Glucose Perturbation in Experimental Hyperviscosity

Leake, Rosemary D.; Chan, Gary M.; Zakauddin, Shereen; Dodge, Michael; Fiser, Robert H.; Bier, Dennis M.; Oh, William

doi:10.1203/00006450-198012000-00009

Cited by 14 publications

(3 citation statements)

References 18 publications

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“…Because the liver must obtain a significant portion of its oxygen delivery from portal venous blood, the mechanisms available to assure adequate tissue oxygenation assume added importance. Hepatic hypoxia has been suggested as one possible etiologic factor in the hypoglycemia seen in polycythemic infants (9). Disturbances in hepatic oxygenation may also contribute to the hyperbilirubinemia seen in a number of neonatal conditions involving circulatory disturbances.…”

Section: Blood Flow and Oxygen Delivery To The Organs Of The Neonatalmentioning

confidence: 99%

Blood Flow and Oxygen Delivery to the Organs of the Neonatal Lamb as a Function of Hematocrit

1986

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ABSTRACT. We chronically catheterized 15 newborn lambs (9.5 f 2.8 days) and measured the distribution of cardiac output by the radionuclide-microsphere technique at hematocrits ranging from 10 volumes % to 55 volumes %. Seven animals were made progressively anemic and eight polycythemic by means of exchange transfusions. Cardiac output and heart rate increased with decreasing hematocrit while whole body oxygen consumption showed a small decrease during severe anemia. Both cerebral and cardiac blood flow markedly increased during anemia which assured a relatively stable oxygen delivery to both organs. The changes seen for blood flow to the carcass (skin, bones, and muscle) were predictable from the effects of blood viscosity: small decreases in flow at the highest hematocrits and small increases in flow at the lowest hematocrits. Consequently, oxygen delivery was as low as 1 ml of oxygen/min/100 g at a hematocrit of 10 volumes %. Renal blood flow remained unchanged while oxygen delivery fell when hematocrit was decreased. Hepatic oxygenation was measured using a modification of the Fick principle. Hepatic blood flow showed only a small decrease as hematocrit increased and changed minimally during anemia resulting in a falling delivery of oxygen with anemia. A stable hepatic oxygen consumption was assured by a marked increase in oxygen extraction during anemia. Two differing organ responses to changes in hematocrit can be seen in the newborn: the brain and heart vary blood flow to assure an adequate delivery of oxygen while a number of other organs show less blood flow regulation and, most likely, vary oxygen removal from blood. Over a wide range of hematocrits, compensatory responses occur in the newborn which effectively prevent the development of tissue hypoxia. (Pediatr Res 20: 1274-1279, 1986 The physiologic responses that occur with isovolemic anemia and polycythemia reflect the continual interplay between the requirements for tissue oxygenation and the rheologic effects of changes in blood viscosity. While information is available concerning the changes in the distribution of cardiac output for both the fetus (1) and adults (2-8) with anemia and polycythemia, there are little data for the newborn. Two patterns of organ blood flow response can be seen in conditions of decreased oxygen availability: the brain, heart and adrenal glands meet their oxygen requirements by increasing organ blood flows; the majority of other organs regulate the extraction of oxygen by varying capil- lary density and the oxygen diffusion gradient. When both oxygen content and blood viscosity are changing, complex physiologic adjustments are clinically important for the maintenance of a stable oxygen delivery to the organs of the newborn. Both anemia and polycythemia can occur from a variety of causes related to chronic and acute events during pregnancy and delivery. Understanding the limits within which adequate tissue oxygenation occurs offers both prognostic and therapeutic possibilities in the care of infants, especially as we tr...

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Section: Blood Flow and Oxygen Delivery To The Organs Of The Neonatalmentioning

confidence: 99%

Blood Flow and Oxygen Delivery to the Organs of the Neonatal Lamb as a Function of Hematocrit

1986

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“…Because the newborn lamb is frequently used as an experimental model for fetal and neonatal circulatory (5) as well as metabolic studies (8) and the results are extrapolated to humans, it was considered of utmost importance to obtain data on rheologic properties of adult and newborn blood in this species.…”

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A Comparison of Blood Viscosity between the Adult Sheep and Newborn Lamb. The Role of Plasma and Red Blood Cell Type

1983

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SummaryAdult sheep and newborn lamb blood viscosity (Vc) have been compared by taking into account not only the hematocrit, but also the type of the red cells (adult or fetal) in the circulation and the plasma Vc. At all shear rates studied the whole blood Vc of the adult was higher than that of the newborn. Plasma Vc was 1.58 +-0.18 centipoises in the adult compared to 1.21 +-0.19 in the newborn group (P < 0.001). The mean relative apparent viscosity (whole blood Vc/plasma Vc) was higher in the newborn although the difference was not significant. Abbreviations CP, centipoise Ht, hematocrit Vc, viscosityIn a recent study, blood viscosity of adults and human newborns was compared to determine the part played by the presence of fetal red cell and the plasma viscosity. This work showed that for the same hematocrit adult blood had a higher viscosity than that of the newborn. This was due to a higher viscosity of adult plasma (10).Because the newborn lamb is frequently used as an experimental model for fetal and neonatal circulatory (5) as well as metabolic studies (8) and the results are extrapolated to humans, it was considered of utmost importance to obtain data on rheologic properties of adult and newborn blood in this species. MATERIALS AND METHODSnewborn blood in presence of change in Ht was studied by plotting the logarithm of Vc against Ht. The statistical analysis of the regression lines were performed according to the methods outlined in Snedecor and Cochran (1 I). A preliminary test of the residual variances about the regression lines was done when these tests were not significant, it was then possible to assess the equality of the two slopes. If these tests were not significant the common values of the slopes were estimated, and the intercepts were calculated. The equality of the two intercepts could then be assessed. The Vc of adult and newborn blood in relation to the shear rate was also compared at three Ht ranges: 30-40, 50-60, and 60-70%). The Vc found for each sample was divided by the Vc of its plasma to obtain the relative apparent Vc (2). This ratio reflects the rheologic properties of the erythrocyte suspension. Unpaired Student's t test was used for statistical analyses unless specified otherwise. RESULTSThe influence of Ht changes on the apparent Vc of neonatal and adult blood at four different shear rates is shown in Figure 1. In all instances Vc increases with a rise of Ht, and at a given Ht the Vc decreases with increasing shear rates. Absolute values of adult blood appear to be higher than those of the newborn lamb. The comparison of the rate of change of the Vc of adult and newborn blood in presence of change in Ht is shown in Figure 2. The tests for the equality of variances were not significant at the 0.05 level. The tests of the equality of the slopes were also not significant at 0.05 level. All the tests of the equality of the intercepts were highly significant ( P < 0.001) for all shear rates studied. Figure 3 A, B, and C show the quantitative comparison between the two types of bloo...

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“…Hypoglycemia is frequently a problem found in infants with polycythemia even after correcting for factors such as intrauterine growth retardation (IUGR). Leake et al 80 and Creswell et al 81 have examined this problem in the newborn lamb. Both groups speculated about decreased glucose production and increased glucose uptake, but a definitive conclusion could not be derived from their work.…”

Section: Hypoglycemiamentioning

confidence: 99%

Polycythemia and Hyperviscosity in the Newborn

Rosenkrantz

2003

Semin Thromb Hemost

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Research from the past 15 to 20 years has led to a comprehensive understanding of the etiology and effects of polycythemia and hyperviscosity in the newborn. Polycythemia and hyperviscosity are generally a result of a poor intrauterine environment or hypoxic complications during labor and delivery. Changes in blood viscosity are a direct result of changes in hematocrit because the plasma viscosity in the newborn is virtually always normal. Polycythemia and hyperviscosity are associated with decreases in blood flow to the brain, heart, lung, intestines, and carcass. Renal blood flow is not affected, but renal plasma flow is diminished, resulting in a lower glomerular filtration rate (GFR). The elevated hemoglobin and hematocrit are associated with an increase in the arterial oxygen content. It is the increase in arterial oxygen content, not the hyperviscosity, that is directly responsible for the decreased blood flow in the brain and heart as well as cardiac output. As a result, brain and cardiac oxygenation is normal. Decreased pulmonary blood flow appears to be the result of hyperviscosity and can result in system hypoxia. This can be corrected by a partial exchange transfusion to lower the hematocrit and viscosity. This will also improve renal function by increasing plasma flow. Because the abnormalities in brain function are due to a primary hypoxia event and not reduced cerebral blood flow, a partial exchange transfusion will not improve short-term or long-term abnormalities in neurological functioning.

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Glucose Perturbation in Experimental Hyperviscosity

Cited by 14 publications

References 18 publications

Blood Flow and Oxygen Delivery to the Organs of the Neonatal Lamb as a Function of Hematocrit

Blood Flow and Oxygen Delivery to the Organs of the Neonatal Lamb as a Function of Hematocrit

A Comparison of Blood Viscosity between the Adult Sheep and Newborn Lamb. The Role of Plasma and Red Blood Cell Type

Polycythemia and Hyperviscosity in the Newborn

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