Low Red Blood Cells, Clotting Factor Levels Tied to Surgery Bleeding Risk

Teresa Carvalho MSc avatar

by Teresa Carvalho MSc |

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Hemophilia patients with a low number of red blood cells and reduced coagulation factor levels — the activity level of proteins essential for blood clotting — are at a higher risk of increased blood loss during a knee replacement surgery, a study reported.

The study, “Risk factors for increased perioperative blood loss during total knee arthroplasty in patients with hemophilia,” was published in Haemophilia.

Researchers called the study the “first to investigate independent risk factors, including coagulation factor levels, for increased [perioperative blood loss].”

One of the symptoms of hemophilia is bleeding into a joint, or hemarthrosis. This can result in hemophilic arthropathy, a form of joint disease associated with hemophilia that may lead to disability.

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In severe cases, patients may need to undergo knee replacement surgery, also known as total knee arthroplasty (TKA), to reduce pain and improve knee function.

Despite using clotting factors during and after surgery to decrease blood loss, hemophilia patients have higher blood loss during the procedure compared with those without hemophilia.

According to researchers, blood management “is an important issue in TKA, especially in patients with hemophilia. During the perioperative period [around the time of surgery] in TKA, blood management is essential because it can affect the postoperative clinical outcome.”

But what risk factors might contribute to increased blood loss during TKA has not been studied, and no studies have assessed coagulation factor levels before and after surgery.

Researchers analyzed data from 92 surgeries to identify potential risk factors associated with increased blood loss, including coagulation factor level, in a population of patients with hemophilia A and B.

After calculating the volume of blood lost during surgeries (mean of 542.3 mL), researchers divided patients into two groups: group H included 36 patients whose blood loss was higher than the mean (895.2 mL); and group L included 56 patients whose blood loss was lower than the mean value (306.9 mL).

Patients were given an injection with clotting factor VIII, the one missing in hemophilia A, and clotting factor IX, which is missing in hemophilia B. Clotting factors were injected before and after surgery.

Blood levels of hemoglobin, red blood cells, and coagulation factors were evaluated before and during surgery. Hemoglobin is the protein in red blood cells that is responsible for oxygen transport.

Blood coagulation tests, such as activated partial thromboplastin time (aPTT) and prothrombin time/international normalized ratio (PT INR) values, were performed to assess how long it takes for a clot to form.

Patients in group H had a lower body mass index (BMI), a measure of body fat, than those in group L (21.5 kg/m2 vs. 23.2 kg/m2). During surgery, coagulation factor levels were also significantly lower in patients with higher blood loss (79.1%) compared with those in the lower blood loss group (about 100%).

Hemoglobin levels and the proportion of red blood cells also were significantly lower in patients with higher blood loss during surgery (12 g/dL and 35.2%, respectively) compared with the other group (14.2 g/dL and 41.4%, respectively).

These results showed that the amount of red blood cells and coagulation factor levels were risk factors for an increased blood loss during TKA.

The team also found an optimal cutoff value for the coagulation factor level (93.5%), and for the amount of red blood cells (38.2%) on the day of the surgery. This means that patients with values below these percentages on the day of surgery were at higher risk for increased blood loss.