Cardiac surgery in patients with moderate renal impairment.

ABSTRACT

Background. There is a paucity of information concerning the results of cardiac surgery in patients with moderate impairment of renal function. We reviewed our recent experience to determine the results of operation and the long-term outcome.

Methods. Since January 1992, we have performed cardiac surgical procedures utilizing total cardiopulmonary bypass on 57 adult patients with preoperative serum creatinine values [greater than or equal to]2.0 mg/dL and no history of dialysis. Operative procedures clone were coronary artery bypass (39 patients), repeated coronary artery bypass (2), valve replacement with or without coronary artery bypass (12), and other procedures (4).

Results. No operative deaths occurred. There were 3 hospital deaths. Only 5 patients required perioperative dialysis; in 5 additional patients, chronic dialysis was begun from 4 to 24 months postoperatively. The surviving patients who were not receiving dialysis had a mean creatinine value of 2.4 mg/dL at most recent follow-up.

Conclusions. Adult patients with moderate renal impairment can safely have major cardiac procedures. The majority of patients maintain stable renal function postoperatively. The overall results of cardiac surgery in this patient population are good.

CARDIOPULMONARY BYPASS brings a multitude of physiologic changes that may affect short-term and long-term function of many organs, including renal function. Special concerns in patients with renal impairment include acid-base balance, hyperkalemia, volume overload, and clotting abnormalities. All of these have major implications for patients having cardiac surgical procedures. Numerous publications have elucidated the results of cardiac surgery in patients with chronic renal failure requiring dialysis. In contrast, there is a paucity of information concerning the results of operation in those patients with moderate impairment of renal function. We reviewed our experience with cardiac surgery in adult patients with compromised preoperative renal function to determine both the results of operation and the long-term outcome in terms of renal function postoperatively.

MATERIALS AND METHODS

We retrospectively reviewed the records of patients who had cardiac surgical procedures with cardiopulmonary bypass at our institutions from January 1992 through November 1998. We identified 57 adult patients who met the arbitrarily defined definition of impaired renal function preoperatively. These patients had a preoperative serum creatinine value [greater than or equal to]2.0 mg/dL and no history of dialysis. Patients who had heart transplantation were not included in the study population because of the confounding issue of cyclosporine use in transplant patients.

All operations were done using standard cardiopulmonary bypass with moderate systemic hypothermia. Myocardial protection measures were aortic cross-clamping, cold crystalloid or blood cardioplegia administered antegrade with or without retrograde cardioplegia, and topical cooling of the heart. Most patients received lowdose dopamine and osmotic diuretics during cardiopulmonary bypass.

Operative mortality was defined as death in the operating room. Early mortality was defined as death during hospitalization or within 30 days of operation. Patients have had postoperative follow-up with particular attention to renal function and whether dialysis was necessary.

RESULTS

The 43 male and 14 female patients ranged in age from 26 to 82 years, with an average age of 63 years. Preoperative serum creatinine values ranged from 2.0 to 6.9 mg/dL, with a mean of 2.6 mg/dL. Operative procedures included coronary artery bypass grafting in 39 patients, repeated coronary artery bypass in 2 patients, valve replacement with or without coronary artery bypass in 12 patients, and other procedures in 4 patients. Cardiopulmonary bypass time ranged from 63 to 479 minutes (mean, 134 minutes). Two patients required mediastinal exploration postoperatively to control bleeding. One patient had a cerebrovascular accident but recovered with nearly complete return of function.

No intraoperative deaths occurred, but 3 early deaths occurred during the initial hospitalization. These early deaths were due to low cardiac output resulting in cardiac arrest in 1 patient, to multiple organ failure in 1 patient, and to multiple organ failure and sepsis in 1 patient. The only identifiable risk factor for early death was the necessity for a slightly complicated operative procedure in 2 patients, 1 of whom had a double valve replacement and 1 of whom had repeated coronary artery bypass grafting. Five patients required initiation of dialysis perioperatively. Two of these patients died during the initial hospitalization, 1 because of low cardiac output and 1 because of multiple organ failure. One patient had dialysis initiated on postoperative day 11 and one patient after discharge (on postoperative day 30); both of these patients have been maintained with long-term dialysis. One patient required dialysis only once (on postoperative day 2) and has maintained satisfactory renal function subseque ntly. In the 5 patients requiring perioperative dialysis, the serum creatinine value ranged from 2.0 to 6.9 mg/dL (mean, 3.7 mg/dL). Those who did not require perioperative dialysis had serum creatinine values ranging from 2.0 to 4.5 mg/dL (mean, 2.2 mg/dL).

Two additional late deaths occurred at 3 and 9 months after operation, respectively, of causes unrelated to renal function. Both patients died suddenly, presumably of acute myocardial infarction. Five additional patients began long-term hemodialysis at 4 months, 1 year (two patients), 23 months and 24 months postoperatively, respectively. Those patients who subsequently required initiation of chronic dialysis late postoperatively had preoperative serum creatinine values ranging from 2.0 to 2.6 mg/dL (mean, 2.3 mg/dL). At the time of discharge from the hospital, their serum creatinine values ranged from 1.7 to 2.6 mg/dL (mean, 2.1 mg/dL). In no instance was the postoperative creatinine higher than the preoperative value. The exact cause of late renal failure necessitating dialysis could not be determined but was not thought to be cardiac function or complications of cardiac surgery in any instance.

The remaining patients who have not required dialysis have had follow-up from 1 month to 2 years postoperatively, with a mean follow-up of 12.1 months. These patients had a mean serum creatinine value of 2.4 mg/dL at the most recent follow-up. Only three patients had an incremental elevation in serum creatinine of >30% compared with their preoperative level.

The requirement to initiate dialysis perioperatively or late postoperatively was not related to patient age, cardiopulmonary bypass time, or the presence of diabetes mellitus.

DISCUSSION

Acute renal failure after cardiac surgery is not uncommon. In years past, the incidence of renal failure after open heart surgery has been reported as high as 39%, depending on the criteria used. (1-8) More recently, Zanardo et al (9) reported that among a series of 734 patients who had normal renal function at the time of cardiac operation, 27 (4%) had acute renal failure.

In a study by Rao et al, (10) a group of patients with preoperative serum creatinine values of [greater than or equal to]1.1 mg/dL were examined. Analysis revealed that postoperative dialysis was necessary to support renal function in 11% of patients identified in this group. This study also showed that when compared with a control group, the group with impaired renal function was more likely to have low cardiac output syndrome, longer ventilatory support time, longer intensive care unit stay, and longer postoperative hospital stay.

Renal failure after cardiac surgery has been strongly associated with baseline renal insufficiency. Preoperative correlates of acute renal failure include advanced age and baseline renal dysfunction. Intraoperative correlates include duration of surgery, cardiopulmonary bypass time, and aortic cross-clamp time. (11) In our patients, we observed no correlation between the requirement for the initiation of dialysis and cardiopulmonary bypass time, aortic cross-clamp time, or the presence of diabetes.

In our patient population, defined arbitrarily as those having a preoperative serum creatinine value [greater than or equal to]2.0 mg/dL, dialysis was needed in five patients perioperatively. Five additional patients required the initiation of dialysis subsequently. Eighty-two percent of patients were free of major renal complications, including dialysis, and in most patients renal function was well preserved.

CONCLUSION

Adult patients with moderate renal impairment can safely have major cardiac procedures and cardiopulmonary bypass. Perioperative initiation of dialysis is required infrequently. The majority of patients maintain stable renal function postoperatively. The overall results of cardiac surgery in this patient population are good and warrant continued application of this technique.

References

(1.) Abel RIM, Wick J, Beck CH, et al: Renal dysfunction following heart operations. Arch Surg 1974; 108:175-177

(2.) Doberneck RC, Reiser MP, Lillehei CW: Acute renal failure after open-heart surgery utilizing extracorporeal circulation and total body perfusion. analysis of 1000 patients. J Thorar Cardiovasc Surg 1962; 43:441-452

(3.) Grismer JT, Levy MJ, Lillehei RC, et al: Renal function in acquired valvular heart disease and effects of extracorporeal circulation. Surgery 1964; 55:2441

(4.) Jaen R, Grossman-Siegert V, Ortega MA, et al: Complications in open heart surgery. J Cardiovasc Surg 1970; 11:129-136

(5.) Moghissi K, McMillan K: Acute renal failure and open heart surgery. BMJ 1972; 2:228-229

(6.) Porter CA, Kloster FE, Herr RJ, et al: Renal complications associated with valve replacement surgery. J Thorac Cardiovasc Surg 1967; 53:145-152

(7.) Yeboah ED, Petrie A, Pead JL: Acute renal failure and open heart surgery. BMJ 1972; 1:412-418

(8.) Yeh TJ, Brackney LE, Hall PD, et al: Renal complications of open heart surgery: predisposing factors, prevention and management.] Thorac Cardiovasc Surg 1964; 47:79-97

(9.) Zanardo G, Michielon P, Paccagnella A, et al: Acute renal failure in the patient undergoing cardiac operation. prevalence, mortality rate and main risk factors. J Thorac Cardiovasc Surg 1994; 107-1489-1495

(10.) Rao V, Weisel R, Buth K, et al: Coronary artery bypass grafting in patients with non-dialysis-dependent renal insufficiency. Circulation 1997; 96:11-38-11-45

(11.) Chertow C, Lazarus J, Christiansen C, et al: Preoperative renal risk stratification. Circulation 1997; 95:878-884

RELATED ARTICLE: KEY POINTS

* Adult patients with moderate renal impairment, arbitrarily defined as creatinine values [greater than or equal to]2.0 mg/dL, can safely have major cardiac procedures on cardiopulmonary bypass.

* The mortality and morbidity in our experience is similar to that in patients without renal impairment.

* Renal function is maintained in most patients; perioperative or late postoperative initiation of dialysis is uncommon.

From the surgical Service, Department of Veterans Affairs Medical Center, and the Department of Cardiac and Thoracic Surgery, Vanderbilt University Medical Center, Nashville, Tenn.

Reprint requests to Walter H. Merrill, MD, Department of Veterans Affairs Medical Center, Surgical Service (112), 1310 24th Ave S, Nashville, TN 37212.