Introduction
Donation after brain dead is considered in a patient who has suffered terminal illness and has been declared by clinical or instrumental based criteria. As the number of organ recipients continue to rise, it is important to have an efficient organization and management in organ procurement. In this organization anesthesiologist are involved in optimizing the donor and organ function, determining the suitability for transplantation, and preservation of the organs retrieved. Their role in the perioperative management of the donor may affect the outcomes of organ transplantation. Hence anesthesiologist plays a pivotal role in perioperative management of organ donors. Their role aims at counteracting the associated unique physiologic derangements and targets optimization of oxygenation of the organs intended for procurement.
Donor Optimization
Physiological changes after brain dead and its maintenance of homeostasis of all the organs are disturbed after brain death. It is essential to maintain tissue perfusion to enhance the quality of organ donated. Hence the anaesthesiologist who are trained in transplant knows the systematic organisation and thereby to enhance the quality of the organs procured. The proper system wise approach is essential to maintain appropriate hemodynamic stability in brain dead individual.
Cardiovascular System
- Loss of vascular tone and hypovolemia leads to profound hypotension. It is essential to maintain MAP>70mmHg. Vasopressin is necessary to maintain blood pressure
Pulmonary
- Patient are more prone for pulmonary edema as there is increased pulmonary capillary permeability. Invasive ventilation with Tidal volume 6-8 ml/kg (Predicted body weight) and PEEP 8 to 10 cmH20 is advised.
- IV fluids should be used judiciously.
Endocrine
- Hyperglycemia is common after brain death secondary to insulin resistance.
- Dysfunction in posterior pituitary is more often noticed than the anterior pituitary. This is due to compromised blood supply to cell bodies arising from deep supraventricular and paraventricular nuclei of hypothalamus, whose neurons supply posterior pituitary.
- Diabetes insipidus often noticed prior to diagnosis of brain death which will compromise perfusion to organs.
- Hypernatremia is encountered as a result of poorly controlled DI.
- Serum T3 also reduced after brain death but it does not contribute to hemodynamic instability yet it is supplemented as it can reduce the requirement of vasopressors. Vasopressin is used to control polyuria and SVR. Insulin infusion is used to maintain BG<180mg/dl
- Metabolic acidosis is also common finding which should be treated appropriately
Recipient Optimization
Pre-operative work-up
Pre-operative assessment identifies patients with scope for optimization and excludes patients with contraindications to transplantation. Though most patients will be adequately optimized, some would have travelled significant distances to the transplant center, so investigations may not be readily available. Some patients can also co-morbidities which requires further optimization. Coronary artery disease is the most common co-morbidities because of accelerated atherosclerosis. To keep all these in mind the holistic approach is essential for success of the transplant.
Investigation
Complete Hemogram
- Usually, patient will be anemic but they can tolerate till Hb 7g/dl. Blood loss is usually less than 500ml during transplantation but unanticipated blood loss might happen
- The raised WBC count is of concern, the source should be checked, most likely foci being chest, urinary tract or dialysis catheter
- Although platelet count may be normal, impaired platelet function can have increased bleeding time
ECG should be taken to check for underlying cardiac disease. If required ECHO can be sought.
Chest Xray is essential to correlate with fluid status and radiological status of heart disease
Medications
- Usually, patient will be refractory hypertensive taking multiple anti-hypertensive such Calcium channel blockers, alpha antagonists, beta blockers, ACE inhibitors
- High doses of ACE inhibitors should be withheld perioperatively, unless there is evidence of left ventricular dysfunction. In contrast, beta-blockers, aspirin, diuretics and statins should not be stopped perioperatively.
Dialysis
- Volume status, acid base balance and electrolyte imbalance shall be assessed by the blood samples before and after dialysis Patient on hemodialysis can have large fluid shifts and relative dehydration after dialysis compared to peritoneal dialysis. Hence, they are more prone for cardiovascular instability under anaesthesia
- It is essential to maintain adequate intravascular volume and cardiac output, so as to render optimum condition for graft implantation
Anaesthesia Techniques
Induction
Peripheral venous access is checked as there might be requirements for infusion of large volume of fluids or blood products Induction with Propofol is safe, thiopentone being another alternate option but its dose is reduced because of its plasma protein binding capacity. Fentanyl is safer and suitable choice of opioid. Morphine is typically avoided as its metabolite which has renal excretion can cause late respiratory depression
Muscle relaxant
CKD patients usually will have delayed gastric emptying. Hence Rapid sequence intubation is preferred, particularly in patients with autonomic dysfunction. RSI can be done with succinyl choline unless serum potassium is more than 5.5mEq. Rocuronium with dose 1-1.2mg/kg can be used whenever there is a contradiction for succinyl choline
Muscle relaxation can be maintained with Atracurium or Cis-atracurium whose elimination is organ independent
Monitoring
Central venous cannula is placed, to guide fluid administration Ultrasonographic assessment of the central vasculature before attempting cannulation is essential as there is a high incidence of pre-existing venous stenosis from the use of long-term indwelling hemodialysis catheters.
Femoral cannulation is avoided because of surgical vascular access concerns and increased incidence of catheter related infections.
Care of AVF is important by avoiding cannulating in that limb, wrapping it with cotton wool and careful positioning
Cardiac output is warranted in cases of expected cardiovascular instability.
Maintenance
Anaesthesia is maintained with either Sevoflurane or Isoflurane neither drug has been shown to be associated with postoperative renal dysfunction, despite peak plasma fluoride levels in excess of 50 μM litre−1 having been documented with use of sevoflurane.
If surgery goes on for more than 4 hours, desflurane can be used. TIVA is another alternative option.
Analgesia
Neuraxial opioids can provide adequate analgesia and reduce the dose of requirements of intra operative opioids.
NSAIDS are contra indicated in this patient.
Analgesics can be provided with iv paracetamol or fentanyl. The emerging USG guided (TAP) Transverse abdominis plane block is good alternative option now a days.
Goals
A mean arterial pressure (MAP) of 90 mm Hg is warranted for all patients undergoing renal transplantation (adjusted upwards for untreated hypertensives). This preserves residual renal function and reduces delayed graft function and the need for post- operative dialysis.
IV fluids are loaded to maintain adequate cardiac output and to optimize renal perfusion. There is an evidence that CVP of 12 to 14 cm H2O can lead to better graft survival rate. Balanced salt solution is used and colloid such as Hydroxyethyl starch should be avoided.
Mannitol can be used as an adjunct to intraoperative fluid therapy. Some centers infuse Mannitol 0.5 g/kg at the time of arterial clamp removal.
Blood transfusion is appropriate whenever there is necessary. The risk of transfusion includes hyperkalemia, increased blood viscosity, allosensitization, and transmission of infection.
Immunosuppressants are provided pre and intra operatively.
Methylprednisolone, a potent iv corticosteroid is administered. T cell depleting agent such Anti thymocyte globulin and alemtuzumab is also used.
Post-operative Management
Analgesia
Patient controlled analgesia (PCA) device is appropriate for pain control. Morphine and fentanyl can be used with increased risk of respiratory depression. Fluids are administered based on optimum MAP values. A dedicated post- transplant unit and trained staff are essential for early diagnosis and prevention of post operative complications.
Summary
Renal transplantation from cadaver is complex procedure involves multiple levels of organization in which anesthesiologist plays an important role. It is essential to maintain optimum physiological conditions in both cadaver and recipient so as to reduce the chance of graft failure. Among the members of the organ transplantation team, the anesthesiologist provides an holistic approach for the successful outcome.
Dr Karthik Raja
Dr Nirmalraj M