Why chest compressions should start when systolic arterial blood pressure is below 50 mm Hg in the anaesthetised patient. Reply to Br J Anaesth 2020; 124: 234–8

Editor—We read with interest the editorial by Harper and colleagues,1Harper N.J.N. Nolan J.P. Soar J. Cook T.M. Why chest compressions should start when systolic arterial blood pressure is below 50 mm Hg in the anaesthetised patient.Br J Anaesth. 2020; 124: 234-238Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar in which an emphasis was placed on pre-emptive cardiopulmonary resuscitation (CPR) at systolic BP (SBP) less than 50 mm Hg. We also believe that, with early institution of CPR, many life-threatening episodes of cardiac arrest can be prevented. However, its applicability needs to be classified in real-world situations, such as children vs adults vs older adults, perioperative vs intensive care, healthy vs critically ill patients, and patients with and without significant co-morbidities. We believe that the same dictum should not be applied to all groups of patients, and the specific high-risk patients and conditions need to be specified. Most hypotensive episodes in the intraoperative period, particularly in young healthy patients, are transient and are corrected rapidly with a targeted oriented approach, for example, hypotension as a result of vagal stimulation. The trigemino-cardiac reflex is a common phenomenon during neurosurgery that manifests with varied autonomic disturbances, such as hypotension.2Sandu N. Chowdhury T. Meuwly C. Schaller B. Trigeminocardiac reflex in cerebrovascular surgery: a review and an attempt of a predictive analysis.Expert Rev Cardiovasc Ther. 2017; 15: 203-209Crossref PubMed Scopus (7) Google Scholar For such hypotensive episodes, it would be excessive to initiate CPR, which would create panic and disrupt the surgical procedure and potentially worsen outcome. Selecting an arbitrary value for SBP of 50 mm Hg as a threshold for initiation of CPR also requires rationale. We feel that mean arterial pressure provides a stronger determinant when noninvasive BP is measured, as it overestimates SBP at low BP as the authors mentioned; the degree of such SBP overestimation is not known precisely. Whilst the incidence of intraoperative cardiac arrest is very low (0.03–0.05%),3Kaiser H.A. Saied N.N. Kokoefer A.S. Saffour L. Zoller J.K. Helwani M.A. Incidence and prediction of intraoperative and postoperative cardiac arrest requiring cardiopulmonary resuscitation and 30-day mortality in non-cardiac surgical patients.PLoS One. 2020; 15e0225939Crossref PubMed Scopus (5) Google Scholar,4Fielding-Singh V. Willingham M.D. Fischer M.A. Grogan T. Benharash P. Neelankavil J.P. A population-based analysis of intraoperative cardiac arrest in the United States.Anesth Analg. 2020; 130: 627-634Crossref PubMed Scopus (5) Google Scholar we presume that over-aggressive pre-emptive CPR potentially resulting in unwanted injuries will have a higher incidence. We also agree with the comments of Granfeldt and Anderson5Granfeldt A. Anderson L.W. Starting chest compressions: one pressure does not fit all.Br J Anaesth. 2020; 124: e199-200Abstract Full Text Full Text PDF Scopus (2) Google Scholar that one arterial pressure does not fit all; rather, a threshold for CPR should be individualised. Unsynchronised CPR, especially during impaired ventricular filling, can be counterproductive. Finally, newer indices, such as the Hypotension Prediction Index that provides an accurate real-time and continuous prediction of impending intraoperative hypotension, can be used so that rescue measures can be instituted early.6Davies S.J. Vistisen S.T. Jian Z. Hatib F. Scheeren T.W.L. Ability of an arterial waveform analysis-derived Hypotension Prediction Index to predict future hypotensive events in surgical patients.Anesth Analg. 2020; 130: 352-359Crossref PubMed Scopus (39) Google Scholar In our opinion, high-risk patients (e.g. critically ill) should be identified for earlier intervention instead of using an arbitrary SBP value of 50 mm Hg for institution of pre-emptive CPR. The authors declare that they have no conflicts of interest.