Why Do Liver Transplants Require So Much Blood?

Liver transplants. A person's second chance at life. A truly amazing feat of medicine. And an occasional bane for Blood Bankers. Even the smoothest of surgeries generally take SOME blood. Over the last few decades blood usage has decreased dramatically overall due  to better techniques and advances in medicine, but the risk of bleeding still exists. Why?

The liver. Can't live without it!

Liver Transplant Bleeding

High Vascularity: The liver is one of the most blood-rich organs in the body, containing about 10% of the body’s blood supply at any given time.The liver's substantial blood volume, sourced from both the hepatic artery and the portal vein, underscores its high vascularity, elevating the complexity and potential bloodiness of liver-related surgical procedures. This dual blood supply system not only highlights the liver's critical role in bodily functions but also signifies the importance of meticulous surgical precision during liver transplants to manage and minimize blood loss effectively.

Complex Vascular Structures: The liver's vascular architecture, including major vessels entering and leaving the liver, makes surgical intervention complex. Precisely connecting these vessels during a transplant is critical to ensure the liver's blood supply in the recipient, and this process can lead to significant blood loss.

Disease State: Many patients requiring a liver transplant have underlying liver diseases such as cirrhosis, which can lead to altered blood clotting mechanisms and increased risk of bleeding. Moreover, liver disease often causes splenomegaly (enlarged spleen), which further complicates the surgery and increases the risk of bleeding.

Technical Challenges: The surgery involves removing the diseased liver and replacing it with a healthy one, connecting the blood vessels and bile ducts precisely to ensure the new liver functions properly. This process is technically challenging and can be associated with significant blood loss, especially in cases where there are anatomical variations or complications.

Advancements in surgical techniques, better understanding of liver anatomy, and improvements in preoperative planning and postoperative care have helped reduce the blood loss associated with liver transplants over the years. This includes the use of cell saver technology during surgery to collect and reinfuse the patient's own blood, minimizing the need for blood transfusions.

Anhepatic Phase 

The anhepatic phase during a liver transplant is a critical and unique period where the patient's diseased liver has been removed, and the new liver has not yet been fully connected and made functional. This phase is particularly challenging for several reasons:

No Liver Function: Since the liver performs many vital functions, including detoxification, protein synthesis, and production of clotting factors, its absence means these processes are temporarily halted. This can lead to an accumulation of toxins and a disruption in the body's metabolic balance.

Blood Clotting Issues: The liver is integral in producing clotting factors, so during the anhepatic phase, the patient is at an increased risk of bleeding due to reduced clotting factor production. This is compounded by the already complex vascular nature of the surgery and the potential for significant blood loss.

Hemodynamic Instability: The liver plays a role in regulating blood volume and pressure. Its removal can lead to hemodynamic instability, characterized by fluctuations in blood pressure and cardiac output. Managing the patient's fluid balance and circulation becomes more challenging during this phase.

Risk of Metabolic Complications: The liver's role in metabolism means its absence can lead to issues such as hypoglycemia. Monitoring and managing the patient's blood sugar and metabolic state are crucial during this time.

Due to these challenges, the anhepatic phase is a period of significant physiological stress for the patient. Anesthesiologists and surgical teams closely monitor vital signs, blood loss, and fluid balance. They may use various techniques and medications to support the patient's body until the new liver can be connected and begin functioning, thus ending the anhepatic phase. The shorter this phase can be kept, the better it is for the patient's overall outcome, as it reduces the time the body is without the critical functions provided by the liver.

Platelet Usage 

During liver transplant surgery, the consumption of a high number of platelets can be attributed to several factors, each emphasizing the complex interplay between liver function, surgical intervention, and the body's hemostatic processes:

Massive Blood Loss and Transfusions: Liver transplant surgeries often involve significant blood loss, requiring large volumes of blood transfusions. Transfused blood, especially when stored, may have reduced platelet function or count, necessitating additional platelet transfusions to maintain adequate hemostasis.

Dysfunctional Platelets: Patients with liver diseases, particularly those severe enough to require a transplant, often have dysfunctional platelets despite a normal or elevated platelet count. The liver plays a crucial role in producing coagulation factors and regulating platelet production. Liver disease can lead to thrombocytopenia (low platelet count) and qualitative platelet defects, making it necessary to transfuse platelets during surgery to correct these issues.

Activation of Coagulation System: The surgical stress and the extensive tissue manipulation during liver transplantation can activate the body's coagulation system. This activation can lead to the consumption of clotting factors and platelets, further necessitating the transfusion of platelets to maintain hemostasis.

Hypothermia: Liver transplants are long procedures, during which patients may become hypothermic. Hypothermia can impair platelet function, contributing to the need for platelet transfusions.

The Anhepatic Phase: As mentioned previously, during the anhepatic phase of the transplant, the patient's liver is not functioning, leading to an accumulation of toxins and further impairment of coagulation factors and platelet function. This phase can significantly contribute to the need for platelet transfusions.

The last liver transplant that came through our hospital took 16! SIXTEEN! Units of single donor apheresis platelets! Crazy. 

Blood Availability and Crossmatch 

The surgeon or anesthesia team will usually place blood orders ahead of time so Blood Bank can have blood products available for the surgery. Most of the time they request quite a bit of product up front, because of the 'bloody' nature of the surgeries. A previous surgeon would have a Liver Transplant Blood Package order of 8 RBCs, 8 FFP, and 4 platelets on hold. The new surgeon that took over wanted 4 whole blood, 10 RBCs, 10 FFP, and platelets/cryo as they go. Pretty wild. We basically had to change our entire policy for the surgeon, as our whole blood units were initially only intended and validated for use on adult male traumas in the ER.


Post a Comment