Understanding Cyanide Poisoning in Burn Victims

In today’s episode, we explore a tragic but educational case involving a 15-year-old girl who suffered severe inhalation injury following a house fire. While heroically rescuing her brother and his friend, she endured prolonged cardiac arrest and severe multi-organ dysfunction. We’ll focus on the pathophysiology, investigation, and management of inhalation injuries, including the critical role of recognizing carbon monoxide and cyanide poisoning in these complex cases.

Key Learning Points:

• Exposure to house fire and prolonged cardiac arrest
• Signs of inhalation injury and airway compromise
• Pathophysiology of inhalation injuries and their impact on multiple organ systems
• Management strategies for inhalation injury, including airway protection and ventilation
• Differentiating carbon monoxide and cyanide poisoning in pediatric fire victims

Case Presentation

A 15-year-old previously healthy girl is brought to the Pediatric Intensive Care Unit (PICU) after experiencing cardiac arrest during a house fire. She was found unconscious by firefighters after a heroic rescue attempt where she saved her brother and his friend. Upon arrival at the hospital, she was unresponsive, intubated, and in severe cardiovascular distress with signs of multi-organ dysfunction.

Key findings include:

• Soot deposits and superficial burns on extremities
• Prolonged resuscitation (45 minutes of field CPR and 47 minutes of in-hospital CPR)
• Cardiovascular compromise with PVCs, cool extremities, and delayed capillary refill
• Metabolic acidosis, AKI, coagulopathy, transaminitis
• Severe hypoxic-ischemic encephalopathy on EEG

These findings raise immediate concern for inhalation injury, which is the primary focus of today's discussion.

Pathophysiology of Inhalation Injury

When a patient is exposed to smoke and hot gases during a fire, inhalation injury results in significant damage to the respiratory system. Inhalation injury has three main components:

1. Upper airway involvement – Thermal injury can cause swelling and obstruction.
2. Chemical pneumonitis – Noxious chemicals like carbon monoxide and cyanide trigger inflammation in the lungs.
3. Systemic toxicity – Toxins such as carbon monoxide and cyanide can affect cellular oxygen utilization.

The primary damage occurs in the lower respiratory tract, leading to airway edema, mucosal damage, and bronchial cast formation. This process can result in bacterial pneumonia, respiratory failure, and the need for aggressive intervention.

Investigating Inhalation Injury

A thorough diagnostic approach is essential when assessing patients with suspected inhalation injury:

1. Basic Imaging: A chest X-ray (CXR) should be obtained, although a normal film doesn't rule out injury.
2. Gold Standard – Bronchoscopy: Direct visualization allows for assessment and removal of bronchial casts.
3. Laboratory Tests: Key labs include CBC, CMP, blood gas, lactate, co-oximetry (to assess CO levels), and toxicology screens.
4. CO and Cyanide Testing: Critical for identifying toxic exposure, especially when a patient presents with altered mental status or unexplained metabolic acidosis.

Managing Inhalation Injury: A Structured Approach

Management revolves around three key pillars:

1. Airway Protection: Intubation is essential for airway security. Signs such as progressive hoarseness, soot around the nose, or face burns should prompt early intervention.
2. Ventilation Strategies: Use low tidal volumes and optimized PEEP for lung protection. In severe cases, consider advanced modalities like APRV, HFOV, or ECMO.
3. Secretion Management: Aggressive pulmonary toilet and medications such as nebulized heparin, tPA, and N-acetylcysteine may help manage airway inflammation and obstructions.

Recognizing and Treating Carbon Monoxide (CO) Poisoning

In cases of suspected CO poisoning, the key is early recognition and treatment:

• CO Blood Levels: Measure carboxyhemoglobin levels immediately.
• Classic Symptoms: Look for the “cherry red” skin color and neurologic symptoms such as confusion or dizziness.
• First-Line Therapy: Administer 100% oxygen via a non-rebreather mask or endotracheal tube.
• Hyperbaric Oxygen: While 100% O2 works well, HBO therapy is crucial for preventing delayed neuropsychiatric complications.

Fun Fact: CO has a much higher affinity for hemoglobin than oxygen, which leads to a "tissue oxygen famine," even with normal PaO2 levels.

Identifying Cyanide Poisoning in Fire Victims

Cyanide poisoning can be particularly challenging to diagnose but is crucial in fire victims. Look for:

• Classic Triad: Metabolic acidosis, elevated venous oxygen saturation, and CNS symptoms (confusion, mydriasis).
• Late Signs: Cardiovascular collapse, hypotension, and bradycardia.
• Treatment: Hydroxocobalamin is the first-line antidote (70 mg/kg IV), with the caveat that purple-red urine is a normal side effect.
• Avoid Nitrites: In burn victims, nitrite-based cyanide kits can worsen CO poisoning by forming methemoglobin.

Clinical Tip: Unlike CO poisoning, cyanide poisoning presents with seizures and dilated pupils.

Clinical Course of Our Patient

The patient’s clinical course was marked by rapid deterioration despite aggressive treatment:

• Initially managed with high-frequency oscillatory ventilation (HFOV) due to pulmonary hemorrhage
• Developed severe PARDS, cardiac dysfunction, and multi-organ failure within 12 hours
• Ultimately, neuroimaging revealed anoxic brain injury with cerebral edema and herniation, leading to brain death

This heartbreaking case highlights the importance of early intervention and recognition of inhalation injury in burn victims.

Key Takeaways:

• Act quickly to protect the airway in pediatric fire victims—early intubation can be life-saving.
• Protect the lungs with proper ventilation strategies and aggressive secretion management.
• Time is critical when dealing with CO and cyanide poisoning. Immediate recognition and treatment are key to survival.
• Inhalation injuries can result in rapid multi-organ failure, and management requires a multi-disciplinary approach.

Join Us for More Insights

We hope this case-based discussion provides valuable insights into the complex management of inhalation injuries in pediatric burn victims. Stay tuned for our next episode and be sure to share your feedback and subscribe to the podcast!

For more episodes, visit our website at picudoconcall.org.

References:

• Tapking C., et al. "Burn and Inhalation Injury." Fuhrman & Zimmerman - Textbook of Pediatric Critical Care, Chapter 116, Pages 1347-1362.
• Bergman, et al. "Burns and Smoke Inhalation." Rogers Textbook of Pediatric Intensive Care, 6th edition, Chapter 33, Pages 484-497.
• Goh CT, Jacobe S. "Ventilation strategies in pediatric inhalation injury." Paediatr Respir Rev. 2016 Sep;20:3-9.
• Rodeberg DA, Housinger TA, et al. "Improved ventilatory function in burn patients using volumetric diffusive respiration." J Am Coll Surg. 1994 Nov;179(5):518-522.