Anaphylaxis in adults: diagnosis and treatment update

2021-06-18 04:44 PM

The first and foremost treatment in anaphylaxis is epinephrine. There are no absolute contraindications to epinephrine in the treatment of anaphylaxis.

Diagnosis is made clinically

The most common signs and symptoms are cutaneous (eg, sudden generalized urticaria, angioedema, flushing, pruritus). However, 10 to 20% of patients have no skin manifestations.

Danger signs: Rapidly progressive symptoms, respiratory distress (eg, shortness of breath, wheezing, dyspnoea, increased respiratory rate, persistent cough, cyanosis), vomiting, abdominal pain, hypotension, arrhythmia, chest pain, collapse.

Acute treatment

The first and foremost treatment in anaphylaxis is epinephrine. There are no absolute contraindications to epinephrine in the treatment of anaphylaxis.

Airway: Intubate immediately if there is evidence of impending airway obstruction due to angioedema. Delays can lead to complete blockages. Intubation can be difficult and should be performed by the most experienced clinician. Tracheostomy may be necessary.

Quickly and Simultaneously

Intramuscular epinephrine (1 mg/mL preparation): 0.3 to 0.5 mg intramuscularly epinephrine, preferably in the middle of the outer thigh. May repeat every 5 to 15 minutes (or more often), if needed. If epinephrine is given intramuscularly immediately, most patients respond to one, two, or at most three doses. If symptoms do not respond to intramuscular epinephrine, prepare epinephrine for intravenous infusion.

Place the patient in a supine position, if acceptable, and elevate the lower extremities.

Oxygen: deliver 8 to 10 L/min via mast or up to 100% oxygen, if needed.

Rapid infusion of normal saline solution: treat hypotension with rapid infusion of 1 to 2 litres of intravenous fluid. Repeat, if needed. Massive fluid changes with severe intravascular volume loss may occur.

Albuterol (salbutamol): for bronchospasm resistant to intramuscular epinephrine, give 2.5 to 5 mg in 3 mL saline through a nebulizer, or 2 to 3 puffs using a metered inhaler. Repeat, if needed.

Supportive therapies

H1* Antihistamines: consider giving cetirizine 10 mg IV (injected over 2 minutes) or diphenhydramine 25-50 mg IV (5 minutes given) - just to relieve urticaria and itching.

H2-antihistamines*: consider giving famotidine 20 mg IV (injected over 2 minutes).

Glucocorticoids*: consider methylprednisolone 125 mg IV.

Monitoring: continuous non-invasive hemodynamic monitoring and pulse oximetry monitoring is required. Urine output should be monitored in patients receiving IV fluid resuscitation for hypotension or severe shock.

Treatment of drug-resistant symptoms

Epinephrine infusion #: for patients who do not respond adequately to intramuscular epinephrine and intravenous saline, continuous epinephrine infusion, starting at 0.1 mcg/kg/min by infusion pump. Continuous dose titration according to blood pressure, heart rate and cardiac function, and oxygen intake.

Vasopressors #: some patients may require a second vasopressor (in addition to epinephrine). All vasopressors should be delivered by infusion pump, with doses titrated continuously according to blood pressure and heart rate/function, and oxygen monitored with a pulse oximeter.

Glucagon: Patients taking beta-blockers may not respond to epinephrine and may receive glucagon 1 to 5 mg IV over 5 minutes, followed by 5 to 15 mcg/min. Rapid administration of glucagon may cause vomiting.

* These drugs should not be used as the initial or sole treatment.

# All patients receiving epinephrine and another vasopressor infusion require continuous monitoring of blood pressure, heart rate and cardiac function, and oxygen saturation noninvasively.

For example, the initial infusion rate for a 70 kg patient would be 7 mcg/min. This is in line with the recommended range for non-weight-based dosing for adults, which is 2 to 10 mcg/min. Non-weight-based dosing may be used if the patient's weight is not known and cannot be estimated.