Abstract
Objective
It has been established that during constant presure arterio-venous bypass perfusion, brain metabolism gradually deteriorates in parallel with the declining hematocrit. However, whether this is due to a disturbance of flow regulation or to the decline in the oxygen-carrying capacity of the blood has not been documented. Therefore, intact animals were submitted to severe hemodilution to determine the threshold for the beginning of functional and biochemical impairment of the brain.
Methods
Six anesthetized and paralyzed adult mongrel cats were submitted to gradual isovolemic hemodilution by stepwise exchange of blood with Ringer lactate/dextran (1∶1) solution. Exchange of 80 ml/kg body weight resulted in a final hematocrit level ranging from 6.1% to 11%.
Results
Cerebral blood flow gradually increased during hemodilution, with a sharp rise to eight times the prehemodilution value when the hematocrit fell below 10%. The calculated oxygen delivery to the brain remained relatively unchanged. Hemodilution did not cause suppression of spontaneous ECoG or somatically evoked primary cortical potentials, even at the lowest hematocrit value of 6.1%. Brain tissue ATP and phosphocreatine content were largely maintained, although tissue lactate content was elevated (9.54±5.99 μmol/g).
Conclusions
The hemodynamically unimpaired healthy mammal is able to support a substantial degree of hemodilution without major functional or biochemical disturbance to the brain. The previously observed disturbances during prolonged bypass perfusion are, therefore, most probably due to the associated abnormalities of flow regulation.
References
Iijima T, Back T, Hossmann K-A (1995) Effect of extracorporeal life support on cerebral blood flow, metabolism and electrophysiology in normothermic cats. Intensive Care Med 21:38–44
Jacobs DS, Kasten BL Jr, DeMott WR, Wolfson WL (1990) Laboratory test handbook, 2nd edn. Williams & Wilkins, Baltimore Hong Kong London Sydney
Alman PL, Dittmer DS (1972) Biology data book, 2nd edn. University Press, Bethesda
Kelman GR Nunn JF (1968) Computer produced physiological tables for calculations involving the relationships between blood oxygen tension and content. Butterworths, London
Ponten U, Ratcheson A, Salford LG, Siesjö BK (1973) Optimal freezing conditions for cerebral metabolites in rats. J Neurochem 21:1127–1138
Kogure K, Alonso OF (1978) A pictorial representation of endogenous brain ATP by bioluminescent method. Brain Res 154:273–284
Paschen W, Niebuhr I, Hossmann K-A (1981) A bioluminescence method for the demonstration of regional glucose distribution in brain slices. J Neurochem 36:513–517
Paschen W (1985) Regional quantitative determination of lactate in brain sections. A bioluminescent approach. J Cereb Blood Flow Metab 5:609–612
Csiba L, Pachen W, Hossmann K-A (1983) A topographic quantitative method for measuring brain tissue pH under physiological and pathophysiological conditions. Brain Res 289: 334–337
Carson JL, Poses RM, Spence RK, Bonavita G (1988) Severity of anaemia and operative mortality and morbidity. Lancet I:727–729
Stein JI, Gombotz H, Rigler B, Metzler H, Suppan C, Beitzke A (1991) Open heart surgery in children of Jehovah's Witnesses: Extreme hemodilution on cardiopulmonary bypass. Pediatr Cardiol 12:170–174
Borgström L, Johannsson H, Siesjö BK (1975) The influence of acute normovolemic anemia on cerebral blood flow and oxygen consumption of anesthetized ratz. Acta Physiol Scand 93: 505–514
Hudak ML, Koehler RC, Rosenberg AA, Traystman RJ, Jones MD (1986) Effect of hematocrit on cerebral blood flow. Am J Physiol 251:H63-H70
Massik J, Tang Y-L, Hudak ML, Koehler RC, Traystman RJ, Jones MD (1987) Effect of hematocrit on cerebral blood flow with induced polycythemia. J Appl Physiol 62:1090–1096
Hudak ML, Jonse DM, Popel AS, Koehler RC, Traystman RJ, Zeger SL (1989) Hemodilution causes size-dependent constriction of pial arteriles in the cat. Am J Physiol 257:H912-H917
Heistad DD, Marcus ML Abboud FM (1978) Role of large arteries in regulation of cerebral blood flow in dogs. J Clin Invest 62:761–768
Kontos HE, Wei EP, Navari RM, Levasseur JE, Rosenblum WI, Patterson JLJ (1978) Response of cerebral arteries and arterioles to acute hypotension and hypertension. Am J Physiol 234:1–9
Lundar T, Lindegaard KF, Frøysaker T, Aaslid R, Wiberg J, Nornes H 1985) Cerebral perfusion during nonpulsatile cardiopulmonary bypass. Ann Thorac Surg 40:144–150
Schmidt-Kastner R, Hossmann K-A, Grosse Ophoff B (1986) Relationship between metabolic recovery and the EEG after prolonged ischemia of the cat brain. Stroke 17:1164–1169
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Bauer, R., Iijima, T. & Hossmann, K.A. Influence of severe hemodilution on brain function and brain oxidative metabolism in the cat. Intensive Care Med 22, 47–51 (1996). https://doi.org/10.1007/BF01728330
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01728330