Weldon J. Miller

Development and Validation of a Risk Calculator Predicting Postoperative Respiratory Failure

BACKGROUND Postoperative respiratory failure (PRF) (requiring mechanical ventilation > 48 h after surgery or unplanned intubation within 30 days of surgery) is associated with significant morbidity and mortality. The objective of this study was to identify preoperative factors associated with an increased risk of PRF and subsequently develop and validate a risk calculator. METHODS The American College of Surgeons National Surgical Quality Improvement Program (NSQIP), a multicenter, prospective data set (2007-2008), was used. The 2007 data set (n = 211,410) served as the training set and the 2008 data set (n = 257,385) as the validation set. RESULTS In the training set, 6,531 patients (3.1%) developed PRF. Patients who developed PRF had a significantly higher 30-day mortality (25.62% vs 0.98%, P < .0001). On multivariate logistic regression analysis, five preoperative predictors of PRF were identified: type of surgery, emergency case, dependent functional status, preoperative sepsis, and higher American Society of Anesthesiologists (ASA) class. The risk model based on the training data set was subsequently validated on the validation data set. The model performance was very similar between the training and the validation data sets (c-statistic, 0.894 and 0.897, respectively). The high c-statistics (area under the receiver operating characteristic curve) indicate excellent predictive performance. The risk model was used to develop an interactive risk calculator. CONCLUSIONS Preoperative variables associated with increased risk of PRF include type of surgery, emergency case, dependent functional status, sepsis, and higher ASA class. The validated risk calculator provides a risk estimate of PRF and is anticipated to aid in surgical decision making and informed patient consent.

Chronic Mesenteric Ischemia: Endovascular versus Open Revascularization

Purpose: To review 20 years of literature on chronic mesenteric ischemia (CMI), examining its complex clinical presentation and comparing open and endovascular treatment options. Methods: The PubMed and EBSCOHost electronic databases were queried to identify English-language articles published over the last 20 years. Scrutiny of the retrieved articles identified 1939 patients (mean age 65 years). Of these, 1163 patients underwent open surgery: 714 between 2000 and 2009 and 449 between 1990 and 1999. Of the 776 patients undergoing endovascular repairs, the majority (684) were performed between 2000 and 2009; 92 patients were treated between 1990 and 1999. Data were entered in an electronic database and were pooled for categorical analysis. Results: No major differences were seen among open surgeries or among endovascular surgeries performed when comparing the 2 time periods. On comparing open and endovascular surgeries performed between 2000 and 2009, symptom improvement was 2.4 times more likely after open compared to endovascular surgery (95% CI 1.5 to 3.6, p<0.001). Five-year primary patency and 5-year assisted primary patency were 3.8 (95% CI 2.4 to 5.8, p<0.001) and 6.4 (95% CI 1.3 to 30.1, p=0.02) times greater in the open group. Freedom from symptoms at 5 years was 4.4 times greater for open versus endovascular (95% CI 2.8 to 7.0, p<0.001). The complication rate for open versus endovascular surgery was 3.2 times greater (95% CI 2.5 to 4.2, p<0.001). The difference in mortality was not statistically significant (p=0.75). Conclusion: Our data demonstrate that open revascularization surpasses endovascular procedures in long-term vessel patency and control of symptoms. Patients undergoing open procedures do, however, develop increased complications perioperatively. The preferred revascularization approach used in treating this condition should be tailored to the anatomy and physiology of each patient.

Determinants of outcomes in pancreatic surgery and use of hospital resources

Outcomes for patients undergoing major pancreatic surgery have improved, but a subset of patients that significantly utilize more resources exists. Variables that can lead to an increase in resource utilization in patients undergoing pancreatic surgery were identified.

Response to Letter Regarding Article, “Development and Validation of a Risk Calculator for Prediction of Cardiac Risk After Surgery”

We thank Drs Lee and Goldman for their comments on our publication.1The doctors state that the ratio of postoperative cardiac arrest to myocardial infarction (MI) is 2.5:1 in our study in comparison with a ratio of 0.3:1 in their study.2 Based on this finding, they contend that cardiac arrests in our study should more appropriately be attributed to noncardiac causes, and thus the Revised Cardiac Risk Index (RCRI) more accurately estimates the risk of cardiac complications after surgery. It should be remembered that, among the patients in the dataset used to develop the RCRI (n=2893) in 1999, 56 (2%) patients developed a major cardiac complication. There were only 9 (0.3%) with cardiac arrest, 2 (0.1%) with complete heart block, 28 (1%) with …