IntroductionSince normal or high central venous oxygen saturation (ScvO2) values cannot discriminate if tissue perfusion is adequate, integrating other markers of tissue hypoxia, such as central venous-to-arterial carbon dioxide difference (PcvaCO2 gap) has been proposed. In the present study, we aimed to evaluate the ability of the PcvaCO2 gap and the PcvaCO2/arterial-venous oxygen content difference ratio (PcvaCO2/CavO2) to predict lactate evolution in septic shock.MethodsObservational study. Septic shock patients within the first 24 hours of ICU admission. After restoration of mean arterial pressure, and central venous oxygen saturation, the PcvaCO2 gap and the PcvaCO2/CavO2 ratio were calculated. Consecutive arterial and central venous blood samples were obtained for each patient within 24 hours. Lactate improvement was defined as the decrease ≥ 10% of the previous lactate value.ResultsThirty-five septic shock patients were studied. At inclusion, the PcvaCO2 gap was 5.6 ± 2.1 mmHg, and the PcvaCO2/CavO2 ratio was 1.6 ± 0.7 mmHg · dL/mL O2. Those patients whose lactate values did not decrease had higher PcvaCO2/CavO2 ratio values at inclusion (1.8 ± 0.8vs. 1.4 ± 0.5, p 0.02). During the follow-up, 97 paired blood samples were obtained. No-improvement in lactate values was associated to higher PcvaCO2/CavO2 ratio values in the previous control. The ROC analysis showed an AUC 0.82 (p < 0.001), and a PcvaCO2/CavO2 ratio cut-off value of 1.4 mmHg · dL/mL O2 showed sensitivity 0.80 and specificity 0.75 for lactate improvement prediction. The odds ratio of an adequate lactate clearance was 0.10 (p < 0.001) in those patients with an elevated PcvaCO2/CavO2 ratio (≥1.4).ConclusionIn a population of septic shock patients with normalized MAP and ScvO2, the presence of elevated PcvaCO2/CavO2 ratio significantly reduced the odds of adequate lactate clearance during the following hours.

Background Non-invasive oxygenation strategies have a prominent role in the treatment of acute hypoxemic respiratory failure during the coronavirus disease 2019 (COVID-19). While the efficacy of these therapies has been studied in hospitalized patients with COVID-19, the clinical outcomes associated with oxygen masks, high-flow oxygen therapy by nasal cannula and non-invasive mechanical ventilation in critically ill intensive care unit (ICU) patients remain unclear. Methods In this retrospective study, we used the best of nine covariate balancing algorithms on all baseline covariates in critically ill COVID-19 patients supported with > 10 L of supplemental oxygen at one of the 26 participating ICUs in Catalonia, Spain, between March 14 and April 15, 2020. Results Of the 1093 non-invasively oxygenated patients at ICU admission treated with one of the three stand-alone non-invasive oxygenation strategies, 897 (82%) required endotracheal intubation and 310 (28%) died during the ICU stay. High-flow oxygen therapy by nasal cannula (n = 439) and non-invasive mechanical ventilation (n = 101) were associated with a lower rate of endotracheal intubation (70% and 88%, respectively) than oxygen masks (n = 553 and 91% intubated), p < 0.001. Compared to oxygen masks, high-flow oxygen therapy by nasal cannula was associated with lower ICU mortality (hazard ratio 0.75 [95% CI 0.58–0.98), and the hazard ratio for ICU mortality was 1.21 [95% CI 0.80–1.83] for non-invasive mechanical ventilation. Conclusion In critically ill COVID-19 ICU patients and, in the absence of conclusive data, high-flow oxygen therapy by nasal cannula may be the approach of choice as the primary non-invasive oxygenation support strategy.

Central venous-to-arterial carbon dioxide difference (PCO), and its correction by the arterial-to-venous oxygen content difference (PCO/CO) have been proposed as additional tools to evaluate tissue hypoxia. Since the relationship between pressure and content of CO (CCO) might be affected by several factors, some authors advocate for the use of CCO/CO. The aim of the present study was to explore the factors that might intervene in the difference between PCO/CO and CCO/CO, 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 PCO/CO and CCO/CO values were correlated, but agreement analysis showed a significant proportional bias. The difference between PCO/CO and CCO/CO was independently associated with pH, SO, baseline CCO/CO 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, PCO/CO, and the difference between PCO/CO and CCO/CO. Initial SO, PCO, CCO/CO, and cardiac index were not different in survivors and non-survivors. In a population of early septic shock patients, simultaneous values of PCO/CO and CCO/CO were not equivalent, and the main determinant of the magnitude of the difference between these two parameters was pH. The PCO/CO ratio was associated with ICU mortality, whereas CCO/CO was not.