corona virus-Covid19

Skeletal Muscle Changes in Critically Ill COVID Patients Interview with:
Dr Toon Mostien

Jessa Hospital, Hasselt, Belgium What is the background for this study

Response: Patients with COVID-19 that survive critical illness are confronted with months or even years of physical impairments. Moreover, literature indicates that possibly up to 68% can still suffer from musculoskeletal symptoms such as muscle pain and weakness after infection with SARS-CoV-2. Although we have focused on 7-day differences in muscle fiber type characteristics, this research is a first step in discovering if skeletal muscles of critically ill patients are more severely damaged compared to a more general ICU population. Cytokine storm and systemic inflammatory responses triggered by the infection could augment muscle damage beyond that of non-COVID ICU patients. What are the main findings?

Response: Surprisingly, we didn’t find significant atrophy of type I and II fibers, previous reports have reported almost 20% (or more) of muscle fiber atrophy within one week of ICU stay. However, a subgroup of our patients showed a pathological fiber size increase. This observed swelling has influenced our average muscle fiber size, because these patients showed an average increase of 62% and 32% in type I and II fiber size respectively. Does edema or fatty infiltration account for some of these changes?  Does this occur in other critically ill patients?

Response: In the subgroup of patients with a pathological size increase, we performed further analysis with electron microscopy. It showed hydropic degeneration, a phase of muscle damage that can ultimately result in muscle fiber necrosis. The hydropic degeneration could be caused by systemic inflammatory mediators and oxygen radicals. These could damage the muscle cells mitochondria, which could lead to energy depletion. Energy depletion can cause dysfunction of ion pumps regulating intracellular volume. Ion pump failure could ultimately lead to myocyte swelling/hydropic degeneration and ultimately results in necrosis in SARS-CoV-2 critically ill patients. Of course this is just one of the possible mechanisms leading up to myocyte swelling. The previously mentioned mechanism has also been described in a model of septic shock. In this study they showed intra-and extracellular muscle edema after just 48h of septic shock.

There are only a few studies that have focussed on changes in muscle fiber type characteristics over time in critically ill patients. Up till now these studies were almost solely performed on patients with acquired brain injury, most of these patients were physically fit before their ICU admission. These studies found significant muscle fiber atrophy over a one week period. Other populations (e.g. with viral infection, sepsis, ARDS) have never been studied to our knowledge. We simply don’t know if edema or fat infiltration account for these changes in other ICU populations. It would be interesting to perform future studies on for instance septic patients, to see if  they show similar patterns of muscle damage as patients infected with SARS-CoV-2. What recommendations do you have for future research as a result of this study?

Response: We think the most important step is to compare the results found in this study to a control group. This study focused on the effect of time (difference between day 0 and 7). This allows us to make a conclusion regarding the effects of 1 week ICU stay on muscle fiber type and ultrastructural muscle characteristics, however, this does not allow us to differentiate between patients infected with SARS-CoV-2, and critically ill patients without infection. To determine if being critically ill with SARS-CoV-2 leads to more muscle damage than only critical illness itself , a control group should be added to the study, because up till now we can only speculate on this.

Citation: presented at Euroanaesthesia

Pathological skeletal muscle features in critically ill patients infected with SARS-CoV-2: a prospective observational cohort study

European Journal of Anaesthesiology

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