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TORONTO – Even if they are cured of the critical illness that sent them to the ICU, discharged patients are at risk of another potentially debilitating condition: ICU-acquired weakness.
That’s according to a report in the American Journal of Respiratory and Critical Care Medicine, which emphasizes that ICU patients can lose muscle mass and function for many reasons, including prolonged immobilization, mechanical ventilation, or even the critical illness that put them there.
The study, led by Canadian researchers from St. Michael’s Hospital in Toronto, points out that the mechanisms of muscle atrophy and function during an ICU stay have been well-studied but relatively little is known about the cellular and molecular mechanisms responsible for recovering muscle strength over the long term.
The article notes that some patients continued to suffer from weakness six months after they were discharged from the ICU, demonstrating persistent muscle wasting even after the biologic functions that commonly cause muscles to atrophy — such as inflammation or the breakdown of proteins in muscle tissue — have returned to normal.
In fact, lead author Jane Batt, MD, PhD, warned that, in some cases, muscle weakness which causes profound disability and reduced quality of life can last the rest of the patients’ lives.
"We know ICU patients lose muscle mass and function. Critical illness literally causes their muscles to dissolve," Batt said in a statement. “Some people grow it back and some don't. Some people can regrow the muscle, but it doesn't function properly."
The novel finding of the study, she said, was that sustained muscle atrophy in the long term is the result of impaired regrowth and is associated with a decrease in the number of satellite cells, the precursors to muscle cells.
"While satellite cells are not required for existing muscle fibres to grow in size, they are essential for the regeneration of injured muscle," Batt explained, adding that decreased number of satellite cells also contribute to age-related muscle loss.
For the small study, 27 patients who had been mechanically ventilated for a week or longer consented to being serially assessed over six months after ICU discharge, although 15 and 11 ended up being assessed at 7 days and 6 months after ICU discharge, respectively. It is the first phase of a larger research program to evaluate patient and caregiver outcomes after prolonged mechanical ventilation with a goal of developing a family-centered rehabilitation program after severe critical illness.