Page 171 - Basic Monitoring in Canine and Feline Emergency Patients

sodium values with the administration of either There are no hard and fast rules as to when treat-
hypertonic fluids (hypertonic saline) or hypotonic ment must occur for hypocalcemia or hypercalcemia.
VetBooks.ir fluids (5% dextrose in water or 0.45% sodium However, the author typically treats hypocalcemia
when iCa levels are less than 1.0 mmol/L and/or
chloride) in large quantities or over long periods of
time. See Table 8.1 for common diseases leading to
hypocalcemia despite higher iCa levels. Similarly,
sodium alterations. Box 8.1 provides broad sug- the patient is showing clinical signs suggestive of
gestions as to how often to measure serum sodium the author typically instigates treatment for
values in different hospitalized cases and case hypercalcemia when iCa levels are higher than
study 1 details a case in which aberrant sodium 1.4 mmol/L. The exception to these rules is
values were treated. An in-depth discussion of the extremely debilitated critically ill patients who
treatment of sodium disorders is beyond the focus often have ionized hypocalcemia. The etiology of
of this chapter (see Further Reading section for hypocalcemia of critical illness is multifactorial,
more information). including downregulation of vitamin D during
inflammatory states, causing decreased levels of
iCa. This is usually a transient change and resolu-
Calcium
tion of the underlying disease and inflammation
When working up an emergency patient, altered should normalize iCa levels. Therefore, critically ill
calcium levels are differentials for clinical signs patients typically do not require treatment for
such as polyuria or polydipsia, vomiting, tremors, their hypocalcemia unless the iCa is less than
arrhythmias, or weakness. Patients with conditions 0.70–0.80 mmol/L and/or they are showing clinical
such as dystocia that may receive calcium therapy signs compatible with hypocalcemia.
should also have baseline levels measured prior to
treatment. See Table 8.2 for a list of common dis-
eases for which hypercalcemia or hypocalcemia Phosphorus
are differentials, leading to the need to measure Measurement of phosphorus levels by themselves
calcium levels. Since iCa is the most clinically are not that important in most emergency or criti-
important fraction of calcium, when there is con- cally ill patients since the phosphorus levels will
cern that hypocalcemia or hypercalcemia is con- usually normalize with treatment of the underlying
tributing to the animal’s clinical condition, iCa disease (Table 8.3). The exception is when the
should be measured. underlying disease process directly causes extremes

Table 8.1. Diseases commonly associated with hyper- or hyponatremia.
Hypernatremia Hyponatremia
Loss of water in excess of sodium (free water loss): Gain of water in excess of sodium (free water gain):
● Vomiting ● Hyperglycemia
● Diarrhea ● Liver failure
● Renal failure ● Congestive heart failure
● Diuresis ● Renal failure
● Third space fluid accumulation (peritoneal or ● Excess antidiuretic hormone (e.g. syndrome
pleural effusion) inappropriate antidiuretic hormone)
● Deficiency of or lack of response to antidiuretic hormone
(e.g. central or nephrogenic diabetes insipidus) Loss of sodium in excess of water:
● Drugs (e.g. glucocorticoids, diuretics) ● Vomiting
● Fever ● Diarrhea
● Prolonged inadequate access to water ● Third space fluid accumulation (peritoneal or
pleural effusion)
Sodium gain: ● Cutaneous loss (e.g. burns, wounds)
● Ingest in diet (e.g. salt toxicity, paint ball intoxication) ● Hypoadrenocorticism
● Hypertonic saline administration ● Drugs (e.g. diuretics)
● Sodium bicarbonate administration
● Excess aldosterone (e.g. hyperaldosteronism)
● Hyperadrenocorticism

Electrolyte Monitoring 163