Pediatric Transplantation

Waldo Concepcion MD¹

Amy E. Gallo MD¹

Julianne Mendoza MD²

Louise Furukawa MD²

Gregory B. Hammer MD²

¹SURGEONS

²ANESTHESIOLOGISTS

PEDIATRIC RENAL TRANSPLANTATION

SURGICAL CONSIDERATIONS

Description: Renal transplantation is the therapy of choice for children with end-stage renal disease providing freedom from dialysis and improvement in growth. Preemptive transplantation is recommended when possible to minimize loss of growth potential and currently accounts for 25% of transplants. The source of the renal allograft may be a cadaveric (40%), living related, or living unrelated donor. More than 90% of donors are adults.

A right curvilinear incision, starting at the pubic symphysis and extending to just below the ribs, is the approach most commonly used even for children as small as 10 kg. The donor renal artery and vein are anastomosed directly to the recipient aorta and vena cava, respectively. An adult-sized kidney may occupy the majority of the right upper quadrant in a small recipient. Meticulous attention to the positioning of the kidney will prevent kinking or twisting of the donor vasculature. This may require mobilization of the right lobe of the liver or even hepatectomy in some cases and almost always a right nephrectomy in small children. The donor kidney can be temporarily taken out of ice and placed into the recipient to determine the best site for the anastomoses. In this manner, the vessel length necessary to fashion straight, yet tension-free anastomoses can be determined. It is important to avoid redundancy in the vessels and ensure a straight line from the renal hilum to the aorta and vena cava without the hooking of one vessel over another. The venous anastomosis is fashioned first. The vena cava is clamped, and an appropriate size cavotomy is made. The renal vein is sutured to the vena cava in an end-to-side fashion. A small vascular bulldog clamp is then applied to the renal vein above the anastomosis to allow for removal of the vena caval clamp and reconstitution of lower extremity venous return to the heart. Heparin is administered, and the aorta is then cross-clamped proximal and distal to the aortotomy. An end-to-side anastomosis is fashioned between the renal artery and aorta, taking care to interrupt the front wall sutures and prevent the purse-string effect of a running suture. Warm ischemia can be minimized during this time by intermittently placing iced slush around the kidney. It is critically important to achieve substantial hypervolemia prior to reperfusion of the adult-sized kidney (ASK) because reperfusion will cause an immediate drain of a large portion of a child’s relatively small blood volume into the ASK. This necessitates bringing the central venous pressure to approximately 10-15 cm H₂O before reperfusion with a combination of crystalloid and colloid to minimize tissue edema. As prophylaxis against ischemia-reperfusion injury, a single dose of iv mannitol is administered at the time of graft revascularization, and low-dose dopamine is also initiated. Adequate renal blood flow to an ASK cannot be obtained in children without maintenance of a hypervolemic state, and infants and small children are frequently kept intubated for 24 to 48 h postop to maintain control of their respiratory function while large volumes of fluid are administered.

The type of ureteral reimplantation depends on the quality of the recipient bladder. An extravesicular ureteral reimplantation can be considered in a healthy bladder of adequate size. This requires distending the bladder with GU irrigant via a three-way Foley catheter. The bladder is reflected medially to accomplish the implantation near the postero lateral portion of the bladder with the ureteral orifice located close to the trigone. The detrusor muscle is divided, and a mucosal-to-mucosal anastomosis is fashioned between the bladder and the donor ureter over a ureteral stent. The detrusor muscle is reapproximated over the ureter for an adequate length to create an antireflux valve. If the bladder is of small capacity or defunctionalized, a transvesicular approach to ureteral reimplantation is required. A bladder cystotomy is made at the dome, and the transplant ureter is brought into a shallow, mucosa-denuded, rectangular trough extending from a superiorly placed ureteral hiatus distally to the trigone. The ureter is then spatulated and directly sutured to the urinary mucosa over a ureteral stent. The ureteral stent is sutured to a cystotomy tube brought out through a separate incision in the bladder for easy removal of the urethral catheter with its associated discomfort, while ensuring adequate drainage and prevention of clot obstruction. The cystotomy is then closed and the kidney inspected for perfusion and hemostasis.

▪ SUMMARY OF PROCEDURE

Position	Supine
Incision	Lower quadrant curvilinear
Special instrumentation	Self-retaining retractor Vascular instruments Foley catheter (three-way)
Unique considerations	Recipient hypervolemia (CVP 10-15 mm H₂O) Mannitol, Furosemide Dopamine Immunosuppression Potassium-free iv fluids
Antibiotics	Cephalosporin
Surgical time	3-5 h
EBL	Minimal
Postop care	Maintain hypervolemia (CVP > 10 mm Hg) Maintain adequate SBP > 120 mm Hg with dopamine Maintain high UO with a combination of iv fluids + Lasix. Goal 150-200 cc/h ICU postop Transplant ultrasound postop
Mortality	< 2%
Morbidity	Primary nonfunction: 2.6% Vascular thrombosis: 10.3% Renal artery stenosis: 0.7% Other technical: 1.3% Bleeding: 2% Wound infection: 5%
Pain score	7

ANESTHETIC CONSIDERATIONS FOR KIDNEY TRANSPLANTATION IN INFANTS AND CHILDREN

PREOPERATIVE

Patients presenting for renal transplantation tend to fall into two groups: (a) children in the infant/toddler age group who suffer from congenital syndromes (congenital nephrotic syndrome, severe polycystic kidney disease, obstructive uropathies, FSGS) or (b) the older child who may have a variety of conditions including severe autoimmune nephropathies. These children are often the recipients of a living-related transplant, and as such, the surgery proceeds as a somewhat elective procedure. Most patients have been on a well-established regimen of peritoneal or hemodialysis.

Airway	Some renal conditions may have associated syndromes and dysmorphia. A thorough airway examination as well as perusal of old anesthetic records should reveal any potential airway problems.
Respiratory	Patients with autoimmune diseases (e.g., lupus) may have pulmonary involvement. Any patient presenting with signs and symptoms of URI should be allowed adequate time for resolution of heightened airway reactivity. Children born with large polycystic kidneys may have pulmonary hypoplasia. Tests: Pulmonary function tests, if indicated from H&P
Cardiovascular	Relatively long-standing hypertension and LVH can be seen in this patient population and may require bilateral nephrectomies prior to or during the transplantation. Adequate control of hypertension should be achieved during the preoperative admission period. Tests: EKG, echocardiogram
Gastrointestinal/ hepatic	Patients with polycystic kidney disease may also have hepatic dysfunction and require future liver transplantation. Patients with congenital nephrotic syndrome tend to be hypoalbuminemic and may be on continuous albumin infusions. Tests: Albumin, LFTs, PT, PTT if applicable
Renal	Most patients are well maintained on hemodialysis or peritoneal dialysis. Other common electrolyte abnormalities are metabolic acidosis, hypocalcemia, and hypermagnesemia. Be aware of current weight relative to dry weight as some patients may present with dehydration in the postdialysis period. Tests: Serum electrolytes, BUN, and creatinine
Hematologic	Anemia and platelet dysfunction are commonly seen. Tests: CBC, platelet count
Premedication	Most children will require a premedication to allay separation anxiety. Oral midazolam 0.5-0.75 mg/kg or iv midazolam 0.1 mg/kg (maximum 2 mg) is usually sufficient.

INTRAOPERATIVE

Anesthetic technique: GETA.

Induction	An inhalational induction with standard monitors will work well in patients without prior iv access. Patients in the infant/toddler age group may have significant venous access problems, and the hemodialysis catheter (if present) may be used provided that sufficient heparinized blood has been aspirated from the dead space of the catheter lumen. Use of muscle relaxation once iv access has been established is necessary for adequate surgical visualization and mobilization. If recently dialyzed, pt may be hypovolemic. Induction of immunosuppression begins in the preop period and continues intraop. Care should be taken to discuss with the surgeon and nephrologist which immunosuppressive agents should be given intraop. If thymoglobulin is used, a dedicated central line port is needed and premedication with iv solumedrol (1 mg/kg), diphenhydramine (1 mg/kg), and acetaminophen (15 mg/kg) is initiated prior to infusion. Solumedrol (10 mg/kg) is given just prior to unclamping of the renal artery upon reperfusion.
Maintenance	Standard balanced anesthetic maintenance. Titration of a long-acting narcotic is recommended, although high doses of meperidine should be avoided due to accumulation of normeperidine. Adequate muscle relaxation is especially important in the patient under 20 kg to facilitate surgical exposure. Any coughing or straining can result in vascular injury to the renal allograft. Significant hypothermia can be seen when the iced organ is placed in the peritoneum. Tachycardia is frequently seen following reperfusion of the ASK due to the relatively large vascular volume it can accommodate and the low vascular resistance. Urine output should be closely monitored postreperfusion.
Emergence	Most children weighing < 20 kg remain intubated in anticipation of large fluid shifts due to volume loading. Extubation in the operating room is usually feasible for patients larger than 20 kg. All patients recover in the ICU for monitoring of hemodynamics and urine output.
Management of reperfusion	Blood and fluids: Maintenance IV fluids without K⁺ Volume loading Albumin loading	Preop fluid status is variable. Maintenance fluids should be devoid of K⁺. Volume loading to a CVP of 15-20 or titrated to renal allograft turgor postreperfusion is usually requested by the surgeon for infants and small children receiving ASKs to avoid stasis and thrombosis within the allograft. Albumin boluses (10 mL/kg) or PRBC transfusion may be needed to achieve goal CVP. Dopamine
	Blood may be required Warm all fluids Promoting diuresis Pressor support	(3-5 mcg/kg/min) is started to increase perfusion pressure to the allograft. In addition, epinephrine infusion may be needed to achieve systolic blood pressure of greater than 120 mm Hg necessary for the ASK. For patients > 20 kg, the magnitude of volume loading is decreased to a goal CVP of 10-15, which can usually be achieved with crystalloid and albumin alone. Constant communication with the surgical team regarding allograft turgor after reperfusion will assist in guiding fluid management. Consider use of TEE in patients with hypertensive cardiomyopathy to guide volume loading to avoid pulmonary edema. Diuresis is promoted just prior to reperfusion of the renal artery with mannitol (0.5 mg/kg) and furosemide (1 mg/kg). Goal urine output after reperfusion is 5-10 mL/kg/h.
Monitoring	Standard Monitors (see p. D-1) Arterial line CVP (2-3 lumen) Hct/electrolytes Urine output (Foley catheter) PIP Temperature control	Adequate blood pressure to perfuse the ASK is crucial as is sufficient preload (CVP 10-15) prior to reperfusion. Invasive arterial blood pressure monitoring is necessary to monitor beat-to-beat variation in perfusion pressure and guide in titrating volume and vasoactive infusions. CVP monitoring is critical to management of volume status. Electrolyte derangements may occur during the case 2° large volume replacement with albumin or blood products. ↓ Ca⁺⁺ and ↑ K⁺ should be corrected. Hematocrit goal after reperfusion is above 25% though caution should be taken with regard to transfusion to avoid renal artery thrombosis. Urine output is closely monitored after ureteral reimplantation. Peak inspiratory pressures should be closely followed as risk of pulmonary edema is increased from volume loading. Care should be taken to avoid hypothermia that may occur following placement of iced allograft into abdominal cavity.
Complications	Ventilatory difficulties Electrolyte abnormalities Hypotension/inadequate renal perfusion Low urine output