Perioperative determinants of morbidity and mortality in elderly patients undergoing cardiac surgery

Abstract

Objective: To determine perioperative predictors of morbidity and mortality in patients >or=to75 yrs of age after cardiac surgery. Design: Inception cohort study. Setting: A tertiary care, 54-bed cardiothoracic intensive care unit (ICU). Patients: All patients aged >or=to75 yrs admitted over a 30-month period for cardiac surgery. Intervention: Collection of data on preoperative factors, operative factors, postoperative hemodynamics, and laboratory data obtained on admission and during the ICU stay. Measurements and Main Results: Postoperative death, frequency rate of organ dysfunction, nosocomial infections, length of mechanical ventilation, and ICU stay were recorded. During the study period, 1,157 (14%) of 8,501 patients >or=to75 yrs of age had a morbidity rate of 54% (625 of 1,157 patients) and a mortality rate of 8% (90 of 1,157 patients) after cardiac surgery.Predictors of postoperative morbidity included preoperative intraaortic balloon counterpulsation, preoperative serum bilirubin of >1.0 mg/dL, blood transfusion requirement of >10 units of red blood cells, cardiopulmonary bypass time of >120 mins (aortic cross-clamp time of >80 mins), return to operating room for surgical exploration, heart rate of >120 beats/min, requirement for inotropes and vasopressors after surgery and on admission to the ICU, and anemia beyond the second postoperative day. Predictors of postoperative mortality included preoperative cardiac shock, serum albumin of 140 mins (aortic cross-clamp time of >120 mins), subsequent return to the operating room for surgical exploration, mean arterial pressure of 120 beats/min, central venous pressure of >15 mm Hg, stroke volume index of 65 yrs. In 1990, the percentage of people >65 yrs of age in the U.S. population was 12.6% (31.4 million), a figure that is projected to increase to 19.6% (58.9 million) by the year 2025 [1]. Although this age group constitutes only 13% of the current population, they account for the use of [approximately]33% of all healthcare resources [2]. The recent increase in healthcare costs has led to evaluation of recent advances in medical and surgical technology offered to elderly patients. Cardiovascular disease is the most common cause of death in the elderly population. With a rapid increase in the size of the elderly population, the demands on resources for cardiac surgery will continue to increase [3]. The appropriateness of cardiac surgery in the group >or=to75 yrs of age has often been debated [4]. It has been suggested that since morbidity and mortality rates are so high in this particular age group, the age of 75 yrs should be used as a cutoff for denial of surgical treatment. With continued advances in operative and anesthetic techniques, this opinion is no longer tenable. A study by Parry et al. [5] addressed the risks and benefits of cardiac surgery in the elderly population and found that the morbidity and mortality rates were not significantly different from those of younger patients. Elective cardiac surgery was found to improve the longevity and functional outcome in selected elderly patients without a prohibitive rate of morbidity or mortality. Several scoring systems were developed to predict postoperative morbidity and mortality of patients undergoing coronary artery bypass surgery (CABG) [6-8]. The scoring systems utilized preoperative risk factors identified from patient cohorts with a wide range of age for a specific surgical procedure. There are several reasons for concern about the validity of such scoring systems being utilized for elderly patients. The disparity of the case-mix of the cohorts used for the development and validation of scoring systems can affect the calibration and discrimination characteristics when applied to elderly patients [9]. These scoring systems lacked definition of operative events which may precipitate subsequent morbidity and mortality in the elderly. Early hemodynamic and biochemical correlates of underlying physiologic derangement immediately after surgery and on admission to the intensive care unit (ICU) were also deficient in these scoring systems [6-8]. There is a demand for accurate definition of risk factors for morbidity and mortality in the elderly patient undergoing cardiac surgery, especially with increasing pressures to limit the critical care resources [10]. Rational allocation of critical care resources to elderly patients is a subject of continuous debate because of the ethical and financial concerns resulting from the futile prolongation of life...