Standard preoperative assessment for cardiac surgery will be done for all patients. Premedication will be given according to standard protocol in our university hospitals as follow bromazepam 3mg oral and ranitidine 150 mg orally in the night-before then another dose of ranitidine 150 mg 2 hours before arrival in operating theatre by small sips of clear liquid.~On arrival to induction room wide bore IV access will be inserted using local anesthetic then arterial cannula in radial artery will be inserted the same manner using local anesthetic then in operating room routine monitoring including a five-lead electrocardiogram, pulse oximeter and invasive blood pressure will be attached.~Anesthesia will be induced with midazolam 0.02 mg/kg and fentanyl 2-5 mcg/kg and muscle relaxation will be achieved by cis-atracurium 0.15 mg/kg. After tracheal intubation, central venous line and transesophageal echocardiography will be inserted, then anesthesia will be maintained throughout the procedure with morphine 20 mcg/kg/min, cis-atracurium 2 mcg/kg/min and sevoflurane 0.4% - 2% MAC. Ventilation will be adjusted to maintain end-tidal carbon dioxide in the range of 30-40 mmHg.~During cardiopulmonary bypass, flow of 2.2 l/min/m2 will be achieved, 20 ml/kg cold blood cardioplegia will be given manually and pressure controlled at 20 - 30 min interval along with hot shot at start of weaning from CPB, temperature will be maintained at 32-34℃ and propofol 1% infusion at rate of 8 - 12ml/hr.~In initial TEE study, baseline measures will be taken assessing left ventricular ejection fraction, and right ventricular hemodynamics represented by right ventricular function measured by [tricuspid annulus plane systolic excursion, fractional area changes, and right ventricular systolic pressure by doppler] also, pulmonary vascular resistance and systemic vascular resistance will be calculated, plus patients hemodynamics (mean arterial blood pressure, heart rate) and inotropic score all measures will be recorded.
This prospective double blinded 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.