Monitoring of the intracranial hemodynamics and oxygenation during and after hyperventilation in newborn rabbits with near-infrared spectroscopy.

Oxyhemoglobin, deoxyhemoglobin, total hemoglobin, and oxidized cytochrome aa3 were monitored, blood pressure and heart rate were continuously recorded, and cerebral hemodynamic changes were analyzed during and after hyperventilation (arterial CO2 tension < 2.67 kPa) and/or hyperoxemia (100% O2 inhalation) in 11- to 12-d-old rabbits. Oxyhemoglobin, deoxyhemoglobin, total hemoglobin, and oxidized cytochrome aa3 were monitored by means of near-infrared spectroscopy. Near-infrared spectroscopy ideally demonstrated decreases in oxyhemoglobin and total hemoglobin and an increase in deoxyhemoglobin during hyperventilation and a return to the previous values after hyperventilation. Cytochrome aa3 decreased during hyperventilation. On hyperventilation with 100% O2 inhalation, however, cytochrome aa3 was not reduced, although the changes in oxyhemoglobin and total hemoglobin were more significant. This reduction of cerebral oxygenation during hyperventilation without the administration of oxygen may induce hypoxic-ischemic brain damage. Noninvasive monitoring of cerebral oxygenation and hemodynamics, for which near-infrared spectroscopy is useful, is a requisite for the prevention of brain injury caused by severe hypocarbia in hyperventilation therapy.