Influence of the Admission Pattern on the Outcome of Patients Admitted to a Respiratory Intensive Care Unit: Does a Step-Down Admission Differ From a Step-Up One?

Discussion

In this study we have demonstrated for the first time that the patient's location prior to RICU admission profoundly influences outcomes, since the step-down subjects and those admitted from the emergency department had a better survival rate than the step-up subjects who had transited through a medical ward or respiratory ward. These latter subjects were also, on average, more severely ill than those transferred from an ICU or the emergency department, most likely because their conditions worsened while being outside of a “protected” environment.

In Europe, a RICU located inside an acute care hospital should admit patients suffering from acute or acute-on-chronic respiratory failure not immediately needing endotracheal intubation but requiring close monitoring, patients with single organ failure needing invasive ventilation, patients requiring NIV, and patients to be weaned from invasive mechanical ventilation.¹ In North America most of the intermediate care units accept a variety of patients, not just patients in respiratory failure,^12,13 so the results of this study may not be generalized, but may basically reflect a different international attitude.

These different conditions reflect different flows of patients once admitted to a general hospital. For example, in a survey conducted in 26 RICUs in Italy, Confalonieri et al¹⁴ found that almost half the patients (47%) were admitted from emergency departments, 19% from other medical wards, 18% from ICUs, 13% from specialist respiratory wards, and 2% following surgery. This is perfectly in keeping with the data collected in our 7-bed RICU in a general hospital for about 1,400 patients and serving a population of 800,000 inhabitants.

Despite the fact that several investigations have assessed the outcomes of patients admitted to RICUs,^12–14 none has considered the effect of the admission pattern, which may serve to deliver step-down or step-up care or to admit directly from the emergency department.¹⁵ The clinical outcome of patients requiring ICU admission (the step-down pattern) has been described in the recent literature, especially for the subset of patients requiring prolonged mechanical ventilation and transferred to a RICU located inside a rehabilitation center or long-term acute care hospital, which is increasingly utilized after a critical illness, especially in North America.^16,17 Data collected on more than 3,000 patients admitted to 5 Italian RICUs, mainly dedicated to weaning from mechanical ventilation, showed a mortality rate of about 15%,¹⁸ which is in line with our results. Concerning a RICU located inside an acute care hospital, Bigatello et al¹⁹ suggested that a considerable number of patients were ready to come off mechanical ventilation at the time of RICU admission, implying that in the preceding ICU stay, discontinuing mechanical ventilation had not always been a priority, and explaining the quite low mortality rate even 1 year after hospital admission.

The data obtained in the present study (∼18% mortality) are in line with those from previous studies, and the deaths were homogenously distributed among patients from the 3 different ICUs of provenance. No differences were observed between the 2 main different locations prior to RICU admission. This is probably because the purpose of our RICU is to admit mainly “respiratory” patients, with single organ failure, so the characteristics of our transferred subjects were rather homogeneous. No subjects were admitted from the coronary care unit of our hospital, since this is organized in such a way that the staff take direct care of their patients, even when these need mechanical ventilation, or in the worst case they have a “preferential channel” with our post-transplant/ECMO ICU.

The mortality rate of the subjects from the emergency department was similar to that of the subjects from the ICUs. This may be explained by the these subjects' SAPS II, which was almost identical to that of the subjects from the ICUs, despite that the latter were mainly invasively ventilated, but in a phase of clinical stability. The subjects from the emergency department were “acutely” ill and undergoing an episode of acute respiratory failure. Interestingly, ∼50% of this group of subjects were ventilated noninvasively; one could, therefore, have expected a better hospital survival, especially if the subjects were treated within a protected environment. However, not all the subjects were affected by acute hypercapnic respiratory failure, in which NIV is associated with the best outcome; in fact, some of the subjects had “pure” hypoxic respiratory failure, such as ARDS, in which NIV is associated with a higher failure rate and mortality.²⁰ Indeed, some subjects, mostly those who were very elderly and with several comorbidities, had DNI orders, so NIV was a ceiling treatment with a palliative aim to improve dyspnea.²¹ In our study, NIV was a ceiling treatment in 41 (13%) of the total 326 subjects.

The most interesting finding of the present study is that the mortality rate in the step-up subjects (transferred to the RICU after having transited through a general or specific ward) was higher than in those admitted from other locations, with those coming from the respiratory ward having the higher risk of death.

The step-up subjects had higher SAPS II and were older, so it is not surprising that their mortality rate was also much higher than that of subjects with lower SAPS II transferred from an ICU or the emergency department. It may, therefore, be claimed that it is the severity of disease itself rather than the location that determines these patients' outcome.^22–24 Unfortunately, given the lack of a standardized database in all the units, we were unable to detect a progressive deterioration of clinical condition during the hospital stay. Simchen et al²⁵ demonstrated that about 2% of all patients admitted to the regular departments of an acute care hospital deteriorate during their hospital stay and reach the criteria of admission to a critical care environment. The majority of these patients (55%) were not, however, transferred early to the ICU or similar environment, so their mortality was likely to increase. Simchen et al concluded that prompt admission to a critical care environment in patients deteriorating while in hospital wards should be imperative to maximize survival, but that this occurred in only a small proportion of patients. This suggests that we should look carefully at patients admitted to wards with respiratory disease, in case we are mis-triaging some patients to lower levels of care than they truly need.

Another problem is the fact that intensivists (ie, those working in ICUs) are usually involved as “first-line call” for patients admitted to a medical ward, and that, due to the paucity of ICU beds, they often deny transfer for old patients or those with several comorbidities, since the physician's perception of poor prognosis is associated with less aggressive or invasive care. The paucity of beds is a limiting factor for access to a general ICU, at least in most European countries. The decision to admit a patient to this setting has been reported to be influenced by the physician's perception of prognosis, which has been shown to be overly pessimistic, with the risk of barring access to ICU to patients who may have a chance of surviving.²⁶ Other studies from different countries have confirmed the existence of this trend, indicating that intensivists are very selective in allowing transfer to the ICU.^27,28 Specialized ICUs such as RICUs may provide an alternative for the referral of patients who develop severe respiratory failure in a regular medical ward, but RICUs are generally present only in large hospitals, and, even when available, ward physicians tend to consult first with the general intensivists.

RICUs usually care for older, chronically ill patients, so it is likely that the higher mortality in patients admitted from the wards may simply reflect the fact that some of these patients had end-stage diseases. This is a striking finding in the patients transferred from our respiratory ward; in 31% of these subjects NIV was a ceiling treatment. However, subjects with DNI orders were separated in the analysis from other patients undergoing NIV treatment; they were also evenly distributed across patients from the various different pre-RICU locations: 27% were from the respiratory ward, 19% from medical wards, 32% from the emergency department, and 22% from ICUs, so their inclusion in the analysis does not alter the finding that pre-RICU location affects prognosis.

The present study confirms most of the previous findings of other investigators in the same setting, for example, that albumin level and age are predictors of hospital mortality. Malnutrition associated with advanced lung disease has been termed the “pulmonary cachexia syndrome”: it is associated with an accelerated decline in functional status and is recognized as an independent predictor of mortality in patients with lung diseases.²²

In the univariate analysis the use of NIV was associated with an increased risk of mortality, which was a surprising finding since NIV improves survival, compared to standard medical treatment, at least in patients with acute hypercapnic respiratory failure.²⁹ It should, however, be noted, as previously stated, that NIV was used in the RICU in some cases (in patients with DNI orders) as a palliative tool. Moreover, NIV was also used in patients with hypoxic respiratory failure, including those with pneumonia. Both these circumstances affect the perceived success of NIV in this study. Indeed, it is our policy to treat all patients with a COPD exacerbation with respiratory failure and a pH > 7.25 in the respiratory ward.³⁰

Only a small proportion of our patients were discharged to home from the RICU, in line with data reported by Bigatello et al,¹⁹ who reported that only 2% of their patients were discharged to home.

Interestingly, we also confirmed that RICU admission is associated with a quite high rate of weaning from mechanical ventilation, since the percentage of patients invasively ventilated at discharge decreased from 70% to 40%.

The present study has some biases. The first and probably most important is that the data were collected in a single RICU in an acute care hospital, and the results, therefore, may not be extrapolated to other hospitals and geographic locations. Second, almost all the patients had been admitted for medical problems, while only 3 were post-surgery patients, and they are therefore representative of only one part of the population admitted to a critical care environment. Lastly, as previously stated, it was often difficult to collect a complete clinical history (in particular, previous lung function data), especially from patients transferred from a medical ward, since these patients were often in critical condition on RICU admission.