Preoperative Care Assessment of Need Scores Are Associated With Postoperative Mortality and Length of Stay in Veterans Undergoing Knee Replacement
Background: Care Assessment of Need (CAN) scores predicting 90-day mortality and hospitalization are automatically computed each week for patients receiving care at Veterans Health Administration facilities. While currently used only by primary care teams for care coordination, we explored their value as a perioperative risk stratification tool before major elective surgery.
Methods: We collected relevant demographic and perioperative data along with perioperative CAN scores for veterans who underwent total knee replacement between July 2014 and December 2015. We examined score distribution, relationships of preoperative CAN 1-year mortality scores with 1-year postoperative mortality and index hospital length of stay (LOS), and patterns of mortality.
Results: Among 8206 patients, 1-year mortality was 1.4% (110 patients), and CAN scores exhibited near-normal distribution. Median scores among survivors were significantly higher than those of in nonsurvivors (45 vs 75; P < .001). The Kaplan-Meier curves showed an approximately 4-fold higher rate of death at 1 year in the highest tercile for 1-year mortality CAN scores compared with those with lower scores (2.0% vs 0.5% respectively; P < .001). Locally estimated scatterplot smoothing curves revealed a significant and nonlinear increase in hospital LOS across preoperative CAN scores.
Conclusions: Although designed for ambulatory care use, CAN scores can identify patients at high risk for mortality and extended hospital LOS in an elective surgery population. The CAN scores may prove valuable in supporting informed decision making and preoperative planning in high-risk and vulnerable populations. Further study is needed to confirm the validity of CAN scores and compare them to other more widely used surgical risk calculators.
Limitations
Our study has several limitations. Only a single surgical procedure was included, albeit the most common one performed in the VHA. In addition, no information was available concerning the precise clinical course for these patients, such as the duration of surgery, anesthetic technique, and management of acute, perioperative course. Although the assumption was made that patients received standard care in a manner such that these factors would not significantly affect either their mortality or their LOS out of proportion to their preoperative clinical status, confounding cannot be excluded. Therefore, further study is necessary to determine whether CAN scores can accurately predict mortality and/or LOS for patients undergoing other procedures. Further, a clinical trial is required to assess whether systematic provision of the CAN score at the point of surgery would impact care and, more important, impact outcomes. In addition, multivariable analyses were not performed, including and excluding various components of the CAN score models. Currently, CAN scores could be made available to the surgical/anesthesia communities at minimal or no cost and are updated automatically. Model calibration and discrimination in this particular setting were not validated.
Because our interest is in leveraging an existing resource to a current clinical and operational problem rather than in creating or validating a new tool, we chose to test the simple bivariate relationship between preoperative CAN scores and outcomes. We chose the preoperative 1-year mortality CAN score from among the 4 options under the assumption that long-term survival is the most meaningful of the 4 candidate outcomes. Finally, while the CAN scores are currently only calculated and generated for patients cared for within the VHA, few data elements are unavailable to civilian health systems. The most problematic would be documentation of actual prescription filling, but this is a topic of increasing interest to the medical and academic communities and access to such information we hope will improve.32-34
Conclusions
Although designed for use by VHA primary care teams, CAN scores also may have value for perioperative clinicians, predicting mortality and prolonged hospital LOS in those with elevated 1-year mortality scores. Advantages of CAN scores relative to other perioperative risk calculators lies in their ability to predict long-term rather than 30-day survival and that they are automatically generated on a near-real-time basis for all patients who receive care in VHA ambulatory clinics. Further study is needed to determine practical utility in shared decision making, preoperative evaluation and optimization, and perioperative resource allocation.
Acknowledgments
This work was supported by the US Department of Veterans Affairs (VA) National Center for Patient Safety, Field Office 10A4E, through the Patient Safety Center of Inquiry at the Durham VA Medical Center in North Carolina. The study also received support from the Center of Innovation to Accelerate Discovery and Practice Transformation (CIN 13-410) at the Durham VA Health Care System.
