Respiratory and cardiovascular alterations during the process of anoxic death in the newborn

Abstract

A systematic investigation was conducted during the process of anoxic death in newborn pups, rabbits and kittens less than 24 hr. old. Simultaneous measurements of respiration, heart rate and blood pressure were made. Considerable individual variation in the respiratory responses of newborn animals breathing nitrogen was noted. Under hypoxic conditions, respiratory failure may follow circulatory failure in the adult, whereas in the newborn, respiratory failure always occurred long before circulatory failure. The effect of anoxia on the cardiovascular system of the newborn at the time of the last breath was not as pronounced as might have been anticipated. Great individual differences with respect to blood pressure and heart rate throughout the period of anoxia were noted. The systolic blood pressure, on the average, was seen initially to fall more rapidly than the diastolic blood pressure or heart rate; it then slowly tapered off. The circulatory system was noted to function, although at hypotensive levels, for long periods of anoxia. Submitted on June 29, 1959

Failure of autoresuscitation in weanling mice: significance of cardiac glycogen and heart rate regulation

“…Although gasping, which originates in the brain stem and is dependent on anaerobic metabolism, can persist for a limited time in the absence of brain perfusion, sufficient pulmonary and systemic circulation is required to transport oxygenated blood to the heart and brain for recovery of normal functions. This conclusion is supported by the oftenrepeated observation that successful autoresuscitation, or for that matter artificial resuscitation by mechanical ventilation, requires a small but definable level of heart function as reflected in systolic blood pressure (1,6,7,16,34,38,39). Thus, in successful autoresuscitation, respiratory and cardiovascular functions are coordinated and interdependent.…”

Studies on the Effect of Acute Asphyxia on the Fetal Pig <i>in utero</i>

“…Most studies on neonatal asphyxia have been made on 'newborns' exposed to N2 or N2 + C 02 mixtures at temperatures similar to those in utero (4,16,24), asphyxia upon delivery (3,8), asphyxiation of the exposed fetus by cord occlusion (9) or reduction in maternal 0 2 (2); variations between methods have been dis cussed previously (7). A preliminary study in dicated that asphyxia at delivery of the neonatal pig would be difficult to control and that the sow is not a good candidate for prolonged local anesthesia.…”

Respiration

“…The well-known rise in blood hemo globin concentration is apparently the more important adaptive response in the mature animal, but it is interesting that in the developing chick exposed to different environmental oxygen tensions, the hemoglobin concentration in all groups was the same (9) . Adult animals are known to withstand hypoxic conditions less well than infants, and this has been confirmed in new studies on dogs, rabbits, kittens (60), and rats (85). For some reason, increase in blood fat level results in a fall of arterial oxygen saturation which is more pronounced at high altitude (257).…”