Adverse events in surgical patients in Australia

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International Journal for Quality in Health Care 2002; Volume 14, Number 4: pp. 269–276

Adverse events in surgical patients in Australia A. K. KABLE1, R. W. GIBBERD1,2 AND A. D. SPIGELMAN3,4 1

Centre for Clinical Epidemiology and Biostatistics and 3Discipline of Surgical Science, School of Medical Practice, Faculty of Health, University of Newcastle, 2Health Services Research Group, 4Clinical Governance Unit, Hunter Area Health Service, Newcastle, New South Wales, Australia

Abstract Objective. To determine the adverse event (AE) rate for surgical patients in Australia. Design. A two-stage retrospective medical record review was conducted to determine the occurrence of AEs in hospital admissions. Medical records were screened for 18 criteria and positive records were reviewed by two medical officers using a structured questionnaire. Setting. Admissions in 1992 to 28 randomly selected hospitals in Australia. Study participants. Five hundred and twenty eligible admissions were randomly selected from in-patient databases in each hospital. A total of 14 179 medical records were reviewed, with 8747 medical and 5432 surgical admissions. Main outcome measures. Measures included the rate of AEs in surgical and medical admissions, the proportion resulting in permanent disability and death, the proportion determined to be highly preventable, and the identification of risk factors associated with AEs. Results. The AE rate for surgical admissions was 21.9%. Disability that was resolved within 12 months occurred in 83%, 13% had permanent disability, and 4% resulted in death. Reviewers found that 48% of AEs were highly preventable. The risk of an AE depended on the procedure and increased with age and length of stay. Conclusion. The high AE rate for surgical procedures supports the need for monitoring and intervention strategies. The 18 screening criteria provide a tool to identify admissions with a greater risk of a surgical AE. Risk factors for an AE were age and procedure, and these should be assessed prior to surgery. Prophylactic interventions for infection and deep vein thrombosis could reduce the occurrence of AEs in hospitals. Keywords: adverse events, disability, injury, prevention, quality in health care, surgery

The prevalence of adverse events (AEs) in acute care hospitals is high and AE prevention is now a priority research area for improving the efficiency and effectiveness of health care [1]. Australia is one of three countries that have published national estimates of the magnitude and variety of AEs in acute care hospitals. The Harvard Medical Practice Study (HMPS) [2] gave an estimate of 3.7% for the incidence of AEs in New York using a random sample of 30 121 admissions in 1984; another US study, UTCO [3], made estimates for the incidence of AEs of 2.9% from 14 700 random admissions in 1992 for Colorado and Utah hospitals. The recently completed New Zealand study reported an AE rate of 12.9% after reviewing 6579 records in 13 hospitals [4] (see http:// ). A pilot study in the UK obtained a rate of 6.7% from 480 medical records [5]. The Quality

in Australian Health Care Study (QAHCS) [6] reviewed a random sample of 14 179 admissions to public and private hospitals in 1992, and reported that 16.6% of admissions are associated with an AE, and that 50.3% of AEs are associated with surgery. The differences in reported rates, especially between the US studies with the low rates and the other two studies with higher rates, has generated discussion about the methodology of retrospective medical record review. A comparison of the results from UTCO and the QAHCS has recently been published [7,8]. Although the four studies used a two-stage process, with explicit criteria for the first stage and a similar definition for an AE for the medical review, the New Zealand and Australian studies were concerned with patient safety and quality of care, while the US studies had a greater interest

Address reprint requests to A. Spigelman, Discipline of Surgical Science, University of Newcastle, c/o John Hunter Hospital, Locked Bag 1, Hunter Region Mail Centre, Newcastle, NSW 2310, Australia. E-mail: [email protected]

 2002 International Society for Quality in Health Care and Oxford University Press


A. K. Kable et al.

in negligence. As a consequence of this difference in focus, the studies differ in three areas. The first stage review classified twice as many records as criteria-positive in QAHCS and New Zealand, which could be explained partially by the fact that the US studies limited the criteria for unplanned readmissions to 6 months for ages >65 years. The HMPS and UTCO reported incidence rates, whereas ‘prevalence’, the proportion of admissions associated with an AE, was reported in QAHCS and New Zealand. The cutoff point for medical causation for the AE was set at two in QAHCS and New Zealand, but at four in the US studies. Adjusting for these factors still results in a comparison of UTCO and QAHCS of 3.2% and 10.6% [7]. Runciman et al. [8] suggest that this is due to differences in reporting AEs with minor disability. One of the areas reporting a difference is post-operative problems, i.e. wound infection and bleeding. The higher rate reported in QAHCS may make this study more relevant for the analyses in this paper. The recent publication by the Institute of Medicine (IOM) on medical error [9] used the results from the HMPS and, by implication, the findings from the other studies, to highlight the magnitude of medical error. In particular, the IOM reported that 44 000–98 000 persons die each year in the US as a result of medical error. This has resulted in McDonald et al. [10] and Hayward and Hofer [11] questioning the validity of the results from HMPS and UTCO. A similar response was made to the publication of the QAHCS results, in which it was estimated that 18 000 deaths were associated with AEs in Australia in 1992. The key aspect when reporting the disability resulting from an AE in these retrospective record review studies is that no attempt has been made to determine what the outcomes may have been if no error had occurred. To do this would require estimating the probability of death given that the error was not made. This is a difficult exercise, and Hayward and Hofer [11] have attempted this on 111 randomly selected deaths in hospital. For retrospective record review studies, we prefer to report that the deaths were associated with an AE, rather than that the deaths were caused by the AE. Thus, 18 000 deaths would not be prevented if all errors were removed. This is supported by Brennan [12] in his discussion of post-operative haemorrhage, where transfer of a patient back to the operating room occurred even though there was no identifiable error made by the surgeon. This distinction has relevance to this paper, where we report the disability resulting from AEs in surgical patients, including wound infections. A wound infection may be prevented by prophylactic antibiotics, but not always. Thus, a wound infection will be classified as a complication caused by medical care if prophylactic antibiotics were not used. However, the appropriate use of antibiotics (removing the ‘error’) does not necessarily mean that the infection would not have occurred. That is, we can report the number of wound infections that occurred, but we cannot infer that no infections would have occurred if the patients had received prophylactic antibiotics. In our study, disabilities resulting from surgical procedures that are associated with an AE suggest that some aspect of medical care was not provided,


or in some cases was provided unnecessarily. From a quality in health care point of view, using record reviews to document the failure of key processes (appropriate provision of care) is more important than trying to estimate the potential gains in the outcomes, which can, in principle, only be done using randomized trials. Leape [13] addresses the question of overestimation of error rates by recognizing that medical records often do not contain sufficient information to allow identification of all errors, and retrospective studies are likely to underestimate AEs/complications [14], and that prospective observational studies often report higher AE rates [15]. Leape also recognized that hindsight bias may influence the reviewer’s perspectives on deaths due to AEs, but goes on to explain that 86% were AEs that constituted a ‘major factor leading to the patient’s death’. He emphasizes that these errors are the result of ‘defects in the design and conditions of medical work’. We report the magnitude of AEs for patients undergoing surgery, a class of patients including many who would be having an elective procedure rather than a non-elective admission for an acute episode of illness.

Materials and methods Objective The purpose of this study was to determine the AE rate for surgical patients, associated disability and preventability, and the major risk factors for an AE. Design Definitions of AEs vary and the QAHCS used the following definition (which was also used in the three other studies mentioned above): an AE is ‘an unintended injury or complication which results in disability, death or prolongation of hospital stay, and is caused by health care management rather than the patient’s disease’ [6]. Details of the study methods have been reported previously [6]. A two-stage review process determined the occurrence of an AE associated with the index admission. The index admission was the admission sampled. In stage 1, the medical records were screened by trained registered nurses using 18 explicit criteria, and if one or more criteria was positive, the record was independently reviewed by two medical officers using a structured questionnaire that included questions on unintended injury or complication, disability, and causation. These three questions were used to determine the occurrence of an AE (stage 2). If there was disagreement between reviewers, the process was repeated jointly and presented to a third reviewer, and consensus obtained [6]. The reviewers were 21 medical officers who were specialists with a minimum of 10 years’ experience, and many were senior specialists. They included physicians (nine), anaesthetists (five), obstetricians (four), surgeons (two), and one paediatrician.

Adverse events in Australia

Setting Twenty-eight hospitals were randomly selected from two states in Australia, in which admissions during 1992 were selected for review. Study participants Five hundred and twenty admissions were randomly selected by computer from in-patient databases in each hospital. Day-only admissions and patients in psychiatric wards were excluded. A total of 14 179 admissions were successfully reviewed, of which 8747 were medical and 5432 were surgical admissions. Outcome measures The proportion of admissions positive for each screening criterion was calculated. The prevalence of AEs was defined as the proportion of admissions associated with an AE. Temporary disability was defined as resolved within 12 months, and permanent disability was defined as not resolved within 12 months. Preventability of an AE was defined as ‘an error in management due to failure to follow accepted practice at an individual or system level’; accepted practice was taken to be ‘the current level of expected performance for the average practitioner or system that manages the condition in question’ [6]. Three categories were used: not preventable, low preventability (some evidence for preventability but
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