From the Guidelines
In suspected anaphylactic shock, stat laboratory investigations should include serum tryptase levels, complete blood count, basic metabolic panel, arterial blood gases, and coagulation studies to confirm the diagnosis and guide management. According to the most recent guidelines 1, immediate treatment with epinephrine (0.2 to 0.5 mg intramuscularly) is crucial, and laboratory tests should not delay this intervention. Serum tryptase levels should be drawn within 1-3 hours of symptom onset (ideally at 1 hour) and again at 24 hours for comparison, as elevated levels indicate mast cell degranulation 1.
Key Laboratory Investigations
- Serum tryptase levels: to confirm mast cell degranulation
- Complete blood count: to reveal hemoconcentration or eosinophilia
- Basic metabolic panel: to assess organ perfusion and acid-base status
- Arterial blood gases: to evaluate oxygenation and acid-base disturbances
- Coagulation studies (PT/PTT): if disseminated intravascular coagulation is suspected
- Blood cultures: to rule out sepsis as a differential diagnosis These tests complement the clinical assessment and help identify potential triggers, guiding follow-up care while prioritizing immediate treatment with epinephrine, IV fluids, oxygen, and other supportive measures 1.
From the Research
Initial Assessment and Management
In a case of suspected anaphylactic shock, the following labs and investigations should be ordered stat:
- Complete Blood Count (CBC) to assess for any underlying infections or inflammatory conditions 2
- Electrolyte panel to evaluate for any electrolyte imbalances 2
- Renal function tests to assess kidney function 2
- Liver function tests to evaluate liver function 2
- Coagulation studies to assess for any coagulopathy 2
- Arterial Blood Gas (ABG) to evaluate oxygenation and ventilation 2
- Electrocardiogram (ECG) to assess for any cardiac complications 2
- Chest X-ray to evaluate for any pulmonary complications 2
Specific Investigations for Anaphylaxis
- Trypsase levels to confirm anaphylaxis 3
- Histamine levels to confirm anaphylaxis 3
- Allergy testing to identify potential allergens 3
Monitoring and Supportive Care
- Continuous cardiac monitoring to assess for any cardiac complications 2
- Pulse oximetry to monitor oxygen saturation 2
- Blood pressure monitoring to assess for any hypotension 2
- Respiratory support as needed, including oxygen therapy and mechanical ventilation 2
- Fluid resuscitation to maintain adequate blood pressure and perfusion 2
Medications and Treatments
- Epinephrine administration as first-line treatment for anaphylaxis 2, 4, 3, 5, 6
- Antihistamines, such as diphenhydramine, to relieve symptoms 4, 5, 6
- Corticosteroids, such as methylprednisolone, to reduce inflammation 4, 5, 6
- Bronchodilators, such as albuterol, to relieve bronchospasm 3
- Vasopressors, such as norepinephrine, to support blood pressure 3
Note: The use of corticosteroids in anaphylaxis is still a topic of debate, and their effectiveness in reducing the risk of biphasic reactions is unclear 4, 5, 6.