Ultrasound guidance for regional anaesthesia
Toronto, Canada
E-mail: colin.mccartney{at}utoronto.ca
Editor—As a proponent of ultrasound-guided regional anaesthesia, I enjoyed reading the excellent case series by Karmakar and colleagues.1 However, I have reservations about a number of the conclusions drawn in the accompanying editorial by Hopkins.2 I agree that the recent regional anaesthesia ultrasound literature has many studies that lack equipoise. However, this fact surely reinforces our responsibility to strive for the best quality ultrasound studies in order to properly answer the question of whether ultrasound techniques really do have significant advantages. This is because there are many existing and very successful users of other regional anaesthesia techniques that correctly demand the highest quality evidence before committing to the significant expense and inconvenience of training with new technology. Although I would agree with Professor Hopkins that almost all radiologists would support the use of ultrasound for certain interventional techniques, this opinion has been developed through studies that exist in the radiology literature comparing ultrasound with other techniques for biopsy.3 4 In addition, radiology studies conclude that ultrasound is but one technique among many that can help achieve a predefined endpoint and that the optimal combination of a number of endpoints can improve success.5
I also disagree that there are no inherent harmful effects of ultrasound guidance. Many of the newly developed ultrasound-guided approaches have significant potential for harm if the needle tip is not carefully visualized and followed during insertion. Superficial ultrasound techniques often use very different needle insertion points compared with traditional techniques where the needle insertion point and path has been carefully developed to avoid vital structures.6 If the needle tip is not clearly followed with ultrasound, significant potential for mishap can occur. With deeper blocks, local anaesthetic expansion can be difficult to appreciate using ultrasound and the usual precautions such as incremental injection and frequent aspiration remain very important. Inexperienced users of ultrasound can obtain a false sense of security and fail to continue to observe these precautions leading to potential for significant complications.
Until we have further evidence for the benefit of ultrasound-guided regional anaesthesia in enhancing success and reducing complications, it is premature to imply that ultrasound is a safer technique. We need to determine the ideal endpoint or combination of endpoints for different types of blocks. For many regional anaesthesia procedures, I believe, based on personal experience and reading the literature, that ultrasound will be the key component. However, until we have the best quality evidence to support this assumption we need to be very careful about making premature conclusions.
C. J. L. McCartney has received payment of honoraria by SonoSite Corporation.
Dundee, UK
E-mail: jaww{at}doctors.org.uk
Editor—Ultrasound guidance for regional anaesthesia is a very promising method, and there is much in the editorial from Hopkins2 that I agree with and support. However, the method must be investigated fully, not simply accepted as perfect as he proposes. Further, I would take issue with his third paragraph, one which I judge to be seriously incautious. To state, as he does, that a clinical aid will produce ‘successful nerve block with no complications’ is wildly over-optimistic, but to then state that ‘any deviation from this standard is an operator deficiency’ is an open invitation to the legal profession to pursue colleagues whose practice may otherwise be impeccable.
Almost any method can be highly successful in the hands of an enthusiastic expert, but the true test is how well it works in routine use. Those who, like me, have been involved in regional anaesthesia for more than three decades will remember that the introduction of nerve stimulators was supposed to eliminate block failure, but they did not, and the history of medicine as a whole is littered with the incautious introduction of ‘advances’ deemed too important for proper investigation, only for them to be shown, much later, to be less than advantageous. It is hard to see how the use of ultrasound could cause harm to patients, although it might engender excessive confidence and thus encourage incautious practice if not properly evaluated. Further, the equipment is expensive and justifying its cost will require the availability of high-quality evidence. Enthusiastic reports after use in what are really very small numbers of patients (all that we have to date) do not represent such evidence.
In regard to evidence, I do not accept that randomized controlled trials have no place in the evaluation of ultrasound for regional anaesthesia, although I agree that the incidence of complications is (or should be) too low for such comparison. The same might be true of block success rates, although I am not so sure, and properly designed and performed audit projects, albeit comprising hundreds of patients (large, but not unachievable, especially on a collaborative basis), should be capable of generating hard data which can be compared with standard figures. Then, and only then, can ultrasound be put forward as a gold standard, assuming that the data warrant it!
Bournemouth, UK
* E-mail: rrhh.bmc{at}btinternet.com
Editor—We read the recent editorial by Hopkins2 on ultrasound guidance for regional anaesthesia and would like to take issue with some of the comments and conclusions. Although accepting that it is difficult to perform large scale, randomized studies in this area, it is dangerous to draw such one-sided opinions in the absence of such studies.
Medicine is littered with technologies which were introduced because logic indicated a benefit, but long-term studies showed otherwise. Pulmonary artery catheters were one and in the field of obstetrics, which Hopkins uses as an example to further his argument, clinicians find themselves in a medico-legal minefield as a result of lack of clear evidence for some medical interventions. To imply that ultrasound should offer 100% success and 0% complications is optimistic in the extreme and to suggest that failure to meet these standards is down to ‘operator deficiency’ goes against one of the founding principles of risk management; we all err from perfection. Those of us who perform hundreds of regional blocks a year with a high success rate (the 95% that Hopkins quotes) with no major complications, efficiently and with a minimum of equipment need good arguments for changing their established practice. We would not consider ourselves to be either intransigent or in the minority, as Hopkins would have us believe.
We feel that ultrasound guidance will be a useful addition to the armamentarium of the anaesthetist practising regional anaesthesia, but to so strongly imply that those not using this method are medically negligent is a dangerous and unhelpful step.
Rotterdam, The Netherlands
E-mail: c.vanvelzen{at}sfg.nl
Editor—After reading the editorial by Hopkins,2 I have a few remarks. First, Hopkins states that he found only one paper,7 8 in children, that demonstrated an improved success, but then appears to recommend its use as a gold standard. Is it because he was sponsored by SonoSite? After all, the use of new technologies should be based on evidence. Why not in this case? If we accept this as fact then we are on the wrong path, this includes the BJA. I challenge the idea that ultrasound should be used always, as it is not good for our residents. They do not learn to use landmarks, nerve stimulation, and good clinical approach of the patients who rely on the expertise of the doctor. We also force hospitals with a smaller budget to invest in techniques which are not better than the ‘old’ techniques.
The presumed disadvantage of nerve stimulation that injection in the nerve sheath is dangerous might not be the truth as described by Bigeleisen.9 The last remark is based on Hopkins statement that more research and development is necessary in ultrasound-guided regional techniques. I suggest that more research is required to prove that ultrasound is better than nerve stimulation. If this is so, then it is time to re-evaluate the use of regional techniques assisted by nerve stimulation.
Leeds, UK
E-mail: p.m.hopkins{at}leeds.ac.uk
Editor—I am pleased that my editorial2 has generated debate of the status of ultrasound guidance in regional anaesthesia. I welcome the opportunity to respond to comments concerning the evidence base for the use of ultrasound, the relative contribution to block failure of a particular technique vs human deficiencies, and the motives behind my article.
In my editorial, I questioned the need for randomized controlled trials of ultrasound-guided vs other regional techniques. To varying degrees McCartney, van Velzen, Wildsmith, and Cornforth and Hargreaves would appear to believe that a randomized controlled comparison of ultrasound with other regional techniques is the only form of evidence that we should accept. But let us consider what makes a successful regional block. Can we not agree that this is placement of a needle adjacent to each of the relevant nerves and injection of sufficient local anaesthetic around them, while avoiding causing damage to nerves and other structures with the needle or injecting the local anaesthetic in the wrong place? To argue otherwise is to imply that there is some magical or mystical component to regional anaesthesia. I believe that there is sufficient evidence from experts in ultrasound-guided needle placement to inform us that this can be achieved with greater rates of success than even the most successful series of nerve blocks using nerve stimulator confirmation of needle placement. To ignore this substantial body of evidence for the accuracy of ultrasound-guided needle placement is akin to arguing that parachutes should not be used because their efficacy has not been demonstrated in a randomized controlled trial.10
The evidence for the accuracy of ultrasound-guided needle placement comes in the form of prospective trials, observational studies, and consensus statements in the radiology literature. McCartney cites, for example, a prospective study of 2403 imaging-guided (ultrasound or stereotactic) breast biopsies that demonstrated an accuracy of >99% using ultrasound.4 McCartney is wrong, however, in suggesting that Dillon and colleagues5 provide evidence that ‘the optimal combination of a number of endpoints can improve success’. This study compared ultrasound-guided breast biopsy with clinically or stereotactically guided biopsy. The success rate was significantly higher in the ultrasound group compared with the others and the authors comment on the advantage of real-time imaging using ultrasound. This study5 refers to one disadvantage of ultrasound in this context compared with stereotactic guidance, which concerns the inability to visualize breast biopsy sites that consist solely of calcified tissue using ultrasound: this is of no relevance to ultrasound-guided regional anaesthesia.
I enjoyed Professor Wildsmith's letter, but I did not state ‘a clinical aid (ultrasound) will produce’ successful nerve block with no complications. I did in fact suggest that ‘with appropriate training, experience and performance, ultrasound techniques have the potential to produce successful nerve block with no complications secondary to needle misplacement in all cases’. This is a fundamental difference to other currently employed regional techniques in which the technology does not reliably confirm perineural location of the needle, nor does it permit identification of anatomical variation. Consequently, block success and avoidance of complications with these techniques always include an element of luck, an element that ultrasound guidance eliminates. McCartney disagrees with my assertion that there are no inherent harmful effects of ultrasound guidance and yet all the examples he gives are dependent on operator deficiency.
Cornforth and Hargreaves criticize me for not recognizing that we all err from perfection, yet this is precisely my point—the technique has the potential to be successful and safe, so any problems are human deficiencies. We should not be afraid to admit that human factors affect performance, but we should expect to inform patients of any impact on their care, for example, our own success rates with a regional anaesthetic technique. We should also expect to demonstrate how we conduct our practice in order to minimize the risks of patients coming to harm from our inevitable human deficiencies. For example, when teaching ultrasound-guided regional techniques, my advice is to not proceed or to abandon the procedure at any stage if you cannot identify: the desired point(s) of injection; all the structures through which the needle has to pass; the structures to be avoided; and the real-time location of the needle throughout the procedure.
I have expanded above my arguments that there is the evidence already available to question those who are not actively seeking to introduce ultrasound guidance into their regional anaesthesia practice. I did not, however, imply (strongly or otherwise) that those not using ultrasound are negligent. Rather, I suggested it might become advisable, in order to limit the potential for litigation, that when we consent patients for regional anaesthesia, we explain that a range of techniques is in use and justify the use of the proposed technique. This was the approach used by orthopaedic surgeons who continued to perform open meniscectomies when the majority had adopted arthroscopic techniques.
Dr van Velzen adopts a cynical attitude to my motives. I can assure him that there are ‘no strings attached’ to my sponsorship from SonoSite. My views are based on my appraisal of the literature and experience of a variety of regional anaesthetic techniques. My motives are ultimately for patient benefit and to encourage readers to embrace the full range of relevant evidence. I agree with van Velzen that injection of local anaesthetic into the nerve sheath may not be as harmful as previously thought. I suspect, from cases that I am aware of, that a more significant factor is direct needle damage secondary to multiple needling of a nerve. I abandoned using nerve stimulators in conjunction with ultrasound when I observed that it was not unusual for the needle tip to be directly adjacent to a nerve trunk while not eliciting a response to the nerve stimulator, illustrating the lack of sensitivity of nerve stimulation.11 I believe this is a potential drawback of ‘blind techniques’.
P. M. Hopkins has the use of ultrasound equipment loaned by SonoSite UK Ltd and has received funding from SonoSite UK Ltd for expenses relating to speaking engagements.
References
1 Karmakar MK, Kwok WH, Ho AM, Tsang K, Chui PT, Gin T. Ultrasound-guided sciatic nerve block: description of a new approach at the subgluteal space. Br J Anaesth (2007) 98:390–5.
2 Hopkins PM. Ultrasound guidance as a gold standard in regional anaesthesia. Br J Anaesth (2007) 98:299–301.
3 Frates MC, Benson CB, Charboneau JW, et al. Management of thyroid nodules detected at US: Society of Radiologists in ultrasound consensus conference statement. Radiology (2005) 237:794–800.
4 Fajardo LL, Pisano ED, Caudry DJ, et al. Stereotactic and sonographic large-core biopsy of nonpalpable breast lesions: results of the Radiologic Diagnostic Oncology Group V study. Acad Radiol (2004) 11:293–308.[CrossRef][ISI][Medline]
5 Dillon MF, Hill AD, Quinn CM, O'Doherty A, McDermott EW, O'Higgins N. The accuracy of ultrasound, stereotactic, and clinical core biopsies in the diagnosis of breast cancer, with an analysis of false-negative cases. Ann Surg (2005) 242:701–7.[CrossRef][ISI][Medline]
6 Brown DL, Cahill DR, Bridenbaugh LD. Supraclavicular nerve block: anatomic analysis of a method to prevent pneumothorax. Anesth Analg (1993) 76:530–4.
7 Dennie NM, Harrop-Griffiths W. Location, location, location! Ultrasound imaging in regional anesthesia. Br J Anaesth (2005) 94:1–3.
8 Willschke H, Marhofer P, Bosenberg A, et al. Ultrasonography for ilioinguinal/iliohypogastric nerve blocks in children. Br J Anaesth (2005) 95:226–30.
9 Bigeleisen PE. Nerve puncture and apparent intraneural injection during ultrasound guided axillary block does not invariably result in neurologic injury. Anesthesiology (2006) 105:779–83.[CrossRef][ISI][Medline]
10 Smith GCS, Pell JP. Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials. Br Med J (2003) 327:1459–61.
11 Perlas A, Nizi A, McCartney C, Chan V, Xu D, Abbas S. The sensitivity of motor responses to nerve stimulation and paresthesia for nerve localization as evaluated by ultrasound. Reg Anesth Pain Med (2006) 31:445–50.[CrossRef][ISI][Medline]
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