|Year : 2015 | Volume
| Issue : 3 | Page : 283-286
Beyond the fire: smoke inhalational injury as a respiratory concern
Ayman M Kamaly MD
Department of Anesthesiology, Intensive Care & Pain Medicine, Ain Shams University, Cairo, Egypt
|Date of Submission||29-May-2015|
|Date of Acceptance||29-May-2015|
|Date of Web Publication||29-Jul-2015|
Ayman M Kamaly
Department of Anesthesiology, Intensive Care & Pain Medicine, Ain Shams University, Cairo
Source of Support: None, Conflict of Interest: None
In fire events, smoke inhalation is the leading cause of death in survivors of the primary fire mortality. Direct upper airway thermal injury is only one of the contributing mechanisms. Others may be related to the nature of the combusted (or incomplete combusted) materials in the scene; eg.; aldehydes, sulphur oxides and nitrogen as a cotton combustion products, while burning polyvinylchloride (PVC's) releases carbon monoxide (CO) and hydrochloric acid, among more than 75 potentially toxic compounds including cyanide.
Hot carbonated gaseous materials and soot may lead to supraglottic, glottic, or infraglottic airway obstruction however; significant hypoxemia is not the typical sign in acute cases without aspiration or parenchymal lung injuries. Injury may not manifest until after 48 hours.
Keywords: burn injury, inhalation injury, respiratory, smoke
|How to cite this article:|
Kamaly AM. Beyond the fire: smoke inhalational injury as a respiratory concern. Ain-Shams J Anaesthesiol 2015;8:283-6
| Overview|| |
In fire-related events, smoke inhalation is the leading cause of death in survivors of the fire. Direct upper airway thermal injury is only one of the contributing causes. Other reasons may be related to the toxic nature of the combusted (or partially combusted) materials at the scene - for example, aldehydes, sulfur oxides, and nitrogen as products of cotton combustion; in addition, burning polyvinylchloride releases carbon monoxide and hydrochloric acid, among more than 75 potentially toxic compounds, including cyanide.
Hot carbonated gaseous materials and soot may lead to supraglottic, glottic, or infraglottic airway obstruction. However, significant hypoxemia is not the typical sign in acute cases without aspiration or parenchymal lung injuries. Injury may not manifest until 48 h.
The American College of Surgeons Committee on Trauma lists the following as 'Clinical indicators' of existence of smoke inhalation:
- Facial burns.
- Singeing of nasal hair or eyebrows.
- Oropharyngeal acute inflammatory changes (swelling, ulceration of oral mucosa, or tongue).
- Soot (carbonaceous materials) in the oropharynx or sputum.
- Airway obstruction, hoarseness, or wheezing.
- A history of impaired mentation (or unconsciousness) and/or being trapped in a burning location.
- Carboxyhemoglobin level more than 10% if the patient is involved in a fire.
| Airway control|| |
Airway clearance techniques
- Tracheal intubation
Emergency intubation is needed in smoke inhalation patients with the following conditions (Level-I Recommendation):
- Airway obstruction.
- Severe cognitive impairment (Glasgow Coma Scale score ≤8).
- Major cutaneous burn (≥40%).
- Impending airway obstruction:
- Moderate/severe facial burn.
- Moderate/severe oropharyngeal burn.
- Moderate/severe airway injury seen on endoscopy.
- Expected prolonged transport time.
- Technical points:
- Securing the endotracheal tube (ETT) may be difficult due to burned adjacent skin and evolving edema. Do not cut the ETT (especially in children) as the expected swelling may render the 'cut tube' too short, and the risk of increasing the dead space is relatively minor.
- Nasal intubation is preferred in children as a general rule.
- Maintaining head-up position at 30°-45° helps gradual drainage of edema by gravity.
- Caution with using succinyl choline for intubation if the burn or smoke injury is older than 24 hours.
- Indications: Conventionally, tracheostomy is indicated for those who seem to be unready for extubation after 14 days of intubation. However, controversy still exists for indications and timing of early tracheostomy, challenging the value of the specificity of '14 days' in burn patients. Better bronchial hygiene, less sedation requirement, better airway securing, and possible easier weaning are all potential advantages of early tracheostomy, which are to be weighed against logical disadvantages of being an invasive maneuver with recognized morbidities.
- Timing: At 10-12 days of ventilation, all patients should be evaluated for possibilities of readiness of weaning or elective tracheostomy. Indicators for prolonged need of ventilator support in 'smoke inhalation' patients are burn injury greater than 50%, full thickness burn greater than 20%, and age more than 50 years. Elective early tracheostomy should be considered if the previous indicators are present, in the earliest possible chance.
- Technique: Both open and percutaneous routes are acceptable techniques, but the decision may be influenced by the skin condition, nature of burn, and its degree in the neck area.
Impaired cough mechanics and reflex are related to pain, medications, or invasive airway instrumentation and devices (ETT). Absence of natural clearing effect of cough reflex will result in retained secretions, atelectasis, and eventually pneumonia.
Encouraging voluntary cough by instructing the patient to take in a 'small breath' followed by a 'small cough', and then escalating breaths and coughs until an effective cough that aids airway clearance is reached.
An alternative interventional effective technique is carried out by massaging the suprasternal notch area by placing the middle and index fingers in a flat position and performing gentle circular massage over the trachea in an inward direction.
ETT between the vocal cords prevents normal approximation of the cords needed to create adequate pressure for coughing. In such patients, cough can be stimulated by increasing the ETT-cuff pressure (closing the glottic space) when delivering manual rapid large inspiratory cycle, followed by rapid sudden release and expiration, using Ambu or circuit bag.
Therapeutic cough maneuvers should be attempted and encouraged every 1-2 h during day time.
- Bronchopulmonary gravity-assisted drainage: The idea is to utilize gravity by positioning the patient in a position suitable to drain retained secretions. However, not all gravity-favoring positions are practical for burn patients. Actually, the Trendelenberg position, which is the most optimal position, can worsen oxygenation and blood gases. The practical option is alternation of position every 1-2 h.
- Chest percussion: Percussion helps in secretion mobilization along the bronchial segments to larger airways. Percussion should be designed to follow the bronchial segments' surface anatomy. Gentle cupping should be carried out with one hand at a time, with a thin towel placed on the patient's skin to minimize skin trauma.
- Chest vibration: This therapy is performed for those who cannot tolerate chest percussion or for those with burns, with the aim to loosen secretions for easy expulsion. The clinical indicator of effective pulmonary physiotherapy is improved breath sounds.
- Indication: Airway suctioning is indicated in case of failure of airway clearance with pulmonary physiotherapy maneuvers. Nasotracheal suctioning is an alternative to intubation that is intended only for suctioning.
- Technique: Preoxygenation is carried out for few minutes, followed by 'head-up' position, before slowly advancing a catheter through the nostril until airflow is heard or felt, indicating the nearest point from the vocal cords. The catheter is advanced 'during inspiration' and the suctioning is performed while withdrawing it out. The maximum allowable period is 10-15 s of suctioning, and the operator is advised to 'hold his breath' during suctioning to alert him of patient's hypoxia.
Fiberoptic bronchoscopy is indicated when all the above maneuvers are ineffective in clearing the airway from foreign materials or secretions. Flexibility and small diameter of modern models allow reaching down to the fifth bronchial tree generation achieving bronchial clearing and pulmonary recruitment.
- Bronchodilators: Inflammatory changes due to inhalational injury causes reactive airway causing bronchospasm and wheezing. Sympathomimetics help bronchial muscle relaxation as well as mucosal vasoconstrictor action. Aerosolized epinephrine may be prescribed every 2-4 h guided by heart rate change.
- Mucolytic agents: Oral or nebulized/aerosolized N-acetylcysteine, in addition to being general oxygen free radical scavenger, is an effective mucolytic agent secondary to its sulfhydryl-group, which attacks the disulfide bond of mucus rendering it unstable and less viscid. However, its acidic nature makes it irritant to respiratory mucous membrane, which may cause bronchospasm. Aerosolized heparin/N-acetylcysteine have been described for successfully reducing fibrin formation, resulting in decreased peak airway pressure and atelectasis, thereby improving the final outcome, especially in the pediatric population. The usual prescribed dose is 5000-10 000 IU heparin in few milliliters saline to be nebulized every 3-4 h alternating with N-acetylcysteine. Needless to mention, baseline and daily clotting studies for the systemic effect of heparin need to be recorded.
- Sputum culture for intubated cases every other day.
- Early ambulation (as early as 4-5 days postoperatively) with effective pain control. Even those on ventilator support can be ambulated in wheelchair to preserve muscular tone.
Detailed ventilator settings and modes of ventilations are beyond the scope of this article. Thus far, there is no evidence-based information that defines the most optimal ventilator mode; therefore, we should consider all ventilating modes acceptable (whether classic modes or the newly emerged modes or techniques in the last decade), as long as oxygenation and ventilation are achieved adequately.
General recommended guidelines for ventilator management
- Choosing the mode: Regardless the fancy and attractive properties of the ventilation mode, the clinician should utilize the mode he or she is familiar with and skilled in, to achieve acceptable oxygenation and ventilator levels.
- Targeted arterial blood gas goals
- pH of 7.25-7.45.
- PaO 2 of 55-80 mmHg or SaO 2 of 88-95%.
- PaCO 2 of 35-55 mmHg, with permissive hypercapnia if pH is greater than 7.25.
- Tidal volume: An initial tidal volume of 6-8 ml/kg should be primarily considered, unless impaired oxygenation or increased PaCO 2 is noted. If these parameters are impaired, aggressive pulmonary physiotherapy and bronchial clearing attempts should be made first, before considering increasing tidal volume up to 8-10 ml/kg. Secretions and fibrin casts are usually a reversible cause of hypoxemia and hypercarbia.
- Plateau pressure: A plateau pressure less than 35 cmH 2 O should always be targeted, unless there is restricted chest-wall compliance due to bandages or burn scars. This level of plateau pressure should be maintained even at the expense of increased PaCO 2 (permissive hypercarbia), unless affecting the pH status. Higher levels carry risks of barotraumas and parenchymal lung injury.
- Positive end-expiratory pressure: Positive end-expiratory pressure could be used as a tool to maintain oxygenation levels, with increments. If oxygenation is jeopardized by using small tidal volume strategies, high positive end-expiratory pressure levels with large tidal volume (8-10 ml/kg) to keep targeted PaO 2 and oxygen saturation is recommended.
- General guidelines: The improved ventilator and oxygenation parameters with readiness for extubation do not reflect the capability of protecting the upper airway after extubation. Bronchoscopic evaluation for subsidence of airway edema should precede extubation attempts.
Tracheomalacia, tracheitis, tracheal ulceration, or tracheal stenosis may complicate the prolonged intubation course of the patient. Postintubation stricture may be due to damage at the stomal site (tracheostomy), cuffs (overinflation), ETT size (large bore), ETT movement, (spontaneous/assist ventilation/heavy circuit), or simple prolonged mucosal exposure to forging body (ETT). Other causes include steroid, diabetes, infection, prolonged hypotension (ischemic tracheal mucosa), or prolonged use of nasogastric tube. The management may result in a major surgical correction procedure.
Chronic airway disease
Obstructive or restrictive diseases may be a rare fate of inhalational injury. In most cases, the majority of pulmonary abnormalities and symptoms decline in a few months. However, there are rare cases reported in which pulmonary function impairment lasted up to few years.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| Suggested readings|| |
- Dunham CM, Barraco RD, Clark DE, Daley BJ, Davis FE 3rd, Gibbs MA, et al. Guidelines for emergency tracheal intubation immediately after traumatic injury. J Trauma 2003; 55:162-179.
- Mlcak RP, Suman OE, Herndon DN. Respiratory management of inhalation injury. Burns 2007; 33:2-13.
- Miller AC, Rivero A, Ziad S, Smith DJ, Elamin EM. Influence of nebulized unfractionated heparin and N-acetylcysteine in acute lung injury after smoke inhalation injury. J Burn Care and Research 2009; 30:249-256.
- Sellers B, Davis BL, Larkin PW, Morris SE, Saffle JR. Early prediction of prolonged ventilator dependence in thermally injured patients. J Trauma 1997; 43:899-903.
- Herndon DN. Inhalation injury. In: Herndon DNed. Total burn care. 2nd ed. Philadelphia, PA: Elsevier; 2002: 242-253.