Influence of Intra-Operative Regional Cerebral Blood Flow and the Carbon Dioxide Partial Pressure Difference between Arterial and End-Tidal on the Neurologic Outcome

ABSTRACT

OBJECTIVE: End-tidal partial pressure of carbon dioxide(PETCO2) is often used as an estimate of arterial partial pressure of carbon dioxide(PaCO2), with the understanding that PaCO2 usually exceeds PETCO2. During craniotomies, because hyperventilation is used to therapeutically lower intracranial pressure, the difference between arterial and end-tidal partial pressure of carbon dioxide(P(a-ET)CO2) has therapeutic implications. To determine how much information concerning neurosurgical operation and clinical outcome is provided by the PETCO2, PaCO2 and P(a-ET)CO2 during surgery, we evaluated 81 patients who had neurosurgical operation. METHODS: There were 51 males and 30 females with a mean age of 50.3 years(range 7-85 years). After the induction of general anesthesia, body temperature was maintained in a normothermia, endtidal CO2 was maintained 28-34mmHg and the systolic blood pressure was kept 90-120mmHg. ETCO2, PaCO2 and regional cortical blood flow(rCoBF) were checked at the time of dura closure. Neurologic outcome was evaluated at 8 hours after operation to rule out other factors which may influence on the patient's long-term outcome. Data were collected and compared by student's t-test or chi-square analysis. RESULTS: The PaCO2 was 34.6+/-5.2mmHg(range, 24.9-54.8), PETCO2 was 29.9+/-4.1mmHg(range, 20.0-45.0) and P(a-ET)CO2 was 4.7+/-3.5mmHg(range, -1.1-18.6). The correlation between the PaCO2 and PETCO2 was statistically significant(PETCO2=13.3-0.57xPaCO2). But there was no correlation of rCoBF with PaCO2 and ETCO2. P(a-ET)CO2 values less than 8mmHg were correlated well with good neurologic outcome compared with higher P(a-ET)CO2 patients. PaCO2, rCoBF, mean arterial blood pressure, arterial pH and initial Glasgow coma scale showed statistically significant correlation with neurologic outcome(p<0.05). CONCLUSION: Based on our study, P(a-ET)CO2 value could be used as a good prognostic factor during the neurosurgical operation and anesthesiologist should be tried to decrease this value. And in patients who has a intact brain autoregulation, rCoBF was not influenced by PaCO2 and ETCO2, entirely.