An economic evaluation of perioperative adverse events associated with spinal surgery

Besides their clinical impact, the economic impact of health care-related adverse events (AEs) is significant. Although a number of studies have attempted to estimate the economic impact of AEs, few have directly linked costs to clinician-reported event severity.

To estimate the economic impact in terms of the incremental cost and length of stay (LOS), attributable to different severity grades of AEs that occurred during perioperative spinal surgery.

Health economic evaluation of data from a prospective observational study from the perspective of an academic hospital.

Consecutive patients at a single, tertiary-quaternary care institution who have undergone inpatient spinal surgery.

The cost and LOS impacts with respect to the severity of the AEs.

We analyzed 4 years of patient discharges between January 1, 2007 and December 31, 2010. The Spine Adverse Events Severity instrument was completed by the surgical team at discharge. Clinical impacts of the AEs were graded as I (requires no/minimal treatment), II (requires treatment and is not likely to cause long-term [>6 months] sequelae), III (requires treatment and is most likely to cause long-term sequelae), and IV (death). A total of 1,815 records were linked with the patient-level costing information. We matched each AE case with four control cases based on their propensity score for the risk of experiencing an AE, regressed against case characteristics. We estimated an incremental cost and LOS for each severity grade by calculating the differences in means across cases and controls. We conducted a sensitivity analysis by estimating the alternate models using generalized linear model (GLM) regression with a gamma log link.

Adverse events were reported in 316 (17.4%) cases, with 126 of these patients (40.2%) experiencing multiple events. The incremental cost/LOS for each severity grade are as follows: I=$4,224 (p=.0351)/3.63 days (p=.0001); II=$23,500 (p<.0001)/14.03 days (p<.0001); III=$147,285 (p=.0036)/74.50 days (p=.0018); and IV=$121,366 (p=.0323)/46.44 days (p=.0036). The total cost in millions/LOS (days) associated with each grade over the 4-year study period are as follows: I=$0.66 million/569.9 days; II=$2.96 million/1,767.8 days; III=$4.27 million/2,160.5 days; and IV=$0.49 million/185.8 days. Our sensitivity analysis produced comparable overall results using alternate modeling techniques. Overall, AEs contributed an estimated $8.38 million (16.0% of the total costs for all patients in the sample) in incremental costs and 4,684 additional bed days over the 4-year study period.

In this surgical spine cohort, AEs accounted for 16% of the total cost of in-hospital care. Higher severity AEs were progressively more costly on a per-case basis; however, the more frequent lower severity events (ie, Grade I and II) also had a substantial aggregate cost (43%). These results suggest that a strong business case exists for patient safety strategies focused not only on severe AEs but also on the reduction of lower severity events that may be more amenable to prevention efforts.