How Much Blood Loss Is Appropriate for a 2- to 3-Level Posterior Lumbar Fusion?

BACKGROUND

Despite the known association between higher estimated blood loss (EBL) and suboptimal outcomes, the threshold of EBL that negatively impacts outcomes following elective spine surgery remains unknown. In an open 2- and 3-level posterolateral lumbar fusion, we sought to find a threshold of surgeon-reported EBL associated with length of stay (LOS), 30-day complications, and patient-reported outcomes (PROs).

METHODS

A single-center, retrospective cohort study was performed for 2- and 3-level open posterolateral lumbar fusions between October 2010 and April 2021. Surgeon-reported EBL (milliliters) was the primary independent variable for predicting LOS (days). Secondary outcomes included 30-day complications and PROs as the minimal clinically important difference (MCID). Multivariable regression and receiver operating characteristic curve with Youden's Index were calculated.

RESULTS

A total of 557 patients underwent 2-level fusions. Multivariable regression found EBL to be a significant risk factor for prolonged LOS. A threshold of 375 mL was associated with LOS beyond postoperative day 2 (POD2) (area under the curve [AUC] = 0.64, 95% CI 0.58-0.70, < 0.001). A total of 287 patients underwent 3-level fusions. Similarly, EBL was a significant risk factor for prolonged LOS, with a threshold of 675 mL to predict LOS beyond POD2 (AUC = 0.63, 95% CI 0.54-0.73, = 0.012). EBL was associated with increased odds of 30-day complications, with a threshold of 538 mL (AUC = 0.63, 95% CI 0.51-0.76, < 0.001). For both 2- and 3-level fusions, EBL was not significantly associated with MCID for any of the PROs.

CONCLUSIONS

In patients undergoing open, posterolateral lumbar fusions, surgeon-reported EBL thresholds at 375 mL for 2-level fusions and 675 mL for 3-level fusions were moderately associated with LOS beyond POD2. In 3-level lumbar fusions, EBL above 538 mL showed a potential association with an increased odds of 30-day complications.

CLINICAL RELEVANCE

Surgeons should improve their ability to manage blood loss and implement methods to keep EBL below the provided thresholds to decrease LOS and minimize the risk of complications.