Hypoalbuminemia as a Predictor of Mortality, Disability, and Readmission in Patients Undergoing Spine Surgery: A Retrospective Analysis

Study Design. This was a retrospective cohort study. Objective. The objective of this study was to clarify the association between preoperative albumin status and mortality and morbidity in lumbar spine surgery. Summary of Background Data. Hypoalbuminemia is a known marker of inflammation and is associated with frailty. Hypoalbuminemia is an identified risk factor for mortality following spine surgery for metastases, yet has not been well studied among spine surgical cohorts outside of metastatic cancer. Materials and Methods. We identified patients with preoperative serum albumin laboratory values who underwent lumbar spine surgery at a US public university health system between 2014 and 2021. Demographic, comorbidity, and mortality data were collected along with preoperative and postoperative Oswestry Disability Index (ODI) scores. Any cause readmission within 1 year of surgery was recorded. Hypoalbuminemia was defined as <3.5 g/dL in serum. We examined the Kaplan-Meier survival plots based on serum albumin. Multivariable regression models were used to identify the association between preoperative hypoalbuminemia with mortality, readmission, and ODI, while controlling for age, sex, race, ethnicity, procedure, and Charlson Comorbidity Index. Results. Of 2573 patients, 79 were identified as hypoalbuminemic. Hypoalbuminemic patients had a significantly greater adjusted risk of mortality through 1 year (odds ratio=10.2; 95% CI: 3.1-33.5; P<0.001), and 7 years (hazard ratio=4.18; 95% CI: 2.29-7.65; P<0.001). Hypoalbuminemic patients had ODI scores 13.5 points higher (95% CI: 5.7-21.4; P<0.001) at baseline. Adjusted readmission rates were not different between groups through 1 year (odds ratio=1.15; 95% CI: 0.5-2.62; P=0.75) or through full surveillance (hazard ratio=0.82; 95% CI: 0.44-1.54; P=0.54). Conclusions. Preoperative hypoalbuminemia was strongly associated with postoperative mortality. Hypoalbuminemic patients did not have demonstrably worse outcomes in their functional disability beyond 6 months. Within the first 6 months following surgery, the hypoalbuminemic group improved at a similar rate to the normoalbuminemic group despite having a greater preoperative disability. However, causal inference is limited in this retrospective study.