Perioperative hypothermia and surgical site infections part 1

Surgical site infections (SSIs) account for 16% of nosocomial infections in humans and although there is currently no official surveillance system available in the veterinary industry it is thought that SSIs account for 0.8–18.1% of surgical complications in small animal species (Nelson, 2011). SSIs have many disadvantages such as client dissatisfaction, increased hospitalisation costs, revision surgeries and even patient morbidity all of which increase workload for clinical staff.

SSIs are infections that occur in a wound created by an invasive surgical procedure and can be classed as ‘superficial incisional’, ‘deep incisional’ (Figure 1) and ‘organ/space’ (Mangram et al, 1999). The first line of defense by a surgical wound against both endogenous and exogenous pathogens is oxidative killing of such pathogens by neutrophils, which as the name of the process suggests, requires a good oxygen supply (Paulikas, 2008). When a patient becomes hypothermic they experience peripheral vasoconstriction, the implication of this is that the blood flow is compromised thus decreasing the rate of oxygen transport to a surgical wound. It is within this blood flow that neutrophils and other immune substances are normally delivered to help with wound healing (Kirkbride and Buggy, 2003). Perioperative hypothermia is also known to decrease numbers of leukocytes and cytokines (Forbes et al, 2009). Leukocytes are white blood cells and the body's defence system against infection, and cytokines aim to decrease inflammation and promote wound healing (Dinarello, 2000). Kurz et al (1996) also found that there were more collagen deposits near the wounds in patients who remained normothermic throughout their surgery. Collagen deposits rely on a well oxygenated environment and provide wounds with much of their strength (O'Dwyer, 2007).