Association of preoperative hemoglobin levels with intraoperative hypotension: a retrospective cohort study

Intraoperative hypotension (IOH) has been increasingly linked to postoperative complications and adverse outcomes. Nevertheless, the association between preoperative hemoglobin levels and the risk of IOH has not been investigated.

We conducted a retrospective cohort study of 2,060 patients aged ≥ 18 yr who underwent general anesthesia between 2019 and 2023. We defined intraoperative hypotension as any mean blood pressure (MBP) < 65, 60, 55, 50, or 45 mm Hg, based on 5-min interval recordings. We assessed the association between preoperative hemoglobin levels and IOH using multivariable logistic regression with restricted cubic spline modeling. We also evaluated the association between preoperative hemoglobin levels and postoperative length of hospital stay using a generalized additive model.

We found no significant association between preoperative hemoglobin levels and IOH risk at MBP < 65 and < 45 mm Hg (P = 0.13 and 0.12, respectively). Nevertheless, at MBP < 60 mm Hg, patients with lower preoperative hemoglobin levels had a significantly higher risk of IOH (P = 0.03). We observed similar trends at more severe hypotension thresholds (< 55 mm Hg and < 50 mm Hg), with P values of 0.02 and 0.03, respectively. Lower hemoglobin levels were associated with more frequent IOH episodes and higher odds ratios. We also found a significant association between lower preoperative hemoglobin levels and a longer postoperative length of hospital stay.

Lower preoperative hemoglobin levels were significantly associated with an increased risk of IOH and longer postoperative length of hospital stay. These findings highlight the potential value of incorporating hemoglobin level assessments into IOH risk stratification and may help improve patient outcomes.