Why Can Liver Transplants Use So Much Blood?
It can also be an absolute nightmare for the Blood Bank.
Blood utilization during liver transplantation has fallen dramatically at many centers as surgical techniques, anesthesia, cell salvage, patient blood management, and point-of-care coagulation testing have improved. Some liver transplants can now be completed with little or even no allogeneic blood.
Others?
Not so much.
A difficult liver transplant can still turn into a massive-transfusion situation very quickly. A 2025 single-center study of 844 adult liver transplants found that about 10% required what the investigators classified as an ultra-massive fluid transfusion, demonstrating just how extreme the resuscitation requirements can still become in selected cases.
So why can liver transplantation be so bloody?
Why Do Liver Transplants Bleed?
There isn't one single reason.
The recipient often arrives in the operating room with abnormal hemostasis before the surgeon makes the first incision, and the operation itself creates several additional opportunities for major hemorrhage.
Portal Hypertension and Collateral Vessels
Many transplant recipients have advanced cirrhosis with portal hypertension.
As pressure increases within the portal venous system, blood is redirected through collateral vessels. These enlarged and sometimes fragile vessels can develop throughout the abdomen.
That makes surgical dissection considerably more difficult.
The surgeon isn't simply removing a normal liver from an otherwise normal vascular system. They may be dissecting through a distorted, scarred, highly vascular field containing large collateral vessels under elevated pressure.
Major Vascular Dissection
The liver receives blood through both the portal vein and hepatic artery, while hepatic veins drain into the inferior vena cava.
During transplantation, the surgical team has to dissect, divide, and reconstruct major vessels while removing the recipient liver and implanting the donor organ.
Bleeding can occur during dissection and during creation of the vascular anastomoses.
Previous abdominal surgery, adhesions, portal-vein thrombosis, unusual anatomy, retransplantation, or severe portal hypertension can make the procedure considerably more difficult.
Cirrhosis and “Rebalanced Hemostasis”
Historically, patients with advanced liver disease were often described as simply being coagulopathic.
They have prolonged PT/INR values.
They may have low fibrinogen.
They frequently have thrombocytopenia.
Therefore, the reasoning went, they must be prone to bleeding.
It turns out that the situation is much more complicated.
The liver synthesizes not only many procoagulant proteins, but also important anticoagulant proteins. Advanced liver disease therefore reduces components on both sides of the coagulation system.
Patients with cirrhosis can additionally have:
thrombocytopenia
altered platelet function
reduced procoagulant factors
reduced natural anticoagulants
increased von Willebrand factor
reduced ADAMTS13
changes in fibrinolysis
The result is often described as rebalanced hemostasis.
The balance is fragile and can be pushed toward bleeding or thrombosis by infection, renal failure, surgery, shock, dilution, hypothermia, and other physiologic stressors.
This is why an elevated INR in cirrhosis does not automatically mean the patient needs plasma and does not accurately represent the entire coagulation system.
Liver transplantation then takes that already fragile system and subjects it to massive surgery.
The Phases of Liver Transplantation
Liver transplantation is often divided into three broad phases:
Pre-anhepatic/dissection phase
Anhepatic phase
Neohepatic/reperfusion phase
Each creates different problems for hemostasis and transfusion management.
The Pre-Anhepatic Phase
During the first phase, the native liver is still present while the surgical team mobilizes it and prepares the major vessels for removal.
This can be one of the bloodiest portions of the operation.
Portal hypertension, abdominal collateral vessels, adhesions, previous surgery, and difficult vascular anatomy can all contribute to major blood loss.
Active hemorrhage can then create additional coagulopathy through:
consumption of platelets and coagulation factors
dilution from replacement fluids and RBC transfusion
hypothermia
hypocalcemia from citrate exposure
worsening acidosis
So the bleeding itself can progressively make additional bleeding more likely.
The Anhepatic Phase
The anhepatic phase begins when the recipient liver has been removed and ends when the donor liver is implanted and reperfused.
For a period of time, the patient literally has no functioning liver.
That's physiologically bizarre, but the major immediate problems are a little different from simply “the patient stops producing clotting factors.”
Loss of Hepatic Clearance
One particularly important change involves fibrinolysis.
The liver normally clears tissue plasminogen activator (tPA) from circulation.
During the anhepatic phase, hepatic clearance disappears while endothelial cells can continue releasing tPA. Fibrinolytic activity can therefore increase, causing formed fibrin clots to be broken down more rapidly.
Studies of coagulation during liver transplantation have demonstrated increasing fibrinolytic activity during the anhepatic period, with potentially even greater disturbance around reperfusion.
Hemodynamic Changes
Major venous vessels may be clamped or partially occluded during implantation.
Depending on the surgical technique, interruption of portal and vena-caval blood flow can substantially reduce venous return to the heart and alter cardiac output.
Modern techniques such as piggyback transplantation, portocaval shunting, and selective use of venovenous bypass can reduce some of these effects, but the anhepatic phase remains a major anesthetic challenge.
Metabolic Changes
The absent liver can no longer perform its normal metabolic and clearance functions.
During this period the anesthesia team carefully monitors:
acid-base status
glucose
electrolytes
ionized calcium
temperature
lactate
coagulation
hemodynamics
The patient is essentially being physiologically supported until the new liver enters the circulation.
Reperfusion: Things Can Get Weird Fast
The neohepatic phase begins when blood flow is restored to the transplanted liver.
This can be one of the most dramatic moments of the entire operation.
Blood suddenly enters an organ that has undergone cold and warm ischemia. Metabolites, potassium, acid, cytokines, and other substances can enter the recipient's circulation.
Some patients develop post-reperfusion syndrome, with significant hypotension and cardiovascular instability immediately after reperfusion.
Coagulation can change abruptly as well.
Hyperfibrinolysis
Fibrinolysis that developed during the anhepatic phase may become especially pronounced immediately following reperfusion.
A poorly functioning graft may initially fail to clear tPA effectively, and severe hyperfibrinolysis can produce diffuse nonsurgical bleeding.
Heparin-Like Effect
The graft can also release endogenous heparin-like substances following reperfusion.
On viscoelastic testing, severe postoperative clotting abnormalities shortly after reperfusion have been attributed to both hyperfibrinolysis and heparin-like effects.
Interestingly, these abnormalities may subsequently improve as a functioning graft begins clearing substances from the circulation and synthesizing new proteins.
So the patient's coagulation status during a liver transplant can change dramatically over the course of an hour.
That's one reason conventional PT, INR, fibrinogen, and platelet counts alone are often too slow and too incomplete to guide every intraoperative transfusion decision.
Enter TEG and ROTEM
This is where viscoelastic testing has become extremely important.
TEG and ROTEM evaluate clot formation and breakdown in whole blood in real time.
Instead of merely asking:
"What's the INR?"
the transplant team can ask much more useful questions:
Is clot initiation actually delayed?
Is the clot weak because of low fibrinogen?
Is platelet contribution inadequate?
Is the patient hyperfibrinolytic?
Is there evidence of a heparin-like effect?
Those answers can direct therapy toward the actual abnormality rather than reflexively giving plasma, platelets, and cryoprecipitate because several conventional laboratory values look ugly.
A survey of U.S. liver-transplant centers found that 97% of responding centers used viscoelastic testing, and 97% also reported use of intraoperative cell salvage.
Studies have also shown reductions in plasma and RBC utilization after implementation of ROTEM-guided transfusion algorithms.
Why Do Liver Transplant Patients Need Platelets?
Platelets are particularly interesting in liver transplantation.
Advanced liver disease frequently causes thrombocytopenia, but not simply because “the liver isn't making platelets.”
The mechanisms can include:
portal hypertension and splenic sequestration
decreased hepatic production of thrombopoietin
increased platelet consumption
immune-mediated mechanisms
infection and inflammation
bone-marrow suppression
medications
And once surgery begins, blood loss, hemodilution, consumption, hypothermia, and metabolic derangements may further impair platelet number or function.
But there is another important wrinkle:
A low platelet count does not automatically equal inadequate hemostasis in cirrhosis.
Increased circulating von Willebrand factor can partially compensate for thrombocytopenia and altered platelet function, another component of the rebalanced-hemostasis model.
So modern liver-transplant practice generally does not aim to normalize the platelet count simply because it is low.
The more important question is:
Is the patient bleeding, and does the overall coagulation assessment show inadequate platelet contribution to clot strength?
Viscoelastic testing can help answer that.
Platelets Aren't Benign
There is good reason to avoid unnecessary platelet transfusion.
Observational studies have repeatedly found associations between intraoperative platelet transfusion during liver transplantation and adverse outcomes, including pulmonary complications and mortality. Those studies cannot prove that platelets themselves caused the worse outcomes—patients receiving large numbers of platelets are obviously also among the sickest and most severely bleeding—but they reinforce the principle that platelet transfusion should be targeted rather than automatic.
This makes a case requiring an enormous number of platelet units particularly notable.
I once saw a liver transplant come through the Blood Bank that ultimately required 16 single-donor apheresis platelet units.
SIXTEEN.
That is not normal everyday liver-transplant usage. That is a patient with extraordinary transfusion requirements.
RBCs, Plasma, Cryo and Fibrinogen
RBCs obviously replace lost oxygen-carrying capacity during hemorrhage.
The other components are increasingly given according to the specific coagulation defect rather than by a fixed ratio whenever possible.
Plasma
Plasma may be useful when there is clinically significant bleeding accompanied by inadequate coagulation-factor activity.
But an elevated INR alone in a patient with liver disease is not a good reason to dump plasma into the patient.
The INR captures only part of the coagulation system and does not measure the corresponding decline in endogenous anticoagulants.
Fibrinogen and Cryoprecipitate
Fibrinogen can fall substantially during major hemorrhage and liver transplantation.
Depending on the institution and country, replacement may be accomplished with cryoprecipitate or fibrinogen concentrate.
Viscoelastic assays such as FIBTEM can help determine whether impaired fibrin-based clot strength is actually contributing to the coagulopathy. Contemporary transplant centers vary considerably in exactly how they replace fibrinogen.
Cell Salvage
One of the major blood-conservation tools during liver transplantation is intraoperative cell salvage.
Shed blood from the surgical field can be collected, processed, washed, and returned to the patient as autologous RBCs.
That reduces the number of donor RBC units required and is now extremely common in liver-transplant practice.
It doesn't replace plasma, platelets, or fibrinogen, but when the surgical field is producing liters of blood, recovering the patient's own red cells can dramatically decrease demand on the Blood Bank.
Blood Availability and the Blood Bank
And now we get to the part the Blood Bank actually experiences.
The surgeon and anesthesia team usually notify the transfusion service in advance so adequate products can be available when the operation begins.
Exactly how much is physically crossmatched, thawed, or staged varies enormously by institution.
One surgeon at our hospital used a liver-transplant blood package of:
8 RBCs
8 plasma
4 apheresis platelets
Then another surgeon arrived and wanted:
4 whole-blood units
10 RBCs
10 plasma
platelets and cryoprecipitate as needed
Pretty wild.
And yes, that meant changing local blood-bank procedures because our whole-blood inventory had originally been validated specifically for selected adult trauma patients.
That illustrates something important:
There is no universal “liver-transplant blood package.”
A 2023 survey of liver-transplant centers found substantial variation in transfusion practice. Nearly all centers used viscoelastic testing and cell salvage, but standardized thresholds and approaches to plasma, platelets, fibrinogen replacement, antigen selection, and emergency substitution differed between institutions.
The Blood Bank therefore has to build its inventory and procedures around the practices of its transplant program.
And Then There Are Antibodies...
Things become even more interesting when the transplant recipient has clinically significant RBC alloantibodies.
Having ten compatible RBC units available is easy if your patient is a straightforward A-positive patient with a negative antibody screen.
It becomes considerably more entertaining when the patient has something like:
anti-E, anti-K, and anti-Jka
and anesthesia would really like ten units sitting in the operating room.
Large anticipated blood requirements can force the Blood Bank to:
phenotype or genotype the patient
locate sufficient antigen-negative units
coordinate with the blood supplier
balance antigen matching against emergency availability
prepare contingency plans if compatible inventory becomes depleted
And unlike an elective procedure that can simply be postponed when compatible blood isn't available, a donor organ introduces a very real clock.
The transplant can't necessarily wait several days while somebody searches the country for ten beautifully matched units.
That makes communication between the transplant service, anesthesia, Blood Bank, blood supplier, and reference laboratory especially important.
Liver Transplants Are Different
Modern liver transplantation is considerably less transfusion-intensive than it once was.
But it remains one of the few surgeries where the Blood Bank may need to prepare for everything from:
“They didn't use a single unit.”
to:
“Send everything you've got.”
The reason isn't merely that the liver is vascular.
The patient begins with an unusually complex and fragile hemostatic system. Surgery introduces major vascular injury and blood loss. The anhepatic phase alters metabolism and fibrinolysis. Reperfusion can suddenly produce hyperfibrinolysis, heparin-like effects, and profound hemodynamic changes.
And all of it can evolve in real time.
That's what makes liver transplantation such an interesting transfusion-medicine case: the goal isn't simply to replace whatever laboratory value is low. It's to figure out what part of hemostasis is actually failing at that particular moment—and give the patient what they actually need.
0 comments:
Post a Comment