Study design and patients
We did an ancillary analysis of the COVID-ICU study, a multicentre, prospective, cohort study conducted in 164 ICUs across three European countries (France, Belgium, and Switzerland), which described outcomes and risk factors of 90-day mortality of critically-ill COVID-19 patients.[1] The study was launched by the Réseau Européen de recherche en Ventilation Artificielle (REVA) and included all consecutive patients aged >16 years admitted to participating ICUs with laboratory-confirmed SARS-CoV-2 infection between February 25 and May 4, 2020. The ethics committees of the French Intensive Care Society (CE-SRLF 20-23), Belgium (2020-294), and Switzerland (BASEC #2020-00704) approved the study according to regulations for each participating country. All patients or next of kin were informed that patient data would be anonymously included in the COVID-ICU database. Patients and relatives had the possibility to decline participation in the study. In that case, data were not collected. The study followed the STROBE statement for the reporting of observational studies.[20]
All patients with laboratory-confirmed SARS-CoV-2 infection and available data regarding LST decisions and day-90 vital status were included in the study. Laboratory confirmation for SARS-Cov-2 was defined as a positive result of a real-time reverse transcriptase-polymerase chain reaction assay from either nasal or pharyngeal swabs, or lower respiratory tract samples.
Data collection
Day 1 was defined as the first day when the patient was present in the ICU at 10 am. Each day, study investigators completed a standardized electronic case report form. Data collected included baseline demographic characteristics within the first 24 h after ICU admission (day 1), comorbidities, simplified acute physiology score (SAPS-II),[21] sequential organ failure assessment (SOFA) score,[22] clinical frailty scale category,[23] date of first symptom/s, and ICU admission date. Local investigators documented the following information in a daily-expanded dataset: presence of a respiratory support device (oxygen mask, high-flow nasal cannula, noninvasive or invasive mechanical ventilation); arterial blood gases; FiO2; PaO2/FiO2 ratio; use of neuromuscular blockers or corticosteroids (regardless of the indication and the dose); and standard laboratory parameters. Data were also collected on complications and organ dysfunction during the ICU stay, including acute renal failure requiring renal replacement therapy, thromboembolic complications, ventilator-associated pneumonia and cardiac arrest, as well as detailed treatment limitation decisions.
If an LST limitation was decided upon during ICU stay, investigators were asked to record in detail the following items: cardiovascular support (vasopressors, do-not-resuscitate order); ventilatory support (invasive or non-invasive, intubation, tracheotomy, respiratory device settings, FiO2); renal replacement therapy; blood transfusion; enteral or parenteral nutrition; surgical emergency treatment; antibiotics; and intracranial pressure monitoring.
Definitions
Geographical areas (hereafter referred to as “regions”) were set as the national administrative divisions, ie, provinces for Belgium, departments for France, and cantons for Switzerland. To assess the strain on ICU capacities caused by the surge of COVID-19 patients, the ICU load was first computed at the regional level on a daily basis as:
This dynamic parameter was defined according to Bravata et al.[4] The ICU load at the patient level was finally defined as the mean ICU load in the region during the patient’s ICU stay. An ICU load of 100% reflected that all baseline ICU beds were occupied by COVID-19 patients, while an ICU load over 100% meant that the number of COVID-19 patients exceeded the baseline ICU hospitalization capacity. The number of baseline regional ICU beds before the pandemic and daily regional ICU bed occupancy during the first surge of the pandemic were based on data publicly available from official epidemiological reports on governmental websites including Public Health France and the French Ministry of Health, the Belgium Health Public Institute “Sciensano”, and the Swiss Federal Office of Public Health (see Online Data Supplement, p 4). Treatment limitations were categorized as LST withholding or withdrawal, according to the decision recorded in the daily-expanded dataset by local investigators (see Online Data Supplement, p 5). A patient with a decision of LST withdrawal after an LST withholding decision was classified in the “LST withdrawal” group.
Statistical analysis
Patients’ baseline characteristics, first 24-h in-ICU variables, treatments, organizational parameters, and ICU load at the patient level were described overall according to the following LST groups: 1) no LST; 2) LST withholding; and 3) LST withdrawal, whether or not preceded by an LST withholding decision. Continuous variables were described as medians (interquartile range [IQR]) and categorical variables as counts and percentages. Time to LST withholding and withdrawal decisions from ICU admission was estimated using a cumulative incidence function with ICU discharge and death during ICU stay as competing risks. Kaplan–Meier survival curves were plotted for the estimation of time to death from the first treatment limitation decision. In further analyses, the treatment limitation decision was dichotomized as LST withholding or withdrawal versus no limitation. Associations between variables and treatment limitation were estimated in a complete case analysis using a random intercept logistic regression model to account for the clustering of patients within centres. The following baseline variables obtained during the first 24 h in the ICU were included in the multivariable model and defined a priori (no statistical variable selection method was planned): age; gender; nursing home resident; clinical frailty scale (non-frail [1–3], pre-frail [4], frail [≥5]); body mass index ≥30 kg/m2; diabetes; hypertension; chronic heart failure; ischemic cardiomyopathy; chronic respiratory disease; chronic kidney disease; immunodepression; past hematologic disease; time between first signs and ICU admission; ICU admission period; ICU load; SOFA cardiovascular component ≥3; SOFA renal component ≥3; and ARDS severity during the first 24 h in the ICU. A sensitivity analysis was performed in centres including ≥10 patients.
Heterogeneity in withholding/withdrawal decisions between centres was investigated using meta-analytical methods to combine proportions on a logit scale and evaluated using a likelihood ratio test. Variability between centres was assessed with the tau statistic (standard deviation of the random effect).[24] This analysis was restricted to centres including 10 patients or more. Subgroup analyses were performed according to the number of patients included by centre (ie, 10-29 patients, 30-49 patients, ≥50 patients) and in centres including at least 10 patients aged 75 years or over.
Analyses were performed on a complete case analysis with no missing data imputation. Statistical significance was set at the two-sided 0.05 value for all analyses. Analyses were computed with R software, version R-4.0.2 (R Foundation for Statistical Computing, Vienna, Austria, https://www.r-project.org).
Role of the funding source
The funders of the study had no role in study design, data collection, data analysis, data interpretation, writing of the report, or the decision to submit for publication.