Morning Report: 3/28/2012

Here are some clinical pearls on cyanide poisonings from yesterday’s morning report by Dr. Audrey Tan:

CYANIDE POISONING

• Sources

1. Ingestion – chemists, photographers, jewelers, lab techs have access to cyanide salts
2. Smoke inhalation – release of cyanide from combustion of wool, silk, synthetic rubber
3. Occupational exposure – many industrial processes involve CN (jewelers, mining, fumigation, photography)
4. Medicinal sources – nitroprusside
5. Food sources – pits of apricots, bitter almonds, cherry, peaches
6. Smoking

• Pathophys – NO ATP!

1. Inhibition of cytochrome a3 of ETC –> hydrogen unable to combine with oxygen at terminal end of chain –> no ATP can be made –> cellular hypoxia

• Clinical presentation

1. CNS – HA, anxiety, agitation, confusion, lethargy, coma, seizure, “knocked down quickly”
2. Cardiac – abnormalities of BP and HR
3. Resp – tachypnea –> bradypnea
4. Skin – cherry red skin color

• Diagnosis

1. Bitter almond smell – only detected by 60% of pop
2. Severe metabolic acidosis with increased AG and significant lactic acidosis (>7 mmol/L)
3. VBG looks like ABG
4. Unexplained coma and acidosis = THINK CYANIDE

• Tx

1. Supportive care – ABCs
2. Cyanide antidote kit
• Amyl nitrite pearls

1. Use until IV established
2. Inhaled for 30 sec to 1 min
3. Induces about 5% MetHb
• Sodium nitrite

1. Peds dose – 0.33 mL/kg
2. Adult dose – 10 mL
3. Infuse over 2-4 minutes
4. Adv effects – vasodilation, hypotension, tachycardia
5. Induces 7-14% MetHb
• Sodium thiosulfate

1. Peds dose: 1.65 mL/kg
2. Adult dose: 50 mL
• Mechanisms of kit
• Nitrite –> methemoglobinemia

• CN has higher affinity for MetHb
• MetHb of about 20-30% can be tolerated without sig adv effects
• Thiosulfate
• CN transferred from cyanomethemoglobin to thiosulfate –> thiocyanate –> peed out

3. Hydroxocobalamin

• MOA – chelates CN to form cyanocobalamin (vit B12) –> eliminated in urine
• Dose
• 2.5 gm for dilution in 100 cc NS

• Starting dose
• Adult – 5 gram (2 vials)
• Peds – 70 mg/kg
• Give further doses of 5 gm (up to 15 gm total) recommended for incomplete or transient result
• To know
• Red color of hydroxocobalamin –> chromaturia and red skin for up to 2 weeks
• Interferes with colorimetric lab tests; if given pre-hospital, EMS should draw labs first
• Do not give in same IV as thiosulfate

4. So if concomitant CO and CN poisoning:

• Do not have nitrites – CO poisoning + MetHb = BADNESS
• Suggested mgmt
• Sodium thiosulfate +/- hydroxocobalamin
• HBO

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Jay Khadpe MD

Editor in Chief of "The Original Kings of County" Assistant Professor of Emergency Medicine Assistant Residency Director SUNY Downstate / Kings County Hospital

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