Background: Deliberate hypotension under spinal or epidural anesthesia is a readily available and effective method to reduce intraoperative blood loss in total hip arthroplasty. However, induced hypotension has been shown to alter the physiologic handling of crystalloid solutions, with blood volume increasing in proportion to the drop in blood pressure. This study aims to investigate the effect of hemodilution secondary to hypotensive anesthesia and volume loading on postoperative hemoglobin levels.
Methods: 211 non-anemic adult patients who underwent primary total hip arthroplasty utilizing a minimal invasive posterior approach with hypotensive spinal-epidural anesthesia were evaluated retrospectively. The effect of fluid loading under hypotensive anesthesia was investigated by calculating the blood loss that corresponds to patients’ preoperative and postoperative hemoglobin levels, as well as calculating the hemoglobin levels expected for known volumes of blood loss.
Results: There was a large discrepancy between the calculated blood loss (1358 mL) and the actual measured blood loss (212 mL). Patients received an average of 4488 (SD 1209) mL of intravenous fluid within 24 hours of surgery. There was also a large difference between the calculated hemoglobin level based on the measured blood loss (13.6 g/dL) and the actual measured mean hemoglobin (10.8 g/dL).
Conclusion: Blood volume expansion and hemodilution with hypotensive epidural anesthesia leads to decreased hemoglobin levels in the early postoperative period and likely impacts on transfusion requirements. Hypotensive anesthesia might have a detrimental effect on transfusion requirements in procedures with relatively low blood loss.