Page 164 - Basic Monitoring in Canine and Feline Emergency Patients

VetBooks.ir 8 Electrolyte Monitoring

ElizabEth J. thomovsky*

Purdue University College of Veterinary Medicine, West Lafayette, Indiana, USA

This chapter will review electrolytes of immediate Therefore, when interpreting changes in sodium, it
concern (sodium, calcium, phosphorus, and potas- is important to remember that in most cases, the
sium) that often need to be monitored and treated hyper- or hyponatremia is actually due to changes
in the emergent patient, their basic function in the in the water levels in the bloodstream, rather than
body, and the most common situations that war- actual alterations in the amount of sodium. This is
rant monitoring of each electrolyte. It is important why terminology that is often used in the literature
to recognize when electrolytes need persistent and to describe changes in sodium refers to the free
continual monitoring and when electrolytes require water deficit. Essentially when there is a free water
less intense monitoring. The methods of measure- deficit and water levels are low in the blood, then
ment of each electrolyte as well as possible pitfalls the sodium is high (i.e. the decrease in water con-
in measurement will also be presented in addition centrates the sodium particles, resulting in hyperna-
to several clinical examples of electrolyte monitoring tremia). Conversely, when there is a free water
in action. excess and water levels are relatively high in the
blood, the sodium is low (i.e. the increased water
dilutes the sodium particles in solution, resulting in
8.1 Basic Physiology and Anatomy hyponatremia).
See Fig. 8.1 for the basic mechanisms underlying
Sodium
the development of hypernatremia and hypona-
Sodium (Na) is ubiquitous in the body and is inti- tremia. Interested readers can obtain more detail
mately involved in control of osmolality in the regarding sodium regulation in the Further Reading
blood, cells, and interstitial tissues. The location of section. While not the focus of this chapter, changes
sodium particles (intracellular versus extracellular) in serum sodium concentration should also be asso-
is determined by the action of sodium transporters ciated with similar changes in serum chloride (Cl)
and Na/K (potassium) ATPase pumps. In many levels, as alterations in overall water content of the
locations in the body such as the brain, heart, kid- blood should dilute or concentrate both ions con-
neys, and skeletal muscle, sodium is preferentially currently. In order to know if the increase or
moved into one location in order to set up a con- decrease of chloride relative to sodium/water is
centration gradient across cell membranes; mainte- proportional, mathematical corrections (see
nance of this gradient is crucial for appropriate Chapter 5) can be applied to ‘correct’ the chloride
cellular and organ function. Because sodium is so relative to the free water gain or loss. Gains or
abundant in the body, changes in sodium concen- losses of chloride in excess of what can be explained
trations can be related to multiple different sys- by changes in sodium/water levels have their great-
tems. In addition, the animal’s sodium level is a est impact on regulation of the acid–base status of
concentration, usually measured in mmol or mEq the body, as further discussed in Chapter 5.
of sodium/dL of water on blood work. This means In general, large alterations in sodium (either
that the amount of body water can have profound high or low) can lead to clinical signs in the patient.
effects on the sodium reported in a blood panel. However, relatively small changes in sodium that

* Corresponding author: ethomovs@purdue.edu

156 © CAB International, 2020. Basic Monitoring in Canine and Feline Emergency Patients
(eds E.J. Thomovsky, P.A. Johnson and A.C. Brooks)