Stellate ganglion block for postoperative analgesia in patients with upper extremity orthopaedic injuries

We read with great interest the recent article by McDonnell et al. [1] and applaud their utilisation of stellate ganglion blockade for analgesia. We concur with their findings as they corroborate our own results [2, 3]. In 2005, we reported a series of seven patients in whom stellate ganglion block safely and significantly reduced postoperative pain after upper extremity orthopaedic surgery [3]. All patients demonstrated a rise in limb temperature, confirming sympathetic block, with preservation of motor strength and two-point discrimination ruling out any somatic block component that could contribute to the pain relief. It is well known that in physiological conditions, sympathetic outflow has no effect on nociceptor function and activity. Surgical insult may be the priming needed before the sympathetic nervous system can relay peri-operative pain [4]. The remarkable differences in McDonnell et al.’s series were the use of ultrasound guidance and the placement of the stellate ganglion block pre-operatively. In 2004, when we conducted our study, ultrasound guidance for nerve blocks was not mainstream practice. Historically, stellate ganglion block has been used to ameliorate sympathetic nervous system-mediated pain. Our series showed, for the first time, its efficacy in treating established postoperative somatic pain. If used pre-operatively, the presence of other confounders such as use of analgesics, the duration and nature of surgery and individual pain tolerance can cause remarkable variations in the level of postoperative pain, making it impossible to determine the severity of pain. We do not contest the pre-operative use of stellate ganglion block; however, its efficacy needs to be established in larger randomised studies. It can then be used for pre-emptive analgesia in the pre-operative period. A recent meta-analysis found only a single study with level-1B evidence and a handful of series with level-1C evidence on the use of stellate ganglion blocks [5]. This shows that although many authors have proved the effectiveness of stellate ganglion block, there is a paucity of high quality evidence. We share the views of Chambers and Smith who discussed McDonnell et al.’s series and cautioned against implementing stellate ganglion block for postoperative analgesia in routine practice, as the mechanism is not completely understood [6]. We have previously stressed that sympathetic pathways play an important role in peri-operative pain and need to be explored further by means of larger randomised, double-blind studies. Future studies should focus on elucidating interactions between autonomic and somatic afferent systems and may provide answers and newer tools for the management of peri-operative pain.