Our hypothesis is that the bupivacaine dose determined according to the thoracolumbar vertebral body length (VBL) is more effective in achieving a lower hypotension rate during spinal anesthesia for cesarean delivery than the dose usually adjusted based on height and weight. The VBL measurements were determined from the midpoint of C7 to the tuffier line L4 spinous process.

Method: Patients ranging in height from 150 to 170 were randomly assigned to either Group 1 (0.2 mg of 0.5% hyperbaric bupivacaine per cm VBL or Group 2 (height-adjusted dose of 0.5% hyperbaric bupivacaine based on a minimum dose of 0.065 mg/cm according to height) or Group 3 (height-adjusted dose of 0.5% hyperbaric bupivacaine based on a minimum height-adjusted dose of 0.065 mg/cm).

The study followed a parallel study strategy. Patients provided informed permission before the procedure. The study was randomly assigned and blinded. The study was conducted from April 2025 to December 2025. 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. Each patient was evaluated for vital parameters and possible complications at 3-minute intervals before and after the spinal anesthesia application, treated if necessary, and recorded. The study was concluded at the end of the cesarean section.

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. We inserted two 20-gauge intravenous cannulas and administered an IV-balanced solution using these routes. The patients' age, height, weight, ASA class, and VBL (C7-L4 Tuffier line cm) were recorded. The Tuffier's line (TL), which is made by drawing a horizontal line across the tops of the iliac crests, is the most common anatomical landmark right now. It has been shown to match up with the L4-L5 interspace or the L4 spinous process.

After skin infiltration with 2% lidocaine, a 25-gauge short-bevel Quincke spinal needle was placed at the L3-4 vertebral interspace with the patient in a sitting position. After aspiration of cerebrospinal fluid, the following anesthetic solutions were delivered over 5 seconds. Randomization was used to divide the patients into three groups. The trial was double-blind, with the patient and assessor unconscious of their group allocation. Only the practitioner delivering the spinal anesthesia was aware of the group allocation. Systolic, diastolic, and mean arterial blood pressure and heart rate were documented at baseline and assessed at 3-minute intervals, commencing 3 minutes post-spinal injection and persisting until the initiation of surgical procedures, after which measurements were conducted at 3-minute intervals.

Patients in Group VBL (Vertebral Body Length) received 0.2 mg x VBL cm of 0.5% hyperbaric bupivacaine. In contrast, Group FD (fixed dose) received a 0.5% hyperbaric bupivacaine volume based on a dose calculated according to the patient's height of 0.065 mg/cm. Group AD (adjusted dosage) got intrathecal heavy bupivacaine (0.5%) tailored to the patient's height and weight. A dosage was derived using Harten's dose chart formulated for Caucasian parturients

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