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* From the National Institute of Respiratory Diseases and National Institute of Public Health, Secretary of Health, Mexico, Tlalpan, Mexico.
Correspondence to: Rogelio Pérez-Padilla, MD, Instituto Nacional de Enfermedades Respiratorias, Calzada de Tlalpan, 4502 Col. Sección XVI México D.F., Mexico; e-mail: perezpad{at}servidor.unam.mx
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Abstract |
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Design: Retrospective review of medical records in a stratified sample of 836 patients drawn from a total of 4,555 hospital admissions registered during the year 2001.
Setting: A referral tertiary-care hospital for patients with respiratory diseases located in Mexico City.
Main outcome measures: Weighted prevalence of AEs and odds ratios for correlates.
Results: The overall weighted prevalence for AEs was 9.1% (95% confidence interval, 7.5 to 10.4%). Of these patients, 17% had a related transient disability, 52% had a prolonged hospital stay, and 26% had an AE that according to the reviewers contributed to their death. Of the total number of AEs, 74% were qualified as potentially preventable. Among all types of AEs, we identified as most relevant for a chest hospital the delayed surgical treatment of empyema, representing 11% of the total.
Conclusions: The frequency of AEs in a tertiary-care respiratory hospital is similar to that reported in general hospitals. A strategy to improve the treatment of empyema is needed.
Key Words: adverse events • developing country • empyema • respiratory diseases
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Introduction |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Our study aimed at the identification of the frequency, types, and correlates of AEs in a respiratory referral hospital. Camus et al9 recently reviewed iatrogenic respiratory diseases, but to the best of our knowledge no empiric data from respiratory hospitals have been reported from either developed or developing countries.
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Materials and Methods |
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During the year 2001, the study hospital admitted a total of 4,555 patients. Of this total, we drew a stratified sample following the criteria put forth by Brennan et al3 from the Harvard Medical Malpractice Study. Criteria were obtained mostly from the existing patient electronic database and also from the Institutional Committee for Prevention of Hospital Infections and from administrative records (legal suits, patient complaints, and discharges against medical advice). Hence, we reviewed all of the hospital admissions belonging to the following categories: lawsuits; complaints; in-hospital deaths (with necropsy); iatrogenic diagnosis according to International Classification of Diseases, Tenth Revision (ICD-10) codes T80 to T88 and J95.8; nosocomial infections (as determined by the Institutional Committee); and patients whose health status worsened during hospitalization. Then we took random samples from each one of the remaining categories, including in-hospital deaths without necropsy, hospital stay of > 30 days, transfer from the ward to the ICU or intermediate care unit, readmission to the hospital in < 15 days after discharge, hospital discharges against medical advice, transfer to another institution, re-entry to the operating room, and finally from all those patients who did not meet any of the previous conditions (Table 1 ). Following these criteria, we selected an initial sample of 922 subjects.
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Variable Definition
An AE was defined as the unintentional harm induced by medical or clinical care (and not by the primary disease) that may result in a prolonged hospitalization, some form of temporary or permanent disability, and/or death.3 To operationalize the variable and be able to decide on the presence of an AE, we used a categorical scale ranging from 0 to 6, in which 0 represented the absence and 6 represented the unquestionable presence of an AE. An AE was recognized whenever the reviewer’s score for this variable was 
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Data Analysis
An accepted taxonomy for the types of AEs is not available yet. For the purposes of this study, we used the following categories: deficient treatment (substandard therapy); complications of surgical or invasive procedures; hospital-acquired infections; delayed diagnosis or treatment; untoward drug-reactions; and accidental falls or trauma inside the hospital.
To estimate intraobserver agreement, each reviewer received, 2 months apart, five additional randomly chosen files from those he/she had previously evaluated. With the purpose of measuring interobserver agreement, each reviewer was blindly asked to process five randomly selected clinical files that had been previously evaluated by another reviewer, and these results were used to estimate 
coefficients. Intraobserver agreement was very good, as demonstrated by a = 0.89 for the presence of AEs (item 1), = 0.87 for the identification of substandard care as the origin of an AE (item 2), and = 0.81 on the subject of preventability of an AE (item 3). With regard to interobserver agreement, the corresponding values were = 0.67 for item 1, = 0.74 for item 2, and = 0.71 for item 3.
The overall prevalence of AEs was estimated by taking into account the sampling weight of each one of the risk strata for AEs and extrapolating to the total number of admissions during the year 2001. Contingency tables were drawn as necessary to assess the relationships of AEs with the remaining variables such as age, gender, hospitalization, socioeconomic level, final diagnosis, and exposure to surgical or invasive procedures. Logistic regression models were fitted to the data in order to identify factors significantly related to the occurrence of AEs. The database was analyzed using the survey commands statistical software (Stata v 8.0; StataCorp; College Station, TX) to take into account stratification and sampling weights.
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Results |
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Of the 836 records included in our final sample, 299 records were from patients in the risk criteria of death from necropsy, iatrogenic diseases according to the ICD-10, complaints, lawsuits, patient with worsening condition, and hospital-acquired infections; 237 files belonged to patients in the remaining risk categories for AEs; and 300 records were from patients who met none of the considered risk criteria for AEs (Table 1).
In the study sample, the average (± SD) age was 45.4 ± 23.3 years, the average length of stay was 16.6 ± 20.4 days, hospitalizations were usually due to a worsening clinical condition (only 1% were programmed admissions), and 376 records (44.9%) were from female patients. Most patients came from metropolitan Mexico City and surrounding states.
The overall weighted prevalence of AEs (with reference to the 4,555 patients admitted) in the year 2001 was 9.1% (95% confidence interval [CI], 7.5 to 10.7%), which in absolute numbers represents 415 cases (95% CI, 342 to 489 cases). The a priori stratification worked well, as 24% of the patients with any of the risk criteria (95% CI, 21 to 28%) resulted in an AE, compared to 1.6% (95% CI, 0.6 to 4.2%) in the patients with no risk identified. In fact, 174 AEs in the sample from a total of 178 were identified in the high-risk groups (98%), and only 4 AEs were identified in patients with no risk factors. Extrapolation to the total number of hospital admissions and taking into account the sampling weights resulted in 88% of the AEs identified in the high-risk strata (95% CI, 78 to 98%). All selection criteria were associated statistically with an increase risk of an AE in univariate models except by transfer to intermediate care, and to other hospital, hospital discharge against medical advice worsening condition, and readmission to the operating room.
Of those patients with an AE, 16.8% had disability lasting < 6 months, 5.2% had permanent disability, 52.2% had protracted hospital stay, and 25.8% died. Of the total group, 26.0% had more than one AE. In 66.5% of the AEs, health care was regarded as suboptimal; 74.4% were potentially preventable.
In univariate logistic regression models, patients with ear, nose, and throat diseases (odds ratio [OR], 0.2; 95% CI, 0.09 to 0.4) and those with AIDS (OR, 0.2; 95% CI, 0.05 to 0.7) had a lower risk for AEs compared to the remaining hospital admissions. On the contrary, patients with pleural diseases had an increased risk for an AE (OR, 4.0; 95% CI, 2.1 to 7.8); as well as those in the ICUs, most of whom were receiving mechanical ventilation (OR, 4.4; 95% CI, 2.0 to 9.5); those undergoing thoracic surgery or invasive procedures (OR, 2.7; 95% CI, 1.7 to 4.4); and especially those with empyema (OR, 5.6; 95% CI, 2.6 to 12). Other disorders evaluated, such as pulmonary tuberculosis, asthma, COPD, interstitial lung diseases, cancer, and pneumonias, showed no significant associations with the development of in-hospital adverse events. Similarly, in univariate models, gender, age, performing a bronchoscopy, and socioeconomic status were not associated with AEs.
Weighted logistic regression models were fitted to the data with the purpose of identifying the most important factors associated with AEs. All of the variables associated with AEs in the univariate analysis as well as age, gender, hospital stay, socioeconomic status, and residence of the patient (metropolitan area vs other states) were initially included in the multivariate model. The final model showed that all selection criteria were associated with the development of AEs (Table 1) and also were strongly related to a protracted hospital stay (ie, for every day of hospitalization, the risk of an AE increased by 4.0% [OR, 1.04; 95% CI, 1.03 to 1.06]). Another strong variable was hospital admission due to pleural disorders or empyema, which almost tripled the risk for an AE (OR, 2.95; 95% CI, 1.4 to 6.4; for empyema, OR, 2.9; 95% CI, 1.3 to 6.6). The risk for an AE was reduced in patients with AIDS HIV (OR, 0.2; 95% CI, 0.04 to 0.6) despite higher in-hospital mortality, and increased in patients residing in the Federal District or in the surrounding state of Mexico compared to those residing in other states (OR, 5.2; 95% CI, 2.9 to 9.3). Socioeconomic status, previous smoking, month of hospital admission, bronchoscopy, thoracic invasive procedure, gender, and age were unrelated to AEs events. In a similar model but excluding the length of hospital stay (because prolongation of the stay is one of the indicators of AEs), we obtained the same significant predictors; in addition, the performance of thoracic surgery or an invasive thoracic procedure increased the risk (OR, 2.2; 95% CI, 1.2 to 4.1). Only one ward had a significantly higher number of AEs (OR, 1.9; 95% CI, 1.1 to 3.5) compared to the remaining eight wards, adjusted by the rest of variables.
Table 2 depicts the types of the most common AEs; of note is the common delayed surgical treatment of empyema (11% of the total of AEs) in addition to well-known sources of AEs such as complications of invasive procedures, nosocomial infections, drug reactions, or delayed diagnosis or treatment. Table 2 also describes in more detail the grouping of AEs.
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Discussion |
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Our findings are consistent with those reported in studies from general hospitals from developed countries. Steel et al5 reported AEs in 36% of the patients admitted to university hospitals; in 25% of these cases, the events were life-threatening. Brennan et al3 observed AEs in 3.7% of hospitalizations, and 27.6% were caused by negligence; of these, 70% induced a transient disability of < 6 months and 2% caused a permanent disability. An additional study6 performed in Colorado and Utah revealed similar results, and the 3% prevalence of AEs mainly affected patients undergoing surgery or childbirth. A study5 performed in two British hospitals reported that 10.8% of patients experienced AEs. Andrews et al8 reported that AEs affected 480 of 1,047 patients (45.8%), with 17.7% of severe episodes causing disability or even death. Finally, the publication with the greatest public impact to date is the book1 by the US Institute of Medicine, which estimated that medical errors kill some 98,000 Americans each year.
Our study had several limitations. First, there is the issue of information bias, since the study was based on the retrospective review of medical records and is, therefore, limited to the availability and the quality of the information that the physicians and allied personnel actually put in the file. There are reasons to conceal information, including fear of lawsuits.111213 Hence, we believe that these results should be regarded as lower estimates of the real magnitude of AEs in hospitals of Mexico and similar countries. Furthermore, we and Brennan et al3 explored only severe AEs: those causing prolonged hospitalization, impairment, or death. Therefore, the number of less severe AEs, although unknown with precision, must be higher than that presented.
Second, AEs were evaluated according to the judgment of specialized physicians and are therefore subject to variation, primarily when difficult decisions must be made. However, concordance of opinions was acceptable, and only the events that reached or exceeded a value of 4 on a scale of 6 were considered iatrogenic events, that is, when the physician was almost certain about the issue at hand. Intrasubject concordance was assessed at an average of 2 months, and although it is likely that at least some cases could seem familiar during the second evaluation, the exact score that was assigned during the first evaluation is unlikely to be remembered. We could not review approximately 10% of the sampled charts in both the group with lower risk for AEs and the group with higher risk, although more from the lower-risk group. This could reduce slightly our estimates of AEs, but not by much.
The present study was performed exclusively in a tertiary-care institution located in Mexico City and does not otherwise reflect the practice of other public and private institutions of the country. However, it offers a first insight of what may be happening in respiratory hospitals and also elsewhere in Mexico and the developing world. It also makes clear that the problem of AEs is at least as important as in developed countries. Moreover, we sustain that the impact of AEs is even more meaningful for developing countries, since the availability of resources for health care is far more limited in these countries than elsewhere.
One of the most salient findings of this study was delayed surgical treatment for empyema. As less invasive surgical techniques have been developed, such as video-assisted surgery, the treatment of empyema has become more interventionist. Current therapy is based in pleural drainage by means of a chest tube, and a surgical procedure is usually reserved for those patients who have evidence of loculations that limit complete drainage.1415 However, a delayed surgical drainage may often extend hospitalization and its costs. In this regard, the reviewers agreed in considering these delays as iatrogenic errors, although only a few of those patients experienced severe medical complications or died.
Another important group of AEs in our study was the occurrence of hospital-acquired infections, predominantly pneumonia. This infection is frequent among severely ill patients, especially when a ventilator is used. These events may only be partially prevented, since the main predisposing factor is the own patient’s condition and the abatement of defense mechanisms as a result of intubation or insertion of IV or urinary catheters. The death rate due to hospital-acquired infections is high, particularly when caused by Pseudomonas aeruginosa, which is commonly seen in the study hospital. Reducing hospital infections requires the collaboration of all health personnel, the coordination of a multidisciplinary hospital infection committee, and permanent support of the hospital authorities.
As in other studies, complications due to surgical and other invasive procedures were also observed, including some caused by the insertion of a central venous catheter, such as pneumothorax. A potentially corrective measure is to strengthen supervision, focusing primarily on less experienced physicians and students, and to establish working teams with progressive specialization, such as vascular-care teams. In our study, prolonged hospitalization was associated with AEs. Length of hospitalization can be considered a consequence of AEs, especially as defined by Brennan et al3 and in our study. However, if we assume a fixed rate of AEs as a function of hospitalization time, a longer stay means also a higher cumulative probability of AEs for a given subject and hospitalization. In fact, the risk per day of some AEs could increase with hospitalization time for example the psychiatric reactions to hospital.
In the same way as epidemiologic surveillance teams for hospital-acquired infections are available at most hospitals, staff is needed for continuous supervision of other adverse events of hospitalization. This staff could come from the team already devoted to hospital-acquired infections.
The results of this study represent a major audit to the outcomes of hospital treatment in our institution, based on existing databases and medical records, and therefore a strategy with a wide availability even in developing countries. The selected strata with high risk for AEs concentrated 88% of them, which can be used with advantage in screening surveys. We contemplate follow-ups and in-depth analysis of the main problems found in the first evaluation to propose prevention strategies, beginning with empyema. Prevention of AEs requires identifying priorities and then using the so-called "systems approach,"16 which attributes AEs to the whole hospital lacking enough safety features and work of teams, and therefore the "system" and not individuals become the subject of interventions. Hospital management has a key role in this strategies. Cost-effective retrospective hospital audits for AEs can be organized by a chart review of a sample of the admitted patients stratified by a priori risk defined through administrative records, routine in hospitals. However, retrospective reviews should be supplemented by analysis of ongoing events and near misses, all leading to focused interventions.
Example 1
A man 42 years of age was hospitalized due to empyema that was drained with a chest tube. The tube was removed 6 days later because it was draining very little. A chest CT scan after the chest tube was removed showed pleural loculations. The patient was discharged as "improved." Twelve days later, he was readmitted with pleuritic chest pain and breathlessness. Pleural decortication was performed, and the patient recovered with no further complications.
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Acknowledgements |
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Footnotes |
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Received for publication February 14, 2005. Accepted for publication June 9, 2005.
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References |
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