Ischaemia and reperfusion injury: when cells almost die

Ischaemia is defined as inadequate blood supply to a part of the body, usually caused by partial or total blockage of an artery. Reperfusion injury occurs when tissue perfusion and oxygenation are restored to an affected area after an ischaemic event.

Ischaemia/reperfusion (I/R) injury is a complex cascade of events resulting in devastating effects to the body, sometimes including death. Despite more than 70 years of research, I/R injury is not fully understood. Events such as gastric dilatation-volvulus (GDV) (Figure 1), mesenteric torsion, or where circulation of the limb is cut off (Figure 2) (e.g. rubber band around paw) all lead to I/R injury. It is important for all veterinary personnel to understand I/R injury so treatment and prevention can begin as early as possible.

The chain of events involved in I/R injury can be broken down into the ischaemic cascade (Box 1) and reperfusion injury (Box 2) An ischaemic episode involves a series of events called the ischaemic cascade. Within 5 minutes of the development of ischaemia, the electrolyte balance within cells becomes disturbed (Grace and Mathie, 1999). The ischaemic cascade usually continues for 2 or 3 hours, but can last for days, even after perfusion is restored to the affected area (Sege, 2006). The term cascade suggests that events follow a sequential pattern, which is not true of the ischaemic cascade. Events can occur simultaneously and do not always occur in a linear pattern (Grace and Mathie, 1999).