95 | The essential guide to toxicology part six: how to manage smoke inhalation and fire injury as a veterinary nurse

NursingPodcastToxicologyEmergency + Critical CareRespiratory
Written By Laura Jones

This week we wrap up our toxicology series with a true emergency and one of the most dramatic, challenging and emotional conditions: inhalation of smoke, thermal and chemical airway injury in our feline and canine patients.

Managing fire-injury is so much more than ‘just’ dealing with smoke inhalation, and these patients can be challenging to nurse, since their disease is often much worse than it initially seems.

These patients need intensive respiratory support, monitoring and nursing care, which means that as well as challenging to manage, they’re incredibly rewarding, and provide us with lots of nursing opportunities to make a difference.

So in this episode, we’ll discuss what happens when our patients become fire-injured, the common complications we see, and the nursing our patients need to recover successfully. You’ll leave this episode feeling much more confident about managing these patients, and with some new skills ready to put to use with your next case.

What impact does fire injury and smoke inhalation have on our veterinary patients?

Smoke inhalation injuries are often underestimated and are a significant cause of morbidity and mortality in patients involved in fires.

Patients often present with upper airway obstruction, bronchospasm and secondary pneumonia, and respiratory failure can quickly result. It isn’t just the initial respiratory injury we need to worry about, though. Concurrent thermal burn injuries are also common, as are systemic signs of shock, and inhalation of poisonous gases and fumes. 

All of this impacts not just breathing - aka ventilation, where the airways need to work well enough to draw in oxygen - but oxygenation, too, where that oxygen is delivered effectively to cells and tissues. 

Smoke inhalation causes significant disease via mixed mechanisms of injury.

The combination of thermal injury from inhaling steam and hot air, chemical injury from inhaling toxic gases and particulate matter, and systemic hypoxia from inhaling toxic gases such as cyanide and carbon monoxide all contribute to the patient’s condition.

Thermal injuries mostly affect the upper airways, including the nose, pharynx and larynx and proximal trachea. This is because the upper airways are effective at dissipating heat, and injury to the bronchi and alveoli is therefore limited. In severe cases, though, the lower respiratory structures can also be affected.

Thermal injury to the lower airways can cause inflammation, erosion, oedema and bronchoconstriction. This impairs lung function and increases the work of breathing - resulting in hypoxaemia.

In addition to thermal injury from hot air, smoke contains lots of particulate matter. Small particles can be inhaled easily, where they cause inflammation in the lower airways; given the concurrent thermal injury and reduced lung function, the body’s ability to clear these particles is also reduced, causing ongoing inflammation. Larger particles can become lodged in the bronchi within the lower airways, causing lung lobe collapse.

One of the biggest considerations in smoke inhalation is the exposure to toxic gases. Significant amounts of carbon monoxide is present in fire smoke; whilst this itself is not directly irritating to the airways, it as a stronger affinity for haemoglobin than oxygen does. This means that the red blood cells will bind to carbon monoxide instead of oxygen, and the delivery (and release) of oxygen to tissues is markedly reduced.

Carbon monoxide also impacts cellular metabolism and function throughout the body, causing multiple complications in these patients - from platelet dysfunction to central nervous system signs and much more.

It’s not just carbon monoxide we need to worry about, though. Cyanide gas is often produced from the burning of paper products, fabrics and synthetic materials. Like CO, cyanide is not directly irritating to the lungs - but it is a metabolic toxin which impairs cellular function, meaning that even if enough oxygen makes it to the cells, they can’t effectively turn that oxygen into energy.

The combination of these three mechanisms - thermal, particulate matter and toxic gas injury - causes significant hypoxaemia. In addition, these effects may progress even after the patient has been removed from the fire. This is because pulmonary oedema, chemical-associated pneumonitis, and airway oedema can take up to 12-24 hours to reach their peak. Patients often develop acute respiratory distress syndrome (ARDS), even if their clinical signs are not immediately obvious.

How do these patients present, and what clinical signs should we be looking out for?

The history for patients is usually straightforward as, in most cases, caregivers are aware that the patient has been exposed to fire or smoke. Clinical signs, however, may not be apparent at the time, and this may delay treatment and impair the patient’s outcome.

Because early oxygen therapy is vital, any patient - even those not showing signs of distress - should receive oxygen therapy and stabilisation ASAP.

If clinical signs are seen at the scene of the fire, these usually include:

  • Coughing

  • Gagging

  • Hypersalivation

  • Tachypnoea

  • Dyspnoea

  • Increased respiratory effort

  • Orthopnoea

  • Mentation changes

  • Skin burns

  • Pain

  • Ocular and upper respiratory signs

In addition, patients will usually smell of smoke, have soot on their coats, or singed whiskers.

Physical examination also typically reveals significant dehydration, corneal ulceration, blepharospasm and reduced tear production. Neurological signs may also be apparent either at presentation, or delayed; delayed signs are thought to be due to the toxic effects of carbon monoxide on tissues.

Exposure to smoke and fire within enclosed spaces, such as a house, vehicle or shed, increases the risk of heavy smoke and toxic gas exposure, and typically results in worse clinical signs - either delayed or at the time of initial presentation.

What diagnostics do these patients need?

We usually know what has happened to these patients - but there are still lots of diagnostic tests we need to perform to determine our patient’s status and inform treatment decisions. These include:

  • Arterial blood gas analysis to assess oxygenation

  • Biochemistry, haematology and coagulation panel to assess general health, organ function, electrolytes and spot coagulopathies early

  • Thoracic radiographs or point-of-care lung ultrasound to evaluate lung changes and monitor progression

An important point to note in these patients is that pulse oximetry is not reliable, so we can’t use this to accurately assess oxygenation. This is because our probes cannot distinguish between carboxyhaemoglobin (haemoglobin full of carbon monoxide) or oxyhaemoglobin (haemoglobin full of oxygen). 

Mucous membrane assessment is also unreliable - so to assess oxygenation, arterial blood gas analysis is indicated, alongside your evaluation of the patient’s respiratory signs.

So how do we treat - and nurse - patients with smoke inhalation?

Our first and most important treatment is oxygen therapy. We need to get this on board ASAP, at high concenrations (aka fraction of inspired oxygen, or FiO2). High oxygen concentrations help to displace carbon monoxide from haemoglobin, allowing oxygen to bind to it and be delivered to cells and tissues.

Oxygen therapy is also the only availabe treatment for carbon monoxide toxicosis and associated cellular injury - so the importance of oxygen treatment, even if respiratory signs are minimal, cannot be overstated.

Since 100% oxygen is often required, many patients require anaesthesia, intubation, and ventilation with 100% oxygen. However, alternative methods of providing high-level oxygen, such as high-flow nasal oxygen therapy (HFOT) are also commonly used. Humidification and warming of this oxygen is indicated, especially when used at high flow rates, since it will be both cool and drying to the patient’s airway mucosa.

Alongside oxygen therapy, patients need fluid resuscitation to correct hypovolaemia and dehydration where present, whilst minimising fluid overload which can cause pulmonary oedema and worsen respiratory signs.

Additional respiratory treatment, such as nebulisation and respiratory physiotherapy, and bronchodilators, may be required depending on the individual patient and the severity of their clinical signs. 

Patients will also need wound and burn management, including wound care, dressing application and changes, and prevention of patient interference. Ocular injury and ulceration is common, so regular ocular assessment and lubrication is essential.

Analgesia should also be provided since patients with burns or corneal injury/ulceration will be in pain. This includes airway burns which will not be obvious on examination, so if any concerns exist regarding these, trial treatment with analgesia is advised.

In severe cases of upper airway burns, swelling and oedema may cause airway obstruction, necessitating a temporary tracheostomy. This will require careful nursing management, including humidification, suction, careful patient monitoring and regular tube changes.

Nursing these patients is incredibly intensive.

These patients are often both critically unwell and recumbent. In addition to general nursing care, our focuses include:

  • Intensive respiratory and neurological monitoring

  • Managing fluid balance and fluid therapy

  • Monitoring pain and providing analgesia

  • Providing nutritional support

  • Monitoring oxygenation and adjusting inspired oxygen concentrations or oxygen delivery method as needed

  • Nebulisation and respiratory physiotherapy

  • Skin, wound and special sense care

  • Serial POCUS to assess lung changes

And much more.

These patients need intensive and at times challenging nursing, but the good news is that in many cases the prognosis is favourable - particularly where patients do not have severe burns, or receive prompt stabilisation.

If your patient’s oxygen requirements continue to increase, you’re concerned they;re showing signs of respiratory fatigue or they have severe burns, it’s advisable to refer them early - they may need ventilation, and getting them to a specialist centre whilst they’re stable enough to transfer is vital.

This is really where we come into things as nurses and technicians, because we’re the ones monitoring these patients in the ward. By looking out for those subtle signs of deterioration and recognising it an early stage, we can help advocate for our patients and improve their outcomes.

Did you enjoy this episode? If so, I’d love to hear what you think. Take a screenshot and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!

References and Further Reading

Laura Jones
Next

94 | The essential guide to toxicology part five: how to manage ingestion of household hazards as a veterinary nurse