Correlation Between Postoperative Pain Intensity and Perioperative Blood Loss After Total Knee Arthroplasty

Postoperative pain following total knee arthroplasty (TKA) can exacerbate sympathetic activity, elevate blood pressure, and potentially increase blood loss. However, the relationship between these factors remains unclear. This study evaluates the correlation between postoperative pain intensity and perioperative blood loss.

A retrospective analysis was conducted on 405 unilateral TKAs, stratified by average visual analog scale (VAS) in the first 24 h postoperatively into mild (VAS 0-3), moderate (VAS > 3-6), and severe (VAS > 6-10) pain intensity groups. The primary outcomes were the effect of pain intensity on mean calculated blood loss (CBL) and risk of blood transfusion. Secondary outcomes included length of hospital stay (LHS) and complications. Multivariable regression analysis was employed.

Adjusted mean differences in CBL and LHS were not significantly different among the pain intensity groups. However, severe pain intensity was associated with a higher risk of blood transfusion (risk ratio: 1.92, p = 0.068). Preoperative hemoglobin (Hb) was the only protective factor against blood transfusion; each 1 g/dL increase in preoperative Hb reduced the blood transfusion risk by 61% (risk ratio: 0.39, p  <  0.001). Additionally, the severe pain intensity group had the highest incidence of overall complications (13.3%) observed during 180 days post-TKA (p  <  0.01).

Patients experiencing severe pain intensity in the first 24 h after TKA tend to have a higher risk for blood transfusion and a significantly higher risk of overall complications. Thus, optimizing pain control is important to enhance recovery for current clinical pathways of TKA.