Background To describe 24‐hour fluid administration in emergency department (ED) patients with suspected infection. Methods A prospective, multicenter, observational study conducted in three Danish hospitals, January 20 to March 2, 2020. We included consecutive adult ED patients with suspected infection (drawing of blood culture and/or intravenous antibiotic administration within 6 hours of admission). Oral and intravenous fluids were registered for 24 hours. Primary outcome: 24‐hour total fluid volume. We used linear regression to investigate patient and disease characteristics' effect on 24‐hour fluids and to estimate the proportion of the variance in fluid administration explained by potential predictors. Results 734 patients had 24‐hour fluids available: 387 patients had simple infection, 339 sepsis, eight septic shock. Mean total 24‐hour fluid volumes were 3656 mL (standard deviation [SD]:1675), 3762 mL (SD: 1839), and 6080 mL (SD: 3978) for the groups, respectively. Fluid volumes varied markedly. Increasing age (mean difference [MD]: 60‐79 years: −470 mL [95% CI: −789, −150], +80 years; −974 mL [95% CI: −1307, −640]), do‐not‐resuscitate orders (MD: −466 mL [95% CI: −797, −135]), and preexisting atrial fibrillation (MD: −367 mL [95% CI: −661, −72) were associated with less fluid. Systolic blood pressure < 100 mmHg (MD: 1182 mL [95% CI: 820, 1543]), mean arterial pressure < 65 mmHg (MD: 1317 mL [95% CI: 770, 1864]), lactate ≥ 2 mmol/L (MD: 655 mL [95% CI: 306, 1005]), heart rate > 120 min (MD: 566 [95% CI: 169, 962]), low (MD: 1963 mL [95% CI: 813, 3112]) and high temperature (MD: 489 mL [95% CI: 234, 742]), SOFA score > 5 (MD: 1005 mL [95% CI: 501, 510]), and new‐onset atrial fibrillation (MD: 498 mL [95% CI: 30, 965]) were associated with more fluid. Clinical variables explained 37% of fluid variation among patients. Conclusions Patients with simple infection and sepsis received equal fluid volumes. Fluid volumes varied markedly, a variation that was partly explained by clinical characteristics.

New Findings What is the central question of this study?Invasive cardiovascular instrumentation can occur through closed‐ or open‐chest approaches. To what extent will sternotomy and pericardiotomy affect cardiopulmonary variables? What is the main finding and its importance?Opening of the thorax decreased mean systemic and pulmonary pressures. Left ventricular function improved, but no changes were observed in right ventricular systolic measures. No consensus or recommendation exists regarding instrumentation. Methodological differences risk compromising rigour and reproducibility in preclinical research. Abstract Animal models of cardiovascular disease are often evaluated by invasive instrumentation for phenotyping. As no consensus exists, both open‐ and closed‐chest approaches are used, which might compromise rigour and reproducibility in preclinical research. We aimed to quantify the cardiopulmonary changes induced by sternotomy and pericardiotomy in a large animal model. Seven pigs were anaesthetized, mechanically ventilated and evaluated by right heart catheterization and bi‐ventricular pressure–volume loop recordings at baseline and after sternotomy and pericardiotomy. Data were compared by ANOVA or the Friedmann test where appropriate, with post‐hoc analyses to control for multiple comparisons. Sternotomy and pericardiotomy caused reductions in mean systemic (−12 ± 11 mmHg, P = 0.027) and pulmonary pressures (−4 ± 3 mmHg, P = 0.006) and airway pressures. Cardiac output decreased non‐significantly (−1329 ± 1762 ml/min, P = 0.052). Left ventricular afterload decreased, with an increase in ejection fraction (+9 ± 7%, P = 0.027) and coupling. No changes were observed in right ventricular systolic function or arterial blood gases. In conclusion, open‐ versus closed‐chest approaches to invasive cardiovascular phenotyping cause a systematic difference in key haemodynamic variables. Researchers should adopt the most appropriate approach to ensure rigour and reproducibility in preclinical cardiovascular research.