Comparison of Two Different Ultrasound Guided Techniques for Saphenous Nerve Block

A Comparison of Two Different Ultrasound-Guided Approaches to the Saphenous Nerve Block - Adductor Canal vs. Distal Trans-sartorial: A Prospective, Randomized, Blinded, Non-Inferiority Trial

Saphenous nerve blocks can be technically challenging. Recently described ultrasound techniques have improved the success rate of saphenous nerve blocks, but randomized controlled trials comparing these techniques are lacking. The investigators compared two common ultrasound guided approach for saphenous nerve block: saphenous nerve block at the adductor canal (ACSNB) vs. block by the distal trans-sartorial (DTSNB) approach.

Study Overview

• Status: Completed
• Conditions: Efficacy of Ultrasound Guided Nerve Block
• Intervention / Treatment: Procedure: Saphenous nerve block

Detailed Description

Patients received either ACSNB or DTSNB in this prospective randomized, blinded, non-inferiority clinical trial. The primary objective was to show the non-inferiority of ACSNB to DTSNB in terms of block success. Secondary outcome measures were time required to perform the block, time to onset of successful block, and the visibility of the nerve using ultrasound.

Sample size calculation: To address the primary objective of the study--to show non-inferiority of the ACSNB to DTSNB in terms of success as defined above- the investigators used the test of non-inferiority of two proportions. DTSNB is the primary technique of doing saphenous nerve block at the investigators' institution. From chart review of the electronic records from 2011 to 2012, the investigators found there was a 3% incidence of rescue blocks among saphenous nerve blocks (19 out of 667 blocks) at their institution. This assumed a success rate of approximately 97%. A study by Saranteas et al reported a success rate of 95.6% in healthy volunteers undergoing saphenous nerve block just after it exited from the adductor canal. Based on these two observations, the investigators expected the success rate of DTSNB to be 95%. To establish the non-inferiority of ACSNB to DTSNB, the investigators pre-determined that the success rate of ACSNB should not be lower than 85% (the expected difference in proportions should be less than (95% - 85%) 10%). Under these assumptions, to achieve 80% power, with a one-sided type I error rate of 0.05, the study needed 59 subjects per group; 118 patients total. 120 patients were enrolled for this study., randomized to receive either ACSNB (n=58) or DTSNB (n=62).To show the non-inferiority of the ACSNB to DTSNB, the upper 95% confidence bound of the success rates (πDTSNB - πACSNB) should be less than 10%.

The normality of continuous variables was tested by the Shapiro Wilk's test. Based on the normality assumption, two independent samples t-test or Mann-Whitney U test was performed for continuous variables. Chi-square test or Fisher's exact test was performed for categorical variables.

• Study Type: Interventional
• Enrollment (Actual): 120
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 17 years to 70 years (Child, Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Patients undergoing elective foot and ankle surgery receiving saphenous nerve block for pain management
• American Society of Anesthesiologists Physical Status (ASA PS) scores 1, 2 and 3

Exclusion Criteria:

• Neuropathy
• Allergy to local anesthetics
• ASA PS scores 4 and 5

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Supportive Care
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: DTSNB; Distal transsartorial saphenous nerve block	Procedure: Saphenous nerve block; Ultrasound guided saphenous nerve blocks with 0.5% Ropivacaine for patients undergoing elective foot and ankle surgery for post-operative pain relief.
Active Comparator: ACSNB; Adductor canal saphenous nerve block	Procedure: Saphenous nerve block; Ultrasound guided saphenous nerve blocks with 0.5% Ropivacaine for patients undergoing elective foot and ankle surgery for post-operative pain relief.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Success rate of the saphenous nerve block	Loss of pin prick sensation to 2 of the 3 pre-defined areas of saphenous nerve distribution in the operative leg after performing the nerve block.	30 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Speed of onset of saphenous nerve block	Time taken for loss of pinprick sensation in 2 of the 3 pre-defined areas of saphenous nerve distribution in the leg after performing the nerve block.	30 minutes
Nerve visibility under ultrasound	Nerve visibility under ultrasound guidance, graded as 1 (clearly visible) to 3 (not visible even after local anesthetic infiltration)	30 minutes
Time taken to perform block	Time taken from skin infiltration of local anesthetic to the nerve block needle removed from patient	30 minutes

Collaborators and Investigators

• Sponsor: University of Iowa

Study record dates

Study Major Dates

• Study Start: April 1, 2013
• Primary Completion (Actual): August 1, 2014
• Study Completion (Actual): August 1, 2014

Study Registration Dates

• First Submitted: February 24, 2015
• First Submitted That Met QC Criteria: March 2, 2015
• First Posted (Estimate): March 9, 2015

Study Record Updates

• Last Update Posted (Estimate): March 9, 2015
• Last Update Submitted That Met QC Criteria: March 2, 2015
• Last Verified: March 1, 2015

More Information

Terms related to this study

• Other Study ID Numbers: 201302730