Chapter 167 Crystalloid Fluid Therapy

Question 1

The need for fluid therapy may be divided into three categories

Answer 1

1. resuscitation (correction of hypovolemia by restoration of intravascular volume)
2. rehydration (replacement of extravascular fluid)
3. maintenance (maintaining normal hydration status)

Question 2

True or False?

Not all patients that are dehydrated are in shock

Answer 2

True

Question 3

True or False?

Not all patients that are in hypovolemic shock are dehydrated.

Answer 3

True

Question 4

Normal plasma osmolality in dogs and cats?

osmolalities of isotonic replacement crystalloids?

Answer 4

290–310mOsm/L in dogs
311–322 mOsm/L in cats

typically have an in the range of 270–310 mOsm/L
LRS 272 mOsm/L
Normosol-R 296 mOsm/L
0.9% NaCl 308 mOsm/L

Question 5

The main difference between replacement and maintenance crystalloids?

Answer 5

The main difference is in their electrolyte concentrations.

Replacement fluids are relatively isotonic to the ECF and are intended to replace lost body fluids and electrolytes.

Maintenance crystalloids contain approximately half the sodium and chloride concentrations of replacement crystalloids. Therefore, maintenance fluids are hypotonic to the normal patient. Maintenance fluid therapy is designed to meet the patient’s sensible and insensible fluid losses. These fluids are appropriate to use in patients that do not have any ongoing losses who are unable to maintain normal fluid and electrolyte intake.

Question 6

What is the crystalloid 5% dextrose in water (D5W)?

Answer 6

D5W is considered hypotonic, as there is no sodium in this fluid to produce osmolality.
Dextrose is added to this solution to prevent hemolysis or vascular endothelial damage but once administered, the dextrose is metabolized to carbon dioxide and water.

Administering D5W is therefore effectively delivering intravenous free water, which is then distributed equally according to the distribution of total body water. Thus, D5W is only used to correct free water deficits.

Question 7

When do you use hypotonic fluids?

Answer 7

Hypotonic fluids distribute throughout both intracellular and extracellular fluid compartments; the larger volume of distribution relative to isotonic fluids and the free water content make these fluids a safer choice for treating patients that have decreased ability to excrete excess sodium or tolerate an increased intravascular volume (such as those with chronic kidney disease or heart disease).

Question 8

volume expansion via hypertonic saline administration is relatively short-lived (<30min) WHY?

Answer 8

Due to the redistribution of electrolytes throughout the extracellular space

Question 9

Why is it important not to administer hypertonic saline at a rate greater than 1mL/kg/min?

Answer 9

Rapid hypertonic saline infusion can result in hypotension associated with effects on the central vasomotor center or via peripheral vasomotor effects.

*Due to the decreased total peripheral resistance

Question 10

The negative effects of giving 0.9% saline in sick dogs?

Answer 10

Both animal and human experimental models have shown that infusions of moderate to large volumes of 0.9% saline can cause a hyperchloremic metabolic acidosis;
result in greater extravascular expansion and increased risk of interstitial edema;
and result in renal vasoconstriction and reduced GFR, leading to salt and water retention,