pediagenosis: Transplantation
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Showing posts with label Transplantation. Show all posts
Showing posts with label Transplantation. Show all posts

Tuesday, May 18, 2021

Assessment For Liver Transplantation

Assessment For Liver Transplantation


Assessment For Liver Transplantation
Assessment of the transplant candidate
As with renal transplantation, assessment of a potential liver transplant recipient involves not only evaluation of the liver disease for which transplantation is indicated, but also determination of comorbidity that may affect peri or post-operative morbidity and mortality. Moreover, since liver transplantation is now a successful treatment for liver failure, focus has switched to ensuring longterm survival rather than just surviving the surgical assault. The shortage of organs has necessitated increased selectivity, favouring patients with better anticipated outcomes.

Assessment For Liver Transplantation

Evaluating the liver disease
Most liver screening tests are repeated to verify the diagnosis and rule out other diseases. These are illustrated in Figure 34.
Complications Of Liver Transplantation

Complications Of Liver Transplantation


Complications Of Liver Transplantation
Monitoring the liver
Careful and frequent clinical review is required post transplant to identify deterioration suggestive of complications. Post-transplant biochemical monitoring uses the same markers of liver dysfunction as were used before transplantation, namely:
1.    Prothrombin time, for synthetic function;
2.    Alanine transaminase (alt) and aspartate transaminase (ast), for hepatocellular damage;
3.    Alkaline phosphatase (alp): reflects bile duct damage;
4.    Serum lactate, should start to fall towards normal within an hour or two of reperfusion of the liver giving earliest sign of function;
5. Ultrasonography is used to detect biliary dilatation and assess blood flow to the liver, supplemented by ctyangiography.

Complications Of Liver Transplantation

Surgical complications
Non-specific complications of surgery
Bleeding is common due to a combination of factors:
·      The presence of abdominal varices
·      A coagulopathy, particularly if the liver is slow to resume full protein synthesis
·      Thrombocytopaenia due to splenomegaly
·      Multiple venous and arterial anastomoses.
Intestinal Failure And Assessment

Intestinal Failure And Assessment


Intestinal Failure And Assessment
Intestinal failure
Intestinal failure means that the patient can no longer maintain their nutritional needs by oral intake of food. In some patients, for example those who have had a recent bowel resection, this is a temporary state that will recover as the residual bowel adapts; in others with very diseased bowel or major resections the condition may be irreversible with a continued requirement for parenteral nutrition (PN).
Parenteral nutrition is the main treatment for patients with intestinal failure. It requires an indwelling central venous catheter to which the patient connects a bag of nutrition (typically 2.5 litres) every evening to run over 12 to 14 hours through the night. Most patients can live a reasonable existence on such therapy.

Intestinal Failure And Assessment, Venous thrombosis,

Complications of parenteral nutrition
The 1-year survival of a patient on home PN is 90%, falling to 65% at 5 years. There are three principal complications of long-term PN.
Assessment For Heart Transplantation

Assessment For Heart Transplantation


Assessment For Heart Transplantation
While heart transplantation remains an excellent treatment for advanced heart failure, the number of transplants performed in Europe is falling due to the lack of suitable donors. The assessment of potential recipients has therefore become more stringent in order to make optimal use of available organs. Many patients referred for transplantation can be improved with conventional cardiac surgery and/or improved medical management, including resynchronisation therapy with biventricular pacing. A classification of underlying diseases is given in Figure 39.

Assessment For Heart Transplantation

Assessment for transplantation
The assessment of potential recipients involves three components:
   functional capacity
   right heart catheterisation to assess pulmonary circulation
   comorbidity.

Sunday, April 25, 2021

Complications Of Heart Transplantation

Complications Of Heart Transplantation


Complications Of Heart Transplantation
Early complications
The initial complications of heart transplantation relate to donor events, damage due to cold ischaemia, reperfusion injury, technical complications and the haemodynamic challenge facing the new heart in the recipient.
·  Bradycardia – related to cold ischaemia, damage to the sinoatrial node or pre-transplant treatment with amiodarone. Treatment comprises either isoproterenol (isoprenaline) or temporary atrioventricular pacing.
·     Atrial fibrillation or flutter occurs in up to a fifth of patients.
·    Right ventricular failure – due to pre-existing pulmonary hypertension and high pulmonary vascular resistance. Isoproterenol is a pulmonary vasodilator as well as a chronotrope, and is used routinely. Inhaled nitric oxide can be a useful addition to reduce pulmonary artery pressure.
·      Systemic hypotension may be due to impaired left ventricular function, which may recover. Reduction in peripheral vascular resistance may occur due to acidosis and vasoconstricting inotropes such as noradrenaline or vasopressin may be required.
·     Valvular dysfunction. Tricuspid regurgitation is more common and may relate to dilatation of the tricuspid valve ring due to high pulmonary pressures. It typically recovers within 12 months.
·      Bleeding resulting in tamponade may occur.
·   Pericardial effusion may also occur and sometimes requires treatment, although it usually resolves within 6 weeks.
· Renal dysfunction is very common, particularly in patients with pre-existing renal impairment, those requiring prolonged bypass (retransplants, previous congenital heart disease) and as a consequence of calcineurin inhibitor immunosuppression. Short-term haemofiltration should be started early and does not confer any late disadvantage.

Complications Of Heart Transplantation

Immunosuppression
A typical immunosuppressive regimen would comprise an induction agent such as antithymocyte globulin or basiliximab, with maintenance therapy with tacrolimus, mycophenolate and steroids. In addition, statins such as pravastatin are also used in the early post-transplant period, regardless of serum cholesterol level.
Assessment For Lung Transplantation

Assessment For Lung Transplantation


Assessment For Lung Transplantation
Indications for lung transplantation
Lung transplantation is indicated for end-stage obstructive, septic, restrictive lung disease or pulmonary vascular disease. In broad terms, the presence of septic disease (e.g. cystic fibrosis) or pulmo- nary hypertension is an indication for bilateral lung transplantation; obstructive or restrictive disease may be treated by single or bilateral lung transplantation. Combined heart lung transplantation, popular in the 1990s, is now rarely performed, although may be indicated for some complex congenital heart diseases.
A decision to offer lung transplantation is based on physical status, quality of life and comorbidity.

Assessment For Lung Transplantation

Assessment investigations
Forced expiratory volume in one second (FEV1) is the amount of breath forcibly exhaled in 1 second. It is usually expressed as a proportion of the value predicted for age, sex and build. A reduced FEV1 signifies obstruction to air escaping.
Lung Transplantation: The Operation

Lung Transplantation: The Operation


Lung Transplantation: The Operation
The Lung Donor
Donor selection
Matching donor and recipient involves matching blood group and donor size, and avoiding any incompatible HLA antigens that might result in hyperacute or early humoral rejection. Size is very important, particularly avoiding putting large lungs into small chests, which will result in pulmonary collapse and infection.
Lung assessment differs between DCD and DBD donors.
Lung Transplantation: The Operation

Lung retrieval from donors following brain death
In DBD donors, where the heart is still beating, the donor undergoes bronchoscopy before retrieval surgery commences to look for evidence of infection or inflammation; bronchial aspirates are sent for Gram stain and culture to inform choice of antibiotics in the recipient. Once the operation begins the lungs are inspected externally and care is taken to ensure that all segments are fully inflated, with no evidence of atelectasis, consolidation, masses or trauma. Pulmonary vein oxygen levels are measured by aspirating blood directly from left and right upper and lower pulmonary veins. A PO2 >40 kPa is desirable.
The lungs are preserved by perfusing a low-potassium/dextran preservation solution (Perfadex), together with a prostaglandin vasodilator, via the pulmonary artery, with the lungs ventilated to aid distribution of perfusate. Following this, additional retrograde perfusion is given via the pulmonary veins to wash out clots. This may also perfuse the bronchial arteries, which arise directly from the descending thoracic aorta.
Complications Of Lung Transplantation

Complications Of Lung Transplantation


Complications Of Lung Transplantation
Early Complications
Initial post-transplant management
The early management of patients post-lung transplantation involves limiting airway pressures (<35 mmHg) and physiotherapy to improve expectoration; tracheostomy may be indicated to facilitate tracheal toilet if prolonged intubation is anticipated. Fluid management aims to keep the recipient in a negative balance so as not to waterlog the lungs, and colloids may be preferred to crystalloids for the same reason.


Complications
The early complications following lung transplantation may be divided into four types.
1.    Technical complications relating to the surgery
These are now uncommon.
Composite Tissue Transplantation

Composite Tissue Transplantation


Composite Tissue Transplantation
Vascularised composite tissue allotransplantation (CTA) reflects the fact that the vascularised graft includes many different tissues, such as bone, nerve, muscle, tendons and skin. The most common example is hand transplantation, but face, laryngeal and abdominal wall transplantation are other examples. Abdominal wall transplants have been used in a few multivisceral transplant recipients to gain abdominal domain – in other words to make room for the bowel.

Hand transplantation

Hand transplantation
Indications
Loss of one hand causes significant disability and carries many psychological and social stigmata, but loss of both upper limbs is a devastating handicap. While prosthetics may provide a substitute that can be used to compensate for loss of a single limb, none can substitute for the tactile sense that is required for many activities of daily living. The benefits of such transplantation need to be balanced against the need for immunosuppression. Possible indications include:

Saturday, April 24, 2021

Xenotransplantation

Xenotransplantation


Xenotransplantation
Aspirations for xenotransplantation
The shortfall between the number of available organs for transplantation and the number of patients on the transplant waiting lists is ever widening. One solution to this that has been explored since Jaboulay’s first efforts in the 1900s is the use of animal organs, so-called xenotransplantation. In spite of much research, xenotransplantation has failed to achieve the successes hoped for, and with every new finding more hurdles appear to slow its progress.
Many xenotransplants have been performed, ranging from kidney, liver and heart transplants using dog, goat, pig or primate organs, to the transplantation of specialised cells in an attempt to cure diabetes or Parkinson’s disease. None has yet been successful.
Xenotransplantation

Barriers to success
Donor selection
It is generally agreed that the favoured animal for mass breeding as donors for transplantation is the pig, for the following reasons.
·     The animals are of a similar size to man, compared with primates such as baboons, which are much smaller.
·       Organs are anatomically similar to those in man.
·       Breeding programmes are well established, and gestation is short.
·      Genetic manipulation has been shown to be possible.
In the paragraphs that follow we have assumed that the pig is the donor; similar considerations apply whatever the species chosen.

Wednesday, October 14, 2020

History Of Transplantation

History Of Transplantation


History Of Transplantation
Fundamentals
Vascular anastom ses
Transplantation of any organ demands the ability to join blood vessels together without clot formation. Early attempts inverted the edges of the vessels, as is done in bowel surgery, and thrombosis was common. It wasn’t until the work of Jaboulay and Carrel that eversion of the edges was shown to overcome the early thrombotic problems, work that earned Alexis Carrel the Nobel Prize in 1912. Carrel also described two other techniques that are employed today, namely triangulation to avoid narrowing an anastomosis and the use of a patch of neighbouring vessel wall as a flange to facilitate sewing, now known as a Carrel patch.
Diagnosis Of Death And Its Physiology

Diagnosis Of Death And Its Physiology


Diagnosis Of Death And Its Physiology
Diagnosing death
Circulatory death
Traditionally, death has been certified by the absence of a circulation, usually taken as the point at which the heart stops beating. In the UK, current guidance suggests that death may be confirmed after 5 minutes of observation following cessation of cardiac function (e.g. absence of heart sounds, absence of palpable central pulse or asystole on a continuous electrocardiogram). Organ donation after circulatory death (DCD) may occur following confirmation that death has occurred (also called non-heart-beating donation). There are two sorts of DCD donation, controlled and uncontrolled.
Deceased Organ Donation

Deceased Organ Donation


Deceased Organ Donation
Opting in or opting out?
In the UK, as in most countries in the world, the next of kin are approached for consent/authorisation for organ donation, a system known colloquially as ‘opting in’. This system is facilitated by having a register, such as the UK organ donor register (ODR), where people can register their wishes to be a donor when they die; 29% of the UK population are on the register. However, opinion polls show that nearer to 90% of people are in favour of organ donation, suggesting that the shortfall is a consequence of apathy. When a person is on the ODR the relatives are much more likely (>90%) to consent to donation than where the wishes of the deceased were not known (60%).
Live Donor Kidney Transplantation

Live Donor Kidney Transplantation


Live Donor Kidney Transplantation
The limited supply of deceased donor organs and an ever-increasing number of patients waiting for kidney transplantation has led to the widespread use of living donors. Renal transplantation has the unique advantage, compared with other organs, that most individuals have two kidneys, and if not diseased, have sufficient reserve of renal function to survive unimpeded with a single kidney. The shortage of donors has also led to the use of parts of non-paired organs, such as liver and lung lobes, the tail of pancreas and lengths of intestine from living donors; indeed, even live donation of the heart has occurred, when the donor has lung disease and received a combined heart-lung transplant, with their own heart being transplanted to someone else, so called ‘domino transplantation’. For the purposes of this chapter we will focus on live kidney donation, but similar principles apply to other organs.
Live Donor Liver Transplantation

Live Donor Liver Transplantation


Live Donor Liver Transplantation
Live liver donation
Much of what has been said about the assessment of a kidney donor applies to a liver donor, with the exception that the full assessment of the liver, its function, exclusion of disease and assessment of its anatomy are paramount.
The Right Materials

The Right Materials


The Right Materials
One of the most important factors in biomedical engineering is biocompatibility – the interaction of different materials with biological tissues. Implanted materials are often chosen because they are ‘biologically inert’ and as a result they don’t provoke an immune response. These can include titanium, silicone and plastics like PTFE. Artificial heart valves are often coated in a layer of mesh-like fabric made from the same plastic used for soft drink bottles – Dacron. In a biological context, the plastic mesh serves as an inert scaffold, allowing the tissue to grow over the valve, securing it in place. Some scaffolds used in implants are even biodegradable, providing temporary support to the growing tissue, before harmlessly dissolving into the body.
Innate Immunity

Innate Immunity


Innate Immunity
The role of the immune system is to identify and remove invading microorganisms before they cause harm to the host. This is achieved by a rapid, non-specific innate immune response that is followed by a more finely tuned, targeted, adaptive immune response. The innate immune system is comprised of components that directly recognise and destroy pathogens (the complement system), a number of ‘flags’ known as opsonins (e.g. C-reactive protein [CRP], C3b, natural IgM antibody), which make pathogens more easily recognised by immune cells such as phagocytes (neutrophils and macrophages), which engulf and kill internalised pathogens, and natural killer (NK) cells, which can detect and destroy virus-infected cells.

Wednesday, December 11, 2019

Heart Transplantation: The Operation

Heart Transplantation: The Operation


Heart Transplantation: The Operation
Donor selection
Waiting list mortalit
The appropriateness of using any organ for transplantation must be balanced against the risk of the recipient dying on the waiting list if the transplant does not proceed, and in the knowledge that many other patients who might potentially benefit from transplantation have been excluded from the list because of donor organ shortage. In the first year on the waiting list around 60% of patients will receive a heart, while 10–15% will die waiting.

Sunday, November 17, 2019

Intestinal Transplantation

Intestinal Transplantation


Intestinal Transplantation
Types of transplant
There are three main types of intestinal transplantation performed. All involve transplanting a sufficient length of small intestine to achieve independence from parenteral nutrition (PN). The large intestine is not usually transplanted, although its inclusion has been proposed as a way to reduce fluid losses. The terminal ileum is brought out as an ileostomy to facilitate biopsy, although this may be reversed in the long term by anastomosis to the native colon (if still present) to restore gut continuity. Where there is pre-existing renal failure it is sensible to perform a kidney transplant at the same time.

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