Anaphylaxis

Question 1

What type of hyerpsensitivity reaction is anaphylaxis?

Answer 1

type I

Question 2

What can cause nonimmune-mediated anaphylaxis?

Answer 2

heat, exhaustion, drugs/chemicals

Question 3

What are the 2 most important cells in the pathogenesis of anaphylaxis?

Answer 3

mast cells
basophils

Question 4

List 6 mediators released during anaphylaxis

Answer 4

• histamine
• Platelet activating factor
• eosinophil-chemotactic factor
• heparin
• prostaglandins
• tryptase

Question 5

What are the effects of platelet activating factor in anaphylaxis

Answer 5

platelet aggregation
increased vascular permeability
bronchoconstriction
vasodilation

Question 6

What are the effects of tryptase in anaphylaxis?

Answer 6

activates complement

Question 7

What is the name of the receptor on mast cells’ and basophils’ surface that IgE binds to?

Answer 7

Fc-epsilon-R1

Question 8

What are the different histamine receptors and what are each of their effects when activated?

Answer 8

H1 - vasodilation and extravasation
H2 - gastric acid secretion and modulation of cardiac myocytes
H3 and H4 - neurotransmitter release

Question 9

How soon after exposure do signs of anaphylaxis occur?

Answer 9

different resources but say 15 min to hours - CCM within 30 min and progression over next hours

Question 10

How is the hepatic/portal circulation affected in dogs with anaphylaxis?

Answer 10

hepatic arterial vasodilation and hepatic venous congestion - portal hypertension –> fluid transudation and decreased venous return to the heart

Question 11

What is “biphasic” anaphylaxis?

Answer 11

occurence of delayed signs (usually respiratory and cutaneous) - hours to days later

reported in 1-20% of human anaphylaxis patients

Question 12

How sensitive and specific are ALT elevations and gall bladder wall edema in dogs suspected to have anaphylaxis?

Answer 12

both almost 100% specific (98%), ALT 85% sensitive, Gall bladder edema 93% sensitive

Question 13

How is epinephrine suspected to help reduce further progression of CS in anaphylaxis?

Answer 13

reduces further histamine release by stabilizing mast cells

beta - 2 effects - bronchodilation
alpha -1 effects - vasoconstriction
beta - 1 effects - improving CO

Question 14

What is the main benefit of anti-histamine administration in anaphylaxis (e.g., diphenhydramine)

Answer 14

shown to reduce cutaneous signs - so really mostly indicated to help with that

Question 15

How long does the onset of action take after administering glucocorticoids and what is their main benefit in anaphylaxis?

Answer 15

minimum 30 min - likely hours

downreguate the late phase eosinophilic response, block arachidonic acid pathway, delayed inflammatory cascades

Question 16

describe the alternative IgG mediated pathway of anaphylaxis

Answer 16

IgG binds via Fc-gamma-RIII receptors

mediated mostly by PAF

Question 17

Explain how hepatocellular necrosis may happen in anaphylaxis

Answer 17

from sinusoidal and venous congestion - ischemia

Question 18

How much fluid can leave the IV space and move into the interstitial space during anaphylaxis?

Answer 18

35%

Question 19

How common are cutaneous signs in anaphylaxis in dogs and cats and how do these signs compare to milder allergic reactions?

Answer 19

different studies - Drobatz says 57%
in anaphylaxis cutaneous signs are actually milder than in mild allergic reactions that are primarily cutaneous

Question 20

What has been associated with death in dogs with severe anaphylaxis in Smith et al, 2020?

Answer 20

• hyperphosphatemia (>12)
• elevated PT
• concurrent PT and aPTT > 50% RI
• hypglycemia within 6 hours of presentation
• need for dextrose supplementation

serum phosphorous and PT times were significantly higher in nonsurvivors
temperature was significantly lower in nonsurvivors

Question 21

How common were coagulopathies, peritoneal effusion, and gall bladder halo signs in dogs with severe anphylaxis in Smith et al., 2020?

Answer 21

• 85%
• 65%
• 85%

(approximate values)

Question 22

How common were GI, respiratory, and cutaneous signs in dogs with severe anaphylaxis in Smith et al, 2020?

Answer 22

• 94%
• 67%
• 27%

Question 23

What was the overall mortality rate in dogs with severe sepsis in Smith et al, 2020?

Answer 23

15%

Question 24

What is the proposed mechanism for hypothermia in dogs with severe anaphylaxis Smith et al, 2020? (3)

Answer 24

• peripheral vasodilation
• decreased CO
• histamine affecting hypothalamic temperature regulation

Question 25

What is the proposed mechanism for hyperphosphatemia in severe anaphylaxis in Smith et al, 2020?

Answer 25

liver injury: P release from cell death, decreased uptake and utiliation of P by hepatic cells

Question 26

What is the proposed mechanism for hypoglycemia in severe anaphylaxis in Smith et al, 2020?

Answer 26

• decreased hepatic gluconeogenesis
• increased cellular utilization
• sepsis-induced - GI bacterial translocation

Question 27

What was the estimated incidence of anaphylaxis or mild hypersensitivity reactions in Fosset et al, 2023?

Answer 27

• 0.04%
• 0.15%

Question 28

What was the most common cause for hypersensitivity reactions and anaphylaxis in Fosset et al, 2023?

Answer 28

• most common known trigger: vaccines
• in hypersensitivity reactions: unknown trigger more common than known vaccine trigger

Question 29

How did hemostatic derangements compare between severe versus mild and moderate cases of anaphylaxis in Smith et al, 2022?

Answer 29

VCM:
* longer CT and CFT
* decreased alpha angle, MCF

prolonged PT and aPTT
lower platelet counts

Question 30

What was the association between anaphylaxis induced spontaneous hemoperitoneum and coagulopathies in Summers et al, 2021

Answer 30

did not seem to be the contributing factor, however, only 5/16 dogs had clotting times evaluated
* only 1 patient prolonged PT and another one prolonged aPTT
* all platelet counts were normal