Certified Registered Nurse Infusion (CRNI) Practice Exam 2025 - Free CRNI Practice Questions and Study Guide

Mixing Dilantin only with D5 (5% dextrose in water) is recommended to avoid vein irritation because Dilantin, or phenytoin, can be quite irritative to the veins if not administered properly. The solution is more compatible with dextrose than with other solutions, particularly saline, which can lead to precipitation and potentially harmful reactions. By using D5, the solubility of the medication is enhanced, thus reducing the risk of irritation and damage to the endothelial lining of the veins during infusion.

To further understand the context, Dilantin should generally not be administered directly into the bloodstream without appropriate dilution, as this increases the risk of irritation. Using a large bore needle may help with flow but does not specifically address the chemical properties of Dilantin that cause irritation. Administering with saline can also lead to incompatibilities, potentially resulting in a precipitate that could occlude a vein or cause irritation. Hence, using D5 is the best practice in preventing vein irritation during administration of Dilantin.