Introduction:

Hypoalbuminemia as a risk factor for mortality following spine surgery has primarily focused on cohorts with spinal metastatic cancer. Low serum albumin is a known marker of inflammation, often associated with poor nutritional status and frailty. We assess the association between pre-operative hypoalbuminemia and mortality among a generalizable population of patients undergoing surgery for any indication, and to determine its association with post-operative patient-reported outcomes and readmission.

Methods:

An Electronic Medical Record (EMR) query identified all patients with pre-operative plasma albumin lab values who underwent Orthopedic spine surgery at a US public university health system between 2014 and 2021. Demographic, comorbidity, and mortality data were collected along with pre- and post-operative Oswestry Disability Index (ODI). All cause hospital readmission within one year of surgery was also identified. Hypoalbuminemia was based on a well-established clinical threshold of ≤3.5 g/dl. We initially examined Kaplan-Meier survival plot by albumin status. Subsequent multivariable regression models were used to identify the association between pre-operative hypoalbuminemia with mortality, readmission and ODI, while controlling for age, sex, race, ethnicity, and the Charlson Comorbidity Index (CCI).

Results:

Of 3425 spine surgery patients with pre-operative serum albumin lab values, 220 were identified as hypoalbuminemic (4.9%). Mean age was not significantly different between groups; mean age of all participants was 59.6 years old.  Sex was not significantly different between groups with 6.0% of all males classified as hypoalbuminemic and 4.5% of all females. The unadjusted mortality rate was 1.8% at 1 year and 5.6% through 7 years. Relative to patients with normal preoperative albumin, those with hypoalbuminemia had a significantly greater adjusted risk of mortality by 1-year (OR 11.24; 95%CI 6.47 – 19.52; p<0.001) and through 7 years (HR 4.27; 95%CI 3.06 – 5.94; p < 0.001). Average pre-operative ODI scores were 5.5 points higher among hypoalbuminemia patients (5.5 points; 95%CI 0.14 – 10.9; p=0.044) compared to patients with normal albumin levels but showed similar rates of improvement through 12 months postoperative.

Discussion:

Pre-operative hypoalbuminemia was strongly associated with post-operative mortality among a general spine surgery cohort. Patients with hypoalbuminemia showed a similar rate of post-operative disability improvement and a slightly lower rate of all-cause readmission. However, causal inference is limited in this retrospective study. Additional research should seek to clarify the role of serum albumin as an independent risk factor of mortality follow all types of spine surgery, and to better elucidate the role of hypoalbuminemia in the selection and management of spine surgery patients.