Perioperative anaphylaxis

Anaphylaxis is defined as a 'severe life-threatening generalized or systemic hypersensitivity reaction'. Anaphylactic shock is characterized by generalized vasodilation and increased capillary permeability, leading to reduction in cardiac output. The pathophysiology of anaphylaxis can be described as immunologic and non-immunologic. The National Audit Project 6 (NAP 6) has recently investigated perioperative anaphylaxis and this article will outline some key updates from their report. Common triggers include antibiotics, followed by neuromuscular blocking agents, chlorhexidine and patent blue dye. Invasive lines impregnated with chlorhexidine are frequently missed as a cause of anaphylaxis. Patients at high risk of adverse outcomes include the elderly and those with pre-existing cardiopulmonary disease. The diagnosis is clinical and can be confounded by physiological changes commonly experienced after induction or airway manipulation. Key management principles include early administration of intravenous adrenaline, CPR if the systolic blood pressure is <50 mmHg and fluid resuscitation. Follow-up investigations are essential to guide future patient care and this is the responsibility of the anaesthetist.