Comparison of Ultrasound and Palpation for Determining the Level of Entry in Spinal Anesthesia for Cesarean Section: Technical Success, Level Accuracy and Maternal Hemodynamic Response - A Randomized Controlled Trial

This study compares two methods of identifying the correct intervertebral level before performing spinal anesthesia in women undergoing elective cesarean delivery.

In current practice, anesthesiologists locate the puncture site by feeling anatomical landmarks on the lower back (palpation of Tuffier's line). Ultrasound imaging offers an alternative in which the spine is scanned and the intended level is marked on the skin before the needle is inserted. It is not yet clear whether this additional step improves the success of the procedure or affects the mother's blood pressure and heart rate after the block.

Sixty pregnant women scheduled for elective cesarean section will be randomly assigned to one of two groups. In one group, the puncture level will be determined by preprocedural ultrasound marking; in the other, by conventional landmark palpation. All other aspects of anesthetic care, including drug doses, will be identical in both groups.

The main outcome is the proportion of patients in whom the subarachnoid space is entered successfully at the first attempt with a single skin puncture, producing a block adequate for surgery. Additional outcomes include the number of needle passes, procedure duration, changes in maternal blood pressure and heart rate, vasopressor requirement, sensory block level, and complications such as headache or back pain within 24 hours after surgery.

Study Overview

• Status: Not yet recruiting
• Conditions: Cesarean Section (MeSH: D002585); Anesthesia, Spinal (MeSH: D000775); Hypotension (MeSH: D007022)
• Intervention / Treatment: Procedure: Preprocedural ultrasound level identification; Procedure: Landmark palpation level identification

Detailed Description

Detailed Description - teknik açıklama, 32.000 karakter sınırı var. Brief Summary'de olmayan yöntem detayları buraya girer. Metin:

Background and Rationale

Spinal anesthesia is the technique of choice for elective cesarean delivery. The intended puncture site is conventionally identified by palpating Tuffier's line, an imaginary line joining the iliac crests, which is assumed to cross the L4 vertebral body or the L4-L5 interspace. Anatomical studies and imaging data have shown that this assumption is unreliable, particularly in pregnancy, where lumbar lordosis, soft tissue changes and altered pelvic tilt shift the landmark cephalad in a substantial proportion of women. Levels selected by palpation are therefore frequently one or more interspaces higher than intended.

Preprocedural ultrasound allows direct visualization of the sacrum and the lumbar interlaminar spaces, and the selected level can be marked on the skin before needle insertion. Whether the improvement in level accuracy translates into clinically meaningful differences in technical success and maternal hemodynamic response has not been established consistently in the obstetric population.

Study Design

This is a prospective, randomized, controlled, parallel-group, single-center trial conducted at the Department of Anesthesiology and Reanimation, Kahramanmaraş Sütçü İmam University Health Practice and Research Hospital.

Sixty ASA II-III women aged 18-45 years with singleton pregnancies scheduled for elective cesarean section under spinal anesthesia will be enrolled after written informed consent. Randomization will be performed using computer-generated block randomization with an allocation ratio of 1:1 (30 per group).

Interventions

Ultrasound group: Before the procedure, the lumbar spine will be scanned with a low-frequency curvilinear probe in the patient's sitting position. The sacrum will be identified in the paramedian sagittal oblique plane and interspaces counted cephalad. The target interspace will be marked on the skin, and the transverse midline plane will be used to confirm the midline. Spinal anesthesia will then be performed at the marked level.

Palpation group: The puncture level will be determined by palpation of Tuffier's line according to standard clinical practice, without ultrasound assistance.

In both groups, spinal anesthesia will be performed with the patient seated, using a midline approach and a pencil-point spinal needle. Hyperbaric bupivacaine with fentanyl will be administered as a single dose, calculated according to the Harten table based on maternal height. A maximum of three puncture attempts is permitted; if unsuccessful, the case will be managed at the discretion of the attending anesthesiologist and recorded as a failure of the allocated technique.

After completion of the block, and without any modification of clinical management, ultrasonography will be used in both groups purely for observational purposes to verify the intervertebral level at which the dural puncture was performed. This exploratory assessment allows quantification of level accuracy in both arms.

Measurements

Baseline maternal characteristics (age, height, weight, body mass index, gestational age, ASA class, parity) will be recorded. Procedure-related variables include the number of skin punctures, number of needle redirections, and procedure duration measured from needle-skin contact to visualization of cerebrospinal fluid.

Non-invasive blood pressure and heart rate will be recorded at baseline and every 3 minutes thereafter until delivery and subsequently until the end of surgery. Hypotension is defined as a mean arterial pressure below 65 mmHg or a decrease of 20% or more from the baseline value, and will be treated with intravenous ephedrine according to institutional protocol; total ephedrine dose will be recorded.

Sensory block level will be assessed bilaterally at 10 and 15 minutes after intrathecal injection. Intraoperative nausea and vomiting, paresthesia during needle insertion, bloody tap, incomplete block, requirement for supplemental analgesia, and conversion to general anesthesia will be documented. Patients will be assessed at 24 hours postoperatively for post-dural puncture headache, back pain, and satisfaction using a visual analogue scale.

Sample Size

The sample size was calculated using G*Power 3.1, based on success rates reported by Li et al. (2019). For the comparison of proportions between two independent groups using Fisher's exact test, with a significance level of 0.05, power of 0.80, and an effect size of h = 0.79, a minimum of 30 participants per group is required, giving a total of 60 participants.

Statistical Analysis

Distribution of continuous variables will be assessed with the Shapiro-Wilk test and visual methods. Normally distributed data will be presented as mean ± standard deviation and non-normally distributed data as median with interquartile range. Between-group comparisons will use the independent samples t-test or Mann-Whitney U test for continuous variables, and the chi-square or Fisher's exact test for categorical variables. Changes in hemodynamic parameters over time will be analyzed using repeated measures analysis (mixed model or repeated measures ANOVA, according to assumption checks). Statistical significance will be accepted at p < 0.05. Analyses will primarily follow the intention-to-treat principle, and missing data will be reported.

• Study Type: Interventional
• Enrollment (Estimated): 66
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Feyza Çalışır, MD; Phone Number: +905056492875; Email: fbolcal@hotmail.com
• Study Contact Backup: Name: Betül Bağrıaçık, MD; Email: fbolcal@hotmail.com

Study Locations

• Turkey (Türkiye)
  • Onikişubat
    • Kahramanmaraş, Onikişubat, Turkey (Türkiye), 46040
      • Kahramanmaraş Sütçü İmam University Health Practice and Research Hospital
      • Contact: Feyza Çalışır; Phone Number: 05056492875; Email: fbolcal@hotmail.com
      • Contact: Feyza Çalışır, MD; Email: fbolcal@hotmail.com
      • Principal Investigator: Feyza Çalışır, MD
      • Sub-Investigator: Betül Bağrıaçık, MD
      • Sub-Investigator: Selim Karaküçük, MD
    • Kahramanmaraş, Onikişubat, Turkey (Türkiye), 46100
      • Kahramanmaraş Sütçü İmam University Health Practice and Research Hospital
      • Sub-Investigator: Betül Bağrıaçık, MD
      • Sub-Investigator: Selim Karaküçük, MD
      • Contact: Feyza Çalışır, MD; Phone Number: 05056492875; Email: fbolcal@hotmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Scheduled for elective cesarean section under spinal anesthesia
• Age 18 to 45 years
• ASA physical status II or III
• Singleton pregnancy
• No contraindication to spinal anesthesia
• Normotensive
• Provides written informed consent

Exclusion Criteria:

• Emergency cesarean section
• Morbid obesity (body mass index 40 kg/m² or higher)
• History of lumbar spine surgery
• Severe spinal deformity
• Local infection at the puncture site
• Coagulopathy or ongoing anticoagulant therapy
• Anatomical abnormality expected to require multiple puncture attempts

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Ultrasound Group; Preprocedural ultrasound scanning of the lumbar spine in the sitting position with a low-frequency curvilinear probe. The sacrum is identified in the paramedian sagittal oblique plane, interspaces are counted cephalad, and the target interspace is marked on the skin. Spinal anesthesia is then performed at the marked level.	Procedure: Preprocedural ultrasound level identification; Ultrasound-assisted identification and skin marking of the target intervertebral level before spinal needle insertion. Spinal anesthesia is performed with the patient seated, using a midline approach and a pencil-point spinal needle, with hyperbaric bupivacaine and fentanyl dosed according to the Harten table based on maternal height. A maximum of three puncture attempts is permitted.
Active Comparator: Palpation Group; Puncture level determined by palpation of Tuffier's line according to standard clinical practice, without ultrasound assistance. Spinal anesthesia is performed at the palpated level.	Procedure: Landmark palpation level identification; Identification of the target intervertebral level by palpation of Tuffier's line. Spinal anesthesia is performed with the patient seated, using a midline approach and a pencil-point spinal needle, with hyperbaric bupivacaine and fentanyl dosed according to the Harten table based on maternal height. A maximum of three puncture attempts is permitted.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
First-attempt success rate	Successful dural puncture (CSF flow) with a single skin puncture at the selected level, with adequate surgical block and no need for supplemental analgesia or GA.	During spinal procedure (up to 30 minutes)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of skin punctures and needle redirections	Number of skin punctures and number of needle redirections required to achieve dural puncture	During the spinal procedure, up to 30 minutes
Procedure duration	Time from needle-skin contact to visualization of cerebrospinal fluid	During the spinal procedure, up to 30 minutes
Incidence of hypotension	Mean arterial pressure below 65 mmHg or a decrease of 20% or more from baseline	From intrathecal injection to end of surgery, up to 90 minutes
Total ephedrine dose		From intrathecal injection to end of surgery, up to 90 minutes
Sensory block level	Assessed bilaterally by pinprick	10 and 15 minutes after intrathecal injection
Incidence of nausea and vomiting		Intraoperative period, up to 90 minutes
Incidence of paresthesia during needle insertion		During the spinal procedure, up to 30 minutes
Incidence of bloody tap		During the spinal procedure, up to 30 minutes
Incidence of incomplete block requiring supplemental analgesia or conversion to general anesthesia		Intraoperative period, up to 90 minutes
Incidence of post-dural puncture headache		Within 24 hours after surgery

Collaborators and Investigators

• Sponsor: Kahramanmaras Sutcu Imam University
• Investigators: Principal Investigator: Feyza Çalışır, Kahramanmaras Sutcu Imam University

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): September 1, 2027
• Study Completion (Estimated): September 1, 2027

Study Registration Dates

• First Submitted: July 24, 2026
• First Submitted That Met QC Criteria: August 24, 2026
• First Posted (Actual): August 27, 2026

Study Record Updates

• Last Update Posted (Actual): August 27, 2026
• Last Update Submitted That Met QC Criteria: August 24, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: obstetric anesthesia; neuraxial anesthesia; Tuffier's line; first-attempt success; preprocedural ultrasound; landmark palpation
• Additional Relevant MeSH Terms: Vascular Diseases; Cardiovascular Diseases; Hypotension
• Other Study ID Numbers: 2026/01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be made publicly available. De-identified data supporting the published results may be provided by the corresponding author upon reasonable request, subject to approval by the institutional ethics committee and in accordance with national data protection legislation.

Drug and device information, study documents

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