P34. Increasing patient complexity is associated with longer in hospital lengths of stay and higher rates of medical complications following primary 1- to 2-level lumbar fusion

Abstract

<h3>BACKGROUND CONTEXT</h3> Lumbar fusion (LF) procedures are being performed at a higher rate and on an older patient population than ever before. The increasing age of patients undergoing LF is accompanied by increasing complexity and comorbidity burden. The Elixhauser Comorbidity Index (ECI) is a well-established stratification tool to predict adverse surgical outcomes. The ECI, developed in 1998, consists of 30 comorbidity measures associated with increased length of stay (LOS), hospital charges, and perioperative complications. Currently, no studies have explored the relationship between ECI and outcomes following primary 1- to 2-level lumbar fusion (1-2LF). <h3>PURPOSE</h3> The purpose of this study is to determine whether higher patient complexity, determined by an ECI score of 2 to 5, is associated with worse outcomes compared to less complex patients with an ECI score of 1 following 1-2LF. Specifically, this retrospective study compared: 1) in-hospital LOS and 2) rates of 90-day medical complications. <h3>STUDY DESIGN/SETTING</h3> A retrospective review from January 1st, 2005, to March 31st, 2014, was performed using an administrative claims nationwide database. Specifically, we used the Medicare Standard Analytical Files for patients undergoing primary lumbar fusion. <h3>PATIENT SAMPLE</h3> Patients undergoing primary lumbar fusion were identified using ICD-9 procedural codes 81.04 to 81.08. From this cohort, patients who underwent 1- to 2- levels of fusion were identified using procedural code 81.62. Patients who underwent LF for traumatic injuries, infections or malignancies were excluded. Patients with an ECI score of 1 to 5 were filtered using 1-point increments. As such a total of five different cohorts were formed with patients having an ECI score of 1 being the comparison cohort, and patients with higher scores being the study cohorts. <h3>OUTCOME MEASURES</h3> Primary endpoints of this study were to compare in-hospital LOS and 90-day medical complications between the study cohorts and comparison cohort. Ninety-day medical complications analyzed included: acute kidney injuries, cerebrovascular accidents, deep vein thromboses, ileus episodes, myocardial infarctions, pneumoniae, pulmonary emboli, respiratory failure, transfusion of blood products, urinary tract infections and venous thromboemboli. <h3>METHODS</h3> Each study group was individually matched in a 1:1 ratio by age and sex to the ECI 1 cohort. After the matching process there were a total of 105,120 patients (female = 56,216; male = 48,232) equally distributed between the five cohorts. Baseline demographics of the individual cohorts was compared using Chi-square analyses or Fischer's exact test, when applicable. To determine the association of ECI on 90-day medical complications, logistic regression analyses were used to calculate the odds-ratios (OR) and 95% confidence intervals (95% CI) on the individual complications. Due to the ease of finding statistical significance in large database registries, a Bonferroni-correction was performed to reduce the probability of a type I error. As such, a p-value less than 0.001 was found to be statistically significant <h3>RESULTS</h3> A total of 105,120 patients were equally distributed between the 5 cohorts. Patients with an ECI score of 2 (6.00 ± 4.51), ECI 3 (6.22 ± 4.67), ECI 4 (7.35 ± 5.05), or ECI 5 (8.99 ± 5.67) had longer in-hospital LOS compared to patients with an ECI score of 1 (4.28 + 4.36) (all p < .001) . Patients with an ECI score of 2 (OR: 1.17, 95%CI: 1.05 - 1.30, p = 0.003; 2.85% vs 2.45%), ECI 3 (OR: 1.22, 95%CI: 1.10 - 1.36, p < 0.001; 2.98% vs 2.45%), ECI 4 (OR: 1.26, 95%CI: 1.13 - 1.40, p < 0.001; 3.10% vs 2.45%), or ECI 5 (OR: 1.18, 95%CI: 1.06 - 1.31, p = 0.001; 2.89% vs 2.45%) had greater incidence and odds of 90-day medical complications including pneumonia, deep vein thrombosis, cerebrovascular accidents, and myocardial infarctions than controls (all p < 0.0001). <h3>CONCLUSIONS</h3> As the volume of LF procedures performed and patient complexity increase, it is important for providers to understand the relationship between comorbidities and perioperative outcomes so they may appropriately adjust patients' pre- and postoperative care. Our study is the first to establish an association between increasing ECI scores with longer LOS and higher 90-day complication rates following 1-2LF. Future research should focus on identifying specific comorbidities that have the largest effect on patient outcomes and determine which modifications to pre- and postoperative care can lower complication rates in complex patients. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.