Wednesday, April 27, 2016
By Will Rosenblatt, MD
Angioedema (AE) describes a medical finding. Care is directed at diagnosing the likely mechanism of the AE and administrating the appropriate therapy. Supportive care of the patient may involve management of the airway. An expectant and thoughtful approach is mandatory as the clinical picture of AE may suddenly and rapidly deteriorate.
Will Rosenblatt, MD, Professor of Anesthesiology, Yale School of Medicine, US
Angioedema (AE) is a clinical manifestation of an acute increase in vascular permeability that results in fluid shift into the subcutaneous tissue. Though AE may occur second to allergic reactions mediated by histamine, non-histiminergic AE is bradykinin mediated, more commonly involves the airway, is not associated with urticaria, and will be unresponsive to anti-hsitamines, corticosteroids and epinephrine. Bradykinin mediated AE is often associated with medications, most commonly Angiotensin Converting Enzyme inhibitors (ACEi), which decrease the metabolism of bradykinin. Hereditary-AE occurs due to a functionally abnormal C1-inhibitor, which likewise results in an accumulation of bradykinin. Though idiopahic AE cases are most often histamine associated, there are cases secondary to a bradykinin mechanism.
Airway involvement is more characteristic of a bradykinin mediated event. Laryngeal involvement has been found responsible for the majority of deaths in the hereditary type disease. In ACEi triggered events, the head and neck is the more commonly affected site. All types of AE may present with gastrointestinal symptoms. Hereditary type AE may appear to have a surgical abdomen.
Presentation may include normal hemodynamics. Alternatively, the shifting of intravascular fluid into the tissues may result in hypotension and tachycardia regardless of the AE mechanism.
The physical exam should involve a detailed and documented exam of the face, lips, oral cavity, tongue, soft palate and pharynx. Voice changes and stridor should be noted. Evidence of airway swelling require advanced diagnosis, most commonly with a flexible rhino-laryngoscopy. Some authors have suggested that swelling anywhere on the head and neck should heighten suspicion of airway compromise and should prompt advanced examination. Swelling noted the base of the tongue or in the larynx guide the need for advanced airway management. Radiologic imaging may be of limited value, delay the diagnosis and definitive and supportive treatment and require the patient to be transported to a poorly monitored and poorly accessible environment.
Patients who have signs of airway involvement may not require immediate airway management but should be observed in a highly monitored setting and undergo repeat examination. Those with no involvement may be medically treated and discharged home after several hours of observation without progression.
Though pulse oximetry and capnography are important measure of the airways competency, patients with normal oxygen saturations may still require advanced airway management.
The decision to manage the airway is made based on the patient’s respiratory and cardiovascular status and the physical exam, including flexible rhino-laryngoscopy. The approach to airway management will be considered below. The clinical care team must be aware that at the time of presentation and exam, the AE may be progressing and the airway may become more challenging over time.
Medical treatment of AE depends on the mechanism and/or insulting agent. A history of allergic reactions or previous hereditary or drug related AE events guides the diagnosis. Histamine mediated AE which presents with anaphylaxis (hypotension, urticarial, bronchospasm) is treated with epinephrine, H1 and H2 histamine blockers and corticosteroids. If the patient is unresponsive to these therapies, a misdiagnosis (e.g., Bradykinin mediation) should be assumed. Bradykinin mediated AE (including ACEi and hereditary forms) are treated with fresh frozen plasma or recombinant C1-inibitor concentrate.
The decision to manage the airway should be definitive. Though supplementary oxygen, nasal trumpets and oral airways, bag-valve-mask or CPAP and BiPAP may act as temporary measures, when the judgment is made that the airway is at risk, tracheal intubation is performed. Supraglottic airways have no role in care of these patients. The obstruction to air movement is below the level of the supraglottic airway rendering them most likely useless after the patient is becomes apneic.
The airway manager should have a high suspicion that the airway will be difficult to manage by routine direct laryngoscopy. Known or suspected edema of the base of the tongue or larynx may thwart attempts at direct laryngoscopy. A history of difficult airway management, independent of the current medical issues, should also be sought. Video laryngoscopy (VL), which bypasses much of the tongue base, should be considered, though expertise in tracheal tube delivery during VL differs from direct laryngoscopy practice and the operator should be practiced and skilled.
Use of direct laryngoscopy or VL will require induction agents and, most often, and muscle relaxant. The operator approaches induction with care, knowing that if there is failure to intubate the patient will likely not recover adequate oxygenation on their own and more invasive measures may be needed.
When direct laryngoscopy, VL and the concurrent use of induction agents is thought to entail significant risk, an awake intubation technique is chosen. Details of an awake intubation technique should be sought elsewhere. In general the technique will involve desiccation with intravenous anticholinergic agents, topical anesthesia of the airway from oral cavity and/or nares to the trachea and a careful, non-rushed procedure. Though a flexible fiberscope is most often used for tracheal tube delivery, any device with which the operator is skilled can be used.
Lastly, when there is a concern for airway compromise, including situations where the approach will be expectant observation, the clinician should be prepared to perform an emergency surgical airway. Equipment required for the technique preferred by the primary clinician should be by the bedside. Should the decision be made to proceed with airway management prudence will dictate the readiness of these materials and devices (e.g., if the airway is judged to have a high potential for difficulty, a cricothyrotomy kit may be opened and by the bedside.)
Angioedema describes a medical finding. Care is directed at diagnosing the likely mechanism of the AE and administrating the appropriate therapy. Supportive care of the patient may involve management of the airway. An expectant and thoughtful approach is mandatory for this clinical picture that may suddenly and rapidly deteriorate.
Angioedema – The decision to manage the airway should be definitive