How to manage intraosseous catheters in exotic species

An intraosseous (IO) catheter is a hollow needle which is placed into the intramedullary cavity to administer medications and fluids (Figure 1). IO catheterisation is often discussed during veterinary nurse training. The route can be used for fluid administration and for many drugs and veterinary nurses are taught about this route as an option in all of their patients. However, once qualified, in the author's experience this route of administration is rarely used in general practice. This is probably because the majority of patients seen in small animal practice have veins of a sufficient size for peripheral intravenous (IV) catheterisation. For this reason, IO catheters are usually reserved for the critical patient where cardiovascular collapse may mean that IV access is difficult. They are most commonly used in very small patients, such as neonates or exotic species, in which venous access is impossible (Lind, 2016). Any fluid that can be given intravenously (e.g. blood, balanced electrolyte solution, glucose) can also be given by the IO route (Macintire, 2008), making this route invaluable in debilitated patients. Administration of crystalloid and/or colloidal fluids through the intramedullary cavity has the same efficacy and an equivalent absorption rate to the intravenous route. In fact, over 50% of the administered IO fluid passes into the central circulation within 30 seconds of it being administered to the patient (Lamberski et al, 1991). Fluids can be given in short regular bolus rates or alternatively, if tolerated, by constant rate infusion (CRI) using a syringe driver or infusion pump.