Renal preservation in cardiac surgery

Acute renal dysfunction: time from coronary angiography to cardiac surgery

Background

The incidence of acute renal dysfunction has not changed much over the years, despite improvements in perioperative care. Our objectives were to evaluate the impact of timing of cardiac surgery after coronary angiography on acute renal dysfunction, to identify risk factors associated with development of acute renal dysfunction, and to measure the association between acute renal dysfunction and mortality.

Patients and methods

The patients were divided into 3 groups: group A (cardiac surgery 0–3 days after angiography), group B (surgery 4–6 days after angiography), and group C (surgery > 6 days after angiography). Endpoints were acute renal dysfunction, defined as serum creatinine > 25% of baseline on the 3rd postoperative day, and mortality.

Results

In 749 patients, the incidence of acute renal dysfunction was 15%; 5% required dialysis. Hypertension, congestive heart failure, chronic obstructive pulmonary disease, ejection fraction < 40%, prolonged cardiopulmonary bypass time, intraaortic balloon pump use, and urgent surgery were risk factors for acute renal dysfunction after cardiac surgery. Patients in group C had a lower risk of acute renal dysfunction.

Conclusion

Acute renal dysfunction has a definite relationship with the time period between angiography and cardiac surgery. The causative factors for this condition are multiple and also show a consistent association with mortality.

Renal function and histology after acute hemorrhage in rats under dexmedetomidine action

PURPOSE: About 50 % of indications for dialysis in acute renal failure are related to problems originated during the perioperative period. Intraoperative hemodynamic changes lead to renal vasoconstriction and hypoperfusion. Previous studies have not defined the dexmedetomidine renal role in hemorrhage situations. This study evaluated the effect of dexmedetomidine on renal function and histology after acute hemorrhage in rats. METHODS: Covered study with 20 Wistars rats, anesthetized with sodium pentobarbital, 50 mg. kg-1, intraperitoneal, randomized into 2 groups submitted to 30% volemia bleeding: DG - iv dexmedetomidine, 3 µg. kg-1 (10 min) and continuous infusion - 3 µg. kg-1. h-1; CG - pentobarbital. For renal clearance estimative, sodium p-aminohippurate and iothalamate were administered. Studied attributes: heart rate, mean arterial pressure, rectal temperature, hematocrit, iothalamate and p-aminohippurate clearance, filtration fraction, renal blood flow, renal vascular resistance, and histological evaluations of the kidneys. RESULTS: DG showed smaller values of heart rate, mean arterial pressure, and renal vascular resistance, but iothalamate clearance and filtration fraction values were higher. There was similarity in p-aminohippurate clearance and renal blood flow. Both groups had histological changes ischemia-like, but dexmedetomidine determined higher tubular dilatation scores. CONCLUSION: In rats, after acute hemorrhage, dexmedetomidine determined better renal function, but higher tubular dilation scores.

Renal Dysfunction in High-Risk Patients After On-Pump and Off-Pump Coronary Artery Bypass Surgery: A Propensity Score Analysis

BACKGROUND

Cardiopulmonary bypass may be a causal factor in the development of renal impairment after cardiac surgery. When acute renal failure requiring dialysis occurs after cardiac surgery, it is associated with high mortality. We attempted to determine whether off-pump coronary artery bypass grafting surgery prevents postoperative renal dysfunction in patients at high risk for renal failure.

METHODS

Retrospective analysis identified 2,869 patients who had preexisting renal dysfunction (preoperative creatinine clearance less than 60 mL/min) and who underwent isolated coronary artery bypass grafting between 1995 and 2003. Patients who required preoperative dialysis were excluded. Propensity scores were computed to match off-pump coronary artery bypass surgery patients 3:1 with those who underwent conventional coronary artery bypass grafting surgery, and the independent predictors of postoperative renal dysfunction were determined.

RESULTS

Two thousand seven hundred eleven patients with preexisting renal dysfunction underwent conventional coronary artery bypass grafting surgery, and 158 patients underwent coronary artery bypass grafting surgery without cardiopulmonary bypass (off-pump coronary artery bypass grafting surgery group). The matched groups showed no differences in any of the preoperative or postoperative variables examined. Diabetes (odds ratio, 1.96; p = 0.01), peripheral vascular disease (odds ratio, 2.50; p < 0.001), and reduced preoperative creatinine clearance (odds ratio, 1.02; p = 0.02) were independent risk factors for the development of postoperative renal dysfunction. Off-pump coronary artery bypass grafting surgery was not associated with a decreased risk of renal dysfunction by univariate or multivariable analysis.

CONCLUSIONS

Off-pump coronary artery bypass grafting surgery did not reduce the risk of postoperative renal dysfunction in this large, unselected, sequential series of patients at high risk for renal failure after coronary artery bypass grafting surgery. Our results suggest that renal function should not be a deciding factor when determining whether or not a patient undergoes off-pump coronary artery bypass grafting surgery.

Diltiazem may preserve renal tubular integrity after cardiac surgery

PURPOSE

To evaluate the influence of dopamine and diltiazem on renal function and markers for acute renal failure, including urinary alpha-glutathion s-transferase (alpha-GST), alpha-1-microglobulin (alpha(1)-MG) and N-acetyl-ss-glucosaminidase (ss-NAG) after extracorporeal circulation.

METHODS

In a randomized, placebo-controlled, double-blind trial we evaluated the efficacy of dopamine (2.5 micro g x kg(-1) x min(-1)), diltiazem (2 micro g x kg(-1) x min(-1)) or placebo administered over 48 hr postoperatively to maintain renal tubular integrity in 60 elective cardiac surgery patients. alpha-GST, alpha(1)-MG, ss-NAG, and creatinine clearance were measured from urine collected during surgery (T0), the first four hours (T1), 24 hr (T2) and 48 hr (T3) postoperatively.

RESULTS

Cumulative urine output in the diltiazem group (9.0 +/- 2.8 L) increased significantly compared with placebo (7.0 +/- 1.6 L), but not compared with dopamine (7.8 +/- 1.8 L). Creatinine clearance showed no significant intergroup differences. In all groups alpha(1)-MG increased from T0 to T3, but we found no significant intergroup differences. alpha-GST increased significantly from T0 to T3 in the placebo (2.1 +/- 1.8 to 11.4 +/- 8.6 micro g x L(-1)) and in the dopamine groups (2.7 +/- 1.8 to 13.6 +/- 14.9 micro g x L(-1)), but not in the diltiazem group (1.8 +/- 1.4 to 3.2 +/- 3.2 micro g x L(-1)). Forty-eight hours postoperatively alpha-GST was significantly lower in the diltiazem group than in both other groups.

CONCLUSIONS

Diltiazem stimulates urine output, reduces excretion of alpha-GST and ss-NAG and may be useful to maintain tubular integrity after cardiac surgery.

Coronary revascularization with or without cardiopulmonary bypass in patients with preoperative nondialysis-dependent renal insufficiency

BACKGROUND

Preoperative renal insufficiency is a predictor of acute renal failure in patients undergoing conventional coronary artery bypass grafting. Off-pump coronary artery bypass operations have been shown to reduce renal dysfunction in patients with normal renal function, but the effect of this technique in patients with preoperative nondialysis-dependent renal insufficiency is unknown.

METHODS

From June 1996 to December 1999, data of 3,250 consecutive patients undergoing coronary artery bypass grafting were prospectively entered into the Patient Analysis & Tracking Systems (PATS, Dendrite Clinical Systems, London, UK). Two hundred and fifty-three patients with preoperative serum creatinine more than 150 micromol/L were identified (202 patients on-pump, 51 patients off-pump), and clinical outcomes were analyzed. Serum creatinine and urea, in-hospital mortality, and morbidity were compared between groups. The association of perioperative factors with acute renal failure was investigated by multiple logistic regression analysis.

RESULTS

Preoperative characteristics were similar between the groups. Mean number of grafts was 2.9 +/- 0.8 and 2.3 +/- 0.8 in the on-pump and off-pump groups, respectively (p < 0.0001). Comparison between groups showed a significantly higher incidence of stroke, inotropic requirement, blood loss, and transfusion of red packed cell and platelets in the on-pump group (all p < 0.05). Postoperative serum creatinine and urea were higher in the on-pump group with a significant difference at 12 hours postoperatively (p < 0.05). Logistic regression analysis identified cardiopulmonary bypass, serum creatinine level 60 hours postoperatively, inotropic requirement, need for intraaortic balloon pump, transfusion of red packed cell, and hours of ventilation as predictors of postoperative acute renal failure.

CONCLUSIONS

This study suggests that off-pump coronary artery bypass operations reduce in-hospital morbidity and the likelihood of acute renal failure in patients with preoperative nondialysis-dependent renal insufficiency undergoing myocardial revascularization.