Changes in hospital mortality for United States intensive care unit admissions from 1988 to 2012

Abstract

Introduction: A decrease in disease-specific mortality over the last twenty years has been reported for patients admitted to United States (US) hospitals, but data for intensive care patients are lacking. The aim of this study was to describe changes in hospital mortality and case-mix using clinical data for patients admitted to multiple US ICUs over the last 24 years.

Methods: We carried out a retrospective time series analysis of hospital mortality using clinical data collected from 1988 to 2012. We also examined the impact of ICU admission diagnosis and other clinical characteristics on mortality over time. The potential impact of hospital discharge destination on mortality was also assessed using data from 2001 to 2012.

Results: For 482,601 ICU admissions there was a 35% relative decrease in mortality from 1988 to 2012 despite an increase in age and severity of illness. This decrease varied greatly by diagnosis. Mortality fell by >60% for patients with chronic obstructive pulmonary disease, seizures and surgery for aortic dissection and subarachnoid hemorrhage. Mortality fell by 51% to 59% for six diagnoses, 41% to 50% for seven diagnoses, and 10% to 40% for seven diagnoses. The decrease in mortality from 2001 to 2012 was accompanied by an increase in discharge to post-acute care facilities and a decrease in discharge to home.

Conclusions: Hospital mortality for patients admitted to US ICUs has decreased significantly over the past two decades despite an increase in the severity of illness. Decreases in mortality were diagnosis specific and appear attributable to improvements in the quality of care, but changes in discharge destination and other confounders may also be responsible.

Figure 1

Hospital mortality, age, and acute physiology score (APS) for 482,601 ICU admissions from 1988-1989 to 2010-2012.

Figure 2

Diagnostic groups with a >60% reduction in mortality from 1988-1989 to 2010-2012. Definition of abbreviations: COPD, chronic obstructive pulmonary disease; SAORTDIS, surgery for aortic dissection; SEIZ, seizures; SSAH, surgery for subarachnoid hemorrhage.

Figure 3

Diagnostic groups with a 51% to 59% reduction in mortality from 1988-1989 to 2010-2012. Definition of abbreviations: AMI, acute myocardial infarction; ; CHF, congestive heart failure; SEPSIS, sepsis, non-urinary tract; SGICA, surgery for gastrointestinal malignancy; SICH, surgery for intracerebral hemorrhage; uriSEPSIS, sepsis, urinary tract.

Figure 4

Diagnostic groups with a 41% to 50% reduction in mortality from 1988-1989 to 2010-2012. Definition of abbreviations: BACVPNEU, viral pneumonia; GIBLEED, gastrointestinal bleeding (upper); GIBLVAR, gastrointestinal bleeding, varices; ICHMED, intracerebral hemorrhage; SHEADTR, surgery for multiple trauma, including the head; STROKE, stroke/cerebral vascular accident.

Figure 5

Diagnostic groups with a 10% to 40% reduction in mortality from 1988-1989 to 2010-2012. Definition of abbreviations: ARDS, acute respiratory distress syndrome; CARDARR, cardiac arrest; HEADTR, head trauma, with chest, abdomen, pelvis, or spine injury; SGIBLEE, surgery for gastrointestinal bleeding; SGIOBS, surgery for gastrointestinal obstruction.

Figure 6

Hospital mortality and discharge destination for 422,294 ICU admissions from 2001 to 2012. Other hospital includes another acute care hospital or long term acute care facility.