Tuesday, April 11, 2017

Interscalene block - what is it's value?

Randomized Controlled Trial of Interscalene Block Compared with Injectable Liposomal Bupivacaine in Shoulder Arthroplasty

These authors list the shortcomings of interscalene brachial plexus block as technical failure and rebound pain. They could also have added to these shortcomings (1) increase cost, (2) increase time, (3) increased rate of complications, (4) risk of phrenic nerve palsy (5) patient frustration with having a 'dead arm' until the block wears off, and (6) inability to do a post op neurological exam.

They randomized patients undergoing primary shoulder arthroplasty to either interscalene brachial plexus block or intraoperative soft-tissue infiltration of bupivacaine liposome injectable suspension.

They found that the mean total postoperative narcotic consumption over 24 hours after the surgical procedure was 14.8 ± 11.3 morphine equivalent units in the block group compared with 14.4 ± 16.8 morphine equivalent units in the suspension group (p = 0.849). The mean VAS pain score was significantly lower in the blockade group than in the suspension group at 0 hours postoperatively (0.8 ± 2.2 compared with 3.3 ± 2.7 points; p < 0.001) and at 8 hours postoperatively (1.4 ± 2.4 compared with 3.2 ± 2.2 points; p < 0.001), but it was not significantly different at 16 hours postoperatively (4.3 ± 2.8 compared with 3.8 ± 2.4 points; p = 0.348). The VAS pain scores were significantly higher (p = 0.021) in the block group (4.9 ± 2.7 points) compared with the suspension group (3.9 ± 2.3 points) at 24 hours postoperatively. 

What is particularly concerning about the VAS pain scores for interscalene block is that at 24 hours the pain was worse than it was preoperatively as shown in this graph




The costs of these two modalities were not available.

They concluded that  interscalene brachial plexus block provided improved pain scores for the first 8 hours after the surgical procedure, pain scores were worse at 24 hours. The optimal postoperative pain regimen for shoulder arthroplasty and the cost-effectiveness of analgesic techniques require further investigation.

Comment: In our primary and revision arthroplasty practice we use neither nerve blocks or the liposomal bupivacaine. Instead we use patient controlled analgesia for the first few hours after surgery and transition to oral analgesics the evening of surgery. With this protocol patients are able to comfortably start continuous passive motion and assisted range of motion exercises immediately after surgery in the recovery room. This is a very cost effective approach, avoiding the increased cost of nerve blocks or the liposomal bupivacaine as well as the time, complications, technical failure, and rebound pain of nerve blocks. Patient satisfaction is high, even among those taking substantial narcotics preoperatively.

Readers may wish to review a similar study:

Liposomal bupivacaine versus interscalene nerve block for pain control after shoulder arthroplasty: a prospective randomized trial.

These authors studied 57 patients undergoing primary shoulder arthroplasty randomized to receive either intraoperative local infiltration of local liposomal bupivacaine (LB) 20 mL bupivacaine/20 mL saline) or preoperative interscalene nerve block (INB).

 Outcomes showed a significant increase in pain in the LB group between 0 and 8 hours postoperatively (mean [standard deviation] 5.3 [2.2] vs. 2.5 [3.0]; P = .001). 

A significant increase in intravenous morphine equivalents was found in the INB group at 13 to 16 hours (mean [standard deviation] 1.2 [0.9] vs. 0.6 [0.7]; P = .01). No significant differences were found in any variable after postoperative day 0 between the 2 groups.

They concluded that an increase in early postoperative pain on the day of surgery was found with LB, whereas the INB group required more narcotics at the end of the day.

In their discussion, the authors review the safety and complication rates of INB. Weber and Jain evaluated the efficacy of INB in a review of 218 patients. They found that 13% of INBs in their study failed, and 5% of their patients had an abnormal neurologic response the day after surgery. Misamore et al demonstrated that 16% of patients undergoing INB experience immediate postoperative block side effects, with 4.4% of patients experiencing persistent neurologic complications. This study displayed similar results, with 3% of patients experiencing a persistent neurologic complication. A study by Fredrickson and Price suggested that an increase in postoperative motor blockade can be experienced with INB and is associated with a reduction in patient  satisfaction.These findings along with the desire for earlymobilization of the operative extremity suggest the utility of an alternative method for pain control in shoulder arthroplasty.

Evaluating the pharmacokinetics of INB, Busch et al found that the time of pain onset after single-injection ropivacaine INB was 10 hours. Weber and Jain similarly evaluated the efficacy of lidocaine and bupivacaine INB and found  that the mean duration of action of the block was 9 hours. This study demonstrated that INB had similar results, with  pain levels quickly rising after 8 hours postoperatively. Goon et al used a single injection of ropivacaine (25 mL 0.375%)  INB in shoulder arthroplasty patients and found the block’s  effects to last on average 18 hours. This study found similar findings with a peak in pain level seen 21 to 24 hours postoperatively  in the INB group. Whereas INB was more effective  at controlling pain in the first 8 hours postoperatively, there  was a trend toward acute rebound pain at the end of POD 0 as the block’s effects declined. 

Comment: Again our reasons for avoiding interscaline blocks for shoulder arthroplasty include (1) desire for documentation of neurological status immediately after surgery, (2) wanting to avoid having a flail unprotected arm as we start immediate postoperative motion exercises, (3) eliminating the risk of block-related neurologic or pulmonary complications, (4) avoiding phrenic nerve paresis with the attendant respiratory compromise, (5) eliminating the inconvenience of a failed block, (6) reducing the cost associated with two different anesthetics (block + general), (7) avoiding the problem of acute rebound pain in the middle of the first postoperative night, and (8) the reluctance of some patients to have a needle placed in their neck.

See also