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This Manual has been designed for use in the NICU at London Health Sciences Centre (LHSC), London, Ontario, Canada, and represents clinical practice at this institution. The information contained within the Manual may not be applicable to other centres. If users of this Manual are not familiar with a drug, it is recommended that the official monograph be consulted before it is prescribed and administered. Any user of this information is advised that the contributors, Editor and LHSC are not responsible for any errors or omissions, and / or any consequences arising from the use of the information in this Manual.

SODIUM BICARBONATE
(NaHCO3)

Indication

  • used as an alkalinizing agent in the treatment of metabolic acidosis and in advanced cardiac life support during cardiopulmonary resuscitation

Pharmacology

  • sodium bicarbonate (NaHCO3) is an alkalinizing agent which dissociates to provide bicarbonate ion
  • the bicarbonate/carbonic acid (HCO3/H2CO3) system is the principal extracellular buffer in the body:
    HCO3 + H+ ==== H2CO3
  • the componets of this buffer system (HCO3, pH) are routinely measured to assess acid-base status
  • in an aqueous solution carbonic acid breaks down to form carbon dioxide (CO2) and water (H2O):
    CA
    HCO3 + H+ ==== H2CO3 ==== CO2 + H2O
  • the enzyme carbonic anhydrase (CA) catalyzes the interconversion of H2CO3 and CO2; it is present in red blood cells, renal tubular cells, and other tissues
  • a large portion of the CO2 is normally exhaled by the lungs - this aids in the tight control of acid-base balance
  • the arterial HCO3 concentration is primarily regulated by the kidneys; CO2 tension is controlled by the lungs
  • the administration of sodium bicarbonate can therefore increase the CO2 levels of babies in respiratory failure.
  • although it corrects the metabolic component of acidosis, it may make respiratory failure worse, therefore, it is contraindicated in pure respiratory acidosis or in the combination of respiratory and metabolic acidosis, until the respiratory failure and normalization of the pCO2 has been achieved.

Side Effects

  • extravasation can cause chemical cellulitis, resulting in tissue necrosis, ulceration and/or sloughing at the injection site; extravasation should be treated by elevating the affected area, applying warm compresses, and locally injecting lidocaine or hyaluronidase
  • it is very hypertonic solution (even after a 1:1 dilution); there is increased risk of intraventricular hemorrhage when given to premature babies (a 1.5% solution of sodium bicarbonate is isotonic)
  • the administration of sodium bicarbonate may lead to hypernatremia and water retention, which potentiates the risk of congestive heart failure, overhydration or pulmonary edema
  • sodium bicarbonate can result in hypokalemia, which can predispose to metabolic alkalosis; therefore, check the blood gases, in additionto periodic serum electolyte determinations
  • in excess, it can cause metabolic alkalosis; therefore, check the blood gases, in addition to periodic serum electrolyte determinations
  • a rise in serum pH, caused by sodium bicarbonate, results in increased binding of calcium to albumin, and can cause the reduction in ionized calcium levels; therefore, babies may become twitchy and hypocalcemic (hence the periodic additional infusions of Calcium Gluconate)
  • because of increased risk of intraventricular hemorrhage with rapid administration, sodium bicarbonate should be avoided in premature infants where possible

Miscellaneous

  • sodium bicarbonate is physically and/or chemically incompatible with many drugs; consult the IV admixture charts and/or call the Pharmacy for compatibility information
  • SODIUM BICARBONATE AND TPN / LIPID SHOULD BE REGARDED AS INCOMPATIBLE

Dose

  1. TREATMENT OF DOCUMENTED METABOLIC ACIDOSIS DURING PROLONGED RESUSCITATION
    • 2 mEq/kg (2 mmol/kg) (this is equivalent to 4 mL/kg of a 4.2% concentration)
    • use a concentration of 4.2% (0.5 mEq/mL, 0.5 mmol/mL)
    • IV push over a least 2 minutes (1 mEq/kg/min = 1 mMol/kg/min = 2mL/kg/min) by a physician (may be given by a certified RN under a physician's supervision)
  2. TO CORRECT A METABOLIC ACIDOSIS, THE DOSE OF SODIUM BICARBONATE AS AN INFUSION IS GIVEN AS FOLLOWS

    # mmol NaHCO3 required = 0.5 to 1 mmol/kg/h
    • The base deficit, serum bicarbonate and serum Na should be monitored closely, and the infusion should be re-assessed every 2 hours.
    • the concentration of the infusion should always be 4.2% (ie, 0.5 mmol/mL) or less - a 4.2% solution is hypertonic (a 1.5% solution is isotonic).
    • dilute 8.4% NaHCO3 with an equal volume of sterile water for injection to prepare a 4.2% solution (do not use the pre-loaded 4.2% syringes for an infusion)
    • if the infant is hypernatremic, consider THAM
    • a 4.2% solution is hypertonic (a 1.5% solution is isotonic).

Sample Calculation

A 2.6 kg baby is to receive a 6 hour infusion of sodium bicarbonate.
Sodium bicarbonate is available as a 4.2% solution for infusion (equivalent to 0.5 mmol/mL).

The # mmol NaHCO3 required is 0.5 to 1 mmol/kg/h.
As an example, 0.75 mmol/kg/h is required.

The # mmol NaHCO3 required is:

0.75 mmol/kg/h x 2.6 kg = 1.95 mmol/h

Given a 0.5 mmol/mL solution, the infusion rate is:

1.95 mmol/h
0.5 mmol/mL
=3.9 mL/h

Supplied

  • 4.2% (0.5 mEq/mL, 0.5 mmol/mL), 10mL pre-loaded syringe (for resuscitation use only)
  • 8.4% (1 mEq/mL, 1 mmol/mL), 50mL single use vial, (use to prepare a 4.2% solution for infusion).

Reference

  1. McEvoy G K (ed): AHFS Drug Information, American Society of Hospital Pharmacists, 1991.
  2. Babson SG, Benson RC, Pernoll ML and Benda GI: Management of high risk pregnancy and intensive care of the neonate, CV Mosby Company, St. Louis, 1975
  3. Applied Therapeutics - The Clinical Use of Drugs, Koda-Kimble MA and Young LY (Eds), Applied Therapeutics, Inc, Vancouver, Washington, 5th Edition, 1992.
  4. Bloom RS, Cropley C and Drew CR: Textbook of Neonatal Resuscitation American Heart Association, American Academy of Paediatrics, 1987.
  5. Taketomo CK, Hodding JH and Kraus DM: Pediatric Dosage Handbook, Lexi-Comp Inc., Cleveland, 1992.

Update: 24 May 2002


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