National trends in patient safety for four common conditions, 2005-2011

Abstract

Background: Changes in adverse-event rates among Medicare patients with common medical conditions and conditions requiring surgery remain largely unknown.

Methods: We used Medicare Patient Safety Monitoring System data abstracted from medical records on 21 adverse events in patients hospitalized in the United States between 2005 and 2011 for acute myocardial infarction, congestive heart failure, pneumonia, or conditions requiring surgery. We estimated trends in the rate of occurrence of adverse events for which patients were at risk, the proportion of patients with one or more adverse events, and the number of adverse events per 1000 hospitalizations.

Results: The study included 61,523 patients hospitalized for acute myocardial infarction (19%), congestive heart failure (25%), pneumonia (30%), and conditions requiring surgery (27%). From 2005 through 2011, among patients with acute myocardial infarction, the rate of occurrence of adverse events declined from 5.0% to 3.7% (difference, 1.3 percentage points; 95% confidence interval [CI], 0.7 to 1.9), the proportion of patients with one or more adverse events declined from 26.0% to 19.4% (difference, 6.6 percentage points; 95% CI, 3.3 to 10.2), and the number of adverse events per 1000 hospitalizations declined from 401.9 to 262.2 (difference, 139.7; 95% CI, 90.6 to 189.0). Among patients with congestive heart failure, the rate of occurrence of adverse events declined from 3.7% to 2.7% (difference, 1.0 percentage points; 95% CI, 0.5 to 1.4), the proportion of patients with one or more adverse events declined from 17.5% to 14.2% (difference, 3.3 percentage points; 95% CI, 1.0 to 5.5), and the number of adverse events per 1000 hospitalizations declined from 235.2 to 166.9 (difference, 68.3; 95% CI, 39.9 to 96.7). Patients with pneumonia and those with conditions requiring surgery had no significant declines in adverse-event rates.

Conclusions: From 2005 through 2011, adverse-event rates declined substantially among patients hospitalized for acute myocardial infarction or congestive heart failure but not among those hospitalized for pneumonia or conditions requiring surgery. (Funded by the Agency for Healthcare Research and Quality and others.).

Figure 1. Adjusted Annual Changes in Adverse-Event Rates, Overall and According to Type of Adverse Event

Panel A shows changes in overall adverse-event rates according to the condition, and Panels B through E show changes in rates for each condition according to the type of adverse event. The changes in the rate of occurrence of adverse events and in the proportion of patients with one or more adverse events are expressed as adjusted relative risk ratios for the ordinal time variable, ranging from 0 to 5, corresponding to year 2005 to year 2011 (except 2008). The change in the number of adverse events per 1000 hospitalizations is expressed as an adjusted incidence risk ratio for the ordinal time variable. A relative risk ratio or incidence risk ratio of less than 1.0 indicates a decline in adverse events over time. The horizontal lines indicate 95% confidence intervals.

Figure 2. Association of Adverse Events with In-Hospital Mortality and Length of Stay, on the Basis of 2010–2011 Data

The association between adverse events and in-hospital mortality (Panel A) is expressed as an adjusted odds ratio for each of the three dummy variables: one adverse event, two or three events, and four or more events, as compared with no adverse events. An odds ratio greater than 1 indicates that a patient with this characteristic is more likely to die during a hospitalization than a patient without any adverse events. The horizontal lines indicate 95% confidence intervals. The association between adverse events and length of stay (Panel B) is shown in box-and-whisker plots. The vertical line inside each box represents the median value; the left and right boundaries of each box represent the 25th and 75th percentiles, respectively. The left and right vertical lines outside each box (“whiskers”) represent the values that are 1.5 times below the 25th percentile and above the 75th percentile, respectively. The circles represent outliers.