Cardiac arrhythmias produced by bretylium in cats anesthetized with halothane

Bretylium given by rapid intravenous injection into cats anesthetized solely with halothane precipitates severe and unusually long-lasting ventricular arrhythmias. They are observed 20-70 sec following doses of bretylium ranging from 0.8 mg/kg to 15 mg/kg and last for 60 sec to just over half an hour. Bretylium also manifests signs of sympathetic involvement since it raises blood pressure and heart rate just prior to the onset of arrhythmias. Propranolol pretreatment prevents bretylium arrhythmias. From these results and from those of other investigations, it is concluded that bretylium arrhythmias are mediated through the release of endogenous noradrenaline stored in adrenergic neurons of the heart. These results call attention to the arrhythmogenic potential of bretylium in the presence of halothane anesthesia.

A birth-life-death model for planning and evaluation of health services programs

A Markov model of the birth-life-death process is developed to relate two input decision variables—specific mortality rates by age and group of diseases and specific fertility rates by age—to output criteria involving life expectancy, time-dependent structure of mortality by age and cause of death, and other time-dependent demographic structures. Experimentation in the form of computer simulation is used to determine the input of health services programs in terms of the output criteria when the cost of a program and its estimated alteration of the input variables are known.