Abbreviated Injury Score (AIS) for Inhalation Injury
Use in adult patients with suspected inhalation injury undergoing flexible bronchoscopy.
Adult patients with suspected inhalation injury undergoing flexible bronchoscopy.
- May predict development of ARDS, length of time on mechanical ventilation, and prolonged ICU stay.
- Some studies have found a non-statistically significant trend towards worse outcomes with higher AIS.
- AIS severity has not been consistently associated with mortality (Sheridan 2016).
- Cannot reliably predict need for high fluid resuscitation requirements.
- A typical flexible bronchoscope is on average 5 mm in diameter. Hence, bronchoscopy can only identify proximal airway changes and not the narrower distal and peripheral airway changes. Thus, bronchoscopic findings cannot be fully relied upon to accurately reflect the overall severity of airway inhalation injury.
- No universal consensus exists on grading for inhalation injury. The AIS has been widely utilized as the predominant bronchoscopic inhalation injury severity score in the literature (but have not been compared head to head with other bronchoscopic criteria).
- Of note, a multicenter prospective cohort study by the American Burn Association is currently underway to develop and validate a scoring system for inhalation injury based on clinical, radiographic, bronchoscopic, and biochemical parameters.
Please fill out required fields.
High AIS severity alone should not dictate management decisions, which should as always be made in conjunction with history, physical exam, and laboratory findings.
- Supportive treatment is the primary means of inhalation injury management, as there is very little in the way of pharmacologic treatment once the inhalation injury has occurred.
- Bronchoscopy can play a therapeutic role in airway clearance as necrotic tissue and eschar can form pseudomembranes, sloughing of mucosa, and bronchial obstruction.
- Other measures include intensive bronchial hygiene, including bronchodilators (e.g. inhaled β2 agonists), frequent chest physiotherapy, and early patient ambulation).
- Upper airway edema can progress, particularly over the first 24 hours after injury, necessitating intubation. If mechanical ventilation is required, a high frequency percussive mode of ventilation can be considered, as some studies have shown benefit to this patient population. A lung-protective, low tidal volume ventilation strategy (6-8 cc/kg of predicted body weight) is preferred in adults.
- Other supportive measures have been used with varied success, including prone positioning, extracorporeal membrane oxygenation (ECMO), inhaled anticoagulants (e.g. heparin, antithrombin), and inhaled N-acetylcysteine (NAC).
- Additionally, referral to a designated burn center should be considered if any inhalation injury is present, according to American Burn Association guidelines.
Macroscopic manifestations of airway abnormalities may be delayed and hence, falsely reassure the clinician that inhalation injury has not occurred (Hunt 1975).
Selection of the appropriate findings:
No carbonaceous deposits, erythema, edema, bronchorrhea, or obstruction
Minor or patchy areas of erythema, carbonaceous deposits, bronchorrhea, or bronchial obstruction present
Moderate erythema, carbonaceous deposits, bronchorrhea, or bronchial obstruction present
Severe inflammation with friability, copious carbonaceous deposits, bronchorrhea, or obstruction present
Mucosal sloughing, necrosis, or endoluminal obstruction present
Facts & Figures
*From Endorf and Gamelli.
The AIS for inhalation injury was first proposed by Endorf and Gamelli in 2007. The purpose of their study was to identify whether severity of inhalation injury correlated better with pulmonary parameters (e.g. lung compliance, PaO2:FiO2 ratio) and acute fluid resuscitation requirements than bronchoscopically assessed inhalation injury severity. They retrospectively reviewed 80 adult patients requiring intubation, mechanical ventilation, and flexible bronchoscopy for suspected inhalation injury within the first 24 hours of admission. They used the AIS classification to separate their patients into two groups of bronchoscopic inhalation injury: one including grades 0 and 1 and another including grades 2, 3, and 4. They compared characteristics, such as fluid resuscitation requirements, initial oxygenation, lung compliance, and duration of mechanical ventilation; only bronchoscopic severity correlated with decreased survival (p = 0.03).
Hassan et al also found a significant (p <0.01) increase in mortality with bronchoscopic severity. They did not use the AIS.
Since 2007, a number of studies have used AIS in order to establish a clear relationship between bronchoscopic grade of injury and a range of clinical outcomes; however, the results have been varied. For instance, in contrast to Endorf and Gamelli’s study, Albright et al (2012), Mosier et al (2012), and Spano et al (2016) all found that increasing AIS grade did not have a significant effect on mortality, with p-values of 0.21, 0.10, and 0.15, respectively.
Albright et al did show that increasing severity was associated with longer ventilator days (p = 0.036) and intensive care unit (ICU) stay (p = 0.040). Additionally, Mosier et al noted a significant association between AIS grade severity and development of acute respiratory distress syndrome (ARDS) at 24 hours (p <0.01).
Original/Primary ReferenceEndorf FW, Gamelli RL. Inhalation injury, pulmonary perturbations, and fluid resuscitation. J Burn Care Res. 2007;28(1):80-3.
ValidationAlbright JM, Davis CS, Bird MD, et al. The acute pulmonary inflammatory response to the graded severity of smoke inhalation injury. Crit Care Med. 2012;40(4):1113-21.Mosier MJ, Pham TN, Park DR, Simmons J, Klein MB, Gibran NS. Predictive value of bronchoscopy in assessing the severity of inhalation injury. J Burn Care Res. 2012;33(1):65-73.
Other ReferencesWalker PF, Buehner MF, Wood LA, et al. Diagnosis and management of inhalation injury: an updated review. Crit Care. 2015;19:351. Hassan Z, Wong JK, Bush J, Bayat A, Dunn KW. Assessing the severity of inhalation injuries in adults. Burns. 2010;36(2):212-6.Sheridan RL. Fire-Related Inhalation Injury. N Engl J Med. 2016;375(5):464-9.Hunt JL, Agee RN, Pruitt BA. Fiberoptic bronchoscopy in acute inhalation injury. J Trauma. 1975;15(8):641-9.Spano S, Hanna S, Li Z, Wood D, Cartotto R. Does Bronchoscopic Evaluation of Inhalation Injury Severity Predict Outcome?. J Burn Care Res. 2016;37(1):1-11.
About the Creator
Frederick W. Endorf, MD, is a general surgeon affiliated with Hennepin County Medical Center in Minneapolis and the American Burn Association. His research interests include burns, trauma, and reconstructive surgery.
To view Dr. Frederick W. Endorf's publications, visit PubMed
About the Creator
Richard L. Gamelli, MD, FACS, is professor emeritus at the Stritch School of Medicine at Loyola University Chicago. He has served as the director of the Burn and Shock Trauma Research Institute, chairman of the department of surgery, and chief of the burn center at Loyola University Medical Center. Dr. Gamelli has published over 175 peer-reviewed manuscripts and abstracts, written 30 book chapters, and edited 10 books.
To view Dr. Richard L. Gamelli's publications, visit PubMed
- Pujan H. Patel, MD