Cerebral vascular response to hemorrhagic hypotension in newborn lambs: the influence of developing anemia
| Autor: | Franklin Ga, Stephen M Golden, Errol R. Alden, O'Neill Jt |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Anemia
chemistry.chemical_element Blood Pressure Hemorrhage Hematocrit Oxygen General Biochemistry Genetics and Molecular Biology chemistry.chemical_compound Oxygen Consumption medicine Animals Homeostasis Cerebral perfusion pressure Sheep medicine.diagnostic_test business.industry Chloralose Brain Hydrogen-Ion Concentration medicine.disease Microspheres Blood pressure Cerebral blood flow chemistry Animals Newborn Regional Blood Flow Anesthesia Vascular Resistance Blood Gas Analysis Hypotension business Perfusion |
| Zdroj: | Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.). 205(2) |
| ISSN: | 0037-9727 |
| Popis: | The ability of newborn animals to autoregulate cerebral blood flow (CBF) has been documented. Most studies of the cerebral vascular response to hypotension utilize hemorrhage, generally confounded with anemia. We studied the cerebral blood flow and metabolic response of chloralose and urethane anesthetized newborn lambs to regulated hypotension. Lambs (< or = 7 days old) were catheterized for radioactive microsphere determinations of CBF. The dorsal sagittal sinus was catheterized to obtain cerebral blood samples for the calculation of oxygen uptake. Cerebral perfusion pressure was reduced in a step-wise fashion with hemorrhagic hypotension. Animals spontaneously became anemic with hypotension (AH; n = 8). In a group of animals (NH; n = 6), anemia was prevented by infusion of autologous red blood cells. Arterial pressure was reduced from control to 50, 40, and 30 mm Hg. In the AH group hematocrit fell 37% but was not different from control in the NH group. Total CBF was maintained in all groups. The lowest perfusion pressures studied were 25 +/- 1 and 22 +/- 1 mm Hg in AH and NH groups respectively. Oxygen delivery decreased (37%) only in the AH group, secondary to anemia. Calculated oxygen consumption was maintained in the AH group but increased (approximately 50%) in the NH group at 50 and 40 mm Hg. The ratio of oxygen uptake to oxygen delivery (fractional oxygen extraction) increased linearly in both groups as arterial pressure decreased. The major findings of these experiments are (i) The anesthetized newborn lamb can maintain CBF when perfusion pressure falls to 25 mm Hg and this autoregulatory capacity (classically defined) is not dependent on a change in hematocrit and, presumably, viscosity; (ii) Cerebral hypotension, anemic or not, appears to be accompanied by an increase in fractional extraction of oxygen. |
| Databáze: | OpenAIRE |
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