Intravenous Levosimendan versus Milrinone: Coronary Sinus Lactate and PA Catheter Derived Parameters in Patients with Pulmonary Hypertension Undergoing Elective Mitral Valve Replacement.

Background: Coronary sinus (CS) lactate level has been shown to corroborate with changes in myocardial metabolism induced by ischaemia and reperfusion, and hence can be used to indicate the effect on myocardial metabolism. In patients with mitral stenosis (MS) undergoing valvuloplasty or valve replacement, presence of severe pulmonary hypertension (PH), indicates advanced disease state and development of right ventricular (RV) failure, an important hallmark of bad prognosis. Levosimendan and milrinone are increasingly being used as inodilators to treat PH and improve RV function to varying degrees, but their effect on myocardial metabolism awaits precise validation.

Methods: Thirty patients were randomized into two groups of 15 patients each. Group L (received levosimendan) and Group M (received milrinone). All the patients received fentanyl (8-10 μg/kg), rocuronium bromide 0.8 mg/Kg for induction and maintenance of anaesthesia. In addition to the routine intravenous and invasive arterial access, a Cavafix® (Certo® 257, 45 cm, B Braun Melsungen AG, Germany) was inserted via right IJV and positioned in the right atrium (RA) to be later re-positioned in the CS before coming off cardiopulmonary bypass (CPB), to obtain blood samples for measuring the CS lactate levels postoperatively. At the commencement of rewarming, group L received levosimendan 10 μ/kg bolus over 10 min, followed by an infusion (0.1 μ/kg/min) and group M received 50 μg/kg bolus over 10 min, followed by infusion (0.5 μg/kg/min), till 24 hours post-operatively. CS lactate, heart rate (HR), mean arterial pressure (MAP) and PA catheter derived data [Cardiac index (CI), cardiac output (CO), PA pressure, systemic and pulmonary vascular resistance indices (SVRI/PVRI)] and mixed venous oxygen saturations (SvO2) were recorded at predetermined time points.

Results: In both the groups the CS lactate levels increased gradually till 6 hours after surgery followed by a decrease at 24 hours. Comparison of CS lactate between the two groups revealed that the CS lactate levels were significantly lower in group L at various time points till 24 hours after surgery with a P value of < 0.05. HR and MAP were comparable in both the groups at all time points. MAP was significantly lower in the two groups, both after induction of anaesthesia and after CPB. 7 patients in group M (46.7%) developed hypotension (MAP decreased by > 20% of baseline) that was treated with norepinephrine. CO increased significantly in both group M and group L, post CPB 10 min after surgery. Patients in group L had a significantly higher CO and CI, compared to group M, P < 0.05. PAP was significantly reduced compared to baseline values after valve replacement in both the groups being lower in group L compared to group M, but the difference was statistically not significant. After valve replacement, SVRI decreased significantly in both the group the decrease being significantly more in group L (P < 0.05).

Conclusion: This study revealed that, in comparison to milrinone, levosimendan was associated with comparable reduction in systolic and mean pulmonary artery pressure, lesser incidence of hypotension, lesser requirement of inotropic support and better myocardial performance.