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Qualitative comparison of carbon dioxide-induced change in cerebral near-infrared spectroscopy versus jugular venous oxygen saturation in adults with acute brain disease.

OBJECTIVE
To compare carbon dioxide-induced changes in cerebral oxy- and deoxyhemoglobin, measured by near-infrared spectroscopy, with those changes in jugular venous oxygen saturation in adult patients with acute brain disease.


DESIGN
A prospective study.


SETTING
The medical and surgical intensive care unit of a university hospital.


PATIENTS
Nine patients with head trauma (n = 4), cerebrovascular disease (n = 3), and meningitis (n = 2). A total of ten measurements were done, while PaCO2 was increased from hypocapnia toward normocapnia in the nine patients.


INTERVENTIONS
Arterial and jugular bulb catheterization, and intracranial pressure monitoring were performed as a part of the clinical intervention. An increase in PaCO2 was obtained by inhalation of CO2 and, if necessary, by reducing the ventilator rate.


MEASUREMENTS AND MAIN RESULTS
In each patient, the position of the jugular bulb catheter was ascertained by skull roentgenography. Near-infrared spectroscopic values for oxy- and deoxyhemoglobin were set at zero at the beginning of the study. An increase in PaCO2 from 29 +/- 1 (SEM) torr (3.9 +/- 0.2 kPa) to 39 +/- 2 torr (5.2 +/- 0.3 kPa) was accompanied by a significant increase in jugular venous oxygen saturation from 63 +/- 3% to 76 +/- 3%; a significant increase in oxyhemoglobin of 3.5 +/- 0.9 mumol/L (of the brain tissue); and a significant decrease in deoxyhemoglobin of 1.5 +/- 0.4 mumol/L. In nine of ten measurements, the slopes of changes in oxyhemoglobin against the slopes of change in jugular venous oxygen saturation were very similar. In one patient, oxyhemoglobin changed negligibly while jugular venous oxygen saturation increased by 20%.


CONCLUSIONS
Jugular venous oxygen saturation consistently demonstrates cerebrovascular responsiveness to CO2. The direction and magnitude of changes in cerebral oxyhemoglobin, measured by near-infrared spectroscopy, were similar to those changes in jugular venous oxygen saturation in most of our cases. Interpretation of a negligible change in oxyhemoglobin in one patient, despite an obvious increase in jugular venous oxygen saturation, requires further study comparing near-infrared spectroscopy with standard techniques.