ORIGINAL ARTICLE   Free access

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

DOI: 10.23736/S0375-9393.21.15245-9

Copyright © 2021 EDIZIONI MINERVA MEDICA

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