Interscalene catheters ‐ should we give them the cold shoulder?

The benefits of single-shot interscalene brachial plexus blockade (SSIB) for patients undergoing shoulder surgery are well established 1. These blocks have a consistently high success rate, the techniques are well described 2-4 and are suitable for the vast majority of patients presenting for shoulder surgery. Single-shot blocks can provide excellent analgesia for 11-14 hours, which mitigates the severe postoperative pain that can follow shoulder surgery. In the UK, these patients are commonly discharged home on the day of surgery 5, 6. In this issue of Anaesthesia, Fredrickson et al. describe the use of continuous interscalene analgesia at home in a large number of patients following shoulder surgery 7. They argue that continuous interscalene infusion following shoulder surgery should be the gold standard for pain relief in these patients 8 and believe that their outcome data will persuade others that this technique is safe and effective. But is this the best way to manage pain after shoulder surgery? The authors correctly point out that, at the moment, ambulatory catheter techniques for shoulder surgery are not widely employed, and this may be related to logistical and safety concerns. This seems to be confirmed by the fact that there are few published research papers that have included more than twenty patients 9. Fredrickson et al. should therefore be commended for completing the largest prospective observational study so far that has investigated the safety of such an analgesic regimen. In approximately 1500 patients they demonstrated the use of pumps, taken home by the patient, catheters, removed by the patient, and low pain scores that we should all be striving for. There were few complications related to the infusion (2% technical and 8% leakage issues) and not many patients were lost to follow up (3%). There were low rates of catheter dislodgement (1.5%), no catastrophic events and apparently no patients returned to hospital because of pain or other problems related to the infusion. Data was collected retrospectively by a telephone call made five to seven days postoperatively by a research nurse. Overall reported pain scores were low, although retrospective reporting can be problematic 10. This is demonstrated by the number of patients complaining of dyspnoea during the infusion at home, which was surprisingly high at 27% and was in contrast to the 0.7% of patients who experienced this symptom immediately postoperatively. As anaesthetists, we are interested in pain and dyspnoea, but patients often have different concerns, and they may find numbness just as unpleasant as pain, thus influencing their choice of analgesic technique. It would have been interesting to learn how patients perceived their recovery with continuous interscalene infusion by using a tool such as the Quality of Recovery (QoR) score 11, 12, or to ask the patient if they would be willing to undergo the procedure again. When Fredrickson previously compared SSIB with continuous infusion for minor arthroscopic shoulder surgery, they found no significant difference in patient satisfaction, despite improved pain scores during the infusion 13. Some preliminary work utilising the QoR-15 score to analyse patient-centred assessment of recovery in day surgery shoulder arthroscopy patients has indicated that patients display good recovery from SSIB in the ambulatory setting, without rebound pain at 48 hours (http://epostersonline.com/asraspring2015/node/192). To the best of our knowledge, few specialists in the UK are inserting interscalene catheters for perineural infusions of local anaesthetic at home. Perineural catheter insertion is a highly skilled procedure that requires advanced training, time and resources. Fredrickson et al. are all extremely experienced and skilled in this procedure, as evidenced by the low rates of intervention required postoperatively as well as the low pain scores. It is unlikely that all consultant anaesthetists in the UK will have the opportunity to achieve or maintain this level of skill, and the expertise may not be sufficiently widespread within a single centre to run a sustainable service that can be offered consistently to patients. Without a reliable service, patients would be unsure what to expect on the day of surgery and may refuse to undergo an unfamiliar technique. Fredrickson and his four colleagues were personally responsible for managing the interscalene catheters for the duration of the infusion and offered 24-hour availability by mobile phone. This level of involvement requires enthusiasts with a high degree of dedication to staff this service, or delegation of troubleshooting to the hospital's on-call anaesthetic service. This in turn requires training of all consultant and trainee anaesthetists in the hospital if patients are to receive an excellent service. The shift patterns and rapid turnover of trainees in the NHS make educating anaesthetists a huge ongoing task and illustrate the difficulties we may have in replicating Fredrickson's enviable set-up. Clearly a robust infrastructure is required before rolling out a catheter-at-home service. In contrast to practice in the UK, where the majority of patients having shoulder surgery are discharged on the day of surgery 6, the majority of patients in Fredrickson's study were discharged on the day after surgery. No data was presented informing us of any anaesthetic interventions required overnight in hospital before patient discharge the next day. If a large number of patients require intervention or adjustment to the catheter on the first night, this makes same-day discharge with a nerve catheter in situ less feasible. Fredrickson et al. did not comment on rates of catheter dislocation; the authors have previously commented that they do not believe that the phenomenon of catheter dislocation exists 8. Nevertheless, nerve catheters may not always lie in the correct location, as demonstrated by Yanovski et al. 14 when a patient died following a top-up of an interscalene catheter. The catheter was found to lie intrathecally, dramatically illustrating the potential for catastrophic complications with displaced (or misplaced) catheters. Marhofer et al. showed a 5% incidence of interscalene catheter dislocation five hours after insertion in volunteers, and that the likelihood of dislocation increased with time 15. This study excluded participants with a BMI >30 kg.m−2, who make up an increasing proportion of our workload. Another case report describes the migration of a catheter into the intrapleural space 16. How comfortable are we sending patients home with these potential risks, no matter how small? The neurological risks of regional anaesthesia are familiar to most anaesthetists. Patients in the Fredrickson et al. study reported neurological symptoms broadly in line with other published figures 17, 18. Despite this being described as a safety study, the authors state that ‘neurological data was not an outcome of primary interest, thus no attempt was made to pinpoint the primary aetiology of symptoms’. Long-lasting neurological sequelae are of interest to any anaesthetist undertaking regional anaesthesia, and it was a shame that the opportunity was missed to collect more data on these patients and have these symptoms formally investigated. This would have generated useful data on the true incidence of neurological complications following this technique. The introduction of an ambulatory nerve catheter service will require training, consumables and staff. To justify the service financially requires either a safety imperative or the potential to reduce other costs to the organisation. In practice, this means reducing the length of inpatient stay or the numbers of patients requiring re-admission to hospital for uncontrolled pain. As most patients are currently discharged on the day of surgery with multimodal oral analgesia, and are not (to our knowledge) consuming health resources elsewhere due to pain, it may be difficult to make the financial case for an ambulatory catheter service for the majority of patients undergoing shoulder surgery. In addition, although the pressure to reduce time spent in the anaesthetic room can be overcome with use of a ‘block room’ service 19, this requires hospital space, staffing and expertise along with a high enough patient throughput to make it financially viable. In the UK, a multimodal approach to analgesia for shoulder surgery includes SSIB to allow same day discharge in the majority of cases. SSIB can provide reliable analgesia for 11-14 hours, which can be prolonged with the use of adjuncts such as α2-adrenergic receptor agonists and dexamethasone, but the non-licensed use of these drugs may restrict their uptake 20. Significantly, a recent article reported similar prolongation of analgesia of at least five hours with a single dose of intravenous dexamethasone compared with perineural dexamethasone 5. The development of sustained-release formulations such as liposomal bupivacaine may offer the potential to provide long-lasting analgesia (72 hours) following a single administration, which may eliminate the need for catheter-based techniques 21. However, this preparation is not currently licensed in Europe, and in the US is licensed for wound infiltration only. Neosaxitoxin, a phycotoxin that reversibly blocks voltage-gated sodium channels at the neuronal level, has shown some success in small trials, providing analgesic activity for approximately 24 hours 22. However its development is at an early stage and further studies are required. Interscalene brachial plexus block is associated with phrenic nerve palsy and injury to the dorsal scapular and long thoracic nerves 23, 24. The superior trunk block targets the C5 and C6 components of the brachial plexus more distally than the classical interscalene block, after they unite into the superior trunk before the branching of the suprascapular nerve 25. Performing a nerve block at this level can provide adequate analgesia for shoulder surgery and may be less likely to result in phrenic nerve palsy. Although not commonly performed, the superior trunk block could provide a safer target for catheter placement because the locations of the needle and catheter tip should be easily visible when using ultrasound. A recent letter by Lin et al. described a single puncture approach to block both the supraclavicular nerves and the superior trunk of the brachial plexus 26, however much more work is required to determine the safety and efficacy of these blocks before they can be recommended. Most patients presenting for routine shoulder surgery are discharged safely with single-shot blocks and despite the excellent results shown by Fredrickson et al., there is currently no convincing evidence that we should change our practice for these patients. We should continue to select our patients carefully and consider continuous infusions on a case-by-case basis. Those who wish to develop an ambulatory catheter service will need to be enthusiastic and hard working to overcome the likely organisational, financial and safety issues. For the time being, we will not be setting up an ambulatory catheter service in our institution. We don't believe those hospitals with an existing service should stop offering it, but we cannot recommend other hospitals setting up catheter services until regional anaesthesia enthusiasts have built up the level of knowledge and skill in the wider anaesthesia community to allow us to offer this service safely. No external funding and no competing interests declared.

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