2. What’s the problem?
Heat – Thermal Injury
Smoke – Particulate
Hypoxic gas inhalation (FiO2 <0.21) - Asphyxia
Carbon Monoxide - Asphyxia
Cyanide – Asphyxia
Smoke inhalation better predictor of mortality
than burn extent
3. Thermal Injury
Obviously patients may have massive burn injury
with or without trauma
Dry Heat (from house fire) has very poor
conveyance of heat beyond vocal cords
Duration of exposure is important – flash burns
usually only singe nasal hair and mucosa
Stridor
Difficulty managing secretions
Hoarseness (count to 10)
4. Particulate matter
Smoke is full of particulate matter, soot and ash
Causes obstruction and sloughing in the small
airways leading to atelectasis and shunt etc…
Bronchospasm – due to direct toxic effects
ARDS
If their lung fall to pieces this is what will most
likely kill them
5. Carbon Monoxide
odorless, tasteless, colorless, nonirritating gas
formed by the incomplete combustion of
carbon-containing compounds
Headache, malaise, confusion, angina, seizures,
heart failure coma…
6. Pathophysiology
Binds to Hb with 240
times affinity than O2
Reduces the other 3
sites ability to offload
O2 at tissue level
Binds to myoglobin
Interrupts
mitochondrial function
7. How to pick it up
? Sats probe (depends how good your probe is)
Work by two frequencies (940 and 660nm) – measure
oxy and deoxy respectively
COHb absorbs light at 660nm just like OxyHb therefore
usually useless to differentiate
(remember MetHb is similar)
Co-oximetry is the way to do it (4 rather than 2
wavelenghts)
Your friendly blood gas machine has a nice co-
oximeter in it
What will the pO2 be?
8. What levels matter
Normal <5%
Smokers/COPD – allow up to 20%
High levels DO NOT correlate with outcome
9. How to treat
Lots of oxy
Half life in FiO2 0.21 about 300 mins
Half-life in FiO2 1.0 about 60-90 mins
What about minute ventilation?
? Hyperbaric Oxygen – NEJM 2002 Volume 347:1057-
1067
Probably >25-40% and should be available within 6
hours and most importantly not compromise care
All pure COHb poisonings in single chambers on
multiple occasions
How do you apply the oxy?
10. Long term
Poorly understood delayed neurosequelae (DNS)
Cognition/personality/movement disorders
3 days – 9 months post exposure
Usually only if there was LOC with exposure
Again - not correlated with COHb levels
11. Cyanide
Not James Bond
Commonly in house fires with plastic furniture
Repeatedly missed due to lack of suspicion
12. How does it kill you?
Mitochondrial toxin
Cytochrome a3
13. How does it kill you?
Stops oxidative phosphorylation and ATP production
Switches to anaerobic production and subsequent
lactic acid
Glucose Pyruvate
In presence of
O2
In absence of O2
Acetyl CoA
Lactic
acid
Kreb’s cycle
LACTATE H+
Dissociates
14. Clinically
Sick and very sick
LOC, seizures, BP, Acidosis
• TCAs, Aspirin, organophospates, meningococcal,
eclampsia
Collapse following gas exposure
• H2S, CO
15. Tests
Mainly to exclude other causes
• ECG, BSL, Aspirin levels, HCG
Specifically
• ABG
• Central venous pO2 to look for oxygen uptake
(what else will affect this)
• Lactate (correlates with cyanide levels)
16. Treatment – Direct binding
Hydroxycobalamin
• Binds to form cyanocobalamin – safely excreted
• Can interfere with co-oximetry
Dicobalteditate
• Horrible toxic drug that at least works
17. Treatment – MetHb induction
Sodium nitrite/Amyl Nitrite
• Cyanide has more affinity for fe3+ on MetHb than it
does for Fe3+ on Cyt A3
• Has some rather obvious problems
18. Treatment – sulfur donors
Body normally deals with cyanide with
rhodanese – a sulfur requiring enzyme
Sodium Thiosulfate
Works reasonably and relatively safe
19. Treatment
Most algorithms suggest:
1. Hydroxycobalamin
2. AND Sodium thiosulfate
Have low threshold for treating in shocked
house fire victim with profound lactic acidosis
20. Summary
Smoke inhalation has 5 main aspects
1. Heat - airway
2. Particulate – wheeze/ARDS
3. Hypoxia – brain damage
4. CO – functional anemia
5. Cyanide – histotoxic hypoxia
Usually with other catastrophic injuries
Often associated with drug ingestions
21. Summary
For CO
1. Co-oximetry – not sats probe
2. Get the oxy on
3. Levels don’t correlate
For cyanide
1. Be suspicious
2. Shock/Seizures/Profound lactic acidosis
3. Central venous O2 useful
4. Hydroxycobalamin/Thiosulfate if good suspicion –
these are safe.
