Alcohol kills more bacteria faster than other antimicrobials commonly found in surgical hand antiseptics, yet some question its role as a surgical rub, its antimicrobial longevity and its dermal compatibility. Are these concerns valid? Here's what we found out.
While there are many antiseptic products for preparing hands for surgery, when it comes down to it, you have a choice among just three key antimicrobial ingredients: alcohol, chlorhexidine gluconate (CHG) and iodophors (povidone-iodine, for example), says Elaine Larson, RN, PhD, FAAN, CIC, associate dean and professor of pharmaceutical and therapeutic nursing at Columbia University School of Nursing in New York. Here are the key differences between them.
- Alcohol. Kills bacteria on skin more effectively than any other agent, says the CDC, and it does so rapidly. It's effective against both gram-positive and gram-negative bacteria, Mycobacterium tuberculosis, various fungi and certain enveloped viruses. At higher concentrations (60 to 70 percent ethanol), it becomes even more lethal to bacteria and can kill certain non-enveloped viruses, although viral kill isn't assured because it depends on such factors as temperature, volume of disinfectant and protein load. Alcohol evaporates rapidly and doesn't bind to the skin, so it won't continue to kill bacteria after application. But due to its devastating effect on the bacterial load, microbial regrowth occurs slowly. "Bacterial counts on hands after wearing gloves for one to three hours seldom exceed pre-scrub, or baseline, values," says the CDC's Guideline for Hand Hygiene in Healthcare Settings.
- Chlorhexidine gluconate. CHG kills bacteria more slowly than alcohol, even at a high (4 percent) concentration. It typically takes four to five applications of CHG to produce the same degree of microbial kill as one application of alcohol, says Daryl S. Paulson, PhD, president and CEO of BioScience Laboratories in Bozeman, Mont. CHG's main attribute is its residual effect. Its antimicrobial efficacy strengthens over time with repeat applications because it binds to the skin, where it continues to kill bugs. CHG is more effective against gram-positive than gram-negative bacteria and it has some effect against fungi and tubercle bacilli, says the FDA. It doesn't kill non-enveloped viruses, but it rapidly inactivates lipid-enveloped viruses.
- Iodine/iodophors. Products such as povidone-iodine kill gram-positive and gram-negative bacteria as well as mycobacteria, certain fungi, viruses and protozoa. Not only does the CDC rank iodophors as the least effective antibacterial type of the three, but pH, temperature, exposure time, concentration of total available iodine and emollient concentration all affect their antimicrobial ability. Blood or sputum can rapidly neutralize them. According to research summarized by the CDC, these products don't have persistent activity after wearing gloves for one to four hours. "Iodophors never catch up in terms of antimicrobial efficacy, no matter how long you use them. They have no residual effect and they're not fast-acting," says Ms. Larson. "People continue to use them because they like to see the brown foam froth up. This offers visual reinforcement. There is a lot of emotion attached to this subject."
A matter of persistence
Despite its excellent antimicrobial performance, alcohol's critics remain. Many say it lacks "persistence" because it doesn't bind to the skin and continue to actively kill bacteria after application, like CHG. However, since alcohol kills so much bacteria so fast on a single use, its effect can be long-lasting. Clinically, it's the actual bacterial count on the hands over the course of surgery that matters, not how the product makes it happen.
Viewing it this way, many alcohol-based products are persistent. The key, says Ms. Larson, is ensuring that the alcohol-based product you choose meets the FDA's current "TFM" standards for persistence. Since 1994, the FDA has had a proposed rule in place that outlines a test method for demonstrating persistence. This Tentative Final Monograph (TFM) requires the bacterial load under surgical gloves to stay below the pre-rub level (baseline) for six hours.
You may also want to consider the manufacturer's data, because the antimicrobial efficacy and persistence of one alcohol-based product vs. another will likely vary, even if they're both FDA compliant, depending on the formulation. Some products combine lower concentrations of alcohol with CHG in an effort to keep the antimicrobial action going, while others offer ethanol concentrations as high as 80 percent by volume to provide a more substantial, initial microbial kill. Additives like detergents, emollients, color, fragrances and preservatives can also influence a product's efficacy. "The addition of a preservative to an alcohol formulation may impart sufficient inhibitory properties to an alcohol product to prevent bacterial regrowth," a representative from the FDA's Center for Drug Evaluation and Research reports. "Other ingredients, such as chelating agents added to products to remove ions from solution, may also provide persistence to an alcohol product."
A cumulative question
Another criticism of alcohol is that it doesn't produce a "cumulative" effect. "Cumulative activity" refers to a product's ability to strengthen its antimicrobial power over the course of days, after repeated uses. The FDA's proposed TFM also contains standards for cumulative action; surgical hand antiseptics must demonstrate a 1-log reduction in bacterial counts on day one, a 2-log reduction on day two and a 3-log reduction on day five.
Alcohol doesn't remain active after application, so not all alcohol-based products can fit this bill. But experts say the cumulative effect has no clinical relevance because those who rub or scrub do so before each case anyway, and it's the microbial load during surgery that matters.
"Is it better to slowly build up to a 3-log reduction on day five, or is it better to get a 2.5-log reduction immediately on day one and make it last all the way through for the five days?" asks Dr. Paulson. "Alcohols do this consistently, and it doesn't make any real clinical sense to slowly build up to it. With cumulative products, it's almost as if you should wait until Friday to have surgery."
Even the FDA admits that this requirement is theoretical, and the agency might scratch it before the TFM becomes final. The agency's Nonprescription Drugs Advisory Committee wants to drop it. "NDAC recommended that the agency not require the demonstration of a cumulative antimicrobial effect ' based on the belief that topical antimicrobial products should be effective immediately after one use and that the demonstration of cumulative antiseptic effect is unnecessary," says an FDA spokesperson.
An irritating problem?
The third criticism of alcohol is that it can dry out the skin. Not so, says Ms. Larson, when it's part of a well-formulated waterless rub. While alcohol alone is drying, she says, research shows that alcohol-based waterless rubs with the right combination of emollients and other ingredients can improve skin condition. "It's the opposite of what you might think. Most people who use alcohol products actually report improvements in skin health," she says. "The formulation is more important than the individual ingredients." In its guidelines, the CDC agrees: "In several recent prospective trials, alcohol-based rinses or gels containing emollients caused substantially less skin irritation and dryness than the soaps or antimicrobial detergents tested."
Ms. Larson also points to the application method as a source of irritation, and says this is another reason why waterless alcohol rubs have a leg up when it comes to skin compatibility. The mechanical process of scrubbing with water and the friction of towel drying can greatly increase the risk of skin breakdown when you do it so often.
This is very important, agree experts, since irritant contact dermatitis makes the skin more vulnerable to microbial colonization. It also makes OR personnel less likely to comply with hand antisepsis protocols. When they shortcut the protocol, antimicrobial efficacy can suffer greatly. Ms. Larson says unfounded concern about the drying effects of alcohol has been a "major" cause of poor acceptance of alcohol-based hand rubs in hospitals.
The role of alcohol
All things considered, many experts have concluded that alcohol-based products should play the central role in surgical hand antisepsis. "My recommendation and bias is alcohol, unless you have a reason not to use it," says Ms. Larson.
It's important to acknowledge what waterless alcohol rubs can't do. Whenever hands are soiled, experts call for a more traditional water-aided scrub. Only a water-aided washing can remove dirt, organic material, spores and vegetative cells. The good news: this seems to be what most of you do. According to a recent Outpatient Surgery survey, two-thirds of facilities use a traditional, albeit typically brushless, scrub for the first scrub of the day to eliminate gross contamination carried in from the outside.
Be aware that you can't please everyone all the time. Ms. Larson says it's critical to test a number of alcohol-based antiseptics to select the products that most of your staffers will accept. "People will be most concerned about the aesthetics - how it looks, feels and smells. It could be the most effective product in the world, but if they hate it, they won't use it," she says. "Pilot-test several products and use a questionnaire to assess consistency, color, fragrance, skin tolerability, dryness and residue. And, importantly, have several products available once all is said and done so everyone has a choice. This will help maximize compliance, and help you know you're doing your best to protect patients from surgical site infection."