Carbon Monoxide and Cyanide Poisoning

EM-CCM Conference 1/21/15

Fire Exposure/Injuries

Presented by:  Dr. Danica Gomes

Summary by:  Dr. Kaycie Corburn

The Case:  60 yo F unknown PMH BIBEMS from a house fire.  There were known fatalities at this house fire.  The patient was being ventilated by EMS personnel via BVM on arrival.  Triage vitals revealed tachycardia and hypertension.  On exam, the patient had soot in her nares, agonal respirations, and was GCS 3.  At that time, the patient was intubated, given fluid replacement, provided with pain control, and given hydroxocobalamin for presumed cyanide toxicity.   A trauma surgery consultation was obtained.  Upon further work-up, ABG analysis reveal carbon dioxide level of 28.2%, lactate level 5.  Post intubation chest x-ray was consistent with ARDS pattern.  CT scan of the head, cervical spine, chest, abdomen and pelvis did not reveal any other traumatic injuries.  The patient had partial thickness burns to her skin of approximately 10% body surface area.  The patient was transferred to a burn center, treated with hyperbaric oxygen therapy, extubated after 3 days, and discharged.

 

Fire Injuries:

-Smoke inhalation injuries

-Cyanide poisoning

-Carbon monoxide poisoning

Smoke Inhalation Injuries:

-Signs and symptoms of impending respiratory failure:

-Signs:  Inflamed nares or oropharynx, singed nasal hair, carbonaceous sputum, soot in nose/mouth, blistering in oropharynx, facial burns, circumferential neck burns

-Symptoms: Persistent cough,  hoarse voice, stridor, wheeze, respiratory distress, depressed  mental status.

 

Assessing the Airway:

-ABG:  evaluates gas exchange along with carbon monoxide level

-CXR:  evaluates for ARDS, consolidation, pneumothorax

-Peak expiratory flow rate:  determines degree of bronchospasm

-End tidal capnography

-Fiberoptic laryngoscopy:  The best way to evaluate the airway. Call ENT, take a look at this link:

http://www.medicalexhibits.com/medical_exhibits.php?exhibit=09016_05B&query=laryngoscopy%20larynx%20fiberoptic%20laryngoscope%20video%20screen%20nasal

Airway Management:

-Mechanical ventilation, intubate early

-Do not wait for oropharyngeal tissue swelling to progress; this may lead to a surgical airway otherwise prevented by early intubation.

-Supplemental oxygen: treats hypoxia, treats carbon monoxide poisoning

-Bronchodilators: combats bronchospasm

 

Mechanical Ventilation:

-Low tidal volume, treat like ARDS: avoid barotrauma

-Permissive hypercapnia: in order to limit barotrauma, allow CO2 level to be in range of 35-55; maintain pH above 7.25

-Alveolar lavage:  clears secretions and debris

-Performed via bronchoscopy

 

Cyanide Poisoning:

-Most cyanide toxicity occurs from fire and smoke exposure

-Cyanide is released during the burning/melting of household items such as rubbers, insulation, and upholstery.

-Cyanide inhibits the final enzyme in the mitochondrial cytochrome pathway, thereby inhibiting oxidative phosphorylation

-Cells are forced into anaerobic metabolism

 

Cyanide Toxicity Signs/Symptoms:

Neuro: Headache, anxiety, confusion, coma, seizures

CVS: Diaphoresis, tachycardia and hypertension followed by bradycardia and hypotension, AV block, ventricular dysrhythmias

Resp: Tachypnea followed by bradypnea, pulmonary edema

GI: Vomiting and abdominal pain

Skin: Flushing then ashen color, irritant dermatitis

 

Cyanide Toxicity Diagnosis:

-Cyanide levels in the blood are volatile and therefore not reliable, half life is about 1 hour; this is a send out test, so results are not readily available

-There is a strong correlation to serum lactate levels.

-Depending on reference, strongly consider cyanide toxicity if lactate levels are above 8-10 range.

-Consider cyanide toxicity from the clinical history

-Given elevated lactate, expect anion gap metabolic acidosis

 

Cyanide Toxicity Treatment:

–Cyanide antidote kit:  Amyl nitrite, sodium nitrite, sodium thiosulfate

http://www.hpsphysiciansupplystore.com/iv-solutions/akorn-cyanide-antidote-pi-1563282.html

-Amyl nitrite and sodium nitrite induce methemoglobinemia

-Cyanide preferentially binds to methemoglobin (forming cyanmethemoglobin), thereby freeing the cytochrome pathway

-Sodium thiosulfate: with the enzyme rhodanase, converts cyanmethemoglobin to renally excretable sodium thiocyanate

Take a look at this link if you prefer pictures:  https://biochemuwi.wordpress.com/2013/04/09/publish-paper-cyanide-poisoning/

-Pitfalls of the cyanide antidote kit (nitrites and sodium thiosulfate):

-Avoid in patients who cannot tolerate methemoglobinemia: for example, concomitant carbon monoxide poisoning or anemia patients

-Causes hypotension, be ready to treat iatrogenic shock

-Cyanokit: Hydroxocobalamin

http://www.gifte.de/Antidote/cyanokit.htm

-Cyanide preferentially binds hydroxocobalamin (forming cyanocobalamin), thereby freeing the cytochrome pathway

-Cyanocobalamin is renally excreted

-Fast onset

-Improves hemodynamics

-First line therapy given above characteristics (carried by FDNY)

 

-Pitfalls of cyanokit (hydroxocobalamin):

-Turns skin and urine red color, takes a look at some of these pictures:

https://umem.org/educational_pearls/922/

http://www.cmaj.ca/content/180/2/251/F1.expansion.html

-Interferes with lab tests that rely on colorimetric methods, for example:

-Creatinine, bilirubin, hemoglobin, and many more (interference lasts from 12 hours to 4 days)

-Urine testing can be altered for up to 8 days

 

Carbon Monoxide Poisoning:

-Exposure during fires, heating systems, burning indoors for heat, car exhaust

-Binds to heme with 240 times affinity compared to oxygen

-Interferes with allosteric changes to 4 heme molecules

-Prevents oxygen off loading to tissues, causing tissue hypoxia

 

Carbon Monoxide Toxicity Signs/Symptoms:

-Mild to Moderate intoxication

-HA, malaise, nausea, dizziness, , altered mental status

-Severe intoxication

-Neuro: seizures, syncope, coma

-CVS: myocardial ischemia, ventricular arrhythmias, pulmonary edema

-Metabolic: profound lactic acidosis

 

Carbon Monoxide Toxicity Diagnosis:

-Obtain a CO level via VBG or ABG

 

Carbon Monoxide Toxicity Treatment:

-Immediate removal from exposure

-High flow O2 to help eliminate CO from body (decreases half-life of CO)

-Intubate for altered mental status, 100% FiO2 on ventilator

-Possible hyperbaric oxygen treatment

 

Criteria for Hyperbaric Oxygen Treatment:

-Loss of consciousness

-Evidence of on-going end-organ ischemia

-Pregnant women with COHb >20% or fetal distress

-Carboxyhemoglobin level:  >25% vs 40%

 

Efficacy of hyperbaric oxygen treatment is not proven

Take Home Points:

-Secure an airway in patients with serious fire injuries.

-Empirically treat quickly for cyanide and carbon monoxide toxicity.

-Contact appropriate transfer centers if your hospital is not capable of caring for these patients.

-Consider hyperbaric oxygen therapy for carbon monoxide toxic patients with above criteria.

References:

Baud, FJ, et al. Elevated blood cyanide concentration in victims of smoke inhalation. NEJM.1991

Chung, KK, et al. High frequenc percussive ventilation and low tidal volume ventilation in burns: A randomized

controlled trial. Critical care medicine. 2010

Clardy, PF, et al. Carbon monoxide poisoning.Uptodate. 2014

Desai, S, et al. Cyanide poisoning. Uptodate. 2014

Harmel, J. A review of acute cyanide poisoning with a treatment update. Critical care nurse. 2011.

Mandel, J, et al. Smoke inhalation. Uptodate. 2014

Marx, Hockberger, Wells. Rosen?s Emergency medicine concepts and clinical practice. 2010.

Rice, PL, et al. Emergency care of moderate and severe thermal burns in adults. Uptodate. 2014