Poisons affecting the blood

Abstract

Blood circulates as a liquid containing cells and numerous chemicals; it functions to transport nutrients, chemicals, oxygen and waste products to and from cells, and is involved in defence and wound repair to tissues. Numerous toxic substances can disrupt the normal function of the blood through various mechanisms resulting in clinical signs of poisoning. Some of the substances that commonly cause adverse effects on the blood in companion animals are described. These include onions and related food plants which cause oxidative damage to red blood cells and the formation of Heinz bodies, and zinc which causes haemolytic anaemia. Haemoglobin is also subject to oxidative damage from paracetamol metabolites resulting in the formation of methaemoglobin which is non-functioning, resulting in tissue hypoxia. Disruption of the clotting cascade by anticoagulant rodenticides results in delayed-onset haemorrhage and the drug 5-fluorouracil disrupts the formation of blood cells causing bone marrow depression.