Weakness: Polyneuromyopathy – the Role of Mobility
The issue of chronic critical illness or Post Intensive Care Unit Syndrome (PICS) is of great importance in the managment of patients in the ICU. There are many additional synonyms for the problem, and the number of names for syndrome demonstrates lack of critical understanding of the syndrome.
Why is this an important concern? Acute respiratory failure results in 1.1 million ICU admissions needing mechanical ventilation annually. There are 400,000 ICU deaths/yr with resp failure; hospital mortality: 37%. The cost of this care is substantial and rising; total health care costs total 17.6% of GDP in the US.
The key questions to be answered about early rehab care in the ICU are:
- How early can ICU rehabilitation occur without patient compromise?
- What exactly is movement content, by whom?
- How much, how often?
Morris points out fiscal considerations of ICU rehabilitation are a potential barrier and historically, the fear of early movement of ICU patients may also fuel reluctance to intervene.
Dr. Morris suggests the proper way to evaluate rehabilitation is the same way you would approach the use of a certain drug with a patient.
Previous studies focused only on heart and lungs but not on muscle performance. Dr. Morris suggests that we need more studies specifically of nerve/muscle therapy to understand the mechanisms of muscle atrophy in the ICU setting. Most studies come from athletes at rest, space program, animal models, post-total knee replacement patients, and the applicability to ICU patients is not clear.
Muscle not used for activity is broken down as an energy source. One goal of early physical therapy should be not allowing loss of muscle mass. Atrophy mechanisms involve several mechanisms, especially a ubiquitin-proteasome pathway leading to actin/myosin breakdown.
There are as yet no consensus statements about the precise type of active exercise that should be used and which muscles to target. Antigravity muscles of neck, trunk, hip are focused upon traditionally. Is focus on resistance or endurance better for rehab? Of particular imporance, the correlation between strength and muscle mass is not 1 to 1: strength increases before muscle mass increase can be demonstrated.
Muscle strength, measured by the amount of weight lifted, is not the only important parameter. Power, the speed of accomplishing muscular activity, is also key and helps define performance. Loss in power appears to be linked to probability of injury.
Early ICU rehab has been shown to be safe; definite efficacy under study. Increased rehab effort lowers number of ICU and hospital days; effects persist when other potentially confounding interventions are controlled for. Morris says it appears to cost no more, and there is a trend toward lower cost. Bedside cycling is one approach to early rehab treatment. Somewhat unexpectedly, early mobility predicts lower rehospitalization rate after one year.
Neuromuscular electrical stimulation: may reduce breakdown in patients too ill for participation in exercise. But the optimal approach: which muscles, how much current, and frequency is not yet clear.
Many unanswered questions remain: how can we best control breathlessness and pain with exercise? Which healthcare professionals are needed for intervention? Do patients with underlying problems like pneumonia benefit from customized versions of these rehab processes? How do we affecting change in culture in the ICU that traditionally has viewed early rehab as dangerous? In the process, we need to assess effect of muscle rehab on cognitive function. Will drugs blocking muscle breakdown be effective? What is the impact of electrical stimulation of neuromuscular system?