Hydrodynamic evaluation of aortic cardiopulmonary bypass cannulae using particle image velocimetry.

The high velocity jet from aortic arterial cannulae used during cardiopulmonary bypass potentially causes a "sandblasting" injury to the aorta, increasing the possibility of embolisation of atheromatous plaque. We investigated a range of commonly available dispersion and non-dispersion cannulae, using particle image velocimetry. The maximum velocity of the exit jet was assessed 20 and 40 mm from the cannula tip at flow rates of 3 and 5 L/min. The dispersion cannulae had lower maximum velocities compared to the non-dispersion cannulae. Dispersion cannulae had fan-shaped exit profiles and maximum velocities ranged from 0.63 to 1.52 m/s when measured at 20 mm and 5 L/min. Non-dispersion cannulae had maximum velocities ranging from 1.52 to 3.06 m/s at 20 mm and 5 L/min, with corresponding narrow velocity profiles. This study highlights the importance of understanding the hydrodynamic performance of these cannulae as it may help in selecting the most appropriate cannula to minimize the risk of thromboembolic events or aortic injury.

Effects of extra-carbohydrate supplementation in the late evening on energy expenditure and substrate oxidation in patients with liver cirrhosis.

BACKGROUND: The purpose of this study was to demonstrate the effects of extra-carbohydrate supplementation before bedtime on energy metabolism and substrate oxidation in patients with liver cirrhosis. METHODS: Sixteen cirrhotic patients and eight control subjects were included in this study. To compare the effect of energy metabolism and substrate oxidation with or without a bedtime snack, indirect calorimetry was assessed at 7 to 8 AM after overnight fasting, following either dinner (6 PM) or a bedtime snack (11 PM) the evening before. The bedtime snack contained about 50 g of carbohydrate. The energy expenditure and substrate oxidation were calculated from the indirect calorimetry measurement and 24-hour urinary nitrogen excretion. RESULTS: In those who fasted since dinner, the respiratory quotient (RQ) was significantly lower in cirrhotic patients than in control subjects. Also, the energy utilized by cirrhotic patients was derived primarily from fat oxidation (58%), whereas the main energy source for controls was carbohydrate (55%). An extra-carbohydrate supplement before bedtime did not influence the indirect calorimetry measurement in the controls, but there were significant increases in both RQ and carbon dioxide production (Vco2) in cirrhotic patients. The extra-carbohydrate supplementation did not significantly change the absolute resting energy expenditure utilization in control subjects; however, the utilization of carbohydrate significantly increased with a decrease in fat and protein oxidation in the cirrhotic patients. CONCLUSIONS: These preliminary data suggest that extra-carbohydrate supplementation before bedtime can shorten nocturnal fasting with a more economic fuel utilization and effectively diminish fat and protein oxidation in cirrhotic patients.