A model for national outcome audit in vascular surgery

Prediction of outcome after abdominal aortic aneurysm rupture

BACKGROUND

Most vascular surgeons practice a selective policy of operative intervention for patients with ruptured abdominal aortic aneurysm (AAA). The evidence on which to justify operative selection remains uncertain. This review examines the prediction of outcome after attempted open repair of ruptured AAA.

METHODS

The Medline and EMBASE databases and Cochrane Database of Systematic Reviews were searched for clinical studies relating to the prediction of outcome after ruptured AAA. Reference lists of relevant articles were also reviewed.

RESULTS

The last 20 years has seen >60 publications considering variables predictive of outcome after AAA rupture. Four predictive scoring systems are reported: Hardman Index, Glasgow Aneurysm Score, Physiological and Operative Severity Score for Enumeration of Mortality and Morbidity (POSSUM), and the Vancouver Scoring System. No scoring system has been shown to have consistent or absolute validity. Of the remaining data, there are no individual or combination of variables that can accurately and consistently predict outcome.

CONCLUSIONS

Little robust evidence is available on which to base preoperative outcome prediction in patients with ruptured AAA. Experienced clinical judgement will remain of foremost importance in the selection of patients for ruptured AAA repair.

Estimation of physiologic ability and surgical stress (E-PASS) as a predictor of immediate outcome after elective abdominal aortic aneurysm surgery

BACKGROUND

The Estimation of Physiologic Ability and Surgical Stress (E-PASS) score was designed on the premise that the balance between the patient's physiologic reserve capacity and the surgical stress inflicted at operation was important in the occurrence of postoperative complications. The aim of this study was to assess its value in predicting mortality and morbidity after open elective abdominal aortic aneurysm (AAA) repair.

METHODS

E-PASS data items were collected prospectively in a group of 204 patients undergoing elective open AAA repair over a 6-year period. The operative morbidity and mortality rates were compared with the preoperative risk score (PRS), surgical stress score (SSS) and comprehensive risk score (CRS) of E-PASS. The group comprised 180 (88%) males and the median age was 73 (range 44 to 86) years.

RESULTS

There were 13 (6%) deaths and 121 (59%) experienced a postoperative complication. As the PRS, SSS and CRS increased, the incidence of postoperative morbidity and mortality significantly increased (P < .0001). Overall mean CRS was .52 (+/-.27). Mean CRS in the groups of patients who survived and died were .49 (+/-.24) and .98 (+/-26), respectively. PRS, SSS, and CRS all had extremely good predictive power for both mortality and morbidity as demonstrated by high areas under the receiver operator curve (range .799 to .953). CRS also showed a strong statistically significant association with the severity of postoperative complication (P < .0001) and length of hospital stay (P < .0001).

CONCLUSIONS

The E-PASS model appears to be a promising method of predicting death and the development of postoperative complications in patients undergoing elective open AAA surgery. It requires further validation in arterial surgery at different geographical locations.

POSSUM models in open abdominal aortic aneurysm surgery

OBJECTIVES

This study evaluated the Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity (POSSUM), Portsmouth (P) POSSUM and Vascular (V) POSSUM. The primary aim was to assess the validity of these scoring systems in a population of patients undergoing elective and emergency open AAA repair. The secondary intention was in the event that these equations did not fit all patients with an aneurysm; a new model would be developed and tested using logistic regression from the local data (Cambridge POSSUM).

METHODS

POSSUM data items were collected prospectively in a group of 452 patients undergoing elective and emergency open AAA repair over an eight-year period. The operative mortality rates were compared with those predicted by POSSUM, P-POSSUM, V-POSSUM and Cambridge POSSUM.

RESULTS

All models except V-POSSUM (physiology only) showed significant lack of fit when predicting mortality after open AAA surgery. It was found that the locally generated single unified model (Cambridge POSSUM) could successfully describe both elective and ruptured AAA mortality with good discrimination (chi(2)=9.24, 7 d.f., p=0.236, c-index=0.880).

CONCLUSIONS

POSSUM, V-POSSUM and P-POSSUM may not be robust tools for comparing mortality between populations undergoing elective and emergency open AAA repair as once thought. The development and successful validation of Cambridge POSSUM provides a unified model to describe both elective and emergency AAAs together and should be validated in other geographical settings.

Pre-operative risk scores for the prediction of outcome in elderly people who require emergency surgery

Background

The decision on whether to operate on a sick elderly person with an intra-abdominal emergency is one of the most difficult in general surgery. A predictive risk-score would be of great value in this situation.

Methods

A Medline search was performed to identify those predictive risk-scores relevant to sick elderly patients in whom emergency surgery might be life-saving.

Results

Many of the risk scores for surgical patients include the operative findings or require tests which are not available in the acute situation. Most of the relevant studies include younger patients and elective surgery. The Glasgow Aneurysm Score and Hardman Index are specific to ruptured aortic aneurysm while the Boey Score and the Hacetteppe Score are specific to perforated peptic ulcer. The Reiss Index and Fitness Score can be used pre-operatively if the elements of the score can be completed in time. The ASA score, which includes a significant element of subjective clinical judgement, can be augmented with factors such as age and urgency of surgery but no test has a negative predictive value sufficient to recommend against surgical intervention without clinical input.

Conclusion

Risk scores may be helpful in sick elderly patients needing emergency abdominal surgery but an experienced clinical opinion is still essential.

Evaluation of various POSSUM models for predicting mortality in patients undergoing elective oesophagectomy for carcinoma

Background

The aim of the study was to validate the use of the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM), Portsmouth (P) POSSUM and upper gastrointestinal (O) POSSUM models in patients undergoing elective thoracic oesophagectomy for carcinoma.

Methods

The observed in-hospital mortality rates in 545 patients undergoing elective thoracic oesophagectomy for squamous cell carcinoma of the oesophagus in all public hospitals in Hong Kong was compared with rates predicted by POSSUM, P-POSSUM and O-POSSUM. The discriminatory power of these models was assessed using receiver–operator characteristic (ROC) curve analysis.

Results

The observed mortality rate was 5·5 per cent, whereas rates predicted by POSSUM, P-POSSUM and O-POSSUM were 15·0, 4·7 and 10·9 per cent respectively. P-POSSUM showed no lack of fit (P = 0·814), but POSSUM (P &lt; 0·001) and O-POSSUM (P = 0·002) showed lack of fit against observed mortality. POSSUM overpredicted mortality across nearly all risk groups, whereas O-POSSUM overpredicted mortality in patients with low physiological scores and in older patients. POSSUM (area under ROC curve 0·776) and P-POSSUM (0·776) showed equally good discriminatory power but O-POSSUM (0·676) was inferior.

Conclusion

P-POSSUM provided the most accurate prediction of in-hospital mortality in this group of patients who had elective oesophagectomy.

VBHOM, a data economic model for predicting the outcome after open abdominal aortic aneurysm surgery

Background

Vascular Biochemistry and Haematology Outcome Models (VBHOM) adopted the approach of using a minimum data set to model outcome. This study aimed to test such a model on a cohort of patients undergoing open elective and non-elective abdominal aortic aneurysm (AAA) repair.

Methods

A binary logistic regression model of risk of in-hospital mortality was built from the 2002–2004 submission to the UK National Vascular Database (NVD) (2718 patients). The subset of NVD data items used comprised serum levels of urea, sodium and potassium, haemoglobin, white cell count, sex, age and mode of admission. The model was applied prospectively using Hosmer–Lemeshow methodology to a test data set from the Cambridge Vascular Unit.

Results

The validation set contained 327 patients, of whom 208 had elective AAA repair and 119 had emergency repair of a ruptured AAA. Outcome following elective and non-elective AAA repair could be described accurately using the same model. The overall mean predicted risk of death was 14·13 per cent, and 48 deaths were predicted. The actual number of deaths was 53 (χ2 = 8·40, 10 d.f., P = 0·590; no evidence of lack of fit). The model also demonstrated good discrimination (c-index = 0·852).

Conclusion

The VBHOM approach has the advantage of using simple, objective clinical data that are easy to collect routinely. The VBHOM data items potentially allow prediction of risk in an individual patient before aneurysm surgery.

Comparison of Mortality Prediction Models after Open Abdominal Aortic Aneurysm Repair

OBJECTIVES

Comparison of the accuracy of prediction of contemporary mortality prediction models after open Abdominal Aortic Aneurysm (AAA) surgery.

METHODS

Post-operative data were collected from AAA patients from 2 UK Intensive Care Units (ICU). POSSUM and VBHOM based models were compared to the APACHE-AAA model which was able to adjust for the hospital-related effect on outcome. Model performance was assessed using measures of calibration, discrimination and subgroup analysis.

RESULTS

541 patients were studied. The in-hospital mortality rate for elective AAA repair (325 patients) was: 6.2% (95% confidence interval (c.i.) 3.5 to 8.8) and for emergency repair (216 patients) was: 28.7% (95% c.i. 22.5-34.9). The APACHE-based model had the best overall fit to the whole population of AAA patients, and also separately in elective and emergency patients. The V-POSSUM physiology-only (p<0.001) and VBHOM (p=0.011) models had a poor fit in elective patients. The RAAA-POSSUM physiology-only (p<0.001) and VBHOM models (p=0.010) had a poor fit in emergency patients.

CONCLUSIONS

The APACHE-AAA model with its ability to adjust for both the hospital-related "effect" as well as the patient case-mix, was a more accurate risk stratification model than other contemporary models, in the post-operative AAA patient managed in ICU.

POSSUM predicts decreased overall survival in curative resection for colorectal cancer

PURPOSE

Poor condition at operation determined by the physiologic POSSUM score is related to postoperative mortality and morbidity of colorectal cancer surgery. This study was designed to analyze the relationship between condition of patients with colorectal cancer at operation and long-term overall survival.

METHODS

A total of 542 patients survived a radical resection for Stages I, II, or III colorectal cancer. Physiologic POSSUM score at surgery, exclusive of age, was calculated for all patients. Mean physiologic POSSUM score was used as cutoff point to determine low-risk and high-risk group patients. A Cox proportional hazard analysis was performed to study the effect of low-risk and high-risk group on overall survival and to identify independent risk factors.

RESULTS

Five-year overall survival was significantly higher in low-risk group patients than in high-risk group patients (low-risk group 66.6 percent vs. high-risk group 48.5 percent; P < 0.001). Differences in overall survival also were found when patients in Stages I, II, and III were analyzed separately. Risk factors for overall survival were advanced stage of disease, poor tumor differentiation, mucinous adenocarcinoma, older than age 70 years, and poor condition of the patient at time of operation.

CONCLUSIONS

Poor condition at operation, as determined by physiologic POSSUM score, is a risk indicator for long-term overall survival in colorectal cancer patients.

Risk Scoring in Perioperative and Surgical Intensive Care Patients: A Review

PURPOSE

Assessing the risk and predicting the outcome of surgery, trauma, and surgical intensive care is an important aspect of perioperative practice. There have been attempts to devise and validate many scoring systems to predict the prognosis of patients having a similar severity of illness. This article reviews some of the commonly used systems with respect to their development, strengths, and limitations.

SOURCES

Published literature describing risk assessment scores and physiologic scoring systems for preoperative assessment, trauma, and surgical intensive care patients.

PRINCIPAL FINDINGS

Risk scores used in preoperative evaluation assist the clinician in optimizing the patient before, during, and after surgery. Scoring systems applied in intensive care units are useful as guidelines rather than accurate predictors of prognosis for individual patient. Many models are used for audit purposes, and some are used as performance measures and quality indicators of a unit; however, both utilities are controversial because of poor adjustment of these systems to case-mixtures.

CONCLUSIONS

Risk assessment scores may assist in the perioperative risk evaluation with respect to organ systems. Prognostication of critically ill patients belonging to a category of illness may be done using physiological scoring systems taking into account the difference in the case-mix of the particular unit.

Optimal prediction of mortality after abdominal aortic aneurysm repair with statistical models

OBJECTIVE

To identify the best method for the prediction of postoperative mortality in individual abdominal aortic aneurysm surgery (AAA) patients by comparing statistical modelling with artificial neural networks' (ANN) and clinicians' estimates.

METHODS

An observational multicenter study was conducted of prospectively collected postoperative Acute Physiology and Chronic Health Evaluation II data for a 9-year period from 24 intensive care units (ICU) in the Thames region of the United Kingdom. The study cohort consisted of 1205 elective and 546 emergency AAA patients. Four independent physiologic variables-age, acute physiology score, emergency operation, and chronic health evaluation-were used to develop multiple regression and ANN models to predict in-hospital mortality. The models were developed on 75% of the patient population and their validity tested on the remaining 25%. The results from these two models were compared with the observed outcome and clinicians' estimates by using measures of calibration, discrimination, and subgroup analysis.

RESULTS

Observed in-hospital mortality for elective surgery was 9.3% (95% confidence interval [CI], 7.7% to 11.1%) and for emergency surgery, 46.7% (95% CI, 42.5 to 51.0%). The ANN and the statistical models were both more accurate than the clinicians' predictions. Only the statistical model was internally valid, however, when applied to the validation set of observations, as evidenced by calibration (Hosmer-Lemeshow C statistic, 14.97; P = .060), discrimination properties (area under receiver operating characteristic curve, 0.869; 95% CI, 0.824 to 0.913), and subgroup analysis.

CONCLUSIONS

The prediction of in-hospital mortality in AAA patients by multiple regression is more accurate than clinicians' estimates or ANN modelling. Clinicians can use this statistical model as an objective adjunct to generate informed prognosis.

Evaluation of outcome of laparoscopic colorectal resection with POSSUM, Portsmouth POSSUM and colorectal POSSUM

BACKGROUND

This study evaluated the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM), Portsmouth (P) POSSUM and colorectal (CR) POSSUM in laparoscopic colorectal resection.

METHODS

Observed mortality and morbidity rates in 400 patients who underwent laparoscopic colorectal resection were compared with those predicted by POSSUM, P-POSSUM and CR-POSSUM.

RESULTS

Observed mortality and morbidity rates were 0.5 and 19.0 per cent respectively. Mortality rates predicted by POSSUM, P-POSSUM and CR-POSSUM were 10.8, 4.0 and 5.6 per cent respectively, and the morbidity rate predicted by POSSUM was 43.0 per cent. The predicted and observed mortality and morbidity rates showed significant lack of fit. The conversion rate to open surgery was 11.5 per cent. The mortality rate for patients having conversion was 2 per cent and was not significantly different to that predicted by P-POSSUM (4 per cent; P = 0.493) or CR-POSSUM (5 per cent; P = 0.370). In this group, the observed and POSSUM-predicted morbidity rates were also similar (43 versus 48 per cent respectively; P = 0.104).

CONCLUSION

POSSUM, P-POSSUM and CR-POSSUM overestimated mortality and morbidity in patients who underwent laparoscopic colorectal resection. However, the mortality rate in patients who required conversion fitted the models of P-POSSUM and CR-POSSUM, and the morbidity rate was comparable to that predicted by POSSUM.

Risk-adjusted analysis of early mortality after ruptured abdominal aortic aneurysm repair

PURPOSE

Ruptured abdominal aortic aneurysms (RAAAs) continue to result in early mortality in up to 50% of patients. Additionally, it remains difficult to compare outcomes given the variability in patient comorbidities and presentation. The purpose of this study was to describe an instrument that permits the prospective analysis of outcomes after RAAA repair while adjusting for the variability in preoperative risk.

METHODS

Consecutive patients undergoing attempted open RAAA repair over a 5-year period (1999 to 2003) at our center were reviewed. Thirty-day or in-hospital mortality was the main outcome variable. Preoperative mortality risk was estimated for each patient by using a validated modification of the POSSUM scoring system (V-POSSUM). A risk-adjusted cumulative sum method (RA-CUSUM) was used to compare observed versus predicted outcomes by assigning a risk-adjusted score, based on log-likelihood ratios, to each patient. These scores were sequentially plotted with preset control limits to allow for "signaling" when results were substantially different from expected (doubling or halving of odds ratios).

RESULTS

A total of 136 patients were reviewed, with an early mortality rate of 45.6%. V-POSSUM scores were accurate in predicting mortality for the entire cohort, with an observed-to-predicted mortality ratio of 0.92 (P = .80). Each patient's risk-adjusted score was plotted sequentially. In one segment of the resulting plot, the graph adopted a negative slope and crossed the lower control limit, indicating improved results compared with predicted.

CONCLUSIONS

V-POSSUM scores in this series accurately predicted early mortality after RAAA surgery. The RA-CUSUM method allows for the prospective evaluation of outcomes, while taking into account patient variability. In the current study, this resulted in the identification of a series of patients who had improved outcomes compared with predicted.

Quantification of mortality risk after abdominal aortic aneurysm repair

Background

The study was designed to evaluate the Acute Physiology And Chronic Health Evaluation (APACHE) II risk scoring system in abdominal aortic aneurysm (AAA) surgery. The aim was to create an APACHE-based risk stratification model for postoperative death.

Methods

Prospective postoperative APACHE II data were collected from patients undergoing AAA repair over a 9-year interval from 24 intensive care units (ICUs) in the Thames region. A multilevel logistic regression model (APACHE-AAA) for in-hospital mortality was developed to adjust for both case mix and the variation in outcome between ICUs.

Results

A total of 1896 patients were studied. The in-hospital mortality rate among the 1289 patients who had elective AAA repair was 9·6 (95 per cent confidence interval (c.i.) 8·0 to 11·2) per cent and that among the 605 patients who had an emergency repair was 46·9 (95 per cent c.i. 43·0 to 50·9) per cent. Four independent predictors of death were identified: age (odds ratio (OR) 1·05 (95 per cent c.i. 1·03 to 1·07) per year increase), Acute Physiology Score (OR 1·14 (95 per cent c.i. 1·12 to 1·17) per unit increase), emergency operation (OR 4·86 (95 per cent c.i. 3·64 to 6·52)) and chronic health dysfunction (OR 1·43 (95 per cent c.i. 1·04 to 1·97)). The APACHE-AAA model was internally valid, as shown by calibration (Hosmer–Lemeshow C statistic: χ2 = 6·14, 8 d.f., P = 0·632), discrimination properties (area under receiver–operator characteristic curve 0·845) and subgroup analysis. There was no significant variation in outcome between hospitals.

Conclusion

APACHE-AAA was shown to be an accurate risk-stratification model that could be used to quantify the risk of death after AAA surgery. It might also be used to determine the relative impact of ICU over high-dependency unit care.

Regional anaesthesia and propofol sedation for carotid endarterectomy

BACKGROUND

Many surgeons now perform carotid endarterectomy under regional anaesthesia. The aim of the present study was to review a sedation technique using a computer-controlled infusion of propofol.

METHODS

A consecutive series of 84 carotid endarterectomies done by a single surgeon and commenced under regional anaesthesia with sedation was studied. There were 54 men and 27 women (three bilateral procedures), with a median age of 71 years (range 48-87 years). All patients had carotid stenosis > 70% 80 procedures were done for symptomatic disease and three asymptomatic patients were treated before cardiac surgery (one bilateral).

RESULTS

Seventy-seven procedures were completed under regional anaesthesia and sedation alone; seven required conversion to general anaesthetic, usually for intolerance of the operation. An intraoperative shunt was required on only four occasions (5%). Postoperatively eight patients required critical care monitoring, usually for blood pressure control. The remainder were nursed on the vascular ward, and 68% were discharged home on the day after surgery. No patient died, but there were two neurological complications. One patient had a cerebellar stroke 10 days after surgery, but recovered fully after 4 months. A second developed cerebral oedema due to severe intraoperative hypertension and required intensive care for 15 days. He too recovered fully. Five patients had a further episode of transient cerebral ischaemia within 1 month of operation, but in all cases duplex imaging showed a widely patent carotid and there were no sequelae.

CONCLUSION

Target controlled propofol infusion is an effective method of sedation in patients undergoing carotid endarterectomy.

Risk-adjusted predictive models of mortality after index arterial operations using a minimal data set

Background

Reducing the data required for a national vascular database (NVD) without compromising the statistical basis of comparative audit is an important goal. This work attempted to model outcomes (mortality and morbidity) from a small and simple subset of the NVD data items, specifically urea, sodium, potassium, haemoglobin, white cell count, age and mode of admission.

Methods

Logistic regression models of risk of adverse outcome were built from the 2001 submission to the NVD using all records that contained the complete data required by the models. These models were applied prospectively against the equivalent data from the 2002 submission to the NVD.

Results

As had previously been found using the P-POSSUM (Portsmouth POSSUM) approach, although elective abdominal aortic aneurysm (AAA) repair and infrainguinal bypass (IIB) operations could be described by the same model, separate models were required for carotid endarterectomy (CEA) and emergency AAA repair. For CEA there were insufficient adverse events recorded to allow prospective testing of the models. The overall mean predicted risk of death in 530 patients undergoing elective AAA repair or IIB operations was 5·6 per cent, predicting 30 deaths. There were 28 reported deaths (χ2 = 2·75, 4 d.f., P = 0·600; no evidence of lack of fit). Similarly, accurate predictions were obtained across a range of predicted risks as well as for patients undergoing repair of ruptured AAA and for morbidity.

Conclusion

A ‘data economic’ model for risk stratification of national data is feasible. The ability to use a minimal data set may facilitate the process of comparative audit within the NVD.

POSSUM scoring for patients with fractured neck of femur † †An abstract of part of the study was presented at the Anaesthetic Research Society meeting, Aberdeen, April 2004 and published in British Journal of Anaesthesia 2004; 93: 161

BACKGROUND

POSSUM scoring is validated as an audit tool in general and orthopaedic surgery. It is also used for preoperative triage to assess perioperative risk. However its ability to predict mortality in specific surgical subgroups, such as patients with fractured neck of the femur, has not been studied. This study assessed the predictive capability of POSSUM for 30-day mortality after surgery for fractured neck of femur.

METHODS

A cohort study was conducted in Queen's Medical Centre, Nottingham over a period of nearly 2 yr. Complete data from 1164 patients were analysed to compare the mortality predicted by POSSUM and the observed mortality. POSSUM risk of death was calculated using the original POSSUM equation, with modifications to the operative score appropriate for orthopaedic surgery.

RESULTS

POSSUM predicted 181 (15.6%) deaths and the observed mortality was 119 (10.2%). The area under the receiver operating characteristic curve was 0.62, indicating poor performance by the POSSUM equation.

CONCLUSION

POSSUM overpredicts mortality in hip fracture patients. It should be used with caution whether as an audit tool or for preoperative triage.

Development of a dedicated risk-adjustment scoring system for colorectal surgery (colorectal POSSUM)

BACKGROUND

The aim of the study was to develop a dedicated colorectal Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (CR-POSSUM) equation for predicting operative mortality, and to compare its performance with the Portsmouth (P)-POSSUM model.

METHODS

Data were collected prospectively from 6883 patients undergoing colorectal surgery in 15 UK hospitals between 1993 and 2001. After excluding missing data and 93 patients who did not satisfy the inclusion criteria, 4632 patients (68.2 per cent) underwent elective surgery and 2107 had an emergency operation (31.0 per cent); 2437 operations (35.9 per cent) for malignant and 4267 (62.8 per cent) for non-malignant diseases were scored. Stepwise logistic regression analysis was used to develop an age-adjusted POSSUM model and a dedicated CR-POSSUM model. A 60:40 per cent split-sample validation technique was adopted for model development and testing. Observed and expected mortality rates were compared.

RESULTS

The operative mortality rate for the series was 5.7 per cent (387 of 6790 patients) (elective operations 2.8 per cent; emergency surgery 12.0 per cent). The CR-POSSUM, age-adjusted POSSUM and P-POSSUM models had similar areas under the receiver-operator characteristic curves. Model calibration was similar for CR-POSSUM and age-adjusted POSSUM models, and superior to that for the P-POSSUM model. The CR-POSSUM model offered the best overall accuracy, with an observed : expected ratio of 1.000, 0.998 and 0.911 respectively (test population).

CONCLUSION

The CR-POSSUM model provided an accurate predictor of operative mortality. External validation is required in hospitals different from those in which the model was developed.

Screening for abdominal aortic aneurysms in men

Gloucestershire's screening project shows the potential benefits of a national programme and how it could be run

The post-operative mortality of ruptured abdominal aortic aneurysm repair

INTRODUCTION

Late peri-operative death after ruptured abdominal aortic aneurysm (RAAA) repair is usually due to multiple-organ failure. The aim of this study was to identify any factors that are associated with mortality in this group of patients.

METHODS

A retrospective case-note review of a single decade's operative experience of RAAA repair in a single centre. Only those patients with confirmed rupture at laparotomy were included. Sixty-three pre- intra- and post-operative variables were recorded where possible for each patient who survived surgery and the initial 24-hours post-operatively. Multi-variate analysis was performed using stepwise logistic regression. The P-POSSUM, RAAA-POSSUM, RAAA-POSSUM (physiology only), V-POSSUM, and V-POSSUM (physiology only) models were all compared to determine how each performed in these patients.

RESULTS

Two hundred and twenty-three cases of confirmed RAAA were identified, of whom 139 survived the operation and initial 24-hours post-operatively. In-hospital mortality in this group of patients was 32.4%. Variables significantly associated with mortality after multi-variate analysis, were low intra-operative systolic blood pressure, the presence of a consultant anaesthetist at the initial operation and the development of cardiac, renal or gastro-intestinal complications. All POSSUM models except the V-POSSUM and P-POSSUM (physiology only) models demonstrated no significant lack of fit in this dataset.

DISCUSSION

Factors associated with delayed peri-operative death after RAAA are not the same as those previously found to be associated with overall peri-operative mortality after RAAA repair.

Comparative audit of abdominal aortic aneurysm repairs using POSSUM scores

Abdominal aortic aneurysm (AAA) repairs represent a significant workload in vascular surgery in Asia. This study aimed to audit AAA surgery and evaluate the application of the Portsmouth Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity (P-POSSUM) in an Asian vascular unit for standard of care. Eighty-five consecutive surgical patients with AAA from a prospective vascular database from July 1996 to December 2001 in Sarawak were available for analysis. Comparisons between predicted deaths by P-POSSUM and observed deaths in both urgency of surgery categories (elective, urgent, emergency ruptures) and risk range groups (0-5%, >5-15%, >15-50%, >50-100%) were made. No significant difference was found between the predicted and observed rates of death for elective, urgent and emergency AAA repairs. The observed mortality rates were 5%, 18% and 30%, respectively. The observed rates of death were also comparable to P-POSSUM predicted rates of death in the various risk range groups. The POSSUM score used with the P-POSSUM mortality equation is easy to use and applicable as a comparative vascular auditing tool in Asia.

Use of mortality rate after aortic surgery as a performance indicator

BACKGROUND

Hospital episode statistics (HES) regarding death after aortic surgery were analysed to evaluate their potential value as a performance indicator.

METHODS

HES data for all acute hospitals in England and Wales from 1996 to 2001 were analysed retrospectively. In-hospital mortality was calculated for all patients over 40 years of age who underwent abdominal aortic procedures or died in hospital with a primary diagnosis of aortic aneurysm.

RESULTS

Some 38 319 cases were identified, of which 8.9 per cent were complex, 46.8 per cent were elective and 44.4 per cent were emergencies. The elective mortality rate was 6.4 per cent overall; that after emergency operation was 35.0 per cent, rising to 41.6 per cent if urgent procedures were excluded and 63.1 per cent if unoperated cases were included. Over the 5-year interval a median of 68 (interquartile range 30-108) elective procedures were carried out by individual hospitals. Considerable variation was identified in the proportion of elderly patients, tertiary referrals and the proportion of emergency admissions that had surgery.

CONCLUSION

The use of mortality data may be misleading owing to identifiable differences in case mix and selection. Some redefinition of groups may help to provide more valid data, but ultimately only high-quality data with clinical information are likely to allow meaningful comparisons of performance.

Comparison of POSSUM scoring and the Hardman Index in selection of patients for repair of ruptured abdominal aortic aneurysm

BACKGROUND

The aim was to assess to what extent the POSSUM (Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity) and Hardman scoring systems were predictive of outcome after surgery for ruptured abdominal aortic aneurysm (RAAA).

METHODS

From January 1990 to December 2001, 232 patients presented with RAAA. Forty-one were treated conservatively and all died; the remainder had emergency surgery. The case notes of all but three of these patients were reviewed retrospectively. POSSUM and Hardman scores were calculated and related to mortality.

RESULTS

The mortality rate after emergency repair was 54 per cent (104 of 191). The physiology-only POSSUM score specific for RAAA and the Hardman Index score were both significantly associated with increased mortality after operation (P < 0.001). Most non-operated patients were in the highest risk bands.

CONCLUSION

Both POSSUM and Hardman scoring systems predicted outcome after emergency surgery for RAAA. The Hardman Index was simpler to calculate, but POSSUM identified a higher number of patients at risk. Risk scoring may help identify patients with RAAA for whom surgery is futile.

Evaluation of POSSUM and P-POSSUM scoring systems in patients undergoing colorectal surgery

BACKGROUND

The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) and Portsmouth POSSUM (P-POSSUM) equations were derived from a heterogeneous general surgical population and have been used successfully as audit tools to provide risk-adjusted operative mortality rates. Their applicability to high-risk emergency colorectal operations has not been established.

METHODS

POSSUM variables were recorded for 1017 patients undergoing major elective (n = 804) or emergency (n = 213) colorectal surgery in ten hospitals. Subgroup analysis was performed to investigate the predictive capability of POSSUM and P-POSSUM in emergency and elective surgery and in patients in different age groups.

RESULTS

The overall operative mortality rate was 7.5 per cent (POSSUM-estimated mortality rate 8.2 per cent; P-POSSUM-estimated mortality rate 7.1 per cent). In-hospital deaths increased exponentially with age. Both scoring systems overpredicted mortality in young patients and underpredicted mortality in the elderly (P < 0.001). Death was underpredicted by both systems for emergency cases, significantly so at a simulated emergency caseload of 47.9 per cent (P < 0.05).

CONCLUSION

There is a lack of calibration of POSSUM and P-POSSUM systems at the extremes of age and high emergency workload. This has important implication in clinical practice, as consultants with a high emergency workload may seem to underperform when these scoring systems are applied. Recalibration or remodelling strategies may facilitate the application of POSSUM-based systems in colorectal surgery.

The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM)

BACKGROUND AND METHODS

The development of the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) is described and its methods of analysis and value in a modern surgical practice are reviewed. A computerized search of all published data in Medline, the Cochrane Library and Embase was made for the last 12 years. Relevant articles were then searched manually for further papers on risk analysis, case-mix comparison and POSSUM methodology.

RESULTS AND CONCLUSION

POSSUM has been evaluated extensively in both general and specialist surgery. While there are problems with both data collection and analysis, when used correctly POSSUM can usefully compare outcomes between surgeons and between hospitals. In specialist surgery, individual regression equations may be needed for each index procedure.