Practical Matters: Intravenous solutions: Should I worry about osmolarity?

Peripheral venous catheters are most commonly used to deliver intravenous fluids and drugs. However, administering hyperosmolar solutions may cause vascular endothelial damage and thrombophlebitis. Solutions with an osmolarity < 600 mOsm/L can be delivered safely through a peripheral intravenous catheter. But solutions that have an osmolarity > 600 mOsm/L should be delivered through a central venous catheter if possible or delivered concurrently with intravenous fluids through a Y-connector into a peripheral vein. Emergent patients may require hyperosmolar drug therapy through a peripheral venous catheter for initial stabilization, but once stabilized, animals that require repeated hyperosmolar drug administration or continuous infusions of hyperosmolar drugs will benefit from delivery through a centrally placed venous catheter.

A peripheral venous catheter can be used to safely administer isotonic crystalloids, synthetic colloids, blood products, 5% dextrose solutions, 10% dextrose solutions, and partial parenteral nutrition. In stable patients, a central venous catheter should be used to administer > 10% dextrose solutions, total parenteral nutrition, 8.4% sodium bicarbonate, 25% mannitol, hypertonic saline (> 2%), and diazepam. In addition, it is important to realize that the osmolarity of combined solutions may be substantially increased (e.g. isotonic crystalloids with potassium chloride). All indwelling catheter sites should be inspected carefully on a daily basis for evidence of inflammation or thrombophlebitis (firm, ropy vessels).

Deborah Silverstein, DVM, DACVECC

Department of Clinical Studies

Matthew J. Ryan Veterinary Teaching Hospital

University of Pennsylvania

Philadelphia, PA 19104-6010

Deborah Silverstein, DVM, DACVECC