25 March 2009

Ten tips for avoiding hospital infections

ScientificAmerican.com (disclosure: I have written a story for them, and it is edited by a friend) has a great interview with a hospital epidemiologist about things to do to avoid hospital infections.

It's a smart list, with some non-obvious things on it. For instance:
5. Make sure you're kept warm
The air temperature in operating rooms typically hovers between 65 and 69 degrees Fahrenheit (18 and 20 degrees Celsius). That's great for the doctors and nurses bundled head to toe in scrubs, but not necessarily for the person on the table. [Stephen Streed, an epidemiologist who oversees infection control at the Lee Memorial Health System in Fort Myers, Fla.] says that the body responds to chilly air by constricting vessels supplying blood to the skin and the tissues just below it; diverting blood away from the body's surface and toward its core is the body's strategy for conserving heat. With less blood supplying oxygen to the incision site, the immune cells there become oxygen-deprived and therefore less effective at battling invading germs. Ask the surgical team how they intend to keep you warm -- if they will crank up the room temperature by a few degrees, cover you in blankets, or warm you with IV fluids, for instance.

6. Ask about presurgery antibiotics
For many operations, including those involving the heart and bone, doctors routinely give patients preventive antibiotics to nip infections in the bud. One dose is typically given via IV an hour before the surgeons make the first cut, and sometimes two more doses are given over the next 24 hours, Streed says. If you think there is any possibility that you have an infection before going into surgery, tell your doctor so that he or she can treat you first. (Having an existing infection in, say, the bladder or skin ups the risk of developing a second, surgery-related infection, Streed warns.)
The whole list is worth reading.

1 comment:

daedalus2u said...

I don't disagree about keeping warm, I do disagree about the mechanism. Immune cells are attracted to specific sites by various signaling molecules, and these signaling molecules (including NO) are increased by local high temperatures. Increased temperature is a generic response to counter infection observed by essentially all animals, even cold blooded ones, even insects. The higher temperatures also signal immune cells to "do their thing" once they reach the warmer site.

The external few hundred microns of skin doesn't get O2 from blood, it gets it from the external air. When there is an incision, the cut parts will be exposed to air at 21% oxygen, which is higher than what they get from blood in vivo. Most immune cells operate via glycolysis which doesn't require O2. They do that because they generate lots of NO which interferes with mitochondrial consumption of O2. Also immune cells need to operate in places with insufficient circulation, so their metabolism needs to be (somewhat) O2 independent but O2 is important in generation of superoxide, hydrogen peroxide and NO. There are hypoxic mechanisms for NO generation involving nitrite and nitrate.

I would add eat a lot of lettuce (to get your nitrate/NOx level up). There is some thought that eating a lot of nitrate can suppress UTIs.


A more important mechanism that is not mentioned here is that nitrite and NO cause biofilms to disperse or not form. Forming a biofilm is one of the major virulence factors for most bacteria, including MRSA and Pseudomonas both of which have their biofilms disrupted by NO/nitrite.