Popi arrived to MVMC in distress. The drive to MVMC had been punctuated by repeated vomiting episodes producing black fluid mixed with whole and partially chewed apricot kernels.
On presentation, Popi exhibited:
- Extreme lethargy
- Hind limb ataxia
- Marked hyperlactatemia (lactate: 10.1 mmol/L)
- Otherwise unremarkable bloodwork
Shortly after arrival, Popi’s condition escalated dramatically. She experienced a generalized seizure requiring midazolam intervention. Post-ictally, her neurological status was alarming:
- Opisthotonic posturing
- Dorsal strabismus (left eye)
- Poor responsiveness
- Persistent tachycardia (180-200 bpm despite fluid resuscitation)
Emergency interventions included mannitol administration and levetiracetam loading. A repeat lactate climbed to 12 mmol/L, raising significant concern despite normal imaging findings (negative FAST, unremarkable abdominal ultrasound, normal thoracic radiographs) and normal TEG and blood pressure (systolic 140 mmHg).
The clinical picture—persistent hyperlactatemia, metabolic acidosis, neurological deterioration, and refractory tachycardia—didn’t fit a typical ingestion pattern. The activated charcoal tablets, while unusual, wouldn’t explain this presentation.
The key was revisiting the exposure history: apricot kernels.
Apricot kernels contain amygdalin, which metabolizes to cyanide in the GI tract. Cyanide inhibits cytochrome c oxidase, blocking cellular respiration and causing histotoxic hypoxia—explaining the severe lactic acidosis despite adequate tissue perfusion and oxygenation.
Treatment Challenges
After consultations with both ASPCA Poison Control and the Northern New England Poison Center, the team confirmed suspected cyanide toxicity. The specific antidote, hydroxocobalamin, had to be sourced from a human hospital.
Supportive care continued:
- Oxygen supplementation
- IV fluid therapy
- Maintenance levetiracetam
- Respiratory monitoring for emerging tachypnea
The Antidote and Recovery
By the time hydroxocobalamin arrived (~80 mg/kg IV over 7.5 minutes), Popi had already begun showing spontaneous improvement—a testament to aggressive supportive care and the reversible nature of cyanide binding to cytochrome oxidase.
Post-antidote response:
- Dramatic improvement in mentation
- Resolution of tachycardia
- Lactate normalized to 1.9 mmol/L
- Return of normal appetite (described as “voracious”)
- Normal urination
- No further seizure activity
Minor complication: Popi developed erythema and pruritus of the ears posthydroxocobalamin administration—a known side effect managed successfully with diphenhydramine.
The Next day
The overnight transformation was remarkable. The critically ill, seizing dog from the previous evening was now bright, alert, and responsive with a healthy appetite. Her neurological status had completely normalized.
Clinical Pearls
- Think cyanide with apricot kernels: While rare, amygdalin-containing foods (apricot kernels, bitter almonds, cassava) can cause legitimate cyanide toxicity.
- Lactate tells the story: Severe, persistent hyperlactatemia without corresponding hypovolemia or hypotension should raise suspicion for histotoxic hypoxia from cyanide, carbon monoxide, or hydrogen sulfide.
- Supportive care saves lives: Even before antidote availability, aggressive oxygen supplementation and supportive care allowed time for spontaneous recovery.
- Hydroxocobalamin availability matters: Unlike the traditional cyanide antidote kit (amyl nitrite, sodium nitrite, sodium thiosulfate), hydroxocobalamin is safer and more effective but may require creative sourcing from human hospitals.
- Recovery can be rapid: With appropriate treatment, cyanide toxicity can reverse quickly as the toxin is metabolized and cellular respiration resumes.
Outcome
Popi recovered fully and was discharged the following day, proving once again that even unusual toxicities can have excellent outcomes with rapid recognition, appropriate consultation, and aggressive supportive care.
Criticalists Dr. Benevides and Dr. D’Ambrosio rose to the challenge of this peculiar toxicity case, demonstrating that successful patient management often requires thinking outside of the box and persistent, elevated care.