Clinical cerebral monitoring: the role of the jugular O_2 difference

摘要

Jugular bulb oxyhaemoglobin saturation (SjO_2) is a measure of global cerebral oxygen balance, because SjO_2 is closely related to the oxygen content in the venous blood of the jugular bulb (cjO_2). The latter is determined by SjO_2, the hemoglobin concentration (Hb), and the oxygen tension in the venous blood of the jugular bulb (PjO_2). We may therefore conclude that for a given Hb concentration, changes in SjO_2 always indicate changes in cjO_2. The cerebral metabolic rate of oxygen or cerebral oxygen consumption (CMRO_2) is the difference between cerebral oxygen transport (DO_2) and the amount of O_2 leaving the brain with venous blood. Cerebral DO_2 is the product of cerebral blood flow (CBF) and arterial oxygen content. Consequently, cjO_2 depends on the relationship between DO_2-CMRO_2 to CBF.