Skin surface PCO2 monitoring in newborn infants in shock: effect of hypotension and electrode temperature

We studied the effect of hypotension and of electrode temperature (41 degrees C to 44 degrees C) on the relation of skin surface PCO2 (Roche prototype) to arterial PCO2 in 24 sick neonates of 690 to 3,500 gm with systolic blood pressures of 5 to 70 mm Hg. PsCO2 closely correlated with PaCO2. The standard error of estimating PaCO2 from PsCO2 was 3.02 torr at 44 degrees C, 3.20 torr at 43 degrees C, and 3.57 torr at 41 degrees C. The pH (6.89 to 7.61), body temperature (33.5 to 38.1 degrees C), hematocrit (0.28 to 0.65), scleredema, or treatment with tolazoline did not affect the relation of PsCO2 to PaCO2. PsCO2 grossly exceeded the predicted value at systolic blood pressures below 15 mm Hg, irrespective of electrode temperature.