Hyponatremic pinnipeds may present seizuring or comatose (see Chapter 41, Seals and
Sea Lions). Distinction from hypoglycemia and diagnosis of hyponatremia are based on
decreased sodium and chloride levels in serum. Adult sea lions may show symptoms of
varying severity with serum sodium levels below 147 mEq/l (Geraci, 1972). An important
predisposing factor is housing in fresh water. Treatment with saline intravenously, subcutaneously,
or even intraperitoneally can result in therapeutic response. A 40-kg (88-lb)
juvenile California sea lion that presented comatose, with serum sodium of 116 mEq/l, was
given 3.5 l of saline subcutaneously. This animal began to show a return of some reflexes
within 1 hour. Over the next 48 hours, the sea lion progressed to sitting up and being attentive
to its surroundings. Supplementation with subcutaneous saline was continued until the
serum sodium levels were greater than 140 mEq/l, and the animal was eating fish with 2 to
3 g of sodium chloride/kg of food