Historically, blood transfusions have been a common occurrence after a total knee replacement surgery because of significant bleeding during surgery.
In modern times however doctors are taking steps before, during, and after surgery to prevent blood loss so that a transfusion isn’t needed.
What is done before surgery?
Our body is constantly making new blood cells to replace the ones that are getting old and tired (the average lifespan of a red blood cell is only 120 days). Our body releases a signal, the protein erythropoietin, when our red blood cells are running low and need to be refilled, and our bone marrow will start making more. EPO (short for erythropoietin) is an medication that can be given before surgery to stimulated your body to make new red blood cells. The medication is just a high dose of the protein thats made organically in your body. Its effect is to simulate new cells to be made by tricking your bone marrow into thinking there is blood loss before the surgery even occurs.
This drug, EPO, may sound familiar, and its probably because it is commonly abused by athletes, especially in the Tour de France, as a performance enhancing drug.
Certain vitamins like B12, folate, and iron are needed to produce red blood cells. Some doctors will check these levels before surgery, and provide supplements if levels are low. This way, when our body needs to ramp up production after bleeding from surgery, it has all the resources it needs to do a great job. Clinical studies looking at the use of these supplements before surgery have shown them to be somewhat helpful in people with anemia (low hemoglobin at baseline). However this method is not helpful in otherwise healthy people (normal hemoglobin before surgery). If fact, the side effects from taking these vitamins, especially iron tablets, which can cause constipation in up to 30% of people taking it, as well as GERD or abdominal pain, are not worth the benefits.
What is done during surgery?
Bleeding naturally occurs during every surgery as a scalpel (knife) is used to cut tissue. Another surgical device, called an Electrocautery (it looks like a pen) is used in almost every surgery to stop bleeding. This device minimizes bleeding by burning (cauterizing) the small veins and arteries that bleed after being cut. A tourniquet is also used in almost all knee replacement cases. A tourniquet is a very tight wrap around the thigh that prevents blood from getting to the site of surgery. A tourniquet has a big impact on minimizing blood loss during surgery.
Tranexamic Acid is an exciting medication that has just started to be used in total joint replacement cases over the last 2 or 3 years. The medication is given during surgery and it encourages our blood to coagulate (harden) so that bleeding stops. Our blood coagulates by forming “fibrin clots”, and this medication makes these fibrin clots stronger and more resistant to breaking apart. Many studies have shown a dramatic decline in blood transfusions after surgery due to the use of this medication. Its also important to note that this medication has not been shown to increase the risk for harmful blood clots (which is a concerning complication of total knee replacements).
Hemodilution is another technique used by orthopedic surgeons to minimize blood loss during a knee replacement. Hemodilution refers to the idea that you give lots and lots of IV fluids during surgery so that your hemoglobin (the most valuable part of your blood) is diluted within the blood.
So how do doctors decide when to transfuse?
Doctors look at the overall blood count by measuring your Hemoglobin concentration. This number is recorded before surgery, immediately after surgery, and for a few days after surgery to make sure that it stays within a relatively normal range. Everyone is different, and there is no number that is normal and abnormal. A healthy young person can do fine with a low hemoglobin, while an elderly person with heart disease will have more problems if their hemoglobin drops. Doctors use the hemoglobin number. Overall, transfusing people if their hemoglobin is above 8 g/dL has no effect on their risk for complications, even if people have a history of cardiac disease. Below 8, patients with cardiac disease or other medical conditions may benefit from transfusion, while younger healthier patients may do well even if their hemoglobin drops below 7. Its important to look for more information , like heart rate and blood pressure to see if someone is tolerating a lower hemoglobin. Generally all people should have a transfusion if their hemoglobin dips below 6
But why should we care about getting a transfusion?
Well for one thing, theres no free lunch in medicine…every treatment has its side effects. When getting a transfusion there is a risk that your body will have an allergic reaction to the foreign blood, and theres also risk of contracting a viral disease like HIV or Hepatitis (but remember that this risk is extremely low: like less than 1 in 1.5 million). Blood transfusions are also very expensive to the patient and the medical system. And lastly, if you need a blood transfusion it means your body is functioning at a suboptimal level and so its better to not let your body even reach that stage.