Anaphylaxis/Anaphylactoid Reactions

Question 1

What are anaphylactic and anaphylactoid reactions?

Answer 1

Anaphylaxis is a type I immediate hypersensitivity reaction involving IgE antibody-antigen interaction (and usually requires previous exposure); anaphlyactoid reactions are direct non-immune-mediated release of vasoactive mediators from mast cells and basophils. The two are clinically indistinguishable.

Question 2

What are the various grades of a anaphylactic or anaphylactoid reaction?

Answer 2

Grade I: mucocutaneous signs only (erythema, urticaria +/- angioedema)
Grade II: moderate multivisceral signs :
grade I signs PLUS HoTN +/- tachycardia +/- dyspnea +/- Gi disturbances (vomiting/diarrhea/crampy abdominal pain)
Grade III: life-threatening mono or multivisceral signs: grade I signs PLUS CV collapse, cardiac dysrhythmias, bronchospasm, GI disturbances
Grade IV: cardiac arrest

Question 3

What is the differential diagnosis for the skin manifestations of an allergic reaction?

Answer 3

nonanaphylaxis related rash, angioedema related ACE inhibitors, trauma, C1-esterase deficiency

Question 4

What is the differential diagnosis for the pulmonary manifestations of anaphylaxis/anaphylactoid reactions?

Answer 4

bronchospasm
pulmonary edema
PTX
PE
aspiration
increased airway pressure from another cause

Question 5

What is the differential diagnosis for the cardiovascular manifestations of anaphylaxis/anaphylactoid reactions?

Answer 5

tamponade
VAE, fat embolism
shock (septic, cardiogenic, spinal)
transfusion reaction
other causes of hypotension

Question 6

How should you manage an anaphylactic/anaphylactoid reaction?

Answer 6

1. Call for help
2. withdraw suspected culprit drug (if occurs on induction, stop all anesthetic drugs)
3. check with surgeons to see if they have introduced any possible antigenic material
4. maintain airway, place 100% FiO2
5. early tracheal intubation should be considered (edema may be imminent)
6. trendelenburg to maximize venous return
7. abbreviate surgery ASAP
8. epinephrine
9. rapidly expand fluid volume (5 - 10cc/kg in first 5 minutes. 2 - 4 L is average but 7L is not uncommon)
10. H1 blocker
11. hydrocortisone (fastest corticosteroid)
12. H2 blockers not indicated
13. consider vasopressin for refractory HoTN
14. glucagon therapy
15. draw blood for serum tryptase

Question 7

How should you dose epinephrine in an anaphylactic/anaphylactoid reaction?

Answer 7

• 10 to 20 mcg IV PRN for hypotension, escalate as needed
• 0.5 - 1mg for cardiovascular collapse
• infusion of 1 - 10mcg/min may be required

Question 8

How much fluid should be administered in an anaphylactic/anaphylactoid reaction?

Answer 8

5 - 10cc/kg of crystalloid in the first 5 minutes

2 - 4 L in initial resuscitation is average (but 7L is not uncommon)

Question 9

How is glucagon therapy helpful in an anaphylactic/anaphylactoid reaction?

Answer 9

increased inotropy/chronotropy independent of alpha or beta adrenergic mechanism. 1000mg IV for adults, 500mg IV children, particularly effective if on beta-blockers.