Background & Aims Severe forms of COVID-19 are associated with systemic inflammation and hypercatabolism. We compared the time course of the size and quality of both rectus femoris and diaphragm muscles between critically-ill, COVID-19 survivors and non-survivors, and explored the correlation between the change in muscles size and quality with the amount of nutritional support delivered and the cumulative fluid balance. Methods Prospective observational study in the general ICU of a tertiary care hospital for COVID-19. The right rectus femoris cross-sectional area and the right diaphragm thickness, as well as their echodensities were assessed within 24 hours from ICU admission and on day 7. Anthropometric and biochemical data, respiratory mechanics and gas exchange, daily fluid balance and the amount of calories and proteins administered were recorded. Results 28 patients were analysed (age 65±10 years, 80% males, BMI 30.0±7.8). Rectus femoris and diaphragm sizes were significantly reduced at day 7 (-26.1 [-37.8;-15.2] and -29.2 [-37.8;-19.6]%, respectively) and this reduction was significantly higher in non-survivors. Both rectus femoris and diaphragm echodensity were significantly increased at day 7, with a significantly higher increase in non-survivors. The change in both rectus femoris and diaphragm size at day 7 was related to the cumulative protein deficit (R=0.664, p<0.001 and R=0.640, p<0.001, respectively), while the change in rectus femoris and diaphragm echodensity was related to the cumulative fluid balance (R=0.734, p<0.001 and R=0.646, p<0.001, respectively) Conclusions Early changes in muscle size and quality seem related to the outcome of critically-ill, COVID-19 patients, and be influenced by nutritional and fluid management strategies.

Maintaining spontaneous breathing has both potentially beneficial and deleterious consequences in patients with acute respiratory failure, depending on the balance that can be obtained between the protecting and damaging effects on the lungs and the diaphragm. Neurally adjusted ventilatory assist (NAVA) is an assist mode, which supplies the respiratory system with a pressure proportional to the integral of the electrical activity of the diaphragm. This proportional mode of ventilation has the theoretical potential to deliver lung- and respiratory-muscle-protective ventilation by preserving the physiologic defense mechanisms against both lung overdistention and ventilator overassistance, as well as reducing the incidence of diaphragm disuse atrophy while maintaining patient–ventilator synchrony. This narrative review presents an overview of NAVA technology, its basic principles, the different methods to set the assist level and the findings of experimental and clinical studies which focused on lung and diaphragm protection, machine–patient interaction and preservation of breathing pattern variability. A summary of the findings of the available clinical trials which investigate the use of NAVA in acute respiratory failure will also be presented and discussed.

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<b><i>Background:</i></b> Acute kidney injury (AKI) is common in the postoperative period and is associated with negative patient outcomes. The definition of perioperative hypotension is wide, but it is associated with various complications, including AKI. <b><i>Summary:</i></b> Preclinical data suggest that sustained severe renal hypoperfusion per se does not cause persistent AKI. The evidence associating blood pressure levels and postoperative renal dysfunction is predominantly retrospective and observational, and therefore potentially misled by the complex interactions between exposures, confounders, and mediators. <b><i>Key Messages:</i></b> To better understand how perioperative hemodynamic management could affect the occurrence of kidney injury, it is pivotal to further investigate the association between hypotension and kidney dysfunction in the perioperative period and determine the degree to which hypotension is a causal factor.