Anaesthesia for the Patient with a Transplanted Organ

Published on 27/02/2015 by admin

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Anaesthesia for the Patient with a Transplanted Organ

INTRODUCTION

There have been several advances in surgical techniques, perioperative management and immunosuppressive regimens to prevent early and late organ rejection. These have led to improvements in short and long-term outcomes after transplantation, with most patients now able to lead a relatively normal life (see Table 39.1). Furthermore, outcomes following patient re-transplantation after rejection or graft failure have improved. As a result, it is likely that non-transplant anaesthetists are more likely to encounter transplant recipients presenting for elective surgery in the future. Transplant recipients are more likely than the general population to require surgery for malignancy or emergency procedures especially for acute gastrointestinal pathology. In addition, the increased success of solid organ transplantation has led to the recipient population being older and having more comorbidities than previously. Furthermore, the use of ‘marginal’ donor organs, secondary to the relative shortage of organs, is likely to make the management of these patients more complex. In general, wherever recipients present for non-transplant surgery, the patient is likely to have both residual evidence of chronic disease, be immunocompromised and have reduced organ function. In the emergency situation, the effect of acute illness may also complicate further anaesthetic management.

Careful attention to detail in the anaesthetic management of these patients will allow a smooth transition through the current surgical problem and perioperative process without disruption of the complex immunosuppressive regimens and without the risk of rejection.

GENERAL CONSIDERATIONS

Immunosuppression

Immunosuppressive regimens are an absolute necessity in promoting long-term benefit from transplantation. The use of mainly steroid-based immunosuppressive regimens is gradually being substituted with the development of newer agents which have fewer generalized adverse effects. As a result, the complications of steroid overdose are seen less commonly and iatrogenic Cushing’s syndrome is rare. However, even newer regimens have significant adverse effects and require careful monitoring. The greatest risk of graft rejection is within the first year after transplantation, especially in the first few months. Immunosuppressive regimens may be classified as:

The characteristics, side effects and drug interactions of the main immunosuppressive agents are shown in Table 39.2.

Plasma drug monitoring is usually performed by transplant physicians and most patients presenting for elective surgery are on a stable regimen of immunosuppressive drugs. Even with stable chronic treatment these patients remain at risk of:

image increased risk of infection (see Table 39.3) – all staff should be aware of the risks of opportunistic infections and take appropriate precautions, including aseptic techniques and microbiological monitoring.

TABLE 39.3

Organisms Causing Common Opportunistic Infections in Transplant Recipients

CMV (cytomegalovirus)

Fungi – Aspergillus sp, Candida sp

Pneumocystis sp

Legionella sp

Toxoplasma sp

Listeria sp

image reduced wound healing – long-term immunosuppression also reduces the tensile strength of tissues and therefore may impair wound healing.

image major drug interactions – immunosuppressive drugs can cause interactions with a number of medications used for anaesthesia or postoperative pain relief.

image damage to other organ systems.

The presence of acute illness in combination with surgical stress is likely to create a period of instability. Early communication with the transplant team regarding immunosuppressive therapy is important to prevent large alterations of plasma drug concentrations. These may cause:

Residual Comorbidity

It is important to consider the nature of the disease process leading to the initial requirement for transplantation. Although some systemic manifestations are reduced by successful transplantation, residual disease in other organs associated with pre-transplant disease may remain (e.g. lung disease secondary to impaired liver function, cardiac disease secondary to renal failure).

The interval between organ transplantation and subsequent elective surgery determines the likelihood, nature and complexity of anaesthetic problems. Within the first 6 months after transplantation, the major considerations for the anaesthetist are those of graft rejection and acute changes in physiology. One year after successful transplantation, the likelihood of significant physiological changes is lower although the risk of chronic rejection always remains.

ANAESTHETIC CONSIDERATIONS

Preoperative

Presence of Infection

In addition to the presence of infection causing the initial requirement for transplantation (e.g hepatitis or CMV), the development of de novo infection must be investigated. However, the diagnosis may be difficult in these patients because typical presenting features may be absent. Fever may not be present and given that some drug regimens cause leucopoenia, an increased white cell count for a particular patient may lie within the ‘normal’ range. In elective situations, a recent culture screen for infection should have been performed before surgery and will guide further management. Early discussion with microbiology colleagues should take place to assess the correct regimen for surgical prophylaxis. There is no evidence to support an increase in the use or duration of prophylactic perioperative antibiotics in the transplant recipient.

Function of Other Organ Systems

Although the status of the transplanted organ and associated system is important, the systemic effect of the disease process that created the need for transplant must also be considered. Although transplantation may reduce the effects of this disease, full reversal of major systemic disease is unlikely.

Cardiovascular issues are common to many multisystem diseases requiring transplantation especially renal, pancreatic, and liver disease and are a common cause of mortality after transplantation. Paradoxically, the presence of coronary artery disease in cardiac transplant recipients is less likely unless rejection is present. Although most patients undergoing these transplants will have had a full investigation of their cardiac status before transplantation, presentation for surgical procedures may occur sometime after the transplantation. Therefore, depending on the complexity of the surgery contemplated, more up to date investigation may be warranted. The presence and stability of diabetes must be known. As previously mentioned, systemic toxicity caused by immunosuppressive regimens, must also be considered before surgery.

Intraoperative

The overriding principles for anaesthetic management of transplant recipients are to reduce the degree of surgical stress, avoid injury to the transplanted organ and to protect against infection.

Reduce Injury to Transplanted Organ

It is vital to maintain adequate perfusion of the transplanted organ, and hypovolaemia must be avoided. Minimally invasive techniques are now available to optimize fluid balance and cardiac output and these are recommended in major surgery, where blood loss and fluid shifts are most likely. Perfusion pressures must be maintained for renal transplant recipients and direct arterial monitoring is indicated in these patients for all but the most minor procedures, especially where preoperative hypertension exists. Other measures should be used to maintain organ perfusion in addition to maintaining circulating volume, particularly in liver transplant recipients. These include the avoidance of high central venous pressures, high levels of PEEP and excessive doses of volatile anaesthetic agents. It is important to avoid high airway pressures and excessive airway manipulation to prevent organ injury in lung transplant recipients. Direct injury to cardiac function in heart transplant recipients is less likely during non-cardiac surgery.

The use of anaesthetic agents that are non-toxic to the transplanted organ is important, given reduced organ reserve. Large volumes of radiological contrast agents, aminoglycosides and non-steroidal anti-inflammatory drugs are best avoided in renal transplant recipients. Liver transplant function is rarely affected by anaesthetic drugs and, importantly, paracetamol in analgesic doses is not contraindicated.

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