Acute renal failure in the patient undergoing cardiac operation. Prevalence, mortality rate, and main risk factors.

A total of 775 consecutive patients who survived the first 24 hours after cardiac operation were prospectively studied to assess the prevalence, mortality rate, and main risk factors for development of new acute renal failure. Normal renal function before operation (serum creatinine level less than 1.5 mg/dl) was registered in 734 (94.7%) patients. Of these, 111 (15.1%) showed a postoperative renal complication including 84 (11.4%) classified as renal dysfunction (serum creatinine level between 1.5 and 2.5 mg/dl) and 27 (3.7%) as acute renal failure (serum creatinine level higher than 2.5 mg/dl). The mortality rate was 0.8% in normal patients, 9.5% in patients with renal dysfunction, and 44.4% when acute renal failure developed (p < 0.0001). Indeed, the renal impairment proved to be an independent predictor of mortality (p < 0.001), along with the infective (p < 0.001), gastrointestinal (p < 0.001), and cardiovascular (p < 0.05) complications. Multivariate analysis identified the following variables as independent risk factors for postoperative renal impairment: use of intraaortic balloon pump (p < 0.0001), need for deep hypothermic circulatory arrest (p < 0.005), low-output syndrome (p < 0.005), advanced age (p < 0.005), need for emergency operation (p < 0.025), and low urinary output during cardiopulmonary bypass (p < 0.05). The 41 patients (5.3%) with preoperative renal failure showed a significantly higher morbidity and mortality rate than those without renal complications before operation. We conclude that in patients undergoing cardiac operation without preexisting renal dysfunction the likelihood of severe renal complications is reasonably low, but the associated mortality remains high. A prominent role in the development of postoperative acute renal failure must be recognized for preoperative, intraoperative, and postoperative hemodynamic factors, whereas cardiopulmonary bypass seems to be of lesser importance in this respect.

[Gastric pH changes during and after extracorporeal circulation. What is its clinical meaning?]. / Variazione del pH gastrico durante e dopo circolazione extracorporea. Quale significato clinico?

OBJECTIVE: To determine the relationship between gastric pH (pHm) and several other indices of blood perfusion in patients undergoing cardiopulmonary bypass (CPB). To evaluate the importance of pHm as a prognostic index for elective cardiac surgery. DESIGN: Prospectives study. SETTING: Cardiac surgery ICU of a Regional Hospital in Italy. PATIENTS: Nineteen patients were sequentially studies in a 4-month period. METHOD: Before anesthetic induction, a pH probe incorporated in the tip of a nasogastric tube (GrapHprobe SH, GrapHometer, Zinetics Medical, USA) was inserted in the stomach. Results, collected during the CPB and in the postoperative period until 1 hour after extubation, were compared to the peripheral tissue perfusion and oxygenation data (transcutaneous: PtcO2), hemodynamic variations (Swan-Ganz catheter), pharyngeal temperature, and blood gases. RESULTS: No significant variations of pHm were reported during the study. Significant relations were found only after surgery between pHm and PaO2 (p < 0.001), hemoglobin (p < 0.001), and blood pH (p < 0.05). No statistical correlations were reported between pHm and hemodynamic variations. CONCLUSIONS: Although a significant variation of peripheral and pulmonary vascular resistance and transcutaneous oxygenation was reported throughout the study, no correlations were found to pHm. At present it is not possible to confirm the importance of pHm as a prognostic index for elective cardiac patients, even though it is necessary to examine whether the additional data of pHm variation could be considered a true marker of visceral perfusion.

Effects of a continuous diltiazem infusion on renal function during cardiac surgery.

Thirty-five male patients undergoing coronary artery surgery were studied to investigate renal function during a continuous infusion of the calcium channel blocker diltiazem. All patients had preoperative renal function within normal limits (serum creatinine below 0.133 mmol/L) and were randomly divided into three groups: Control (C), Diltiazem 1 (D1), and Diltiazem 2 (D2). Diltiazem was infused in D1 (1 microgram/kg/min) and D2 (2 micrograms/kg/min) patients throughout surgery and during the following 36 hours. Glomerular function was investigated using the endogenous creatinine clearance while tubular function was assessed by means of water and sodium reabsorption tests, as well as urinary enzyme activity measurements. Hemodynamic monitoring was performed using a pulmonary artery catheter. The glomerular filtration rate of C and D1 patients showed a significant fall during cardiopulmonary bypass (CPB) with respect to the prebypass period and returned to the baseline values only in the postoperative period. A similar change was not observed in D2 patients. The analysis of variance demonstrated that the glomerular filtration rate was significantly higher in Group D2 versus Group C during and after CPB (P = 0.03 and P = 0.04, respectively). Furthermore, after CPB, urinary output was significantly improved in D2 patients, both versus C and D1 patients (P = 0.003), notwithstanding a lower mean arterial pressure in the D2 Group (P = 0.04 v C Group). Tubular function was not influenced by diltiazem infusion. It is concluded that a continuous diltiazem infusion, at a dose of 2 micrograms/kg/min during cardiac surgery, may be useful to prevent a decrease in glomerular function secondary to cardiopulmonary bypass.

[Noninvasive hemodynamic (bioimpedance) evaluation during short anesthesia with propofol]. / Valutazione emodinamica incruenta (bioimpedenza) in corso di anestesia breve con propofol.

The hemodynamic effects of propofol (3 mg/kg) during anesthetic management of 10 patients undergoing minor urologic procedures were evaluated by noninvasive thoracic electrical bioimpedance method. Cardiac output, cardiac index, systolic and diastolic arterial blood pressures and EVI/TFI (an index of myocardial function) decreased significantly in ten minutes from starting of propofol injection, while the heart rate remained unchanged.