Inhaled Versus Intravenous Milrinone for Patients Undergoing Mitral Valve Replacement Surgery

This prospective open-label randomized study aims to compare the effect of inhaled versus intravenous milrinone on the pulmonary vascular resistance in patients undergoing mitral valve replacement surgery. The primary outcome is to determine change in pulmonary artery pressure. The secondary outcomes include, * Incidence of systemic hypotension. * Hemodynamic affection and need of vasopressors and inotropes. * Change in pulmonary vascular resistance versus systemic vascular resistance. * Right ventricular function. * Duration of mechanical ventilation. * Need for mechanical circulatory support devices. * Urine output * Length of intensive care (ICU) in stay. As the investigators hypothesize that inhaled milrinone has a selective pulmonary vasodilator effect devoid of the systemic hypotension with the intravenous administration.

All patients underwent standard preoperative cardiac surgery assessment. Premedication included bromazepam and ranitidine, given the night before and 2 hours prior to arrival to OT. On arrival, IV access and arterial cannula were inserted under local anesthesia, along with routine monitoring electrocardiogram (ECG), pulse oximetery (SpO2), and IBP. Anesthesia was induced with midazolam, fentanyl, and cis-atracurium. After tracheal intubation, ultrasound (US) guided- central venous catheter (CVC) was inserted and TEE also applied and then anesthesia maintained with morphine, cis-atracurium infusions, and sevoflurane. Mechanical ventilation was set to maintain end-tidal carbon dioxide (etco2) in the range of 30-40 mmHg using lung protective ventilation strategies. During CPB, flow of 2.2 L.min-1.m-2, a custodiol cardioplegia was given, temperature kept at 28-32℃ and anesthesia maintained by sevoflurane- through a vaporizer mounted on CPB machine-. A senior consultant certified cardiac anesthetist conducted a baseline TEE using Philips EPIQ CVxi echocardiography machine. Baseline measures included left ventricular ejection fraction (LVEF), and RV function represented by tricuspid annulus plane systolic excursion (TAPSE), fractional area changes (FAC), and right ventricular systolic pressure (RVSP) by doppler also, PVR and systemic vascular resistance (SVR) was calculated, plus patients hemodynamics (mean arterial blood pressure (MAP), heart rate (HR)), all measures were recorded.