How a patent ductus arteriosus effects the premature lamb's ability to handle additional volume loads.
A model of patent ductus arteriosus in premature lambs was created to examine the lamb's ability to handle the volume load imposed by a patent ductus arteriosus and to determine the lamb's ability to handle any additional volume load. Fifteen preterm lambs [133 +/- 2 (+/- SD) days gestation, term 145 days], whose ductal diameter could be regulated with a mechanical occluder, were studied to determine the independent effects of ductus patency and a saline volume load (50 ml/kg over 3 min) on left ventricular output and its distribution. During a saline infusion, preterm lambs with a closed ductus could only increase their stroke volume by 40% above baseline stroke volume. When challenged with a saline infusion, lambs with an open ductus still were able to increase their stroke volume significantly; the maximal increase in stroke volume during the saline load with the ductus open was 70% above baseline stroke volume. We hypothesize that the associated reduced left ventricular afterload plays a significant role in the preterm lamb's ability to increase its stroke volume when challenged with a patent ductus arteriosus. Even with a patent ductus arteriosus, the lamb still has the ability to handle additional volume loads.
Cardiovascular Research Institute, San Francisco, California.
R I
RI
Clyman
C
C
Roman
M A
MA
Heymann
F
F
Mauray
D000818:Animals; D000831:Animals, Newborn; D001810:Blood Volume; D002302:Cardiac Output; D004374:Ductus Arteriosus, Patent / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D007231:Infant, Newborn; D007235:Infant, Premature, Diseases / Q000503:physiopathology*; D009200:Myocardial Contraction; D012756:Sheep