Reply to the Editor

Abstract

We read with interest the letter by Kramer and colleagues regarding our recent article exploring the association between the timing of cardiac catheterization and the incidence of postoperative acute kidney injury (AKI) after elective proximal aortic surgery.1Andersen N.D. Williams J.B. Fosbol E.L. Shah A.A. Bhattacharya S.D. Mehta R.H. et al.Cardiac catheterization within 1 to 3 days of proximal aortic surgery is not associated with increased postoperative acute kidney injury.J Thorac Cardiovasc Surg. 2012; 143: 1404-1410Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar Our study is noteworthy in that it failed to identify an increased incidence of AKI among patients undergoing catheterization within 1 to 3 days of surgery when compared with patients undergoing catheterization 4 or more days before surgery. This finding seemingly contradicts a study by Kramer and colleagues,2Kramer R.S. Quinn R.D. Groom R.C. Braxton J.H. Malenka D.J. Kellett M.A. et al.Same admission cardiac catheterization and cardiac surgery: is there an increased incidence of acute kidney injury?.Ann Thorac Surg. 2010; 90 (discussion 1423-4): 1418-1423Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar which found that catheterization during the same admission as coronary artery bypass grafting or valve surgery was associated with an increased incidence of AKI relative to catheterization during a previous admission. Kramer and colleagues now assert that our findings should be read with caution because of the presence of variability between patient groups in our study. As outlined in our discussion, there are many other reasons why our results may differ from the findings of the study of Kramer and colleagues.2Kramer R.S. Quinn R.D. Groom R.C. Braxton J.H. Malenka D.J. Kellett M.A. et al.Same admission cardiac catheterization and cardiac surgery: is there an increased incidence of acute kidney injury?.Ann Thorac Surg. 2010; 90 (discussion 1423-4): 1418-1423Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar First, the proximal aortic surgical patients in our study were younger, healthier, and at a lower baseline risk of development of contrast-induced nephropathy than the coronary artery bypass grafting and valve surgical patients included in the study of Kramer and colleagues.2Kramer R.S. Quinn R.D. Groom R.C. Braxton J.H. Malenka D.J. Kellett M.A. et al.Same admission cardiac catheterization and cardiac surgery: is there an increased incidence of acute kidney injury?.Ann Thorac Surg. 2010; 90 (discussion 1423-4): 1418-1423Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar Second, same-day catheterizations, which have been associated with the highest risk of postoperative AKI in some previous studies,1Andersen N.D. Williams J.B. Fosbol E.L. Shah A.A. Bhattacharya S.D. Mehta R.H. et al.Cardiac catheterization within 1 to 3 days of proximal aortic surgery is not associated with increased postoperative acute kidney injury.J Thorac Cardiovasc Surg. 2012; 143: 1404-1410Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar, 3Ranucci M. Ballotta A. Kunkl A. De Benedetti D. Kandil H. Conti D. et al.Influence of the timing of cardiac catheterization and the amount of contrast media on acute renal failure after cardiac surgery.Am J Cardiol. 2008; 101: 1112-1118Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar, 4Mehta R.H. Honeycutt E. Patel U.D. Lopes R.D. Williams J.B. Shaw L.K. et al.Relationship of the time interval between cardiac catheterization and elective coronary artery bypass surgery with postprocedural acute kidney injury.Circulation. 2011; 124: S149-S155Crossref PubMed Scopus (44) Google Scholar were not performed at our institution. Most importantly, our study was restricted to patients undergoing elective surgery, and all emergency and urgent procedures were excluded. In the study of Kramer and colleagues,2Kramer R.S. Quinn R.D. Groom R.C. Braxton J.H. Malenka D.J. Kellett M.A. et al.Same admission cardiac catheterization and cardiac surgery: is there an increased incidence of acute kidney injury?.Ann Thorac Surg. 2010; 90 (discussion 1423-4): 1418-1423Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar patients requiring urgent operation were included in the analysis and comprised 87% of the same-admission catheterization group, compared with only 14% of the previous-admission catheterization group. As a result, patients undergoing catheterization during the same admission as surgery were 25 times more likely to have had a preoperative myocardial infarction, had a higher incidence of 3-vessel coronary artery disease, had lower ejection fractions, had a higher incidence of preoperative balloon pump use, and had longer cardiopulmonary bypass times. Thus Kramer and colleagues2Kramer R.S. Quinn R.D. Groom R.C. Braxton J.H. Malenka D.J. Kellett M.A. et al.Same admission cardiac catheterization and cardiac surgery: is there an increased incidence of acute kidney injury?.Ann Thorac Surg. 2010; 90 (discussion 1423-4): 1418-1423Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar essentially compared elective patients who underwent catheterization on a previous admission with urgent patients who underwent catheterization during the same admission as surgery. Not surprisingly, the urgent patients had worse outcomes, including more AKI. Thus although our study does contain some important differences between patient groups that should be considered by the reader, the restriction of our study to patients undergoing elective operations led to comparatively less selection bias and variability than in the study of Kramer and colleagues.2Kramer R.S. Quinn R.D. Groom R.C. Braxton J.H. Malenka D.J. Kellett M.A. et al.Same admission cardiac catheterization and cardiac surgery: is there an increased incidence of acute kidney injury?.Ann Thorac Surg. 2010; 90 (discussion 1423-4): 1418-1423Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar We echo the sentiments of Kramer and colleagues in calling for additional studies to delineate better the ideal time frame between catheterization and cardiac surgery. The Society of Thoracic Surgeons database may provide the best opportunity to study this question by interrogating a multi-institutional clinical database that allows comprehensive risk-adjustment for case status as well as the multiple other patient and perioperative factors that contribute to AKI. The study could further be designed to assess the association between the timing of catheterization and the incidence of postoperative AKI among various subsets of the cardiac surgical population, including those undergoing coronary artery bypass grafting, valve operations, and proximal aortic surgery. Association of catheterization with acute kidney injury in the cardiac surgical patientThe Journal of Thoracic and Cardiovascular SurgeryVol. 145Issue 1PreviewIn a recent publication, Andersen and colleagues1 concluded that cardiac catheterization within 1 to 3 days before proximal aortic surgery is not associated with an increase in postoperative acute kidney injury (AKI). Although our own interest in the occurrence and duration of AKI has lain primarily with patients undergoing coronary artery bypass grafting,2,3 we are conscious of special circumstances in which the postoperative AKI rate does not appear to be affected, such as for same-day cardiac catheterization and aortic valve surgery. Full-Text PDF