Effects of injury and therapy on brain parenchyma pO2, pCO2, pH and ICP following severe closed head injury.

Simultaneous monitoring of brain parenchyma pO2, pCO2, and pH (PbO2, PbCO2 and pHb) has been tested in ICU environments using fiber optic sensors incorporated in probes 0.5 mm in diameter. An Institutionally approved protocol was used to test the concept and technology for monitoring PbO2, PbCO2 and pHb, and to observe the effects of injury and therapy interventions on each of the variables monitored, including ICP, the clinical standard. ICP and fiber optic pO2, pCO2 and pH probes were placed in 10 SCHI patients at bedside in the ICU using sterile technique. The probes remained in place for the duration of ICP monitoring, and were functional in the ICU environment for up to 10 days. Trend patterns recurred in this series of SCHI patients: Extreme PbCO2 (high) and pHb (low) are associated with poor perfusion; increasing pbCO2 and decreasing pHb may be early indicators of ICP crisis, i.e. ICP > 20 mm Hg that tends to be unresponsive to therapy, and; pentobarbital "loading" and maintenance is associated with increased pbO2. These preliminary results from monitoring pbO2, pbCO2 and pHb in SCHI patients indicate that fiber optic sensor technology functions and is able to be used in this application. Trend patterns from this data may further indicate practical utility as a more direct monitor of the delicate balance between tissue perfusion and cell metabolism than ICP alone.