Page 265 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

256 ACID-BASE DISORDERS

(mEq/L) (mEq/L) (mEq/L)
Cations Anions Cations Anions Cations Anions

Sodium 145 110 Chloride 145 125 Chloride 145 110 Chloride

Bicarbonate (21) Bicarbonate (6) Bicarbonate (6)
Phosphates (2) Phosphates (2) Phosphates (2)
Sulfates (2) Sulfates (2) Sulfates (2)
Lactate (2) Lactate (2) Lactate (17)
Potassium
Other organic Other organic Other organic
Calcium 4 16 anions (3) 4 16 anions (3) 4 16 anions (3)
Magnesium 5 Plasma proteins 5 Plasma proteins 5 Plasma proteins
(2)
Total: Total: Total: Total:
156 mEq/L 156 mEq/L 156 mEq/L 156 mEq/L
Normal dog Pure hyperchloremic Pure normochloremic
(normal anion gap) (increased anion gap)
metabolic acidosis metabolic acidosis due
to lactate accumulation
A B C
Figure 10-2 Theoretical examples of electrolyte distribution in (A) normal canine plasma, (B) a dog with
pure hyperchloremic (normal anion gap) metabolic acidosis, and (C) a dog with normochloremic (increased
anion gap) metabolic acidosis caused by lactate accumulation (i.e., lactic acidosis). (Adapted from Toto RD.
Metabolic acid-base disorders. In: Kokko JP, Tannen RL, editors. Fluids and electrolytes, 2nd ed. Philadelphia:
WB Saunders, 1990: 324.)

to balance the decrease in plasma HCO 3 concentration.
Pancreatic juice
In the following discussion, the causes of metabolic aci-
160 Na
dosis have been divided into those associated with a nor-
mal anion gap and those associated with an increased 140
anion gap. 120
DISORDERS ASSOCIATED WITH A 100 HCO 3
NORMAL ANION GAP Concentration (mEq/L)
Diarrhea 80

The concentration of HCO 3 in intestinal fluid usually is 60

higher than that of plasma, whereas its Cl concentration 40
islower.Thisresultsfromtheadditionofalkalinepancreatic Cl
and biliary secretions to luminal contents and from secre- 20
K
tion of HCO 3 in exchange for Cl in the ileum
0
(Fig. 10-3 and Table 10-1). In some diseases of the small 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
intestine, increased delivery of ileal contents to the colon Secretory rate (ml/min)
may overwhelm the considerable capacity of the colon for Figure 10-3 Influence of secretory rate on electrolyte
reabsorption of fluid and electrolytes. As a result, severe composition of canine pancreatic juice. Note the inverse

acute small bowel diarrhea may cause loss of HCO 3 in relationship between Cl and HCO 3 concentrations and the

þ
þ
excess of Cl with resultant hyperchloremic metabolic relatively constant concentrations of Na and K . (From Cohen JJ,
acidosis. The acidosis is not purely hyperchloremic but Kassirer JP. Acid-base. Boston: Little, Brown, 1982: 135.)