Hypotensive anesthesia may result in false anemia and increase transfusion requirements in total hip arthroplasty

Background: Deliberate hypotension under spinal or epidural anesthesia is a readily available and effectivemethod to reduce intraoperative blood loss in total hip arthroplasty. However, induced hypotension has been shownto alter the physiologic handling of crystalloid solutions, with blood volume increasing in proportion to the drop inblood pressure. This study aims to investigate the effect of hemodilution secondary to hypotensive anesthesia andvolume loading on postoperative hemoglobin levels.

Methods: 211 non-anemic adult patients who underwent primary total hip arthroplasty utilizing a minimalinvasive posterior approach with hypotensive spinal-epidural anesthesia were evaluated retrospectively. The effectof fluid loading under hypotensive anesthesia was investigated by calculating the blood loss that corresponds topatients’ preoperative and postoperative hemoglobin levels, as well as calculating the hemoglobin levels expectedfor known volumes of blood loss.

Results: There was a large discrepancy between the calculated blood loss (1358 mL) and the actual measuredblood loss (212 mL). Patients received an average of 4488 (SD 1209) mL of intravenous fluid within 24 hours ofsurgery. There was also a large difference between the calculated hemoglobin level based on the measured bloodloss (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 decreasedhemoglobin levels in the early postoperative period and likely impacts on transfusion requirements. Hypotensiveanesthesia might have a detrimental effect on transfusion requirements in procedures with relatively low blood loss.