What medications should be ordered for a patient with metabolic acidosis unresponsive to epinephrine (adrenaline)?

Management of Metabolic Acidosis When Epinephrine Is Ineffective

In patients with metabolic acidosis unresponsive to epinephrine, sodium bicarbonate should be administered as the first-line medication, followed by calcium, insulin with glucose, and vasopressors if needed. 1

First-Line Treatment: Sodium Bicarbonate

For patients with metabolic acidosis unresponsive to epinephrine:

1. Sodium bicarbonate: 1-2 mEq/kg IV given slowly 1
   • Indicated specifically for documented metabolic acidosis after effective ventilation has been established
   • Particularly important when pH < 7.2 1, 2
   • For sodium channel blocker overdose (e.g., tricyclic antidepressants), titrate to maintain serum pH of 7.45-7.55

Important: Ensure effective ventilation before administering bicarbonate, as this allows elimination of excess CO2 produced by bicarbonate 1

Second-Line Treatments

If inadequate response to sodium bicarbonate:

1. Calcium chloride: 20 mg/kg (0.2 mL/kg for 10% CaCl2) IV 1

   • Particularly indicated for hyperkalemia with acidosis
   • Also useful for calcium channel blocker toxicity
   • Calcium gluconate (60 mg/kg) may be substituted if calcium chloride is unavailable

2. Insulin with glucose:

   • Insulin: 10 units IV with 50 mL dextrose 1
   • Particularly effective for hyperkalemia with acidosis
   • Monitor blood glucose closely to prevent hypoglycemia

Third-Line Treatments

If still inadequate response:

1. Vasopressors/inotropes:

   • Norepinephrine (0.05-0.5 μg/kg/min) 1
   • Vasopressin (1-2 IU bolus with or without infusion at 2 units/hour) 1
   • For patients on beta-blockers, consider glucagon (1-2 mg IV) 1

2. Hemodialysis: Consider for severe, refractory metabolic acidosis, especially in patients with renal failure 1

Special Considerations

For Specific Causes of Metabolic Acidosis:

• Tricyclic antidepressant overdose: Sodium bicarbonate is particularly important 1
• Hyperkalemia with acidosis: Prioritize calcium, insulin/glucose, and bicarbonate 1
• Lactic acidosis: Focus on improving tissue perfusion and treating underlying cause 2
• Diabetic ketoacidosis: Insulin therapy with fluid resuscitation 2
• Chronic kidney disease: Target serum bicarbonate ≥ 22 mmol/L 2

Cautions:

• Sodium bicarbonate can cause sodium and fluid overload, increase in lactate and PCO2, and decrease in serum ionized calcium 2
• Rapid administration of sodium bicarbonate can lead to paradoxical intracellular acidosis and hypocalcemia 2
• In patients with mixed acidosis with high PaCO2 or hypernatremia, THAM may be preferred over bicarbonate 2

Monitoring During Treatment

• Arterial blood gases every 15-30 minutes during acute treatment
• Serum electrolytes (especially potassium, sodium, chloride)
• Continuous cardiac monitoring
• Urine output
• End-tidal CO2 if intubated

Algorithm for Metabolic Acidosis Management

1. Ensure effective oxygenation and ventilation
2. Administer sodium bicarbonate 1-2 mEq/kg IV if pH < 7.2
3. If hyperkalemia present or inadequate response, add calcium chloride 20 mg/kg IV
4. Add insulin 10 units with glucose 50 mL IV
5. If still inadequate response, start vasopressors (norepinephrine or vasopressin)
6. Consider hemodialysis for refractory cases

The primary goal should always be to identify and treat the underlying cause of metabolic acidosis while supporting vital functions and correcting severe acid-base disturbances that may impair cardiac function and tissue perfusion.