What is the management approach for a patient with anaphylactic shock and acute kidney injury (Impaired renal function)?

Management of Anaphylactic Shock with Acute Kidney Injury

Immediate intramuscular epinephrine (0.3-0.5 mg of 1:1000 solution) into the anterolateral thigh remains the first-line treatment for anaphylactic shock regardless of the presence of acute kidney injury, followed by aggressive fluid resuscitation with crystalloids and transition to intravenous epinephrine infusion (5-15 μg/min) if hypotension persists despite repeated IM doses. 1

Immediate Resuscitation (First 5 Minutes)

Epinephrine Administration

• Administer intramuscular epinephrine 0.3-0.5 mg (0.5 mL of 1:1000 solution) into the anterolateral thigh immediately as the cornerstone of treatment, with no absolute contraindications even in the presence of renal impairment 1, 2
• Repeat IM epinephrine every 5-15 minutes as needed if hypotension or bronchospasm persists 1
• The presence of acute kidney injury does not alter epinephrine dosing or administration route 3

Airway and Breathing

• Administer 100% oxygen immediately and assess for rapidly progressive laryngeal edema 1, 2, 4
• Prepare for emergency intubation if stridor develops, as waiting may make intubation impossible and necessitate cricothyroidotomy 1, 4
• Treat persistent bronchospasm with IV salbutamol infusion, or consider IV aminophylline or magnesium sulfate 1, 4

Circulation and Fluid Resuscitation

• Establish large-bore IV access immediately and administer rapid boluses of normal saline 0.9% or lactated Ringer's solution (500-1000 mL boluses in adults, 20 mL/kg in children) 1, 2
• Large volumes of crystalloid may be required due to profound vasodilation and capillary leak, even in patients with AKI 1, 5
• The 2020 AHA guidelines prioritize fluid resuscitation alongside epinephrine as standard resuscitative measures 1

Transition to IV Epinephrine (If Refractory to IM Doses)

Indications for IV Epinephrine

• Transition to IV epinephrine when hypotension persists despite 2-3 IM doses and aggressive fluid resuscitation 1, 6
• IV epinephrine is reasonable when IV access is already established in anaphylactic shock 1

IV Epinephrine Dosing

• For IV bolus: administer 0.05-0.1 mg (50-100 μg) of 1:10,000 solution slowly, titrating to response 1, 6
• For continuous infusion: start at 5-15 μg/min (0.05-0.1 μg/kg/min in children) and titrate to blood pressure response 1, 6
• Prepare infusion by adding 1 mg epinephrine to 100 mL saline (1:100,000 solution) 6
• Continuous infusion allows careful titration and avoids epinephrine overdosing, which is critical given epinephrine's short half-life 1, 6

Monitoring During IV Epinephrine

• Continuous hemodynamic monitoring is mandatory, with blood pressure measured every 5-15 minutes 6
• Monitor for arrhythmias, as IV epinephrine carries risk of potentially lethal ventricular arrhythmias, particularly in patients with underlying heart disease 1, 3
• Frequently check the IV infusion site for extravasation, as this can cause substantial skin necrosis 6

Renal-Specific Considerations in AKI

Epinephrine Safety in AKI

• Epinephrine dosing does not require adjustment for renal impairment, as it is metabolized primarily by catechol-O-methyltransferase and monoamine oxidase, not renally excreted 3
• The presence of AKI should not delay or alter epinephrine administration, as untreated anaphylactic shock will worsen renal perfusion and exacerbate kidney injury 7, 8

Fluid Management in AKI

• Despite concerns about fluid overload in AKI, aggressive crystalloid resuscitation remains essential to restore intravascular volume and renal perfusion pressure 1, 2
• Anaphylaxis causes profound distributive shock with third-spacing, requiring large fluid volumes even in oliguric AKI 5, 7
• Restoration of blood pressure with vasopressors and fluids improves renal perfusion and may prevent further AKI progression 8

Alternative Vasopressors for Refractory Shock

• If blood pressure does not recover despite epinephrine infusion and fluid resuscitation, consider adding norepinephrine as the preferred second-line vasopressor 1, 6, 8
• Norepinephrine is safer than epinephrine in prolonged shock states, with less lactic acidosis and hyperglycemia 8
• Avoid dopamine as first-line vasopressor in AKI, as it offers no renal protective benefit and is associated with increased arrhythmias and mortality 1, 8
• Consider metaraminol as an alternative if norepinephrine is unavailable 1, 6

Adjunctive Medications (After Epinephrine)

Antihistamines and Corticosteroids

• Administer H1-antihistamine (diphenhydramine 25-50 mg IV or chlorphenamine 10 mg IV) only after adequate epinephrine and fluid resuscitation 1, 2
• Add H2-antihistamine (ranitidine 50 mg IV or famotidine 20 mg IV) as adjunctive therapy 2
• Give hydrocortisone 200 mg IV or methylprednisolone 1-2 mg/kg IV to potentially prevent biphasic reactions, though evidence is limited 1, 2
• These medications have no role in acute management and should never delay epinephrine administration 2, 4, 5

Special Considerations for Beta-Blocker Patients

• For patients on beta-blockers with refractory hypotension despite epinephrine, administer glucagon 1-5 mg IV over 5 minutes 6, 2
• Beta-blockade may blunt epinephrine's cardiovascular effects, necessitating higher doses or alternative agents 6

Monitoring and Disposition

Laboratory Monitoring

• Obtain serial mast cell tryptase levels: immediately after resuscitation starts, at 1-2 hours, and at 24 hours or follow-up to confirm anaphylaxis diagnosis 1, 2
• Monitor renal function (creatinine, BUN), electrolytes, and urine output closely, as anaphylactic shock can cause or worsen AKI through hypoperfusion and rhabdomyolysis 7
• Check creatine kinase if rhabdomyolysis is suspected from prolonged hypotension 7

Observation Period

• Observe patients in a monitored setting for minimum 6 hours after symptom resolution, extending to 24 hours for severe reactions requiring multiple epinephrine doses 2, 4, 9
• Patients with AKI require ICU admission for close hemodynamic monitoring and potential renal replacement therapy 1, 2
• Biphasic reactions occur in 1-20% of cases and are difficult to predict, but mandatory observation periods beyond clinical stability are not evidence-based 9

Discharge Planning

• Prescribe epinephrine auto-injector (EpiPen 0.3 mg for adults, 0.15 mg for children) with detailed administration instructions 2, 4
• Arrange urgent allergy/immunology follow-up for trigger identification and long-term management 1, 2
• Provide medical alert identification and anaphylaxis action plan 2

Critical Pitfalls to Avoid

• Never delay epinephrine for antihistamines or corticosteroids, as epinephrine is the only medication proven to prevent death from anaphylaxis 2, 4, 5
• Do not inject epinephrine into the buttock, as this may cause inadequate absorption and has been associated with Clostridial infections 3
• Avoid repeated injections at the same site due to risk of tissue necrosis from vasoconstriction 3
• Do not withhold fluids in AKI, as restoration of intravascular volume and renal perfusion pressure is essential to prevent further kidney injury 1, 7, 8
• Never confuse 1:1000 and 1:10,000 epinephrine concentrations, as this is a common and potentially fatal dosing error 6
• Do not use IV epinephrine as first-line therapy unless the patient is in cardiac arrest or has failed multiple IM doses with IV access already established 1, 6