When patients with anaphylaxis progress to cardiac arrest, there is likely to be associated significant hypotension, collapse of the cardiovascular system, hypoxemia, and asystole. Patients will require intravascular replacement. However, this is challenging due to the associated capillary leak that opposes intravascular fluid retention. Patients should be treated as with other patients undergoing cardiac arrest. The following therapies can also be used: 

• Fluid replacement: aggressive treatment is needed due to both vasodilation and capillary leak. Ensure good IV access with two large-bore IVs and administer large volumes (as much as 4-8L) rapidly. 
• IV antihistamines: while no good data is supporting this therapy, due to the mechanisms of action of anaphylaxis, there are likely little side effects from this treatment
• Corticosteroids: while these are not of benefit during cardiac arrest, it will be beneficial following ROSC. 
• Most patients will have PEA or asystole, and the algorithm for cardiac arrest should be used. 

Some case reports suggest that cardiopulmonary bypass can be effective. 

Special Treatment Considerations

Severe Airway obstruction

Close monitoring of the airway for edema is necessary. Early intubation may be necessary if there are signs of edema such as hoarseness, tongue or oropharyngeal edema, or significant bronchospasm. If the patient deteriorates clinically, rapid intubation without paralytic medications may be required. Note that as patients deteriorate rapidly, progressive airway edema (from the tongue to the larynx) may make intubation or cricothyrotomy near impossible. This is due to the anatomic shifts of airway edema. Additionally, facial edema can make bag-mask ventilation difficult due to a poor seal. Unsuccessful intubation attempts can further inflame the airway and make the situation more challenging as will hypoxia and associated combativeness.

In such cases, surgical airways (cricothyrotomy) may be the best option. Alternatively, a flexible fiberoptic intubation can help with direct visualization. Other options include blind intubation using palpation or laryngeal mask airways.