What is the dose and indications for starting a sodium bicarbonate (NaHCO3) drip in a patient with acute metabolic acidosis?

From the Guidelines

Sodium bicarbonate (NaHCO3) drips should be initiated for severe metabolic acidosis when pH is less than 7.1-7.2 or serum bicarbonate is below 12-15 mEq/L, particularly when acidosis is causing hemodynamic instability or is refractory to other treatments. The standard dosing approach is to calculate the bicarbonate deficit using the formula: Bicarbonate deficit (mEq) = 0.5 × weight (kg) × [24 - measured serum bicarbonate (mEq/L)], as suggested by general medical knowledge. Initially, administer half of this calculated deficit over 4-8 hours, then reassess. For continuous infusion, a typical concentration is 150 mEq of sodium bicarbonate in 1L of D5W, infused at 1-1.5 mEq/kg/hour, as indicated in the study 1. The drip should be adjusted based on serial arterial blood gas measurements and electrolyte levels, typically targeting a pH above 7.2 or bicarbonate level above 12-15 mEq/L. Careful monitoring is essential as bicarbonate therapy can cause complications including hypernatremia, hyperosmolality, volume overload, paradoxical CSF acidosis, and hypokalemia. Bicarbonate therapy addresses acidosis by providing bicarbonate ions that buffer excess hydrogen ions, raising blood pH. However, it should be used judiciously as it treats the symptom rather than the underlying cause of acidosis, which must be addressed concurrently. It's also important to note that routine use of sodium bicarbonate is not recommended for patients in cardiac arrest, as stated in the study 1, but it may be beneficial in special situations such as preexisting metabolic acidosis, hyperkalemia, or tricyclic antidepressant overdose. In such cases, an initial dose of 1 mEq/kg is typical, and therapy should be guided by the bicarbonate concentration or calculated base deficit obtained from blood gas analysis or laboratory measurement. To minimize the risk of iatrogenically induced alkalosis, providers should not attempt complete correction of the calculated base deficit. Key points to consider when initiating a sodium bicarbonate drip include:

• Calculating the bicarbonate deficit and administering half of it over 4-8 hours
• Using a typical concentration of 150 mEq of sodium bicarbonate in 1L of D5W
• Infusing at a rate of 1-1.5 mEq/kg/hour
• Adjusting the drip based on serial arterial blood gas measurements and electrolyte levels
• Monitoring for potential complications such as hypernatremia and hypokalemia.

From the FDA Drug Label

In cardiac arrest, a rapid intravenous dose of one to two 50 mL syringes (44.6 to 100 mEq) may be given initially and continued at a rate of 50 mL (44. 6 to 50 mEq) every 5 to 10 minutes if necessary (as indicated by arterial pH and blood gas monitoring) to reverse the acidosis. In less urgent forms of metabolic acidosis, Sodium Bicarbonate Injection, USP may be added to other intravenous fluids The amount of bicarbonate to be given to older children and adults over a four-to-eight-hour period is approximately 2 to 5 mEq/kg of body weight – depending upon the severity of the acidosis as judged by the lowering of total CO2 content, blood pH and clinical condition of the patient

The dose and indications for starting a sodium bicarbonate (NaHCO3) drip in a patient with acute metabolic acidosis are:

• Initial dose in cardiac arrest: 1-2 syringes of 50 mL (44.6-100 mEq) given rapidly, followed by 50 mL (44.6-50 mEq) every 5-10 minutes as needed.
• Dose in less urgent cases: 2-5 mEq/kg body weight over 4-8 hours, depending on the severity of the acidosis.
• Indications: Metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest, and severe primary lactic acidosis 2, 2.

From the Research

Dose and Indications for Sodium Bicarbonate Drip in Acute Metabolic Acidosis

• The dose and indications for starting a sodium bicarbonate (NaHCO3) drip in a patient with acute metabolic acidosis are based on the severity of the acidosis and the patient's clinical condition 3, 4.
• Severe metabolic acidosis is defined by a pH < 7.2 with HCO3- < 8 mEq/L in plasma, and its best treatment is to correct the underlying cause 3.
• The indication for NaHCO3 therapy requires a risk-benefit assessment, considering its complications such as hypernatremia, hypokalemia, ionic hypocalcemia, rebound alkalosis, and intracellular acidosis 3.
• Bicarbonate should be given at an arterial blood pH of ≤7.0, and the amount given should be what is calculated to bring the pH up to 7.2 4.
• In patients with acute lactic acidosis and ketoacidosis, lactate and ketone bodies can be converted back to bicarbonate if the clinical situation improves, and therapy must be individualized 4.
• The use of sodium bicarbonate for management of diabetic ketosis and lactic acidosis has been controversial, but it is now the treatment of choice in certain cases 5.
• However, the most recent guidelines strongly recommend against the use of bicarbonate in patients with pH at least 7.15, while deferring judgment in more severe acidemia 6.

Administration and Monitoring

• Isotonic solutions should be preferred instead of hypertonic bicarbonate to prevent hypernatremia 3.
• Calcium must be provided for hypocalcemia to improve cardiovascular function 3.
• The patient will require monitoring with serial evaluation of the internal environment, especially arterial blood gases, plasma electrolytes, and ionized calcium 3.
• Effective therapy of lactic acidosis due to shock is to reverse the cause, and bicarbonate therapy should be used with caution and only in severe cases 6.

Calculation of Bicarbonate Deficit

• It is possible to estimate the bicarbonate deficit, speed, and volume of its infusion, but the calculations are only for reference 3.
• More important is to start intravenous NaHCO3 when needed, administer it judiciously, manage its side effects, and continue it to a safe goal 3.