Cerebral Cortical Blood Flow and Oxygen Metabolism in Normocythemic Hyperviscous Newborn Piglets

Abstract

ABSTRACT. Our study tests the hypothesis that hyper-cerebral blood flow has been demonstrated in adults with primary viscosity independent of arterial 0 2 content reduces cere-polycythemia (1 5-17). In the neonate, polycythemia is associated bra1 cortical blood flow, Oz delivery, and Oz uptake. After with decreased cerebral blood flow velocity and increased pulbaseline determinations, ten 2-to 4-day-old awake spon-satility indices that are reversed by partial plasma exchange hnesusly breathing piglets-ere given an intravenous in-transfusion (18,19). However, Jones et al. (20) emphasized the fusion (5 ml. kg-', body weight) of concentrated cyropre-importance of arterial 0 2 content in the regulation of cerebral cipitate, whereas eight controls received normal saline. blood flow. To maintain a constant 0 2 delivery, an alteration in Cerebral cortical blood flow, arterial and superior sagittal arterial 0 2 content results in a reciprocal change in blood flow. sinus 0 2 content, whole blood viscosity, hematocrit, blood Rosenkrantz et al. (21) showed in newborn lambs that the gases, and plasma fibrinogen concentrations were meas-cerebral blood flow reduction noted with polycythemic hypervisured at baseline and 3 h after infusion. No significant cosity is due to the increased arterial 0 2 content from polycychanges were observed in the control group. Three hours themia and not the result of hyperviscosity. Nevertheless, in after the infusion of concentrated cryoprecipitate the ex-paraproteinemic adults Humphrey and coworkers (22,23), demperimental group showed an increase in whole blood vis-onstrated that 0 2 content and blood viscosity are both independcosity, whereas hematocrit and arterial 0 2 content were ent variables controlling cerebral blood flow. unchanged. There was a decrease in cerebral cortical blood To examine the effect of hyperviscosity independent of polyflow and cerebral cortical 0 2 delivery, whereas cerebral cythemia and arterial O2 content, a normocythemic hyperviscous cortical 0 2 uptake was unchanged. We conclude that hy-animal model was developed. This study is designed to test the perviscosity independent of arterial 0 2 content reduces hypothesis that normocythemic hyperviscosity reduces cerebral cerebral cortical blood flow and that although Oz delivery cortical blood flow, O2 delivery, and 0 2 uptake in newborn was reduced in the newborn piglet cerebral cortical 0 2 piglets. uptake was maintained. (Pediatr Res 24: 486-489,1988) MATERIALS AND METHODS Animals. Eighteen newborn piglets were randomly divided Polycythemia and hyperviscosity occur in 3-5% of newborns into experimental (n = 10) and control (n = 8) groups and (1, 2). Structural and functional CNS abnormalities have been studied between 2 and 4 days of age. ~n i m a l weights on the day associated with polycythernia and hyperviscosity (3-9). The most of study were 1290 * 207 g (mean + SD) and 1280 + 158 g for common etiology of neonatal hyperviscosity is polycythemia. the experimental and control piglets, respectively. However,...

Elevated Low-Shear Blood Viscosity is Associated with Decreased Pulmonary Blood Flow in Children with Univentricular Heart Defects

“…Hyperviscosity from polycythemia results in greater oxygen content, resulting in a compensatory increase in cerebral vascular tone in order to decrease cerebral blood flow and maintain constant cerebral oxygen delivery. This mechanism is supported by several animal models as well as both pediatric and adult studies of cerebral blood flow in patients with polycythemia; in these studies, despite decreased cerebral blood flow, oxygen delivery is maintained due to increased cerebral oxygen extraction [9]. Similarly, in the Glenn circulation, hyper-viscosity could cause a decrease in cerebral blood flow, in turn causing a proportional decrease in PBF.…”

“…Elevated whole blood viscosity has been implicated as a significant independent risk factor of atherosclerosis and resultant cardiovascular disease in adults [12]. Hyperviscosity has also been shown to decrease cerebral blood flow both in neonatal and adult patients with polycythemia; interestingly, this effect has been observed in hyperviscous but normocythemic animal models as well [9]. In the pulmonary circulation, hyperviscosity can have similarly detrimental effects.…”

Neonatal polycythaemia: critical review and a consensus statement of the Israeli Neonatology Association

“…In experimental polycythaemia, glucose delivery and utilization in the brain decreases (33). Moreover, an experimental increase in whole‐blood viscosity through infusion of concentrated cryoprecipitate, in spite of constancy of red cell mass and O2 content, leads to a reduction in CBF (34). Increased cellular breakdown of the increased red cell mass .…”

The evaluation of polycythemic newborns: efficacy of partial exchange transfusion

“…Increased cerebrovascular resistance and diminished cerebral blood flow (CBF) velocity, determined by Doppler studies, have been observed in polycythemic infants [20,21]. Decreased CBF and oxygen delivery have been shown in animal experimental studies [22]. In our study, the patients with ICH were nearterm neonates with a history of prolonged labor.…”