Hidden blood loss and its influential factors after total hip arthroplasty.

Background: Total hip arthroplasty (THA) is a vital therapy for various hip joint diseases. However, patients have lower hemoglobin level post-operatively, remarkably inconsistent with the measured blood loss. The inconsistence is majorly attributed to hidden blood loss (HBL). In this study, we investigated the HBL and its influential factors among patients after THA.

Methods: From January 2008 to June 2014, 322 patients (99 males and 223 females) undergoing THA were enrolled in this study. All patients were assessed comprehensively before the operation. The demographic information of the patients was collected. Intra-operative and post-operative blood loss was recorded, and then, the total perioperative blood loss and the HBL were calculated. Influential factors were further analyzed by multiple and stepwise regression.

Results: The HBL was 429 ± 223 mL, with a percentage of 35.4% ± 11.0% in the total perioperative blood loss (1,155 ± 377 mL). Multiple and stepwise regression analysis revealed that HBL was positively associated with body mass index (BMI), blood transfusion volume, length of incision, change of hematocrit (HCT) between pre-operation and post-operation but negatively associated with age. As compared to male patients, female patients had a risk of increased HBL. Development displasia hip (DDH) patients had a less risk of HBL in all patients.

Conclusion: HBL is a significant portion of total blood loss in the patients after THA. Gender, age, BMI, blood transfusion, length of incision, change of HCT, and diagnosis are influential factors of HBL.