smoke inhalation

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Smoke inhalation

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Page 1: Smoke inhalation

Smoke inhalation

Page 2: Smoke inhalation

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

Page 3: Smoke inhalation

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)

Page 4: Smoke inhalation

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

Page 5: Smoke inhalation

Carbon Monoxide

odorless, tasteless, colorless, nonirritating gas formed by the incomplete combustion of carbon-containing compounds

Headache, malaise, confusion, angina, seizures, heart failure coma…

Page 6: Smoke inhalation

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

Page 7: Smoke inhalation

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?

Page 8: Smoke inhalation

What levels matter

Normal <5%

Smokers/COPD – allow up to 20%

High levels DO NOT correlate with outcome

Page 9: Smoke inhalation

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?

Page 10: Smoke inhalation

Long term

Poorly understood delayed neuro sequelae (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

Page 11: Smoke inhalation

Cyanide

Not James Bond

Commonly in house fires with plastic furniture

Repeatedly missed due to lack of suspicion

Page 12: Smoke inhalation

How does it kill you? Mitochondrial toxin

Cytochrome a3

Page 13: Smoke inhalation

How does it kill you? Stops oxidative phosphorylation and ATP production

Switches to anaerobic production and subsequent lactic acid

Acetyl CoA

Kreb’s cycle

Lactic acid

In presence of O2

In absence of O2

LACTATE H+Dissociates

Glucose Pyruvate

Page 14: Smoke inhalation

Clinically

Sick and very sick

LOC, seizures, BP, Acidosis• TCAs, Aspirin, organophospates, meningococcal,

eclampsia

Collapse following gas exposure• H2S, CO

Page 15: Smoke inhalation

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)

Page 16: Smoke inhalation

Treatment – Direct binding

Hydroxycobalamin• Binds to form cyanocobalamin – safely excreted• Can interfere with co-oximetry

Dicobalt editate• Horrible toxic drug that at least works

Page 17: Smoke inhalation

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

Page 18: Smoke inhalation

Treatment – sulfur donors

Body normally deals with cyanide with rhodanese – a sulfur requiring enzyme

Sodium Thiosulfate

Works reasonably and relatively safe

Page 19: Smoke inhalation

Treatment

Most algorithms suggest:

1. Hydroxycobalamin

2. AND Sodium thiosulfate

Have low threshold for treating in shocked house fire victim with profound lactic acidosis

Page 20: Smoke inhalation

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

Page 21: Smoke inhalation

Summary

For CO1. Co-oximetry – not sats probe

2. Get the oxy on

3. Levels don’t correlate

For cyanide1. Be suspicious

2. Shock/Seizures/Profound lactic acidosis

3. Central venous O2 useful

4. Hydroxycobalamin/Thiosulfate if good suspicion – these are safe.