Central venous-to-arterial carbon dioxide difference combined with arterial-to-venous oxygen content difference (PCO/CO) reflects microcirculatory oxygenation alterations in early septic shock.

PURPOSE

To explore the relationship between central venous-to-arterial carbon dioxide difference (PCO), PCO/arterial-venous oxygen content difference ratio (PCO/CO) and the microcirculatory status, evaluated by using near-infrared spectroscopy, in septic shock patients.

METHODS

Observational study in a 30-bed mixed ICU. Fifty septic shock patients within the first 24 h of ICU admission were studied. After restoration of mean arterial pressure, hemodynamic, metabolic and microcirculatory parameters were simultaneously evaluated. Local tissue oxygen saturation (StO), and local hemoglobin index (THI) were measured on the thenar eminence by means of near-infrared spectroscopy. A transient vascular occlusion test was performed in order to obtain StO deoxygenation rate (DeO), local oxygen consumption (nirVO), and reoxgenation rate (ReO).

RESULTS

At inclusion, increased PCO values were associated with lower StO and THI, whereas increased PCO/CO values were associated with lower DeO, nirVO, and ReO. Multiple regression models confirmed the association between PCO/CO and nirVO, while PCO was only related to CI, and not to microcirculatory parameters.

CONCLUSIONS

In a population of early septic shock patients, increases in PCO and PCO/CO reflected different alterations at the microcirculatory level. While PCO was related to global flow, the PCO/CO ratio was associated to impaired local oxygen utilization and diminished microvascular reactivity.