Association Between Anesthesia Techniques and Postoperative Complications in Older Adults with Dementia Undergoing Hip Fracture Surgery

Abstract

To the Editor: The recent article by Seitz et al.1 assessing the association between anesthetic techniques and postoperative complications in older adults with dementia undergoing hip fracture surgery was of great interest. The authors found that general anesthesia and regional anesthesia were associated with similar rates of most perioperative adverse events. The power of this study is its use of several administrative databases containing most of the known preoperative factors that can affect perioperative adverse events in such individuals. To account for systematic differences in observed baseline confounders between individuals receiving general anesthesia and those receiving regional anesthesia, the authors used propensity-score matching to estimate the effects of anesthesia techniques on study endpoints. Nevertheless, this study was a retrospective analysis, which is inevitably subject to uncontrolled and unmeasured confounding. In our view, several important things were not well addressed in this study. First, perioperative hemoglobin levels and transfusion were not included in the data analysis. Perioperative anemia is common in individuals undergoing hip fracture surgery, and anemia at admission and postoperative anemia needing a transfusion are independent risk factors for worse postoperative outcomes in individuals with hip fracture.2 Second, information on mobility and functional status before surgery were not provided and analyzed. Preoperative impaired functional status and mobility disability are common problems of individuals with hip fracture, and more than half of individuals with hip fracture do not regain mobility in the first postoperative year.3 Such conditions can not only impair survival, but may also adversely affect recovery and clinical outcomes in the early postoperative period. Specifically, complete functional dependence has been found to be associated independently with short-term morbidity and mortality after hip fracture surgery.4 Thus, the possibility cannot be excluded that mobility disability was a serious health problem in the participants that confoiunded their data analysis for postoperative adverse events. Third, most importantly, detailed information about the anesthesia and intraoperative management is not provided. Thus, it is difficult to estimate how much influence anesthesiologists’ interventions might have on postoperative outcomes. It has been shown that intraoperative blood loss, hypoxemia, and hemodynamic instability are independently associated with morbidity and mortality after noncardiac surgery.5 Furthermore, short durations of intraoperative mean arterial pressure less than 55 mmHg can result in postoperative myocardial and kidney injuries, with an independent graded relationship between duration of intraoperative hypotension and postoperative myocardial and kidney injuries.6 Typically, based on estimated blood loss, lowest heart rate, and lowest mean arterial pressure during surgery, the Surgical Apgar Score, which was originally developed in individuals undergoing noncardiac surgery, has been shown to be a good predictor of postoperative 30-day major complications.7 Finally, approximately 10% of the participants had chronic kidney disease before surgery, but postoperative kidney complications were not included in the major adverse events. Acute kidney injury is a frequent adverse event in elderly adults after hip fracture surgery. In a study of 90 individuals aged 65 and older undergoing hip fracture surgery, 24% developed acute kidney injury, as defined according to risk, injury, failure, loss, and end-stage renal disease criteria.8 In a study of 165 elderly adults undergoing hip fracture surgery, 15.3% developed acute kidney injury within the first 48 postoperative hours, and preoperative baseline renal function was an independent risk factor for postoperative acute kidney injury.9 In a study of 1,511 individuals undergoing hip fracture surgery, 69 of 730 (9%) with normal renal function before surgery developed renal dysfunction after surgery, and 364 of 545 (67%) with a low glomerular filtration rate upon admission had evidence of postoperative renal dysfunction.10 Furthermore, acute kidney injury is associated with longer hospital stay and greater morbidity.9 We believe that addressing the above factors would increase the transparency of this study. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. None of the authors received financial support and there are no potential conflicts of interest for this work. Author Contributions: All authors have seen and approved the manuscript. Xue carefully read the manuscript of Seitz et al., analyzed their methods and data, suggested comment points, drafted this manuscript, and is responsible for this manuscript. Liu read the manuscript of Seitz et al. and helped to write and revise this manuscript. Sun read the manuscript of Seitz et al. and helped analyze their methods and data, review this manuscript. Sponsor's Role: None.