S.H. Renes

Ultrasound-guided low-dose interscalene brachial plexus block reduces the incidence of hemidiaphragmatic paresis.

Background and Objectives: Interscalene brachial plexus block is associated with 100% incidence of hemidiaphragmatic paresis as a result of phrenic nerve block. We examined whether an ultrasound (US)-guided interscalene brachial plexus block performed at the level of root C7 versus a nerve stimulation interscalene brachial plexus block, both using 10 mL of ropivacaine 0.75%, resulted in a lower incidence of hemidiaphragmatic paresis. Methods: In a prospective randomized controlled trial, 30 patients scheduled for elective shoulder surgery under combined general anesthesia and interscalene brachial plexus block were included. Interscalene brachial plexus block using the same dose was performed using either US or nerve stimulation guidance of ropivacaine for both groups. General anesthesia was standardized. Ventilatory function was assessed using spirometry, and movement of the hemidiaphragm was assessed by US. Results: Two patients in the US group showed complete paresis of the hemidiaphragm, but in the nerve stimulation group, 12 patients showed complete and 2 patients had partial paresis of the hemidiaphragm (13% versus 93%, respectively; P < 0.0001). Ventilatory function (forced expiratory volume at 1 second, forced vital capacity, and peak expiratory flow) was significantly reduced in the nerve stimulation group compared with the US-guided group (P < 0.05). One block failure occurred in the nerve stimulation group compared with none in the US group. No adverse effects occurred in either group. Conclusions: Ultrasound-guided interscalene brachial plexus block performed at the level of root C7 using 10 mL of ropivacaine 0.75% reduces the incidence of hemidiaphragmatic paresis.

Minimum effective volume of local anesthetic for shoulder analgesia by ultrasound-guided block at root C7 with assessment of pulmonary function.

Background and Objectives: This study was performed to determine the minimum effective volume of ropivacaine 0.75% required to produce effective shoulder analgesia for an ultrasound (US)-guided block at the C7 root level with assessment of pulmonary function. Methods: Using the Dixon and Massey up-and-down method study design, 20 patients scheduled for elective open shoulder surgery under combined general anesthesia and continuous interscalene brachial plexus block were included. Initial volume of ropivacaine 0.75% was 6 mL; block success or failure determined a 1-mL decrease or increase for the subsequent patient, respectively. General anesthesia was standardized. A continuous infusion of ropivacaine 0.2% was started at a rate of 6 mL/hr at 2 hrs after completion of surgery. Ventilatory function was assessed using spirometry, and movement of the hemidiaphragm was assessed by US. Results: The minimum effective volume of local anesthetic in 50% and 95% of the patients was 2.9 mL (95% confidence interval, 2.4-3.5 mL) and 3.6 mL (95% confidence interval, 3.3-6.2 mL), respectively. Ventilatory function and hemidiaphragmatic movement was not reduced up to and including 2 hrs after completion of surgery, but 22 hrs after start of the continuous infusion of ropivacaine 0.2%, ventilatory function and hemidiaphragmatic movement were significantly reduced (P < 0.001). Conclusions: The minimum effective volume of local anesthetic for shoulder analgesia for a US-guided block at the C7 root level in 50% and 95% of the patients was 2.9 and 3.6 mL, respectively. Pulmonary function was unchanged until 2 hrs after completion surgery, but reduced 22 hrs after start of a continuous infusion of ropivacaine 0.2%.

Different Approaches to Ultrasound-guided Thoracic Paravertebral Block An Illustrated Review

Given the fast development and increasing clinical relevance of ultrasound guidance for thoracic paravertebral blockade, this review article strives (1) to provide comprehensive information on thoracic paravertebral space anatomy, tailored to the needs of a regional anesthesia practitioner, (2) to interpret ultrasound images of the thoracic paravertebral space using cross-sectional anatomical images that are matched in location and plane, and (3) to briefly describe and discuss different ultrasound-guided approaches to thoracic paravertebral blockade. To illustrate the pertinent anatomy, high-resolution photographs of anatomical cross-sections are used. By using voxel anatomy, it is possible to visualize the needle pathway of different approaches in the same human specimen. This offers a unique presentation of this complex anatomical region and is inherently more realistic than anatomical drawings.

Ultrasound-guided training in the performance of brachial plexus block by the posterior approach: an observational study

The application of ultrasonography in guiding and controlling the path of the stimulating needle to the brachial plexus via the posterior approach (Pippa technique) was studied. In 21 ASA physical status 1 and 2 patients, scheduled for surgery of the shoulder or upper arm, needle insertion was monitored by ultrasonography and the interaction between needle, surrounding structures and brachial plexus was followed. During injection, the spread of local anaesthetic was visualised and a prediction of block success was made. One failure was predicted. Complete block was achieved in 20 (95%) patients. One potential complication, puncture of the carotid artery, was prevented using ultrasound. Ultrasound is a useful tool in the training and performance of a neurostimulation‐guided brachial plexus block by the posterior approach. Ultrasonographic guidance may prevent serious complications associated with this approach to the brachial plexus.

Vertical Infraclavicular Brachial Plexus Block: Needle Redirection After Elicitation of Elbow Flexion

Background: In vertical infraclavicular brachial plexus block, success depends on distal flexion or extension response. Initially, elbow flexion (lateral cord) is generally observed. However, specific knowledge about how to reach the medial or posterior cord is lacking. We investigated the mid-infraclavicular area in undisturbed anatomy and tested the findings in a clinical setting. Methods: Along a length of 35 mm around the mid-infraclavicular point, cryomicrotomy sections of 5 shoulders from cadavers were used todetermine the topography of the cords in relation to one another and the axillary artery. Based on the findings, the anesthesiologists were instructed on how to elicit a distal motor response after an initial elbow flexion response in single-shot, Doppler-aided, vertical infraclavicular block in a series of 50 consecutive patients. Results: In the mid-infraclavicular area, the lateral cord always lies anterior to either the posterior or the medial cord and cranial to the axillary artery; the posterior cord was always cranial to the medial cord; and both cords were always located dorsal to the artery. In the clinical study, in 98% of the included patients, finger flexion or finger and/or wrist extension was elicited as predicted. The overall success rate was 92%. No vascular or lung puncture occurred. Conclusions: In the clinical study, in 98% of cases, the final stimulation response of posterior or medial cord was found as predicted by the findings of the anatomic study. Once elbow flexion is elicited, a further (ie, deeper) advancement of the needle will result in the proper distal motor response.

Ipsilateral brachial plexus block and hemidiaphragmatic paresis as adverse effect of a high thoracic paravertebral block.

Background: Thoracic paravertebral block is regularly used for unilateral chest and abdominal surgery and is associated with a low complication rate. Case Reports: We describe 2 patients with an ipsilateral brachial plexus block with Horner syndrome after a high continuous thoracic paravertebral block at T2-3. One patient also developed an ipsilateral hemidiaphragmatic paresis, an adverse effect that has not been reported before. Subsequent radiologic examination revealed a limited thoracic cephalad spread of the radiopaque dye and a laterally ascending spread from the thoracic paravertebral space toward and around the brachial plexus. We offer potential explanations for these phenomena. Conclusions: Brachial plexus block can occur by a route parallel to a nerve connecting the second intercostal nerve and T1 nerve, that is, Kuntz nerve. The hemidiaphragmatic paresis was attributed to the ascending spread of local anesthetic toward the area where the phrenic nerve bypasses the subclavian artery and vein.

Thoracic Paravertebral Block

In thoracic paravertebral block (TPVB), local anesthetic is injected in the vicinity of the thoracic spinal nerves, in order to obtain an ipsilateral somatic, segmental, and sympathetic nerve block. This technique can be used for unilateral thoracic and abdominal surgery. The thoracic paravertebral block has a high success rate and is associated with a low complication risk. The incidence of pneumothorax in the classical technique is 0.5 %; the use of ultrasound will likely decrease this. In this chapter, the anatomy of the thoracic paravertebral space is reviewed, and different techniques, including ultrasound-guided techniques, for performing thoracic paravertebral block are described.

Reply to Dr. Cornish.

To the Editor: W e write with reference to an article by Fredrickson et al, which claims an advantage for continuous peripheral nerve catheter management of pain relief versus single-shot blocks after a range of more Bminor[ shoulder surgeries. We, too, have had a large experience in this area and wish to query certain aspects of their study. We are puzzled that no pain scores have been included for the period within the first 24 hours after surgery. Presumably, both groups had no pain initially. It would be interesting to know when the single-shot blocks wore off and what strategies were used to counter its effect? There seems to have been more difficulty siting the single-shot blocks, and how this may or may not have affected the duration of the block is uncertain. From the data presented, it is difficult to judge the extent of the separation between the 2 groups. There was some mixing of surgical groups, which has the potential to confound results. For example, our experience has been that lateral clavicular surgeries do not warrant continuous catheter management. Elastomeric pumps require a large volume (400 mL) to fill. Given that there is no advantage to running a catheter longer than a day and a half according to their data, a large volume of local anesthetic (È200 mL) is likely to be wasted with this approach. The authors have rightly commented on other costsVsurely, this is another one to consider. We do agree, however, with the authors’ comment that the first 36 hours after surgery seems to be the time of greatest advantage for running peripheral nerve catheters in these situations.