Podcast #112- Eating Smoke: Inhalation Injuries

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Firefighters are exposed to a number of dangers on a daily basis.  With this being the anniversary of 9/11, we want to dedicate this blog and podcast to all the victims from that day.  Most of us are already very familiar with issues that arise with firefighters such as PTSD and the impact on the body from long hours, overtime, and physical stress.  Unfortunately, we often forget about the other needs and special scenarios that firefighters come across and will cover some of the key aspects in this blog and podcast.
Firefighters already are under stressful conditions between long hours and overtime. While there are many dangers with firefighting, one of the main concerns is smoke exposure.  Not only is it the chemical irritants but heat can also cause direct injury including to the eyes and respiratory tract.

Chronic epithelial injury has been seen in experienced firefighters with resulting airway reactivity when exposed to smoke.  In one study, 80% of experienced firefighters had airway reactivity whereas none of the new recruits had airway reactivity.  The airway reactivity persisted for at least six hours but not 24 hours.

Another study was on 30 firefighters with severe smoke exposure.  This study of firefighters in Houston, Texas demonstrated 28 out of the 30 firefighters on initial evaluation had symptoms consistent with recent smoke exposure: 19 had substernal pain or burning, 9 had headaches, 8 had burning eyes, 8 had dyspnea, and 6 had nausea.  Interestingly, none in this study had wheezing on the initial exam.  The authors found a significant decrease in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) compared to control subjects which further supports previous evidence of possible lung disease related to occupational exposure. 

When it comes to burns to the mucosa and respiratory tract secondary to smoke exposure, this is the same as burn management in general.  Initially, there may be few signs and symptoms.  Facial burns, hoarse voice, singed nasal hair, carbonaceous sputum, and soot or carbonaceous material in the oral cavity are early clues.  Later there may be facial/oral edema, stridor, wheezing, dyspnea, and cyanosis.  Toxicology studies when available are beneficial but others tests such as CBC, CMP, ABG, EKG, and CXR all can be beneficial.  Early identification of the need for advanced airway management is key to avoid complications.  If symptoms are worsening, there are major burns over a large area or significant burns to the fact/neck, mouth, respiratory distress/depression, or altered mental status these should all be key signs to intubate.  Bronchodilators are also beneficial if there is evidence of bronchospasm.

The overhaul process is also dangerous.  Although SCBAs are supposed to be worn through firefighting activities in dangerous environments, it is often taken off during the overhaul process.  In a study where gases during overhaul such as carbon monoxide (CO), carbon dioxide (CO2), hydrogen cyanide (HCN), hydrogen sulfide (H2S), and oxygen (O2) were within NIOSH ceiling recommendations there were still alterations in genes that impacted proteins related to inflammation-associated lung disease and cancer.

Other studies have shown this to be the same issue with products of combustion in general.  Again, the emphasis to prevent such injuries is proper use of SCBA and other personal protective equipment (PPE) for prevention.

Although SCBAs are very important to protect the respiratory system, the skin is another major source of cancer and other injuries such as burns. One recently published study found that the main exposure route for carcinogens is skin absorption.  Proper decontamination of the skin, PPE including helmets and clothing, and work surfaces. 

As we have hinted at, smoke is full of dangers besides burns to the respiratory tract.  Chlorine and phosgene have also been found in hazardous environments that firefighters come across.  Both chlorine and phosgene react with water in the respiratory tract to form hydrochloric acid.

Hydrochloric acid can be very serious and is a combustion product of polyvinyl chloride (PVC).  For inhalational injuries it can cause PVCs and other arrhythmias, pulmonary edema (2-12 hours later), dyspnea, and chest pain. 

A bleach smells usually accompanies chlorine and is highly water-soluble.  Although symptoms can be mild and it is usually irritating, extreme cases can cause airway edema, obstruction, or laryngospasm.  In most cases, supportive care is all that is needed.

Phosgene has low water-solubility and is heavier than air which increases its chance to damager the lower respiratory tract.  Classically, the description has been an odor of freshly cut hay.  It is used to manufacture plastics, dyes, pharmaceuticals, and pesticides.  This means that hours there can be the development of respiratory distress, cough, and pulmonary edema.  Care is supportive but management of oxygen and even acute respiratory distress syndrome (ARDS) may be needed.  Unfortunately, there are no antidotes.

However, hydrogen cyanide (HCN) is also dangerous but there is an antidote.  The smell of bitter almonds may be present and cherry red skin is less common.  The PO2 of venous blood is similar to arterial blood with a possible unexplained severe lactic metabolic acidosis.  The agent of choice is hydroxocobalamin (commercially called a Cyanokit).  There are other options with the Lilly Kit being the second-line choice.  This consists of amyl nitrate, sodium nitrite, and sodium thiosulfate.  There are a number of issues regarding this second option and why a Cyanokit is better which has been expertly reviewed by The Dantastic Mr. Tox and Howard Show.

Another time to consider giving a cyanide antidote is with hydrogen sulfide.  This may have a “rotten egg” smell.  100% oxygen is important but the Cyanokit may also be administered.  If not available, the nitrite component of the Lilly Kit may be given but do not give the thiosulfate portion.  The theory is that this will increase methemoglobin formation in blood and will cause conversion of sulfide to sulfmethemoglonin which is less toxic.

The main aspect to know though is that methemoglobinemia can be induced (and intentionally so) with the Lilly Kit.  Methemoglobinemia can be cause though by hemoglobin oxidation from the heat of a fire and the classic “chocolate brown” color of blood may be seen.  The SpO2 will be falsely elevated until there are higher levels present.  The management is mainly methylene blue except in G6PD deficiency.

Speaking of falsely elevated SpO2 levels, think of carbon monoxide.  Symptoms are similar in nature and often occur in fires.  It can often co-occur with cyanide toxicity.  Headache is often the first symptom but can rapidly progress to unconsciousness and death.  Hypoxia, lactic acidosis, and hypotension are seen.   Although hyperbaric oxygen therapy is commonly discussed as a main part of management, it can be difficult to access and high flow oxygen is the mainstay in emergency management.

Also check out a podcast by EmCrit regarding cardiac arrest management after smoke inhalation with toxicologist Dr. Lewis Nelson.

As a summary, firefighters are exposed to a number of dangers on a daily basis.  Get a good history and physical checking for indications of advanced management such as intubation.  Look for telltale toxidromes that can help direct such as the unique smells from certain chemicals.  CBC, CMP, ABG and possible VBG, pulse oximetry, EKG, CXR, and levels from toxins can be beneficial.  Supportive care is key but high flow oxygen is often key.  Remember to contact your local toxicologist which in the United States is 1-800-222-1222.

Let us know what you think by giving us feedback here in the comments section or contacting us on Twitter or Facebook.  Remember to look us up on Libsyn and on iTunes.  If you have any questions you can also comment below, email at thetotalem@gmail.com, or send a message from the page.  We hope to talk to everyone again soon.  Until then, continue to provide total care everywhere.

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