Cardiovascular aspects of anaphylaxis: implications for treatment and diagnosis.
OBJECTIVE
Anaphylactic cardiovascular collapse can be resistant to treatment with epinephrine (adrenaline) and, in some cases, diagnostic uncertainty compromises follow-up care. The purpose of this review is to examine recent studies relevant to the management and diagnosis of this condition.


RESULTS
Nausea, vomiting, incontinence, diaphoresis, dyspnoea, hypoxia, dizziness and collapse are associated with hypotension. Relative bradycardia (falling heart rate despite hypotension) is a consistent feature of hypotensive insect sting anaphylaxis and may represent a non-specific physiological response to severe hypovolaemia in conscious individuals. Upright posture has been found to be associated with death from anaphylaxis. Animal studies have found the intramuscular route for epinephrine is ineffective, intravenous boluses temporarily effective, but intravenous infusions of epinephrine are able to reverse anaphylactic shock. In one animal model, antihistamines were found to be harmful. A prospective human study provides evidence for the efficacy of treatment with intravenous epinephrine infusion and fluid (volume) resuscitation. Case reports support the use of the vasoconstrictors metaraminol, methoxamine and vasopressin if adrenaline is ineffective. Repeated measurements of mast cell tryptase are more sensitive and specific than a single measurement for the diagnosis of anaphylaxis.


CONCLUSIONS
Current evidence supports use of the supine/Trendelenburg position, epinephrine by intravenous infusion and aggressive volume resuscitation. If these fail, atropine should be considered for severe bradycardia and potent vasoconstrictors may be useful. To confirm the diagnosis of anaphylaxis, serial measurements of mast cell tryptase may be preferable to a single measurement.
Discipline of Emergency Medicine, The University of Western Australia at Fremantle Hospital, Fremantle, Western Australia, Australia. simon.brown@uwa.edu.au
Simon G A
SG
Brown
D000293:Adolescent; D000328:Adult; D000707:Anaphylaxis / Q000188:drug therapy* / Q000276:immunology* / Q000401:mortality / Q000503:physiopathology; D000818:Animals; D002318:Cardiovascular Diseases / Q000188:drug therapy* / Q000276:immunology* / Q000401:mortality; D002648:Child; D002675:Child, Preschool; D003131:Combined Modality Therapy; D003422:Critical Care; D004342:Drug Hypersensitivity / Q000276:immunology; D004359:Drug Therapy, Combination; D004837:Epinephrine / Q000008:administration & dosage*; D005440:Fluid Therapy / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D007262:Infusions, Intravenous; D007299:Insect Bites and Stings / Q000276:immunology; D008875:Middle Aged; D018570:Risk Assessment; D012720:Severity of Illness Index; D015996:Survival Rate; D016896:Treatment Outcome; D014662:Vasoconstrictor Agents / Q000008:administration & dosage*
D014662:Vasoconstrictor Agents; D004837:Epinephrine