Type I IgE-mediated hypersensitivity reaction. Release of histamine and other agents causes: capillary leak; wheeze; cyanosis; oedema (larynx, lids, tongue, lips); urticaria. More common in atopic individuals.

Assessment

• ABCDE : with shock we are dealing primarily with C
• 2 large-bore IV access
• ECG: for rate, rhythm (very fast or very slow will compromise cardiac output), and signs of ischemia.
• General review: any features suggestive of anaphylaxis—history, urticaria, angioedema, wheeze?

If BP unrecordable, call the cardiac arrest team.

Immediate Management

• Secure the airway
  • 100% O2
  • Intubate if respiratory obstruction imminent
• Remove the cause
• Raising the feet may help restore the circulation
• Give adrenaline IM 0.5mg
  • Repeat every 5min, if needed
  • Guided by BP, pulse, and respiratory function, until better
• Secure IV access
• Chlorphenamine 10mg IV
• Hydrocortisone 200mg IV
• IVI (0.9% saline, 500mL over ¼h; up to 2L may be needed)
  • Adjust the amount of fluid based on the blood pressure.
• If wheeze, treat for asthma
  • May require ventilatory support
• If still hypotensive
  • admission to ICU
  • an IVI of adrenaline may be needed ± aminophylline
  • nebulized salbutamol

Further management

• Admit to ward.
• Monitor ECG.
• Measure serum tryptase 1–6h after suspected anaphylaxis.
• Continue chlorphenamine 4mg/6h oral, if itching.
• Suggest wearing an identification bracelet that lists the specific allergen.
• Teach about self-injected adrenaline (0.3mg) to prevent a fatal attack.
• Skin-prick tests showing specific IgE help identify allergens to avoid.