Hospital trajectories and early predictors of clinical outcomes differ between SARS-CoV-2 and influenza pneumonia.

BACKGROUND: A comparison of pneumonias due to SARS-CoV-2 and influenza, in terms of clinical course and predictors of outcomes, might inform prognosis and resource management. We aimed to compare clinical course and outcome predictors in SARS-CoV-2 and influenza pneumonia using multi-state modelling and supervised machine learning on clinical data among hospitalised patients. METHODS: This multicenter retrospective cohort study of patients hospitalised with SARS-CoV-2 (March-December 2020) or influenza (Jan 2015-March 2020) pneumonia had the composite of hospital mortality and hospice discharge as the primary outcome. Multi-state models compared differences in oxygenation/ventilatory utilisation between pneumonias longitudinally throughout hospitalisation. Differences in predictors of outcome were modelled using supervised machine learning classifiers. FINDINGS: Among 2,529 hospitalisations with SARS-CoV-2 and 2,256 with influenza pneumonia, the primary outcome occurred in 21% and 9%, respectively. Multi-state models differentiated oxygen requirement progression between viruses, with SARS-CoV-2 manifesting rapidly-escalating early hypoxemia. Highly contributory classifier variables for the primary outcome differed substantially between viruses. INTERPRETATION: SARS-CoV-2 and influenza pneumonia differ in presentation, hospital course, and outcome predictors. These pathogen-specific differential responses in viral pneumonias suggest distinct management approaches should be investigated. FUNDING: This project was supported by NIH/NCATS UL1 TR002345, NIH/NCATS KL2 TR002346 (PGL), the Doris Duke Charitable Foundation grant 2015215 (PGL), NIH/NHLBI R35 HL140026 (CSC), and a Big Ideas Award from the BJC HealthCare and Washington University School of Medicine Healthcare Innovation Lab and NIH/NIGMS R35 GM142992 (PS).

Sympathetic stimulation increases serum lactate concentrations in patients admitted with sepsis: implications for resuscitation strategies.

BACKGROUND: Diametrically opposed positions exist regarding the deleterious effects of elevated lactate. There are data suggesting that it is a detrimental proxy for tissue hypoperfusion and anaerobic metabolism in sepsis and an alternative viewpoint is that some of the hyperlactatemia produced maybe adaptive. This study was conducted to explore the relationship between serum lactate levels, mean arterial blood pressure (MAP), and sympathetic stimulation in patients with sepsis. METHODS: Retrospective analysis of prospectively collected clinical data from four community-based hospitals and one academic medical center. 8173 adults were included. Heart rate (HR) was used as a surrogate marker of sympathetic stimulation. HR, MAP, and lactate levels were measured upon presentation. RESULTS: MAP and HR interacted to affect lactate levels with the highest levels observed in patients with low MAP and high HR (3.6 mmol/L) and the lowest in patients with high MAP and low HR (2.2 mmol/L). The overall mortality rate was 12.4%. Each 10 beats/min increase in HR increased the odds of death 6.0% (95% CI 2.6% to 9.4%), each 1 mmol/L increase in lactate increased the odds of death 20.8% (95% CI 17.4% to 24.2%), whereas each 10 mmHg increase in MAP reduced the odds of death 12.3% (95% CI 9.2% to 15.4%). However, HR did not moderate or mediate the association between lactate and death. CONCLUSIONS: In septic patients, lactate production was associated with increased sympathetic activity (HR ≥ 90) and hypotension (MAP < 65 mmHg) and was a significant predictor of mortality. Because HR, lactate, and MAP were associated with mortality, our data support the present strategy of using these measurements to gauge severity of illness upon presentation. Since HR did not moderate or mediate the association between lactate and death, criticisms alleging that lactate caused by sympathetic stimulation is adaptive (i.e., less harmful) do not appear substantiated.

Sepsis, the Administration of IV Fluids, and Respiratory Failure: A Retrospective Analysis-SAIFR Study.

BACKGROUND: Although resuscitation with IV fluids is the cornerstone of sepsis management, consensus regarding their association with improvement in clinical outcomes is lacking. RESEARCH QUESTION: Is there a difference in the incidence of respiratory failure in patients with sepsis who received guideline-recommended initial IV fluid bolus of 30 mL/kg or more conservative resuscitation of less than 30 mL/kg? STUDY DESIGN AND METHODS: This was a retrospective analysis of prospectively collected clinical data conducted at an academic medical center in Omaha, Nebraska. We abstracted data from 214 patients with sepsis admitted to a single academic medical center between June 2017 and June 2018. Patients were stratified by receipt of guideline-recommended fluid bolus. The primary outcome was respiratory failure defined as an increase in oxygen flow rate or more intense oxygenation and ventilation support; oxygen requirement and volume were measured at admission, 6 h, 12 h, 24 h, and at discharge. Subgroup analyses were conducted in high-risk patients with congestive heart failure (CHF) as well as those with chronic kidney disease (CKD). RESULTS: A total of 62 patients (29.0%) received appropriate bolus treatment. The overall rate of respiratory failure was not statistically different between patients who received appropriate bolus or did not (40.3% vs 36.8%; P = .634). Likewise, no differences were observed in time to respiratory failure (P = .645) or risk of respiratory failure (adjusted hazard ratio, 1.1 [95% CI, 0.7-1.7]; P = .774). Results were similar within the high-risk CHF and CKD subgroups. INTERPRETATION: In this single-center retrospective study, we found that by broadly defining respiratory failure as an increase in oxygen requirements, a conservative initial IV fluid resuscitation strategy did not correlate with decreased rates of hypoxemic respiratory failure.

Sepsis and the Obesity Paradox: Size Matters in More Than One Way.

OBJECTIVES: Multiple studies have demonstrated an obesity paradox such that obese ICU patients have lower mortality and better outcomes. We conducted this study to determine if the mortality benefit conferred by obesity is affected by baseline serum lactate and mean arterial pressure. DESIGN: Retrospective analysis of prospectively collected clinical data. SETTING: Five community-based and one academic medical center in the Omaha, NE. PATIENTS: 7,967 adults hospitalized with sepsis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were categorized by body mass index as underweight, normal weight, overweight, or obese. Multivariable logistic regression models were used to estimate the odds of in-hospital death by body mass index category; two-way interactions between body mass index and each covariate were also evaluated. Subgroup and sensitivity analyses were conducted using an ICU cohort and Acute Physiology and Chronic Health Evaluation III scores, respectively. The overall unadjusted mortality rate was 12.1% and was consistently lower in higher body mass index categories (all comparisons, p < 0.007). The adjusted mortality benefit observed in patients with higher body mass index was smaller in patients with higher lactate levels with no mortality benefit in higher body mass index categories observed at lactate greater than 5 mmol/L. By contrast, the association between lower MAP and higher mortality was constant across body mass index categories. Similar results were observed in the ICU cohort. Finally, the obesity paradox was not observed after including Acute Physiology and Chronic Health Evaluation III scores as a covariate. CONCLUSIONS: Our retrospective analysis suggests that although patient size (i.e., body mass index) is a predictor of in-hospital death among all-comers with sepsis-providing further evidence to the obesity paradox-it adds that illness severity is critically important whether quantified as higher lactate or by Acute Physiology and Chronic Health Evaluation III score. Our results highlight that the obesity paradox is more than a simple association between body mass index and mortality and reinforces the importance of illness severity.