Mechanical ventilation in critically burned patient with inhalation

Mechanical ventilation It is a treatment option for those patients who have suffered a critical burn by inhalation.

Inhalation injury usually occurs in the context of a multisystemic picture with burns, carbon monoxide poisoning and cyanide toxicity. It ultimately results from the inhalation of very hot gas and products of incomplete combustion, usually during a fire.

2% of patients with burns have injuries by inhalation, being more frequent the bigger the burned body surface. In burned patients Inhalation injury is a fundamental determinant of increased morbidity and mortality, being responsible for half of the deaths of burned patients.

Damage to the airway and lung Depends on the components of inhaled smoke, the degree of exposure and the response of the organism.

Respiratory injury

The injury due to heat and toxic gases causes edema of the upper airway with clinical obstruction. These symptoms are greater the lower the patient is and usually appears in the first 12-18 hours, although the onset of symptoms may be delayed up to 72 hours

Respiratory injury is the main cause of immediate death. We distinguish several types:

  • Thermal injury: heat injury is usually limited to the oropharynx by the reflex closure of the glottis and the high thermal dissipation power of these tissues.
  • Inhalation injury of composition products: the water-soluble gases react with the water of the mucous membranes releasing strong acids and alkalysis, producing edema and bronchospasm. Slightly soluble gases produce lesions in the most distal areas. The main toxic product of combustion is carbon monoxide. Another toxic gas of clinical relevance is hydrogen cyanide.
  • Lung injury of endogenous origin: patients with extensive burns may develop progressive respiratory failure after the initial phase, although they do not present direct damage of the airway by inhalation.

Diagnosis

The diagnosis of inhalation injury is, above all, clinical. It should be suspected when the patient is unconscious in a confined space where there has been a fire or escape of hot gas.

On physical examination the signs of suspicion are the finding of burned nose hair, dark sputum, burn on the face and nostrils, cough, hoarseness and whistling breathing.

It is important to explore the oropharynx to assess the alteration of the mucosa. The complementary diagnostic methods help assess lung and systemic damage. However, none of them is sufficiently specific nor does it allow a diagnosis to be made.

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Treatment

Most manifestations of lung injury appear after several hours of latency. For this reason, it is very important that any anomaly should proceed to mechanical ventilation.

However, there is no specific treatment for the critically burned patient by inhalation. The therapeutic approach is based on the maintenance of patency of the airway through intubation and mechanical ventilation in severe cases, pulmonary cleaning and the administration of antibiotics if there is infection.

Intubation and mechanical ventilation

The intubation is needed in up to 50% of patients with inhalation injuries. Severe cases require, as we have seen, early intubation with a large-bore tube to:

  • Keep the airway permeable.
  • Avoid aspiration.
  • Allow the elimination of secretions and mucus plugs.
  • Help ventilation.

In cases where intubation is done late when the patient presents severe edema of the airway, can make intubation impossible or have to resort to tracheotomy.

Mechanical ventilation should be aimed at maintaining oxygenation and ventilation avoiding damage induced by ventilation, using, according to the degree of lung damage, conventional ventilation with permissive hypercapnia, inhalation of nitric oxide, high frequency ventilation and extracorporeal membrane oxygenation.

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Other treatments

Prophylactic administration of corticosteroids and antibiotics has not shown any utility. In addition, in some studies the Corticosteroid treatment has been associated with an increase in lung infection and mortality. On the other hand, the presence of inhalation injury increases the need for expansion with liquids in the critical patient.