Transcutaneous monitoring of carbon dioxide tension after cardiothoracic surgery in infants and children

In this prospective investigation, we evaluated the efficacy and accuracy of transcutaneous monitoring of CO2 (TC-CO2) in infants and children after cardiothoracic surgery. Cardiothoracic surgery patients whose ETCO2 and arterial CO2 values did not correlate (gradient greater than or equal to 5 mm Hg) during the first postoperative hour underwent placement of the TC electrode (30 of 33 patients). If the TC-CO2 to arterial difference was greater than or equal to 5 mm Hg,the TC-CO2 electrode was recalibrated and reapplied on another site. If the discrepancy was still greater than or equal to 5 mm Hg, the case was considered a clinical failure and no further data were collected (3 of 30 patients). If the arterial to TC gradient was <5 mm Hg, the patient was included in the data collection (27 of 30 patients). One to five sample sets (TC and arterial CO2) were collected from these patients. Statistical analysis included linear regression analysis and Bland-Altman analysis. The cohort for the study included 27 patients ranging in age from 2 days to 9 yr and in weight from 3.2 to 25 kg. A total of 101 sample sets were analyzed. The mean +/- SD absolute difference between the TC-CO2 and arterial CO2 was 1.7 +/- 1.4 mm Hg (range 0-9 mm Hg). The TC-CO2 to arterial CO2 difference was 0-2 mm Hg in 82 of 101 values (81%), 3-5 mm Hg in 18 of 101 values (18%), and >6 mm Hg in 1 of 101 values (1%). Linear regression analysis revealed a slope of 0.90, an r value of 0.9410, and an r(2) value of 0.8854 (P < 0.0001). Bland-Altman analysis revealed a bias of 0.58 mm Hg with a precision of +/-2.1 nam Hg when comparing the TC-CO2 with the arterial CO2. Implications: We conclude that, with certain caveats in mind, including the need to correlate the transcutaneous CO2 with an initial arterial CO2 value, transcutaneous CO2 monitoring can be used to estimate arterial CO2 in most neonates and children after cardiothoracic surgery.