Smoke inhalation

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Smoke inhalation

  1. 1. Smoke inhalation
  2. 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. 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. 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. 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. 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. 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. 8. What levels matter Normal <5% Smokers/COPD – allow up to 20% High levels DO NOT correlate with outcome
  9. 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. 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. 11. Cyanide Not James Bond Commonly in house fires with plastic furniture Repeatedly missed due to lack of suspicion
  12. 12. How does it kill you? Mitochondrial toxin Cytochrome a3
  13. 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. 14. Clinically Sick and very sick LOC, seizures, BP, Acidosis • TCAs, Aspirin, organophospates, meningococcal, eclampsia Collapse following gas exposure • H2S, CO
  15. 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. 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. 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. 18. Treatment – sulfur donors Body normally deals with cyanide with rhodanese – a sulfur requiring enzyme Sodium Thiosulfate Works reasonably and relatively safe
  19. 19. Treatment Most algorithms suggest:1. Hydroxycobalamin2. AND Sodium thiosulfate Have low threshold for treating in shocked house fire victim with profound lactic acidosis
  20. 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. 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.

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