Expensive cerebral blood flow measurements alone are useless and misinformative in comatose patients: a comprehensive alternative

Abstract

-Since the first report addressing quantification of cerebral blood flow (CBF), concomitant assessment of cerebral oxygen consumption was also carried out. Over the years, however, some investigators have emphatically and mistakenly addressed cerebral ischemia in comatose patients, on the basis of CBF measurements alone. In contrast, we have repeatedly reported that ischemia in these patients must be precisely evaluated based on CBF-metabolism coupling or uncoupling, rather than CBF alone. Based on these previous findings, we therefore propose a comprehensive alternative approach, namely the evaluation of brain ischemia in comatose patients based on cerebral metabolic parameters, such as cerebral extraction of oxygen or cerebral lactate release, without expensive CBF measurements.KEY WORDS: arteriojugular lactate difference, brain ischemia, cerebral blood flow, cerebral extraction of oxygen, coma.Medidas dispendiosas apenas de fluxo sanguíneo cerebral são inúteis e desinformativas em estados de Medidas dispendiosas apenas de fluxo sanguíneo cerebral são inúteis e desinformativas em estados de Medidas dispendiosas apenas de fluxo sanguíneo cerebral são inúteis e desinformativas em estados de Medidas dispendiosas apenas de fluxo sanguíneo cerebral são inúteis e desinformativas em estados de Medidas dispendiosas apenas de fluxo sanguíneo cerebral são inúteis e desinformativas em estados de coma: uma alternativa abrangente coma: uma alternativa abrangente coma: uma alternativa abrangente coma: uma alternativa abrangente coma: uma alternativa abrangente RESUMO -Desde o primeiro artigo apresentando quantificação de fluxo sanguíneo cerebral (FSC), também se avaliou o consumo cerebral de oxigênio. Todavia, ao longo dos anos, alguns investigadores têm enfaticamente e erroneamente destacado a isquemia cerebral em pacientes comatosos, baseando-se apenas em medidas do FSC. Em contrapartida, temos repetidamente destacado que a avaliação de isquemia cerebral nestes pacientes deve ser baseada no conceito de acoplamento ou desacoplamento entre metabolismo cerebral e FSC, ao invés de alterações no FSC apenas. Baseando-se nestes achados prévios, aqui propomos uma abordagem alternativa e abrangente, a qual envolve a avaliação de isquemia cerebral em pacientes comatosos baseando-se em parâmetros metabólicos cerebrais, tais como a extração cerebral de oxigênio ou a liberação cerebral de lactato, sem medidas dispendiosas de FSC. Since the pioneering work of Kety and Schmidt 1 , addressing quantification of cerebral blood flow (CBF), concomitant assessment of the cerebral metabolic rate of oxygen consumption (CMRO 2 ) was also established. CBF was precisely quantified as the integrated arteriojugular difference of nitrous oxide over approximately 10 minutes (the "height-overarea" method of quantification), whereas CMRO 2 was calculated as the product of CBF and the arteriojugular oxygen content difference (AVDO 2 ). The latter parameter had already been introduced in the pertinent literature by another pioneering work of Gibb...

Cerebral Hemodynamics By Transcranial Doppler And Protein S100β In Patients With Sepsis-Associated Encephalopathy

“…The classic work of Obrist and colleagues 32 shows how patients with low flow pattern achieve near-normal values of arteriovenous oxygen difference (DavO 2 ), however, patients with hyperemic pattern show DavO 2 below the limits of normality. The article by Obrist et al 32 and more recently that of Cruz et al 33 , have shown that the worst result is given by the decoupling between cerebral blood flow (CBF) and cerebral metabolic rate of O 2 (flow -metabolism), with unfavourable results associated with hyperemic patterns.…”