During CABG, a section of a blood vessel (the superficial vein) from the leg and/or inner chest wall artery is grafted to the coronary artery to bypass the blocked or severely narrowed section of the coronary artery to improve the blood supply to the heart muscle.
CABG wound site infections remain a challenge to healthcare institutions that provide this surgical service. This is mainly because patients undergoing the procedure almost always have other risk factors that increase the risk of poor wound healing and infection. Among them are age (>50 years) and underlying medical conditions like diabetes mellitus, hypertension, obesity, and a smoking history.
In NUH, CABG patients are followed-up within 30 days of operation. There are essentially two surgical wound sites; the chest and the leg/donor site.
A total of 2433 CABG procedures were performed in NUH from 2005 to 2011. Over the years, leg/donor SSIs were observed more commonly than chest SSIs. Although our overall rates are not yet as good as those reported in the U.S. Network, the SSI rate has been in consistent decline from 2005 to 2011.
The breakdown of rates by sites is shown in Figure 1 below.
Figure 1: CABG Infections by Site at 30 days follow-up (2005 to 2011)
NOTE: Denominators for the above rates are as follows: 2005=300; 2006=383; 2007=394; 2008=321; 2009=324; 2010=361; 2011=350.
Data source: Infection Control, NUH
Our increased overall SSI rates are partly attributable to the high leg/donor SSI rates. International rates show a similar trend, that is, leg/donor SSIs being more common than chest SSIs. Studies have described several independent risk factors that contribute to this high incidence rate. Among them are obesity, older age (>75 years), history of stroke, wound depth and length, and post-operative transfusion of 5 units or more of red blood cells. Identification of risk factors is thus important in preparing a patient for CABG. Humid weather also increases wound infection rates.
The following measures are also being taken in NUH to reduce SSIs:
- Appropriate use of prophylactic antibiotics.
- Appropriate hair removal. Shaving produces nicks in the skin, making it to be a potential ‘nidus’ or breeding place for bacteria.
- Maintenance of normal blood glucose before and after the procedure. Elevated blood sugar levels compromise the body’s white cells’ ability to fight infection.
- Prevention of peri-operative hypothermia also reduces the risk of complications. Maintaining normothermia increases blood circulation, bringing the white blood cells to the compromised area to fight infection.
The hospital strives to unremittingly find possible problem areas that may reduce CABG infection rates, which is in keeping with our hospital’s policy of continuous quality improvement.
- Edwards, JR, et al, “National Healthcare Safety Network (NHSN) Report, data summary for 2006 through 2007, issued November 2008”, Am J of Infectious Control, Vol. 36, No. 9, http://www.cdc.gov/nhsn/PDFs/dataStat/2008NHSNReport.pdf, accessed on 9 November 2009
- Olsen, MA, et al, “Risk Factors for Leg Harvest Surgical Site Infections after Coronary Artery Bypass Graft Surgery”, J Thorac Cardiovasc Sur, 2003, 126: 992-999,http://jtcs.ctsnetjournals.org/cgi/reprint/126/4/992 accessed on 18 November 2009
- Healthcare-associated Infection in England, 2008-2009 Report, August 2009, http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1252326222452, accessed on 23 November 2009
- NUH Hospital Administrative Policy on Surgical Wounds, NUH-HAP-INF-002
- NUH Hospital Administrative Policy on Pre-operative hair Removal, NUH-HAP-INF-003