CORRESPONDENCE |
Migration of interscalene catheter—not proven
* E-mail: awhg{at}btinternet.comEditor—We read with interest a recent Case Report in which the authors claim to document the migration of an interscalene catheter from the brachial plexus to the pleural cavity.1 Although the authors provide CT scan images to demonstrate that the tip of the catheter eventually achieved an intrapleural position, they provide no conclusive evidence that the catheter was not initially placed in this position, that is, they do not prove that migration occurred. The proof that they claim is that, having placed the catheter and injected bupivacaine 0.25% (20 ml) down it, and after shoulder manipulation had been performed under general anaesthesia, the patient awoke with ‘residual anaesthesia’ and did not require additional analgesia before transfer to the ward, although they accept that ‘no formal sensory (or) motor assessment’ was performed at this time. They therefore depend for their proof of migration upon the assumption that intrapleural local anaesthetic cannot produce brachial plexus analgesia. Unfortunately, this is not the case as tissue planes in the body do not act as absolute barriers to the diffusion of local anaesthetic drugs. It is therefore perfectly possible for local anaesthetic injected into the pleural space, particularly at the apex of the lung where the distance between the pleura and the brachial plexus is very short indeed, to spread to provide regional analgesia, although it is unlikely that it would reach the plexus in such large quantities as to produce anaesthesia.
References supporting our contention exist within the literature. Intrapleural analgesia can be used to treat pain originating from the brachial plexus2 and intrapleural local anaesthetic can produce brachial plexus blockade, whether the drug gets to this position deliberately3 or accidentally.4 No doubt the authors will respond to our assertions by questioning why the first postoperative top-up down the catheter produced shoulder analgesia while the second top-up produced chest wall analgesia. It is reasonable to assert that variations in patient position, drug mass, injectate volume and speed of injection may well affect the distribution of the local anaesthetic to produce different effects.
In addition to ‘guilty’ and ‘not guilty’, the Scottish legal system has access to a third verdict: ‘not proven’. It is our view that the authors' claims of catheter migration are ‘not proven’. Indeed, it is our opinion that the catheter was placed in the pleural cavity before the surgical procedure and did not migrate at all. This is perhaps supported by the authors' admission that they provoked contractions in the triceps muscle (nerve root supply: C7 and C8, i.e. lower to mid-plexus) rather than the more usual deltoid or biceps muscles (nerve root supply: C5 and C6, i.e. upper plexus); the needle over which the sheath was passed was therefore already in the lower reaches of the plexus and near the apex of the lung before 6 cm of catheter were passed beyond its tip.
London, UK
* E-mail: alain.borgeat{at}balgrist.ch (originally eletter)
Editor—We read with interest the article describing a case of delayed intrapleural migration of an interscalene catheter.1 The authors explained the occurrence of interpleural location of the interscalene catheter by a delayed catheter migration. Perineural catheter migration is a very rare and probably overstated event. We think in the present case the catheter was from the beginning very close to—or partly in—the pleura as shown by the CT reconstruction. This was not recognized by the authors for the following reasons. The effects of the first bolus [bupivacaine 0.25% (20 ml)] were unfortunately not checked and the patient had general anaesthesia (including strong opioids and muscular relaxant), which has masked to some extent an incomplete interscalene block. Despite the presence of some residual block over the shoulder in the recovery room, there is no description of a fully efficient interscalene block. The presence of some pain at this time argues against a correctly placed interscalene block. Moreover, the volume needed to control the pain had to be subsequently increased until chest wall numbness became evident. The increased volume of local anaesthetics was the most likely reason to make pleural analgesia visible, a secondary migration seems very doubtful. In fact, this case represents most likely a postponed diagnosis of an incorrectly placed interscalene catheter. This case is similar to the one described by Souron and colleagues.5 The occurrence of this complication emphasized the recommendation not to thread the catheter more than 2–3 cm past the tip of the stimulating needle. Threading the catheter more than that is unnecessary, it increases the risks of complication and jeopardizes the success of the block.
Zurich, Switzerland
* E-mail: carolinejenkins{at}cuhk.edu.hk
Editor—We appreciate the comments regarding our case report.1 However, we feel strongly that this was a true migration of the catheter. It is not possible to ever prove that the catheter migrated, but we feel that we have evidence to back up our claim.
In retrospect we should have formally tested both the motor and sensory block in this patient, but in our busy clinical practice, we, as many others, often do not formally test unless there is a problem with the block. We monitored the block in the recovery room and were happy that the patient had anaesthesia over the shoulder. He complained of a ‘numb’ shoulder and therefore we did not feel the requirement for any further testing.
Patients have been reported to develop brachial plexus analgesia with an intrapleural block3 but it remains that the block changed between the first two injections of local anaesthetic and the third. We appreciate that different patient positioning, drug mass, injectate volume and patient position can give rise to a different block but the same doctor administered the top up injections on the second and third occasion. The patient was in the same position and the only difference was an additional 5 ml of lidocaine. It is important to recognize that the patient noticed a very different feeling to that of the previous day and morning and alerted the nurses on the ward to this.
As for the use of the triceps muscle contraction, this has been previously well described for localization of the brachial plexus6 so we do not feel that this shows any further proof that this was not a migration. We believe that this was a true migration of a brachial plexus catheter and would like to continue to warn people of this potentially serious complication.
References
1 Jenkins CR, Karmakar MK. An unusual complication of interscalene brachial plexus catheterization: delayed catheter migration. Br J Anaesth 2005; 95: 535–7
2 Myers DP, Lema MJ, de Leon-Casasola OA, Bacon DR. Interpleural analgesia for the treatment of severe cancer pain in terminally ill patients. J Pain Symptom Manage 1993; 8: 505–10[CrossRef][Web of Science][Medline]
3 Fernandez Munoz J. Brachial plexus block as a complication of interpleural analgesia. Rev Esp Anestesiol Reanim 1991; 38: 202–3[Medline]
4 Manara AR. Brachial plexus block—unilateral thoraco-abdominal blockade following the supraclavicular approach. Anaesthesia 1987; 42: 757–9[Medline]
5 Souron V, Reiland Y, De Traverse A, Delaunay L, Lafosse L. Interpleural migration of an interscalene catheter. Anesth Analg 2003; 97: 1200–1
6 Borgeat A, Ekatodramis G, Kalberer F, Benz C. Acute and nonacute complications associated with interscalene block and shoulder surgery: a prospective study. Anesthesiology 2001; 95: 875–80[CrossRef][Web of Science][Medline]
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