![]() Blood gas analysis and serum lactate measurements may be used to assess severity and metabolic consequences of the anemia. 129,181 Serum biochemistry and urinalysis should be performed to monitor liver and kidney function. 129,179 Measured blood methemoglobin concentration is increased in cases with maple leaf toxicity and can exceed 50% of total cellular hemoglobin concentration (normal methemoglobin fraction is less than 2% of total hemoglobin). Heinz bodies and eccentrocytes can be detected on blood smears ( Fig. Moderate to severe anemia, hyperbilirubinemia, hemoglobinemia, and hemoglobinuria are present. Brown discoloration of the mucous membranes, blood, and urine indicate methemoglobinuria, commonly found with maple leaf toxicity ( Fig. Tachycardia, tachypnea and icterus are common findings. Horses usually present with weakness, depression, anorexia, exercise intolerance, and signs of hematuria. Recognition History and presenting complaintĬlinical signs vary depending on type and amount of toxin, time since exposure, and occurrence of complicating factors like pigment nephropathy and acute renal failure. Prognosis with rapid developing severe anemia is poor. Maple leaf toxicity also leads to methemoglobinemia and brown discoloration of mucous membranes, urine, and blood. ![]() Oxidative damage to erythrocytes leads to hemolytic anemia characterized by the presence of Heinz bodies and eccentrocytes on the blood smear. Heinz body anemia results from toxic effects of maple leaves, wild onions, phenothiazines, or methylene blue. Prevention of the disease is accomplished by preventing exposure of horses to dried maple leaves. 94 Treatment with dexamethasone was associated with increased risk of death in one study. Whether dexamethasone increases the risk of laminitis in affected horses is unknown, and the efficacy of ascorbic acid is questionable. Other symptomatic therapies that have been suggested include nasogastric intubation with activated charcoal to aid in potentially binding to the toxin(s) dexamethasone to aid in stabilizing red blood cell membranes and decrease phagocytosis of damaged red blood cells and ascorbic acid (30 mg/kg) given in intravenous fluids twice daily, which may reduce oxidative damage to red blood cells. Acute renal failure should be treated appropriately if it develops. Blood electrolyte and acid-base parameters should be monitored and abnormalities corrected as needed. Oxygen therapy may be beneficial in selected cases, and blood transfusions can be administered to severely affected individuals.īalanced fluid administration is important to maintain renal function and to aid in diuresis because affected horses may be at great risk of developing hemoglobin nephrosis and acute renal failure. Exposure to red maple leaves should be eliminated immediately, and affected horses should be kept in a quiet, calm environment. Treatment of affected horses is primarily symptomatic. 92 Urinalysis may indicate varying degrees of hemoglobinuria, hematuria, bilirubinuria, and proteinuria. 89-92 Transient hypercalcemia has been recorded in some horses, 89 and increases in BUN and creatinine concentrations are expected in horses undergoing significant renal insult secondary to hemolysis. Blood chemistry analysis may reveal depletion of erythrocyte-reduced glutathione and increased serum concentrations of LDH, creatine phosphokinase, AST, and sorbitol dehydrogenase. Hematologic abnormalities noted in affected horses include moderate to severe anemia (PCV often less than 10% in severely affected horses), hemoglobinemia, methemoglobinemia, Heinz bodies, anisocytosis, hyperbilirubinemia, and increased erythrocyte fragility. ![]() The typical clinical signs and conditions supporting maple leaf intoxication should be in evidence before making a diagnosis. Maple leaf toxicosis occurs under rather specific conditions but is characterized by an acute onset of hemolytic anemia with methemoglobinemia and Heinz body production. Patricia Talcott, in Equine Internal Medicine (Fourth Edition), 2018 Diagnosis and Treatment
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