Evaluating parsimonious risk-adjustment models for comparing hospital outcomes with vascular surgery

New anthropometric classification scheme of preoperative nutritional status in children: a retrospective observational cohort study

OBJECTIVE

WHO uses anthropometric classification scheme of childhood acute and chronic malnutrition based on low body mass index (BMI) ('wasting') and height for age ('stunting'), respectively. The goal of this study was to describe a novel two-axis nutritional classification scheme to (1) characterise nutritional profiles in children undergoing abdominal surgery and (2) characterise relationships between preoperative nutritional status and postoperative morbidity.

DESIGN

This was a retrospective observational cohort study.

SETTING

The setting was 50 hospitals caring for children in North America that participated in the American College of Surgeons National Surgical Quality Improvement Program Paediatric from 2011 to 2013.

PARTICIPANTS

Children >28 days who underwent major abdominal operations were identified.

INTERVENTIONS/MAIN PREDICTOR

The cohort of children was divided into five nutritional profile groups based on both BMI and height for age Z-scores: (1) underweight/short, (2) underweight/tall, (3) overweight/short, (4) overweight/tall and (5) non-outliers (controls).

MAIN OUTCOME MEASURES

Multiple variable logistic regressions were used to quantify the association between 30-day morbidity and nutritional profile groups while adjusting for procedure case mix, age and American Society of Anaesthesiologists class.

RESULTS

A total of 39 520 cases distributed as follows: underweight/short (656, 2.2%); underweight/tall (252, 0.8%); overweight/short (733, 2.4%) and overweight/tall (1534, 5.1%). Regression analyses revealed increased adjusted odds of composite morbidity (35%) and reintervention events (75%) in the underweight/short group, while overweight/short patients had increased adjusted odds of composite morbidity and healthcare-associated infections (43%), and reintervention events (79%) compared with controls.

CONCLUSION

Stratification of preoperative nutritional status using a scheme incorporating both BMI and height for age is feasible. Further research is needed to validate this nutritional risk classification scheme for other surgical procedures in children.

Estimating Adverse Events After Gastrostomy Tube Placement

OBJECTIVE

Gastrostomy feeding tube placement in children is associated with a high frequency of adverse events. This study sought to preoperatively estimate postoperative adverse events in children undergoing gastrostomy feeding tube placement.

METHODS

This was an observational study of children who underwent gastrostomy with or without fundoplication at 1 of 50 participating hospitals, using 2011-2013 data from the American College of Surgeons' National Surgical Quality Improvement Program Pediatric. The outcome was the occurrence of any postoperative complications or mortality at 30 days after gastrostomy tube placement. The preoperative clinical characteristics significantly associated with occurrence of adverse events were included in a multivariate logistic model. The area under the receiver operating characteristic curve was computed to assess model performance and split-set validated.

RESULTS

A total of 2817 children were identified as having undergone gastrostomy tube placement. The unadjusted rate of adverse events within 30 days after gastrostomy tube placement was 11%. Thirteen predictor variables were identified. Notable preoperative variables associated with a greater than 75% increase in adverse event rate were preoperative sepsis/septic shock (odds ratio [OR], 10.76, 95% confidence interval [CI], 3.84-30.17), central nervous system tumor (OR, 3.36; 95% CI, 1.42-7.95), the primary procedure as indicated by the current procedural terminology (CPT) linear risk variable (OR, 1.93; 95% CI, 1.50-2.49), severe cardiac risk factors (OR, 1.88; 95% CI, 1.17-3.03), and preoperative seizure history (OR, 1.90; 95% CI, 1.38-2.62). The area under the receiver operating characteristic curve was 0.71 with the derivation data set and 0.71 upon split-set validation.

CONCLUSIONS

Preoperatively estimating postoperative adverse events in children undergoing gastrostomy tube placement is feasible.

A validated risk model to predict 90-day VTE events in postsurgical patients

BACKGROUND

VTE is the proximate cause of 100,000 deaths in the United States each year. Perioperative VTE risk among surgical patients varies by 20-fold, which highlights the importance of risk stratification to identify high-risk patients, in whom chemoprophylaxis can decrease VTE risk, and low-risk patients, for whom the risk-benefit relationship of prophylaxis may be unfavorable.

METHODS

We used data from a statewide surgical quality collaborative for surgical procedures performed between 2010 and 2012. Regression-based techniques identified predictors of 90-day VTE while adjusting for procedural complexity and comorbid conditions. A weighted risk index was created and was validated subsequently in a separate, independent dataset.

RESULTS

Data were available for 10,344 patients, who were allocated randomly to a derivation or validation cohort. The 90-day VTE rate was 1.4%; 66.2% of the derivation cohort and 65.5% of the validation cohort received chemoprophylaxis. Seven risk factors were incorporated into a weighted risk index: personal history of VTE, current cancer, sepsis/septic shock/systemic inflammatory response syndrome, age≥60 years, BMI≥40 kg/m2, male sex, and family history of VTE. Prediction for 90-day VTE was similar in the derivation and validation cohorts (areas under the receiver operator curve, 0.72 and 0.70, respectively). An 18-fold variation in 90-day VTE rate was identified.

CONCLUSIONS

A weighted risk index quantifies 90-day VTE risk among surgical patients and identifies an 18-fold variation in VTE risk among the overall surgical population.

Derivation and validation of a practical risk score for prediction of mortality after open repair of ruptured abdominal aortic aneurysms in a US regional cohort and comparison to existing scoring systems

OBJECTIVE

Scoring systems for predicting mortality after repair of ruptured abdominal aortic aneurysms (RAAAs) have not been developed or tested in a United States population and may not be accurate in the endovascular era. Using prospectively collected data from the Vascular Study Group of New England (VSGNE), we developed a practical risk score for in-hospital mortality after open repair of RAAAs and compared its performance to that of the Glasgow aneurysm score, Hardman index, Vancouver score, and Edinburg ruptured aneurysm score.

METHODS

Univariate analysis followed by multivariable analysis of patient, prehospital, anatomic, and procedural characteristics identified significant predictors of in-hospital mortality. Integer points were derived from the odds ratio (OR) for mortality based on each independent predictor in order to generate a VSGNE RAAA risk score, which was internally validated using bootstrapping methodology. Discrimination and calibration of all models were assessed by calculating the area under the receiver-operating characteristic curve (C-statistic) and applying the Hosmer-Lemeshow test.

RESULTS

From 2003 to 2009, 242 patients underwent open repair of RAAAs at 10 centers. In-hospital mortality was 38% (n = 91). Independent predictors of mortality included age >76 years (OR, 5.3; 95% confidence interval [CI], 2.8-10.1), preoperative cardiac arrest (OR, 4.3; 95% CI, 1.6-12), loss of consciousness (OR, 2.6; 95% CI, 1.2-6), and suprarenal aortic clamp (OR, 2.4; 95% CI, 1.3-4.6). Patient stratification according to the VSGNE RAAA risk score (range, 0-6) accurately predicted mortality and identified those at low and high risk for death (8%, 25%, 37%, 60%, 80%, and 87% for scores of 0, 1, 2, 3, 4, and ≥5, respectively). Discrimination (C = .79) and calibration (χ(2) = 1.96; P = .85) were excellent in the derivation and bootstrap samples and superior to that of existing scoring systems. The Glasgow aneurysm score, Hardman index, Vancouver score, and Edinburg ruptured aneurysm score correlated with mortality in the VSGNE cohort but failed to identify accurately patients with a risk of mortality >65%.

CONCLUSIONS

Existing scoring systems predict mortality after RAAA repair in this cohort but do not identify patients at highest risk. This parsimonious VSGNE RAAA risk score based on four variables readily assessed at the time of presentation allows accurate prediction of in-hospital mortality after open repair of RAAAs, including identification of those patients at highest risk for postoperative mortality.