Infant with syndrome of inappropriate antidiuretic hormone secretion (SIADH) secondary to infant botulism

ABSTRACT

Objectives To become familiar with the appearance of SIADH in infant botulism Methods A-43 day old male with no significant history presented to the ED with difficulty latching and decreased activity for 2 days. At the ED, he was afebrile, hypoxic to 82% with moderate respiratory distress. Non-invasive positive pressure ventilation was started and he was placed on systemic antibiotics due to concern for sepsis. Initial labs showed positive rhinovirus/enterovirus, but otherwise normal CMP (Na 140 mmol/l), CBC, CRP, VBG, UA, negative COVID-19 and blood culture after 48 hours. CXR showed right upper lobe consolidation. Patient received a bolus of NS and maintenance IVF afterwards for less than 24 hours. He was placed on continuous orogastric feeds during the second day of hospitalization with his usual home formula regimen while weaning IVF. Patient started showing periorbital edema and his neurologic status deteriorated with hypotonia, diminished reflexes and lethargy. During the 5th day of hospitalization, he had a focal seizure of the left lower extremity that lasted about 2 minutes that promptly resolved after lorazepam administration. Labs sent during that episode were significant with Na of 113 mmol/l, urine Na of 94 mmol/l, urine Osm of 383 mOs/kg, and serum Osm of 271 mOs/kg consistent with SIADH, however, he did not have increased urine output. Rest of labs and imaging of the head and spine were normal. Patient received 0.9% NS and 3% hypertonic solution and sodium started to normalize over the course of 24 hours and remained stable during the rest of the hospital course on IV fluids. Due to profound hypotonia and aforementioned progressive clinical course while ruling out other possible causes with different specialties, concern for infant botulism was discussed and infectious disease was consulted. Recommendations included sending stool sample for botulism, avoiding the use of any aminoglycoside, and starting botulism immune globulin (BabyBIG) Results Patient received BabyBIG 50mg/kg about 10 days after initial admission and started improving immediately the day after administration. Neurologic status and respiratory effort subsequently started improving significantly and patient was able to be extubated after a week. Infant was eventually confirmed for botulism toxin A via stool Conclusions SIADH is thought to be due to reduced atrial filling from venous pooling in paralysis and is known to be a common complication of infant botulism and should be considered when patient has hyponatremia.