Page 176 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

166 ELECTROLYTE DISORDERS

BOX 6-6 Conditions Associated with Hypocalcemia

Common Uncommon
Hypoalbuminemia Laboratory error
Chronic renal failure Improper sample anticoagulant (EDTA)
Puerperal tetany (eclampsia) Infarction of parathyroid gland adenoma
Acute renal failure Rapid intravenous infusion of phosphates
Acute pancreatitis Acute calcium-free intravenous infusion (dilutional)
Undefined cause (mild hypocalcemia) Intestinal malabsorption or severe starvation
Hypovitaminosis D
Occasional Blood transfusion (citrated anticoagulant)
Soft tissue trauma or rhabdomyolysis Hypomagnesemia
Hypoparathyroidism Nutritional secondary hyperparathyroidism
Primary Tumor lysis syndrome
Idiopathic or spontaneous
Postoperative bilateral thyroidectomy Human
After sudden reversal of chronic hypercalcemia Pseudohypoparathyroidism
Secondary to magnesium depletion or excess Drug-induced
Ethylene glycol intoxication Hypercalcitonism
Phosphate enema Osteoblastic bone neoplasia (prostate cancer)
After NaHCO 3 administration

TABLE 6-4 Anticipated Changes in Calcemic Hormones and Serum Biochemistry
Associated with Disorders of Hypocalcemia
1,25 PTG
Corr 25 (OH) ULS,
tCa iCa alb tCa Pi PTH PTHrP (OH)-D 2-D Surgery

Primary # # N # " N # N N N N # Multiple #
hypoparathyroidism
Pseudohypoparathyroidism # N # N # " N " N N N " N "
Sepsis/critical care # N # N # N N " " N N N N N
Ethylene glycol toxicity # # N # " N " N N # N N
Paraneoplastic # # N # # " N N N N N "
Phosphate enema # # N # " " N N N #" N
Eclampsia # # N # # Mild N N N # N
",N
Hypoalbuminemia # # N # N N N " N N N " N "

#, Decreased concentration; ", increased concentration; N, normal; tCa, serum total calcium; iCa, serum ionized calcium; alb, albumin; Corr tCa, corrected
total calcium; Pi, inorganic phosphorus; PTH, parathyroid hormone; PTHrP, parathyroid hormone related protein; 25(OH)-D, 25-hydroxyvitamin D; 1,25
(OH)2-D, 1,25-dihydroxyvitamin D; PTG, parathyroid gland; ULS, ultrasound.

because hypocalcemia results from reduced intestinal cal- 17% of the dogs with CRF. Thus, iCa concentration
cium absorption and increased skeletal resistance to was low in the majority of dogs despite the presence of
PTH. 404 Animals with CRF and decreased serum tCa metabolic acidosis in 83% of dogs, which would be
concentration are most often asymptomatic, possibly expected to increase iCa. 303 Hypocalcemia was diagnosed
because of an increase in iCa concentration that more frequently in a study of 489 dogs with CRF when
accompanies metabolic acidosis. determined by iCa measurement. Based on serum tCa
Serum tCa concentration was 8.0 mg/dL or less in measurement, hypocalcemia was noted in only 19% of
10% of 268 dogs with clinical CRF, whereas low serum dogs with CRF; when iCa concentration was measured,
iCa concentrations were detected in 40% of affected hypocalcemia was observed in 29% of dogs with CRF. 519
dogs. 118 In 23 dogs with CRF, iCa represented 40% of In 74 cats with clinical CRF, 15% were hypocalcemic
tCa as compared with 51% of tCa in normal dogs. 303 based on serum tCa. 147 In cats with CRF, hypocalcemia
Serum iCa was low in 56%, normal in 26%, and high in was found more commonly with higher magnitudes of