Minimum Effective Dose of 0.5% Bupivacaine for Ultrasound-guided Spinal Anesthesia Using Taylor's Approach

Study Overview
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Brief Summary
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This study aims to determine the minimum effective dose of bupivacaine 0.5% in 90% of patients undergoing lower limb surgery with ultrasound-guided spinal anesthesia using Taylor's approach. A biased coin design up-and-down sequential method is applied. The initial dose is 15 mg of bupivacaine 0.5%. After 45 successful spinal anesthesia, the ED90 of bupivacaine 0.5% will be calculated.

Detailed Description
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The minimum effective dose of local anesthetics for spinal anesthesia using Taylor's approach is not known. This study aims to determine the minimum effective dose of bupivacaine 0.5% using a biased coin design up-and-down sequential method. Patients will receive real-time ultrasound guided spinal anesthesia using Taylor's approach. The initial dose is chosen as 15 mg on the basis of clinical experience. Subsequently, if a patient has an inadequate block, the bupivacaine dose is increased by 2 mg in the next subject. If a patient has a successful block, the next subject is randomized to receive either a lower dose (with a decrement of 2 mg), with a probability of b = 0.11, or the same dose, with a probability of 1 - b = 0.89. Forty five successful blocks will be accomplished. MED90 will be calculated by isotonic regression.

Official Title
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Minimum Effective Dose of 0.5% Bupivacaine for Ultrasound-guided Spinal Anesthesia Using Taylor's Approach

Conditions
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Lower Limb Surgery

Intervention / Treatment
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* Procedure: spinal anesthesia


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists physical statusⅠ- Ⅲ Lower limb surgery, expected operation time within 2 hours Exclusion Criteria: Patient refusal American Society of Anesthesiologists physical status IV/V Peripheral neuropathy skin infection at the site of injection allergy to bupivacaine or lidocaine BMI > 35 kg/m2 coagulation disorders

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Deceasing<br>Spinal anesthesia with decreasing dose. Real-time ultrasound-guided spinal anesthesia Using Taylor's approach. | Procedure: spinal anesthesia<br>* Patients will receive real-time ultrasound guided spinal anesthesia using Taylor's approach. Various doses of bupivacaine 0.5% (Bupivacaine hydrochloride injection, Harvest Pharmaceutical CO., LTD., Shanghai, China) will be administered.<br>|
| Active Comparator: Similar<br>Spinal anesthesia with similar dose. Real-time ultrasound-guided spinal anesthesia Using Taylor's approach. | Procedure: spinal anesthesia<br>* Patients will receive real-time ultrasound guided spinal anesthesia using Taylor's approach. Various doses of bupivacaine 0.5% (Bupivacaine hydrochloride injection, Harvest Pharmaceutical CO., LTD., Shanghai, China) will be administered.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The minimum effective dose of bupivacaine in spinal anesthesia using Taylor's approach | The minimum effective dose of bupivacaine in spinal anesthesia using Taylor's approach is based on 45 successful spinal anesthesia performed in patients undergoing lower limb surgery. | up to 6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| the upper level of the sensory block 25 min after bupivacaine injection | the upper level of the sensory block 25 min after bupivacaine injection | 25 min | 
| the incidence of hypotension | the incidence of hypotension | during anethesia and operation | 
| the duration of sensory spinal anaesthesia for the lower extremity | the duration of sensory spinal anaesthesia for the lower extremity | up to 3 days postoperation | 
| postoperative neurological complications | postoperative neurological complications | up to 3 months postoperation |