Erector spinae plane block and N‐rays

In recent years, the erector spinae plane block has become increasingly popular. In their narrative review, Turbitt et al. present it as a Plan A block that should be a core competency for all anaesthetists [1]. Given the unreliable and infrequent spread of local anaesthetic to the ventral branch of the spinal nerves and the paravertebral space, as well as its unpredictable effects, the wide range of applications of the erector spinae plane block is surprising. The suggested indications for erector spinae plane blocks are indeed more numerous than for any other peripheral nerve or interfascial plane block. To this day, the effectiveness of the block has been shown in hundreds of studies. However, the quality of many studies is low, sample sizes are small and there is often a high risk of bias. In contrast, high-quality multicentre studies published recently show no beneficial effect [2]. In view of the great enthusiasm for this block, we recall an episode in scientific history. In 1903, the French physicist René Blondlot identified N-rays as part of the electromagnetic spectrum [3]. Directed at an electrical spark, N-rays increased the brightness of the light source. N-rays were emitted from inert and living objects, as well as the human body and brain [4]. Remarkably, through psychic activity and concentration, the electromagnetic waves could be bundled and emitted through a human's eyes. It was therefore discussed in the scientific community if N-rays could explain paranormal phenomena such as telepathy or mind reading. The existence of N-rays was initially confirmed by many highly regarded physicists. In the short term of just three years, over 100 scientists had published >300 papers in recognised scientific journals such as the Scientific American [4]. However, some colleagues, such as Heinrich Rubens, the German physicist, failed to reproduce N-rays. After initial frustration and self-doubt about his own incompetence, Ruben proposed a controlled experiment with a blinded setup. When visiting Blondlot's laboratory in France, Robert W. Wood, the American optical physicist, modified the experiments according to Rubens' suggestions so that the investigators could not observe if the radiation source was activated or not. This was done secretly without the knowledge of Blondlot and co-workers. After blinding the experimental setup, N-rays could no longer be detected. Wood published this in a letter and resolved the story of the N-rays in the scientific community [5]. Today, the existence of N-rays is no more assumed. The reason for the repeated incorrect verification of the phenomenon in the beginning of the 20th century might be best explained by confirmation bias. We indeed see some parallels between the popularity and enthusiasm of these blocks today and that of N-rays in the past. At the beginning of the 20th century, scientists were enthusiastic due to the breakthrough discoveries of various types of radiation within the electromagnetic spectrum, such as X-rays and radioactivity. Today, in the field of regional anaesthesia, fascial plane blocks have generated comparable enthusiasm within our community of anaesthetists and the number of positive publications on these blocks is overwhelming, as it was for the N-rays then. Scientists who propagate the theory of N-rays and erector spinae plane blocks had, and still have, a substantial academic background and have contributed to many important developments in their field. However, just as Rubens failed to depict the effect of N-rays, some colleagues fail to achieve sensory anaesthesia of the anterior truncal wall. Some of us might therefore begin to doubt their professional skills. There is, of course, a relevant difference. Unlike N-rays, the erector spinae plane block has a demonstrable, albeit very limited, effect. Technique can be of use for indications when the dorsal branches of the spinal nerves are involved in a pain mechanism. However, we question the wide range of indications that are proposed. Consequently, we do not agree that it should be considered a Plan A block.