Hypophosphatemia in Dogs
In dogs undergoing insulin treatment for diabetic ketoacidosis or receiving glycolytic refeeding for starvation, there’s a risk of hypophosphatemia. This occurs due to the rapid production of adenosine triphosphate (ATP) as a response to insulin, causing phosphorus to shift from the blood serum into cells. This decrease in serum phosphorus concentration can stem from reduced intestinal absorption or renal reabsorption of phosphorus.
If left untreated, this condition can lead to acute extracellular hypophosphatemia, an electrolyte imbalance. Since phosphorus is crucial for ATP, low serum levels can deplete ATP and affect cells with high energy demands such as red blood cells, skeletal muscle cells, cardiac muscle cells, and brain cells. Hypophosphatemia can also reduce erythrocyte 2,3-DPG, decreasing oxygen delivery to tissues.
Symptoms
Symptoms typically align with the underlying disease causing hypophosphatemia rather than directly correlating with phosphate concentration. These include:
- Hemolytic anemia resulting from severe hypophosphatemia.
- Presence of red or dark-colored urine due to hemoglobinuria stemming from red blood cell breakdown.
- Tachypnea, dyspnea, and anxiety caused by hypoxia.
- Muscle weakness.
- Mental depression.
- Rapid, shallow respirations due to impaired respiratory muscle function.
Causes
- Maldistribution through enteral or total intravenous nutrition.
- Treatment of diabetes mellitus, particularly with carbohydrate loading and insulin administration.
- Respiratory alkalosis, which decreases hydrogen ion concentration in arterial blood plasma.
- Reduced intestinal absorption of phosphorus due to a phosphorus-deficient diet.
- Vitamin D deficiency.
- Use of phosphate-binding agents.
- Malabsorption syndromes that hinder nutrient absorption.
- Decreased renal phosphate reabsorption.
- Undiagnosed or poorly managed diabetes mellitus.
- Prolonged periods of anorexia, starvation, or malnutrition.
- Consumption of phosphate-poor diets or intravenous nutrition solutions.
Diagnosis
Diagnosing hypophosphatemia in your dog involves a comprehensive physical examination by your veterinarian, considering the symptoms you’ve observed and potential underlying conditions. Given the various possible causes, your veterinarian will likely employ a differential diagnosis approach to prioritize treatment. This entails thorough evaluation of outward symptoms, eliminating more common causes until the correct disorder is identified for appropriate treatment. A comprehensive blood profile, comprising a chemical blood profile, complete blood count, and urinalysis, will be conducted as part of the diagnostic process.
Treatment
In cases of severe hypophosphatemia, hospitalization for immediate treatment under the care of your veterinarian is necessary for your dog. If the condition is induced by insulin therapy or intravenous nutrient administration, these treatments will be paused until supplemental phosphate is administered over several hours. If anemia accompanies the condition, fresh whole blood transfusions might be necessary. Conversely, if your dog has a moderate case of hypophosphatemia and its condition remains stable, outpatient treatment may suffice.
Living and Management
To manage your dog’s condition, your veterinarian will monitor its phosphorus levels every 6–12 hours until they stabilize within the normal range. If hyperphosphatemia recurs, all supplementation will cease, and your dog will receive intravenous fluids until phosphorus levels normalize. Follow-up care involves monitoring your dog for acute renal failure, a condition to which some hyperphosphatemic patients are susceptible, and daily monitoring of potassium concentrations until they stabilize as well.