Management of anaphylactic shock in the operating room

Diagnosis of anaphylactic shock occurring during anesthesia is challenging because of altered clinical signs and confounding diagnoses (e.g. arterial hypotension). A major sign of clinical severity in the presence of arterial hypotension is a low end-tidal CO2 concentration (below 20mmHg). Acute hemoconcentration (increase of hemoglobin concentrations) is highly suggestive of vascular leak triggered by anaphylactic shock. Guidelines for management of anaphylactic shock occurring during anesthesia are based on withdrawal of the suspected allergen, airway control, increased cardiac preload by the Trendelenbourg position and volume expansion, epinephrine, glucocorticoids and monitoring for 24hours, although evidence for the efficacy of these therapeutic interventions is absent or very weak. Refractory anaphylactic shock although not defined could be characterized by persistent clinical signs after more than 10minutes of adequately managed resuscitation. It should trigger enhanced cardiac monitoring through echocardiography to detect primary myocardial dysfunction and alert for extracorporeal life support. Drugs that may be used for refractory anaphylactic shock in addition to epinephrine are glucagon, norepinephrine, vasopressin, methylene blue but there are only animal studies where these drugs were compared to epinephrine. Follow-up after resuscitation includes patient information on the drugs given before occurrence of clinical signs, scheduled allergology investigation, pharmacovigilance report and recovery of the conclusions of allergology investigation with clear decisions on the identification of the culprit agent and subsequent avoidance. All these conclusions have to be traced in the medical record and shared with the patient.