Hydroxocobalamin hinders hemodialysis [abstract]
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Background: Hydroxocobalamin, an antidote used for cyanide exposure, has been FDA approved since 2006. It functions by binding cyanide, forming cyanocobalamin, which is then excreted in the urine. Its side effect profile is limited, however it can alter accuracy of laboratory measurements and impact hemodialysis. We present a patient whose hemodialysis treatment was delayed due to a false "blood leak" alarm following hydroxocobalamin administration.
Case Report: A 22 year-old male was running from police, and upon being caught he suffered a respiratory arrest. He was transported by ambulance with respirations assisted by bag valve mask. On arrival to the emergency department (ED) he had palpable pulses and Glasgow Coma Scale (GCS) score of 3. ED providers promptly intubated the patient and initiated other resuscitative measures. Vital signs included heart rate 70 beats/minute, blood pressure 76/50 mmHg, and O2 saturation 100%. Blood drawn from both peripheral IVs and a central line was bright red; venous blood gas revealed pH <6.8, pCO2 47.5 mmHg, pO2 245 mmHg, bicarbonate 6.4 mmol/L, and O2 saturation 97%. Lactate concentration was 16.4 mmol/L. With the constellation of low GCS, hypotension, bright red venous blood with high O2 content, and lactic acidosis, cyanide poisoning was considered and 5 gm hydroxocobalamin was given. Hemodialysis was initiated based on persistent acidosis, hyperkalemia, and renal insufficiency. The dialysis machine experienced an auto-shutdown due to a "blood leak" alarm. This alarm persisted and finally had to be manually overridden, at which point dialysis commenced. The patient ultimately deteriorated and expired 24 hours after initial presentation.
Discussion: A known effect of hydroxocobalamin administration is the discoloration of body fluids. During dialysis it also discolors the dialysate, creating a problem because of an internal safety measure in the dialysis machine. Normally blood passes on one side of a semi-permeable membrane and dialysate on the other. Photosensors monitoring the dialysate are meant to alarm and shut down the machine if red blood cells leak across the membrane. Hydroxocobalamin changes the light refraction in the dialysate enough to set off the alarm and cause the auto-stop. This "blood leak" phenomenon of hydroxocobalamin has been reported previously in a case report; in that case it appears as though manual override was not done in time to perform dialysis.
Conclusion: Hydroxocobalamin administration can induce a false "blood leak" alarm preventing hemodialysis until manually overriding the alarm. Providers caring for patients treated with hydroxocobalamin should be aware of this as inability to perform dialysis may make for poor outcomes.