ULTRASOUND-GUIDED SELECTIVE BLOCK OF THE UPPER TRUNK OF THE BRACHIAL PLEXUS.
DESCRIPTION OF A NEW APPROACH
Leonardo Henrique Cunha Ferraro, Ph D; Thiago Nouer, MD; Rioko Sakata; Ph D
Division of Anesthesiology, Pain and Intensive Care, Federal University of São Paulo, Brazil
Interscalene brachial plexus block is the most commonly performed regional anesthesia technique to promote analgesia for shoulder surgeries. However, this technique is associated with close to 100% incidence of hemidiaphragmatic paresis due to phrenic nerve block, being contraindicated in patients with limited pulmonary reserve. Low volumes of local anesthetics were used to decrease the incidence of hemidiaphragmatic paralysis, but did not eliminate the incidence of phrenic nerve block.
Describe a new technique of selective block of upper trunk of brachial plexus to promote shoulder analgesia, without blocking phrenic nerve.
These are preliminary data of case series. Patients scheduled for rotator cuff surgery without cognitive impairment or active psychiatric condition, infection at the puncture site of the blockage, coagulopathy and history of allergy to bupivacaine were eligible to the study.
After signing a consent form, patients received 6 mL of 0,5% bupivacaine under the upper trunk, closed to the suprascapular outlet and below the omohyoid muscle, guided by ultrasound (M-Turbo®, Sonosite, Fujifilm, Bothell, WA, USA).
To perform this new approach, the upper trunk is followed until the supraclavicular region, where it joins the rest of the brachial plexus posterolateral to the subclavian artery. In this area, the identification of suprascapular nerve outlet has been described, detaching itself from the brachial plexus and proceeding posteriorly and deeply to the omohyoid muscle. It is possible to assume that the upper trunk remains intact until the exit of suprascapular nerve.
Successful block was defined as presence of adequate motor block (motor score of ≤ 2 on modified Bromage scale), absent sensation to cold and pinprick sensation within 30 minutes of injection. The muscles tested were: deltoid and biceps; the thermal and painful sensitivities of the C5 and C6 dermatomes were examined.
To evaluate the phrenic nerve, diaphragmatic excursion was assessed by ultrasonography of the ipsilateral hemidiaphragm at the cephalad border of the zone of apposition of the diaphragm to the costal margin between the mid-clavicular and anterior axillary lines. Decrease between 25% and 75% of the diaphragmatic movement was considered paresis and decrease greater than 75% was considered paralysis. Pain scores and analgesic consumption were assessed in the PACU.
Until the present moment, nine patients underwent this new technique. Eight patients underwent arthroscopic surgery. Due to lateral positioning, these patients also received general anesthesia. One patient underwent conventional surgery. For this patient, the surgeon infiltrated 3 mL of lidocaine at the incision site because the incision was performed in the area innervated by the supraclavicular nerve and the procedure was performed only with sedation. All blocks were considered positive. In addition, hemidiaphragmatic movement was not reduced at 30 minutes after the block and 1 and 2 hours after completion of surgery. Surgical procedures were performed uneventfully and no patient reported pain in the PACU.
This case series shows a new selective upper trunk block for analgesia of shoulder surgery. With this approach, it was possible to perform the block more distant in relation to phrenic nerve, avoiding its block. Phrenic nerve blocks did not occurred probably due to the absence of spread of local anesthestic cranio-caudal and anteroposterior that could reach it. Therefore, this new technique promoted analgesia without altering postoperative ventilatory function.