This randomized controlled study will evaluate whether individualizing the dose of spinal anesthesia according to the ultrasound-derived dural sac cross-sectional area (DSCSA) can improve hemodynamic stability in patients undergoing transurethral resection of the prostate (TURP). Participants aged 40 years or older will be randomly assigned to one of two groups. In the individualized-dose group, the anteroposterior diameter of the dural sac will be measured by ultrasound at the L3-L4 level, and DSCSA will be calculated from this measurement. The dose of intrathecal bupivacaine will then be individualized according to the calculated DSCSA. In the control group, participants will receive a fixed dose of intrathecal bupivacaine. Both groups will also receive intrathecal fentanyl. The main outcome is the incidence of intraoperative hypotension. The study will also evaluate the number of hypotensive episodes, minimum mean arterial pressure, vasopressor and atropine requirements, sensory and motor block characteristics, respiratory monitoring parameters, cerebral oxygenation, and adverse events. The study aims to determine whether a DSCSA-guided dosing strategy can reduce excessive spinal block and improve hemodynamic stability while maintaining effective spinal anesthesia.
This prospective, randomized controlled study compares two routinely used approaches to determining the intrathecal bupivacaine dose for spinal anesthesia in patients undergoing transurethral resection of the prostate (TURP). No new drug, new indication, or experimental treatment will be introduced. Both dosing approaches are currently used in routine clinical practice; the study will prospectively and randomly compare their clinical effects. Participants will be randomly assigned to either a dural sac cross-sectional area (DSCSA)-guided individualized dosing group or a fixed-dose control group. Before spinal anesthesia, the anteroposterior diameter of the dural sac will be measured by ultrasound at the L3-L4 intervertebral level. DSCSA will be calculated using the formula A = π × (D/2)². In the individualized-dose group, a DSCSA of 150 mm² will be used as the reference value corresponding to 10 mg of intrathecal bupivacaine. The bupivacaine dose will be adjusted proportionally according to the participant's calculated DSCSA and limited to a minimum of 6 mg and a maximum of 12.5 mg. Fentanyl 25 micrograms will be added intrathecally. In the fixed-dose group, participants will receive 10 mg (2 mL of 0.5%) intrathecal bupivacaine together with fentanyl 25 micrograms. Spinal anesthesia will be performed at the L3-L4 intervertebral space using a 27-gauge Quincke needle. Standard intraoperative monitoring will be performed according to the study protocol. Sensory and motor block characteristics and hemodynamic variables will be recorded prospectively for comparison between the two dosing strategies.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
SUPPORTIVE_CARE
Masking
DOUBLE
Enrollment
60
The dural sac cross-sectional area (DSCSA) is calculated from the ultrasound-measured anteroposterior dural sac diameter at the L3-L4 level. The intrathecal bupivacaine dose is individualized according to DSCSA.
Hyperbaric bupivacaine is administered intrathecally in both study groups. In the DSCSA-guided group, the dose is individualized according to DSCSA, using 150 mm² as the reference corresponding to 10 mg, with a permitted dose range of 6 to 12.5 mg. In the fixed-dose group, 10 mg (2 mL of 0.5% bupivacaine) is administered.
Fentanyl 25 micrograms is administered intrathecally together with bupivacaine in both study groups.
Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine
Istanbul, Turkey (Türkiye)
Incidence of Intraoperative Hypotension
Intraoperative hypotension is defined as a decrease in mean arterial pressure (MAP) of ≥20% from baseline or an MAP \<65 mmHg. Participants meeting either criterion at least once during surgery will be classified as having intraoperative hypotension. The outcome will be reported as the percentage of participants with intraoperative hypotension.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Number of Intraoperative Hypotension Episodes
Number of intraoperative hypotension episodes recorded for each participant. Hypotension is defined as a decrease in mean arterial pressure (MAP) of ≥20% from baseline or an MAP \<65 mmHg.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Minimum Intraoperative Mean Arterial Pressure
Lowest mean arterial pressure (MAP), measured in mmHg, recorded during the intraoperative period.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Percentage of Participants With a ≥30% Decrease in Mean Arterial Pressure
Percentage of participants experiencing at least one decrease in mean arterial pressure (MAP) of ≥30% from baseline during surgery.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Percentage of Participants Requiring Ephedrine
Percentage of participants receiving at least one intravenous dose of ephedrine for treatment of intraoperative hypotension.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Total Ephedrine Dose
Total intravenous ephedrine dose, measured in milligrams (mg), administered to each participant during surgery.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Percentage of Participants Requiring Atropine
Percentage of participants receiving intravenous atropine for treatment of intraoperative bradycardia.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Total Atropine Dose
Total intravenous atropine dose, measured in milligrams (mg), administered to each participant during surgery.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Maximum Sensory Block Level
Highest cephalad sensory block level achieved after spinal anesthesia, assessed by the pin-prick test and recorded as the corresponding dermatomal level.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Time to Achieve T10 Sensory Block
Time, measured in minutes, from completion of intrathecal injection to achievement of a T10 sensory block, assessed using the pin-prick test.
Time frame: Up to 30 minutes after spinal anesthesia
Time to Two-Dermatome Sensory Regression
Time, measured in minutes, from the maximum sensory block level to regression of the sensory block by two dermatomes, assessed using the pin-prick test.
Time frame: From maximum sensory block until two-dermatome regression, assessed up to 3 hours after spinal anesthesia
Time to Recovery to Modified Bromage Score 0
Time, measured in minutes, from completion of intrathecal injection until recovery to a Modified Bromage score of 0, indicating complete recovery of lower-extremity motor function.
Time frame: From completion of spinal anesthesia until recovery to Modified Bromage score 0, assessed up to 3 hours after spinal anesthesia
Number of Integrated Pulmonary Index ≤4 Episodes
Number of episodes in which the Integrated Pulmonary Index (IPI) is ≤4. The IPI is a composite score ranging from 1 to 10 based on end-tidal carbon dioxide, respiratory rate, oxygen saturation, and pulse rate; lower scores indicate greater respiratory compromise.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
Incidence of Adverse Events
Percentage of participants experiencing at least one adverse event recorded during the intraoperative study period.
Time frame: During surgery (from completion of spinal anesthesia until the end of surgery)
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