4. Anaphylactic Shock

Question 1

Anaphylaxis is an..

Answer 1

allergic reaction that is rapid in onset and may cause death.

It usually occurs after previous exposure to the substance.

Hives, angioedema in ~88% of the cases

Respiratory Tract Involvement in ~ 50% of cases

Shock occurs in ~ 30% of anaphylaxis cases.

Question 2

Etiology of Anaphylactic Shock:

Answer 2

-IgE-Mediated immediate hypersensitivity reaction to PROTEIN substances.
-Penicillin, contrast media, bee sting, foods, latex

Question 3

An anaphylactoid response

Answer 3

looks the same clinically but is NOT IgE-mediated. Previous exposure is not necessary (figure 5-5)

Question 4

Pathophysiology of anaphylactic shock

Answer 4

Antigen-Antibody Reaction
—->Histamine Released
—–>Increased Capillary Permeability
—–>Massive dilation
——> decreased CO
——> Bronchospasm, laryngeal edema, urticaria

(increased cap permeability, massive dilation, decreased co all lead to hypotension)

Question 5

Treatment:

Answer 5

-Removal of offensive agent, if able

-O2

-0.3 - 0.5 mg of 1: 1,000 epinephrine IM (IM has more rapid absorption than subcutaneous) to decrease dilation, bronchospasm.

-Aggressive fluid resuscitation (1 - 4 L) to treat the relative hypovolemia

-Antihistamine: diphenhydramine (Benadryl) 25-50 mg IV to decrease allergic response

-Inhaled beta-adrenergic agents to decrease bronchospasm

-Steroids IV (high-dose): peaks in 4-6 hrs, give ASAP to get “on board” to decrease inflammatory response.