Critical care beyond organ support: the importance of geriatric rehabilitation.

Very old critically ill patients pose a growing challenge for intensive care. Critical illness and the burden of treatment in the intensive care unit (ICU) can lead to a long-lasting decline of functional and cognitive abilities, especially in very old patients. Multi-complexity and increased vulnerability to stress in these patients may lead to new and worsening disabilities, requiring careful assessment, prevention and rehabilitation. The potential for rehabilitation, which is crucial for optimal functional outcomes, requires a systematic, multi-disciplinary approach and careful long-term planning during and following ICU care. We describe this process and provide recommendations and checklists for comprehensive and timely assessments in the context of transitioning patients from ICU to post-ICU and acute hospital care, and review the barriers to the provision of good functional outcomes.

The association of premorbid conditions with 6-month mortality in acutely admitted ICU patients over 80 years.

BACKGROUND: Premorbid conditions influence the outcome of acutely ill adult patients aged 80 years and over who are admitted to the ICU. The aim of this study was to determine the influence of such premorbid conditions on 6 month survival. METHODS: Prospective cohort study in 242 ICUs from 22 countries including patients 80 years or above, admitted over a 6 months period to an ICU between May 2018 and May 2019. Only emergency (acute) ICU admissions in adult patients ≥ 80 years of age were eligible. Patients who were admitted after planned/elective surgery were excluded. We measured the Clinical Frailty Scale (CFS), the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE), disability with the Katz activities of daily living (ADL) score, comorbidities and a Polypharmacy Score (CPS). RESULTS: Overall, the VIP2 study included 3920 patients. During ICU stay 1191 patients died (30.9%), and another 436 patients (11.1%) died after ICU discharge but within the first 30 days of admission, and an additional 895 patients died hereafter but within the first 6 months after admission (22.8%). The 6 months mortality was 64%. The median CFS was 4 (IQR 3-6). Frailty (CFS ≥ 5) was present in 26.6%. Cognitive decline (IQCODE above 3.5) was found in 30.2%. The median IQCODE was 3.19. A Katz ADL of 4 or less was present in 27.7%. Patients who surviving > 6 months were slightly younger (median age survivors 84 with IQR 81-86) than patients dying within the first 6 months (median age 84, IQR 82-87, p = 0.013), were less frequently frail (CFS > 5 in 19% versus 34%, p < 0.01) and were less dependent based on their Katz activities of daily living measurement (median Katz score 6, IQR 5-6 versus 6 points, IQR 3-6, p < 0.01). CONCLUSIONS: We found that Clinical Frailty Scale, age, and SOFA at admission were independent prognostic factors for 6 month mortality after ICU admission in patients age 80 and above. Adding other geriatric syndromes and scores did not improve the model. This information can be used in shared-decision making. CLINICALTRIALS: gov: NCT03370692.

30-day mortality among very old patients admitted to European intensive care units for major trauma.

INTRODUCTION: Cases of major trauma in the very old (over 80 years) are increasingly common in the intensive care unit. Predicting outcome is challenging in this group of patients as chronological age is a poor marker of health and poor predictor of outcome. Increasingly, decisions are guided with the use of organ dysfunction scores of both the acute condition (e.g. Sequential Organ Failure Assessment (SOFA) score) and chronic health issues (e.g. clinical frailty scale, (CFS)). Recent work suggests that increased CFS is associated with a worse outcome in elderly major trauma patients. We aimed to test whether this association held true in the very old (over 80) or whether SOFA had a stronger association with 30-day outcome. METHODS: Data from the VIP-1 and VIP-2 studies for patients over 80 years old with major trauma admissions were merged. These participants were recruited from 20 countries across Europe. Baseline characteristics, level of care provided and outcome (ICU and 30-day mortality) were summarised. Uni- and multi- variable regression analysis were undertaken to determine associations between CFS and SOFA score in the first 24-hours, type of major trauma and outcomes. RESULTS: Of the 8062 acute patients recruited to the two VIP studies, 498 patients were admitted to intensive care because of major trauma. Median age was 84 years; median SOFA score was 6 (IQR 3,9) and median CFS was 3 (IQR 2,5). Survival to 30-days was 54%. Median and inter-quartile range of CFS was the same in survivors and non-survivors. In the logistic regression analysis, CFS was not associated with increased mortality. SOFA score (p<0.001) and trauma with head injury (p<0.01) were associated with increased mortality. CONCLUSIONS: Major trauma admissions in the very old are not uncommon and 30-day mortality is high. We found that CFS was not a helpful predictor of mortality. SOFA and trauma with head injury were associated with worse outcomes in this patient group.

The trajectory of very old critically ill patients.

The demographic shift, together with financial constraint, justify a re-evaluation of the trajectory of care of very old critically ill patients (VIP), defined as older than 80 years. We must avoid over- as well as under-utilisation of critical care interventions in this patient group and ensure the inclusion of health care professionals, the patient and their caregivers in the decision process. This new integrative approach mobilises expertise at each step of the process beginning prior to intensive care unit (ICU) admission and extending to long-term follow-up. In this review, several international experts have contributed to provide recommendations that can be universally applied. Our aim is to define a minimum core dataset of information to be shared and discussed prior to ICU admission and to facilitate the shared-decision-making process with the patient and their caregivers, throughout the patient journey. Documentation of uncertainty may contribute to a tailored level of care and ultimately to discussions around possible limitations of life sustaining treatments. The goal of ICU care is not only to avoid death, but more importantly to maintain an acceptable quality of life and functional autonomy after hospital discharge. Societal consideration is important to highlight, together with alternatives to ICU admission. We discuss challenges for the future and potential areas of research. In summary, this review provides a state-of-the-art current overview and aims to outline future directions to address the challenges in the treatment of VIP.

A Comparison of High and Usual Protein Dosing in Critically Ill Patients With Obesity: A Post Hoc Analysis of an International, Pragmatic, Single-Blinded, Randomized Clinical Trial.

OBJECTIVES: Across guidelines, protein dosing for critically ill patients with obesity varies considerably. The objective of this analysis was to evaluate whether this population would benefit from higher doses of protein. DESIGN: A post hoc subgroup analysis of the effect of higher protein dosing in critically ill patients with high nutritional risk (EFFORT Protein): an international, multicenter, pragmatic, registry-based randomized trial. SETTING: Eighty-five adult ICUs across 16 countries. PATIENTS: Patients with obesity defined as a body mass index (BMI) greater than or equal to 30 kg/m 2 ( n = 425). INTERVENTIONS: In the primary study, patients were randomized into a high-dose (≥ 2.2 g/kg/d) or usual-dose protein group (≤ 1.2 g/kg/d). MEASUREMENTS AND MAIN RESULTS: Protein intake was monitored for up to 28 days, and outcomes (time to discharge alive [TTDA], 60-d mortality, days of mechanical ventilation [MV], hospital, and ICU length of stay [LOS]) were recorded until 60 days post-randomization. Of the 1301 patients in the primary study, 425 had a BMI greater than or equal to 30 kg/m 2 . After adjusting for sites and covariates, we observed a nonsignificant slower rate of TTDA with higher protein that ruled out a clinically important benefit (hazard ratio, 0.78; 95% CI, 0.58-1.05; p = 0.10). We found no evidence of difference in TTDA between protein groups when subgroups with different classes of obesity or patients with and without various nutritional and frailty risk variables were examined, even after the removal of patients with baseline acute kidney injury. Overall, 60-day mortality rates were 31.5% and 28.2% in the high protein and usual protein groups, respectively (risk difference, 3.3%; 95% CI, -5.4 to 12.1; p = 0.46). Duration of MV and LOS in hospital and ICU were not significantly different between groups. CONCLUSIONS: In critically ill patients with obesity, higher protein doses did not improve clinical outcomes, including those with higher nutritional and frailty risk.

Frailty's influence on 30-day mortality in old critically ill ICU patients: a bayesian analysis evaluating the clinical frailty scale.

INTRODUCTION: Frailty is widely acknowledged as influencing health outcomes among critically ill old patients. Yet, the traditional understanding of its impact has predominantly been through frequentist statistics. We endeavored to explore this association using Bayesian statistics aiming to provide a more nuanced understanding of this multifaceted relationship. METHODS: Our analysis incorporated a cohort of 10,363 older (median age 82 years) patients from three international prospective studies, with 30-day all-cause mortality as the primary outcome. We defined frailty as Clinical Frailty Scale ≥ 5. A hierarchical Bayesian logistic regression model was employed, adjusting for covariables, using a range of priors. An international steering committee of registry members reached a consensus on a minimal clinically important difference (MCID). RESULTS: In our study, the 30-day mortality was 43%, with rates of 38% in non-frail and 51% in frail groups. Post-adjustment, the median odds ratio (OR) for frailty was 1.60 (95% CI 1.45-1.76). Frailty was invariably linked to adverse outcomes (OR > 1) with 100% probability and had a 90% chance of exceeding the minimal clinically important difference (MCID) (OR > 1.5). For the Clinical Frailty Scale (CFS) as a continuous variable, the median OR was 1.19 (1.16-1.22), with over 99% probability of the effect being more significant than 1.5 times the MCID. Frailty remained outside the region of practical equivalence (ROPE) in all analyses, underscoring its clinical importance regardless of how it is measured. CONCLUSIONS: This research demonstrates the significant impact of frailty on short-term mortality in critically ill elderly patients, particularly when the Clinical Frailty Scale (CFS) is used as a continuous measure. This approach, which views frailty as a spectrum, enables more effective, personalized care for this vulnerable group. Significantly, frailty was consistently outside the region of practical equivalence (ROPE) in our analysis, highlighting its clinical importance.

Limiting life-sustaining treatment for very old ICU patients: cultural challenges and diverse practices.

BACKGROUND: Decisions about life-sustaining therapy (LST) in the intensive care unit (ICU) depend on predictions of survival as well as the expected functional capacity and self-perceived quality of life after discharge, especially in very old patients. However, prognostication for individual patients in this cohort is hampered by substantial uncertainty which can lead to a large variability of opinions and, eventually, decisions about LST. Moreover, decision-making processes are often embedded in a framework of ethical and legal recommendations which may vary between countries resulting in divergent management strategies. METHODS: Based on a vignette scenario of a multi-morbid 87-year-old patient, this article illustrates the spectrum of opinions about LST among intensivsts with a special interest in very old patients, from ten countries/regions, representing diverse cultures and healthcare systems. RESULTS: This survey of expert opinions and national recommendations demonstrates shared principles in the management of very old ICU patients. Some guidelines also acknowledge cultural differences between population groups. Although consensus with families should be sought, shared decision-making is not formally required or practised in all countries. CONCLUSIONS: This article shows similarities and differences in the decision-making for LST in very old ICU patients and recommends strategies to deal with prognostic uncertainty. Conflicts should be anticipated in situations where stakeholders have different cultural beliefs. There is a need for more collaborative research and training in this field.

Validity of the total SOFA score in patients ≥ 80 years old acutely admitted to intensive care units: a post-hoc analysis of the VIP2 prospective, international cohort study.

BACKGROUND: Little is known about the performance of the Sequential Organ Failure Assessment (SOFA) score in older critically ill adults. We aimed to evaluate the prognostic impact of physiological disturbances in the six organ systems included in the SOFA score. METHODS: We analysed previously collected data from a prospective cohort study conducted between 2018 and 2019 in 22 countries. Consecutive patients ≥ 80 years old acutely admitted to intensive care units (ICUs) were eligible for inclusion. Patients were followed up for 30 days after admission to the ICU. We used logistic regression to study the association between increasing severity of organ dysfunction and mortality. RESULTS: The median SOFA score among 3882 analysed patients was equal to 6 (IQR: 4-9). Mortality was equal to 26.1% (95% CI 24.7-27.5%) in the ICU and 38.7% (95% CI 37.1-40.2%) at day 30. Organ failure defined as a SOFA score ≥ 3 was associated with variable adjusted odds ratios (aORs) for ICU mortality dependant on the organ system affected: respiratory, 1.53 (95% CI 1.29-1.81); cardiovascular 1.69 (95% CI 1.43-2.01); hepatic, 1.74 (95% CI 0.97-3.15); renal, 1.87 (95% CI 1.48-2.35); central nervous system, 2.79 (95% CI 2.34-3.33); coagulation, 2.72 (95% CI 1.66-4.48). Modelling consecutive levels of organ dysfunction resulted in aORs equal to 0.57 (95% CI 0.33-1.00) when patients scored 2 points in the cardiovascular system and 1.01 (0.79-1.30) when the cardiovascular SOFA equalled 3. CONCLUSIONS: Different components of the SOFA score have different prognostic implications for older critically ill adults. The cardiovascular component of the SOFA score requires revision.

Outcomes of patients aged ≥80 years with respiratory failure initially treated with non-invasive ventilation in European intensive care units before and during COVID-19 pandemic.

BACKGROUND: Non-invasive ventilation (NIV) has been commonly used to treat acute respiratory failure due to COVID-19. In this study we aimed to compare outcomes of older critically ill patients treated with NIV before and during the COVID-19 pandemic. METHODS: We analysed a merged cohort of older adults admitted to intensive care units (ICUs) due to respiratory failure. Patients were enrolled into one of two prospective observational studies: before COVID-19 (VIP2-2018 to 2019) and admitted due to COVID-19 (COVIP-March 2020 to January 2023). The outcomes included: 30-day mortality, intubation rate and NIV failure (death or intubation within 30 days). RESULTS: The final cohort included 1986 patients (1292 from VIP2, 694 from COVIP) with a median age of 83 years. NIV was used as a primary mode of respiratory support in 697 participants (35.1%). ICU admission due to COVID-19 was associated with an increased 30-day mortality (65.5% vs. 36.5%, HR 2.18, 95% CI 1.71 to 2.77), more frequent intubation (36.9% vs. 17.5%, OR 2.63, 95% CI 1.74 to 3.99) and NIV failure (76.2% vs. 45.3%, OR 4.21, 95% CI 2.84 to 6.34) compared to non-COVID causes of respiratory failure. Sensitivity analysis after exclusion of patients in whom life supporting treatment limitation was introduced during primary NIV confirmed higher 30-day mortality in patients with COVID-19 (52.5% vs. 23.4%, HR 2.64, 95% CI 1.83 to 3.80). CONCLUSION: The outcomes of patients aged ≥80 years treated with NIV during COVID-19 pandemic were worse compared then those treated with NIV in the pre-pandemic era.

COVID-19-associated pulmonary aspergillosis in mechanically ventilated patients: a prospective, multicentre UK study.

BACKGROUND: Invasive pulmonary aspergillosis is a complication of severe COVID-19, with regional variation in reported incidence and mortality. We describe the incidence, risk factors and mortality associated with COVID-19-associated pulmonary aspergillosis (CAPA) in a prospective, multicentre UK cohort. METHODS: From March 2020 to March 2021, 266 mechanically ventilated adults with COVID-19 were enrolled across 5 UK hospital intensive care units (ICUs). CAPA was defined using European Confederation for Medical Mycology and the International Society for Human and Animal Mycology criteria and fungal diagnostics performed on respiratory and serum samples. RESULTS: Twenty-nine of 266 patients (10.9%) had probable CAPA, 14 (5.2%) possible CAPA and none proven CAPA. Probable CAPA was diagnosed a median of 9 (IQR 7-16) days after ICU admission. Factors associated with probable CAPA after multivariable logistic regression were cumulative steroid dose given within 28 days prior to ICU admission (adjusted OR (aOR) 1.16; 95% CI 1.01 to 1.43 per 100 mg prednisolone-equivalent), receipt of an interleukin (IL)-6 inhibitor (aOR 2.79; 95% CI 1.22 to 6.48) and chronic obstructive pulmonary disease (COPD) (aOR 4.78; 95% CI 1.13 to 18.13). Mortality in patients with probable CAPA was 55%, vs 46% in those without. After adjustment for immortal time bias, CAPA was associated with an increased risk of 90-day mortality (HR 1.85; 95% CI 1.07 to 3.19); however, this association did not remain statistically significant after further adjustment for confounders (adjusted HR 1.57; 95% CI 0.88 to 2.80). There was no difference in mortality between patients with CAPA prescribed antifungals (9 of 17; 53%) and those who were not (7 of 12; 58%) (p=0.77). INTERPRETATION: In this first prospective UK study, probable CAPA was associated with corticosteroid use, receipt of IL-6 inhibitors and pre-existing COPD. CAPA did not impact mortality following adjustment for prognostic variables.

The impact of age-related syndromes on ICU process and outcomes in very old patients.

In this narrative review, we describe the most important age-related "syndromes" found in the old ICU patients. The syndromes are frailty, comorbidity, cognitive decline, malnutrition, sarcopenia, loss of functional autonomy, immunosenescence and inflam-ageing. The underlying geriatric condition, together with the admission diagnosis and the acute severity contribute to the short-term, but also to the long-term prognosis. Besides mortality, functional status and quality of life are major outcome variables. The geriatric assessment is a key tool for long-term qualitative outcome, while immediate severity accounts for acute mortality. A poor functional baseline reduces the chances of a successful outcome following ICU. This review emphasises the importance of using a geriatric assessment and considering the older patient as a whole, rather than the acute illness in isolation, when making decisions regarding intensive care treatment.

The clinical frailty scale - does it predict outcome of the very-old in UK ICUs?

Introduction: The age of patients admitted into critical care in the UK is increasing. Clinical decisions for very-old patients, usually defined as over 80, can be challenging. Clinicians are frequently asked to predict outcomes as part of discussions around the pros and cons of an intensive care unit (ICU) admission. Measures of overall health in old age, such as the clinical frailty scale (CFS), are increasingly used to help guide these discussions. We aimed to understand the characteristics of the very-old critically unwell population in the UK and the associations between frailty and outcome of an ICU admission in our healthcare system (National Health Service, NHS). Methods: Baseline characteristics, ICU interventions and outcomes (ICU- and 30-day mortality) were recorded for sequential admissions of very old patients to UK ICUs as part of the European VIP 1 and 2 studies. Patient characteristics, interventions and outcome measures were compared by frailty group using standard statistical tests. Multivariable logistic regression modelling was undertaken to test association between baseline characteristics, admission type and outcome. Results: 1858 participants were enrolled from 95 ICUs in the UK. The median age was 83. The median CFS was 4 (IQR 3-5). 30-day survival was significantly lower in the frail group (CFS > 4, 58%) compared to vulnerable (CFS = 4, 65%) and fit (CFS < 4 68%, p = .004). Sequential organ failure assessment (SOFA) score, reason for admission and CFS were all independently associated with increased 30-day mortality (p < .01). Conclusion: In the UK, frailty is associated with an increase in mortality at 30-days following an ICU admission. At moderate frailty (CFS 5-6), three out of every five patients admitted survived to 30-days. This is a similar mortality to septic shock.

The role of clinical phenotypes in decisions to limit life-sustaining treatment for very old patients in the ICU.

BACKGROUND: Limiting life-sustaining treatment (LST) in the intensive care unit (ICU) by withholding or withdrawing interventional therapies is considered appropriate if there is no expectation of beneficial outcome. Prognostication for very old patients is challenging due to the substantial biological and functional heterogeneity in that group. We have previously identified seven phenotypes in that cohort with distinct patterns of acute and geriatric characteristics. This study investigates the relationship between these phenotypes and decisions to limit LST in the ICU. METHODS: This study is a post hoc analysis of the prospective observational VIP2 study in patients aged 80 years or older admitted to ICUs in 22 countries. The VIP2 study documented demographic, acute and geriatric characteristics as well as organ support and decisions to limit LST in the ICU. Phenotypes were identified by clustering analysis of admission characteristics. Patients who were assigned to one of seven phenotypes (n = 1268) were analysed with regard to limitations of LST. RESULTS: The incidence of decisions to withhold or withdraw LST was 26.5% and 8.1%, respectively. The two phenotypes describing patients with prominent geriatric features and a phenotype representing the oldest old patients with low severity of the critical condition had the largest odds for withholding decisions. The discriminatory performance of logistic regression models in predicting limitations of LST after admission to the ICU was the best after combining phenotype, ventilatory support and country as independent variables. CONCLUSIONS: Clinical phenotypes on ICU admission predict limitations of LST in the context of cultural norms (country). These findings can guide further research into biases and preferences involved in the decision-making about LST. Trial registration Clinical Trials NCT03370692 registered on 12 December 2017.

Associations of anemia and blood transfusions with mortality in old, critically ill COVID-19 patients - Results from the prospective COVIP Study.

AIMS: Anemia is common in the old and often observed in critically ill patients. Increased age is associated with higher mortality following a COVID-19 infection, making old patients prone to poor outcomes. We investigated whether anemia at admission to the ICU or the need for blood transfusion was associated with 90-day mortality in older, critically ill COVID-19 patients. METHODS: In this prospective multicenter study, the 90-day mortality of COVID-19 patients≥70 years treated in 138 intensive care units (ICU) was analyzed. Associations between anemia (WHO definition) at admission and discharge from ICU and the use of red blood cell (RBC) transfusions with mortality were assessed. Hemoglobin thresholds of RBC transfusions in old, critically ill COVID-19 patients were recorded. RESULTS: In 493 patients (350 anemic, 143 non-anemic), anemia (WHO definition) at the time of ICU admission was not associated with impaired overall survival. Transfusion and severe anemia (hemoglobin≤10 g/dL) at ICU discharge were independently associated with a higher risk of 90-day mortality. CONCLUSION: The need for red blood cell transfusions and severe anemia at ICU discharge, but not at the timepoint of admission, were independently associated with 90-day mortality in critically-ill old COVID-19 patients.

The Clinical Frailty Scale for mortality prediction of old acutely admitted intensive care patients: a meta-analysis of individual patient-level data.

BACKGROUND: This large-scale analysis pools individual data about the Clinical Frailty Scale (CFS) to predict outcome in the intensive care unit (ICU). METHODS: A systematic search identified all clinical trials that used the CFS in the ICU (PubMed searched until 24th June 2020). All patients who were electively admitted were excluded. The primary outcome was ICU mortality. Regression models were estimated on the complete data set, and for missing data, multiple imputations were utilised. Cox models were adjusted for age, sex, and illness acuity score (SOFA, SAPS II or APACHE II). RESULTS: 12 studies from 30 countries with anonymised individualised patient data were included (n = 23,989 patients). In the univariate analysis for all patients, being frail (CFS ≥ 5) was associated with an increased risk of ICU mortality, but not after adjustment. In older patients (≥ 65 years) there was an independent association with ICU mortality both in the complete case analysis (HR 1.34 (95% CI 1.25-1.44), p < 0.0001) and in the multiple imputation analysis (HR 1.35 (95% CI 1.26-1.45), p < 0.0001, adjusted for SOFA). In older patients, being vulnerable (CFS 4) alone did not significantly differ from being frail. After adjustment, a CFS of 4-5, 6, and ≥ 7 was associated with a significantly worse outcome compared to CFS of 1-3. CONCLUSIONS: Being frail is associated with a significantly increased risk for ICU mortality in older patients, while being vulnerable alone did not significantly differ. New Frailty categories might reflect its "continuum" better and predict ICU outcome more accurately. TRIAL REGISTRATION: Open Science Framework (OSF: https://osf.io/8buwk/ ).

Diabetes mellitus is associated with 90-day mortality in old critically ill COVID-19 patients: a multicenter prospective observational cohort study.

BACKGROUND: Several studies have found an association between diabetes mellitus, disease severity and outcome in COVID-19 patients. Old critically ill patients are particularly at risk. This study aimed to investigate the impact of diabetes mellitus on 90-day mortality in a high-risk cohort of critically ill patients over 70 years of age. METHODS: This multicentre international prospective cohort study was performed in 151 ICUs across 26 countries. We included patients ≥ 70 years of age with a confirmed SARS-CoV-2 infection admitted to the intensive care unit from 19th March 2020 through 15th July 2021. Patients were categorized into two groups according to the presence of diabetes mellitus. Primary outcome was 90-day mortality. Kaplan-Meier overall survival curves until day 90 were analysed and compared using the log-rank test. Mixed-effect Weibull regression models were computed to investigate the influence of diabetes mellitus on 90-day mortality. RESULTS: This study included 3420 patients with a median age of 76 years were included. Among these, 37.3% (n = 1277) had a history of diabetes mellitus. Patients with diabetes showed higher rates of frailty (32% vs. 18%) and several comorbidities including chronic heart failure (20% vs. 11%), hypertension (79% vs. 59%) and chronic kidney disease (25% vs. 11%), but not of pulmonary comorbidities (22% vs. 22%). The 90-day mortality was significantly higher in patients with diabetes than those without diabetes (64% vs. 56%, p < 0.001). The association of diabetes and 90-day mortality remained significant (HR 1.18 [1.06-1.31], p = 0.003) after adjustment for age, sex, SOFA-score and other comorbidities in a Weibull regression analysis. CONCLUSION: Diabetes mellitus was a relevant risk factor for 90-day mortality in old critically ill patients with COVID-19. STUDY REGISTRATION: NCT04321265, registered March 19th, 2020.