◊ BACKGROUND AND OBJECTIVES:
Up to 70% of patients report moderate to severe pain after shoulder surgery, which can compromise early rehabilitation and functional recuperation. Postoperative shoulder pain control is improved with both interscalene block and intra-articular local anesthetic injection. The present study hypothesized that perioperative interscalene analgesia would offer pain control superior to perioperative intra-articular local anesthetics over the first 24 hours after surgery.
◊ METHODS:
Sixty patients undergoing shoulder surgery were randomly assigned to 1 of 2 groups: group IS had interscalene block with catheter installation, while group IA received intra-articular local anesthetic, also with catheter installation. All patients received 3 local anesthetic injections: 0.25 mL/kg of 2% lidocaine with epinephrine 2.5 microg/mL immediately before and after surgery, and 0.25 mL/kg of 0.5% bupivacaine with epinephrine 2.5 microg/mL 1 hour after the end of surgery, after which the catheters were removed, and no further local anesthetics were administered. Postoperative pain at rest was evaluated in the postanesthesia care unit (PACU), 3 hours, 6 hours and 24 hours after surgery. The area under the 24 hour pain over time curve was calculated. Hydromorphone consumption in the PACU and over 24 hours was recorded.
◊ RESULTS:
Pain scores (IS: 0.4 +/- 2 vs. IA: 4 +/- 3, P < .0001) and opioid consumption (IS: 0.7 mg +/- 1.4 vs. IA: 1.5 mg +/- 1.2, P = .02) were significantly higher in the PACU for group IA. However, neither the mean pain scores over the first day after surgery (IS: 5 +/- 2 vs. IA: 5 +/- 3; P = .4) nor 24-hour opioid consumption (IS: 4.4 mg +/- 2.8 vs. IA: 4.2 mg +/- 2.6; P = .4) were significantly higher in group IA.
◊ CONCLUSIONS:
PACU measurements of immediate postoperative pain and narcotic consumption favor perioperative interscalene analgesia over intra-articular analgesia. This benefit does not translate into lower overall pain for the first 24 hours after surgery.
◊ Reviewed by J. Raeder, MD, PhD
Chairman of Clinical Ambulatory anaesthesia / Professor in Anaesthesiology,
Dept. of Anaesthesia,
Oslo University Hospital, Oslo, Norway
This is a sound report on a study with 2x30 patients receiving two perioperative injections of lidocaine with epinephrine and a 1 hr postoperative injection of bupivacaine+epinephrine, either as interscalene block (IS) or intra-articularly (IA). The interscalene block provided better analgesia and resulted in fewer opioid consumption in the post-operative care unit, but during the rest of the first 24 hrs, results were similar for both treatments.
The reader will question whether these results are relevant in clinical practice for the selection of patients and procedures as well as for the total “package” of perioperative measures.
Study patients seem to be a mix of different types of elective shoulder surgery (excluding drains) with variations in age, gender and of in- and outpatients. Although patients with chronic preoperative pain were excluded, we do not know if those with acute, shortlasting preoperative pain were allowed to participate. Such patients will usually need stronger analgesia. The same may be true for female patients who were two times more frequent in the IA group.
A mixed variety of shoulder procedures may have different requirements for analgesia per se, both in terms of total amounts of analgesics and in terms of the anatomical structures involved. In the present study, interventions ranged from diagnostic arthroscopy to shoulder prosthesis. This may have added to the variation between the two groups. Furthermore, as arthroscopy pain involves fewer extra-articular structures than open shoulder surgery, for the latter, analgesia by only intra articular injections may be expected to work less. An interscalene block provides much better sensory and analgesic effects on extra-articular structures. It would have been of interest if the initial inferiority of the IA method was due to less analgesia in the open surgical patients only or in all patients.
What about the total “package” of anaesthestic measures to ensure optimal postoperative analgesia with both methods? In both groups, there were three injections, pre-, peri- and postoperatively which is optimal in terms of a pre-emptive effect as demonstrated for loco-regional anaesthesia. The use of lidocaine in the beginning and of bupivacaine at the end is also reasonable in order to have both fast onset and prolonged duration. Benefits of adding opioids to local anaesthesia have been demonstrated for chronic inflammation of peripheral tissue only and are probably not applicable in this context. Of further benefit could have been to add an NSAID or coxib, either to the local anaesthetic solution, or (less controversially) by systemic dosing. A further improvement, especially in the IA group would have been to use local anaesthesia infiltration for all wounds and skin incisions and to take more benefit from having a catheter in place, by delaying the last injection until PACU discharge, or by a fourth injection for inpatients in the evening. Unfortunately, we do not know how long the patient stayed in PACU, or how many patients were staying overnight, in order to evaluate the potential of this measure.
Authors mentioned that some patients had a dislocation of the catheter. While it is honest to include this information, it may have been of interest to report results for the subgroup with optimal catheter placement throughout the study, because this is the goal to strive for. Would more success in securing all catheters change overall results?
Are data interpreted correctly? Surely, statistical methods are adequate, but looking at figure 1 the statistical power of only having 2 x 30 patients with a large spread in types of surgery may be questioned. While the NPS in the IA group at PACU discharge is more than twice the score of the IS group, it is still not significant. Looking at the figure, we may suspect that the advantage of the IS method lasts for 3 hrs postoperatively, and not just at the PACU admittance. Also according to figure 1, overall pain seems to increase throughout the first 24 hrs despite of opioid rescue and an expected effect of bupivacaine for at least 6 hrs. This may be linked to catheter displacement, but also suggests that another dosing regimen (timing, volume and mg bupivacaine) for the third injection would have been beneficial.
Although the IA method was less successful in this report, the authors point out that it is simple and do not involve motor paralyses or extensive numbness. Thus, this method may still be preferable for artroscopic procedures, especially if the method is enforced with bupivaciane injections into all wounds and concomitant treatment with oral NSAIDs. We will certainly need further studies to cofirm this; however, the present study has raised a lot of interesting questions!
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