Patient risk factors
Obesity
You can find out if you are overweight by checking your body mass index (BMI). BMI calculators are freely available on the internet and will give you a score depending on your height, weight and if you are male or female. A BMI of 40 may mean that your operation will take longer and you may need more blood products (transfusions). Both of these factors are associated with a higher risk of infection. Fat also has a poorer blood supply, meaning there is less oxygen and fewer nutrients available to help the wound site heal.
Diabetes mellitus
Too much or too little sugar circulating in the blood can have a negative effect on the cells involved in healing and, in particular, poorly controlled diabetes can weaken your body’s ability to fight infection.
Current or recent smoking
There are many reasons why smoking increases the risk of wound infection, including that smoking reduces the body’s ability to heal and to fight infection. Smoking can lead to an iron imbalance (releasing the body’s stores) and bacteria (which cause infections) thrive on iron.
Emergency surgery
If you have had a heart attack and need surgery immediately, there may not be enough time to prepare you for surgery as there would be for patients having planned surgery. For example, in an emergency you would be unlikely to have a shower with an antibacterial soap before surgery. This may increase your risk of infection. Ideally, after a heart attack the heart would have time to recover before surgery, but this is not always possible. Under these circumstances, you may already be very unwell and your body’s chemical and cellular systems may be unbalanced, which then in turn delays the normal healing process.
Age >65 years
Increased age can increase the risk of wound infection due to the potential combination of increased underlying illness and the decrease in the body’s defence mechanisms.
Long surgery time
Some operations are more complicated and take more time. When this happens, the surgical wound site is exposed to the air for longer and the risk of bacteria in the air getting into the wound increases.
Bilateral mammary arteries (BIMA)
Heart bypass surgery is carried out when the blood vessels that supply blood and nutrients to the heart muscle become blocked. During bypass surgery, healthy blood vessels are moved from other parts of your body to supply blood to your heart muscle instead. These blood vessels are called grafts because the end of the vessel is grafted onto your heart. In most bypass operations, one graft will come from inside your rib cage (a mammary artery) and another from your leg. However, recent studies suggest that using both of your mammary arteries (bilateral mammary arteries) as grafts, has longer lasting benefits, especially in younger patients. The downside is that there is an increased risk of wound infection since some of the blood that would have gone to supply your chest is now going to your heart instead, so there is less blood available to heal your chest wound site.
Pre-existing infection(s)
Infections elsewhere in the body, such as chest infections, water infections (also known as urinary tract infections) or skin infections (also known as cellulitis) increases the risk of introducing the bacteria already present into the new surgical wound.
Female gender
The surgical wound usually runs down the middle of the patient’s chest, with breasts on either side. Breasts contain no muscle and can be very heavy. The weight from each breast can put pressure on the new surgical wound, making it hard for the wound edges to come together and can slow wound healing.
Implants
You may have an implant put inside you as part of your operation. An implant is something that is man-made, like a metal wires to stitch your bones together or an acrylic tube to act as a blood vessel to supply blood to your heart. If we take a blood vessel from your leg or arm and move it into your chest, this is not called an implant because it comes from your own body. Sometimes infections can develop on the surface of implants.
Being cold
Blood vessels carry nutrients and cells around the body that help wound healing and fight infection. If you are cold, the blood supply to your skin decreases. This means there are fewer nutrients and cells available to heal wounds and fight infection. Keep warm before surgery by wearing a clean dressing gown. During the surgery, the staff will put warming blankets on you.
Poor diet
Your body needs vitamins and minerals to heal wounds. If you diet is poor and lacking in fruit and vegetables, you may have reduced levels of the vitamins and minerals needed to heal your wound. A wound that is slow to heal is more likely to become infected.