OUTCOMES AFTER ACUTE CARE: ANALYSIS OF 133 MECHANICALLY VENTILATED PATIENTS

	To the Editor:

Your publication of Carson and colleague's (1) cautionary conclusions regarding the disposition to long term acute care (LTAC) hospitals of 133 patients suffering prolonged mechanical ventilation (PMV) in the ICU, may have done a disservice to all such patients. How so? Uncritical reviewers of the paper will apply its findings to all LTAC outcomes; the American Thoracic Society (ATS) has already proved this point by doing exactly that when highlighting the article in press releases on its web site and its ATS News publication (2).

The problems start with outdated information sources on frequency of PMV. Two current references (3, 4), encompassing ~ 6,000 ICU patient each, state that 15-20% of ICU mechanically ventilated patients are undergoing PMV, not 3-6%. The authors state that "little is known about the role of LTAC hospitals in achieving survival or return of function in patients who suffer from prolonged critical illness." This is a carefully worded statement, and is followed by a paragraph which begins: "We therefore examined the outcomes. . . ." The reader is given the impression that outcomes of PMV patients at LTACs are largely unknown.

There are more than 30 studies on post-ICU weaning from PMV in the English language literature. If we take only those with more than 100 patients, wherein prolonged mechanical ventilation is defined as  21 days, there are eight studies, half at LTACs (including ours), and the others in hospital noninvasive ICUs, or "step-down units" that specialize in weaning patients from PMV. These papers, taken together, report a 51% weaning success rate in more than 2,400 patients (5). Since only two of these studies report one-year survival, and none functionality, Carson and associates should still garner applause for their greater than 87% follow-up success in gathering outcome and functionality dataalbeit with a non-validated instrument, formulated by their hospital staff.

Then there is the problem of selection factors, which is given great weight by the authors. They explain the "poor short and long-term outcomes" of their patients at discharge and one year later by stressing that many LTACs specializing in weaning patients from PMV admit less critically ill patients than they do, using some screening for "prognosis, rehabilitation, and illness severity." They cite our report of outcomes in 1,123 patients, in which we stress that patients came to us more ill and closer to their catastrophic illness each year (6). Compared to their small series, our patients had slightly lower A-a gradients and APACHE scores, and slightly longer ICU time ventilator-dependent than did their patients. They report dopamine infusion running on arrival in 14%, while we did not accept patients with pressors running; in fact, in California, a statewide agency discourages the inappropriate transfer of such medically unstable patients (7).

Patient selection differences and differences in care, particularly in availability and continuity of physician care, on which the authors elaborated in a prior publication (8), probably combined to produce their dismal outcomes. What may be at work as well is the insidious intrusion of fiscal expediency into the decision-making process, with patients transferred out of the ICU too sick and too soon. Selection factors such as those above should be used to achieve the best outcomes for PMV patients after their ICU stay.

Finally, Carson and coworkers speculate that multicenter studies may validate their findings, allowing ICU caregivers to downscale expectations of PMV patients and their families to chronic mechanical ventilation or "comfort" care. Existing studies are in conflict with their findings. We concur with the authors' awareness, demonstrated in their penultimate paragraph, that drawing sweeping conclusions from studying a small number of patients and even smaller subgroups, is often unwise. Small numbers should dictate small conclusions, particularly if sweeping conclusions may imperil chances for best treatment and best outcome in a sizable cohort of patients.

Barlow Respiratory Hospital and Research CenterLos Angeles, California

1. Carson, S. S., P. B. Bach, L. Brzozowski, and A. Leff. 1999. Outcomes after acute care: analysis of 133 mechanically ventilated patients. Am. J. Respir. Crit. Care Med. 159: 1568-1573 [Abstract/Free Full Text].

2. ATS News. June 1999. Journal highlights. 25.3.

3. Seneff, M. G., J. E. Zimmerman, W. A. Knaus, and et al. 1996. Predicting the duration of mechanical ventilation: the importance of disease and patient characteristics. Chest 110: 469-479 [Abstract/Free Full Text].

4. Kurek, C. J., I. L. Cohen, J. Lambrinos, et al . 1997. Clinical and economic outcome of patients undergoing tracheostomy for prolonged mechanical ventilation in New York State during 1993: analysis of 6,353 cases under diagnostic related group 483.  Crit. Care Med. 25: 983-988 [Medline].

5. Scheinhorn, D. J., and M. A. Steam-Hassenpflug. 1998. Provision of long term mechanical ventilation. In S. Tharratt, editor. Critical Care Clinics. W. B. Saunders, Philadelphia. 819-832.

6. Scheinhorn, D. J., D. C. Chao, M. A. Stearn-Hassenpflug, L. D. LaBree, and D. J. Heltsley. 1997. Post-ICU mechanical ventilation: treatment of 1,123 patients at a regional weaning center. Chest 111: 1654-1659 [Abstract/Free Full Text].

7. California Medical Review Institute (CMRI).

8. Bach, P. B., S. S. Carson, and A. Leff. 1998. Outcomes and resource utilization for patients with prolonged critical illness managed by university-based or community-based subspecialists. Am. J. Respir. Crit. Care Med. 158: 1410-1415 [Abstract/Free Full Text].

	From the Authors:

We thank Dr. Scheinhorn for his comments and concerns, especially considering his experience in this area of clinical medicine. The primary focus of our study (1) was long-term outcomes of patients requiring prolonged mechanical ventilation. Owing to its relatively nonrestrictive admission policies, this particular LTAC provided a useful setting to study these patients in a way that limited selection bias. In fact, the outcomes for these patients were similar to those for patients requiring prolonged mechanical ventilation who were managed exclusively in acute hospital ICUs (2). Direct comparisons of our results with studies from different LTAC hospitals are not valid due to differences in patient selection. In response to Dr. Scheinhorn's comparison and critique, we cite our previous study (3) indicating that physician practice had a significant impact on success and time to liberation from mechanical ventilation but not on long term survival. Except in the most extreme circumstances, patient characteristics likely have the most influence on long term outcomes in these complicated patients.

Focusing on patient characteristics, our analysis used the factors of advanced age and poor prior functional status to identify a high risk group of patients with only 5% one-year survival. We will reiterate our previous statement that larger studies, involving multiple institutions, should examine these concepts further. If the results of our study are supported, this type of information could be useful for chronically critically ill patients or their surrogates as they consider appropriate levels of aggressive care versus alternative measures that focus on comfort. These patients should receive only the highest quality of appropriate care regardless of setting. The critical reviewer should realize that we do not suggest otherwise.

SHANNON CARSON

PETER BACH

ALAN LEFF

The University of Chicago

Chicago, Illinois

1. Carson, S. S., P. B. Bach, L. Brzozowski, and A. Leff. 1999. Outcomes after long-term acute care: an analysis of 133 mechanically ventilated patients. Am. J. Respir. Crit. Care Med. 159: 1568-1573 .

2. Spicher, J. E., and D. P. White. 1987. Outcome and function following prolonged mechanical ventilation. Arch. Intern. Med. 147: 421-425 [Abstract/Free Full Text].

3. Bach, P. B., S. S. Carson, and A. Leff. 1998. Outcomes and resource utilization for patients with prolonged critical illness managed by university-based or community-based subspecialists. Am. J. Respir. Crit. Care 158: 1410-1415 .