Central venous-arterial pCO2 difference as a tool in resuscitation of septic patients
To investigate the interchangeability of mixed and central venous-arterial carbon dioxide differences and the relation between the central difference (pCO2 gap) and cardiac index (CI). We also investigated the value of the pCO2 gap in outcome prediction.
We performed a post hoc analysis of a well-defined population of 53 patients with severe sepsis or septic shock. Mixed and central venous pCO2 were determined earlier at a 6 h interval (T = 0 to T = 4) during the first 24 h after intensive care unit (ICU) admittance. The population was divided into two groups based on pCO2 gap (cut off value 0.8 kPa).
The mixed pCO2 difference underestimated the central pCO2 difference by a mean bias of 0.03± 0.32 kPa (95 % limits of agreement: −0.62–0.58 kPa). We observed a weak relation between pCO2 gap and CI. The in hospital mortality rate was 21 % (6/29) for the low gap group and 29 % (7/24) for the high gap group; the odds ratio was 1.6 (95 % CI 0.5–5.5), p = 0.53. At T = 4 the odds ratio was 5.3 (95 % CI 0.9–30.7); p = 0.08.
From a practical perspective, the clinical utility of central venous pCO2 values is of potential interest in determining the venous-arterial pCO2 difference. The likelihood of a bad outcome seems to be enhanced when a high pCO2 gap persists after 24 h of therapy.
KeywordsCentral venous-arterial pCO2 difference Cardiac index Septic shock Hemodynamics
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