Journal of Clinical Monitoring and Computing | 2021
IONM protocols
Abstract
Protocols are detailed descriptions of standard methodologies that are sufficient in detail to allow other groups to replicate the experiment. In fields such as molecular biology there are entire book series dedicated to the publication of protocols (Methods in Molecular Biology, Springer Publishing). In neuroscience there are dedicated journals such as the Journal of Neuroscience Methods (Journal of Neuroscience Methods—Elsevier). A Medline search for Protocol (in the title) yields over half a million results and an exponential rise in the use of the term in recent years. A protocol paper differs from a methods section in a paper describing results. Obviously, the protocol does not include any results, but it should include evidence that the protocol is feasible. The publication of the protocol allows for independent evaluation of the proposed methodology, both in terms of whether it will answer the question and, also for scientific rigour. The publication of a protocol allows for a review by content experts. Such a publication does not usually involve ethical considerations in the sort of detail that an institutional review board would provide. There is usually a more general review of ethical issues as they relate to whether the study will answer the questions being asked of the study. Publication of a protocol also allows readers of the final study, wherever it is published, to assess whether the protocol was followed and forces the authors to explain protocol violations. Pre-specification of outcomes prevents post-hoc analysis in search of significance, so-called ‘P-hacking’ [1]. It is an important step therefore in improving reliability of research. In this edition, for the first time that we are aware of, a protocol for an intraoperative neuromonitoring study is published. The study by Dulfer and colleagues describes a protocol that attempts to answer an important question in intraoperative neuromonitoring, namely the influence of both depth of anesthesia and blood pressure on motor evoked potential (MEP) amplitude. Using a repeated measures design in which patients undergoing spine deformity surgery undergo a targeted change in depth of anesthesia and change in blood pressure prior to surgery commencing. Depth of anesthesia is assessed in this proposed study by a processed EEG measure on a scale between 0 and 100. Many may quibble about the use of these devices, but they are widely used by colleagues in anesthesia and is regarded as being useful as a measure of sedation [2]. Blood pressure is assessed in the normal manner using an arterial line in the periphery. This is the clinical situation when we encounter changes in MEP amplitude. Systemic blood pressure is a good marker of spinal cord perfusion, which is what we are ultimately trying to assess, but may ignore local changes to flow dynamics that may come into play during spinal surgery. Depth of anesthesia and blood pressure are of course often related, deeper anesthetic giving a lower blood pressure in the absence of other factors and the study design has to be careful to allow for these to be independently assessed. One of the major drivers of blood pressure is blood volume, with less volume the pressure is typically lower and a previous group has shown changes in MEPs during hemorrhage may be related to propofol concentration and not blood pressure per se [3]. The proposed study will not provide all of the answers we seek, but should go a long way towards improving our understanding of the interplay of these variables with MEP amplitude. We eagerly await the outcome of the study.