Question 13

Outline the pathophysiology and clinical features of a smoke inhalation injury in a patient with major burns.

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College Answer

Key Features

a) CO/CN toxicity – Lactic acidosis, high SvO2, mental confusion, hypotension
b) Upper airway obstruction from airway oedema – soot in the pharynx, singed hair, stridor, hoarseness, oropharyngeal erythema, oedema and blistering
c) Chemical burns to the lungs which result in mucosal damage, bronchitis, mucous plugging and pulmonary oedema – Bronchospasm, bronchorrhoea, raised a-a gradient

Discussion

Smoke inhalation injuries are discussed in greater detail in the answer to Question 26 from the first paper of 2012. One can divide this issue into mechanisms of thermal and inhalational injury, pathophysiological changes, damage at varying anatomical levels, and probably all of the above are reasonable approaches.

Presented in this fashion, it could even be turned into a table.

Everyone likes tables.

Mechanisms, Clinical Features and Management of Upper Airway Burns
Mechanism	Specific factors	Clinical features	Management
Thermal	Exposure to flames Splash with corrosives Inhalation of superheated smoke or steam	Facial burns Burns of the mucosa Soot on lips Carbonised material in the pharynx Carbonised material in sputum	Early assessment of airway patency Examination of the upper airway Serial assessments Upright positioning Suctioning of upper airway secretions Early elective intubation Referral to ENT for tracheostomy in case of severe burns, if strictures are anticipated
Inflammatory	Thermal damage to mucosa Effects of inhaled particles	Mucosal oedema Pharyngeal oedema Vocal cord oedema Tracheal oedema Difficulty swallowing Hoarse voice Cough Stridor Wheeze Increased work of breathing
Inhaled agents	Carbon monoxide Cyanide	"Cherry red" complexion Hypoxia despite normal SpO2 readings

Or, one can organise them by anatomical location:

Mechanisms, Clinical Features and Management of Upper Airway Burns
Anatomical location	Mechanism	Clinical features	Management
Face	Exposure to flames Splash with corrosives	Facial burns	Early assessment of airway patency Examination of the upper airway Serial assessments Upright positioning Suctioning of upper airway secretions Early elective intubation Referral to ENT for tracheostomy in case of severe burns, if strictures are anticipated
Oral cavity	Exposure to flames Splash with corrosives	Soot on lips Burns of the mucosa Mucosal oedema
Pharynx	Inhalation of superheated smoke or steam	Carbonised material in the pharynx Pharyngeal oedema Difficulty swallowing
Larynx	Inhalation of superheated smoke or steam	Hoarse voice Cough Vocal cord oedema Stridor Increased work of breathing
Trachea	Inhalation of superheated smoke or steam	Stridor Wheeze Tracheal oedema Carbonised material in sputum

A good summary of airway burns can be found in this 2012 article

References

Lund, Tjostolv, et al. "Upper airway sequelae in burn patients requiring endotracheal intubation or tracheostomy." Annals of surgery 201.3 (1985): 374.

Bartlett, Robert H., et al. "Acute management of the upper airway in facial burns and smoke inhalation." Archives of Surgery 111.7 (1976): 744-749.

Gaissert, Henning A., Robert H. Lofgren, and Hermes C. Grillo. "Upper airway compromise after inhalation injury. Complex strictures of the larynx and trachea and their management." Annals of surgery 218.5 (1993): 672.

Bishop, Sophie, and Simon Maguire. "Anaesthesia and intensive care for major burns." Continuing Education in Anaesthesia, Critical Care & Pain 12.3 (2012): 118-122.

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