Abstract & Commentary
Acute Respiratory Failure in Chronic Neuromuscular Diseases: ICU Management and Long-Term Outcomes
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: Most patients with chronic neuromuscular diseases who developed acute respiratory failure received noninvasive ventilation and many also required intubation, although the majority of them survived the hospitalization and most did not require long-term tracheostomy.
Source: Flandreau G, et al. Management and long-term outcome of patients with chronic neuromuscular diseases admitted to ICU for acute respiratory failure. A single-center retrospective study. Respir Care 2011 (epub 2/21/11 prior to print).
Flandreau and colleagues at the Hôpital de la Croix-Rousse in Lyon, France, report their experience with patients with chronic neuromuscular disease (CNMD) admitted to their 15-bed medical ICU because of acute respiratory failure (ARF). They reviewed the hospital records of all such patients first admitted because of ARF between 1996 and early 2007, and also followed up with all survivors as of mid-2008. Patients not admitted because of ARF were excluded, as were patients without a well-established diagnosis of CNMD and subsequent admissions for ARF. In addition to underlying CNMD diagnoses and patient demographics, the investigators recorded the cause of ARF and severity of illness by SAPS II score; how the patients were managed including the use of noninvasive ventilation (NIV), intubation, and tracheotomy; and short-term outcomes such as survival and ventilation status. In addition, all surviving patients were followed up either by interview or information from their primary physicians.
During the 12-year admission period, 4813 patients were admitted to the authors' MICU; 87 met all inclusion criteria. These patients were evaluated in two categories of CNMD: hereditary conditions (n = 44; Duchenne muscular dystrophy 19, other muscular dystrophies 17, spinal muscular atrophy 4, and miscellaneous 4) and acquired disorders (n = 43; amyotrophic lateral sclerosis 20, myasthenia gravis 6, spinal cord injury 6, multiple sclerosis 3, post-polio syndrome 2, and other, 6). Prior to the ICU admission, 48% of the patients in the first group were receiving NIV, vs 23% of the second group; pre-existing tracheostomy was present in 9% and 14% of the patients, respectively.
As expected, patients with hereditary CNMD were younger than those with acquired disorders. Apart from this, there were no differences in initial severity of illness, initial arterial blood gas values, or precipitating cause of ARF (including airway secretions in 28%, hypoventilation in 22%, pneumonia in 22%, and aspiration in 11%). Eleven patients died during the index ICU admission (12.6%), with no difference between the hereditary and acquired groups. Eighty-two percent of patients with hereditary CNMD were treated with NIV in the ICU, compared to 63% of those with acquired CNMD (P = 0.04), and the corresponding rates of intubation were 30% and 56%, respectively (P = 0.017). The rates of tracheotomy during the admission (9% vs 12%) did not differ statistically.
Surviving patients were followed up for a median of 3 years. During this interval the overall mortality rate was 57.5%, which did not differ by type of CNMD. At the final follow-up assessment, 46% of patients were receiving NIV and 29% had a tracheostomy.
Commentary
I believe this is the largest outcome study yet reported among patients with CNMD admitted to the ICU because of ARF. Chronic neuromuscular disease is an uncommon cause of ARF, even in the medical ICU of an acknowledged center of excellence in managing such patients, as in the present instance. The majority of the patients in this series were managed acutely with NIV, but the need for invasive ventilation was nonetheless common. The mortality rate was low, and long-term outcome was independent of whether the underlying CNMD was hereditary or acquired.
This report documents excellent, state-of-the-art management for patients with ARF complicating CNMD. This group of investigators is one of the most experienced anywhere, and first described long-term management of CNMD patients with NIV nearly 30 years ago. Their unit also has established expertise in the acute application of NIV, as well as a cadre of unit-dedicated physical therapists who routinely contribute the following to the care of these patients on a 24/7 basis:
- Clinical assessment, several times daily, of coughing and swallowing capabilities as well as the adequacy of secretion clearance;
- Respiratory muscle support using manual assistance, mechanical insufflation-exsufflation, and intermittent positive-pressure breathing;
- Selection of NIV interface, mode, and settings as well as training the nurses; and
- Active involvement in mobilizing patients, including getting them out of bed at the earliest possible opportunity.
ICUs in France do not have respiratory therapists who perform some of these activities, although emphasis on these aspects of care and the expertise with which they are applied vary a great deal in this country.
This was a retrospective study, focused on a selected group of patients. It excluded readmissions and patients with acute neuromuscular processes, such as Guillain-Barre syndrome and cervical spinal cord injury. The population of patients with CNMD managed in Europe also differs from that in the United States, with, for example, many fewer patients with traumatic quadriplegia from cervical spinal cord injury. Despite these potential limitations to the generalizability of the findings, the present report is valuable for its demonstration that ARF in CNMD can have a low ICU mortality despite the short-term need for intubation, that permanent tracheostomy is by no means inevitable, and that long-term survival after a bout of ARF is achievable for many patients.