Effects of milrinone versus epinephrine on left ventricular relaxation after cardiopulmonary bypass following myocardial revascularization: assessment by color m-mode and tissue Doppler.

OBJECTIVE: The purpose of this study was to evaluate the left ventricular lusitropic effects of epinephrine versus milrinone after cardiopulmonary bypass. DESIGN: Prospective randomized study. SETTING: Single institution, university teaching hospital. PARTICIPANTS: Adult patients undergoing coronary artery bypass grafting under cardiopulmonary bypass. INTERVENTIONS: After separation from cardiopulmonary bypass, patients were randomized to receive intravenous epinephrine by continuous infusion (0.03 microg/kg/min) or milrinone (50 microg/kg followed by 0.5 microg/kg/min). Transesophageal echocardiographic evaluation of left ventricular diastolic function, with emphasis on relaxation, was performed before and after bypass and after the administration of either epinephrine or milrinone. MEASUREMENTS AND MAIN RESULTS: Measurements included pulse-wave Doppler analysis of mitral inflow and pulmonary vein and left ventricular outflow tract velocities. Left ventricular inflow velocity of propagation measured with color M-mode and tissue Doppler assessment of early mitral annulus velocity were used to evaluate left ventricular relaxation. Values of velocity of propagation and mitral annulus velocity improved significantly after bypass, suggesting improved relaxation. The administration of either epinephrine or milrinone did not result in further improvement in left ventricular relaxation. CONCLUSIONS: After cardiopulmonary bypass, left ventricular relaxation was significantly improved. Neither epinephrine nor milrinone exhibited favorable lusitropic effects after bypass.

Oximetry-derived perfusion index for intraoperative identification of successful thoracic sympathectomy.

BACKGROUND: Endoscopic thoracic sympathectomy treats patients with hyperhidrosis. Laser Doppler flow and changes in palmar temperature have been advocated for intraoperative monitoring. The pulse oximetry-derived perfusion index (PI) is used to quantify pulsatile blood flow at the pulse oximeter. Upper limb sympathectomy is associated with increased flow to the ipsilateral extremity; thus we postulate that it will increase PI. We evaluated changes in intraoperative PI as a monitor of successful thoracic sympathectomy. METHODS: After institutional review board approval and informed consent, 10 adult patients undergoing bilateral endoscopic thoracic sympathectomy under general anesthesia were studied. Finger pulse-oximetry probes were placed on each hand, and reference probes on each earlobe. Hemodynamic variables and PI were continuously monitored. Data were collected immediately before and every minute after sympathectomy for 5 minutes. Anesthetic management remained constant throughout. A successful sympathectomy was defined by a twofold increase in PI on the ipsilateral arm. Data were analyzed with analysis of variance and Student's t tests; a p < 0.05 was considered significant. RESULTS: Baseline oximetric waveforms were adequate in all subjects. Right sympathectomy was associated with a 372% increase in PI (p < 0.0001), and left sympathectomy with a 316% increase in PI (p < 0.029). This occurred as early as 1 minute after transection of the sympathetic chain. The PI in the reference probes as well as the hemodynamics remained constant. All patients had postoperative resolution of their hyperhidrosis symptoms. CONCLUSIONS: In patients with hyperhidrosis of the upper extremity, the intraoperative PI derived from pulse oximetry is an additional indicator of successful thoracic sympathectomy.

Effects of a new phosphodiesterase enzyme type V inhibitor (UK 343-664) versus milrinone in a porcine model of acute pulmonary hypertension.

BACKGROUND: Perioperative pulmonary hypertension remains a clinical challenge. The phosphodiesterase enzyme type III inhibitor milrinone produces pulmonary vasodilation but lacks selectivity. Sildenafil, a phosphodiesterase enzyme type V inhibitor, can also induce relaxation of the pulmonary vasculature; however, only the oral formulation is presently available. This study evaluated the effects of a new intravenous sildenafil analogue--UK 343-664--compared with milrinone during acute pulmonary hypertension in a porcine model of thromboxane-induced pulmonary hypertension. METHODS: After acute pulmonary hypertension, 24 adult swine were randomized to 3 groups. Group 1 (n = 9) received an intravenous dose of 500 microg of UK 343-664, group 2 (n = 8) received milrinone 50 mg/kg, and group 3 (n = 7) received 10 mL of normal saline solution. All agents were administered for more than 5 minutes. Data were recorded continuously for 30 minutes. RESULTS: Both milrinone and UK 343-664 partially reversed thromboxane-induced pulmonary hypertension, with a notable decrease in mean pulmonary artery pressure and pulmonary vascular resistance and a concomitant increase in cardiac output. In addition, milrinone improved right ventricular contractility but produced marked systemic vasodilatation. In contrast, the administration of UK 343-664 was associated with pulmonary vasodilatation, without appreciable changes in systemic arterial pressure or vascular resistance. CONCLUSIONS: Milrinone and UK 343-664 were equally effective as pulmonary vasodilators; however, only UK 343-664 exhibited a high degree of pulmonary selectivity. Potential uses for this new phosphodiesterase enzyme type V inhibitor warrant further study.