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
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)
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
Carbon Monoxide odorless, tasteless, colorless, nonirritating gas formed by the incomplete combustion of carbon-containing compounds Headache, malaise, confusion, angina, seizures, heart failure coma…
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
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?
What levels matter Normal <5% Smokers/COPD – allow up to 20% High levels DO NOT correlate with outcome
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?
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
Cyanide Not James Bond Commonly in house fires with plastic furniture Repeatedly missed due to lack of suspicion
How does it kill you? Mitochondrial toxin Cytochrome a3
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
Clinically Sick and very sick LOC, seizures, BP, Acidosis • TCAs, Aspirin, organophospates, meningococcal, eclampsia Collapse following gas exposure • H2S, CO
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)
Treatment – Direct binding Hydroxycobalamin • Binds to form cyanocobalamin – safely excreted • Can interfere with co-oximetry Dicobalteditate • Horrible toxic drug that at least works
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
Treatment – sulfur donors Body normally deals with cyanide with rhodanese – a sulfur requiring enzyme Sodium Thiosulfate Works reasonably and relatively safe
Treatment Most algorithms suggest:1. Hydroxycobalamin2. AND Sodium thiosulfate Have low threshold for treating in shocked house fire victim with profound lactic acidosis
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
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.