Compatibility of calcium chloride with milrinone, epinephrine, vasopressin, and heparin via in vitro testing and simulated Y-site administration

Purpose: The purpose of this study is to evaluate calcium chloride (CaCl) compatibility with commercially available and extemporaneously compounded milrinone, vasopressin, epinephrine, and heparin. This report describes 2 clinical scenarios in which patients experienced intravenous catheter precipitation when receiving multiple continuous infusions, including CaCl, and the results of an in vitro simulation of those scenarios. The hypothesis was that one or a combination of the medications would precipitate with CaCl. Methods: CaCl compatibility was tested in 3 stages to simulate clinical situations where line precipitation occurred. Multiple tests were conducted in each stage to determine if precipitation had occurred, including visual assessment, absorbance measurement at 650 nm, and pH measurement. First, milrinone, vasopressin, epinephrine, and heparin were mixed pairwise with CaCl in a test tube. Second, the medications were mixed in different combinations deemed likely to precipitate. Finally, 5 medications were infused via simulated Y-site administration. Incompatibility was defined as observed crystals, haziness, or turbidity upon visual inspection or absorbance of greater than 0.01 absorbance unit (AU). All solutions were tested at time 0 and at 20, 60, 240, and 1,440 minutes. Results: Across all tests, only a commercially available formulation of heparin 2 units/mL in 0.9% sodium chloride injection precipitated with CaCl, alone or in combination with other medications. Upon further review, it was found that this specific formulation of heparin contained a monohydrate and dibasic sodium phosphate buffer. Conclusion: CaCl only precipitated with a commercially available heparin formulation that contained a phosphate buffer. CaCl was deemed to be compatible with all other medications and formulations tested.