Objective: Our aim was to evaluate the utility of transcutaneous CO2 (TC-CO2) monitoring in following the response to therapy in children and adolescents in diabetic ketoacidosis (DKA) requiring ICU admission.
Methods: During therapy for DKA, TC-CO2 was monitored and compared with the serum bicarbonate values (HCO3-). As clinically indicated, serum electrolytes including serum HCO3- were drawn and at the same time, the TC-CO2 value was recorded. Using the TC-CO2 value and the equation (PaCO2=1.5xHCO3-+8), a calculated HCO3- value was determined. The measured serum HCO3- value was subtracted from the calculated HCO3- value and the absolute difference was recorded. The difference between the measured serum HCO3- and the calculated HCO3- was analysed using analysis of variance after stratification for serum HCO3- values and patient age ranges. Calculated to serum HCO3- values were compared using linear regression analysis. In addition, serum HCO3- values were plotted against TC-CO2 values to derive an equation from these data which would relate the TC-CO2 values to the measured serum HCO3-.
Results: The cohort included 28 patients ranging in age from 1.6 to 21 years (9.4 +/- 4.7 years) and in weight from 13 to 96 kg (35.6 +/- 18.2 kg). Two additional patients were not included as the initial TC-CO2 values were inaccurate because of tissue hypoperfusion. In the remaining 28 patients, the absolute difference between the calculated bicarbonate and serum bicarbonate values was 1.5 +/- 1.2 mmol.l-1. The difference was < or =2 mol.l in 74.4% of samples and < or=5 mmol.l(-1) in 99.2%. No difference in the value between the calculated and measured serum HCO3- was present according to serum HCO3- value or patient's age. Linear regression analysis of calculated HCO3- against serum HCO3- revealed a slope of 0.95 and an r2 value of 0.88. Linear regression analysis using serum HCO3- against TC-CO2 resulted in the following equations: TC-CO2=(1.64xHCO3-)+3.9 or HCO3-=0.61x(TC-CO2-3.9).
Conclusions: TC-CO2 correlates with serum HCO3- and can be used to follow therapy in children and adolescents in DKA.