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Mis-use of medical terms can cause confusion by leading to conclusions that are either not applicable or completely erroneous. A classic example often occurs in discussions about fluid therapy among feline caregivers who substitute "over-hydration" for "volume overload" as creating a hazard of congestive heart failure. The fallacy is that these terms refer to diametrically opposite states in the body! The problem isn't just semantic, because such a misunderstanding can lead to misguided treatment decisions in real life . Over-hydration occurs when the sodium concentration of the blood is diluted by an excess of water, resulting in hyponatremia. This does not occur from administration of subcutaneous fluids but rather is most often seen in human athletes who drink plain water after strenuous exercise instead of electrolyte drinks like Gatorade. https://en.wikipedia.org/wiki/Water_intoxication In a state of overhydration excess water leaves the blood and enters the cells. Because of this, it does not increase circulating volume. Volume Overload is a state in which the amount of blood exceeds the capacity that the vascular system can contain (hypervolemia). The system compensates to a certain degree by dilating the blood vessels but a limit may be reached at which the pressure increases, especially if the influx of fluid is rapid. When there are weak points such as defective heart valves this pressure may result in leakage of serous fluid into adjoining spaces (or organs). These effusions can accumulate to such an extent that they interfere with pulmonary or cardiac function, which is then referred to as congestive heart failure (CHF). Hypervolemia is generally linked to one of two causes:
Sub-q therapy with Lactated Ringer's does not present either of these risks, whether given for maintenance or diuresis. Detailed explanations may be found at: Sub-Q_vs_IV and Ringers_vs_Saline Those wishing to acquire a solid understanding of fluids and the heart are encouraged to get the following books, which may be found on the Veterinary Bookshelf: Fluid, Electrolyte and Acid-Base Disorders in Small Animal Practice (free) |