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Which IV calcium: chloride or gluconate?

From the May 7,1997 Issue

Problem: Some hospitals store both calcium gluconate and calcium chloride in floor stock, in automated dispensing modules or in emergency kits. There is a three-fold difference in the primary cation between calcium gluconate, which contains 4.65 mEq Ca++/gram, and calcium chloride, which contains 13.6 mEq Ca++/gram. When ordering IV calcium, this difference has important implications. Calcium chloride is more irritating when given IV. Confusion may also occur in ordering intramuscular calcium. Calcium chloride is extremely irritating and should never be given IM.1 Since intravenous calcium is often ordered without specifying which salt is desired (e.g., gluconate or chloride), the implications of storing these alongside one another in patient care areas are obvious.

Serum phosphorus levels are important to consider when replacing calcium. If serum phosphate is elevated during IV calcium administration, precipitation of calcium phosphate may occur in the vasculature with potential end organ injury such as interstitial pneumonitis.2 When serum phosphorus is low, larger quantities of calcium may be needed for replacement. Levels of calcium and phosphorus must be carefully monitored. Specific problems reported with calcium include:

  • Interactions with digoxin - rapid injection of calcium may cause bradyarrhythmias, especially in patients on digoxin.3
  • Antagonism of calcium channel blockers resulting in blood pressure elevation
  • Extravasation causing tissue necrosis.

Incorrect calcium to phosphate ratios (which are dependent upon the order of mixing, the mixing process, phosphate content of the amino acid solution, volume at time calcium is added, and pH) could lead to precipitation and end organ injury or death.4 Precipitation may be impossible to detect visually when the TPN is mixed with lipids.

Safe Practice Recommendation: The Institute for Safe Medication Practices and the Institute for Healthcare Improvement in Boston are preparing a document about high hazard medications. The following recommendations are made to reduce adverse drug events with calcium:

  1. Reduce available options: Use either calcium gluconate or calcium chloride in an institution, but not both.
  2. To avoid calcium phosphate precipitation, prepare solutions containing calcium and phosphorus only in the pharmacy, using standard protocols. Avoid mixing with lipids because visible precipitation will be obscured.
  3. 1. Standardize ordering: calcium should be ordered based on the number of mEq of calcium. Calcium should never be ordered by number of "amps" or "mLs." The salt should always be expressed.
  4. Standardize administration: Develop a standard administration protocol including rules for rate of administration and monitoring of calcium, phosphate and albumin levels prior to administration.

To monitor safe use of calcium salts, ISMP and IHI recommend measuring the percentage of times IV calcium use is deemed to have been administered in accordance with standards. Intermittently review a sample of cases where IV calcium was administered. [D, N, P]

Reference: 1. Lacy C, Armstrong LL, Naomi Ingrim, Lance LL, 4th ed. Drug Information Handbook. 4th ed. Hudson: Lexi-Comp. 1996. 2. Knowles JB et al. Pulmonary deposition of calcium phosphate crystals as a complication of home total parenteral nutrition. JPEN 1989;13:209-13. 3. Facts and Comparisons. St. Louis:Wolters Kluwer;1997. 4. FDA Safety Alert, April 18, 1994

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