Corona-virus Disease 2019 (Covid-19) is a global pandemic providing one of the biggest challenges for critical care medicine. Mortality from disease is much greater in elderly males, many of whom succumb to acute respiratory distress syndrome (ARDS) triggered by the viral infection. Since there is no specific antiviral treatment against Covid-19, new strategies are urgently needed. Selenium (Se) is an essential trace element with antioxidant, and immunomodulatory effects. Poor nutritional status increases pathogenicity of viruses and low Se in particular can be a determinant of viral virulence. In the last decade Se pharmaconutrition studies from ourselves and others demonstrated some improvement in overall mortality, reduced incidence of ventilator associated pneumonia (VAP) and infectious complications such as ARDS in the critically ill. Consequently, we postulate that intravenous Se therapy, could be part of the therapeutic fight against Covid-19 in ICU patients with ARDS and that outcomes could be affected by age, sex, and body weight.
Our working hypothesis addresses the question: Could high-dose selenite pharmaconutrition as an early pharmacological intervention, be effective at reducing the incidence and the progression from type 1 respiratory failure (non ARDS) to severe ARDS, multiorgan failure, and new infectious complications in Covid-19 patients?
At the end of 2019, in the city of Wuhan, the Chinese health authorities reported the first cases of a potentially fatal disease in humans, characterized by severe pneumonia and acute respiratory failure due to a novel coronavirus, named severe acute respiratory syndrome coronavirus 2 (SARS-Cov2) [ 
Reducing the incidence of severe ARDS, multiorgan failure, and new infectious complications, especially in elderly males where micronutrient deficiencies have been associated with severe adverse events during viral infections is a worthwhile aim [8, 9] . In this clinical scenario, early repletion of micronutrients such as Selenium (Se) should be a mandatory part of critical care nutrition.
Specifically, we would argue that pharmaconutrition with high-dose Se, as intravenous sodium selenite, is worthy of re-investigation.
Se is an essential trace element for humans, present in selenoproteins as the Reactive oxygen species (ROS) and reactive nitrogen species (RNS), including free radicals, increase expression of proinflammatory cytokines such as IL-6, and TNF- through upregulation of nuclear factor-kappa B (NF-κB) activity
where the Se status of the host may play a role in viral evolution, which has been associated with sepsis [11, 12] . This trial has a number of shortcomings. There was a markedly uneven distribution of patients, with for example, significantly more high risk sepsis patients requiring renal replacement therapy in the Se group. Inexplicitly, the mortalities observed (approx. 25% in all groups) were significantly lower than the 40% expected mortality in German ICUs [26] , raising questions about the basic assumptions in the study protocol design. The intention to treat analysis also found a statistically significant interaction between Se and PCT, which had previously been reported [27] . This interaction adds further confusion to the results interpretation and is considered a major limitation of the study. On the other hand, ,the American Society of Parenteral and Enteral Nutrition based on BMI; evaluating any sex differences in metabolism; investigating any age-related influences on drug efficacy.
The first step will be to better understand the PK and PD involved and explore report that overweight and obese patients, despite their younger age (67.0±12.6 years) were more likely to be admitted to ICU. Moreover, they had a higher need for non-invasive ventilation for pneumonia than normal weight patients aged 76.1±13.0 years, p<0.01) [40] . Further support for our contention that any future pharmacological therapy should be administered on the basis of the weight and/or BMI of the patient.
In the developed world more than 10% of the population is over 65 years with a male to female ratio of 0.75 and by 2030, one in five people will be classified as Old (75-84y) or Old Old (85y+). Classical drug PK take into consideration changes with Age in Adsorption, Distribution, Metabolism and Excretion "ADME" In a sub group analysis of data from the REDOXS study, Heyland et al. [24] showed that antioxidant (Se) supplementation actually improved 28 day mortality for those under 65y but not for those older patients. Age and sex differences are not immediately obvious in the SISPCT [25] study where the mean age was 65y but the M:F ratio was 0.6 with over 4 fold differences in daily doses and according to the authors, age and the disease severity marker differed considerably between the study groups. Clearly age and sex differences have been an 'invisible' confounder in many pharmaconutrition studies. Now, in the Covid-19 era, it is surely not a coincidence that age and sex differences are increasingly being identified as important factors influencing the severity of the response to the virus.
Simultaneous to the new PK/PD studies, we propose that large-scale RCT aimed at addressing the questions of Age, Sex, BMI and optimum posology need to be designed. Groups of severely ill Covid-19 patients admitted to the ICU, will receive an initial loading dose of high dose iv sodium selenite, followed by Se monotherapy by parenteral route starting as soon as possible after admission to the ICU for up to 14 days with follow up on Se status and outcome measures for up to 100 days.
We believe there is sufficient evidence on the anti-inflammatory, immunological and antioxidant properties of Se that allows us to initiate further in depth investigations into metabolic and clinical aspects of Se pharmaconutrition as adjuvant therapy aimed at combating this global pandemic.
William Manzanares: conceptualization, methodology, writing original and final draft.