C53-23 The Unsung Hero in Phenobarbital Overdose - Hemodialysis

Abstract Introduction Phenobarbital, a long-acting barbiturate, is one of the leading causes of fatal poisoning that can cause coma, circulatory collapse, and respiratory arrest. Supportive care and multiple doses of activated charcoal (MDAC) are mainstays of treatment. However, in severe cases refractory to MDAC, intermittent hemodialysis (HD) can prove beneficial in reducing plasma barbiturate burden. Case description A 58-year-old lady with history of depression presented as a transfer for intentional overdose of 160 units of 32.4 mg phenobarbital tablets. At the outside facility, naloxone and flumazenil were given. During attempts to intubate, patient developed bradycardia and cardiac arrest requiring 20 mins of resuscitation. Patient presented on ventilatory support at 100% FiO2, 8 PEEP, needing norepinephrine infusion at 25 mcg/min. On exam, she was unresponsive to painful stimuli with dilated and reactive pupils. Labs showed, WBC 25, ABG 7.24/46.3/99.6, bicarb 20 with anion gap acidosis, glucose 329, CK 52 and normal hepatic/renal functions. Tox screen was negative. Phenobarbital level was 127µg/ml. EKG unremarkable. CXR showed possible pneumonia. After informing poison control, 50 g of activated charcoal (AC) was administered via OGT and bicarbonate drip initiated for urinary alkalinization. As pressor requirements improved, AC was repeated at 4 hours and further doses deferred. On repeat testing, phenobarbital levels increased to 140µg/ml. Hence, hemodialysis was pursued. After two dialysis sessions levels dropped to 74µg/ml and 37µg/ml. Regardless, the clinical picture was concerning due to absence of spontaneous arousal. MRI brain confirmed findings of hypoxic ischemic injury, considering which family opted comfort measures. Discussion Serum phenobarbital level 80 µg/ml can be fatal. MDAC is the first-line treatment, proven superior to urinary alkalinization in improving renal clearance. In our case despite timely measures, phenobarbital levels worsened. Although levels improved effectively with HD, patient outcome was poor due to ensuing hypoxic brain injury. Consistent with The EXTRIP (Extracorporeal Treatments in Poisoning) workgroup recommendations, we endorse close barbiturate level monitoring and early initiation of HD in severe toxicity with high/worsening serum concentrations despite MDAC treatment. This abstract is funded by: None