Anaphylaxis and sudden collapse Flashcards
List systems within which abnormalities can result in diffuse brain dysfunction
CNS
CVS
Metabolic
Endocrine
Toxic
Environmental disorders e.g. hypothermia, heat stroke
Hysterical
Outline 3 principle causes of coma
1) widespread damage in both hemispheres e.g. trauma
2) suppression of cerebral function e.g. drugs or hypoglycaemia
3) brainstem lesions that damage RAS
What are risk factors for anaphylaxis fatalities?
Failure to administer required adrenaline immediately
Rapid IV allergen
Pre existing (beta blockers, asthma, cardiac disease)
Requirements to diagnose of arrhythmia related syncope
ECG:
- sinus bradycardia
- 3rd degree AV heart block
- tachycardias e.g. VT
- pacemaker or ICD malfunction
Outline orthostatic syncope
Documentation of orthostatic hypotension ( <90mmHg / >20mmHg drop in systolic BP) associated with syncope or pre-syncope
Cardiac ischaemia-related syncope
Diagnosed when symptoms are present with ECG or other evidence of acute ischaemia,
with or without myocardial infarction
Identify possible causes of loss of consciousness
TIPS AEIOU
Trauma
Infection
Psychogenic
Seizure, syncope, space occupying lesion
Alcohol and other toxins
Endocrinopathy, encephalopathy, electrolyte disturbances
Insulin - diabetes
Oxygen - hypoxia of any cause
Uraemia
Outline situational syncope
Transient vagal tone:
Diagnosed if syncope occurs during or after specific event
Anaphylactic
vs
Anaphylactoid
-tic = related to IgE
-toid = not related to IgE
What happens with the IgE molecules upon subsequent exposure to the allergen?
Cross linking of the IgE antibodies and antigen causing rapid mast cell activation
Adrenaline dosage
1:1000 adrenaline is 1mg in 1ml
0.3-0.5mg IM
Repeat every 5-10 minutes
First line treatment for anaphylaxis
IM adrenaline
What are the clinical effects of subsequent allergen exposure?
urticaria, angioedema, bronchospasm, anaphylaxis
What are the 3 types of anaphylaxis?
Monophasic (peak within 30-60 minutes)
Biphasic (symptoms recur 1-72 hrs after initial episode)
Protracted (lasts days/weeks)
Outline reflex syncope
Vasovagal syncope
- precipitated by emotional distress or prolonged standing
- associated with prodromal symptoms due to autonomic activation
Define syncope
a brief loss of consciousness (fainting) and postural tone (collapse) with rapid spontaneous recovery
Treatment for cutaneous symptoms of anaphylaxis
Antihistamines
h1 receptor blocker
+
h2 receptor blocker
Risk factors for biphasic and protracted anaphylactic reactions?
Severe initial reaction
>1 dose of adrenaline required
Wide pulse pressure
Unknown trigger
Cutaneous signs and symptoms
Delayed time to adrenaline (>90min)
Drug trigger in paediatric patients
What investigations to conduct with coma presentation
ABGs/VBGs
ECG
Blood cultures
Drug screen
Alcohol level
FBC
Biochemistry
Lumbar puncture
CXR
CT head if aetiology not obvious or if focal signs present (essential if trauma present)
TFTs
Outline the 2 focal lesions of the CNS causing coma
1) supratentorial e.g. haemorrhage, infarction, tumour or abscess
2) subtentorial e.g. compressive or destructive
Does the binding of IgE with mast cells always produce a response?
No, not in the absence of further contact with the allergen
2 main criteria to diagnosis of anaphylaxis
1) ACUTE onset of an illness with simultaneous involvement of the SKIN/MUCOSA and at least on of (respiratory, hypotension, GIT)
2) Acute onset of HYPOTENSION or BRONCHOSPASM or LARYNGEAL involvement AFTER EXPOSURE to a known or highly probable allergen for that patient (mins-hrs), even in the ABSENCE OF TYPICAL SKIN INVOLVEMENT
Hx questions: patient presenting with syncope
- eye witness
- mode of onset and progression
- body position
- depth of altered consciousness
- duration
- rate of recovery
- identify precipitants
- associated symptoms
- history of panic attack and hyperventilation
- drug history
- past medical Hx and risk factors for IHD
Main effect of beta 1 & 2 adrenergic stimulation
1: +ve ionotrope (contractility) and chronotrope (HR)
2: bronchodilator
Both: increases cAMP - inhibits further mast cell and basophil mediator release
Treatment regime for anaphylaxis
Monitoring post adrenaline injection
Stable patient needs ~ 6-8 hrs as up to 5% of biphasic anaphylaxis
Continue meds for 3 days - antihistamines
Reassess precipitants - allergy testing and specialist follow up
Immunotherapy
Fluid administration for anaphylaxis
Crystalloid, 10-20ml/kg bolus
Main effect of alpha adrenergic stimulation
Vasoconstriction: decreases angioedema
- Increase TPR
- Improve BP
- Improves coronary artery perfusion
- Reverses peripheral dilatation
