Study of Different Concentrations of Epidural Bupivacaine for the Effects on Vasodilatation and Sensory Block

Study Overview
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Brief Summary
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This study aims to compare human subjects receiving epidural bupivacaine local anesthetic at different doses and concentrations and to assess the effect on vasodilatation (sympathectomy), sensory and motor block. The hypothesis is that the drug concentration is more important than drug dose in the determination of the extent and intensity of differential sympathetic, sensory and motor block following epidural local anesthetic.

Detailed Description
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There is controversy regarding the factors that determine the extent and intensity of epidural drug action. Most studies have focused on the inter-related triad of dose, concentration and volume. We compare three groups: group A: 10ml of 0.5% bupivacaine; group B: 10ml of 0.25% bupivacaine and group C: 40ml of 0.0625% bupivacaine. When comparing these groups, groups A & B have the same volume of epidural drug, and groups B & C have the same total dose. In particular this study compares different methods of assessing the sympathetic block (causing vasodilatation). These methods include skin temperature changes, hemodynamic changes and photoplethysmography.

Official Title
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Sympathectomy-Mediated Vasodilatation and Differential Sensory Block After Epidural Bupivacaine: a Randomized Concentration Ranging Study

Conditions
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Intraoperative Complications

Intervention / Treatment
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* Drug: Epidural bupivacaine (dose/concentration/volume ranging)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients scheduled for extracorporeal shock wave lithotripsy (ESWL) under epidural anesthesia between March to September 1999 Exclusion Criteria: graded as ASA 3 or higher, below 18 or above 70 years of age, if they had peripheral vascular disease, baseline neurological deficit, or had any other contraindication for regional anesthesia.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 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: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Intervention/Treatment |
| --- |
|Drug: Epidural bupivacaine (dose/concentration/volume ranging)|nan|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Index of sympathectomy: photoplethysmography derived amplitude-baseline ratio from foot and hand; data measured at time 0, 5, 10 and 20 min following epidural; data expressed as % change from baseline and as area under time effect curve. |  |  | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 1. Other indices of sympathectomy: |  |  | 
| a. Photoplethysmography derived baseline change (ln (Blepi/Blo)); |  |  | 
| b. Photoplethysmography derived time lag between pulse reaching hand and foot; |  |  | 
| c. Blood pressure (mean, systolic, diastolic); |  |  | 
| d. Skin temperature changes (finger and toe temperature change from baseline, toe-thigh and finger-arm temperature gradients). |  |  | 
| 2. Sensory level (pinprick, touch, cold) |  |  | 
| 3. Motor block (Bromage scale) |  |  | 
| All assessments made at 0, 5, 10 and 20 minutes after epidural drug administration. |  |  | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Anesthesia, Epidural, Pharmacology, Dose-Response Relationship, Drug, Sympathectomy, Photoplethysmography