319 USE OF TRANSCUTANEOUS PCO2 ELECTRODES FOR DIAGNOSIS AND THERAPY OF INFANTS IN SHOCK

Abstract

Transcutaneous PCO2 (PtcCO2) values are dependent on changes of local perfusion. We studied the effects of shock, acidosis and cardiovascular (CV) drugs on unheated (NH) PtcCO2, in 21 preterm and 5 term infants who required dopamine (D), isoproterenol (I), tolazoline (T) and transfusions of blood (B). Simultaneous PaCO2 and NHPtcCO2 tensions obtained before and during drug therapy were compared. Correlations of values obtained during hypotension (BP<2SD of normal), acidosis (pH<7.25) or both treated with CV drugs, were compared to those during the same conditions without CV drug therapy. When CV drugs were not given, PtcCO2 values during hypotension were the highest and most discrepant from PaCO2. Administration of I and D decreased the PtcCO2 differences. With CV drugs, the differences became greater in hypotension accompanied by acidosis. T and B decreased the difference between PtcCO2 and PaCO2. These data suggest that: 1) The high PtcCO2 associated with cardiovascular compromise reflects lack of tissue perfusion. 2) In hypotension, widened PtcCO2 - PaCO2 differences are narrowed by CV drugs. 3) If acidosis is added to hypotension, CV drugs are less effective in reducing the differences, suggesting it interfers with their action. 4) T and B narrow the differences, indicating improved tissue perfusion. We conclude the PtcCO2 electrode can be valuable as an indicator of tissue perfusion in the care of infants with cardiovascular alterations.