Arek Wiktor M.D.
Burn Fellow
University of Colorado Hospital


Background

Smoke

Pathophysiology

Diagnosis

Treatment

Specific Lethal Compounds http://spanishlakefd.com/firealarms/

Learning Objectives

Describe the pathophysiology of inhalation injury

How is inhalation injury diagnosed?

What adjunctive measures are used to treat inhalation injury?

What is the treatment for carbon monoxide and cyanide poisoning?

A Sunday afternoon stroll thru the fire… http://www.aeromedix.com/product-exec/parent_id/1/category_id/12/product_id/1074/nm/Safe_Escape_Smoke_Hood

Epidemiology

15-30% of burn admissions have inhalation injury

Independent predictor of mortality, ↑ by 20%

Increases pneumonia risk

Leading diagnosis of those hospitalized and treated on 9/11, World Trade Center attack

Anatomic Classification

Upper airway

Lower airway
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Systemic toxicity http://www.monroecc.edu/depts/pstc/backup/parasan4.htm

SMOKE

Variable, changes with time burning

Toxic gases and low ambient oxygen

Ingredients:
Aldehydes (formaldehyde, acrolein), ammonia, hydrogen sulfide, sulfur dioxide, hydrogen chloride, hydrogen fluoride, phosgene, nitrogen dioxide, organic nitriles

Particulate matter
Prien et al. Burns 1988; 14:451-460

Pathophysiology

Cilia loss, respiratory epithelial sloughing
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Neutrophilic infiltration
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Atelectasis, occlusion by debris/edema
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Pseudomembranes

Bacterial colonization at 72 hrs
Hubbard et al. J Trauma 1991; 31:1477-1486

Bartley et al.
Drug Design, Development and
Therapy. 2008; 2: 9–16.

Secondary Lung Injury

Unilateral smoke inhalation damages contralateral lung

Immune response, increased permeability

Oxygen-derived free radicals

NO mediated damage (chemotactic factor neuts)

Eiscosanoids (TXA2→TXB2)

Reduced phagocytosis in macrophages

Systemic Effects

Larger fluid resuscitation (2→5cc/kg/%)
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Additive effect to burns

12% pts inhalation injury alone require intubation *

62% pts burn + inhalation injury intubated *
Clark et al. J Burn Care Rehabilitation, 1990; 11:121-134

Miller et al. Journal of Burn Care Research. 2009; 30(2) 249-256

Diagnosis

Clinical findings:
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

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Facial burns (96%)
Wheezing (47%)
Carbonaceous sputum (39%)
Rales (35%)
Dyspnea (27%)
Hoarsness (26%)
Tachypnea (26%)
Cough (26%)
Cough and hypersecretion (26%)
DiVincenti et al. Journal of Trauma, 1971; 11:109-117

NO ONE FINDING IS
SUFFICIENTLY SENSITIVE
OR SPECIFIC!
Must use clinical judgment!

Tools for Diagnosis

Bronchoscopy

Pulmonary function testing

Xenon 133 lung scan

Grades of Inhalation Injury
Endorf and Gamelli. Journal of Burn Care and Research. 2007; 28:80-83

Treatments

Airway Control

Chest physiotherapy
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Suctioning
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Therapeutic bronchoscopy
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Ventilatory strategies
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Pharmacologic adjuncts

Treatment
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≥ 40% burn

Transport http://www.burnsurgery.com/Betaweb/Modules/initial/bsinitialsec2.htm

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Ventilator Strategies
Airway pressure release ventilation (APRV)
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Intrapulmonary percussive ventilation (IPV)
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High-frequency percussive ventilation (HFPV)
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High frequency oscillatory ventilation (HFOV)

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Single center, prospective randomized trial 2006-2009
387 pts screened
31 pts HFPV, 31 pts LTV (ARDSnet)
Chung et al. CCM; 2010: 38(10) 1970-1977

Results
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No significant difference in mortality or ventilator free days
Significant difference in “Rescue Therapy”

Results


No significant difference in mortality or ventilator free days
Significant difference in “Rescue Therapy”

P/F ratio vs Ventilator Mode
Chung et al. CCM; 2010: 38(10) 1970-1977

Study Conclusions
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Study stopped for safety concerns in LTV group
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Gas exchange goals met in all HFPV pts, and not in 1/3 of LTV pts
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Trend for less barotrauma, less VAP, less sedation
“Strict application of LTV may be suboptimal in the burn population”

Pharmacologic Intervention
Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16.

Pharmacologic Intervention
Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16.

Airway Obstructive Casts
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Mucus secretions
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Denuded airway epithelial cells
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Inflammatory cells
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Fibrin
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-Solidifies airway content
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Several studies shown reduction in size of casts with fibrinolytic agents (tPA)

Casts
Enkhbaatar et al., 2007

Theory Behind Inhaled Heparin
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Animals with Burn + ARDS have decreased levels of antithrombin in plasma and BAL specimens
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Heparin potentiates antithrombin by 2000x
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Prevention of fibrin deposition in lungs
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Heparin inhibits antihrombin’s antiinflammatory effect - ? systemic rhAT ?

Shriners Protocol
Since 1990 (560+ patients treated)
Mlcak RP et al. Burns, 2007;33:2-13

Evidence (Pro)
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Desai et al. 1998
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Pediatric burns (90 pts total)
1985-1989 (43) vs 1990-1994 (47pts)
↓ reintubation, atelectasis, and mortality
Miller et al. 2009
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30 patients over 5 years, retrospective review
Tx 10,000 units heparin, 20% NA, 0.5 ml AS q4 hrs
Survival benefit, improved LIS scores, compliance
Number needed to treat 2.73

Evidence (Con)
 Holt et al. 2008
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Retrospective review 1999-2005, 150 pts total
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Burn size, LOS, time on vent, mortality SAME
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Only 68% pts had bronchoscopy,
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Attending discretion which treatment to use

Carbon Monoxide (CO)
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CO from incomplete combustion
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CO + Hb → COHb
(affinity 200-250x)
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LEFT shift of oxy-Hb curve (Haldane effect)
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CO binding to intracellular cytochromes and metalloproteins (myoglobin)
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“Two compartment” pharmacokinetics
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Animal experiment 64% COHb transfusion

CO Toxicity Symptoms
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“Cherry-red lips, cyanosis, retinal hemorrhage”rare
CNS and Cardiovascular
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↑ RR, ↑HR, dysrhythmias, MI, ↓BP, coma, seizures
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Delayed neuropsychiatric syndrome (3-240d)
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Cognitive/personality changes/parkinsonianism
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Spontaneous resolution

Signs and Symptoms
Weaver LK. N Engl J Med 2009;360:1217-25.

CO Toxicity Diagnosis


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Pulse oximetry false
HIGH SpO
2
Need cooximetry direct measurement of
COHb

Older ABG analyzers (estimate off dissolved PO
2
)
MRI – lesions globus pallidus/basal ganglia/deep white matter
COHb
%
Symptoms
0-5 Normal
15-20 Headache, confusion, fatigue
20-40 Hallucination, vision
Δ’s
40-60 Combative, coma
60 + Cardiopulmonary arrest

CO Toxicity Diagnosis



Pulse oximetry false
HIGH SpO
2
Need cooximetry direct measurement of
COHb

Older ABG analyzers (estimate off dissolved PO
2
)
MRI – lesions globus pallidus/basal ganglia/deep white matter
COHb
%
Symptoms
0-5 Normal
15-20 Headache, confusion, fatigue
20-40 Hallucination, vision
Δ’s
40-60 Combative, coma
60 + Cardiopulmonary arrest

CO Toxicity Treatment


OXYGEN
Half-life COHb (min)
RA
1ATM
Male 240
Female 168
100%
O
2
47
100% O
2
2.5 ATM
22
33 15


Carbogen – normobaric, normocapnic, hyperventilation (4.5-
4.8% CO
2
)
Hyperbaric oxygen???

Cyanide (CN)

Combustion of synthetics (plastics, foam, varnish, paints, wool, silk)
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Binds to cytochrome c oxidase – dose dependent
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Uncouple mitochondria
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Aerobic → anaerobic = Lactic acid
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Half-life 1-3 hours

CN Toxicity Symptoms
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Dyspnea
Tachypnea
Vomiting
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Bradycardia
Hypotension
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Giddiness/Coma/Siezures
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Death
* The smell of bitter almonds on the breath suggests exposure
(cannot be detected by 60% of the population)

CN Toxicity Diagnosis

No rapid assay
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High lactate (>10mmol/L) ( s/s, 87%/94%)
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Metabolic acidosis
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Elevated mixed venous saturation (<10% a-v) difference
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High index of suspicion
** Also get: COHb and Methemoglobin levels

CN Treatment
Cyanokit (Hydroxocobalamin)

70mg/kg dose (5g vials)
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Combines with cyanide to from cyanocobalamin (Vit B12)
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Red membranes/urine
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Hypertension, Anaphylaxis
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5% increase COHb, interfere with HD
LFTs/Cr/Fe levels

Cyanide Antidote Kit (CAK)
Amyl nitrite pearls, sodium nitrite, and sodium thiosulfate


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Amyl nitrate and sodium nitrate induce methemoglobin
Methemoglobin+cyanide→releases cyanide from CC
Sodium thiosulfate enhances cyandide→thiocynate→renal excretion
Avoid nitrate portion in pts with inhalation injury
(COHb >10%)
Vasodilation and hypotension

Acquired Methemolgobinemia

NO2, NO, benzene gases → oxidation of iron

Fe 2+ → Fe 3+
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Shift curve to LEFT
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Blood “Chocolate brown color”
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Normal PaO2, pulse ox >85%

Tx: Methylene blue (1-2 mg/kg Q 30-60min)

Final Thoughts
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Inhalation injury is bad

Support the airway

Frequent bronchoscopy and monitoring

Different ventilatory strategies

Adjunctive measures need further investigation

The Toilet Snorkel http://www.icbe.org/2006/01/18/the-toilet-snorkel/

Learning Objectives

Describe the pathophysiology of inhalation injury

How is inhalation injury diagnosed?

What adjunctive measures are used to treat inhalation injury?

What is the treatment for carbon monoxide and cyanide poisoning?