Hourly Analysis of Mechanical Ventilation Parameters in Critically Ill Adult Covid-19 Patients: Association with Mortality.

Objective: There exists controversy about the pathophysiology and lung mechanics of COVID-19 associated acute respiratory distress syndrome (ARDS), because some report severe hypoxemia with preserved respiratory system mechanics, contrasting with "classic" ARDS. We performed a detailed hourly analysis of the characteristics and time course of lung mechanics and biochemical analysis of patients requiring invasive mechanical ventilation (IMV) for COVID-19-associated ARDS, comparing survivors and non-survivors. Methods: Retrospective analysis of the data stored in the ICU information system of patients admitted in our hospital ICU that required IMV due to confirmed SARS-CoV-2 pneumonia between March 5th and April 30th, 2020. We compare respiratory system mechanics and gas exchange during the first ten days of IMV, discriminating volume and pressure controlled modes, between ICU survivors and non-survivors. Results: 140 patients were included, analyzing 11 138 respiratory mechanics recordings. Global mortality was 38.6%. Multivariate analysis showed that age (OR 1.092, 95% (CI 1.014-1.176)) and need of renal replacement therapies (OR 10.15, (95% CI 1.58-65.11)) were associated with higher mortality. Previous use of Angiotensin Converting Enzyme inhibitor (ACEI)/angiotensin-receptor blockers (ARBs) also seemed to show an increased mortality (OR 4.612, (95% CI 1.19-17.84)) although this significance was lost when stratifying by age. Respiratory variables start to diverge significantly between survivors and non-survivors after the 96 to 120 hours (hs) from mechanical ventilation initiation, particularly respiratory system compliance. In non survivors, mechanical power at 24 and 96 hs was higher regardless ventilatory mode. Conclusions: In patients admitted for SARS-CoV-2 pneumonia and requiring mechanical ventilation, non survivors have different respiratory system mechanics than survivors in the first 10 days of ICU admission. We propose a checkpoint at 96-120 hs to assess patients improvement or worsening in order to consider escalating to extracorporeal therapies.

Urgent need for a rapid microbiological diagnosis in critically ill pneumonia

Severe lower respiratory tract infection is a common issue in Intensive Care Units that causes significant morbidityand mortality. The traditional diagnostic-therapeutic approachhas been grounded on taking respiratory samples and/or bloodcultures as soon as possible and starting empirical antibiotictherapy addressed to cover most likely pathogens based onthe presence of the patient’s risk factors for certain microorganisms, while waiting for the culture results in the following 48-72 hours to adequate the antibiotic treatment to thesensitivity profile of the isolated pathogen. Unfortunately, thisstrategy leads to use broad-spectrum antibiotics more timesthan necessary and does not prevent possible therapeuticfailures. The recent development of rapid molecular diagnostic techniques, based on real time polymerase chain reaction(RT-PCR), makes it possible to determine the causative agentand its main resistance pattern between 1 and 5 hours aftersampling (depending on each technique), with high precision,some of them reaching a negative predictive value greaterthan 98%, facilitating the very early withdrawal of unnecessary broad-spectrum antibiotics. Its high sensitivity can alsodetect unsuspected pathogens based on risk factors, allowingadequate treatment in the first hours of stay. This short review discusses the potential usefulness of these techniques incritically ill patients with lower respiratory tract infection andadvocates their immediate implementation in clinical practice. (AU)