Earlier age of dementia onset and shorter survival times in dementia patients with diabetes.

Diabetes is a risk factor for dementia, but relatively little is known about the epidemiology of the association. A retrospective population study using Western Australian hospital inpatient, mental health outpatient, and death records was used to compare the age at index dementia record (proxy for onset age) and survival outcomes in dementia patients with and without preexisting diabetes (n = 25,006; diabetes, 17.3%). Inpatient records from 1970 determined diabetes history in this study population with incident dementia in years 1990-2005. Dementia onset and death occurred an average 2.2 years and 2.6 years earlier, respectively, in diabetic compared with nondiabetic patients. Age-specific mortality rates were increased in patients with diabetes. In an adjusted proportional hazard model, the death rate was increased with long-duration diabetes, particularly with early age onset dementia. In dementia diagnosed before age 65 years, those with a ≥15-year history of diabetes died almost twice as fast as those without diabetes (hazard ratio = 1.9, 95% confidence interval: 1.3, 2.9). These results suggest that, in patients with diabetes, dementia onset occurs on average 2 years early and survival outcomes are generally poorer. The effect of diabetes on onset, survival, and mortality is greatest when diabetes develops before middle age and after 15 years' diabetes duration. The impact of diabetes on dementia becomes progressively attenuated in older age groups.

Morbidity outcomes of 78,577 hysterectomies for benign reasons over 23 years.

OBJECTIVE: To investigate the association of the method of hysterectomy for benign reasons with morbidity outcomes in Western Australia after taking other demographic, social and health-related factors into account. DESIGN: Population-based retrospective observational study. SETTING: All hospitals in Western Australia where hysterectomies were performed from 1981 to 2003. POPULATION: All women aged 20 years or older who underwent a hysterectomy for benign reasons. METHOD: Logistic and zero-truncated negative binomial regression analysis of record-linked administrative health data. MAIN OUTCOME MEASURES: Relative odds of experiencing complications during the hysterectomy admission or readmission and relative length of stay in hospital by type of hysterectomy. RESULTS: There were 78,577 hysterectomies performed for benign reasons from 1981 to 2003. Procedure-related haemorrhage (2.4%) was the most commonly recorded complication, followed by genitourinary disorders (1.9%), infection (1.6%) and urinary tract infections (1.6%). Vaginal hysterectomy was associated with reduced odds of infection and haemorrhage compared with abdominal procedures during the hysterectomy admission. Readmission rates increased from 5.4% in 1981-84 to 7.2% in 2000-03 as average length of stay decreased by 53% over the same time period. Women who underwent laparoscopically assisted vaginal hysterectomies and vaginal hysterectomies had increased odds of readmission for haemorrhage and genitourinary disorders compared with abdominal hysterectomy. Young age, increasing number of co-morbid conditions and having a complication at hysterectomy admission were also associated with increased odds of readmission. CONCLUSION: These findings identify women at risk of readmission following hysterectomy and highlight an opportunity to modify early discharge and patient follow-up practices to reduce this risk.

Relationships between age, body weight, physical fitness and sex-hormone-binding globulin capacity.

The associations between sex-hormone-binding globulin capacity (SHBG), age, body mass index (BMI), and physical fitness have been studied in 34 men and 36 women. Multivariate analysis was used to look for independent associations with SHBG. The data indicate that when controlled for a number of other factors SHBG levels are related, in men but not in women, to age (positively, p less than 0.001) and BMI (negatively, p less than 0.001).

Long term relative survival after surgery for abdominal aortic aneurysm in western Australia: population based study.

OBJECTIVE: To determine the long term relative survival of all patients who had surgery for abdominal aortic aneurysm in Western Australia during 1985-94. DESIGN: Population based study. SETTING: Western Australia. SUBJECTS: All patients who had had surgery for abdominal aortic aneurysm in Western Australia during 1985-94. MAIN OUTCOME MEASURES: Morbidity and mortality data of patients admitted and surgically treated for abdominal aortic aneurysm in Western Australia during 1985-94. Elective, ruptured, and acute non-ruptured cases were analysed separately. Independent analyses for sex and patients aged 80 years or more were also undertaken. Postoperative (>30 days) relative survival was assessed against age and sex matched controls. RESULTS: Overall, 1475 (1257 men, 218 women) cases were identified. The crude five year survival after elective surgery, including deaths within 30 days of surgery, was 79% for both men and women. When compared with a matched population the five year relative survival after elective surgery was 94.9% (95% confidence interval 89.9% to 99.9%) for men but only 88.0% (76.3% to 99.7%) for women. The five year relative survival of those aged 80 years and over was good: 116.6% (89.1% to 144.0%) compared with 92.4% (87.7% to 97.0%) for those under 80 years of age (men and women combined). Cardiovascular disease caused 57.8% of the 341 deaths after 30 days. CONCLUSION: In a condition such as abdominal aortic aneurysm, which occurs in elderly patients, relative survival is more clinically meaningful than crude survival. The five year relative survival in cases of elective and ruptured abdominal aortic aneurysm was better in men than in women. This is probably because of greater comorbidity in women with abdominal aortic aneurysm and this deserves more attention in the future. The long term survival outcome in octogenarians supports surgery in selected cases.

Bowel cancer. Positive expectations for improvements in outcomes.

BACKGROUND: Colorectal cancer continues to be a major cause of mortality and morbidity in people over 50 years of age in the Western world. Age standardised incidence and mortality rates are high in Australia and too many patients with colorectal cancers are first diagnosed with advanced stage disease. OBJECTIVE: The aim of this overview of colorectal cancer is to present the clinical epidemiology of colorectal cancer in Australia, review screening strategies and demonstrate the benefits of early diagnosis. DISCUSSION: While little change has been noted in the cure rate within Australia during the past two decades, there are now promising signs that more colorectal cancers are being detected in the early stage due to greater community awareness of the disease. The movement to establish an effective screening program for colorectal cancer will further add to the ability to detect colorectal cancers at the early stages. These developments, coupled with improvements in surgical technique and adjuvant therapy, will provide real scope to improve treatment, survival and quality of life outcomes.

Effectiveness of a patient blood management data system in monitoring blood use in Western Australia.

The aim of this paper is to describe a linked patient blood management (PBM) data system and to demonstrate its usefulness by presenting the blood usage data obtained. Our existing datasets already collected much of the required information in relation to PBM. However, these datasets were not linked. A patient identifier was used to link the Patient Administration System with the Laboratory Information System. Data linkage was achieved by linking the Laboratory Information System with the Patient Administration System records where blood transfusion or laboratory result date/time fell between admission and discharge date/time. The two datasets were then consolidated into the PBM data system. Blood usage data obtained from the system showed that between August 2008 and July 2009 there were 59,627 patient completed separations in the pilot hospital. Of the total transfused units, 62% were red blood cells (RBC), followed by fresh frozen plasma (22%), cryoprecipitate (9%) and platelets (8%). Around 50% of RBC transfusions were administered to patients >70 years of age. General medicine represented 21% of RBC usage, followed by haematology (19%), orthopaedics (17%) and general surgery (16%). Patients with 100 g/l pre-transfusion haemoglobin received 9% of RBC transfusions and patients with 71-100 g/l pre-transfusion haemoglobin received 73% of RBC transfusions. The post-transfusion haemoglobin in RBC transfusions exceeded 100 g/l in 33% of patients. Databases were successfully linked to produce a powerful tool to monitor blood utilisation and transfusion practices within a pilot PBM program. This will facilitate effective targeting of PBM strategies and ongoing monitoring of their impact.

Persistent high rates of hysterectomy in Western Australia: a population-based study of 83 000 procedures over 23 years.

OBJECTIVE: To investigate incidence trends and demographic, social and health factors associated with the rate of hysterectomy and morbidity outcomes in Western Australia and compare these with international studies. DESIGN: Population-based retrospective cohort study. SETTING: All hospitals in Western Australia where hysterectomies were performed from 1981 to 2003. POPULATION: All women aged 20 years or older who underwent a hysterectomy. METHODS: Statistical analysis of record-linked administrative health data. MAIN OUTCOME MEASURES: Rates, rate ratios and odds ratios for incidence measures and length of stay in hospital and odds ratios for morbidity measures. RESULTS: The age-standardised rate of hysterectomy adjusted for the underlying prevalence of hysterectomy decreased 23% from 6.6 per 1000 woman-years (95% CI 6.4-6.9) in 1981 to 4.8 per 1000 woman-years (95% CI 4.6-4.9) in 2003. Lifetime risk of hysterectomy was estimated as 35%. In 2003, 40% of hysterectomies were abdominal. The rate of hysterectomy to treat menstrual disorders fell from 4 per 1000 woman-years in 1981 to 1 per 1000 woman-years in 1993 and has since stabilised. Low socio-economic status, having only public health insurance, nonindigenous status and living in rural or remote areas were associated with increased risk of having a hysterectomy for menstrual disorders. Indigenous women had higher rates of hysterectomy to treat gynaecological cancers compared with nonindigenous women, particularly in rural areas. The odds of a serious complication were 20% lower for vaginal hysterectomies compared with abdominal procedures. CONCLUSION: Western Australia has one of the highest hysterectomy rates in the world, although proportionally, significantly fewer abdominal hysterectomies are performed than in most countries.

Influence of gender on outcome from ruptured abdominal aortic aneurysm.

BACKGROUND: The aim of the present study was to compare outcomes following ruptured abdominal aortic aneurysm (AAA) in men and women. METHODS: Overall mortality from ruptured AAA was compared in men and women using the Western Australia Health Services Research Database. The linked chains of de-identified hospital morbidity and death records were selected using the ICD-9-CM (International Classification of Diseases - Clinical Modification) diagnostic and procedure codes pertaining to AAA. Cases were divided into three groups for analysis: patients who died without admission to hospital, those admitted to hospital with a ruptured AAA but who did not undergo operation, and patients who underwent operation for ruptured AAA. RESULTS: Ruptured AAA occurred in 648 men and 225 women over the age of 55 years during the decade 1985-1994. Only 50 per cent of women, compared with 59 per cent of men, were admitted to hospital. Of those admitted to hospital only 37 per cent of women underwent operation, compared with 63 per cent of men. The overall mortality rate from ruptured AAA was 90 per cent in women and 76 per cent in men (chi2 = 50.34, 1 d.f., P < 0.0001). Although women were, on average, 6 years older than men, this unfavourable pattern occurred across all age groups. CONCLUSION: Women with a ruptured AAA are more likely to die than men. More research is required to identify the causes of this sex difference.

Changing treatments for primary urolithiasis: impact on services and renal preservation in 16,679 patients in Western Australia.

OBJECTIVES: To examine changing treatments for the primary presentation of urinary lithiasis and their effects on re-admissions, repeat procedures, cumulative hospital use and renal preservation. PATIENTS AND METHODS: Linked hospital morbidity records were used to identify first-time admissions for renal and ureteric calculi from 1980 to 1997 in the population of Western Australia. The cases were followed to mid-1999 and actuarial methods used to estimate risks of further hospital admissions and procedures, including the loss of a renal moiety. RESULTS: Between 1980 and 1997 the total rate of inpatient procedures for urinary stones more than doubled, at a time when the rate of first-time hospital admissions increased by only 13% and the conservative management of stones remained constant at approximately 59%. The predominant procedure for stone management was initially open lithotomy, replaced in the early 1980s by percutaneous nephrolithotomy and soon supplemented by extracorporeal shock wave lithotripsy (ESWL). The changes in technology led to a four-fold increase in procedural re-admissions within 30 days of primary separation. This was a result of repeated, staged or postponed interventions, often involving the use of stents or a second treatment with ESWL. The risk of surgical intervention decreased from 48% to 32%, whilst the cumulative length of stay over the first year decreased from 7.8 to 3.9 days. The risk of kidney loss declined significantly from 2% to <0.1% during the period. CONCLUSIONS: The main reason for more interventions were short-term procedural re-admissions. ESWL reduced the need for invasive procedures and decreased cumulative hospital stay, despite more re-admissions. Renal preservation improved by a factor of 10.

The influence of gender on outcome following peripheral vascular surgery: a review.

There is considerable evidence that outcome following intervention for coronary artery disease in women may be worse than it is for men. The influence of gender on outcome following peripheral vascular surgery has received less attention and is the subject of this review. The incidence of most vascular procedures in women is 20-40% that of men. Women appear to have a greater risk of dying following surgery for abdominal aortic aneurysm, a higher risk of stroke and death following carotid endarterectomy, and poorer patency rates following infrainguinal bypass. The causes may include delayed diagnosis and referral, increased co-morbidity and possibly the effect of smaller arteries in women.

A population-based study of the incidence, mortality and outcomes in patients following surgery for colorectal cancer in Western Australia.

BACKGROUND: The literature contains many reports on the management of colorectal cancer from single institutions or groups of specialist surgeons. But there are few data on community-wide patterns of treatment or the outcomes of colorectal surgery. The aim of the present study was to use a population-based linked database to assess the trends in colorectal cancer incidence and mortality in Western Australia (WA) in the period 1982-95, and to evaluate the outcomes following surgical care. METHODS: A population-based linked database was used to relate the cancer registry, hospitalization and mortality records of all patients with a diagnosis of colorectal cancer in WA during 1982-95. Data on surgical treatment and postoperative morbidity and mortality in this group of patients were available only in 1988-95. Patient records were selected using the international classification for diagnosis and procedure codes pertaining to colorectal cancer and surgery. Incidence and mortality trends in colon and rectal cancers were estimated by Poisson regression regression of age-standardized rates, and relative survival analysis was used to compare patient survival with the general population. RESULTS: During the 14-year period, 9673 patients presented with a diagnosis of colorectal cancer. The sex distribution of patients with colon cancer was evenly divided, but rectal cancer was more common in men (ratio 1:4). The mean age at diagnosis was 67.8 years (SD: 12.7). During the study period there was a significant increase in the standardized incidence rate of rectal cancer in men, and in the mortality rates from colon cancer in women. The overall crude 5-year survival was 57%. Large bowel resections were performed on 71% of patients with an in-hospital postoperative mortality of 4.2%. CONCLUSION: Colorectal cancer is a continuing major cause of morbidity and mortality in WA. The present study demonstrated increases in the incidence rate of rectal cancer in men and in the mortality rate from colon cancer in women in the period 1982-95.

Long-term relative survival following surgery for abdominal aortic aneurysm: a review.

BACKGROUND: The literature reporting the long-term survival following surgery for abdominal aortic aneurysm (AAA) tends to be confusing. As a result, many clinicians looking after patients with AAA may be uncertain about the five-year survival of a given patient. This is in marked contrast to the situation for patients with malignant disease. With the current interest in population screening and endoluminal stenting for AAA, an understanding of long-term survival is increasingly important. METHODS: Thirty two publications in the English language over the last 20 years, containing data pertaining to five-year survival following routine elective surgery for AAA in unselected patients, were identified using Medline searches. RESULTS AND CONCLUSIONS: A range of important methodological differences were noted. The mean five-year crude survival was about 70% while the expected survival of a matched population was close to 80%. Survival was further reduced by about 10% in cases with significant coronary heart disease. Age alone is not a predictor of long-term relative survival with octogenarians who survive beyond 30 days surviving longer than an age-matched population.

Appendicectomy in Western Australia: profile and trends, 1981-1997.

OBJECTIVE: To measure and describe changes in the incidence of appendicectomy in the population of Western Australia (WA) for 1981-1997. DESIGN: Population-based incidence study using hospital discharge data. SETTING: All hospitals in WA (1981-1997). PATIENTS: All patients who underwent an appendicectomy in WA hospitals. MAIN OUTCOME MEASURES: Changes in the incidence of appendicectomy procedures over time; age-standardised rates and age-sex profiles of four appendicectomy subgroups: (1) acute emergency admission, (2) other emergency admission, (3) incidental appendicectomy and (4) other appendicectomy. RESULTS: From 1981 to 1997, there were 59,749 appendicectomies in WA hospitals. The age-standardised rate of appendicectomy declined by 63% in metropolitan females, by 44% in non-metropolitan females, by 41% in metropolitan males and by 21% in non-metropolitan males. The rate of decline was significantly greater in females and in metropolitan patients. From 1988 to 1997, acute emergency admission for appendicectomy was the most common admission status and was more common in males than females (122 v 103 per 100,000 person-years) and in non-metropolitan areas. The rate of incidental appendicectomy was higher among females than males (20 v 7 per 100,000 person-years). From 1988 to 1997, recorded diagnosis coding for appendicitis became more specific, with a marked reduction in the use of the "unspecified" appendicitis code. CONCLUSIONS: The overall incidence of appendicectomy has declined markedly in WA and includes a decline in the practice of incidental appendicectomy. The trend was greatest in the metropolitan hospitals.

Population-based study of carotid endarterectomy in Western Australia.

BACKGROUND: Previous studies reported an increase in the rates of operation following the publication of major trials that demonstrated the benefit of carotid endarterectomy in reducing stroke. The aim of this study was to determine whether carotid endarterectomy rates have continued to rise despite the reducing trend in most manifestations of atherosclerotic cardiovascular disease. METHODS: Record linkage was used to select patients who had a carotid endarterectomy during the interval from 1988 to 2001. Incidence rates were age-standardized and trends were examined with Poisson regression. RESULTS: The rate increased by 13.8 per cent per year between 1988 and 1998; however, from 1999 onwards the rate of carotid surgery fell by 15.8 per cent per year. In octogenarians, the rate increased steadily from 0.9 to 5.1 per 100,000 person-years between 1992 and 2000. The proportion of octogenarians also increased significantly from 0.9 per cent in 1988-1990 to 19.5 per cent in 2000-2001 (chi2=60.11, 4 d.f., P<0.001). CONCLUSION: For the first time a recent decline has been observed in the rate of carotid endarterectomy, most likely owing to a combination of the deceasing incidence of atherosclerosis and more widespread use of effective drugs in the treatment of cardiovascular disease. The rate and proportion of operations in patients aged 80 years or older has increased steadily.

Population-based outcomes after 28,246 in-hospital vasectomies and 1,902 vasovasostomies in Western Australia.

OBJECTIVES: To examine trends in vasectomy and vasovasostomy, and the surgical complications and factors associated with reversal after vasectomy, and paternity after vasovasostomy. PATIENTS AND METHODS: Procedure rates were estimated from 1980 to 1996 in the population of Western Australia. Linked hospital morbidity records were used in the follow-up of men after vasectomy to estimate the risks of complications and reversals. Records of vasovasostomies were linked to the paternity field on birth registrations. Independent effects of the study factors were examined using Cox regression. RESULTS: There was little net change in vasectomy rates, whereas vasovasostomy rates increased in men aged 30-49 years. Risks of surgical complications were low and decreased for vasovasostomy. At 12-15 years after vasectomy, the risk of reversal levelled at 2. 4% in the total cohort and at 11.1% in men aged 20-24 years. The risk of vasovasostomy was 69% greater after vasectomy performed in 1994-96 than in 1980-84 (P = 0.011). The factors strongly associated with reversal were age < 30 years and being single, divorced or separated at the time of vasectomy. Paternity was achieved after an estimated 53% of vasovasostomies. Successful reversal was more likely if the man was younger at vasectomy and the time elapsed was comparatively short. Compared with vasovasostomies performed in 1980-84, the success rate of those in 1994-96 was almost four times higher. CONCLUSION: Population rates of vasectomy are stable but the risk of seeking a reversal has increased. Outcomes after vasovasostomy have improved. Care should be taken during the counselling of men before vasectomy, and especially in those aged <30 years.

Fenestration in endovascular grafts for aortic aneurysm repair: new horizons for preserving blood flow in branch vessels.

PURPOSE: To describe techniques for deploying fenestrated stent-grafts that use partial graft deployment and guided tracking of the fenestration to the arterial orifice. TECHNIQUE: Fenestrations have been added to custom-made tube grafts and commercially manufactured Zenith stent-graft systems to preserve perfusion of aortic side branches. Partial device deployment, orientation markers on the endograft, and intraoperative angiography enable maneuvering of the fenestration over the orifice of the target vessel with the aid of guiding catheters. Placement of a Palmaz stent overlapping the fenestration and vessel orifice secures the junction. Two variations of fenestration have preserved blood flow in renal arteries during endovascular repair of abdominal aortic aneurysms (AAAs); similar techniques have maintained flow to the celiac axis in a thoracic aortic aneurysm. CONCLUSIONS: Accurate placement of a fenestration over the orifice of a target vessel is feasible, but long-term maintenance of position is dependent on secure graft fixation. This capability brings us a step closer to overcoming the problem of inadequate necks in infra-renal AAAs, especially when the neck is foreshortened by asymmetry of the renal origins. It may also pave the way for the eventual replacement of the entire aorta with an endoluminal graft.

Population-based record linkage study of the incidence of abdominal aortic aneurysm in Western Australia in 1985-1994.

BACKGROUND: The incidence of abdominal aortic aneurysm (AAA) has increased steadily during the past 30 years. METHODS: Trends in the incidence and surgical intervention for AAA in Western Australia were reviewed for the interval 1985-1994. A population-based health database was used to link morbidity and mortality records of all patients aged 55 years or more who died from rupture or were admitted and treated surgically for AAA. Three groups were separated for analysis: patients with a ruptured AAA, those admitted for elective repair and those admitted as an emergency with an acute (non-ruptured) aneurysm. RESULTS: There was a decline in the incidence of both emergency and elective procedures for AAA after 1992. While the mortality rate from ruptured AAA has also fallen since 1991, the overall case fatality rate for ruptured AAA has fallen by only 1.3 per cent (from 80.7 to 79.3 per cent). CONCLUSION: The decline in mortality rate and emergency procedures may result from a fall in the incidence of ruptured AAA, due to an increasing rate of elective surgery before 1992. The decline in elective procedures from 1992 may be due to a fall in the prevalence of AAA owing to high rates of elective surgery, or to a fall in the incidence of the disease itself.

The Quality of Surgical Care Project: benchmark standards of open resection for abdominal aortic aneurysm in Western Australia.

BACKGROUND: The Quality of Surgical Care Project (QSCP) was established in May 1996, to evaluate surgical outcomes and where indicated, recommend changes to improve the quality of surgical care in Western Australia (WA). The purpose of this study is to establish benchmark standards in WA for operative mortality, 5-year survival and length of stay in all patients who were surgically treated for aneurysm of the abdominal aorta (AAA) in WA. METHODS: The WA Linked Database was used to link the morbidity and mortality records of all patients admitted and surgically treated for AAA in WA from 1985 to 1994. The linked chains of de-identified hospital morbidity and death records were selected using diagnostic and procedure codes pertaining to AAA. Three groups were separated for analysis: those admitted for rupture, those admitted for elective repair, and those who were admitted to hospital as an emergency without mention of rupture but who underwent repair for AAA. Independent analysis for gender and patients 80 years or more were included in the study. Patients were excluded from the study if they were less than 55 years of age. RESULTS: A total of 1475 cases (1257 males, 218 females) were identified. The mean age in elective cases was 70.4 years in males and 72.4 years in females, and for rupture the mean ages were 71.9 and 74.8 years, respectively. Median length of stay for males was 12 days for elective cases. Admission type or age did not significantly influence length of stay. Thirty-day mortality in males was 4.4% for elective repair and 36.7% for ruptured AAA and 5-year survival was 71.7 and 47.7%, respectively. The overall case fatality rate for ruptured AAA was 79.3% which included those cases who died from rupture without being admitted to hospital. CONCLUSIONS: These community-wide data provide a realistic measure of surgical performance for open repair of AAA. The outcomes for elective and rupture repair for AAA compare favourably with standards reported by international centres of excellence. They also support the use of this procedure in patients over 80 years of age with rupture. This information can be used for ongoing audit purposes and as a benchmark for the introduction of new treatment modalities.

The Quality of Surgical Care Project: a model to evaluate surgical outcomes in Western Australia using population-based record linkage.

BACKGROUND: The aim of this study is to establish a model to evaluate surgical outcomes and, where indicated, recommend changes to improve the quality of surgical care in Western Australia (WA). Open resection for aneurysm of the abdominal aorta was the first procedure evaluated and the results are reported in an accompanying paper. METHODS: The Quality of Surgical Care Project (QSCP) is conducted under the aegis of the Royal Australasian College of Surgeons (RACS) in WA, and brings together a multidisciplinary team of surgeons, public health researchers and health service administrators. The Western Australia Health Services Research Linked Database (the WA Linked Database) is used to provide linked chains of patients records residing in the state health department from the following sources: hospital morbidity data system, birth and death records, mental health services data, cancer registrations and midwives' notifications. This links 16 years of population-based patient records from 1980, including all public and private hospital admissions and re-admissions. The Quality of Surgical Care Project was established to use and to correlate the data from the WA Linked Database. RESULTS: The result is a powerful database for a contained population that is available for scientific analysis by a multidisciplinary team of clinical epidemiologists, surgeons and health service managers. Users will have the ability to establish benchmark standards for the outcomes of surgical procedures in WA for use in quality improvement programmes run by the College and will facilitate self-directed performance auditing activities as a commitment to greater community accountability. CONCLUSIONS: The Quality of Surgical Care Project provides a potential model of benefits to be realized by both the medical profession and the community through multidisciplinary collaboration supported by adequate information. Although migration from WA is relatively low, future linkage to the state electoral roll will allow correction for any population change.

Analytical modeling and numerical simulation of forces in an endoluminal graft.

PURPOSE: To utilize mathematical analysis and computational fluid dynamics (CFD) to investigate the forces acting within the pressurized aorta and upon a stent-graft and how these forces may affect the ongoing performance of the stent-graft. METHODS: Analytical force balance analysis and CFD simulations using the Fluent code were used to mimic blood flow through a bifurcated stent-graft in a person at rest. Steady-state blood flow was assumed in which the inlet pressure approximated the mean blood pressure (100 mm Hg) and the blood flow velocity was an approximation of the peak systolic flow rate (0.6 m/s). Two sizes of endoluminal grafts were analyzed: the larger graft had an inlet diameter of 3 cm and outlet diameters of 1 cm; the smaller graft diameters measured 2.4 cm proximally and 1.2 cm distally. The endografts were studied in 2 configurations: with the limbs straight and with one bent. RESULTS: For the larger graft model, the normal peak blood flow induced a downward force of 7 to 9 N on the bifurcated grafts. Bending one of the limbs of the graft produced a sideways force of 1.3 N. For the smaller endograft, the downward force was in the range of 3.1 to 5.1 N and the sideways force on a curved limb was approximately 1.5 N. The magnitude of the forces given by the analytical formulae and the CFD results agreed to within 2 significant figures. CONCLUSIONS: These results suggest that the downward force on a bifurcated stent-graft, which may exceed the force required to dislodge it when relying on radial attachment alone, is determined mostly by the proximal graft diameter. Curvature of the graft limbs creates an additional sideways force that works to displace the distal limbs of the graft from the iliac arteries.