Cardioprotective effects of acute normovolemic hemodilution in patients with severe aortic stenosis undergoing valve replacement.

BACKGROUND: After acute normovolemic hemodilution (ANH), improvement of the rheologic conditions may contribute to optimize tissue oxygen delivery and attenuate ischemia-reperfusion injuries. It was hypothesized that ANH would confer additional cardioprotection in patients with ventricular hypertrophy undergoing open heart surgery. STUDY DESIGN AND METHODS: This study was a randomized controlled trial. Forty patients scheduled for elective aortic valve replacement were randomly assigned to a control group (standard care) or an ANH group (target hematocrit level of 28%). All patients were managed with standard myocardial preservation techniques (cold blood cardioplegia, anesthetic preconditioning). The outcome measures included the release of myocardial enzymes, perioperative hemodynamic changes, the need for pharmacologic cardiovascular support, and cardiac complications. RESULTS: In the ANH group, the postoperative release of troponin I (mean peak plasma concentrations, 1.7 ng/mL; 95% confidence interval, 1.4-2.1 ng/mL) and myocardial fraction of creatine kinase (22 U/L; range, 18-24 U/L) was significantly lower than in the control group (3.6 [range, 3.0-4.2] ng/mL and 45 [range, 39-51] U/L, respectively). In addition, requirement for inotropic support was significantly lower and fewer hemodiluted patients presented adverse cardiac events. After ANH, there was a significant decrease in heart rate (-11 +/- 6%) and rate-pressure product (-16 +/- 8%) until the aortic cross-clamping time and, at the end of surgery, the circulating levels of erythropoietin (EPO) were higher than in control patients (13.6 +/- 4.2 mUI/mL vs. 7.3 +/- 2.4 mUI/mL; p < 0.05). CONCLUSIONS: Besides conventional cardiac preservation techniques, preoperative ANH further attenuates myocardial injuries. Optimization of preischemic myocardial oxygen delivery and/or consumption and the postconditioning effects of endogenous EPO are potential mechanisms for ANH-induced cardioprotection.

Incidence, risk factors and prognosis of changes in serum creatinine early after aortic abdominal surgery.

OBJECTIVE: To determine the incidence, risk factors, and prognostic implications of serum creatinine changes following major vascular surgery. DESIGN: Observational study. SETTINGS: University hospital. PATIENTS: Cohort of 599 consecutive patients undergoing elective abdominal aortic surgery. INTERVENTIONS: Review of prospectively collected data from 1993 to 2004. MEASUREMENTS AND RESULTS: The receiver-operator characteristic (ROC) curve analysis was used to detect the best threshold for postoperative elevation in serum creatinine (Delta Creat) in relation to major complications. A cut-off value of +0.5 mg/dl was selected to define renal dysfunction (RD(0.5) group, n=91; no RD(0.5), n=508) that was associated with higher mortality (7.7% in RD(0.5) group vs 1.4% in no RD(0.5) group, P<0.05), rate of admission to the ICU (34% vs 13%, P<0.05), and incidence of cardiovascular (9% vs 4%, P<0.05), respiratory (21% vs 7%, P<0.05), surgical (24% vs 10%, P<0.05), and septic complications (9% vs 3%, P<0.05). After multivariate analysis with logistic regression, renal dysfunction was independently related to low preoperative creatinine clearance [<40 ml/min; odds ratio (OR) 1.5, 95% confidence interval (CI) 1.1-3.9], prolonged renal ischemic time (>40 min; OR, 3.8, 95% CI, 1.9-7.2), blood transfusion (>5 units; OR, 1.9, 95% CI 1.2-6.1), and rhabdomyolysis (OR, 3.6, 95% CI 1.7-7.9). CONCLUSIONS: Postoperative RD(0.5) (Delta Creat >0.5 mg/dl) occurs in 15% of vascular patients and carries a bad prognosis. Preoperative renal insufficiency and factors related to the complexity of surgery are the main predictors of renal dysfunction.