Regional Anesthesia: Brief Report
In emergency surgery, axillary and midhumeral brachial plexus blocks represent more than 50% of all regional anesthesia techniques performed (1). The choice between the two approaches remains controversial. Only three prospective studies have compared these two techniques, with different methodology and results (2–4). In a double-injection axillary block, injection of local anesthetic on the median and radial nerves is mandatory (5), whereas all four nerves are identified using the midhumeral approach. Several studies suggest that block discomfort is reduced by fewer injections (6). In this prospective and randomized study, we compared the efficacy and patient acceptance of the midhumeral block described by Dupre (7) to the double-injection axillary brachial plexus block described by Sia et al. (4).
After informed patient consent and institutional approval, 90 ASA I-III patients undergoing emergency surgery below the elbow were included in this study. Exclusion criteria were coma, usual contraindications to regional anesthesia techniques, or multiple injuries. Midhumeral and axillary brachial plexus blocks were performed according to Dupré and Sia et al.’s description (5,7). After randomization, 40 mL of 0.75% ropivacaine was equally and slowly injected, after negative aspiration test for blood, on 2 (median, then radial nerves, group axillary (A), n = 45) or on 4 (median, radial, ulnar, then musculocutaneous nerves, group midhumeral (H), n = 45) nerves through a short bevel 50-mm insulated needle using a nerve stimulator technique. In both groups, nerve stimulation began at 1.5 mA, 2 Hz, and 100 μs and the needle position was judged adequate when output ≤0.5 mA still elicited a motor response. In case of vascular puncture, a new insertion was attempted.
At the end of the injection, each patient was asked to evaluate the block on a verbal rating scale from 1 = comfortable to 4 = intolerable. The time to perform the block was defined as the time from the initial insertion of the needle to its removal. The sensory onset time of the block was assessed in all the upper limb areas (except axillary) every 5 min until 30 min after the last injection. Sensory block was assessed with a 25-gauge needle and defined as normal (score 0), analgesia (score 1), or anesthesia (score 2). The block was assessed as complete if analgesia or anesthesia was observed at 30 min in all the sensory areas below the elbow. Motor block was assessed every 5 min until 30 min for 4 motor nerves and scored 0 = no motor block; 1 = minor movements; 2 = no movement. Adverse effects were recorded. After 30 min, in case of incomplete block, the unblocked nerve(s) implicated in the surgical site were blocked at the elbow level. Patients were declared ready for surgery when they had a complete block (analgesia in all areas necessary for surgery). In case of failure, general anesthesia was performed.
Primary and secondary block effectiveness was calculated as the percentage of patients in each group in whom a complete block was obtained at 30 min or who had surgical analgesia after supplementary blocks.
Quantitative variables were expressed as mean ± sd. Qualitative variables were expressed as number (%). Student’s t-test, Fisher’s exact test, χ2 test, or Mann-Whitney U-test was used as appropriate to compare the two groups. P < 0.05 was considered statistically significant.
No difference between the groups was found with regard to demographic data or surgical site (Table 1).
No patient was excluded from the study because of absence of muscular response during nerve stimulation. Patients in group A were ready for surgery 5 min before those in group H (22 ± 6 min in group A versus 27 ± 9 min in group H, P < 0.01) and also judged the technique more comfortable than did those in group H (P < 0.05, Table 2).
Primary and secondary block effectiveness was similar in both groups (Table 2). Among the different nerve (Table 3), a greater success rate and a shorter onset of sensory block for anesthetizing the musculocutaneous nerve were seen in Group H. The rate of motor block was similar for the 3 nerves, except for the musculocutaneous nerve (Table 4).
The main result of this study was that a double-injection axillary brachial plexus block was superior to midhumeral block for emergency hand surgery. This finding is consistent with previous studies examining midhumeral and axillary blocks using from 1 to 4 injections of nerves of interest. Bouaziz et al. (2) concluded that the midhumeral approach was superior to axillary block when only one nerve innervating the surgical site plus the musculocutaneous nerve were blocked (Lavoie’s approach) (8). Unfortunately, Lavoie’s approach is not recommended, particularly because of frequent failure of the radial nerve block (2,9). In contrast, both midhumeral and 4-injection axillary blocks provided frequent success and rapid onset (3). We studied a double-injection axillary block, as this offers a similar success rate to 3- and 4-injection axillary block but with the added advantage of fewer injections (3,4). Thus, we were able to confirm that 2-injection axillary block provides similar success to 4-injection midhumeral block but with the advantages of fewer needle entries, faster performance time (a 5-minute difference is clinically relevant for patient comfort in an emergency situation), and better patient tolerance, provided the musculocutaneous nerve does not need to be blocked.
In our study using ropivacaine, the onset time of sensory block was 14 minutes in both groups, which is very similar to that found with lidocaine (2,3). Ropivacaine appears to be the local anesthetic of choice for block performed in the emergency setting when prolonged postoperative analgesia is requested.
In conclusion, the double-injection axillary brachial plexus block performed with ropivacaine is superior for emergency hand surgery, as compared with the midhumeral block: the time to perform the block is diminished and the patient’s acceptance is increased. However, a supplemental block of the musculocutaneous nerve may be necessary in 20% of cases, when its cutaneous distribution is involved in the surgical area.
The authors thank Jame Torrie, MD, for her invaluable help in preparing the manuscript.
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© 2006 International Anethesia Research Society
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