Apnea testing guided by continuous transcutaneous monitoring of partial pressure of carbon dioxide.

OBJECTIVE

To continuously monitor PCO2 during two different protocols for apnea testing as part of the determination of brain death.

DESIGN

Prospective comparative study using continuous transcutaneous PCO2 (tcPCO2) monitoring in 54 apnea tests with or without artificial CO2 augmentation. Another 53 apnea tests were not continuously monitored.

SETTING

Intensive care wards in Northern Bavaria.

PATIENTS

Ninety-six consecutive patients with suspected brain death.

INTERVENTIONS

Apnea tests guided by transcutaneous monitoring during a PaCO2 of > or = 60 torr (> or = 8 kPa).

MEASUREMENTS AND MAIN RESULTS

The mean of the difference between tcPCO2 and PaCO2 was -0.26 +/- 1.16 (SEM) torr (-0.035 +/- 0.15 kPa). Seventy percent of all transcutaneous measurements were within +/-10% of the PaCO2 values. The individual differences ranged from -25.8 to 16.9 torr (-3.44 to 2.25 kPa).

CONCLUSIONS

While not as precise as could be desired in individual cases, the overall agreement between tcPCO2 and PaCO2 was good. Transcutaneous monitoring aided in effectively reducing the CO2 target overshoot with artificial CO2 augmentation, reduced the necessary number of blood gas checks compared with a former study, using predetermined time-locked evaluations, and prolonged only tests with artificial CO2 augmentation.