Here, we report a case of LDLT in a patient with CPS1D, which was a congenital metabolic dysfunction of the urea cycle. Any enzymatic defects in the urea cycle inhibit the production of essential amino acids from arginine and cause nitrogen accumulation and hyperammonemia in patients with CPS1D. According to the guidelines for UCD treatment, dextrose and arginine should be administered to suppress protein catabolism and avoid hyperammonemia, in addition to low-protein meals [1, 3, 4]. Although LT is indicated as a final treatment in patients with severe UCD, hyperammonemia is caused by surgical stress . Therefore, perioperative anesthesia management is suggested to suppress the increase in serum ammonia levels during the perioperative period.
Serum ammonia levels should be checked frequently to avoid hyperammonemia during LDLT. Some reports have shown that serum ammonia level is an essential parameter for evaluating transplanted liver function . In adult LDLT for end-stage liver dysfunction, serum ammonia increases transiently during the anhepatic phase and returns to normal levels after reperfusion when the transplanted liver starts reworking. The normalization of serum ammonia indicates a well-functioning liver graft in the acute phase of LT, and  increased serum ammonia over 200 mcmol/L causes cerebral edema and intracranial hypertension; therefore , hyperammonemia should be avoided in such patients. In our case, serum ammonia was measured every 2 h, and critical hyperammonemia was not observed during surgery. Some reports have suggested that serum ammonia levels should be used as a standard monitor for LT [3, 9, 10].
No clinical guidelines exist for anesthetic management in pediatric LT with UCD, and our perioperative anesthesia management plan was based on the guidelines for UCD and hyperammonemia, such as the Middle East Hyperammonemia and Urea Cycle Disorders Scientific Group and the Japanese Society for Inherited Metabolic Disease [1, 4, 11]. Guidelines indicate that the proper administration of dextrose and l-arginine is effective in preventing hypercatabolism. If hyperammonemia occurs, calorie intake should be increased up to 110% of the standard daily intake with dextrose to reduce the endogenous protein consumption and l-arginine production . Following the guidelines, we planned to increase dextrose intake to 100 kcal/kg/day with l-arginine in cases where serum ammonia was critically increased in the perioperative period. Continuous renal replacement therapy (CRRT) has also been used to treat severe hyperammonemia, although its effectiveness during surgery has not been reported till date. Intraoperative CRRT induction should be suggested if serum ammonia exceeds 500 mcmol/L and any medical treatment is ineffective in controlling serum ammonia . Fortunately, hyperammonemia did not occur and additional dextrose intake or CRRT was not performed in our case.
According to the guidelines, dextrose with l-arginine was continuously administered during the operation to avoid hyperammonemia. However, it is unclear how to decrease and complete dextrose administration. The transplanted liver begins to function, and the urea cycle is functional following reperfusion. In addition to serum ammonia, platelets, and lactate are useful markers of transplanted liver function . In this case, the normalization of serum ammonia, platelets, and lactate might have indicated the possibility of decreasing dextrose administration. Dextrose and l-arginine administration were continued during surgery, even if serum ammonia started to decrease after reperfusion of the transplanted liver. When serum ammonia, platelet, and lactate levels were maintained at normal levels in the ICU, we decided to complete dextrose administration. Serum ammonia levels were within the normal range without dextrose after LT. Although no reports have shown an optimal program to decrease dextrose administration after LT, serum ammonia, platelets, and lactate levels might be relevant markers to indicate a decrease in dextrose after LT in CPS1D patients.
Some reports have shown that a smaller amount of blood loss and blood infusion contributes to a good outcome in LT . Blood products contain serum ammonia, and blood transfusions increase the serum ammonia levels [15, 16]. Furthermore, blood transfusions are associated with increased graft failure and mortality rates [17, 18]. Compared to patients with biliary atresia, liver function and coagulation activity were generally maintained in children with CPS1D. In our case, liver function and coagulation activity were preserved, and the blood infusion required was only 13 mL/kg of red blood cells. Therefore, a low-dose blood infusion may contribute to a good outcome in LDLT.
In conclusion, we suggest anesthesia management with administration of dextrose to avoid hyperammonemia during LDLT in patients with CPS1D.