Management of cetacean metabolic abnormalities poses challenges to the clinician due to this animal’s unique anatomy and water environment. Intravenous access can be accomplished in the fluke, peduncle, dorsal, or pectoral fins in cetaceans. Their vascular rete structure, however, can make it difficult to accurately deliver medications to veins as well as avoid extravasation of drugs and subsequent perivascular sloughing. Oral and subcutaneous delivery of therapeutic agents have proven effective in managing some cetacean metabolic abnormalities, including hypoglycemia, metabolic acidosis, and hypernatremia. While our discussion will include initial treatment options for these conditions, diagnosis, and correction of the underlying cause of the metabolic abnormality is the ultimate goal in managing the cetacean patient.
Clinical signs of hypoglycemia can occur when glucose levels drop below 70–80 mg/dl in cetaceans. Severe hypoglycemia is most quickly addressed with intravenous administration of 5–10% dextrose, however, skin sloughing can occur with perivascular leakage of hypertonic solutions. Intraperitoneal administration of 5% dextrose has occasionally been administered when intravenous access is poor in cetaceans. Fluid therapy can also be delivered in a cetacean’s subcutaneous space between the blubber and epaxial muscles cranial to the dorsal fin. Though the space is relatively tight, administration of 2.5% dextrose/0.45% saline for hypoglycemic patients has been performed without obvious ill effect to surrounding tissue. Hypoglycemia can also be managed with oral administration of 10–12% dextrose, though feces should be monitored closely for glucose content and diarrhea development at higher concentrations of dextrose supplementation. Amount of dextrose given is to affect. Regardless of the route of dextrose administration, blood glucose evaluation needs to be performed to assess response to treatment and determine if further supplementation is necessary.
Metabolic acidosis in cetaceans is diagnosed, as in small animal medicine, by evaluating blood gases. In severe cases of metabolic acidosis, intravenous bicarbonate therapy is recommended, but acidosis can also be improved with fluid therapy and oral administration of bicarbonate. Sodium or potassium bicarbonate can be dosed at 1 mEq/kg or 84 mg/kg, divided BID or TID, in a dolphin. Underlying electrolyte imbalances such as hypernatremia should be considered when selecting which form of bicarbonate to use. Arterial or venous blood gases are helpful in assessing response to therapy.
Cetaceans generally have a higher blood sodium level than terrestrial mammals, but levels over 160–165 mEq/L can indicate health abnormalities. Hypernatremia occasionally occurs in ill or anorexic cetaceans and may be associated with ingestion of salt water. When possible, moving the animal to a brackish water environment will help control sodium intake. Subcutaneous administration of 2.5% dextrose/0.45% NaCl has also been attempted to dilute internal sodium levels. Oral administration of freshwater 2–4 times daily by orogastric tube, and injection of thawed food fish with freshwater will also help manage hypernatremia. As in other mammalian species, sudden correction of hypernatremia can result in adverse side effects. Maintenance fluid requirements for cetaceans are generally estimated at 40 ml/kg/day, and additional fluids may be indicated based on an animal’s metabolic or hydration status.1 Caution must be taken with any fluid administration to avoid over hydration and possible pulmonary or neurologic edema development.
Though intravenous access for fluid and drug therapy is possible in cetaceans, other routes of administration provide valuable alternatives when managing metabolic abnormalities such as hypoglycemia, metabolic acidosis, and hypernatremia. With any of these disorders, it is important to closely monitor the patient with blood analysis to determine the effectiveness of therapy and need for further supplementation.
The authors would like to thank Stacy Randall, DVM, DACVIM for her guidance and expertise, and John Kerivan for his support.
1. Walsh, M.T., and S. Gearhart. 2001. Intensive Care. In: CRC Handbook of Marine Mammal Medicine. 2nd Edition. CRC Press, Boca Raton, FL. 691.