Measurement of Central Venous Pressure. Small Animal Diagnostic and Treatment Techniques

The equipment needed for measurement of central venous pressure includes a sterile bag or bottle of fluids (a) with attached fluid administration set (b), an IV extension set (c), a manometer (d) and a stopcock (e).

The tip of the manometer where it tapers to fit into the stopcock (arrow) is the weakest point in the system. When turning the pointer on the stopcock (f ), hold the bottom of the manometer or the tip of the manometer may snap off.

The direction the white knob is pointed is the OFF position of the stopcock. In the photographs below, the animal is on your left and the bag of fluids is on your right. The white arrows indicate the direction of fluid flow. Initially the white knob is turned straight up towards the manometer, allowing fluid to flow from the fluid bag to the patient's catheter to assure the catheter is patent (a). If fluid does not flow freely into the patient's catheter a valid CVP reading will not be obtained. Then the knob is turned toward the patient (b) and fluid will fill the manometer. The manometer should not contain any air bubbles. If air is present in the manometer or fluid line, let the fluids run, overfilling the manometer until all air is purged from the system. Then turn the knob toward the fluids (c). The level of fluid in the manometer will fall (the fluid is running into the patient's catheter) until the height of the fluid column exerts a pressure equivalent to the patient's central venous pressure. The top of the fluid column will slightly oscillate up and down as the animals' heart beats and as the animal breathes.

The bottom of the manometer is held at the level of the right atrium which is approximately the midpoint between the dorsum and ventrum. The white arrow points to the bottom of the stopcock attached to the manometer. The patient can be in sternal recumbency or lateral recumbency. Trends in central venous pressure are more informative than single values. Each time a CVP reading is obtained the patient should be in the same position. Normal values are 0-10cm of H₂0