No abstract

Propylene glycol accumulated significantly in pediatric intensive care patients receiving continuous lorazepam infusion, and propylene glycol concentration correlated with the cumulative lorazepam dose the patient received. However, significant laboratory abnormalities due to propylene glycol accumulation were not observed.

To evaluate combination therapy of mild to moderate bronchiolitis with bronchiodilators and corticosteroids, we treated 51 young children with first-time wheezing and symptoms of respiratory tract infection with albuterol plus either prednisolone or placebo for 5 days. Disease severity was scored on days 0, 2, 3, and 6. On day 2, prednisolone resulted in significantly lower scores (2.7 +/- 1.4 vs. 4.0 +/- 1.5 in all patients evaluated, p < 0.05) than placebo, whereas there was no detectable difference on day 6, suggesting that addition of prednisolone to albuterol transiently accelerates recovery from bronchiolitis. The clinical significance of this effect needs to be evaluated in further studies.

The effects of increasing the frequency of contraction on myocardial oxygen consumption per minute (MVo 2 ) were examined in eight dogs using an isovolumic left ventricular preparation. MVo 2 was determined at two to four levels of heart rate in each animal. Peak wall stress was maintained constant in each animal so that changes in it would not influence the effects of heart rate on oxygen consumption per beat. As heart rate was increased, there was a highly significant linear increase in MVo 2 . Oxygen consumption per beat was shown to be a negative linear function of the reciprocal of heart rate. Thus, as heart rate increased there was a significant increase in oxygen consumption per beat; when basal oxygen consumption was subtracted from total oxygen consumption, there was a much larger increase in oxygen consumption per beat. Myocardial contractile state, defined as the maximum observed contractile element velocity at the lowest common level of wall stress, was significantly increased by increasing heart rate. The data suggest that the increased M"v"o 2 associated with augmented heart rate is secondary to augmentation of contractile state, as well as to the increase in stress development per minute. ADDITIONAL KEY WORDSmyocardial metabolism inotropic state stress-velocity relation peak myocardial wall stress isovolumic left ventricular contractions• There is general agreement that increasing the frequency of contraction augments the inotropic or contractile state of the myocardium, as reflected by a shift of the force-velocity relationship, both in isolated cardiac muscle (1-3) and the intact heart (4, 5). Recently, it has been shown that the contractile state of the heart is an important determinant of myocardial oxygen consumption (6-9), and therefore, it might be expected that increasing the frequency of cardiac contraction would be