Hemodynamic effects of the new calcium sensitiser levosimendan in cardiosurgical ICU patients

Introduction

The aim of the study was to determine the hemodynamics and clinical effects of levosimendan (LS) in cardiosurgical patients. LS enhances the contractile function of stunned myocardium without increasing concetrations of intracellular calcium and myocardial oxygen consumption.

Methods

Ten patients (age 71 ± 6 years) mechanically ventilated and sedated were included in this study (n = 10). Diagnosis was coronary artery bypass operation (n = 7), valve replacement (n = 1) and pulmonary edema (n = 2). Patients were prospectively selected to receive LS, if hemodynamic data measured by a pulmonary artery catheter and estimation of cardiac function by echocardiography indicated a need for positive inotropic support. The infusion rate of LS was 0.1–0.2 μg/kg/min. A pre-existing infusion with epinephrine or norepinephrine was titrated to maintain a mean arterial pressure of 65–100 mmHg. Crystalloids and colloids were administered to maintain pulmonary capillary wedge pressure (PCWP) > 14 mmHg. Measurements were obtained at baseline, 3 hours and 24 hours after starting LS infusion. Statistical analysis was performed with a paired t test. P < 0.005 was considered statistically significant.

Results

LS caused a significant increase in cardiac index (CI) from 2.2 ± 0.4 l/min/m² at baseline to 3.3 ± 0.5 l/min/m² after 24 hour infusion. The increase in CI was due mainly to increase in stroke volume, as the heart rate remained nearly unchanged during the study period. The stroke volume index increased from 22.9 ± 4 ml/m² to 33.9 ± 9 ml/m² (P < 0.005). The left ventricular ejection fraction, as estimated by echocardiography, increased from 29.5 ± 5.5% to 33.9 ± 9% (P = 0.001). The systemic vascular resistance index significantly decreased from 2539.5 ± 551.4 dyn/s/cm^-5/m² to 1791.5 ± 276 dyn/s/cm^-5/m² (P < 0.005). LS did not cause significant changes in pulmonary vascular resistance (PVRI at baseline 318.5 ± 104 dyn/s/cm^-5/m², after 24 hours 293 ± 136 dyn/s/cm^-5/m²). There was a fall in PCWP, although this was not significant.

Conclusion

In this study the effects of a new calcium sensitiser were evaluated after cardiac surgery. The study demonstrates that LS exerts favourable hemodynamic responses in these patients, without increasing myocardial oxygen consumption. LS has the potential to treat low cardiac output states after cardiopulmonary bypass surgery and its use in these situations might be of special value.