Bilateral Continuous Suprascapular Nerve Blocks for Bilateral Shoulder Hemiarthroplasty

A&A Case Reports: 15 September 2016 – Volume 7 – Issue 6 – p 125–128

Authors: Flaherty, James M. MD et al

We report a novel case of a patient undergoing a bilateral shoulder hemiarthroplasty for chronic bilateral shoulder dislocations with proximal humeral fractures. Bilateral selective suprascapular nerve catheters were placed preoperatively with the intent to provide continuous local anesthetic-based analgesia while sparing diaphragmatic function. Postoperative respiratory mechanics were relatively spared while numerical rating scale pain scores were suggestive of analgesic benefit.

Written permission to publish this case report was obtained directly from the patient described below.

Regional anesthesia provides effective analgesia after major shoulder surgery while decreasing opioid consumption, improving patient satisfaction, and hastening readiness for discharge.^1–3 The traditional approach of continuous brachial plexus block using an interscalene approach, however, causes hemidiaphragmatic paresis in 100% of patients.⁴ In otherwise healthy patients undergoing unilateral shoulder surgery, this is well tolerated and viewed as an acceptable consequence of brachial plexus blockade. However, the impact of bilateral continuous interscalene anesthesia has not been rigorously investigated.

A continuous selective suprascapular perineural catheter may be an effective alternative for providing shoulder analgesia. Indeed, the suprascapular nerve provides 70% of shoulder innervation, and anatomically can be blocked at a greater distance from the more medially located phrenic nerve, thereby producing less of an impact on diaphragmatic function.⁵ Selective suprascapular blocks have shown promise for shoulder arthroscopy when compared with placebo or intraarticular injection.^6–8 We report on a novel case of a patient with history of chronic pain undergoing a bilateral shoulder hemiarthroplasty with analgesia augmented by bilateral selective suprascapular perineural catheters.

CASE DESCRIPTION

A 52-year-old otherwise healthy woman presented for a bilateral shoulder hemiarthroplasty. She had a history of potential alcohol withdrawal seizures leading to falls and chronic bilateral shoulder dislocations with proximal humeral fractures. Preoperatively, she had decreased range of motion of each shoulder. Her resting pain on an 11-point numerical rating scale (NRS) was 4 of 10 in each shoulder for which she used 20 to 30 mg oxycodone daily.

Given her baseline pain and chronic opioid use, we discussed a regional technique to enhance postoperative analgesia with the patient and surgical team. Bilateral suprascapular catheters were chosen to minimize impact on respiratory mechanics while focusing analgesia to the planned surgical site. Baseline forced vital capacity (FVC) was measured using spirometry (MicroPlus Spirometer, MicroDirect, Lewiston, ME) with the patient sitting, as an average of 3 values. Baseline diaphragmatic excursion was measured using a high-frequency linear ultrasound probe (M-Turbo, SonoSite, Bothell, WA) with the patient supine. All subsequent measurements of FVC and diaphragmatic excursion were taken by the same operators with the patient in identical positions.

To perform the blocks, the patient was placed in a semirecumbent position at 30°. Before block placement, supplemental oxygen was delivered (6 L/min) through facemask, and sedation was achieved with 2 mg IV midazolam and 50 μg IV fentanyl. After identifying the brachial plexus adjacent to the subclavian artery at the supraclavicular level using a high-frequency linear transducer, the suprascapular nerve was isolated from the brachial plexus because it branched from the superior trunk. The suprascapular nerve was traced laterally by rotating the transducer perpendicular to the clavicle.⁹ A 17-gauge Tuohy needle and 19-gauge catheter (Flex-Tip Plus, Arrow International, Reading, PA) were inserted posterior to the probe and advanced anterior/medially in-plane until adjacent and just deep to the suprascapular nerve. After 5 mL 1.5% mepivacaine was given, the catheter was threaded 1–2 cm to maintain catheter tip-to-suprascapular nerve approximation. Once the needle was removed, an additional 5 mL of mepivacaine administered through the catheter confirmed appropriate tip position. The catheter was then secured with 2-octylcyanoacrylate (Dermabond, Ethicon Inc, Somerville, NJ) and a sterile occlusive dressing (Opsite IV3000, Simth & Nephew, San Antonio, TX). This sequence was repeated on the left. The development of first and second digit numbness confirmed onset of the blocks. A continuous 0.2% ropivacaine infusion set to 3 mL/h was attached to each perineural catheter and begun before proceeding to the operating room.

Intraoperatively, the patient received 250 μg IV fentanyl and 2 mg IV hydromorphone throughout the course of an uneventful general endotracheal anesthetic. She was extubated without incident before being transferred to the postanesthesia care unit in a stable condition after 3 hours and 37 minutes of surgical procedure time. Ropivacaine infusion rates were increased to 5 mL per hour because postoperative NRS pain values were 7 to 8 in either shoulder. This infusion rate was maintained through the remainder of the hospitalization.

FVC and diaphragmatic excursion were measured in postanesthesia care unit, on the evening of the operative day, and the mornings of postoperative days (PODs) 1 and 2. Over the duration of the infusions, the average FVC reduction was 23%. With the exception of POD1, diaphragmatic excursion remained at baseline throughout the hospitalization.  Subjective dyspnea or episodes of hypoxemia were absent throughout the hospitalization. Pain assessments were performed by nursing staff every 4 hours. Our patient’s mean reported NRS values with SD were 4.5 ± 0.5 on POD0, 6.2 ± 1.5 on POD1, 5.8 ± 1.2 on POD2, and 5.8 ± 0.8 on POD3. In addition to the perineural infusions, the patient was offered 10 to 20 mg oxycodone every 3 hours as needed. On POD 0, 1, and 2, the patient received 28, 62, and 48 mg of IV morphine equivalents, respectively.

She was discharged to a rehabilitation facility on the morning of POD3. Ropivacaine infusions were continued until discharge, at which point the perineural catheters were removed.

DISCUSSION

This case suggests that bilateral continuous suprascapular blocks are a feasible option for bilateral shoulder arthroplasty for postoperative analgesia when used in conjunction with traditional opioid-based pain management.

The 23% reduction in FVC our patient experienced is equivalent to the minimum of the range of reductions reported for unilateral interscalene infusions. With the exception of the 50% FVC reduction POD1, which may be partially attributable to normal postoperative variation related to atelectasis, our patient’s FVC was maintained within 13.5% of her baseline. By contrast, unilateral interscalene block reduces FVC between 25% and 40%.^10–13 For patients with severe underlying lung disease, this impairment can lead to hypoxemia, causing many anesthesia providers to consider pulmonary disease as a relative contraindication to interscalene brachial plexus analgesia.¹⁴ Studies aiming to eliminate this side effect have failed to identify a means to reliably provide continuous shoulder analgesia while consistently avoiding diaphragmatic paresis.¹⁵

Few cases exist documenting bilateral brachial plexus analgesia. In the available cases, practitioners have attempted to block the brachial plexus distally in the hopes of reducing phrenic nerve involvement.¹⁶ Still fewer reports have described bilateral perineural blocks that are considered effective for shoulder analgesia. One case of bilateral interscalene catheters did report their blocks’ effect on respiratory mechanics and found that this approach created a 60% decrease in FVC.¹⁷ Although their patient remarkably did not experience dyspnea or clinically significant hypoxemia, any additional insult may not have been well tolerated.

There are significant limitations impacting the interpretation of our patient’s analgesic benefit from the suprascapular nerve catheters. First, there was no confirmation of block onset apart from the development of digit numbness. As the suprascapular nerve supplies primary afferents to the shoulder joint and surrounding rotator cuff muscles, sensory distribution testing may be unreliable. Testing of selective suprascapular nerve block would ideally involve motor strength assessments of the infraspinatus and supraspinatus muscles, which was not feasible with our patient. Second, assessing the opioid sparing effect of the blocks is difficult in an individual patient, particularly one with a history of chronic opioid use. Currently, data are not available on postoperative analgesic use after shoulder arthroplasty with continuous suprascapular analgesia. Context for our patient’s experience is provided by a study from Ilfeld et al investigating continuous interscalene analgesia for unilateral shoulder arthroplasty. In this trial, opioid consumption in the interscalene group compared favorably with the placebo group, with an average of 7 vs 26 mg IV morphine equivalents in 24 hours.² This study notably excluded patients with chronic pain or opioid use. Patients with chronic opioid use may have perioperative requirements 3 times that of their opioid naïve counterparts.¹⁸,¹⁹ We believe that the 24-hour average of 46 mg IV morphine equivalents used by our patient is a significant improvement compared with the 78 mg that may be expected without a regional intervention. Considering that our patient underwent bilateral arthroplasty, the analgesic benefit may have been more significant still. The fact that her average NRS value remained within 2 points of her baseline is encouraging but difficult to interpret in light of the concurrent opioid administration.

Finally, there also may have been limitations to the optimization of our patient’s analgesic regimen. It is not known what the optimal infusion rate is for a selective suprascapular brachial plexus catheter. We chose an infusion rate of 5 mL/h to limit local anesthetic spread to the phrenic nerve. Greater infusion rates not only may have reduced pain and opioid consumption, but may also have compromised lung function further. Also, the addition of an axillary nerve block may have further improved our patient’s analgesia and opioid consumption with minimal effect on pulmonary function.⁸,²⁰

In conclusion, bilateral suprascapular continuous nerve blocks may minimize perioperative lung dysfunction, likely by limiting phrenic nerve paralysis. This continuous nerve block technique has the potential to reduce pain and opioid consumption after shoulder surgery. For patients with severe respiratory comorbidities undergoing shoulder surgery, whether unilateral or bilateral, this benefit may make continuous suprascapular analgesia a favorable option. Future randomized, controlled trials are required to support this conclusion.

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