Jean-François Baron

Dipyridamole-Thallium Scintigraphy and Gated Radionuclide Angiography to Assess Cardiac Risk before Abdominal Aortic Surgery

BACKGROUND Because many patients with atherosclerotic disease of the abdominal aorta also have coronary artery disease, assessment of cardiac risk before abdominal aortic surgery has received much attention. Our prospective study was designed to identify predictors of cardiac risk in consecutive patients evaluated preoperatively with dipyridamole-thallium single-photon-emission computed tomography (SPECT) to assess myocardial perfusion and radionuclide angiography to measure left ventricular ejection fraction. METHODS Clinical and scintigraphic data were collected prospectively during hospitalization in 457 consecutive patients undergoing elective abdominal aortic surgery. Adverse cardiac outcomes were predicted with multivariate analyses. RESULTS Eighty-six patients (19 percent) had one or more of the following postoperative complications: prolonged myocardial ischemia (61 patients), myocardial infarction (22), congestive heart failure (20), and severe ventricular tachyarrhythmia (2). Twenty patients died postoperatively (4.4 percent), half of them from cardiac causes. Information about myocardial perfusion obtained from dipyridamole-thallium SPECT did not accurately predict adverse cardiac outcomes. The best correlates of cardiac complications were definite clinical evidence of coronary artery disease (odds ratio, 2.6; 95 percent confidence interval, 1.6 to 4.3) and age greater than 65 years (odds ratio, 2.3; 95 percent confidence interval, 1.4 to 3.6). Measurement of the ejection fraction was useful only in the prediction of left ventricular failure. Age greater than 65 years was the only predictor of death (odds ratio, 26.4; 95 percent confidence interval, 3.5 to 200.0). CONCLUSIONS The presence of definite clinical evidence of coronary artery disease and older age were the most important preoperative predictors of an adverse cardiac outcome after abdominal aortic surgery. These results suggest that the routine use of dipyridamole-thallium SPECT and radionuclide angiography for screening before abdominal aortic surgery may not be justified.

The Pharmacokinetics and Tolerability of an Intravenous Infusion of the New Hydroxyethyl Starch 130/0.4 (6%, 500 ml) in Mild-to-severe Renal Impairment

Hydroxyethyl starches (HES) are almost exclusively excreted glomerularly, in part after hydrolysis by amylase. HES 130/0.4 (Voluven®; Fresenius Kabi Deutschland GmbH, Bad Homburg, Germany) was developed to improve pharmacokinetics whereas preserving the efficacy of volume effect. We studied the dependency of pharmacokinetics of HES 130/0.4 on renal function. Nineteen volunteers with stable, non-anuric renal dysfunction, ranging from almost normal creatinine clearance (CLcr) to severe renal impairment (mean CLcr: 50.6 mL · min−1 · 1.73 m−2), were given a single infusion of 500 mL 6% HES 130/0.4 over 30 min. HES plasma concentrations were determined until 72 h, urinary excretion until 72–96 h. CLcr had been obtained at least twice before and twice after dosing. Standard pharmacokinetic calculations and regression analysis were performed. Area under the time concentration curve (AUC0–inf) clearly depended on renal function comparing subjects with CLcr <50 with those with CLcr ≥50 (ratio 1.73). Peak concentration (Cmax, 4.34 mg/mL) as well as terminal half-life (16.1 h, model independent) were not affected by renal impairment. At CLcr ≥30, 59% of the drug could be retrieved in urine, versus 51% at CLcr 15–<30. The mean molecular weight of HES in plasma was 62,704 d at 30 min, showing lower values with increased renal impairment (P = 0.04). Pre-dose amylase concentrations inversely correlated with baseline CLcr. Residual HES plasma concentrations after 24 h were small in all subjects (≤0.6 mg/mL). We conclude that HES 130/0.4 (500 mL 6%) can be safely administered to patients even with severe renal impairment, as long as urine flow is preserved, without plasma accumulation.

Continuous infusion of remifentanil and target-controlled infusion of propofol for patients undergoing cardiac surgery: a new approach for scheduled early extubation.

OBJECTIVE To assess hemodynamic stability, postoperative pain management, and the control and timing of early extubation of a total intravenous anesthetic technique using propofol target-controlled infusion (TCI) and remifentanil in cardiac surgery. DESIGN Prospective study. SETTING University hospital. PARTICIPANTS Fifty patients scheduled for elective cardiac surgery. INTERVENTIONS Premedication consisted of oral midazolam, 0.1 mg/kg. Anesthesia was induced with propofol TCI at a target concentration of 1.5 to 2 microg/mL; remifentanil, 1 microg/kg; and rocuronium. Anesthesia was maintained with propofol at the same target concentration and remifentanil titrated between 0.25 and 1 microg/kg/min. Thirty minutes before the end of surgery, a 0.1-mg/kg bolus of morphine was administered intravenously. Postoperative sedation was achieved by maintaining the propofol infusion until the patient was deemed ready for extubation. Postoperative pain relief was evaluated using a visual analog scale. The intervals between arrival in the intensive care unit, spontaneous ventilation, and extubation were recorded. MEASUREMENTS AND MAIN RESULTS Included in this study were 36 men and 14 women (American Society of Anesthesiologist = III; New York Heart Association = II) scheduled for cardiac surgery. All patients remained hemodynamically stable throughout the perioperative period. Thirty-seven patients were successfully extubated during the first 4 postoperative hours. Spontaneous breathing was achieved at a mean interval of 15+/-5 minutes after propofol discontinuation. The mean interval to extubation was 163+/-45 minutes after arrival in the intensive care unit. Extubation was performed 48+/-12 minutes after patients were considered ready to awaken. During spontaneous ventilation, 36 patients received additional boluses of morphine (mean, 2.5+/-1 mg). Subsequently, all patients achieved a visual analog scale less than 40 mm. CONCLUSION The combination of remifentanil and propofol TCI resulted in hemodynamic stability and good postoperative analgesia. This technique allows physicians to schedule the time of extubation in patients undergoing cardiac anesthesia.

Effects of Propofol and Thiopental on Coronary Blood Flow and Myocardial Performance in an Isolated Rabbit Heart

BackgroundSome clinical and experimental studies suggest that propofol decreases myocardial contractility and relaxation, whereas others report preserved cardiac function. To investigate the effects of propofol on intrinsic contractility and relaxation, increasing concentrations of propofol were infused in isolated blood-perfused rabbit hearts. Equimolar concentrations of thiopental were infused as a reference group. MethodsCoronary blood flow, left ventricular contractility and relaxation (as maximal positive and negative left ventricular pressure derivatives [dP/dtmax and dP/dtmin], respectively), and myocardial oxygen consumption (MvO2) were measured during infusion of 10–1,000 μM propofol in bloodperfused hearts. To determine whether the effects of propofol depend on the hearts perfusate, propofol also was infused in isolated buffer-perfused rabbit hearts. In addition, the effects of propofol solvent were investigated in blood- and buffer-perfused preparations. ResultsIn blood-perfused preparations, coronary blood flow increased with propofol concentrations greater than 30 μM and with 300 and 1,000 μM thiopental. Left ventricular dP/dtmax and dP/dtmin remained unchanged with propofol and decreased with concentrations of thiopental equal to or greater than 30 μM. MvO2 increased with 1,000 μM propofol, whereas coronary venous oxygen tension and content remained unchanged. MvO2 decreased with thiopental associated with a significant increase in coronary venous oxygen tension and content. In six buffer-perfused hearts, basal coronary blood flow was much greater and MvO2 less than in blood-perfused hearts. Left ventricular dP/dtmax and dP/dtmin decreased with 30, 100, and 300 μM propofol. Propofol vehicle did not change coronary blood flow, myocardial performance, or MvO2 of blood- or buffer-perfused hearts. ConclusionsWhen compared to a reference drug such as thiopental, propofol did not depress the myocardial performance of blood-perfused rabbit hearts. The type of the perfusate (blood vs. buffer), however, had a major influence on the myocardial effects of propofol.

The effect of universal leukodepletion of packed red blood cells on postoperative infections in high-risk patients undergoing abdominal aortic surgery

We evaluated, by using a before-and-after study, the influence of leukoreduction by filtration on postoperative infections and adverse outcomes in patients undergoing elective major aortic surgery. From January 1995 to October 2000, all patients who underwent elective abdominal aortic surgery were included in the analysis. Before the introduction of systematic leukodepletion of packed red blood cells (RBCs), on April 1, 1998, 192 patients received standard or buffy-coat-depleted packed RBCs. Then, 195 patients were transfused with exclusively filtered leukodepleted packed RBCs. No major significant difference was observed between the groups of patients with regard to preoperative cardiac and pulmonary status, anesthetic and surgical techniques, or transfusion policy. No significant difference in mortality was observed between the two groups. The incidence of postoperative infections was 31% (95% confidence interval, 25%–38%) in the Control group versus 27% (95% confidence interval, 21%–33%) in the Leukodepleted group; severe infectious complications and pneumonia were not significantly different between the two groups of patients. Cardiovascular and respiratory outcomes were not significantly different between the groups. Data from this study suggest that the effect of using leukodepleted RBC on postoperative infections is not of obvious importance.

Mechanisms of increased myocardial contractility with hypertonic saline solutions in isolated blood-perfused rabbit hearts

Hypertonic saline improves organ perfusion and animal survival during hemorrhagic shock because it expands plasma volume and increases tissue oxygenation.Because both decreased and increased myocardial performance have been reported with hypertonic saline, the effects of hyperosmolarity and the mechanism accounting for it were investigated in isolated blood-perfused rabbit hearts. Coronary blood flow (CBF), myocardial contractility, relaxation, and oxygen consumption were measured during administration of blood perfusates containing 140-180 mmol sodium concentrations ([Na+]). In two other series of experiments, the role of Na+-Ca2+ exchange in the inotropic effect of hyperosmolarity (160 mmol sodium concentration) and hypertonicity (sucrose) were also investigated. Hypertonic [Na+] induced a significant increase in contractility and relaxation, combined with a coronary vasodilation. Myocardial oxygen consumption (MvO2) increased at all hypertonic [Na+] without significant change in coronary venous oxygen tension (PvO2) and content (CvO2). Amiloride (0.3 mmol) inhibited the improved contractility observed with 160 mmol sodium. Similar Na+-Ca2+ exchanger blockade did not inhibit the inotropic effect of sucrose. These results confirm the positive inotropic effect of hypertonic [Na+]. The inhibition of this improvement by amiloride suggests that calcium influx through the sarcolemna could be the major mechanism of this effect. (Anesth Analg 1995;81:777-82)

Comparison of the acute hemodynamic effects of hypertonic or colloid infusions immediately after mitral valve repair

OBJECTIVE To determine the acute hemodynamic effect of hypertonic saline and/or colloid solutions as volume resuscitation in postoperative mitral valve repair patients. DESIGN Prospective, randomized trial. SETTING Postoperative cardiac intensive care unit of Broussais Hospital. PATIENTS Twenty-six patients who underwent mitral valve repair were prospectively studied. Two patients were excluded during the study. INTERVENTIONS During the immediate postoperative period, when wedge pressure decreases to <8 mm Hg, patients were randomly assigned to receive 250 mL of either hypertonic saline 7.2%-hydroxyethyl starch 6% (molecular weight, 200,000; hydroxyethylation ratio, 0.5) solution (HS-HES group), hypertonic saline 7.2% solution (HS group), or hydroxyethyl starch 6% solution (HES group). The infusion was completed within 15 mins. No additional volume was infused throughout the study. MEASUREMENTS AND MAIN RESULTS Standard hemodynamic measurements and echocardiographic data demonstrated that HS-HES and HS induced a higher increase in left ventricular end-diastolic area than HES. In the HS-HES and HS groups, systemic vascular resistances decreased significantly and end-systolic area tended to decrease. In the HES group, systemic vascular resistances did not change and end-systolic area tended to increase. Accordingly, ejection fraction increased significantly by 21% and 18% with HS-HES (from 50.5 +/- 5.5 to 61.2 +/- 4.8) and HS (from 49.7 +/- 3.6 to 58.8 +/- 3.3), respectively, and did not change with HES. A major increase in cardiac index was observed after hypertonic solutions infusion, from 2.9 +/- 0.3 to 4.1 +/- 0.4 L/min/m2 in the HS-HES group and from 2.7 +/- 0.3 to 3.8 +/- 0.4 L/min/m2 in the HS group. Then, cardiac index progressively returned to baseline values within the 3 hrs after the infusion. No significant difference was observed between HS-HES and HS. In these groups, plasma sodium increased significantly after the infusion and remained higher than baseline values throughout the study. Adverse events were observed only with hypertonic solution administration: hypotensive episodes, sudden increases in pulmonary capillary wedge pressure, and ventricular arrhythmias. These side effects are likely attributable to a too-high dose and/or rate of infusion. All patients included in the study were discharged from the hospital before the 10th postoperative day. CONCLUSION We conclude that in patients who have undergone mitral valve repair, postoperative infusion of hypertonic saline solutions increases left ventricular preload and left ventricular ejection fraction. The use of these hypertonic solutions may be of interest in patients with valvular cardiomyopathy. A titrated dose and a low rate of infusion may substantially improve the safety.

Reversal of Intraoperative Myocardial Ischemia with a Hemoglobin-based Oxygen Carrier

THE hemoglobin-based oxygen-carrying solutions currently under investigation have oxygen transport and exchange properties similar to blood. However, their cardiovascular effects are still a subject of controversy. In particular, there have been several reports of extensive vasonconstriction, 1-4 and several authors have suggested that this effect may be deleterious for the myocardium in patients with coronary artery disease. 5,6

Aprotinin to decrease bleeding and intraoperative blood transfusion requirements during descending thoracic and thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass.

The purpose of this retrospective study was to assess the efficacy of aprotinin, an antifibrinolytic agent, in reducing bleeding and blood transfusion requirements in patients undergoing descending thoracic or thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass (CPB). Sixty-nine consecutive patients underwent thoracic or thoracoabdominal aneurysmectomy using CPB in a 2-year period. None of the 29 patients operated on in 1990 (group 1) received aprotinin, whereas all 40 patients operated on in 1991 (group 2) were placed on a high-dose regimen of aprotinin. There were no significant differences between the two groups. Administration of aprotinin was associated with a decrease in CPB time (p=0.02), surgical duration (p=0.05), and intraoperative blood loss (p=0.008) as well as a reduction in intraoperative packed red cells (p=0.01), Cell-Saver units (p=0.05), fresh-frozen plasma units (p=0.002), and platelet concentrate (p=0.01) requirements. These data suggest that aprotinin is effective in reducing bleeding and blood transfusion requirements during descending thoracic or thoracoabdominal aortic aneurysmectomy using CPB.