TYK253
A 6 year old, 23 kg female with Crouzon syndrome presents to the ICU after monobloc fronto-orbital advancement, which was uneventful. Volume status was maintained intraoperatively with 1.8 liters LR, 900 mL PRBCs, and 750 mL FFP. On POD 1, urine output is 10 mL/hr. Morning labs reveal Na 128, K 3.9, Hb 10.1, HCO3 21, urinary osmolality > 100, BUN 9, Creatinine 0.5. Vital signs show HR 92, invasive BP 117/71, CVP 12. What is the first most likely course of treatment?
a) fluid administration with normal saline
b) fluid restriction
c) administration of 3% hypertonic saline
d) desmopressin
e) none of the above
Answer
Answer b. Hyponatremia after craniofacial surgery is a potential complication and can be seen within the first several postoperative days. Potential causes include SIADH, cerebral salt wasting (CSW), and dilutional hyponatremia secondary to administration of hypoosmolar fluids. This patient presents with oliguric hyponatremia and the urine is inappropriately concentrated. The patient appears to be euvolemic or slightly hypervolemic with high-normal arterial and central venous pressures and relatively low pulse; therefore, SIADH is the most likely diagnosis. This syndrome is associated with hypersecretion of antidiuretic hormone (ADH), which is normally responsible for reabsorption of water in the collecting ducts and distal convoluted tubules via increased expression of aquaporins. Etiologies of SIADH include pain, intracranial pathology, neoplasms (especially small cell lung cancer), and various drugs. The mainstay of treatment is fluid restriction to reduce total body water, but in demeclocycline, which is a potent inhibitor of ADH, may be used in refractory cases. Cerebral salt wasting syndrome is also associated with hyponatremia, but in contrast to CSW is associated with hypovolemia, polydipsia, and polyuria with random urine sodium concentration <100 mEq/L. Primary treatment modalities include fluid resuscitation and sodium supplementation. Desmopressin or DDAVP is the treatment of choice for central diabetes insipidus, which is characterized by hypernatremia, polydipsia and polyuria with extremely dilute urine (i.e., low specific gravity and urine sodium concentration) due to deficiency of antidiuretic hormone. Hypertonic saline may be used in hyponatremia, but must be used with extreme caution and typically reserved for extreme cases or in symptomatic patients (seizures, altered mental status, coma). Overly aggressive sodium repletion (> 12 mEq/L per day) carries the risk of central pontine myelinolysis with irreversible neurologic injury. For more detailed explanation of endocrine emergencies, please see Book 7, Chapter 2 in this series.
Notes
- This question originally printed in the Pediatric Anesthesiology Review Topics kindle book series, and appears courtesy of Naerthwyn Press, LLC.