Anaphylaxis Flashcards
What type of hyerpsensitivity reaction is anaphylaxis?
type I
What can cause nonimmune-mediated anaphylaxis?
heat, exhaustion, drugs/chemicals
What are the 2 most important cells in the pathogenesis of anaphylaxis?
mast cells
basophils
List 6 mediators released during anaphylaxis
- histamine
- Platelet activating factor
- eosinophil-chemotactic factor
- heparin
- prostaglandins
- tryptase
What are the effects of platelet activating factor in anaphylaxis
platelet aggregation
increased vascular permeability
bronchoconstriction
vasodilation
What are the effects of tryptase in anaphylaxis?
activates complement
What is the name of the receptor on mast cells’ and basophils’ surface that IgE binds to?
Fc-epsilon-R1
What are the different histamine receptors and what are each of their effects when activated?
H1 - vasodilation and extravasation
H2 - gastric acid secretion and modulation of cardiac myocytes
H3 and H4 - neurotransmitter release
How soon after exposure do signs of anaphylaxis occur?
different resources but say 15 min to hours - CCM within 30 min and progression over next hours
How is the hepatic/portal circulation affected in dogs with anaphylaxis?
hepatic arterial vasodilation and hepatic venous congestion - portal hypertension –> fluid transudation and decreased venous return to the heart
What is “biphasic” anaphylaxis?
occurence of delayed signs (usually respiratory and cutaneous) - hours to days later
reported in 1-20% of human anaphylaxis patients
How sensitive and specific are ALT elevations and gall bladder wall edema in dogs suspected to have anaphylaxis?
both almost 100% specific (98%), ALT 85% sensitive, Gall bladder edema 93% sensitive
How is epinephrine suspected to help reduce further progression of CS in anaphylaxis?
reduces further histamine release by stabilizing mast cells
beta - 2 effects - bronchodilation
alpha -1 effects - vasoconstriction
beta - 1 effects - improving CO
What is the main benefit of anti-histamine administration in anaphylaxis (e.g., diphenhydramine)
shown to reduce cutaneous signs - so really mostly indicated to help with that
How long does the onset of action take after administering glucocorticoids and what is their main benefit in anaphylaxis?
minimum 30 min - likely hours
downreguate the late phase eosinophilic response, block arachidonic acid pathway, delayed inflammatory cascades
describe the alternative IgG mediated pathway of anaphylaxis
IgG binds via Fc-gamma-RIII receptors
mediated mostly by PAF
Explain how hepatocellular necrosis may happen in anaphylaxis
from sinusoidal and venous congestion - ischemia
How much fluid can leave the IV space and move into the interstitial space during anaphylaxis?
35%
How common are cutaneous signs in anaphylaxis in dogs and cats and how do these signs compare to milder allergic reactions?
different studies - Drobatz says 57%
in anaphylaxis cutaneous signs are actually milder than in mild allergic reactions that are primarily cutaneous
What has been associated with death in dogs with severe anaphylaxis in Smith et al, 2020?
- 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
How common were coagulopathies, peritoneal effusion, and gall bladder halo signs in dogs with severe anphylaxis in Smith et al., 2020?
- 85%
- 65%
- 85%
(approximate values)
How common were GI, respiratory, and cutaneous signs in dogs with severe anaphylaxis in Smith et al, 2020?
- 94%
- 67%
- 27%
What was the overall mortality rate in dogs with severe sepsis in Smith et al, 2020?
15%
What is the proposed mechanism for hypothermia in dogs with severe anaphylaxis Smith et al, 2020? (3)
- peripheral vasodilation
- decreased CO
- histamine affecting hypothalamic temperature regulation
What is the proposed mechanism for hyperphosphatemia in severe anaphylaxis in Smith et al, 2020?
liver injury: P release from cell death, decreased uptake and utiliation of P by hepatic cells
What is the proposed mechanism for hypoglycemia in severe anaphylaxis in Smith et al, 2020?
- decreased hepatic gluconeogenesis
- increased cellular utilization
- sepsis-induced - GI bacterial translocation
What was the estimated incidence of anaphylaxis or mild hypersensitivity reactions in Fosset et al, 2023?
- 0.04%
- 0.15%
What was the most common cause for hypersensitivity reactions and anaphylaxis in Fosset et al, 2023?
- most common known trigger: vaccines
- in hypersensitivity reactions: unknown trigger more common than known vaccine trigger
How did hemostatic derangements compare between severe versus mild and moderate cases of anaphylaxis in Smith et al, 2022?
VCM:
* longer CT and CFT
* decreased alpha angle, MCF
prolonged PT and aPTT
lower platelet counts
What was the association between anaphylaxis induced spontaneous hemoperitoneum and coagulopathies in Summers et al, 2021
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
