Mahendran S, et al. - Given tissue hypoperfusion may be reflected by venoarterial carbon dioxide pressure (p_v-aCO₂) and content (C_v-aCO₂) differences, including the ratio to arteriovenous oxygen content difference (C_a-vO₂), and free energy shifts (-∆∆G_a-v), researchers undertook this single-centre, observational study to examine the links with alterations in cardiac output (CO) or oxygen consumption (VO₂) after fluid bolus administration. Participants were 89 adult postoperative cardiac surgical patients admitted to ICU. Arterial, central venous and mixed venous blood gas analyses were performed to ascertain p_v-aCO₂, C_v-aCO₂ and their ratios to C_a-vO₂ as well as the -∆∆G_a-v prior to and following a 250-500ml fluid bolus. Comparisons were performed between responses related to changes ≥ or < 15% in CO or VO₂. Findings revealed no link of venoarterial carbon dioxide gradients and associated calculations to evaluate the adequacy of tissue perfusion prior to a fluid bolus, with subsequent raises in CO or VO₂.