Cerebral blood flow and oxidative metabolism during hypoxia and asphyxia in the new‐born calf and lamb.

Abstract

SUMMARY1. The effects of hypoxia and asphyxia on cerebral blood flow and oxidative metabolism have been investigated in the calf and lamb under sodium pentobarbitone anaesthesia.2. Cerebral blood flow was determined using a hydrogen clearance technique, and cerebral metabolism quantified by the simultaneous measurement of arteriocerebral venous concentration differences for oxygen, glucose and lactate.Continuous measurements were made of arterial and cerebral venous PO, in vivo.3. Both cerebral blood flow and oxygen consumption were less in animals anaesthetized with sodium pentobarbitone than in conscious animals.4. In the calf, recovery from transient episodes of severe hypoxia and asphyxia was associated with a rapid recovery and overshoot of cerebral venous Po2. Evidence was obtained that rapid changes in blood pressure during severe asphyxia were associated with pressure-passive cerebral blood flow. Prolonged hypoxia (Pa, Ad: 21 + 2 mmHg) with normocapnia was associated with an increase in cerebral blood flow, fall in cerebral oxygen consumption, and no change in the glucose-oxygen index.5. In the lamb, prolonged asphyxia (PO: 30+ 1 mmHg; P c02o 56+ 2 mmHg) was associated with an increase in cerebral blood flow. Cerebral glucose uptake did not change, but cerebral oxygen consumption was markedly depressed, and the glucose-oxygen index increased. 6. In the lamb during normoxia, there was a linear correlation between cerebral blood flow and arterial PC0o in the range 10-95 mmHg (r = 0-92; P < 0.001), with a slope of 1'74 ml. 100g-1 min'. mmHg PacoX2' Hypoxia did not significantly increase the fall in cerebral vascular resistance associated with a rise in Pa co, from 34 to 56 mmHg.

Substrate Utilization and Brain Development

“…Arteriovenous differences for oxygen and glucose showed no significant difference between the conscious and anaesthetised state, and the values obtained by Gardiner (1980b) and by Jones et al (1975) were in close agreement. In conscious ani mals, CMR02 was 174 /Lmol 100 g-I min-1 and CMRg!u was 31 /Lmol 100 g-l min-I (Table 2).…”

“…In a subsequent study on cerebral metabolism in newborn calves (Gardiner, 1980b) considerably higher values were reported for CBF (70 ml 100 g-l min-I) and for CMR02 (148 /Lmol 100 g-l min-I) in conscious animals. Sodium pentobarbitone anaesthesia was then found to reduce both values by about 30%, and CMRg!u in these anaesthetised animals was 14 /Lmol 100 g-l min-I.…”

“…Cerebral oxidative metabolism in the newborn calf has been studied in association with the effects of hypoglycemia (Gardiner, 1980a) and hypoxia (Gardiner, 1980b).…”

Brain Metabolic Correlates of Hypoxic-Ischemic Cerebral Necrosis in Mid-Gestational Sheep Fetuses: Significance of Hypotension

“…Asphyxiated newborn dogs (Hernandez et aI. , 1979) and calves (Gardiner, 1980) show similar findings. Such vasodilatation increases oxygen de livery to brain and prevents a reduction in cerebral energy charge (Siesjo, 1978) even though blood ox ygen content is decreased.…”

Avaliação física e dos níveis séricos de cortisol de bezerros neonatos da raça Nelore, nascidos de partos normais e auxiliados

“…Os neonatos saudáveis sofrem, discreta acidose após o nascimento. Já, a taquipnéia prolongada, acompanhada de dilatação de narinas e abertura da boca para respirar (dispnéia), pode ser sugestiva de envolvimento pulmonar primário (Gardiner 1980). Apesar de não terem sido constatadas diferenças estatisticamente significativas entre as frequên-cias respiratórias, aferidas de bezerros nascidos de partos eutócicos e laboriosos, em ambos os períodos estudados (Quadro 2), este parâmetro biológico deve ser sempre levado em consideração para os diferentes tipos de nascimentos e momentos de observação, mesmo que haja, na maioria dos casos, rápida ação dos mecanismos respiratórios de compensação, em animais com acidose metabólica (Haskins 1977, Lisboa et al 2002.…”