Page 384 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

374 FLUID THERAPY

A B

C D

E F
Figure 15-8 Proper injection and blood collection technique. A, Using a conventional “T” piece (the
principlesarethesameifusinganinjectioncap),fluidadministration hasbeeninterrupted,andthe extensiontube
onthe“T”piecehasbeenclamped(arrow).Therubberdiaphragmoftheinjectionportiscleanedwithalcoholand
allowed to air dry. B, Proper needle insertion for injection ports and medication bottles. After the needle tip
contacts the rubber surface, the needle is dragged slightly away from the bevel orifice (in the direction of
the arrow). This stretches the rubber surface at the injection point and reduces the likelihood of “coring” the
rubber with the needle during insertion. When the needle is withdrawn, the rubber will return to its original
conformation and seal the needle tract. C, Use needles less than 20 gauge to inject or aspirate through the
injection ports. A 3- to 6-mL purge sample is collected by inserting a 22-gauge needle just inside the rubber
diaphragm. This purges the dead space of the injection port and the catheter. After the purge sample is collected,
the needle is withdrawn from the injection port, capped, and set aside. D, The syringe used for sample collection
is attached to a new 22-gauge needle that is inserted all the way to the hub. This allows the needle to
bypass the injection port dead space during sample collection. E, After sample collection, the purge sample is
returned by injection. A 3-mL syringe with (heparinized) saline flush with a 22-gauge injection needle is used to
flushthepurgesamplecompletelyintotheanimal.Theneedleisadvancedjustinsidetherubberdiaphragm,and
0.5 to 2.0 mL of flush is injected. F, The injection of flush is continued as the needle is completely
withdrawn. If the injection ceases before needle withdrawal, removal of the needle will create a vacuum that
pulls blood back into the tip of the catheter, creating a potential obstruction with a clot. When removed, a fully
seated 22-gauge injection needlewill pull blood into the distal 5 cm (2 inches) of a 22-gauge intravenous catheter.