Canadian HealthCare Mall: The Effect of Body Mass Index on Patient Outcomes in a Medical ICU


DiabetesAs more and more Americans combine an increase in food consumption with a decrease in physical activity, it is not surprising that there is a growing trend toward overweight and obesity in the United States. The prevalence of obesity has increased from 14.5 to 22.5% in the past 10 to 15 years. In 1998, 97 million American adults, representing 55% of the population, were designated as being overweight or obese. With the obese population in the United States continuing to rise, it becomes evident that obesity and obesity-related disorders will be encountered more frequently in the health-care industry.

On the basis of guidelines released by the National Institutes of Health, a person with a body mass index (BMI) of 25 to 29.9 is defined as overweight, whereas obesity is defined as having a BMI of >30Л In addition to psychological and social difficulties faced by people who are categorized as obese, they are more susceptible to physiologic complications and having decreased length of life.

Many studies concur that as BMI increases, so does the risk of mortality. The overall mortality is approximately twice as high in the severely obese and may be 2 to 25 times higher than normal in disease-specific mortality. In addition, obesity increases the risk of cardiovascular disease, noninsulin-dependent diabetes mellitus, hypertension, respiratory dysfunction, and certain types of cancer. Obese patients undergo more frequent hospitalizations because obesity exacerbates the onset and progression of illnesses. Although many hospitalized patients pass through the ICU at some time during their stay, it is expected that the number of obese patients requiring intensive care will also increase substantially. There are several studies that do not concur that BMI correlates with mortality; however, this is normally a result of smaller populations. In larger populations, the significant association is shown. This study examines the effect of BMI on the outcome of patients in a medical ICU (MICU).

 BMI in critical illnessUntil very recently, no data have been published on the influence of BMI on outcomes after critical care. Surprisingly, Tremblay and Bandi found that there was no increased mortality in a study of a national cooperative database. Their study did not have information on complication rates. Therefore, our investigation complements their multicenter study by providing additional analyses on outcomes and specific information on complication rates. Tremblay and Bandi did find low discharge functional status. We did not have that data at the time of this study, but we are planning to obtain that data and to examine functional discharge status in a future investigation. Do you have an irresistible desite to lose weight? To know how you may here on wordpress together with Canadian Health and Care Mall.

Published trials evaluating the influence of BMI in critical illness have demonstrated varying effects of BMI on outcomes. We hypothesized that there would be a relationship between the degree of obesity, as determined by BMI, and the mortality and rate of complication in the ICU.

Materials and Methods

This study was conducted in a 9-bed MICU of a 650-bed tertiary care hospital. Patients > 20 years old who were admitted to the unit between January 1, 1997, and August 1, 2001, and had MICU stays > 24 h were enrolled in the study. The age limit of 20 years was used because most growth in stature is complete, and any increase in weight is generally attributable to excess adipose tissue. If any patient was admitted more than once during a single hospital admission or during the study period, only data from the first encounter were used for comparisons.

ventilator-associated pneumoniaWhenever possible, height and weight were measured and recorded, and BMI was calculated on admission for the MICU registry. According to these data, the patients were then separated into five groups based on BMI, as follows: underweight (BMI < 20.0), normal weight (20.0 to 24.9), overweight (25.0 to 29.9), obese (30 to 39.9), and severely obese (> 40.0). These groupings were based on BMI categories devised by the World Health Organization and the National Heart, Lung, and Blood Institute of the National Institutes of Health to classify overweight and obesity.

As part of a formalized critical care database in our institution, data were concurrently collected for each patient, including the following: age, gender, APACHE (acute physiology and chronic health evaluation) II diagnosis, length of stay (LOS) in the MICU and hospital, and the number of days the patient required mechanical ventilation. It was also documented when a patient had certain complications while in the MICU. These complications included central or arterial line infection with bacteremia, pneumothorax, deep venous thrombosis, nosocomial or ventilator-associated pneumonia (VAP), failed extubation, self extuba-tion, GI hemorrhage, or prolonged paralysis from neuromuscular blockade (NMB) [Table 1]. Patient deaths that occurred in the MICU or the hospital were recorded. Finally, total hospital costs and variable costs were separately extracted from the administrative database of the hospital for each patient. Total cost comprises both fixed and variable costs incurred while furnishing services to patients. Fixed cost is the combination of fixed direct (administration salaries and supervisory salaries, office supplies depreciation expenses) and fixed indirect (also known as overhead or supporting cost or costs of the finance, information services, and telecommunication department expenses, etc). Variable cost is cost that only occurred when a procedure is performed, for example, labor (registered nurse, license practical nurse, and medical assistant wages) or variable supplies costs (medical supplies, drugs, radiographs, etc).

Using analysis of variance for continuous variables and x2 for discrete variables, BMI groups were compared by age, APACHE

II diagnosis, MICU LOS, hospital LOS, mortality in the MICU and hospital, standardized mortality rate (SMR) for MICU and hospital, ventilator-days, and hospital costs. Logistic regression was performed to examine BMI and mortality. Overall complication rates were compared using analysis of variance.

Table 1—Definitions for MICU Complications

Complications Definition
Central or arterial line infections Documented line tip infection with bacterial growth > 15 colonies, and positive blood culture findings with the same organism and not associated with an infection at another site.
Nosocomial pneumonia Clinical examination findings of a pulmonary process or chest radiograph showing new or progressive infiltrate, consolidation, cavitation, or pleural effusion plus one of the following: new-onset purulent sputum, organism isolated from blood culture, or isolation of pathogen by sputum culture or bronchial specimen.
VAP Mechanical ventilation and met the above criteria for pneumonia, and have suggestive sputum culture per Gram stain, new or progressive infiltrates, and physician diagnosis of pneumonia.
Failed extubation Requirement of reintubation within 24 h of liberation from a mechanical ventilator.
Self extubation Patient removing an endotracheal tube.
GI hemorrhage A 2-g decrease in hemoglobin over a 24-h period with evidence of melena, hematochezia, or hemetemesis with or without cardiovascular symptoms.
Prolonged paralysis from NMB Persistent paralysis based on physical examination lasting > 48 h after cessation of paralytic agent.
Deep vein thrombosis Ultrasonographic evidence of acute blood clot in a major vein of the leg or arm.
Pneumothorax Radiographic evidence of air within the pleural space either associated with a central line placement or secondary to barotrauma.