Comparison of vasopressin delivery via the proximal humerus and proximal tibia in healthy dogs under general anesthesia: implications for emergency intraosseous administration

During cardiopulmonary resuscitation, securing intravenous access for medication delivery can be problematic due to the size of the patient and vasoconstriction due to hypotension. The osseous route is a promising alternative to the intravenous route. The proximal humerus and proximal tibia are two commonly utilized sites in dogs. While some studies have reported the superiority of the proximal humerus route over the proximal tibia route for drug delivery in humans, there is a lack of knowledge on this topic in dogs. This study evaluated the difference in intraosseous vasopressin effect between the proximal humerus and proximal tibia in dogs. Seven healthy dogs were under general isoflurane anesthesia and intraosseous access was achieved in a crossover design. 0.05 U/kg vasopressin was administered and perfusion index (PI), heart rate (HR), and mean arterial blood pressure (MAP) were recorded. PI and HR decreased more dramatically when vasopressin was injected into the proximal humerus than into the proximal tibia, and MAP increased more distinctly when vasopressin was injected into the proximal humerus than into the proximal tibia. These results suggest that vasopressin is more effectively delivered when injected into the proximal humerus than into the proximal tibia. We performed histopathologic exploration of the humerus and tibia and found the difference in the distribution of vessels with cell composition of the bone marrow, and this would be a factor to affect the drug absorption of the each site. These results support the opinion that humerus is a superior intraosseous route for the administration of vasopressin.