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Anesthetic Management of Cesarean Delivery for a Parturient with Ornithine Transcarbamylase Deficiency
Abstract Number: SU-62
Abstract Type: Case Report/Case Series
This is a case report of a 29yo G1P0 at 37 weeks gestation with ornithine transcarbamylase deficiency (OTCD) who presented for a scheduled cesarean delivery due to gestational hypertension. She was diagnosed with OTCD early in childhood due to lethargy associated with elevated ammonium. Other medical history includes sinus tachycardia attributed to pregnancy. Home medications include L-carnitine, citrulline, and glycerol phenylbutyrate. A multidisciplinary team developed a plan to admit the patient 24 hours prior to her scheduled cesarean section for medical optimization.
On admission, two 18-gauge intravenous catheters and a 20-gauge arterial catheter were inserted for medication administration and frequent blood draws, respectively. She was made NPO and started on an infusion of dextrose in normal saline. She was administered ammonia scavenging therapy – infusions of sodium phenylacetate/sodium benzoate and arginine. Her starting ammonia level was 14 (normal range 9-35 umol/L) and remained within normal limits throughout her hospitalization.
Spinal anesthesia was performed for her uneventful cesarean delivery. Pre-delivery arterial blood gas (ABG) showed pH 7.44, pCO2 27.2, pO2 105, HCO 20.5. Post-delivery ABG showed pH 7.40, pCO2 31.2, pO2 98, HCO 20.8. Her compensated metabolic acidosis was attributed to administration of ammonia scavenging treatment. Dextrose in normal saline infusion was continued post-op for 48 hours. The remainder of the hospital stay for the patient and newborn was uncomplicated.
OTCD is an X-linked recessive condition affecting the urea cycle, and is the most common urea cycle enzyme deficiency. Patients are unable to convert ornithine to citrulline, which is necessary for the removal of ammonia. Accumulation of toxic levels of ammonia can lead to altered mental status, lethargy, emesis, hypotonia, seizure, coma, neural tissue injury, and death.
In pregnancy, the placenta may ameliorate symptoms, but the metabolic stress of pregnancy carries risks of inducing a hyperammonemic crisis. A primary goal in management is to minimize the catabolic state, thus lowering the risk of a hyperammonemic crisis. Perioperative treatment includes lowering protein intake, providing dextrose to enhance anabolism, ensuring adequate hydration, correcting electrolyte imbalances, administering ammonia scavengers, and preventing infection. Neuraxial anesthesia may be beneficial in mitigating the sympathetic stress for OTCD patients undergoing cesarean delivery; and as this case report shows, can be done safely with a multidisciplinary team approach.
Ituk U, Constantinescu OC, Allen TK, Small MJ, Habib AS. Peripartum management of two parturients with ornithine transcarbamylase deficiency. Int J Obstet Anesth. 2012 Jan;21(1):90-3.
Auron A, Brophy PD. Hyperammonemia in Review: Pathophysiology, diagnosis, and treatment. Pediatr Nephrol. 2012 Feb;27(2):207-22.