Comparison of POSSUM with P-POSSUM for prediction of mortality in infrarenal abdominal aortic aneurysm repair

Tools and scores for general and cardiovascular perioperative risk assessment: a narrative review

The number of surgical procedures in the world is large and in Brazil it has been expressing a growth trend higher than the population growth. In this context, perioperative risk assessment safeguards the optimization of the outcomes sought by the procedures. For this evaluation, anamnesis and physical examination constitute an irreplaceable initial stage which may or may not be followed by complementary exams, interventions for clinical stabilization and application of risk estimation tools. The use of these tools can be very useful in order to obtain objective data for decision making by weighing surgical risk and benefit. Global and cardiovascular risk assessments are of greatest interest in the preoperative period, however information about their methods is scattered in the literature. Some tools such as the American Society of Anesthesiologists Physical Status (ASA PS) and the Revised Cardiac Risk Index (RCRI) are more widely known, while others are less known but can provide valuable information. Here, the main indices, scores and calculators that address general and cardiovascular perioperative risk were detailed.

Risk-Adjusted Analysis of Patients Undergoing Emergency Laparotomy Using POSSUM and P-POSSUM Score: A Prospective Study

Background:

Comparison of operative morbidity rates after emergency laparotomy between units may be misleading because it does not take into account the physiological variables of patients’ conditions. Surgical risk scores have been created, and the most commonly used is the Physiological and Operative Severity Score for the enumeration of Mortality (POSSUM) or one of its modifications, the Portsmouth-POSSUM (P-POSSUM), usually requires intraoperative information.

Objective:

The objective of this study is to evaluate the POSSUM and P-POSSUM scores in predicting postoperative morbidity and mortality in patients undergoing emergency laparotomy.

Methodology:

This is a prospective, cross-sectional, and hospital-based study that was conducted at J.L.N. Medical College and Hospital, Ajmer, Rajasthan, India, from April 2017 to December 2017. Adult patients who presented at the causality and underwent emergency laparotomy were included in the study. Observed and predicted mortality and morbidity were calculated using POSSUM and P-POSSUM equations, and statistical significance was calculated using Chi-square test.

Results:

A total of 100 patients were included in this study, with a mean age of 42.83 ± 18.21 years. The observed (O) mortality was 12 (12.0%), while POSSUM predicted 40 (40%) and P-POSSUM 27 (27%). The O/E ratio for POSSUM was 0.29 and for P-POSSUM was 0.44, and this means that they both overestimate mortality. When the results were tested by Chi-square test, the P value was found to be 0.55 and 0.85 for POSSUM and P-POSSUM, respectively, which showed no significant correlation for observed and expected mortality. The observed morbidity was 69 (69%), while POSSUM expected morbidity was 79 (79%), O/E ratio is 0.87, and this again overestimates the morbidity. POSSUM is overpredicting the rate of morbidity, and test of correlation showed no significance with P = 0.75.

Conclusion:

POSSUM and P-POSSUM were found to overestimate mortality and morbidity in our patient's population.

Estimation of V-POSSUM and E-PASS Scores in Prediction of Acute Kidney Injury in Patients after Elective Open Abdominal Aortic Aneurysm Surgery

BACKGROUND

V-POSSUM and E-PASS scoring systems are usually used to predict morbidity and early mortality in surgical patients. We conducted this study to assess the validity of the V-POSSUM and E-PASS scores in predicting risk of acute kidney injury (AKI) development in patients undergoing elective open abdominal aortic aneurysm (AAA) repair.

METHODS

We studied a consecutive series of 171 patients with AAA, qualified for elective open infrarenal repair. Patients underwent a thorough examination, and the physiological and surgical stress components of the V-POSSUM and E-PASS scores were calculated. The classification of patients in terms of postoperative AKI was performed in accordance with KDIGO criteria.

RESULTS

AKI was recognized in 62 patients. In these patients, we found significantly higher physiological and surgical stress components of V-POSSUM and E-PASS scores in relation to patients without AKI. ROC analysis showed that the E-PASS score with a cutoff point ≥0.796 and the V-POSSUM score (morbidity) with a cutoff point ≥77.2% with sensitivity of 75.8% and 74.2%, respectively, and with specificity of 83.5% for both, identified patients with postoperative AKI.

CONCLUSIONS

V-POSSUM and E-PASS scores have similar good properties in predicting postoperative AKI in patients undergoing elective open AAA repair.

Preoperative assessment of surgical risk: creation of a scoring tool to estimate 1-year mortality after emergency abdominal surgery in the elderly patient

BACKGROUND

The risk of mortality after emergency general surgery (EGS) in elderly patients is prolonged beyond initial hospitalization. Our objective was to develop a preoperative scoring tool to quantify risk of 1-year mortality.

METHODS

Three hundred ninety EGS patients aged 70 years or more were analyzed. Risk factors for 1-year mortality were identified using stepwise-forward logistic multivariate regression and weights assigned using natural logarithm of odds ratios. A geriatric emergency surgery mortality (GEM) score was derived from the aggregate of weighted scores. Leave-one-out cross-validation was performed.

RESULTS

One-year mortality was 32%. Risk factors and their weights were: acute kidney injury (2), American Society of Anesthesiology class greater than or equal to 4 (2), Charlson Comorbidity Index greater than or equal to 4 (1), albumin less than 3.5 mg/dL (1), and body mass index (less than 18.5 kg/m² [1]; 18.5 to 29.9 kg/m² [0]; ≥30 kg/m² [-1]). One-year mortality was: GEM 0 to 1 (0% to 7%); GEM 2 to 5 (32% to 68%); GEM 6 to 8 (94% to 100%). C-statistics were .82 and .75 in training and validation data sets, respectively.

CONCLUSIONS

A simple score using 5 clinical variables predicts 1-year mortality after EGS with reasonable accuracy and assists in preoperative counseling.

Single-Center Experience of Endovascular Abdominal Aortic Aneurysm Repair (EVAR) in Patients Not Participating in the U.K. EVAR Trials

The objective was to evaluate outcomes of a high-risk patient cohort following endovascular abdominal aortic aneurysm repair (EVAR) treatment not entered into the U.K. endovascular stent-graft aortic aneurysm repair trials (EVAR-1 or -2) because of equipoise absence but where EVAR was judged to be the most appropriate intervention option on compassionate grounds. A single-center retrospective analysis was performed involving all patients undergoing compassionate EVAR treatment during the EVAR-1 and -2 trial period. Over an 8-year period, 34 patients underwent compassionate EVAR procedure. The mean (SD) age was 76 (79) years. The mean (SD) preoperative physiology score (P-POSSUM) was 25 (8.3) with a mean (SD) predicted early mortality of 9.9% (16%). The actual early mortality in our study was 2.9% and morbidity was 35%. There were 8 cases of endoleak: type I (n = 2), type II (n = 5), and type IV (n = 1). Aneurysm-related mortality and all-cause mortality after 8 years were 5.8% and 23.5% respectively. Satisfactory outcome with low mortality (2.9%) and morbidity can be achieved in patients with compassionate indications, where clinicians judge EVAR to be an advantage over open abdominal aortic aneurysm repair. Based on our study, the early mortality (2.9%) in our compassionate EVAR group is comparable to EVAR-1 outcomes (1.7%) and better than EVAR-2 mortality results (9%). EVAR should therefore not be denied to a significant number of high-risk abdominal aortic aneurysm patients who fall between the EVAR-1 and EVAR-2 criteria.

Impact of Delay on Survival in Patients with Ruptured Abdominal Aortic Aneurysm

Rupture of the abdominal aortic aneurysm (RAAA) is a common surgical emergency. Surgical treatment of this condition carries a high morbidity and mortality rate. For successful outcome, an early diagnosis and prompt treatment are essential. However, recently, some centers have reported better results in patients whose surgery had been delayed because of interhospital transfer. Delay in treatment sometimes occurs as patients are transferred from one institution to another where specialized vascular care is available. This retrospective study sought to determine the effect of delay in treatment on the mortality of patients with RAAA repair.

The time from arrival at the emergency room to surgery and operative time were obtained from the case notes of 45 consecutive patients with RAAA. Patients' physiology scores on admission were calculated using V-POSSUM for the RAAA model.

Thirty-five patients were diagnosed with RAAA in the emergency room and were transferred to surgery. These patients were divided into two groups: patients who had surgery within 1 hour ( n = 23) and those in whom surgery was delayed for up to 4 hours ( n = 12).

There was no significant difference in physiology score between the two groups ( p = .12). The time to surgery and operative time with death as the outcome were plotted on a logistic regression model that showed that the delay in surgical treatment increases the mortality rate following RAAA repair ( p = .041). Furthermore, a long operative time was associated with a higher surgical mortality rate ( p = .029).

Delay to surgery and a long operation increase the mortality rate following RAAA repair. However, delay to surgery alone did not influence the mortality rate.

An evaluation of POSSUM and P-POSSUM scoring in predicting post-operative mortality in a level 1 critical care setting

Background

POSSUM and P-POSSUM are used in the assessment of outcomes in surgical patients. Neither scoring systems’ accuracy has been established where a level 1 critical care facility (level 1 care ward) is available for perioperative care. We compared POSSUM and P-POSSUM predicted with observed mortality on a level 1 care ward.

Methods

A prospective, observational study was performed between May 2000 and June 2008. POSSUM and P-POSSUM scores were calculated for all postoperative patients who were admitted to the level 1 care ward. Data for post-operative mortality were obtained from hospital records for 2552 episodes of patient care. Observed vs expected mortality was compared using receiver operating characteristic (ROC) curves and the goodness of fit assessed using the Hosmer-Lemeshow equation.

Results

ROC curves show good discriminative ability between survivors and non-survivors for POSSUM and P-POSSUM. Physiological score had far higher discrimination than operative score. Both models showed poor calibration and poor goodness of fit (Hosmer-Lemeshow). Observed to expected (O:E) mortality ratio for POSSUM and P-POSSUM indicated significantly fewer than expected deaths in all deciles of risk.

Conclusions

Our data suggest a 30-60% reduction in O:E mortality. We suggest that the use of POSSUM models to predict mortality in patients admitted to level 1 care ward is inappropriate or that a recalibration of POSSUM is required to make it useful in a level 1 care ward setting.

APACHE III score on ICU admission predicts hospital mortality after open thoracoabdominal and open abdominal aortic aneurysm repair

BACKGROUND

No prior studies, to our knowledge, have examined the performance of the Acute Physiology and Chronic Health Evaluation (APACHE) III score in predicting mortality of patients undergoing open thoracoabdominal aortic aneurysm (TAAA) or open abdominal aortic aneurysm (AAA) repair. We sought to evaluate APACHE III scores in the prediction of postoperative mortality in elective TAAA and AAA repairs.

METHODS

Over a 9-year period (July 1998 through June 2007), prospective data (demographics, admitting diagnosis, APACHE III score, intensive care unit [ICU] and hospital length of stay, ICU and hospital mortality) were collected by a dedicated APACHE III coordinator for all patients admitted to a tertiary academic surgical ICU (20 beds). Observational and comparative analyses were performed. Emergent repairs for ruptured aneurysms were excluded from the study.

RESULTS

Forty-one patients underwent open elective repair of TAAA and 404 underwent open elective repair of AAA. Mean age of the TAAA group was 63.4 ± 9.8 years and the AAA group was 70.3 ± 8.3 years. Mean APACHE III score was 54 (range: 10-103) for the TAAA group and 45 (range: 11-103) for the AAA group. The in-hospital mortality rate for TAAA patients was 4.9% (n = 2) and for AAA patients was 2.0% (n = 8). Mean APACHE III scores on ICU admission were significantly greater in nonsurvivors versus survivors (79 vs. 45, p < 0.0001). For the entire patient cohort, the APACHE III score on ICU admission was an excellent discriminator of hospital mortality (receiver operating characteristic and area under the curve 0.92 [standard error of 0.05, 95% CI: 0.83-1.0]).

CONCLUSIONS

APACHE III is an accurate predictor of survival to hospital discharge in both open elective TAAA and AAA repairs.

Evaluation of POSSUM for patients undergoing pancreatoduodenectomy

Background

Comparison of operative morbidity rates after pancreatoduodenectomy between units may be misleading because it does not take into account the physiological variable of the condition of the patients. The aim of the present study was to evaluate the Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity (POSSUM) for pancreatoduodenectomy patients and to look for risk factors associated with morbidity in a high-volume center.

Methods

Between January 1993 and April 2006, 652 patients underwent a pancreatoduodenectomy, 502 of them for malignant disease. POSSUM performance was evaluated by assessing the “goodness-of-fit” with the linear analysis method.

Results

Overall, 332 of the 652 patients (50.9%) had one or more complication after pancreatoduodenectomy, and 9 patients (1.4%) died. POSSUM had a significant lack of fit using goodness-of-fit analysis. In multivariate analysis, one statistically significant factor associated with morbidity and not incorporated in POSSUM (P < 0.05) was identified: ampulla of Vater adenocarcinoma (OR = 1.73, 95% CI: 1.07–2.80).

Conclusions

Overall, there is a lack of calibration of POSSUM among patients who undergo pancreatoduodenectomy.

Comparison of different methods of risk stratification in urgent and emergency surgery

Background

The aim was to compare a number of risk scoring systems prospectively in a cohort of patients who underwent non-elective surgery.

Methods

This was a cohort study of 2349 consecutive patients who had urgent or emergency surgery in a district general hospital in the UK. All patients were scored prospectively using the Revised Goldman Cardiac Risk Index (RGCRI), Portsmouth modification of the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM), Surgical Risk Score (SRS) and Biochemistry and Haematology Outcome Models (BHOM). Actual 30-day and 1-year survival rates were compared with the predicted outcomes using receiver–operator characteristic (ROC) curves and Hosmer–Lemeshow analysis.

Results

Some 141 patients (6·0 per cent) died within 30 days of operation. This increased to 254 (10·8 per cent) by 1 year. The area under the ROC curve for death within 30 days was 0·90 for P-POSSUM, 0·85 for SRS, 0·84 for BHOM and 0·73 for RGCRI. Only the first three risk scores were able to discriminate accurately within the groups (area under ROC curve over 0·8), with no significant variation between expected and observed mortality rates confirmed by Hosmer–Lemeshow analysis. Similar results were found for the ability of each score to predict outcome at 1 year.

Conclusion

P-POSSUM, SRS and BHOM scoring systems were all able to predict outcome after emergency and urgent surgery, but the SRS had the advantage of ease of calculation. BHOM requires only the most commonly available blood test data and the computer holding these data can easily perform the calculation.d.

Endovascular repair versus open surgery in patients with ruptured abdominal aortic aneurysms: clinical outcomes with 1-year follow-up

OBJECTIVE

To compare the clinical outcomes of treatment after endovascular repair and open surgery in patients with ruptured infrarenal abdominal aortic aneurysms (AAAs), including 1-year follow-up.

METHODS

All consecutive conscious patients with ruptured infrarenal AAAs who presented to our tertiary care teaching hospital between January 1, 2001, and December 31, 2005, were included in this study (n = 55). Twenty-six patients underwent endovascular repair, and 29 patients underwent open surgery. Patients who were hemodynamically too unstable to undergo a computed tomography angiography scan were excluded. Outcomes evaluated were intraoperative mortality, 30-day mortality, systemic complications, complications necessitating surgical intervention, and mortality and complications during 1-year follow-up. The statistical tests we used were the Student t test, chi2 test, Fisher exact test, and Mann-Whitney U test (two sided; alpha = .05).

RESULTS

Thirty-day mortality was 8 (31%) of 26 patients who underwent endovascular repair and 9 (31%) of 29 patients who underwent open surgery (P = .98). Systemic complications and complications necessitating surgical intervention during the initial hospital stay were similar in both treatment groups (8/26 [31%] and 5/26 [19%] for endovascular repair, respectively, and 9/29 [31%] and 8/29 [28%] for open surgery, respectively; P > .40). During 1-year follow-up, two patients initially treated with endovascular repair died as a result of non-aneurysm-related causes; no death occurred in the open surgery group. Complications during 1-year follow-up were 1 (5%) of 20 for endovascular repair and 4 (16%) of 25 for open surgery (P = .36).

CONCLUSIONS

On the basis of our study with a highly selected population, the mortality and complication rates after endovascular repair may be similar compared with those after open surgery in patients treated for ruptured infrarenal AAAs.

Prospective comparison of POSSUM and P-POSSUM with clinical assessment of mortality following emergency surgery

BACKGROUND

Tools to accurately estimate the risk of death following emergency surgery are useful adjuncts to informed consent and clinical decisions. This prospective study compared the Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity (POSSUM) and Portsmouth POSSUM (P-POSSUM) scoring systems with clinical judgement in predicting mortality from emergency surgery.

METHODS

Data were collected prospectively from 163 patients. Details of the physiological and operative severity scores were recorded for POSSUM and P-POSSUM. The estimates of both the surgeon and anaesthetist for 30-day and in-hospital mortality were also recorded pre-operatively. The accuracies of the four predictions were then compared with actual mortalities using linear and exponential analysis and receiver operator characteristics (ROC).

RESULTS

P-POSSUM gave the most accurate prediction of 30-day mortality using linear analysis [observed to expected ratio (O : E) = 1.0]. POSSUM gave the most accurate prediction using exponential analysis (O : E = 1.15). Clinical judgement of mortality from both operating surgeons and anaesthetists compared favourably with the scoring systems for 30-day mortality (O : E = 0.83 and O : E = 0.93, respectively). ROC analyses showed both clinical judgement and the POSSUM scores to be good predictors of 30-day mortality with area under the curve values (AUC) of 0.903, 0.907, 0.946 and 0.940 for surgeons, anaesthetists, POSSUM and P-POSSUM respectively.

CONCLUSIONS

POSSUM and P-POSSUM appear to be useful indicators for the prediction of mortality. Clinical judgement compares strongly with scoring systems in predicting post-operative mortality, but may underestimate mortality in very high-risk patients with more than 90% mortality.

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.

A comparison of POSSUM, P-POSSUM and colorectal POSSUM for the prediction of postoperative mortality in patients undergoing colorectal resection

PURPOSE

POSSUM (Physiologic and Operative Severity Score for enUmeration of Morbidity & Mortality) and P-POSSUM have been validated as scoring tools for the prediction of postoperative complications in general surgical patients. More recently a colorectal-specific POSSUM has been developed for mortality prediction. This study was designed to evaluate and compare the accuracy for mortality prediction of POSSUM, P-POSSUM, and colorectal POSSUM after major and complex major colorectal procedures.

METHODS

The relationship between the observed and expected morbidity and mortality was examined in 347 consecutive patients (321 elective, 26 urgent) undergoing a major or complex major colorectal resection using POSSUM, P-POSSUM, and Colorectal POSSUM. The accuracy of using these scoring tools to predict mortality was assessed using Receiver Operator Characteristic curve analysis.

RESULTS

A total of 347 consecutive patients (median age, 69 (range, 34-92) years) were assessed. Seventy-one patients (20.5 percent) suffered a postoperative complication and 15 patients (4.3 percent) died. The observed: expected POSSUM ratio for morbidity was 0.71 and mortality 0.68. The area under curve from Receiver Operator Characteristic curve analysis for POSSUM was 0.752. The observed:expected mortality ratio for P-POSSUM was 0.71, and the area under curve from Receiver Operator Characteristic curve analysis was 0.749. The observed:expected mortality ratio for colorectal POSSUM was 0.75, and the area under the curve from Receiver Operator Characteristic curve analysis was 0.781.

CONCLUSIONS

Colorectal POSSUM provides comparable prediction of mortality risk after colorectal resection compared with POSSUM and P-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.

Cost-effectiveness of endovascular abdominal aortic aneurysm repair

Background

The rapid introduction of endovascular abdominal aortic aneurysm repair (EVAR) has considerable implications for the management of abdominal aortic aneurysm (AAA). This study was undertaken to determine an optimal strategy for the use of EVAR based on the best currently available evidence.

Methods

Economic modelling and probabilistic sensitivity analysis considered reference cases representing a fit 70-year-old with a 5·5-cm diameter AAA (RC1) and an 80-year-old with a 6·5-cm AAA unfit for open surgery (RC2). Results were assessed as incremental cost-effectiveness ratio (ICER) compared with open repair (RC1) or conservative management (RC2).

Results

In RC1 EVAR produced a gain of 0·10 quality-adjusted life years (QALYs) for an estimated cost of £11 449, giving an ICER of £110 000 per QALY. EVAR consistently had an ICER above £30 000 per QALY over a range of sensitivity analyses and alternative scenarios. In RC2 EVAR produced an estimated benefit of 1·64 QALYs for an incremental cost of £14 077 giving an incremental cost per QALY of £8579.

Conclusion

It is unlikely that EVAR for fit patients suitable for open repair is within the commonly accepted range of cost-effectiveness for a new technology. For those unfit for conventional open repair it is likely to be a cost-effective alternative to non-operative management. Sensitivity analysis suggests that research efforts should concentrate on determining accurate rates for late complications and reintervention, particularly in patients with high operative risks.

Evaluation of P-POSSUM in surgery for obstructing colorectal cancer and correlation of the predicted mortality with different surgical options

PURPOSE

This study examined the accuracy of Portsmouth Physiologic and Operative Severity Score for enUmeration of Mortality and Morbidity system (P-POSSUM) in predicting the mortality of patients who underwent operations for obstructing colorectal cancer. It also is attempted to analyze the actual mortality and the predicted P-POSSUM mortality of different surgical options for obstructing left-sided cancer.

METHODS

Data on patients who underwent surgery for obstructing colorectal cancer during 1998 to 2002 were collected. Mortality predicted by P-POSSUM was compared to the actual mortality with the method of linear analysis. The accuracy of using P-POSSUM to predict mortality in this group of patients was assessed by Hosmer and Lemeshow goodness of fit test and Receiver Operator Characteristic curve analysis. The predicted and actual mortality of patients who underwent different surgical options also were analyzed.

RESULTS

A total of 160 patients were included in the study and 18 patients died postoperatively. The operative mortality was 11.3 percent. P-POSSUM predicted overall mortality of 15 percent. The observed and predicted mortality was found to have no significant lack of fit (chi-squared = 5.98; degree of freedom = 3; P = 0.11). The area under Receiver Operator Characteristic curve analysis was 0.75. For patients with left-sided tumors, P-POSSUM predicted mortality and actual mortality of patients who had resection without anastomosis were both significantly higher than patients with single-stage resection and primary anastomosis (P = 0.044 and 0.011, respectively).

CONCLUSIONS

P-POSSUM system is valid for prediction of overall mortality in patients with operations for obstructing colorectal cancer. Estimation of P-POSSUM predicted mortality during operation and its ability to correlate with choice of procedure is an area that is worth further study in emergency colorectal surgery.

Risk-Adjusted Analysis of Outcomes Following Elective Open Abdominal Aortic Aneurysm Repair

The purpose of this study was to describe a method to analyze outcomes following open abdominal aortic aneurysm (AAA) repair while considering the variability in patients' preoperative risk. Consecutive patients undergoing elective open infrarenal AAA repair during a 4-year period (2000-2003) were reviewed. Thirty-day or in-hospital mortality was the major outcome variable. Preoperative mortality risk was estimated for each patient using a validated scoring system that considers age, renal dysfunction, and coronary artery and cerebrovascular disease. A risk-adjusted cumulative sum method was used to compare observed versus predicted outcomes by assigning a risk-adjusted score, based on log-likelihood ratios, to each patient. These cumulative scores were sequentially plotted with preset control limits to allow for "signaling" when results were substantially different than expected (doubling or halving of odds ratios). Four hundred and sixty-three patients were studied with an overall early mortality rate of 4.5% (n = 21). Patients were allocated to three different preoperative risk groups (low, n = 89; medium, n = 160; high, n = 214) according to a medical comorbidity-based scoring system. Predicted (P) and observed (O) mortality rates for each group were as follows: low, 2.4% (P) and 2.2% (O); medium, 4.1% (P) and 4.4% (O); high, 9.3% (P) and 5.6% (O). The resulting risk-adjusted scores for each patient were plotted sequentially. This plot was flat for the first year and then adopted a negative slope crossing the lower control limit after 266 patients, indicating improved results compared to those expected. This coincided with the adoption of routine intraoperative cell saver use in our practice. This form of analysis allows for the prospective evaluation of results while considering patient-mix variabilities.

A new and feasible model for predicting operative risk

BACKGROUND

Although the POSSUM (Physiological and Operative Severity Score for the enumeration of Mortality and Morbidity) score can be used to calculate operative risk, its complexity makes its use unfeasible in the immediate clinical setting. The aim of this study was to create a new model, based on ASA status, to predict mortality.

METHODS

Data were collected in two hospitals. All types of surgery were included except for cardiac surgery and Caesarean delivery. Age, sex and preoperative information, including the presence of cardiocirculatory and/or lung disease, renal failure, diabetes mellitus, hepatic disease, cancer, Glasgow Coma Score, ASA grade, surgical diagnosis, severity of the procedure and type of surgery (elective, urgent or emergency), were recorded for each patient. The model was developed using a data set incorporating data from 1936 surgical patients, and validated using data from a further 1849 patients. Forward stepwise logistic regression was used to build the model. Goodness of fit was examined using the Hosmer-Lemeshow test and receiver operating characteristic (ROC) curve analyses were performed on both data sets to test calibration and discrimination. In the validation data set, the new model was compared with POSSUM and P-POSSUM for both calibration and discrimination, and with ASA alone to compare discrimination.

RESULTS

The following variables were included in the new model: ASA status, age, type of surgery (elective, urgent, emergency) and degree of surgery (minor, moderate or major). Calibration and discrimination of the new model were good in both development and validation data sets. This new model was better calibrated in the validation data set (Hosmer-Lemeshow goodness-of-fit test: chi(2)=6.8017, P=0.7440) than either P-POSSUM (chi(2)=14.4643, P=0.1528) or POSSUM, which was not calibrated (chi(2)=31.8147, P=0.0004). POSSUM and P-POSSUM had better discrimination than the new model, although this was not statistically significant. Comparing the two ROC curves, the new model had better discrimination than ASA alone (difference between areas, 0.077, SE 0.034, 95% confidence interval 0.012-0.143, P=0.021).

CONCLUSIONS

This new, ASA status-based model is simple to use and can be performed routinely in the operating room to predict operative risk for both elective and emergency surgery.