Initial assessment of the burn patient should include evaluation of the airway and breathing.
Considerations STEP 1
As respiratory failure is immediately life threatening, including an evaluation of the airway and breathing in the initial assessment of any trauma patient is unarguable. Assessment of the airway and breathing are universally advocated by life support training programs as the ﬁrst steps in assessment of trauma cases [58–60]. Oropharyngeal burns can rapidly cause obstruction, and other causes of critical respiratory failure, such as coma, require immediate diagnosis and treatment.
Balance of beneﬁts and harms
Loss of upper airway patency due to progressive edema from inhaled hot gases will lead to death if insufﬁcient cross-sectional area of the trachea and larynx is available for respiratory exchange. Similarly, the progression of damaged lung parenchyma to respiratory distress syndrome following exposure to inhaled toxicants will result in pneumonia or death. Respiratory injury is the major cause of death in patients injured in structure ﬁres .
Values and preferences
Decentralization of care throughout many countries of the world, especially in RLS, means that the frequency with which patients may present with smoke inhalation injury may be quite low in rural areas. Recognition of inhalation injury presupposes the existence of resources for providing appropriate treatment. In some cases, humidiﬁed supplemental oxygen will be sufﬁcient supportive care until upper airway edema subsides, but the need for endotracheal intubation and ventilatory support may exceed the capabilities of all but a few speciality hospitals in RLS.
Evaluation of airway and breathing require only education of health care providers; there is no need for specialized equipment or supplies. In addition, evaluation of airway and breathing is a standard item in all trauma care educational programs. Therefore, no additional costs are envisaged by inclusion of airway and breathing in the initial assessment of burn patients.
Diagnosis of inhalation injury is suspected by a history of exposure within a closed space to products of incomplete combustion, in the physical examination by diminished consciousness, and by the presence of soot in the oral cavity and by facial burns. Normal oxygenation or chest radiographs do not exclude the diagnosis. However, signs such as hoarseness, carbonaceous sputum, wheeze, and dyspnea are strongly suggestive of inhalation injury.
Considerations STEP 2
Evidence for this recommendation is weak, not least because the deﬁnition of inhalation injury is imprecise. The term ‘‘inhalation injury’’ comprises three main components, which can occur separately but which frequently present in combination. These components are:
1. Systemic poisoning due to the inhalation of gases produced by combustion, such as carbon monoxide (CO) and hydrogen cyanide (HCN).
2. Obstruction of the upper airways due to the effects of heat and subsequent edema.
3. Injury to the lower respiratory system due to the inhalation of noxious chemicals and particulates present in smoke. As each type of injury is potentially fatal, inhalation injury should be suspected if the presenting history, symptoms or signs suggest the possibility.
Carbon monoxide poisoning is suggested by diminished consciousness together with a history of exposure to ﬁre in an enclosed space. Hydrogen cyanide poisoning, which may also be present, produces similar signs. The differential diagnosis includes diminished consciousness from other causes, especially inebriation from alcohol and other drugs, which may have a similar presentation. (The eventuality that a ﬁre may be caused by a prior deterioration of consciousness should also be considered.) Diagnosis of carbon monoxide poisoning is conﬁrmed by measurement of blood carboxyhemoglobin (COHb), which should be performed in all patients in whom inhalation injury is suspected.
Obstruction of the upper airway: In burns to the face, assessment of potential obstruction by edema of the upper airway is more problematic and requires insight into burn wound pathology. Evidence of burning within the buccal cavity (e.g., blistering of the mucosal membrane), or symptoms such as hoarseness or stridor suggest that airway obstruction is imminent, warranting rapid intervention to secure airway integrity. A limited superﬁcial burn to the face, such as a scald burn, is less likely to be problematic. Edema formation in the head and neck may be insidious and obstruction can become manifest within up to 24 h or longer post burn. The clinical approach is discussed below.
· The presence of soot in the oral cavity is indicative of smoke inhalation.
· Signs and symptoms such as hoarseness, wheeze, cough, tachypnea, and hypoxemia can be present on admission or may develop within up to 48 h after exposure.
· The initial chest X-ray is often normal.
· Diagnosis is generally accepted as positive by the detection of soot in sputum in combination with any of the above ﬁndings, or by the observation on bronchoscopy of damaged mucosa below the larynx .
Balance of beneﬁts and harms
The technique for initial assessment (see Recommendation 1 above) of the patient with suspected inhalation injury is a rapid, sensitive, but non-speciﬁc approach to ensuring that patients with potentially life-threatening injuries are identiﬁed. Subsequently a more thoughtful and considerate approach to establishing the diagnosis must be carried out because the supportive treatment indicated by a diagnosis of inhalation injury (i.e., endotracheal intubation and ventilatory support) not only introduces the patient the risk of iatrogenic harm, but also requires the expenditure of signiﬁcant resources.
Therefore, the ideal screening tool for inhalation injury would not only be highly sensitive (thus avoiding the loss of life due to missed diagnosis) but also speciﬁc, avoiding intubation of patients who do not need to be intubated. For example, singeing of facial or nasal hair, hoarseness, and expectoration of carbonaceous sputum are ‘‘sensitive’’ signs because they are present in nearly all patients with inhalation injury, but they are not ‘‘speciﬁc’’ because many patients with these signs do not have clinically signiﬁcant inhalation injury. There remains an ongoing dilemma about which patients require early intubation to prevent loss of airway after smoke inhalation.
Values and preferences
Fortunately, the diagnosis of CO poisoning can be made deﬁnitively by the assay of COHb. However, there is not a universally accepted standard for the diagnosis of thermal injury to the upper airway or of signiﬁcant damage to the lower airways. For example, even within resource-abundant settings, there is variation among burn centers on the routine use of ﬁberoptic bronchoscopy for the initial diagnosis of inhalation injury .
The diagnosis of inhalation injury requires considerable skill and experience. Furthermore, diagnosis implies the availability of resources to respond to a positive diagnosis; inhalation injury can only be managed in a well-equipped intensive care unit. COHb measurements can be made with little additional cost to the basic cost of an arterial blood gas analysis. However, if the facility lacks the basic equipment to obtain and analyze arterial blood gases, diagnosis will be made on clinical grounds only. The advantage of proper diagnosis and timely treatment of CO poisoning is the elimination of unnecessary deaths and neuropsychological disability, which reduce the indirect medical costs to the community. Similarly, there are signiﬁcant costs of providing ﬁberoptic bronchoscopy, which may be ultimately defrayed in the reduction of unnecessary deaths or prolonged hospital stay. However, even in resourcerich settings, in the great majority of cases diagnosis is made primarily on clinical appearances.
Treatment for suspected or conﬁrmed carbon monoxide poisoning is administration of high-ﬂow supplemental oxygen for at least 6 h.
Considerations STEP 3
Although, for obvious reasons, no comparative clinical studies are available, the recommendation is based on well-established principles of pharmacology and physiology. Carbon monoxide is a colorless, odorless gas that is produced by the incomplete combustion of hydrocarbon fuels. CO diffuses rapidly and competitively binds with hemoglobin, displacing oxygen, which results in hypoxemia. The afﬁnity of CO for hemoglobin is approximately 200 times that of oxygen. In addition, CO binds to cytochromes, interfering with cellular oxygen utilization. Hypoxemia caused by CO poisoning is not detected by pulse oximetry or by partial pressure of oxygen (pO2) measurements. The COHb binding is stable, with a half-life of up to 4 hour in a person breathing air. Increasing the arterial pO2 accelerates CO displacement from the hemoglobin molecule; administration of 100% oxygen shortens the half-life of COHb to 40–60 min . Therefore, patients suspected of having CO poisoning should immediately be given oxygen, preferably via a non-rebreathing mask, at a rate of 8–15 L/min, depending on mask design. Treatment should be maintained for at least 6 h, or longer if symptoms persist. The indication for intubation and mechanical ventilation is dictated by the level of consciousness.
Hyperbaric oxygen: From theoretical considerations, one would conclude treatment by hyperbaric oxygen would further accelerate elimination of CO, but practical difﬁculties of monitoring and providing ongoing vital care preclude this mode of treatment in most instances. A systematic review of hyperbaric oxygen treatment found insufﬁcient evidence to recommend its use .
Hydrogen cyanide (HCN) is released by the combustion of nitrogen-containing compounds, which are present in plastics, fabrics and paper. Cyanide interferes with intracellular oxygenation, principally by inhibition of cytochrome oxidases. There is substantial evidence that hydrogen cyanide is commonly inhaled by ﬁre victims  and may contribute to morbidity and mortality. The half-life of cyanide in man is approximately one hour . Presenting signs and symptoms are similar to those of CO poisoning. Empirical treatment involves administration of high-ﬂow oxygen. Speciﬁc antidotes are advocated, especially hydroxocobalamin, which binds to cyanide and is relatively non-toxic; but administration must be immediate for any effect to be useful .
Balance of beneﬁts and harms
The use of increased levels of inspired oxygen content to reduce the amount of CO bound to Hb is therapy that is presumed to be effective at reducing morbidity and mortality from CO poisoning is a presumption that is not supported by randomized, clinical trials, yet is so theoretically sound that it deﬁes challenge. Similarly, the early effects of the inhalation of smoke on the trachea-bronchial tree result in hypoxia, which again is treated by the administration of oxygen. While there is evidence that the prolonged administration of oxygen at inspired concentrations above 40% may cause parenchymal damage, the use of oxygen as an initial treatment of ﬁre victims is logical and potentially life-saving.
Values and preferences
The use of supplemental oxygen in patients extricated from structure ﬁres or exposed to smoke is dependent on provision of this simple therapy throughout pre-hospital and basic hospital systems throughout RLS. The lack of randomized, prospective clinical trials to support this recommendation is likely to remain because it would be unethical to perform a trial in which supplemental oxygen administration would be withheld.
Pre-hospital care systems are either poorly developed or nonexistent in RLS, yet provision of supplemental oxygen can be found in many basic hospitals and some clinics. In resourceabundant settings, established pre-hospital care systems routinely provide supplemental oxygen therapy. Where supplemental oxygen is a treatment available for administration, the other critical step is providing health care providers with necessary education so that appropriate patients will be selected for support. The cost of education for this particular modality can be bundled with the other educational activities proposed in these recommendations.
Treatment of upper airway burns secondary to smoke inhalation includes observation and monitoring. Patients with upper airway burns should be nursed in the semi-upright position with moderate elevation of the head and trunk. Endotracheal intubation or tracheostomy is indicated if airway patency is threatened.
Considerations step 4
Although evidence supporting this recommendation is weak, the management of upper airway burns with respect to airway patency is a clinical necessity. As edema formation continues for many hours, continuous monitoring and frequent assessment are essential.
Moderate elevation of the head of the bed allows gravity to help reduce airway edema by facilitating venous and lymphatic drainage, and is therefore a sensible, critical standard practice. The patient should be given oxygen by mask to maintain adequate arterial oxygen saturation. Suction should be used to keep the airway clear of debris and secretions.
To protect the airway, the presence of burns inside the oral cavity and the occurrence of stridor are strong indications for immediate intubation. Other signs for concern include tachypnea, hoarseness and the use of accessory respiratory muscles.
Children are at greater risk of obstruction, as are patients whose burns include circumferential burns to the neck. Other early signs and symptoms of respiratory dysfunction may be more suggestive of smoke inhalation. These signs include a ‘‘brassy’’ cough, wheezing and breathlessness. Arterial oxygen desaturation despite oxygen therapy by mask is an important marker of respiratory compromise.
In many cases of upper airway burns, it is prudent to observe and hold off on immediate intervention. On the other hand, failure to intervene presents a risk of airway obstruction later as edema develops. If delayed, laryngoscopy and intubation may be hazardous, due to the presence of pharyngeal edema. The clinical decision to intubate in order to protect the airway depends on the availability of technical expertise and facilities and, above all, on the clinical insight of the physician in charge. The decision is often facilitated by the presence or absence of signiﬁcant smoke inhalation, which requires mechanical ventilation to maintain adequate gas exchange.
No evidence supports the use of tracheostomy in burn patients. In a recent survey of American burn centers, tracheostomies were most frequently performed at 2 weeks, but most respondents agreed that early tracheostomy was indicated under certain circumstances . Indications cited included predicted need for prolonged mechanical ventilation, burns of head and neck, and failure to wean. The conventional surgical procedure was preferred to the percutaneous method, especially in the presence of neck burns. In all cases requiring intubation, meticulous hygiene of the oropharynx and trachea are mandatory to prevent the occurrence of ventilatorassociated pneumonia (VAP).
Balance of beneﬁts and harms
This recommendation describes the best practice of care for patients with inhalation injury. Although not supported by prospective, randomized, clinical trials, this recommendation summarizes the consensus of experienced burn clinicians, both nurses and doctors. As such, this practice of care may be effective at reducing, but not eliminating the complications associated with inhalation injury. However, intubation and ventilation may cause harm. Apart from the obvious risks of accidental extubation and mechanical obstruction, there is growing awareness of the risks of mechanical ventilation itself (see Recommendation 5), patients require increased administration of sedatives and analgesics and are no longer able to maintain homeostasis. Intensive care facilities are then essential for the provision of appropriate ﬂuids and nutrition.
Values and preferences
Consistent with support for the recommendations above, education is key to instituting this recommendation into consistent clinical practice. However, barriers to ensuring permanent implementation of these care plans include large volumes of patients, shortage of human resources, and the absence of clinical standards for intensive care.
The resources required for optimal clinical care plans for patients with inhalation injury are high. The provision of intensive care requires investment in human resources, education and facilities and therefore represents a considerable ﬁnancial commitment. The ability to provide optimal care for patients with inhalation injury is therefore dependent on the availability of expensive intensive care facilities and clinical expertise.
In those patients requiring ventilatory support, lung protective strategies should be employed. Prophylactic antibiotics and corticosteroids are not indicated for the treatment of smoke inhalation injury.
Considerations STEP 5
In the past 15 years evidence has accumulated from studies in the intensive care unit (ICU) that positive pressure mechanical ventilation is associated with lung injury (ventilator-associated lung injury, VALI) and acute respiratory distress syndrome (ARDS). It is suggested that damage to small airways and alveoli is caused by the mechanical forces transmitted by cyclical positive inﬂating pressures . Various studies show improved survival using low tidal volumes in patients with ARDS . For this reason, lung protective strategies, maintaining plateau pressures below 31 cm H2O and tidal volumes below 7 mL/kg, are being increasingly adopted in the ICU setting .
Efforts to apply protective ventilation strategies to burn patients have been problematic . The effect of smoke inhalation on VALI is unknown and thoracic compliance may be affected by burns to the thorax and abdomen. Above all, the hypermetabolic response to burn markedly increases the demand for respiratory gas exchange. A recent survey in North American burn centers found a wide variation of ventilator practices, with reported difﬁculties in adhering to low tidal volume strategies, suggesting that burn patients on ventilators may comprise a unique subpopulation . At the present time, while conventional ICU ventilation guidelines may not be pertinent, it nevertheless seems prudent to assume that VALI also occurs in burn patients. Therefore, the use of the lowest possible inﬂation pressures and tidal volumes, compatible with respiratory demands, is suggested for the mechanical ventilation of burn patients. At the same time, it is acknowledged that the optimal approach to mechanical ventilation in burn patients has yet to be established.
Ventilator-associated pneumonia is common and potentially fatal . Scrupulous hygiene around the head and neck area, including the oropharynx, and regular clearing of the airways under sterile conditions are essential. Measures that help to reduce ventilation requirements include nursing in a semi-upright position and escharotomies as appropriate for burns to the trunk, both of which increase total lung compliance. Empirically, maintenance of optimal ﬂuid balance and other aspects of general burn care, such as nutrition, effective wound coverage and pain control, all reduce the hypermetabolic response, which decreases the respiratory demand.
Corticosteroids are not recommended for the initial treatment of inhalation injury . Humidiﬁcation of inspired gases helps prevent mucus retention. Mucolytic agents such as acetylcysteine and bronchodilator therapy may be useful adjuncts. Antibiotics have no effect on inhalation injury until infection supervenes, when the choice of antibiotics should be based if possible on the antibiograms of the causative microorganisms.
In conclusion, inhalation injury is a potentially lifethreatening condition which can lead to respiratory failure from a number of mechanisms. Recognition of inhalation injury and the subsequent monitoring of vital signs are essential. Initial treatment comprises the administration of oxygen in high concentration. A conservative approach is advocated if clinically appropriate, but intubation and mechanical ventilation may be life-saving. Respiratory support is not a cure, and all measures to promote body homeostasis and wound healing should be aggressively pursued.
Balance of beneﬁts and harms
This recommendation is supported by the scientiﬁc literature and by expert clinical opinion. Clinical practice that is consistent with this recommendation results in improved outcomes, including fewer complications and reduced mortality. Additionally, this topic is a ﬁeld in which there are many promising research endeavors currently underway, many of which should help guide improvements in future care.
Values and preferences
Endotracheal intubation and mechanical ventilatory support are now more common in RLS, but optimal ventilation requires continuous monitoring and frequent adjustments, posing additional strains on limited resources. Again, education will play a key role in ensuring that these principles will be employed in the care of patients with inhalation injury.
Dissemination of these clinical recommendations is an ongoing responsibility of national, regional and international burn care associations. However, there is an equal responsibility of health care facilities and practitioners to guarantee that management of inhalation injury is an ongoing priority for continuing medical education activities. Thus, as in Recommendation 4 above, there is a considerable logistical challenge to provide the support of hospital administrators and government health ofﬁcials, as well as the commitment of health care professionals to acquiring and maintaining standards of care in this ﬁeld.
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