Literature reports on bilateral plexus blocks, and more specifically, bilateral brachial plexus blocks, are rare and almost anecdotal (1). There are more reports on bilateral blocks performed as an adjuvant for postoperative pain control along with general anesthesia for the surgery itself (2–4) or for other nonsurgical situations (5). There are several factors contributing to this scarcity. Performing a bilateral technique on one patient is time consuming, possibly more uncomfortable to the patient, and potentially associated with an increased failure rate because it usually implies using less local anesthetic solution on each side. However, most importantly, these bilateral blocks carry an increased risk of technique-related complications and local anesthetic toxicity. Thus, only very few clinical situations seem amenable to a bilateral block. We report a clinical scenario where a bilateral brachial block seemed appropriate.
A 38-year-old man, diagnosed with AIDS 2 yr before, was scheduled to undergo incision and drainage of skin abscesses affecting both upper extremities. The surgeons planned to operate on both sides simultaneously with two teams. The patient had had several admissions in the preceding 12 mo for complications related to his main condition. He had experienced general anesthesia on several occasions, the last one having been complicated with pneumonia and delayed extubation. He had a 2-wk history of malaise and weight loss, but was alert, oriented, and cooperative. He complained of acute pain on both upper extremities related to his skin lesions. He made clear that this time he would like to remain awake during the procedure avoiding general anesthesia if at all possible. On examination, he appeared physically diminished, febrile, and slightly tachypneic. His oxygen saturation on room air was 97%–98%. He was able to tolerate the supine position with a small pillow under his head. His skin lesions on the right side affected the hand, wrist, forearm, elbow, and distal arm. On the left side, the lesions were similar but more distally located, leaving the arm down to the elbow unaffected.
The patient was told about the option of bilateral brachial plexus block to be performed sequentially under minimal sedation (the patient wanted to remain awake). The plan included using a decreased volume of local anesthetic on each side to lower the total dose of it and the possibility of toxicity. He was told also that decreasing the local anesthetic volume used on each side would also decrease the chances for success while still carrying a higher risk for toxicity, as compared with a single technique. He was willing to proceed, with the understanding that general anesthesia could not be completely excluded.
The patient had a functional IV on the right foot and had been started on systemic antibiotics after culture samples had been obtained in the emergency room. Standard ASA monitors were applied, and supplemental oxygen by nasal cannula was started. Midazolam 1 mg IV was given. The right neck, which was free of skin lesions, was prepared with Betadine, and our customary supraclavicular block (6) was performed, using a 22-gauge, 50-mm, insulated needle (B. Braun, Bethlehem, PA) and a nerve stimulator (Stimuplex DIG, B. Braun). After an adequate hand response was obtained at 0.5 mA, 20 mL of 1% mepivacaine plus 1:200,000 epinephrine were injected slowly with frequent aspirations in between. Visual and oral contact with the patient was kept at all times. Ten minutes after the injection, and with excellent anesthesia already developing on the right side, the contralateral technique was started. The left axilla was prepared with Betadine solution as usual. A similar 22-gauge needle connected to our nerve stimulator was used. After a brisk radial response with extension of the fingers was obtained, the injection was started using 30 mL of 1% mepivacaine plus 1:200,000 epinephrine. The local anesthetic was slowly injected with frequent aspirations in between. The patient and monitors were carefully watched. Before removing the needle, it was redirected laterally under the biceps into the substance of the coracobrachialis muscle. An immediate twitch from stimulation of the musculocutaneous (elbow flexion) was obtained. At this point, 3 mL of 1% mepivacaine plain was given after aspiration.
At the end of the left axillary procedure, the right side was already adequately numbed, and surgical scrubbing was allowed to proceed on that side. Ten minutes after the axillary procedure, and with good anesthesia developing, the surgical scrubbing on the left side also proceeded.
The incision was made approximately 15 min after the end of the axillary technique. Surgery was performed uneventfully on both sides with superb bilateral anesthesia. The patient was talkative and relaxed during the procedure that lasted for approximately 55 min. Approximately 3 h after our initial technique, the anesthesia had begun to dissipate, starting on the side that received the axillary block. The next day the patient was doing well without any residual numbness. The patient went home 7 days after the procedure. One year later, he had managed to avoid new hospital admissions, had regained some weight, and continued receiving his AIDS treatment.
There are few reports on bilateral plexus blocks in the literature. A bilateral technique takes time to accomplish, and it theoretically doubles the amount of any discomfort the patient may experience during a single technique. Potentially, it carries a lesser success rate and an increased risk of side effects and local anesthetic toxicity. We chose to perform a supraclavicular block on the side where the skin lesions reached more proximally on the arm because we have extensive experience with this technique (7) and because it has the ability to provide reliable anesthesia of the distal arm (8). It is generally accepted that this technique carries a lesser risk of phrenic nerve paralysis (9) than an interscalene block, but for practical purposes, it should be assumed to happen frequently. However, it is the technique that is most often associated with pneumothorax. Whereas we fear this complication as much as anybody, we perform a technique (6) that in our hands has proved to be highly safe (7). This technique brings the needle in proximity to the brachial plexus trunks. There are just three trunks, and they are close to one another, explaining both the rapid onset and the high success rate of this approach.
In our practice, we usually perform the supraclavicular technique with 30–40 mL of local anesthetic solution. We chose to inject on this patient 20 mL of a solution containing epinephrine. Decreasing the volume used on any of these techniques would eventually reach a critical point below which the overall success rate would start to decrease. Twenty milliliters on this patient produced a quick and dense block, reaffirming the belief that 40 mL in the supraclavicular area may be excessive for most adults.
The axillary block is different. The block is performed at the level of the terminal branches of the brachial plexus, which arrange themselves around the axillary artery. Thus, the elements to be blocked are not only more numerous as compared with the supraclavicular area, but also more distant from one another having a vascular structure and variable amount of organized connective tissue in between. Therefore, if a single injection is preferred, as it was in this case, the volume to inject must be greater than the one used for supraclavicular blocks. We usually inject 50 mL of local anesthetic solution in the axillary region for a single injection technique. In this case, we injected just 30 mL of a solution containing epinephrine. By this time, we already knew that our supraclavicular block had been successful, so we could concentrate on achieving success on the axillary side, trying to keep the total dose of local anesthetic as small as possible. Blocking the musculocutaneous nerve separately using a nerve stimulator helped to achieve this goal.
Bilateral supraclavicular blocks should not be attempted because of the risk of overwhelming respiratory compromise due to bilateral diaphragmatic paralysis and the potential for pneumothorax. Thus, combining a supraclavicular block on the side of proximal lesions with an axillary block on the other side was adequate to this clinical scenario. Although, bilateral blocks of any kind must be assessed carefully on a case-by-case basis.
The success we obtained on this case should not be interpreted as a license to dismiss concerns about double technique side effects and local anesthetic toxicity. The total dose used on this case was 500 mg of mepivacaine with epinephrine and 30 mg without. This exceeds the recommended total dose for this drug. We believe that because the total dose of local anesthetic was injected over an extended period of time, the patient might have had an increased tolerance to it. This case was also peculiar because the patient wanted not only to avoid general anesthesia, but also to remain awake during the procedure. It is generally accepted that drugs used for sedation may help to decrease the rate of development of local anesthetic toxicity (1). Using only 1 mg of midazolam may have placed this patient at a greater risk of developing such toxicity. The American Society of Regional Anesthesia convened a “Conference on Local Anesthetic Toxicity”(10) in November 2001 stressing the importance of this issue. Several practitioners with vast regional anesthesia experience believe that our current recommended total dose for local anesthetics might be a bit conservative and could be increased. Thus far, there is no consensus. We would like to share this clinical experience, where the strengths and weaknesses of two different regional anesthesia techniques were adequately combined to successfully manage a peculiar clinical situation.
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