Respiratory quotient estimations as additional prognostic tools in early septic shock

• Published in: Journal of clinical monitoring and computing Vol. 32; no. 6; pp. 1065 - 1072
• Main Authors: Mesquida, J., Saludes, P., Pérez-Madrigal, A., Proença, L., Cortes, E., Enseñat, L., Espinal, C., Gruartmoner, G.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-12-2018; Springer Nature B.V
• Subjects: Anesthesiology; Carbon dioxide; Correlation analysis; Critical Care Medicine; Health Sciences; Hemoglobin; Hypoxia; Intensive; Medicine; Medicine & Public Health; Mortality; Original Research; Oxygen content; Patients; Regression analysis; Restoration; Sepsis; Statistics for Life Sciences; Tissue hypoxia; Circulatory shock; Venous-to-arterial carbon dioxide difference; Hemodynamic monitoring
• ISSN: 1387-1307; 1573-2614
• DOI: 10.1007/s10877-018-0113-8

Central venous-to-arterial carbon dioxide difference (P
cva
CO
2
), and its correction by the arterial-to-venous oxygen content difference (P
cva
CO
2
/C
av
O
2
) have been proposed as additional tools to evaluate tissue hypoxia. Since the relationship between pressure and content of CO
2
(CCO
2
) might be affected by several factors, some authors advocate for the use of C
cva
CO
2
/C
av
O
2
. The aim of the present study was to explore the factors that might intervene in the difference between P
cva
CO
2
/C
av
O
2
and C
cva
CO
2
/C
av
O
2
, and to analyze their association with mortality. Observational study in a 30-bed mixed ICU. Fifty-two septic shock patients within the first 24 h of ICU admission were studied. After restoration of mean arterial pressure, hemodynamic and metabolic parameters were evaluated. A total of 110 sets of measurements were performed. Simultaneous P
cva
CO
2
/C
av
O
2
and C
cva
CO
2
/C
av
O
2
values were correlated, but agreement analysis showed a significant proportional bias. The difference between P
cva
CO
2
/C
av
O
2
and C
cva
CO
2
/C
av
O
2
was independently associated with pH, S
cv
O
2
, baseline C
cva
CO
2
/C
av
O
2
and hemoglobin. A stepwise regression analysis showed that pH was the single best predictor for the magnitude of such difference, with very limited effect of other variables. At inclusion, variables associated with ICU-mortality were lactate, pH, P
cva
CO
2
/C
av
O
2
, and the difference between P
cva
CO
2
/C
av
O
2
and C
cva
CO
2
/C
av
O
2
. Initial S
cv
O
2
, P
cva
CO
2
, C
cva
CO
2
/C
av
O
2
, and cardiac index were not different in survivors and non-survivors. In a population of early septic shock patients, simultaneous values of P
cva
CO
2
/C
av
O
2
and C
cva
CO
2
/C
av
O
2
were not equivalent, and the main determinant of the magnitude of the difference between these two parameters was pH. The P
cva
CO
2
/C
av
O
2
ratio was associated with ICU mortality, whereas C
cva
CO
2
/C
av
O
2
was not.