Accuracy of transcutaneous carbon dioxide monitoring in hypotensive patients.

OBJECTIVES

Continuous blood gas monitoring is frequently necessary in critically ill patients. Our aim was to assess the accuracy of transcutaneous CO₂ tension (PtcCO₂) monitoring in the emergency department (ED) assessment of hypotensive patients by comparing it with the gold standard of arterial blood gas analysis (ABGA).

METHODS

All patients receiving PtcCO₂ monitoring in the ED were included. We excluded paediatric patients, patients with no ABGA results during a hypotensive event, patients whose ABGA was not performed simultaneously with PtcCO₂ monitoring, and patients who received sodium bicarbonate for resuscitation. The included patients were classified into hypotensive patients and normotensive patients. A hypotensive patient was defined as a patient showing a mean arterial pressure under 60 mm Hg. The agreement in measurement between PaCO₂ tension (PaCO₂) and PtcCO₂ were investigated in both groups.

RESULTS

The mean difference between PaCO₂ and PtcCO₂ was 2.1 mm Hg, and the Bland-Altman limits of agreement (bias ± 1.96 SD) ranged from -15.6 to 19.7 mm Hg in the 28 normotensive patients. The mean difference between PaCO₂ and PtcCO₂ was 1.1 mm Hg, and the Bland-Altman limits of agreement (bias ± 1.96 SD) ranged from -19.5 to 21.7 mm Hg in the 26 hypotensive patients. The weighted κ values were 0.64 in the normotensive patients and 0.60 in the hypotensive patients.

CONCLUSIONS

PtcCO₂ monitoring showed wider limits of agreement with PaCO₂ in urgent situations in the ED environment. However, acutely developed hypotension does not affect the accuracy of PtcCO₂ monitoring.