Original contribution
Nerve stimulator versus ultrasound guidance for placement of popliteal catheters for foot and ankle surgery,☆☆

https://doi.org/10.1016/j.jclinane.2011.06.008Get rights and content

Abstract

Study Objective

To determine whether ultrasound guidance improves the quality of continuous popliteal block when compared with a nerve stimulator after major foot and ankle surgery.

Design

Prospective, randomized, double-blinded clinical trial.

Setting

Operating room, Postanesthesia Care Unit (PACU), and hospital wards of a university-affiliated hospital.

Patients

45 ASA physical status 1, 2, and 3 patients undergoing elective major foot and ankle surgery.

Interventions

Placement of a popliteal sciactic nerve catheter using either nerve stimulator or ultrasound guidance. In the PACU, a continuous infusion of ropivacaine 0.2% was started at a basal rate of 4 mL/hr and adjusted in a standardized fashion to maintain visual analog scale (VAS) pain scores < 4. All patients also received intravenous (IV) patient-controlled analgesia with hydromorphone and oral opioids.

Measurements

VAS pain scores at rest and with physical therapy, ropivacaine use, opioid use, and opioid-related side effects were recorded.

Main Results

Cummulative ropivacaine use was lower in patients whose catheter was placed by ultrasound than by nerve stimulator guidance (mean 50 vs 197 mL, P < 0.001). Pain scores at rest and during activity were similar between groups. Cumulative opioid consumption (mean 858 vs 809 mg oral morphine equivalents) and daily frequencies of nausea (5% to 33% vs 0 to 24%) and pruritus (0 to 21% vs 0 to 24%) were similar between groups. Length of hospital stay was similar between groups (3.5 vs 3.7 days).

Conclusions

Ultrasound guidance was associated with less local anesthetic consumption than with the nerve stimulator; however, there was little clinical benefit, as all other outcomes were similar between groups.

Introduction

Continuous perineural analgesia of the sciatic nerve via the popliteal fossa offers significant benefits after major foot and ankle surgery. Previous randomized controlled trials (RCTs) have shown that continuous popliteal block versus either placebo or intravenous (IV) patient-controlled analgesia (PCA) opioids results in markedly improved postoperative analgesia, decreased opioid use, decreased opioid-related side effects, greater patient satisfaction, and greater short-term functional activity [1], [2].

Currently, popliteal catheters are commonly inserted after initial localization with a nerve stimulator-guided needle [3]. Thus, precise location of the needle and catheter cannot be ascertained. Ultrasound guidance has gained popularity for regional anesthesia as it allows precise localization of neural targets and needle placement. A recent systematic review of ultrasound guidance for regional anesthesia noted that ultrasound versus nerve stimulator for lower-extremity, single-shot nerve blocks, including popliteal blocks, improved the quality and onset of anesthesia [4]. Thus, ultrasound guidance may improve the quality of continuous popliteal block when compared with a similar block by nerve stimulator. However, only a single RCT has compared the nerve stimulator with ultrasound guidance for placement of continuous popliteal block catheter, and that study primarily was interested in the time required for catheter placement [5]. We performed this prospective, randomized, double-blinded study to compare nerve stimulator with ultrasound guidance for postoperative analgesia after major foot and ankle surgery.

Section snippets

Materials and methods

After Hospital for Special Surgery Institutional Review Board approval and written, informed consent were obtained, patients undergoing major foot/ankle surgery with a planned hospital stay of more than 48 hours and requiring a perineural sciatic nerve catheter were enrolled. Exclusion criteria included neurological deficit in the operative extremity; infection at the site for the block; allergy to local anesthetics; pregnancy; diabetes; history of chronic opioid use; or ASA physical status

Results

Fig. 1 displays the CONSORT (Consolidated Standards of Reporting Trials) flow of patients through the study. After randomization, 6 patients (4 in the nerve stimulator and two in the ultrasound group) were excluded due to protocol violations (eg, PCA pump misprogramming or malfunction, incorrect bolus dose, or infusion adjustments). Patient characteristics and types of surgical procedures were similar between groups (Table 1). All patients had successful sensory block to cold in the sciatic

Discussion

The use of ultrasound markedly decreased consumption of local anesthetic, which suggests that ultrasound allowed closer approximation of the popliteal catheter than did nerve stimulator guidance. Several RCTs also noted greater efficacy for ultrasound versus nerve stimulator guidance for single-shot popliteal block with either significantly faster onset or success rates [8], [9], [10], [11]. Thus, it is likely that ultrasound allowed superior targeting of the block needle so that subsequent

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No author has financial interests to disclose.

☆☆

Funding: Hospital for Special Surgery's Anesthesiology Department Research and Education Fund.

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