Continuous monitoring of jugular bulb oxygen saturation in comatose patients--therapeutic implications

Comatose patients run a high risk of developing cerebral ischaemia which may considerably influence final outcome. It would therefore be extremely useful if one could monitor cerebral blood flow in these patients. Since there is a close correlation between the arteriovenous difference of oxygen and cerebral blood flow, it was a logical step to place a fiberoptic catheter in the jugular bulb for continuous measurement of cerebrovenous oxygen saturation. We have monitored cerebral oxygenation in 54 patients, comatose because of severe head injury, intracerebral haemorrhage or subarachnoid haemorrhage. Normal jugular venous oxygen saturation (SJVO2) ranges between 60 and 90%. A decline to below 50% is considered indicative of cerebral ischaemia. Spontaneous episodes of desaturation (SJVO2 < 50% for at least 15 min) were frequent during the acute phase of these insults. Many of these desaturation episodes could be attributed to hyperventilation, even though considered moderate. Likewise, insufficient cerebral perfusion pressure and severe vasospasm were found to be important causes of desaturation episodes. In many instances, tailoring of ventilation or induced hypervolaemia and hypertension were capable of reversing these low flow states. The new method of continuous cerebrovenous oximetry is expected to contribute to a better outcome by enabling timely detection and treatment of insufficient cerebral perfusion.