Survival After Long-Term Residence in an Intensive Care Unit

The concept of hospital dependence is applicable to the majority of the ICU survivors, though the authors did not attempt to create a quantitative measure of this status.³⁶ Another study limitation is that absence of hospitalization does not equal functional independence. A better definition of this status, and its application to a broad spectrum of LOS, would be a valuable adjunct to ICU decision making.

The convention by which the authors considered the first day of their study period a “fresh slate” did not adjust for the situation that some first admissions actually were readmissions. Assuming the validity of the finding that readmitted patients had a higher burden of morbidity and mortality, misclassification of admission status would tend to inflate the mortality of single-admission patients and minimize the magnitude of the differences found in this study. Similarly, an admission near the end of the study period may have been analyzed as a single admission, even if the patient was readmitted and died the next year. The latter situation also would tend to inflate the mortality of the single-admission category. None of these possible mathematical errors negates the fact that a second ICU admission should be regarded as a marker for poor recovery.

A more accurate estimate of short- and long-term prognosis likely can be obtained by examining laboratory studies and interventions such as vasopressors, dialysis, and ventilation at defined time points. Although the authors did not attempt it, development of such a model would be a valuable undertaking. They focused on describing the expected course of ICU patients and determining what patterns emerged from care duration. As this study found that the prognosis for long-term ICU residents remained guarded a long time after discharge, survival models of patients with 1- to 2-week ICU residences likely would be valuable in clinical decision making.

A quality-of-life survey was administered only to patients in the ICU longer than 2 weeks. This limited study was conducted to explore the feasibility of assessing outcomes other than survival and to determine the staffing requirements needed to research this further. A more meaningful analysis would come from a broader analysis of scores from 3 or 4 different ICU lengths of stay.

Clinician and family behavior can influence some of the outcomes measured in this study—particularly in cases in which an illness is poorly characterized and an evidence basis for decision making is lacking. In these situations, values and individual clinician judgment likely predominate, possibly introducing variability to care duration. Nevertheless, cumulative mortality 1 month or more after ICU residence would eliminate biased clinician behavior. The heterogeneity of care providers’ and families’ decision making, captured in this analysis, likely is a normal phenomenon that should help inform physicians’ understanding of prolonged ICU residence.