Methods
This is a cross-sectional observational study conducted at an ICU in the
Central-West region of Brazil. The study was approved by the local
Research Ethics Committee on February 26, 2021 (protocol number:
4.563.056/2021; Certificate of Presentation for Ethical Appraisal (CAAE)
number: 43454621.2.0000.5077). Data collection was performed from March
12, 2021 to May 26, 2022.
Patients admitted to the ICU, diagnosed with SARS-CoV‑2 infection,
requiring IMV, older than 18 years, and of both sexes, were included in
the study. Patients who had three or more incompletely analyzed
variables in their medical records, who had no record of death outcome
due to transfer to another institution, or who demonstrated unclear
association between deaths and SARS-CoV‑2 infection were excluded from
the study.
Patients who had clinical dyspnea and required supplemental oxygen, and
the ratio of partial arterial pressure of oxygen (PaO2)
and fraction of inspired oxygen (FiO2) ≤ 300 mmHg were
considered as having ARF7.
Data regarding sociodemographic characteristics, chronic diseases,
lifestyle, treatment, and hospital death were collected from medical
records. In-hospital death was considered an outcome or a dependent
variable. The considered sociodemographic variables were sex (male or
female) and age. The considered chronic disease variables were systemic
arterial hypertension; diabetes mellitus (DM); hypothyroidism;
hyperthyroidism; chronic obstructive pulmonary disease; cardiovascular
disease (CVD); cerebrovascular disease; mental health-related disease;
history of thrombosis; hepatitis A, B, and C; asthma; and liver failure.
The considered lifestyle variables were smoking, alcohol consumption,
and illicit drug use. The considered treatment variables were the use of
the prone position during hospitalization and the use of drugs, such as
dexamethasone, azithromycin, chloroquine, orhydroxychloroquine, and
low-molecular-weight heparin (enoxaparin).
For the sample size calculation, expected prevalence (or rate) of death
of 45% was used,8 with an error margin of 5.0% and a
95% confidence interval (95% CI) for a population of 300,000
inhabitants residing in the city of Rio Verde, State of Goiás, Brazil,
and its neighboring districts. Thus, the sample size required for this
analysis (prevalence calculation) was found to be 380 patients.
All statistical analyses were performed using the Stata statistical
package, version 16.0 (StataCorp LLC, College Station, TX, USA). The
variables were presented as absolute numbers (n) and relative
frequencies (%) with mean and standard deviation. Poisson’s regression
was used to calculate the prevalence ratio and 95% CI, andp -values was obtained using the Wald test. Variables with ap -value of <0.20 in bivariate analysis were included in
multiple hierarchical Poisson regression analyses, with robust variance
based on a hierarchical model9. The independent
variables in this hierarchical analysis were classified as follows: (I)
demographic data (gender and age), (II) chronic diseases (DM and mental
illness), (III) clinical features (pronation), and (IV) medication use
(azithromycin and heparin). Statistical significance was established
using a cutoff value of p < 0.05. Notably, thep -value of 0.000 indicates that the relationship is statistically
significant at the α = 0.05 level.
Variables without statistical power; that is, variables that after the
bivariate analysis presented n < 10 in any stratum, were
excluded from the multiple regression analysis10.
Additionally, the variables of hyperthyroidism, mental illness, asthma,
liver failure, smoking, and use of chloroquine/hydroxychloroquine were
excluded.