Faculty Bibliography

BACKGROUND: Peripheral nerve blocks are almost always performed as blind procedures. The purpose of this study was to test the feasibility of seeing individual nerves of the brachial plexus and directing the block needle to these nerves with real time imaging. METHODS: Using ultrasound guidance, infraclavicular brachial plexus block was performed in 126 patients. Important aspects of this standardized technique included (i) imaging the axillary artery and the three cords of the brachial plexus posterior to the pectoralis minor muscle, (ii) marking the position of the ultrasound probe before introducing a Tuohy needle, (iii) maintaining the image of the entire length of the needle at all times during its advancement, (iv) depositing local anaesthetic around each of the three cords and (v) placing a catheter anterior to the posterior cord when indicated. RESULTS: In 114 (90.4%) patients, an excellent block permitted surgery without a need for any supplemental anaesthetic or conversion to general anaesthesia. In nine (7.2%) patients local or perineural administration of local anaesthetic, and in three (2.4%) conversion to general anaesthesia, was required. Mean times to administer the block, onset of block and complete block were 10.0 (SD 4.4), 3.0 (1.3) and 6.7 (3.2) min, respectively. Mean lidocaine dose was 695 (107) mg. In one patient, vascular puncture occurred. In 53 (42.6%) patients, an indwelling catheter was placed, but only three required repeat injections, which successfully prolonged the block. CONCLUSION: The use of ultrasound appears to permit accurate deposition of the local anaesthetic perineurally, and has the potential to improve the success and decrease the complications of infraclavicular brachial plexus block

It is fortunate that serious embolic phenomena are uncommon because, with the exception of neurosurgery in the sitting position and cardiac surgery, thoracic echocardiography and the precordial Doppler device, the most sensitive indicators of embolism, are seldom used. Vigilance is required of the anesthesiologist to recognize the rapid fall in end-tidal PCO2, the usual first indicator of a clinically significant PE. Any sudden deterioration in the patient's vital signs should include embolism in the differential diagnosis, particularly during procedures that carry a high risk of the complication

Large dose (7-18mg/kg) and high volume (30-60ml) of local anesthetics (LA) have been used to improve the success rate of brachial plexus blocks.1 Ultrasound (US) guidance permits deposition of LA closely around each cord.2 We hypothesized that this method permits using smaller than usual dose and volume. Methods: After Institutional Review Board approval, 14 consecutive consenting patients undergoing upper extremity surgery were given an US guided infraclavicular block using carbonated (1ml/10ml) lidocaine, 2%, with 1:200,000 epinephrine. The Block was administered using a 2.5 MHz probe (HP 77020A, Andover, MA) and 17G Tuohy needle. Each patient was administered midazolam,1-2 mg, and fentanyl,25-50 mcg prior to the block. A 19G catheter with its tip placed between the axillary artery and the posterior cord, served to inject 10 ml LA if block began to fade during surgery. The final dose of LA was determined based on satisfactory spread observed sonographically around each cord; the maximal dose did not exceed 340 mg in any patient. Time to perform the block,onset of analgesia and motor weakness, complete sensory and motor block, and the time to intraoperative dissipation of block, if it occurred, were recorded. Results:In all patients surgery was completed without any need for general anesthesia, additional opioid or intravenous anesthetic agents, and/or LA infiltration of the surgical field. Time to perform the block was 11.1± 2.7 minutes. Mean±SD body weight of patients was 72.6 ± 13.4 kg. In all patients mean± initial dose of lidocaine was 296 ±39.1mg (4.1 ±0.9 mg/kg), and LA solution volume was 16.24 ± 1.74 SD ml, respectively. Complete sensory and motor block occurred in 4.8 ± 2.6 min. Mean ± SD duration of surgery was 103±47.min. One patient had a patchy sensory block in radial nerve distribution at 5 min after injection, requiring 5ml at 5 minutes and 10 ml each at second and third hour during surgery through the catheter. Two other patients required 10 ml after one and 1.5 hours of initial successful blockade, respectively. Discussion: US guidance may permit reduction of dose and volume of LA, but the duration of block may also be shortened. This may be overcome by placement of an indwelling catheter. Reduction of dose by this method may have clinical implications: minimizing the likelihood of toxicity, ability to administer regional anesthesia at multiple areas of the body at the same time, and short recovery room stay