Nerve Puncture and Apparent Intraneural Injection During Ultrasound-Guided Axillary Block Does Not Invariably Result in Neurologic Injury

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Nerve Puncture and Apparent Intraneural Injection During Ultrasound-Guided Axillary Block Does Not Invariably Result in Neurologic Injury
Paul E. Bigeleisen
(Anesthesiology, 105:779-783, 2006)
Department of Anesthesiology, Lindsay House Surgery Center at Linden Oaks, Rochester, NY.
The general assumption has been that needle-nerve contact and intraneural injection during peripheral nerve block procedures will inevitably cause neurological damage. Debate also centers on what the ultrasound images mean when the technique is used to perform the procedure. In a previous retrospective study of 50 ultrasound-guided blocks, each patient had 1 or more nerves punctured, followed by an intraneural injection with local anesthetic, but they did not have any known untoward sequelae. Therefore, the present prospective study was designed to determine the incidence of apparent nerve puncture and intraneural injection of local anesthetic. Any transient or permanent injury to the nerve was recorded.
Fifty patients undergoing ultrasound-guided axillary block for surgical repair of the basal joint of the thumb were enrolled. Before the block was performed and sedation administered, each patient had a sensory examination using pinprick, alcohol wipe (cold and soft brush [light touch]). A score of 1 was given if the patient could identify the modality and 0 if not. A qualitative muscular examination was also performed. All axillary blocks were performed with the arm abducted at 120 degrees, the shoulder externally rotated, and the forearm flexed at 90 degrees. The axillary artery and vein, pectoralis major muscle, biceps muscle, and coracobrachialis muscle and appropriate nerves were identified on ultrasound. Each nerve was anesthetized by eliciting a paresthesia or piercing the fascia around the nerve by the sensation of a pop. Then, an anesthetic mixture of 2.6 mg/mL of bupivacaine, 10 mg/mL of lidocaine, and 3 μg/mL of epinephrine was injected. If the injection seemed to be intraneural, the needle was withdrawn, and 2 to 3 mL of the mixture was injected around the nerve. If the first injection produced a halo, another 2 to 3 mL of local anesthetic was injected around the nerve. The ultrasound sequence was noted on a digital recorder, and a nurse recorded the clinical activities of the investigator and the patient's responses during the injections. Qualitative sensory and muscle testing was repeated at 5 and 20 minutes after the block was completed and at a 6-month follow-up visit, at which patients were examined for any neurological deficit.
Twenty-two patients were excluded because of preoperative abnormalities in the sensory/motor examinations, and 2 others were lost to follow-up. The musculocutaneous and radial nerves were the easiest to block, showing the greatest block at 5 and 20 minutes for both sensory and motor block. No patient reported surgical pain, and none needed local anesthetic supplementation during the surgery. None required analgesia in the recovery room. All patients who completed the study had normal qualitative sensory and motor examinations at the 6-month visit. On force meter testing preoperatively and at 6 months postoperatively, no differences were noted (preoperative supination and pronation, 5.7 ± 0.6 and 4.4 ± 0.8 kg, respectively; postoperatively, 5.7 ± 0.8 and 4.5 ± 0.5 kg, respectively). Nerve punctures occurred in 8 musculocutaneous nerves, 22 median nerves, 23 radial nerves, and 19 ulnar nerves. Halos were seen in 18, 4, 3, and 7 nerves, respectively; swelling occurred in 5, 4, 3, and 1, respectively. Halo and swelling occurred in 3, 18, 20, and 18, respectively; paresthesia or dysesthesia was reported after puncture of 4, 23, 24, and 15 nerves, respectively. Three patients reported tenderness at the injection site in the axilla the day after surgery; it resolved in all patients within 3 weeks without treatment.

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