In the United States from 2002 through 2007, we found hospitalizations for persons with a secondary diagnosis of schizophrenia had increased odds of decubitus ulcer, infection due to medical care, postoperative respiratory failure, sepsis, and pulmonary embolism/deep venous thrombosis when compared to the general population. Accidental puncture was significantly reduced for hospitalizations with a secondary diagnosis of schizophrenia. Adjusting for hospital characteristics had little influence on these odds ratios.
Little is known about optimal perioperative management of medications in patients with schizophrenia. However, over-dosing, under-dosing, and interactions between analgesics, anesthetics and patients’ regular psychotropic medications may lead to postoperative delirium, confusion or oversedation which could cause aspiration and other respiratory complications following surgery [14
]. The odds of postoperative respiratory failure were almost twice as high in hospitalizations for persons with schizophrenia compared to those without schizophrenia, the most elevated for all of the measured patient safety indicators.
Postoperative delirium and other behavioral issues not uncommonly result in sedation and restraints for patients with schizophrenia [5
]. By reducing mobility, sedation or the use of restraints may increase the risk of decubitus ulcers, venous thromboembolism, nosocomial infection, and post-operative respiratory failure in persons with schizophrenia. In addition, behavioral aspects of the psychiatric disorder [16
], reduced pain sensitivity [17
], and effects of sedation may reduce the recognition of these complications following surgery.
We also found that the adjusted odds of accidental puncture or laceration were significantly decreased when comparing hospitalizations with a secondary diagnosis of schizophrenia to those without. This may be explained by the potentially lower rate of risky surgical procedures for persons with schizophrenia. The denominator for this complication includes all types of surgical discharges so that it does not control for the seriousness of the procedure or the number of procedures during hospitalization. A previous study found that individuals with mental illnesses were substantially less likely to obtain revascularization procedures following a myocardial infarction than persons without SMI [18
A previous study determined the odds ratios of various adverse events associated with a secondary diagnosis of schizophrenia in Maryland hospitals for 2001 to 2002 [19
]. Infections due to medical care, postoperative respiratory failure, sepsis, and venous thromboembolism all had increased odds in hospitalizations with schizophrenia, however the magnitude was higher for nosocomial infections and thromboembolism compared to the results of this study. Unlike the current study, the Maryland study did not find increased odds for decubitus ulcers. These differences may be due to geographic differences, a smaller sample, differences in the variables available in the Maryland hospital data, or the earlier version of the PSI software available at that time.
The relationship between schizophrenia and patient safety indicators may be subject to geographical variations because of differences in the way persons with schizophrenia receive care in different parts of the country. For example, a study conducted by Betempts et al.
found that hospital geographic location was significantly associated with differences in use of seclusion and restraint, citing different standards of practice or laws between states [20
]. In addition, the authors found the group most often secluded or restrained were persons with schizophrenia. Sample size limitations did not permit us to examine the interaction between schizophrenia diagnosis and state on the occurrence of adverse events.
4.1. Methodological strengths and limitations
The AHRQ Patient Safety Indicators provide a screen for a variety of potential adverse events during hospitalizations. Many previous investigations of medical injuries rely on medical record abstraction. These studies can provide information on clinical variables during hospitalization and a better understanding of the preventability of a patient safety event. However, creating standard and accepted definitions for preventability in patient safety is challenging. Chart abstraction studies require medical expertise to perform and are costly [21
]. As a result, most of these studies are limited to relatively small sample of patients and cannot provide a cost-effective way of screening for adverse events for special populations, nor could they address the scope of the problem on a national scale. This analysis uses data stratified and weighted to the general U.S. population of patients attending community hospitals that are already collected for management and billing purposes. The large size of the dataset makes it suitable to study small subgroups such as persons with schizophrenia that may be more vulnerable to adverse events.
Residual confounding is a common limitation to using large administrative databases. For example, since persons with schizophrenia tend to be poorer and have only public insurance, they may be more likely to be admitted to lower quality hospitals. Although adjusting for hospital characteristics thought to be associated with hospital quality did not result in large changes to the ORs, we cannot rule out the role hospital quality plays in the elevated rates of some of the PSIs.
Residual confounding from undetected or unreported medical disease in hospitalizations for patients with schizophrenia could also explain part of the associations we found between schizophrenia and the PSIs. Persons with schizophrenia also have a higher rate of lifestyle risk factors (e.g. obesity and smoking) which may not be fully captured by the variables available in the data [4
]. These lifestyle factors may increase a patient’s susceptibility to experiencing an adverse event. For example, the extremely high rates of smoking in people with SMI are likely to play a role in respiratory function, infection, and hypercoagulability, making persons with schizophrenia at greater risk of adverse events from respiratory failure, nosocomial infection, and deep vein thrombosis, respectively.
Accuracy of clinical coding on hospital discharge summary and medical billing records affects every variable in our analysis, from the main exposure of schizophrenia to patients’ comorbidities, demographic characteristics, and the PSIs. Previous studies have found that administrative database tools have had low sensitivity, but high specificity for adverse events, thus injuries are often underreported [22
]. However, we do not believe coding should be systematically different for hospitalizations for persons with schizophrenia compared to the general population.
The AHRQ Patient Safety Indicators are not definitive measures of adverse events, yet they emphasize areas of concern for quality of care that warrant further study. This analysis suggests that persons with schizophrenia may be more vulnerable to some types of medical injuries that can occur during hospitalization, and these differences often persist after controlling for known patient, hospitalization, and hospital characteristics. Higher rates of adverse events for hospitalizations in persons with schizophrenia raise questions about effective communication among healthcare providers and between health care providers and this vulnerable patient population. Improved understanding of factors related to hospital quality of care and outcomes in this group will be important to plan interventions to enhance patient safety for persons with schizophrenia.