POISSY, FRANCE—Although neuromuscular dysfunction acquired in the intensive care unit (ICU) has been well documented, data on the risk factors and incidence of ICU-acquired paresis (ICUAP) have been lacking. Recently, however, a prospective study by Bernard De Jonghe, MD, Reanimation Medicale, Centre Hospitalier de Poissy, France, and colleagues has shown that the duration of mechanical ventilation, the number of days with dysfunction of two or more organs, and the use of corticosteroids were independent risk factors for developing ICUAP.[1]

This is the first study to focus on the recovery period and to look at patients after they had regained consciousness. That patients could comprehend their condition and surroundings allowed researchers to perform clinical assessments and simple bedside tests rather than rely solely on electrophysiologic and histologic examinations for a diagnosis of paresis.

CONSCIOUSNESS AND STRENGTH

Between March 1999 and June 2000, investigators enrolled patients who were ventilated for at least seven days. Patients were excluded if they had preexisting neuromuscular dysfunction or another condition that would make assessment of paresis impossible. Out of the 332 patients who were ventilated for seven days or longer, 95 met the inclusion criteria and were eligible for evaluation.

Patients were assessed as soon as they were conscious, which was considered to be day 1. Determination of awakening was based on a patient’s response to five orders such as “Open your eyes” and “Nod your head.” The patient had to respond to at least three orders on two consecutive evaluations.

After consciousness was validated, investigators evaluated the strength of three muscle groups in each of the upper and lower limbs; each muscle group was given a score ranging from 0 (paralysis) to 5 (normal strength). Total scores thus ranged from 0 to 60; a patient whose score was lower than 48 on day 7 was considered to have ICUAP. In addition, all patients underwent electrophysiologic examination within 72 hours after day 7.

PATIENT DATA AND PARESIS

Of the 95 patients, 24 (25.3%) had ICUAP. In all but two of these patients, electrophysiologic results were clear enough to reveal sensorimotor axonopathy. After initial awakening, paresis lasted an average of 44.6 days, and the median duration was 21 days.

Thirteen patients had continued ICUAP at day 14; 10 of these patients underwent muscle biopsy. Neurogenic muscle atrophy and type 2 fiber atrophy were present in all 10 patients; muscle fiber necrosis was found in five patients. After performing regression analysis, investigators found four independent risk factors for ICUAP:
• Female sex.
• Dysfunction in two or more organs before awakening.
• Ventilation before awakening.
• Corticosteroid use before awakening.

Not only did the ICUAP patients remain on the ventilator longer before awakening than did controls (mean, 16.6 vs 10.8 days), but they also were ventilated for more days after awakening than were the controls (mean, 18.2 vs 7.6 days).

THERAPEUTIC IMPLICATIONS

The investigators were surprised to find female sex to be a risk factor for ICUAP, but they speculated that women’s lower physiological muscle strength may contribute to this finding. In addition, because the number of days with organ dysfunction was significantly higher in patients with ICUAP than in controls (mean, 10.3 vs 4.8 days), it appears that the duration rather than severity of organ dysfunction is a factor. De Jonghe et al suggest that interventions to reduce the risk of multiple organ dysfunction may also reduce the risk of ICUAP.

The association between prolonged duration of mechanical ventilation and ICUAP is probably due to the deleterious effects of immobilization on muscle function. Thus, preserving muscle activity through means such as passive physiotherapy may help prevent ICUAP in some patients.

While corticosteroid use has been associated with neuromuscular dysfunction in ICU patients who were given high doses for severe acute asthma, this is the first study to show such an effect in a general ICU population. According to the investigators, exogenous corticosteroids stimulate corticosteroid muscle receptors and may thereby produce myopathy. They therefore advise that physicians limit corticosteroid use to septic shock, unresolved adult respiratory distress syndrome, and status asthmaticus.

On a positive note, most of the patients in this study improved during the first several weeks or months after regaining consciousness. Neuromuscular dysfunction resolved within three weeks for half of the patients. At nine-month follow-up, 15 of the 16 survivors no longer had paresis, and 12 could return home.

—Lisa Pallatroni

Reference
1. De Jonghe B, Sharshar T, Lefaucheur JP, et al. Paresis acquired in the intensive care unit: a prospective multicenter study. JAMA. 2002;288:2859-2867.

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