Accuracy of transcutaneous carbon dioxide monitoring in hypotensive patients

ObjectivesContinuous 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).MethodsAll 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.ResultsThe 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.ConclusionsPtcCO2 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.

Download Full-text

Agreement between arterial and capillary pH, pCO2 and lactate in patients in the emergency department

10.1101/2020.06.11.20128223 ◽

2020 ◽

Author(s):

V. Collot ◽

S. Malinverni ◽

E. Schweitzer ◽

J. Haltout ◽

P. Mols ◽

...

Keyword(s):

Lactic Acidosis ◽

Sensitivity And Specificity ◽

Blood Gas Analysis ◽

Gas Analysis ◽

Mean Difference ◽

Blood Gas ◽

Limits Of Agreement ◽

Study Objective ◽

Arterial Blood Gas ◽

Arterial Blood

AbstractStudy objectiveThe primary objective of the study was a quantitative analysis to assess the mean difference and 95% confidence interval of the difference between capillary and arterial blood gas analyses for pH, pCO2 and lactate. Secondary objective was to measure the sensitivity and specificity of capillary samples to detect altered pH, hypercarbia and lactic acidosis.MethodsAdults admitted to the ED for whom the treating physician deemed necessary an arterial blood gas analysis (BGA) were screened for inclusion. Simultaneous arterial and capillary samples were drawn for BGA. Agreement between the two methods for pH, pCO2 and lactate were studied with Bland-Altman bias plot analysis. Sensitivity, specificity, positive and negative predictive value as well as AUC were calculated for the ability of capillary samples to detect pH values outside normal ranges, hypercarbia and hyperlactatemia.Results197 paired analyses were included in the study. Mean difference for pH, between arterial and capillary BGA was 0.0095, 95% limits of agreement were -0.048 to 0.067. For pCO2, mean difference was -0.3 mmHg, 95% limits of agreement were -8.5 to 7.9 mmHg. Lactate mean difference was -0.93 mmol/L, 95% limits of agreement were -2.7 to 0.8 mmol/L. At a threshold of 7.34 for capillary pH had 98% sensitivity and 97% specificity to detect acidemia; at 45.9 mmHg capillary pCO2 had 89% sensitivity and 96% specificity to detect hypercarbia. Finally at a threshold of 3.5 mmol/L capillary lactate had 66% sensitivity to detect lactic acidosis.ConclusionCapillary measures of pH, pCO2 and lactate can’t replace arterial measurements although there is high concordance between the two methods for pH and pCO2 and moderate concordance for lactate. Capillary blood gas analysis had good accuracy when used as a screening tool to detect altered pH and hypercarbia but insufficient sensitivity and specificity when screening for lactic acidosis.

Download Full-text