Disinfection of tissue is a daily routine for most veterinarians, for instance prior to a surgical procedure or specific orthopedic injection. Knowledge of different disinfecting agents is vital to prevent the occurence of any adverse septic events after a medical procedure.
We all know that iatrogenic infections can cause serious consequences for the patient and the client-veterinarian relationship.
Antiseptics are distinguished from disinfectants by the fact that the latter are being used to kill micro-organisms on non-living objects.
One of the most commonly used antiseptic in veterinary practice is of course alcohol. It is important to mention that alcohols are only effective against vegetative bacteria, and poorly effective against spores, fungi and viruses. Their bactericidal action is based on protein denaturation. Alcohols have a defatting effect, but their action is inactivated by organic debris and there is no residual effect after evaporation. Their bactericidal action occurs very quickly after application, and this kill rate is higher and faster then for instance chlorhexidine or povidone-iodine. Alcohol can also be used to rinse the surgical scrub from the surgical site. Alcohols (isopropyl alcohol excepted) have no adverse effects on the action of chlorhexidine.
Chlorhexidine solutions have a rapid onset of action as well as a persistent effect. This latter is caused by binding to proteins on the stratum corneum. This way it remains in the surrounding, which is beneficial if bacteria reside in sweat glands, sebaceous glands, and hair follicles.
Chlorhexidine solutions show invariable results against viruses and fungi. It has low toxicity as a skin scrub, or as an aqueous solution for wound disinfection, oral lavage, and mucous membranes of the urinary tract.
The antiseptic agents with probably the broadest antimicrobial spectrium are inorganic or elemental iodine solutions. Their kill time is rather short as well (even at lower concentrations ), and micro-organisms are not able to develop resistance to it. Iodine solutions are available as complexes of elemental iodine with a carrier, like eg. podivone-iodine. Iodine is able to cause skin irritation -and staining, but these complexes are able to reduce the amount of skin irritation -and staining.
Povidone-iodine solutions are often available as a 10% solution, containing 1% of available iodine but with only a very low amount of free (and bactericidal active) iodine. Therefore the bactericidal activity of this solution is normally very low. By diluting this solution with water, the amount of free iodine is increased, as well as its bactericidal activity. Scrubbing this solution causes an increase of free iodine, thereby enhancing the bactericidal effect of the povidone-iodine application. After 2 minutes of scrubbing enough free iodine is released to achieve proper disinfection.
Clipping of hair and cleaning of the skin enhances the effectivity of iodine solutions, because this reduces inactivation by organic debris. Nevertheless studies on arthrocentesis models (carpal joint and coffin joint were used in a study) have shown that a 5-minute surgical scrub with povidone-iodine of non-clipped skin and a subsequent rinse with 70% alcohol was as effective as the same regimen on clipped skin. Therefore clipping the skin is not always a necessary procedure for certain joint injections.