RESUMO
Background: Limiting the fluid bolus (FB) volume may attenuate side effects, including hemodilution and increased filling pressures, but it may also reduce hemodynamic responsiveness. The minimum volume to create hemodynamic effects is considered to be 4 mL/kg. In critically ill patients, the hemodynamic effects of FB with this volume have not been adequately investigated and compared to higher quantities. We hypothesized that a standardized FB approach using 4 mL/kg has comparable hemodynamic and metabolic effects to the common practice of physician-determined FB in critically ill patients. Methods: We conducted post hoc analysis of two trials in non-selected critically ill patients with central venous-to-arterial CO2 tension (PvaCO2) >6 mmHg and no acute bleeding. All patients received crystalloids either at a physician-determined volume and rate or at 4 mL/kg pump-administered at 1.2 L/h. Cardiac index (CI) was calculated with transthoracic echocardiogram, and arterial and venous blood gas samples were assessed before and after FB. Endpoints were changes in CI and oxygen delivery (DO2) >15%. Results: A total of 47 patients were eligible for the study, 15 of whom received physician-determined FB and 32 of whom received standardized FB. Patients in the physician-determined FB group received 16 (12-19) mL/kg at a fluid rate of 1.5 (1.5-1.9) L/h, compared to 4.1 (3.7-4.4) mL/kg at a fluid rate of 1.2 (1.2-1.2) L/h (p < 0.01) in the standardized FB group. The difference in CI elevations between the two groups was not statistically significant (8.8% [-0.1-19.9%] vs. 8.4% [0.3-23.2%], p = 0.76). Compared to physician-determined FB, the standardized FB technique had similar probabilities of increasing CI or DO2 by >15% (odds ratios: 1.3 [95% CI: 0.37-5.18], p = 0.66 and 1.83 [95% CI: 0.49-7.85], p = 0.38). Conclusion: A standardized FB protocol (4 mL/kg at 1.2 L/h) effectively reduced the volume of fluid administered to critically ill patients without compromising hemodynamic or metabolic effects.
RESUMO
Background High-flow oxygen therapy (HFOT) has been widely used as an effective alternative to invasive mechanical ventilation (IMV) in some critically ill patients with COVID-19 pneumonia. This study aimed to compare different tools, including the respiratory rate and oxygenation (ROX) index, to predict HFOT failure in this setting. Methodology This single-center retrospective observational study was conducted from September to December 2020 and assessed COVID-19 patients who required HFOT as the first treatment at admission; HFOT failure was defined as IMV use. Prognostic scoring tools were as follows: the Sequential Organ Failure Assessment (SOFA), Acute Physiology And Chronic Health Evaluation (APACHE) II, and Simplified Acute Physiology Score (SAPS) III scores; C-reactive protein; lung consolidation percentage on chest CT; mean partial pressure of oxygen in arterial blood (PaO2)/fraction of inspired oxygen (FiO2) ratio; and ROX index and modified ROX index, calculated using PaO2 instead of blood oxygen saturation, within the first 24 hours after admission to the intensive care unit (ICU). These scores were analyzed using a multivariate Cox proportional hazard model; optimal cutoffs were computed using the R system for statistical computing. Results The study enrolled 52 patients, 31 (60%) of whom experienced HFOT failure. The best predictors of HFOT failure measured 24 hours after HFOT initiation were as follows: PaO2/FiO2 (threshold 123.6, sensitivity 87%, specificity 81%, hazard ratio [HR] 7.76, and 95% confidence interval [CI] 2.39-17.1); ROX index (threshold 5.63, sensitivity 68%, specificity 95%, HR 6.18, and 95% CI 2.54-13.4); and modified ROX index (threshold 4.94, sensitivity 81%, specificity 90%, HR 8.16, and 95% CI 3.16-21.5) (P < 0.001 for all). Conclusions Early assessment of the ROX index, modified ROX index, and PaO2/FiO2 ratio can adequately predict, with high accuracy, HFOT failure in COVID-19 patients. Because thresholds remain debated and are still not sufficiently validated, we advocate using them with caution for clinical decision-making in this context.
