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ORIGINAL ARTICLE   Free accessfree

Minerva Anestesiologica 2021 March;87(3):325-33

DOI: 10.23736/S0375-9393.21.15245-9


language: English

Prevalence and outcome of silent hypoxemia in COVID-19

Mattia BUSANA 1 , Alessio GASPERETTI 2, Lorenzo GIOSA 3, Giovanni B. FORLEO 4, Marco SCHIAVONE 4, Gianfranco MITACCHIONE 5, Cecilia BONINO 4, Paolo VILLA 4, Massimo GALLI 4, Claudio TONDO 2, Ardan SAGUNER 6, Peter STEIGER 6, Antonio CURNIS 5, Antonio DELLO RUSSO 7, Francesco PUGLIESE 8, Massimo MANCONE 9, John J. MARINI 10, Luciano GATTINONI 1

1 Department of Anesthesiology, Intensive Care and Emergency Medicine, Medical University of Göttingen, Göttingen, Germany; 2 Monzino Cardiology Center, IRCCS, Milan, Italy; 3 Department of Surgical Sciences, Città della Salute e della Scienza, Turin, Italy; 4 Luigi Sacco Hospital, Milan, Italy; 5 Spedali Civili Hospital, University of Brescia, Brescia, Italy; 6 University Hospital of Zurich, Zurich, Switzerland; 7 Clinic of Cardiology and Arithmology, Department of Biomedical Sciences and Public Health, Umberto I-Lancisi-Salesi University Hospital, Marche Polytechnic University, Ancona, Italy; 8 Department of General Surgery, Paride Stefanini Surgical Specialties, Sapienza University, Rome, Italy; 9 Department of Clinical Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy; 10 Department of Pulmonary and Critical Care Medicine, University of Minnesota and Regions Hospital, Minneapolis, MN, USA

BACKGROUND: In the early stages of COVID-19 pneumonia, hypoxemia has been described in absence of dyspnea (“silent” or “happy” hypoxemia). Our aim was to report its prevalence and outcome in a series of hypoxemic patients upon Emergency Department admission.
METHODS: In this retrospective observational cohort study we enrolled a study population consisting of 213 COVID-19 patients with PaO2/FiO2 ratio <300 mmHg at hospital admission. Two groups (silent and dyspneic hypoxemia) were defined. Symptoms, blood gas analysis, chest X-ray (CXR) severity, need for intensive care and outcome were recorded.
RESULTS: Silent hypoxemic patients (68-31.9%) compared to the dyspneic hypoxemic patients (145-68.1%) showed greater frequency of extra respiratory symptoms (myalgia, diarrhea and nausea) and lower plasmatic LDH. PaO2/FiO2 ratio was 225±68 mmHg and 192±78 mmHg in silent and dyspneic hypoxemia respectively (P=0.002). Eighteen percent of the patients with PaO2/FiO2 from 50 to 150 mmHg presented silent hypoxemia. Silent and dyspneic hypoxemic patients had similar PaCO2 (34.2±6.8 mmHg vs. 33.5±5.7 mmHg, P=0.47) but different respiratory rates (24.6±5.9 bpm vs. 28.6±11.3 bpm respectively, P=0.002). Even when CXR was severely abnormal, 25% of the population was silent hypoxemic. Twenty-six point five percent and 38.6% of silent and dyspneic patients were admitted to the ICU respectively (P=0.082). Mortality rate was 17.6% and 29.7% (log-rank P=0.083) in silent and dyspneic patients.
CONCLUSIONS: Silent hypoxemia is remarkably present in COVID-19. The presence of dyspnea is associated with a more severe clinical condition.

KEY WORDS: COVID-19; Respiratory distress syndrome; Hypoxia; Emergency service, hospital

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