Detection of cerebral venous desaturation by continuous jugular bulb oximetry following acute neurotrauma.

A prospective observational study was performed to assess the reliability of fibreoptic oximetric catheters and to identify the incidence and causes of jugular bulb oxygen desaturation in patients with acute closed head injury. There were twenty-five patients (30 +/- 16 years) with GCS < or = 8 in this study. Jugular bulb oximetry, mean arterial pressure, intracranial pressure, end-tidal CO2 and pulse oximetry were monitored continuously. Catheter calibration against a laboratory oximeter was performed post insertion and thereafter eight-hourly. Cerebral venous desaturation was defined as a jugular bulb oxygen saturation < 55% of > 10 minutes duration. There was a poor correlation for the first in vivo calibration (r2 = 0.602, P < 0.001, n = 25). Thereafter a close correlation between jugular bulb catheter and oximetry values was demonstrated (r2 = 0.868, P < 0.001, n = 205). Forty-two episodes of jugular bulb oxygen desaturation of 88 minutes mean duration (range 10 to 555) were observed. 83% occurred within 48 hours following injury. Hypocapnia was associated in 45% of episodes; hypoperfusion in 22%; raised ICP in 9% and a combination of the above in 24%. Validation with a laboratory oximeter is essential prior to continuous jugular bulb oximetry. Sustained episodes of cerebral venous desaturation are frequent within the first 48 hours following acute head injury. Factors such as hypocapnia and cerebral hypoperfusion that primarily reduce cerebral blood flow are predominant.