ABSTRACT
OBJECTIVE: Orientation-related bileaflet mechanical valve flow and velocity studies in the downstream area are limited in mitral valve replacement studies. METHODS: In five sheep, ventricular blood flow was visualized prior to the implantation of a mitral Edwards Mira Bileaflet Mechanical Valve Model 9600. The implant orientation was either anatomic, with a 45 degrees rotation, or anti-anatomic, with a 90 degrees rotation. Sheep were positioned within an 1.5T field strength MR scanner (Magnetom Sonata; Siemens) to assess time-dependent three-dimensional blood flow velocities displayed as color-encoded vectors. RESULTS: The preoperative ventricular velocity profiles presented negligible individual variances. Streamlines passed homogeneously without any spatial differences into the left ventricle. Starting from the anatomical position, the areas with inhomogeneous and accelerated local blood velocities increased in comparison to the preoperative status. Rotating the prosthesis until it was in a 45 degrees position caused a significant increase in turbulence immediately downstream; fluids stagnated longer at the apex. In the anti-anatomic orientation, mean velocities decreased. In all three positions, but less so in the anatomical position, the flow pattern of the blood helix at the apex was disturbed. The intraventricular flow patterns between prostheses in the three orientations were, however, not significant when compared to the differences between physiologic intraventricular flow and any of the postoperative measurements. CONCLUSIONS: To achieve optimal hemodynamics, rotation of the mitral valve has to be considered carefully, as has long been known from aortic valve replacement studies. To this end, a method for qualitative assessment of left ventricular blood flow patterns was developed.
Subject(s)
Heart Valve Prosthesis Implantation/methods , Heart Valve Prosthesis , Mitral Valve/physiology , Ventricular Function, Left/physiology , Animals , Blood Flow Velocity , Hemorheology , Magnetic Resonance Imaging/methods , Rotation , SheepABSTRACT
PURPOSE: Evaluation of the relationship between ethanol concentration in expired air and the amount of absorbed irrigation fluid in patients who undergo a transurethral resection of the prostate. METHODS: 76 patients were evaluated in a prospective study. The irrigation fluid contained 1.92 w/w% of ethanol. The ethanol concentration in breath was measured at least every 10 minutes with a Alcotest 7410 (Dräger) or a Biomed 3010 (Biotest). Documented values: breath ethanol concentration, mean arterial pressure, heart rate, haemoglobin concentration, serum sodium concentration, the amount of irrigation fluid, the time of operation, special events, therapeutic interventions. A modification of the Widmark formula was used for calculating the amount of absorbed irrigation fluid from the breath ethanol concentration. RESULTS: A rise of the ethanol level above 0.2/1000 was observed in 10 patients. No clinically significant difference in heart rate and blood pressure during surgery between the 24 patients with no alcohol in breath and the 10 patients with more than 0.2/1000 was observed. Prolonged duration of resection and greater amount of used irrigation fluid correlated with higher ethanol concentration in breath. During the study period no patient developed the clinical features of a transurethral resection syndrome. CONCLUSIONS: If 2 w/w% of ethanol is added to the irrigation fluid, breath ethanol concentration under 0.2/1000 may be considered harmless, while values above 0.2/1000 are predictors of massive absorption of irrigation fluid. In our patients, the addition of ethanol to the irrigation fluid has been a suitable and easy way to monitor the absorption of irrigation fluid, if the ethanol concentration in the breath is measured every ten minutes. If 2 w/w% of ethanol have been added to the irrigation fluid, the absorbed volume (E) can be estimated using the formula: E = 37.5 x body weight (kg) x ethanol concentration (/1000).
