The ongoing quest for pro-inflammatory biomarkers of delirium in cardiac surgery

We read with avid interest the article by Su et al. published recently in the Heart & Lung. 1 Su L.J. Chen M.J. Yang R. Zou H. Chen T.T. Li S.L. et al. Plasma biomarkers and delirium in critically ill patients after cardiac surgery: a prospective observational cohort study. Heart Lung. 2023; 59: 139-145 Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar The authors’ idea of studying the pro-inflammatory biomarkers of postoperative delirium (POD) in a predisposed subset of cardiac surgical patients, is undeniably admirable. That being said, a response is humbly sought of the research group regarding certain overlooked aspects in the study. First, Su et al. do not account for the incidence of atrial fibrillation (AF) in their study participants. 1 Su L.J. Chen M.J. Yang R. Zou H. Chen T.T. Li S.L. et al. Plasma biomarkers and delirium in critically ill patients after cardiac surgery: a prospective observational cohort study. Heart Lung. 2023; 59: 139-145 Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar Indeed, a comprehensive review by Banach et al. on the significance of AF in cardiac surgical patients, outlines mechanisms including cerebral hypoperfusion and embolic load, owing to which the rhythm disturbance potentially contributes to POD. 2 Banach M. Mariscalco G. Ugurlucan M. Mikhailidis D.P. Barylski M. Rysz J. The significance of preoperative atrial fibrillation in patients undergoing cardiac surgery: preoperative atrial fibrillation–still underestimated opponent. Europace. 2008; 10: 1266-1270 Crossref PubMed Scopus (37) Google Scholar Moreover, amidst literature existing to link pro-inflammatory biomarkers with AF, the latter could have been an important confounder in the Su et al. study. 1 Su L.J. Chen M.J. Yang R. Zou H. Chen T.T. Li S.L. et al. Plasma biomarkers and delirium in critically ill patients after cardiac surgery: a prospective observational cohort study. Heart Lung. 2023; 59: 139-145 Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar ,3 Guo Y. Lip G.Y. Apostolakis S. Inflammation in atrial fibrillation. J Am Coll Cardiol. 2012; 60: 2263-2270 Crossref PubMed Scopus (567) Google Scholar Second, lack of description of the anesthetic regime is equally difficult to neglect in the index prospective research endeavor. 1 Su L.J. Chen M.J. Yang R. Zou H. Chen T.T. Li S.L. et al. Plasma biomarkers and delirium in critically ill patients after cardiac surgery: a prospective observational cohort study. Heart Lung. 2023; 59: 139-145 Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar Herein, the perioperative use of anesthetic agents such as dexmedetomidine would have been specifically pertinent in the context of evaluating POD as an outcome. 4 Magoon R. Mahajan S. Jose J. DEX, Delirium and dilemma. Braz J Cardiovasc Surg. 2023; 38: 305-308 Crossref Scopus (2) Google Scholar Third, independent researchers like El Azab et al. outline a reduced pro- to anti-inflammatory cytokine ratio in cardiac surgical patients receiving preoperative dexamethasone. 5 El Azab S.R. Rosseel P.M. de Lange J.J. Groeneveld A.B. van Strik R. van Wijk E.M. et al. Dexamethasone decreases the pro- to anti-inflammatory cytokine ratio during cardiac surgery. Br J Anaesth. 2002; 88: 496-501 Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar Thus, the relevance of knowing whether the Su et al. study participants received prophylactic steroids, can also not be undermined, when the practice pertaining to the former continues to be peculiarly heterogeneous. 1 Su L.J. Chen M.J. Yang R. Zou H. Chen T.T. Li S.L. et al. Plasma biomarkers and delirium in critically ill patients after cardiac surgery: a prospective observational cohort study. Heart Lung. 2023; 59: 139-145 Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar ,5 El Azab S.R. Rosseel P.M. de Lange J.J. Groeneveld A.B. van Strik R. van Wijk E.M. et al. Dexamethasone decreases the pro- to anti-inflammatory cytokine ratio during cardiac surgery. Br J Anaesth. 2002; 88: 496-501 Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar , 6 Magoon R. Choudhury A. Sahoo S. Malik V. Steroids for adult cardiac surgery: the debate echoes on. J Anaesthesiol Clin Pharmacol. 2019; 35: 560-562 Crossref PubMed Scopus (3) Google Scholar , 7 Magoon R. Implications of Practice Variability: comment. Anesthesiology. 2020; 133: 943-944 Crossref PubMed Scopus (13) Google Scholar Talking of heterogeneity, a mixed emergency and elective surgical cohort in the present study, could have simultaneously affected the prevailing physiological stress and metabolic derangements, the matter only being compounded by the absence of preoperative estimation of the biomarkers. 1 Su L.J. Chen M.J. Yang R. Zou H. Chen T.T. Li S.L. et al. Plasma biomarkers and delirium in critically ill patients after cardiac surgery: a prospective observational cohort study. Heart Lung. 2023; 59: 139-145 Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar ,7 Magoon R. Implications of Practice Variability: comment. Anesthesiology. 2020; 133: 943-944 Crossref PubMed Scopus (13) Google Scholar