Predictive value of veno-arterial carbon dioxide partial pressure difference and central venous oxygen saturation for fluid administration and mortality in critically ill patients with extensive burns.

OBJECTIVES

Guiding fluid therapy in severely burned patients presents complex challenges, combining elements of both distributive and hypovolemic shock, accompanied by cardiovascular dysfunction. Whereas parts of hemodynamic assessment in septic shock such as central venous oxygen saturation (ScvO2) and the arterial-venous carbon dioxide (CO2) partial pressure difference (ΔpCO2 = pcvCO2 - paCO2) can both be used as indicators of hypoperfusion, they are not part of the standard clinical assessment of severely burned patients. The aim of this retrospective study was thus to investigate whether the ΔpCO2 and ScvO2 in severely burned patients correlates with fluid administration and mortality.

METHODS

Retrospective analysis of severely burned patients with burns larger than 20 % total body surface area (TBSA) admitted between 01/2017 and 06/2021 to the Burns Center of the University Hospital Zurich, Switzerland. Patients were treated according to international guidelines and in-house standards and ΔpCO2 and ScvO2 were assessed at least once within the first 24 h of intensive care unit admission.

RESULTS

In total 69 patients were included in this analysis. The median ΔpCO2 and ScvO2 were 1.16 kPa [inter-quartile range IQR, 0.82 - 1.50] and 76 % [IQR, 71 - 81]. This translated to an abnormally elevated ΔpCO2 (>0.8 kPa) in 53 (77 %) and an abnormally reduced ScvO2 (<70 %) in 13 (19 %) patients. Initial ΔpCO2, but not ScvO2, was non-linearly associated with intravenous fluid administration in the following 24 h (estimate 9.6 L [95 % confidence interval CI, 4.1 - 15.2], p = 0.001) and 48 h (estimate 6.0 L [95 % CI, 0.3 - 11.8], p = 0.039). Both initial ΔpCO2 (logarithmic odds ratio OR 4.3 [95 % CI, 1.1 - 20.9], p = 0.048) as well as ScvO2 (OR 0.1 [95 % CI, 0 - 0.42], p = 0.034) were non-linearly associated with in-hospital mortality. However, the best association with mortality was achieved by combining ΔpCO2 and ScvO2, with patients presenting with abnormalities in both ΔpCO2 and ScvO2 having a predicted mortality of 46 % [95 % CI, 23-71].

CONCLUSION

In severely burned patients, both ΔpCO2 and ScvO2 are associated with the extent and severity of burns as well as with in-hospital mortality. However, only ΔpCO2 seems to possess potential as a predictor of fluid administration. A multimodal approach to fluid resuscitation including both parameters may show promise in severely burned patients; however, further prospective studies are required to define optimal thresholds and validate its integration into clinical fluid resuscitation practice.