Comparing the Steam Engine With a Horse-Drawn Carriage?

Abstract

In Response: In the study cited by Heller et al., we demonstrated similar rates of postoperative neurologic symptoms (PONS) after nerve stimulator or paresthesia techniques of nerve localization (1). Heller et al.'s negative views of paresthesia techniques are shared by many members of the anesthesia community. However, as clinicians and scientists, we should not be dealing with opinions, but rather on facts supported by rigorous scientific studies. First, Heller et al. state that the incidence of PONS in our patients is “strikingly high,” and they use a recent prospective case series (2), their “own experience,” and “European leaders' opinion” as support for this statement. “Opinions” and “experience” aside, the study referenced by Heller et al. that indicated a 3% incidence of PONS, followed patients who underwent many different operative procedures and who received either upper or lower extremity continuous peripheral nerve blockade for 2–7 days. We studied a single anesthetic and a single surgical procedure. Furthermore, in many patients, PONS presented and resolved within the timeframe of the continuous infusion referenced. Comparing these two studies is simply not appropriate. There are many more appropriate comparison studies that describe an incidence of PONS in the range we report (3–6). Second, although we agree with Heller et al. that ultrasound is a potentially useful method to assist in nerve localization for peripheral nerve block, there are few randomized, controlled trials evaluating the safety and efficacy of ultrasound in preventing PONS. Until the results of more such studies are available, we should keep an open mind. As Heller et al. correctly state, the relationship between needle tip and nerve are unclear (at best) with both paresthesia and nerve stimulator studies (7–9). In addition, a recent report by Bigeleisen (10) clearly shows that ultrasound techniques may not be reliable to avoid nerve contact. Furthermore, we do not understand the relevance of Heller et al.'s reference to the closed claims analysis (11). None of our patients suffered lasting injury, and there is no evidence that ultrasound-guided nerve blocks are safer than nerve blocks performed with other techniques. Third, Heller et al.'s comment that the volume of local anesthetic used is “outdated and potentially toxic” is another example of a commonly held, yet scientifically unsupported opinion. A comprehensive review on this topic attempts to differentiate between opinion and fact (12). Finally, it is true that it is difficult to statistically prove that two procedures yield equivalent results. We found a 9.3% incidence of PONS with the paresthesia technique (90% CI: 4.7%–13.9%) and a 10.1% incidence with the nerve stimulator technique (90% CI: 5.3%–14.7%). It is likely that if any difference did exist, it would be too small to be clinically significant. Anesthesiologists should be guided by facts supported by randomized, controlled trials, and not swayed by personal experiences and opinions. If we focus on facts, it is quite possible that other myths in anesthesia will be dispelled. We are certain that at some point during the 20th century, popular opinion was that steam engines would be the primary source of transportation energy for decades to come. Popular opinion is not always correct. Gregory A. Liguori, MD Jacques T. YaDeau, MD, PhD Victor M. Zayas, MD Richard Kahn, MD Leonardo Paroli, MD, PhD Valeria Buschiazzo, BS Department of Anesthesiology Hospital for Special Surgery Weill Medical College of Cornell University New York, New York [email protected]