Tuesday, March 23, 2021

Anesthesia for Renal Transplantation Case File

Posted By: Medical Group - 3/23/2021 Post Author : Medical Group Post Date : Tuesday, March 23, 2021 Post Time : 3/23/2021
Anesthesia for Renal Transplantation Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 50
A 58-year-old dialysis-dependent diabetic woman is scheduled to receive a living related kidney transplant from her 40-year-old brother. She has chronic renal failure from diabetes, has been on chronic dialysis for the past 5 years, and was dialyzed yesterday. The patient’s medical history includes hypertension, diabetes, and hepatitis B. Her medications include metoprolol, furosemide, insulin, calcium carbonate, ferrous sulphate, epogen, and sevalamer. On physical examination, the patient is 5 ft 7 in, 55 kg, and her physical examination is otherwise normal. Her laboratory results show: Na 135 mEq/L, K 4.9 mEq/L, pH 7.32, and Hct of 29%. Her ECG is normal. The patient’s brother is healthy, with the exception of gastric reflux and a hiatus hernia. His laboratory results are normal, and his Hct is 45%.

➤ What are the anesthetic considerations for patients each of the above?

➤ How are the kidney donor and recipient typically managed?


ANSWERS TO CASE 50:
Anesthesia for Renal Transplantation

Summary: A living sibling is donating a kidney to his diabetic sister with kidney failure.
Anesthetic concerns: Renal transplant donors are typically anxious. In addition to the concerns with positioning, such as the potential for nerve compression and pressure sores, their general anesthetic is similar to that for any other healthy patient. Renal transplant recipients typically have comorbid illnesses and may benefit from invasive monitoring. Bleeding may be exacerbated because of platelet dysfunction. Renal recipients require immunosuppressant medications to prevent rejection and possible diuretics to facilitate urine production.

Management of donor: General endotracheal anesthesia with muscle relaxation is usually employed. Since living organ donation is an altruistic act of the highest order, every attempt should be made to provide optimal postoperative analgesia.

Management of recipient: General endotracheal anesthesia with consideration of central and arterial monitoring, and judicious fluid and electrolyte management is vital.


ANALYSIS

Objectives
1. Understand the differences in the surgical approach for renal donor and recipient.
2. Become familiar with the anesthetic considerations and plans for each patient.
3. Become acquainted with the postoperative issues associated with renal transplantation in both donors and recipients.


Considerations
Living donors are often quite anxious. A reassuring approach and anxiolytic therapy are important to the donor. It is important to verify that they are volunteering freely and understand the risks of surgery prior to proceeding.

The recipient’s dependence on dialysis lends challenges to fluid management. Most patients undergo dialysis the day before the procedure, resulting in relative and sometimes significant hypovolemia. In addition, electrolytes, and particularly potassium vary markedly depending upon the timing of the most recent dialysis, so the timing of dialysis should be verified and a recent set of postdialysis electrolytes obtained. Failure to dialyze or inadequate dialysis in the preoperative period can predispose to volume overload and electrolyte imbalances such as hyperkalemia.

The recipient’s diabetes requires monitoring of blood sugars in the perioperative period. Given her end-stage nephropathy, it is reasonable to assume that diabetes has also affected other organ systems and could lead to gastropathy, neuropathy, and autonomic instability, all of which could complicate the anesthetic.


APPROACH TO
Anesthesia for Renal Transplantation

DEFINITIONS
LIVING RELATED RENAL TRANSPLANT: A kidney is removed from the
donor who is otherwise healthy and related to the recipient. Living donors may
also be unrelated. The other source for donors is cadaveric, where an organ is
donated after death.

DONOR: The person giving a kidney to the recipient. Live donors should be healthy and have normal renal function.

DIALYSIS-DEPENDENT RENAL FAILURE: When renal function falls below 10% of normal, patients typically start dialysis to aid in elimination of fluids, urea, potassium, and replace other kidney functions. Hemodialysis is conducted through a large central catheter (Permcath) or AV fistula. Some patients undergo peritoneal dialysis, in which fluid is introduced into the peritoneal cavity and fluids and waste products are filtered through the peritoneal membrane and intermittently drained or exchanged. Hemodialysis is conducted three times a week, whereas peritoneal dialysis is either done continuously or at least nightly.

DONOR SURGICAL APPROACH: Donor receives either a laparotomy or a “hand assisted” laparoscopic nephrectomy under general anesthesia. The donor kidney is dissected carefully and separated from the bladder. It is isolated from the blood supply and removed from the donor.

RECIPIENT SURGICAL APPROACH: Recipient has donor kidney implanted under general anesthesia. The new kidney is placed in the preperitoneal space in the pelvis and generally anastomosed to the iliac vessels. The native kidneys are left in place.


CLINICAL APPROACH
The donor’s preoperative evaluation is usually quite straightforward, and in most ways, does not significantly differ from that of a normal, healthy patient. The evaluation examines their renal function (creatinine, GFR, urinalysis), cardiopulmonary status (history, exercise tolerance, possible ECG, and chest x-ray), compatibility (blood type and antigen match to the recipient), and suitability (emotional and mental status, freedom from coercion to donate).

The recipient requires verification of donor compatibility (blood type and antigen matching), assessment of cardiopulmonary status, and volume and electrolyte status. Patients are often chronically ill. They may be anemic and acidotic, but both these electrolyte disturbances are usually well tolerated. Uremia is also associated with coagulopathy due to platelet dysfunction, which can increase bleeding during surgery. Preoperative tests of particular interest to the anesthesiologist include an ECG, potassium level, complete blood count, and type and screen.

Since donors are healthy patients, standard monitors and a large-bore intravenous are placed prior to the surgery. A general anesthetic is utilized for an open or laparoscopic nephrectomy, and muscle relaxants are administered to facilitate the surgical approach. Fluids are given liberally to maintain urine output. Both laparoscopic and open donor nephrectomies are typically completed in a lateral position, so positioning and padding is important to prevent intraoperative ulcerations and nerve palsies. In addition, if the kidney bar is raised, compression of the inferior vena cava may result in hypotension. Pain control in the postoperative period can be provided with a patient-controlled analgesia (PCA) administration of narcotics, or an epidural. PCA is usually appropriate for laparoscopic approaches, but open procedures may require more aggressive postoperative analgesia.

The recipients are chronically ill, and particularly if the renal failure is the result of diabetes, may have many comorbidities. Decisions can be challenging, and should be based on individual patient characteristics. Most centers utilize general anesthesia for recipient nephrectomies, though some use spinal or combine spinal-epidural techniques as primary anesthetics. The anesthetic considerations in this kidney recipient include likely gastroparesis or reflux which may increase the risk of aspiration, electrolyte abnormalities, particularly with potassium, anemia, and the altered metabolism and excretion of anesthetic drugs in patients with end-stage renal disease.

The choice of induction agents varies with coexisting disease and volume status postdialysis. If volume status or cardiovascular issues are present, etomidate may be preferable since it causes minimal changes in cardiovascular function. Propofol or thiopental may also be used, bearing in mind that these agents decrease SVR, resulting in hypotension in normal patients. These effects would be predicted to be amplified in the hypovolemic patient.

The choice of muscle relaxants is determined by the potassium level and the patient’s renal disease. Serum potassium levels vary widely in the freshly dialyzed patient when compared to the patient ready for dialysis. In addition to the risks associated with hyperkalemia in general, hyperkalemia may put the patient at risk of hyperkalemic arrest if succinylcholine is administered. Succinylcholine increases potassium levels by as much as 0.5 mEq/L. So in patients with potassium levels greater than 5.5 mEq/L or evidence of hyperkalemia (peaked T waves on ECG), it is best to avoid succinylcholine. Other neuromuscular blockers with renal clearance such as rocuronium or vecuronium may have prolonged effect in renal failure patients, so dosing with caution and titrating to effect are advisable. Cisatracurium is degraded by Hoffman elimination, so its duration of action is not altered in patients with renal dysfunction. Thus, cisatracurium is the relaxant of choice in patients with end-stage renal disease.

Inhalational agents are often used for maintenance of anesthesia, though their metabolism to compound A and release of fluoride ions limits choices. Enflurane is generally avoided due to risk of nephrotoxicity. Sevoflurane use carries a theoretical risk of compound A–induced nephrotoxicity. Fresh gas flows in excess of 2 L/min should minimize this risk with Sevoflurane. While demonstrated in animal studies, this topic remains controversial in human subjects.

Analgesia is typically provided by narcotics. Morphine and meperidine have active metabolites which require renal excretion, and so should be used with caution. Other narcotics such as fentanyl and sufentanil are reasonable alternatives. Epidural catheters are not typically used in kidney recipients since these patients are immunosuppressed and thus susceptible to infection, and bleeding diatheses are often present.

Both lactated Ringer and normal saline are acceptable choices for fluid administration. Due to concerns over the inability of these patients to clear potassium, some clinicians elect to use normal saline. However, large volumes of normal saline could cause a metabolic acidosis, resulting in potassium migration out of cells.

In addition to standard monitors, arterial access can be beneficial for hemodynamic monitoring and frequent blood sampling. This need must be balanced against the fact that, if the transplant fails, the patient may require subsequent AV fistulas. Thus, preserving arteries from possible injury may be of future benefit. Also, the radial artery should not be cannulated on the side of an existing AV fistula, as the readings may not be an accurate representation of arterial blood pressure, and the blood drawn may be mixed arterial and venous due to the presence of a shunt.

A central venous line may serve a variety of purposes in this patient population. It can provide an estimate of volume status which can be helpful given the frequent volume changes with hemodialysis and superimposed NPO status. It is also helpful to ensure euvolemia or even mild hypervolemia after the transplanted kidney is implanted to provide adequate perfusion and avoid ischemia to the implant. Central venous access may be helpful in chronically ill patients to provide venous access for the administration of immunosuppressant regimens, and frequent blood sampling. However, renal failure patients have often had multiple central lines placed for dialysis, rendering central venous access difficult due to thrombosis or scarring. Ultrasound is helpful in identifying and cannulating vessels in this difficult patient population. In the case of patients who come to surgery with a central dialysis catheter in situ, it may also be possible to utilize the indwelling catheter. But since dialysis lines are flushed with concentrated heparin (5000 units/cc), care must be taken to withdraw all the heparin from the catheter to avoid inadvertent anticoagulation. The catheter also should be accessed in sterile fashion to avoid risk of infection. A discussion should be undertaken with the surgical team prior to using this approach.

During the maintenance of anesthesia, close attention must be paid to volume status, electrolyte balance, and hemodynamics. Although volume expansion is preferable once the new kidney is implanted, sometimes pressors such as phenylephine are required for blood pressure support prior to its implantation. In patients with significant cardiac dysfunction, it may be necessary to employ ionotropes such as dopamine or epinephrine to improve cardiac output and deliver an adequate blood flow to the transplanted organ. At the transplant of the new kidney, steroids and other immunosuppressants are given to avoid rejection, while diuretics such as mannitol (osmotic) and furosemide (loop) are often used to facilitate urine production and avoid acute tubular necrosis (ATN). Muscle relaxants should be closely monitored with a goal of reversal and extubation in the operating room.

Postoperative care is typically centered around immunosuppression, analgesia, and plasma volume. CVP and urine output are monitored closely to ensure adequate hydration and urine output. Intravenous fluids are typically aggressive and titrated to maintain supra-normal urine output in the early postoperative period and avoid acute tubular necrosis (ATN). Because the most common site of implantation is the pre-peritoneal space, there is usually less pain in recipients than donors. Narcotics, delivered by patient-controlled analgesia (PCA) are usually adequate for postoperative analgesia.


Comprehension Questions

50.1. Compared with kidney donors, which of the following is most accurate for kidney transplant recipients ?
A. Do not require preoperative dialysis
B. Have more comorbid medical conditions
C. Have normal renal function
D. Require less intraoperative monitoring
50.2. Which of the following is most accurate regarding patients undergoing dialysis?
A. Patients undergoing dialysis typically have stable circulating blood volumes due to the dialysis.
B. Patients undergoing dialysis need to have their serum potassium measured just prior to the procedure.
C. Because of the dialysis, their intravenous access is usually easy.
D. Patients undergoing dialysis must be sufficiently stable to be transported to a dialysis unit.


ANSWERS
50.1. B. Kidney transplant recipients typically have more comorbid medical conditions such as diabetes or hypertension. Their renal function is impaired and they require more intraoperative monitoring. Renal failure patients undergo dialysis, whereas donors do not.

50.2. B. Dialysis in the patient with renal failure is associated with significant fluxes in serum potassium concentrations. If the patient is near his or her routinely scheduled dialysis time, the serum potassium can exceed 6.0 and even 7.0 g/dL. Similar fluctuations also occur in blood volume, even from relative hypovolemia to hypervolemia. However, in patients immediately postdialysis, hypovolemia should be anticipated. Patients on dialysis often have an arteriovenous fistula(s) in their upper extremity. Because only one arm can be used for blood sampling, their intravenous access is usually difficult. Being sufficiently stable to be transported to a dialysis unit is not a prerequisite for dialysis. Peritoneal dialysis is easily conducted in the ICU setting. 


Clinical Pearls
➤ Donors require no special monitoring. Key points include anxiolysis, adequate hydration, and analgesia.
➤ Recipients typically have numerous comorbidities and may benefit from invasive monitoring.
➤ Recipients are immunosuppressed and may require diuretics and/or mannitol to facilitate urine production.
➤ While both surgeries are typically performed under general endotracheal anesthesia, the level of anesthetic complexity is very different between the two.

References

Miller R. Solid organ transplant. Miller’s Anesthesia. 6th ed. Philadelphia, PA: Churchill Livingstone;2005: 2234-2243. 

O’Hara J, Cywinski J, Monk T. The renal system and anesthesia for urologic surgery. In: Barash P, Cullen B, Stoelting R, eds Clinical Anesthesia. Philadelphia, PA: Lippincott Williams and Wilkins;2006: 1013-1025. 

Sarin Kapoor H, Kauri R, Kaur H. Anesthesia for renal transplant surgery. Acta Anaesthsiologica Scandinavica. 2007;51:1354-1367.

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