Cardiac responses to autonomic nerve stimulation during acidosis and hypoxia in the lamb

Downing, S. E.; Milgram, E.; Halloran, KH

doi:10.1152/ajplegacy.1971.220.6.1956

Cited by 12 publications

(4 citation statements)

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“…First, there were no significant changes in heart rate during the volume infusion, despite the fact that baroreceptors have been shown to be capable of altering fetal heart rate (34,35). Even though baroreceptors can influence fetal heart rate, they have little effect on cardiac output in the fetus (10) and newborn (36). Increases in blood volume in adult animals produce marked increases in cardiac output that are only partially dampened by the baroreceptor system.…”

Section: Discussionmentioning

confidence: 99%

How a Patent Ductus Arteriosus Effects the Premature Lamb's Ability To Handle Additional Volume Loads

et al. 1987

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ABSTRACT. 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 I133 -C 2 ( 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. W e 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. (Pediatr Res 22: 531-535, 1987) Abbreviations PDA, patent ductus arteriosus LV, left ventricle QLV, left ventricular output Q pulmonary, pulmonary blood flow Q ductus, ductus arteriosus blood flow Q systemic, systemic blood flow R pulmonary, pulmonary vascular resistance R systemic, systemic vascular resistance R ductus, ductus arteriosus resistance R total, total resistance Hbg, hemoglobin GI, gastrointestinalThe PDA represents a significant stress on the premature cardiovascular system. The extent of this stress depends both on the magnitude of the left to right shunt through the PDA and on the ability of the cardiovascular system to adjust to that shunt. Full-term newborn lambs respond to volume loading with a limited increase in stroke volume, compared with adult sheep. The left ventricle of the full-term newborn lamb is capable of developing greater force than the left ventricle of the preterm lamb (with closed ductus) at comparable filling volume and resistance (6). Several studies have shown that the fetal lamb has a limited ability to increase its stroke volume above its baseline value during an acute volume load (8-12).The limited ability of the developing left ventricle to increase its output during a volume load is caused by some degree of myocardial immaturity (13) as well as by the high resting output needed to supply the demand for oxygen after delivery (14). The high resting level of performance demanded of the newborn heart may exhaust any reserve pumping capacity. The purpose of our study was both to examine the premature lamb's ability to handle the volume load imposed by a PDA and to see how the presence of a PDA alters the lamb's ability to tolerate any additional volume load. METHODSPreparafion. Fifteen mixed breed western time-dated pregnant ewes at 128-133 days ge...

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Section: Discussionmentioning

confidence: 99%

How a Patent Ductus Arteriosus Effects the Premature Lamb's Ability To Handle Additional Volume Loads

et al. 1987

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“…Samples of arterial blood (0.5 ml) were taken hourly for blood gas and pH determinations in a Radiometer electrode assembly. As in our previous studies (Buckley et al, 1976;Reddy et al, 1974), blood gas composition was controlled by varying the depth of ventilation to preclude depression of cardiac effects of catecholamines by hypercarbia and acidosis (Downing et al, 1971) or release of catecholamines by hypoxia (Jones and Robinson, 1975). Decamethonium bromide (Burroughs-Wellcome Co.) was administered in doses of 0.5-1.0 mg/ kg to minimize muscle tremor artifacts on ECG and flowmeter recordings.…”

Section: Animal Preparationsmentioning

confidence: 99%

Age-related cardiovascular effects of catecholamines in anesthetized piglets.

Buckley¹,

Gootman²,

Yellin³

et al. 1979

Circulation Research

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SUMMARY We studied cardiac and peripheral circulatory effects of graded doses of catecholamines (0.05-1.0 fig/kg) in piglets aged £ 1 day, 2-4 days, 1 week, 2 weeks, and 2.5-3 months, under anesthesia with pentobarbital. We evaluated cardiovascular function from simultaneous recordings of aortic pressure, ventricular pressure and its first derivative, heart rate, and phasic carotid and femoral blood flows. We calculated vascular resistance as the ratio of mean aortic pressure to mean flow. The age of onset of a given cardiovascular response was determined, and magnitudes of each type of response were compared among the age groups. Norepinephrine elevated the blood pressure at all doses in piglets of all ages, elicited reflex bradycardia only in older piglets, and increased carotid resistance. Epinephrine elevated the blood pressure at all doses in piglets less than 1 week old, but low doses lowered the blood pressure in piglets older than 1 week of age; resistance changes in the femoral and carotid circulations were variable except in the 2.5-3 month age group. Isoproterenol increased cardiac contractility at all doses in piglets of all ages and increased heart rate at low doses in piglets older than 2 days of age; however, blood pressure and femoral resistance decreases were age and dose dependent. There were age-related differences in the catecholamine dose required to elicit a given cardiac or peripheral circulatory effect and age-related differences in the direction and magnitude of such effects. These results provide evidence for differing rates of postnatal maturation of cardiovascular or-and /}-adrenergic mechanisms in swine. Ore Re* 45: 282-292, 1979

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“…An effect of acidosis on left ventricular function has been observed by Downing et al (1966aDowning et al ( , 1966bDowning et al ( , 1969 and an apparently unresponsive heart were observed in this study . Ng et al (1967), Linden and Norman (1969), and Downing et al (1971 ) have reported that acidosis potentiates vagal slowing of the heart and this may partially explain the lower heart rates late in the experiments. Downing and Siegel (1963) Wiggers (1950) to contribute to a more rapid reuptake of shed blood and subsequent irreversible collapse of the animals.…”

Section: Results Of the Shock Experimentssupporting

confidence: 66%

Production and bioassay of an endogenous myocardial depressant

Terry

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PRODUCTION AND BIOASSAY OF A MYOCARDIAL DEPRESSANT IN SHOCK PLASMA 8 Introduction 8 Methods: Hemorrhagic Shock Experiments 9 Results of the Shock Experiments 15 Discussion 26 Methods: Bioassay of the Shock Plasma 29 Results and Discussion 45 ASSESSMENT OF A MYOCARDIAL DEPRESSANT SUBSTANCE IN CANINE HOMOGENATES 62 Introduction 62 Methods for Homogenation and Processing of the Canine Pancreas 64 Methods for the Isometric Screen of Chromatographed Peaks 71 Results of the Bioassay of the Individual Chromatographed Peaks 74 Conclusions 92 EFFECTS OF TEMPERATURE ON THE ISOMETRIC CONTRACTION OF CANINE PAPILLARY MUSCLES 94 Introduction 94 Methods: Examination of the Effects of Temperature 95 Results and Discussion 97 iii

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Cardiac responses to autonomic nerve stimulation during acidosis and hypoxia in the lamb

Cited by 12 publications

References 0 publications

How a Patent Ductus Arteriosus Effects the Premature Lamb's Ability To Handle Additional Volume Loads

How a Patent Ductus Arteriosus Effects the Premature Lamb's Ability To Handle Additional Volume Loads

Age-related cardiovascular effects of catecholamines in anesthetized piglets.

Production and bioassay of an endogenous myocardial depressant

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