Where now for thoracic paravertebral blockade?

In this issue of Anaesthesia, Luyet et al. report an elegant study examining the reliability of the classical landmark approach to paravertebral blockade (PVB) [1]. While this report will no doubt be of interest to thoracic anaesthetists, we urge all general anaesthetists not to be too hasty in turning the page, as this work has broader application. In 2006, Exadaktylos et al. published a retrospective study analysing the medical records of 129 consecutive patients undergoing surgery for breast cancer. The findings suggested that paravertebral anaesthesia and analgesia for breast cancer surgery may reduce the risk of tumour recurrence or metastasis [2]. While confirmation from prospective randomised controlled trials is awaited, the volume of in vitro data to support such a hypothesis is growing [3]. Should such an approach be convincingly demonstrated to confer survival benefits, the delivery of effective regional anaesthesia and analgesia will become an established standard of care in cancer surgery. This increases the drive to develop a safe, effective and reliable technique for unilateral regional blockade. In thoracic surgery, debate surrounding the ideal analgesic technique for thoracotomy has intensified in recent years with the suggestion that PVB has a better side-effect profile and has been associated with a reduction in complications compared with thoracic epidural analgesia (TEA) [4, 5]. The current practice of thoracic anaesthesia in the UK is represented by an approximately 2:1 split in favour of TEA over PVB [6], a split that has remained consistent over several years, perhaps suggesting that to many, either the reliability or the benefits of PVB over TEA are yet to be sufficiently proven to change practice. Luyet et al. report an observational study aiming to explore the association between the location of paravertebral catheters placed using the classical landmark technique, the distribution of contrast dye delivered through the catheter, and the extent of subsequent somatic block [1]. In doing so, the authors encounter one of the many methodological difficulties that challenges studies of this sort: what constitutes failure of regional anaesthetic blockade? In one recent, high-profile, meta-analysis comparing the analgesic efficacy and side effects of PVB versus TEA for thoracotomy, the included studies defined failed technique as anything from failure to catheterise the epidural space and inadequate analgesia (technique failure) to unavailability of an infusion pump (system failure) [4]. When appraising the regional anaesthetic literature, clinicians must pay careful attention to definitions of failure and decide what constitutes a clinically meaningful failure in their practice. It has been said that regional anaesthesia always works provided you put the right dose, of the right drug, in the right place [7]. The pertinent question is: how do you deliver local anaesthetic to the right place within the paravertebral space? It has been demonstrated that the analgesic effect of single-shot PVB lasts approximately six hours, and that as such, in order to provide prolonged postoperative analgesia via PVB, a catheter technique is required [8]. In Luyet et al.s study, the authors attempted to place PVB catheters by a percutaneous landmark technique in 31 patients. In one patient, difficulties were encountered during paravertebral catheter placement, leading the investigators to switch to an ultrasound-guided approach (undoubtedly a case of technique failure). The authors define the spread of contrast dye within the paravertebral space either close to the intervertebral neural foramen, extrapleural laterally at the level of the ribs, extrapleurally at the level of the vertebral bodies or anterior to the vertebral bodies, as a successful radiological endpoint; the right place. In nine out of 30 catheters, dye was not seen in these locations. Including the failed catheterisation,