Page 389 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Technical Aspects of Fluid Therapy 379

A B

C
Figure 15-10 Fluid pumps. A, A peristaltic pump, with its fluid path exposed to show the peristalsis
mechanism (arrow), which massages fluid through the tubing set. B, A volumetric pump that requires a
specific in-line cassette that snaps into the drive mechanism. C, A syringe pump useful for administration of
drugs and very slow administration of fluids.

hydration status in sick dogs and should not be relied measurements in as technically precise a manner as possi-
upon as sole measures of hydration. 31 Finding a high ble and to obtain consecutive measurements with the
urine specific gravity in animals capable of concentrating patient in the same position each time. As with any moni-
their urine assists in detection of inadequate circulating toring tool, CVP measurements must be interpreted in
blood volume (in animals being treated for shock or light of other diagnostic findings, and the pitfall of relying
extracellular fluid losses) or inadequate administration too heavily on a single test must be avoided.
of water (in animals receiving maintenance fluid therapy). The CVP is the blood pressure within the intrathoracic
portions of the cranial or caudal vena cava. CVP is
CENTRAL VENOUS PRESSURE measured clinically for two reasons: (1) to gain informa-
MONITORING tion about cardiac function, and (2) to gain information
about intravascular blood volume. The CVP is slightly
CVP measurement is a useful diagnostic procedure for higher than the mean right atrial pressure (RAP), and
hemodynamic assessment and management of fluid the two terms, CVP and RAP, are sometimes used inter-
therapy in critically ill animals. It can be used in a variety changeably. However, in some circumstances, the mean
of situations to assist in diagnosis and optimal fluid RAP may vary independently of CVP. 81 The CVP (or
therapy management. It is important to obtain CVP RAP) affects, and is affected by, cardiac output. RAP is