W e read with great interest Drs. Hanson and Auyong's article 1 regarding the identification of the dorsal scapular and long thoracic nerves during ultrasound-guided interscalene nerve block. As a busy orthopedic ambulatory surgery center, we perform a large number of interscalene perineural catheters for shoulder surgery (to see a demonstration of our technique, see the Supplementary Video at http://www.blockjocks.com/ka8K). To minimize the possibility of phrenic nerve blockade, we, too, use a posterior approach for placing these catheters. 2 In combination with a low-volume technique (typically <15 mL of local anesthetic), we have subjectively observed a significant decrease in the incidence of postoperative respiratory complications while maintaining a nearly 100% success rate for postoperative analgesia. We also feel that traversing the middle scalene muscle provides a relatively unobstructed path to the posterior aspect of the cervical roots within the interscalene groove and avoids many of the vital structures encountered with an anterior approach including the phrenic nerve itself, the carotid artery, and the internal jugular vein.Drs. Hanson and Auyong mention that they are unaware of any outcome data that support injury to the dorsal scapular and long thoracic nerves related to an interscalene block. We found this article to be timely as we were recently made aware of a patient who appears to have suffered long thoracic nerve injury following shoulder surgery, presumably as a result of interscalene perineural catheter placement.Like the authors, we were unable to identify any other confirmed cases of nerve block-related long thoracic or dorsal scapular nerve injuries in the regional anesthesia literature (although we suspect that underreporting may play a role). Nevertheless, our recent experience demonstrates the importance of the findings in this article. It remains unclear to us whether the addition of nerve stimulation to the use of ultrasound would effectively reduce the likelihood of injury to these nerves by allowing safe needle redirection if long thoracic or dorsal scapular nerve twitch is elicited absent ultrasound visualization during needle passage. One could argue that systematic ultrasonographic with or without nerve stimulator-assisted identification of these nerves, or at the very least awareness of their presence, could help avoid adverse outcomes such as this one. We appreciate the hard work of Drs. Hanson and Auyong and look forward to any future studies related to this subject.
Background Minimally invasive thoracic surgery (MITS) has been shown to reduce postoperative pain and contribute to better postoperative quality of life as compared to open thoracic surgery (Bendixen et al., Lancet Oncol 17:836–44, 2016). However, it still causes significant post-operative pain. Regional anaesthesia techniques including fascial plane blocks such as the erector spinae plane block (ESP) have been shown to contribute to post-operative pain control after MITS (Finnerty et al., Br J Anaesth 125:802–10, 2020). Case reports relating to ESP catheters have described improved quality of pain relief using programmed intermittent boluses (PIB) instead of continuous infusion (Bendixen et al., Lancet Oncol 17:836–44, 2016). It is suggested that larger, repeated bolus dose may provide superior pain relief, possibly because of improved spread of the local anaesthetic medications (Ilfeld and Gabriel, Reg Anesth Pain Med 44:285–86, 2019). Evidence for improved spread of local anaesthetic may be found in one study which demonstrated that PIB increased the spread of local anaesthetic medication compared to continuous infusions for continuous paravertebral blocks, which are another type of regional anaesthesia technique for the chest wall (Hida et al., Reg Anesth Pain Med 44:326–32, 2019). Similarly, regarding labour epidural analgesia, the weight of evidence is in favour of PIB providing better pain relief compared with continuous infusion (Onuoha, Anesthesiol Clin 35:1–14, 2017). Since fascial plane blocks, such as ESP, rely on the spread of local anaesthetic medication between muscle layers of the chest wall, intermittent boluses may be particularly useful for this group of blocks. However, until recently, pumps capable of providing automated boluses in addition to patient-controlled boluses were not widely available. To best of our knowledge, there are no randomised controlled trials comparing continuous infusion versus intermittent bolus strategies for erector spinae plane block for MITS in terms of patient centred outcomes such as quality of recovery. Methods This trial will be a prospective, double-blinded, randomised controlled superiority trial. A total of 60 eligible patients will be randomly assigned to receive an intermittent bolus regime of local anaesthetic vs a continuous infusion of local anaesthetic. The medication will be delivered via an ultrasound-guided erector spinae plane block catheter which will be inserted by an anaesthesiologist while the patient is under general anaesthetic before their MITS surgery begins. The primary outcome being measured is the Quality of Recovery (QoR-15) score between the two groups 24 h after surgery. Secondary outcomes include respiratory testing of maximal inspiratory volume measured with a calibrated incentive spirometer, area under the curve for Verbal Rating Score for pain at rest and on deep inspiration versus time over 48 h, total opioid consumption over 48 h, QoR-15 score at 48 h and time to first mobilisation. Discussion Despite surgical advancements in thoracic surgery, severe acute post-operative pain following MITS is still prevalent. This study will provide new knowledge and possible recommendations about the efficacy of programmed intermittent bolus regimen of local anaesthetic vs a continuous infusion of local anaesthetic via an ultrasound-guided erector spinae plane catheter for patients undergoing MITS. Trial registration This trial was pre-registered on ClinicalTrials.gov Identifier: NCT05181371. Registered on 6 January 2022. All item from the World Health Organization Trial Registration Data set have been included.
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