Brain microvascular function during cardiopulmonary bypass
Emboli in the brain microvasculature may inhibit brain activity during cardiopulmonary bypass. Such hypothetical blockade, if confirmed, may be responsible for the reduction of cerebral metabolic rate for glucose observed in animals subjected to cardiopulmonary bypass. In previous studies of cerebral blood flow during bypass, brain microcirculation was not evaluated. In the present study in animals (pigs), reduction of the number of perfused capillaries was estimated by measurements of the capillary diffusion capacity for hydrophilic tracers of low permeability. Capillary diffusion capacity, cerebral blood flow, and cerebral metabolic rate for glucose were measured simultaneously by the integral method, different tracers being used with different circulation times. In eight animals subjected to normothermic cardiopulmonary bypass, and seven subjected to hypothermic bypass, cerebral blood flow, cerebral metabolic rate for glucose, and capillary diffusion capacity decreased significantly: cerebral blood flow from 63 to 43 ml/100 gm/min in normothermia and to 34 ml/100 gm/min in hypothermia and cerebral metabolic rate for glucose from 43.0 to 23.0 mumol/100 gm/min in normothermia and to 14.1 mumol/100 gm/min in hypothermia. The capillary diffusion capacity declined markedly from 0.15 to 0.03 ml/100 gm/min in normothermia but only to 0.08 ml/100 gm/min in hypothermia. We conclude that the decrease of cerebral metabolic rate for glucose during normothermic cardiopulmonary bypass is caused by interruption of blood flow through a part of the capillary bed, possibly by microemboli, and that cerebral blood flow is an inadequate indicator of capillary blood flow. Further studies must clarify why normal microvascular function appears to be preserved during hypothermic cardiopulmonary bypass.
- Research Organization:
- Copenhagen Univ., Denmark
- OSTI ID:
- 5669307
- Journal Information:
- J. Thorac. Cardiovasc. Surg.; (United States), Vol. 94:5
- Country of Publication:
- United States
- Language:
- English
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BRAIN
BLOOD FLOW
GLUCOSE
METABOLISM
HEART
SURGERY
CAPILLARIES
DYNAMIC FUNCTION STUDIES
PERMEABILITY
RADIOISOTOPES
SWINE
TRACER TECHNIQUES
ALDEHYDES
ANIMALS
BLOOD VESSELS
BODY
CARBOHYDRATES
CARDIOVASCULAR SYSTEM
CENTRAL NERVOUS SYSTEM
DOMESTIC ANIMALS
HEXOSES
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MEDICINE
MONOSACCHARIDES
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ORGANS
SACCHARIDES
VERTEBRATES
550600* - Medicine
550501 - Metabolism- Tracer Techniques