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Types of donor organ: a reminder
Here Dr Andrew Owen, an Anaesthetist and Academic Clinical Fellow reminds us of the definitions of DBD and DCD organs.
DR.
ANDREW OWEN: Hello. My name is Dr. Andrew Own. I am what’s called a clinical research training fellow, which means that I’m currently doing a PhD in the liver labs. But I also do some clinical work as an anaesthetic and intensive care registrar. [On Screen: Can you explain the terms DCD and DBD to us in the context of types of donor organ collected for transplantation?] So DCD is an abbreviation for a Donation after Cardiac or Circulatory Death. DBD stands for Donation after Brainstem Death. So when a patient on intensive care undergoes brainstem death testing, it’s a way of defining them as being dead, but their heart is still beating. So this is what’s called a heart-beating donor.
If a patient doesn’t fulfil the criteria for brainstem death, but treatment is perceived to be futile, and critical care treatment is going to be withdrawn, we have to wait for the patient’s heart to stop before they’re classed as being dead. And that’s what becomes a donation after cardiac or circulatory death donor. There are key differences between these types of donors that are important in the context of liver transplantation, and also other organ transplantation, such as kidney. A donation after brainstem death donor is an operation that is slightly more elective in its nature, in that we can plan to take the patient to theatre at a certain time.
And right up until the point where the clamp goes on and the perfusion fluid goes into the liver, the patient’s heart is still beating, and they’re maintaining a blood pressure. So that liver doesn’t have a significant, what we call, warm ischemic injury. It has a cold ischemic injury, in that the perfusion fluid goes into the liver, becomes cold. And ischemia, therefore, being a lack of blood flow means that the organ then gets damaged. But that is much less significant when the liver is cold and under preservation. A donation after cardiac death patient, their heart has to stop, and then we have to start the operation.
And there is clearly a small lag time between the patient’s heart stopping and the patient going into theatre and being operated on. So we have a longer, what is called, warm ischemic period. That period can be prolonged even more if, when we withdraw our support, which could be blood pressure support or could be ventilatory support, if the patient’s heart does not stop straightaway, which is often the case. We only have a limited window for warm ischemic time, in which we can take a liver or a kidney out of a patient and it still be useful in the context of transplantation. For liver, that’s only around about 30 minutes. So that really doesn’t give us a long time.
In terms of the organ and the quality of the organ when it goes into the patient, there is a mixed opinion on the differences between a DCD and a DBD liver. It’s clearly very important how long that warm ischemic period lasts for. And the longer it lasts for, the more injury that liver undergoes and, therefore, the more likely we are to see complications in the post-operative period. But that includes things such as a prolonged intensive care stay, a longer time needing support of blood pressure, and also the liver potentially not functioning once we plumb in the liver and let it take over the function within the recipient patient.
[On screen: Can you tell us a bit more about what the anaesthetist team does during complex surgery?] So the anaesthetic team is made up of a large number of people, including the anaesthetist, the operating department practitioners, the theatre runners, as well as the wider team, such as the surgeons and the transplant coordinators. We have a role throughout the liver transplant process, both in the preoperative, the perioperative, and the post-operative care of a patient undergoing a liver transplant. The preoperative care involves mainly assessing risk of a patient and their risk of having a transplant operation.
And that’s done in close conjunction with the other teams, such as the surgical team, the medical team, the nutritionists, the physiotherapists, and the wider team involved in transplant assessment. In the perioperative period– this normally covers the time from when we put the patient to sleep to when we wake them up again– we’re responsible not only for maintaining anaesthesia, which means keeping a patient asleep, making sure that they’re not aware of what’s going on in the surgery, but also creating an environment which is favourable for the surgeon to undertake and carry out that operation. We’ll be responsible for maintaining the airway of the patient and keeping the patient breathing. And usually, we do that with a ventilator.
We’ll also put in various monitoring devices, which allow us to look at both depth of anaesthesia, patients’ temperature, the cardiovascular status. And we’ll put a number of lines into both blood vessels, such as veins and arteries, allowing us to measure invasively the arterial pressure and the venous pressure, as well as large points of access that allow us to deliver fluid and blood products, should we need them. During the operation, we also look at things such as blood clotting. We do that with a point-of-care testing machine. But also we look at the way the blood clots using something called a thromboelastogram.
And this allows us to tailor the use of blood products, such as clotting agents, as well as red blood cells to the patient’s clotting profile, which can change considerably during a transplantation operation. [On Screen: How do the anaesthetist team continue to assist with the patient care after the operation?] So in the post-operative period, we are caring for the patient in conjunction with our colleagues in the intensive care unit, as well as the surgical and medical teams, as discussed before. During the perioperative period, we usually put in some sort of device for maintaining pain relief in the post-operative period. And that’s usually an epidural though not always. This is something that’s then monitored and looked after on the intensive care unit.
All of the lines that I discussed earlier for monitoring pressure are also left in the post-operative period. And they, again, are looked after on the intensive care unit by the intensive care team. [Music Playing]
In this activity we meet Dr Andrew Owen who is an Anaesthetist and Academic Clinical Fellow working in the Centre for Liver Research.
Andy has taken time out from his clinical training to study for a PhD at the University of Birmingham to investigate ways in which stem cells can be used to improve the quality of donor organs for transplantation. We will learn more about his research in Week 3 but today Andy will explain the different categories of donor liver that can be used. He will revisit terms you have already heard and provide a clear definition before we go on to discuss the surgery. He’ll also tell you a little more about the role of the anaesthetists during transplantation surgery.
Don’t forget to add any useful details to your glossary and discuss this video with other learners in the comments.
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