Predictors of mortality of mechanically ventilated patients in internal medicine wards

Abstract

Purpose

Budget restrictions have led to shortage of intensive care unit (ICU) beds in several countries. Consequently, ventilated patients are often kept on the wards. This study examined survival likelihood among patients ventilated on the wards and the predictive value of commonly used severity-of-illness scores.

Methods

This study is a prospective observation and characterization of consecutive, mechanically ventilated patients in 3 internal medicine wards of a single hospital who were denied ICU admission. Outcome measures are as follows: 28-day mortality, survival to hospital discharge, and 3 months postdischarge.

Results

Eighty-six patients were examined. The patients were 78.9 ± 8.9 years old; 53% were independent preadmission. Respiratory insufficiency due to infection was the main reason for mechanical ventilation (58%). Charlson and acute physiology scores (APS) averaged 4 ± 2.2 and 91.8 ± 26.7, respectively. Twenty-eight-day mortality was 71%, whereas in-hospital mortality was 74% and 3 months postdischarge mortality was 79%. Survivors were significantly younger than nonsurvivors (74.4 ± 8.5 years vs 80.4 ± 8.6 years, P < .01), were more likely to be ventilated for cardiac causes (41% vs 11%, P = .04), and had significantly higher initial mean blood pressure (79.4 mm Hg vs 58.2 mm Hg, P = .02) and blood albumin levels (29.8 g/L vs 25.7 g/L, P = .05). Death rate was 10 times more likely, with an APS greater than 90 on the day of intubation as compared with an APS less than 90.

Conclusion

Mortality in patients ventilated on the ward was high, especially in the subgroup of patients with an APS score greater than 90. The early calculation of APS may assist in focusing therapeutic efforts on patients with better survival chances.

Introduction

Changes in health care financing designed to curb medical expenditure are becoming increasingly prevalent. This and other factors have led to a relative lack of intensive care unit (ICU) beds in several European countries [1] and an evolving crisis in the US critical care services [2], [3], [4]. Like in many other countries, Israel has been suffering from a shortage of ICU beds for the last decade. Ward physicians in departments of internal medicine and geriatric medicine in most of the hospitals ventilate patients requiring intubation and ventilation as medically/acutely indicated, independent of whether the patient is admitted to an ICU or not. This leads to a situation where ventilated patients are often kept on the ward because the number of ventilated patients exceeds by far the number of available ICU beds [5]. In Israel, it is estimated that most ventilated patients are kept on the ward in departments of internal medicine and geriatric medicine [6], [7]. This situation, in varying rates, is prevalent in most of the hospitals in Israel, thus transferring ventilated patients to another hospital's ICU is not feasible in most cases.

Mostly as of lack of place and/or being deemed to less likely benefit from intensive care (usually because of severity of disease and very high predicted mortality) than others, it is often the patients who are perceived to be the most severely ill that are not admitted to ICU. This situation is particularly relevant to nonsurgical elderly patients with multiple chronic illnesses [5]. Decisions whether to refer an intubated ward patient to ICU are not anchored upon clear criteria [7], [8], [9], [10]; no models for prediction of survival have been developed for critically ill ventilated patients who remain on the ward, and prediction models that exist for ICU patients require validation in this population before clinical implementation.

The current study describes the course and outcome of mechanically ventilated patients in medical wards, which is, in a main part, predicated on scarcity of resources. It was not our intention to compare the course and outcome of mechanically ventilated patients in medical wards with the course and outcome in ICU because this was previously done [6], [7]. Rather, we aimed to explore some parameters that will prospectively identify those patients ventilated on the ward who have a better chance than others to survive. The value of the severity of acute illness (using the acute physiology score [APS], part of the Acute Physiology and Chronic Health Evaluation [APACHE] III) [11], the burden of chronic illness (using the Charlson Index) [12], [13], and the functional status (using the Lawton scale for activities of daily living [ADLs]) [14], [15] for predicting survival were used for this purpose. By doing so, we aimed to provide to the internal medicine physicians a practical key that will assist them to focus their efforts on patients with a better prognosis. The aim of any severity of illness scoring (beyond research purposes) is to help the treating physician to construct a more realistic prognostication. Because it was obvious that our study population will consist mainly of elderly patients with poor prognosis, in the face of our limited resources and difficulty to provide them on the wards (monitoring, blood sampling, vasopressors, imaging, intrahospital transport, surgical interventions, dialysis, cardiopulmonary resuscitation, etc), any piece of information about prognosis will help in therapeutic decisions and in resource allocation.

We preferred this score over the traditional complete APACHE II score because we were looking for a “new,” not ICU-related score. We wanted this score to reflect more widely our study population's acute physiological changes and also the multiple comorbidities and functional limitations that this aged population most probably will have. The APS component of the APACHE III contains a larger number of acute physiological parameters than the APACHE II (20 vs 12) and is not affected by the patient being postoperative elective/emergency (which is not relevant to our study population, but affects APACHE II), and the Charlson Index contains more chronic illnesses than the APACHE II (19 detailed conditions vs 5 general ones). The index of ADL is a well-recognized reflector of biological and psychosocial function translated into survival rate [14], [15].