Iodine vs. Chlorhexidine skin prep

OK it isn’t the biggest or sexiest decision you might make on any day of the working week – but one where there is in fact some evidence.  Betadine  vs. Chlorhexidine – not really a hot debate.  Boring EM at best.

Are you making incisions in patients, or are you doing skin lac repairs?  I know that when I prep a surgical field I usually reach for the closest bottle of prep solution without giving it a moments thought.  But thanks to some ‘bottom-up’ education from local RMO, Dr Garg I have decided to be a Chlorhexidine in alcohol guy.

Why is this?  Well there are a few studies which he has pointed out to me which make a pretty convincing case for chlorhex over iodine – in terms of post-op wound infections it seems to be a winner.

Read them here:

Skin prep – NEJM 2010 (Chlorhex alcohol is better than povidone-iodine)

NYU skin prep review

Now – a very astute reader (my wife) noted that the studies here are done with 2% chlorhex – however in Australia we tend to stock 0.5% Chlorhex in alcohol.  So let me know if you are aware of any data on the weaker solutions.  Are they still as good? Or can we translate these studies to Oz?

The aqueous vs. alcohol decision is easy in my shop as we don’t keep aqueous as standard on the trolley – however it seems that isopropyl alcohol solutions work fast – i.e. as they evaporate and dessicate the bugs over 1 – 2 minutes they have done their work.

Now – a few practical caveats to the idea that chlorhex in alcohol is all round great.

  1. You cannot use the strong isopropyl alcohol solutions directly onto mucosa (e.g. vaginal, mouth, or anywhere near the eyes)
  2. The alcohol-based solutions are flammable – but only if you don’t let them dry or let them pool in places e.g. umbilicus and then ignite them, with say, diathermy.  SO be aware of this – they need to dry to work properly anyway so – don’t leave it wet.
  3. Chlorhex in alcohol is neurotoxic…. in theory. (see this study from the Mayo in Amer Soc of Regional Anaesthesia).  It seems to be a rare event in spinal anaesthesia, but I think we should avoid it in areas where we are exposing nerves in ED – eg exploring deep lacerations.

My last learning point for you – I have been trying to teach this to my local RMOs for a while – if you have a contaminated wound and you want to flush out bits of the earth etc – then use large volumes of saline or other cheap and isotonic solution.  Using antiseptic solutions in this setting is just wrong – no benefit, and you are not going to use the volume that is required.  So wash out with lots of salty water, then worry about prep later.

Let me know – does this change the way you prep your patients?


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  1. Pertaining to your last point, is there a particular reason you endorse using an isotonic solution for irrigation? Multiple studies have been done looking at the use of tap water for large volume wound irrigation and most of the ones I’ve seen have shown no difference in infection rate when compared to sterile NS(e.g. To me it seems like a bucket of tap water, a 60mL syringe, and an 18G angiocath or sprash-guard should make quick and cheap work of any wounds that need cleansing.

    Then again, at our shop most folks are either hesitant to crack open anything larger than our tiny 100 mL sterile bottles for irrigation, but they also don’t want to use tap water, so I suspect a lot of wounds go under-irrigated.

    • Hi Vince
      No -- no evidence for saline over tap water. I think if you use a lot of volume it does make the tissues a bit soft / wrinkly like when you stay in the pool too long.
      That can make sewing i back a bit tougher. No evidence just an ideal.
      I like to get a liter or two of whatever IV fluid we have and put it on a pressure bag then you can use it to hose out the wound over a bucket, a soft catheter tip helps get into the cracks.
      Might be criticized for using a tap water where I work as we have a lot of bugs that love the tropical temps and thrive in water.

      • Thanks for the reply.
        Good thought about the tropical bugs -- it’s not a worry here in Upstate NY, but I can see where you’re coming from.
        Plus most patients are going to do well regardless, so it’s mostly down to personal preference anyway with such a high NNT. At maybe $2 a bag for a liter of NS, the setup you describe is probably worth the price for the peace of mind that you won’t get blamed for causing an infection. Plus it’s cheaper than a liter of saline in one of those plastic bottles, which seem to run around $6 a pop and are impossible to find in our department most days, so triple-win for the pressure-infusion irrigator.

      • The old saying goes…the solution to pollution is dilution! Pretty much any fluid (so long as it is clean and non-toxic) will do. Water and normal saline are cheap. The days of hydrogen peroxide are long gone due to the risk of injury to surrounding tissues.

        I have used chlorhex/alcohol as my only prep for blocks and lines for several years, since reading that it was up to seven times more effective than betadine. It is also not sticky like betadine which makes for a better working environment. HOWEVER it must be allowed to dry (the alcohol evaporation is key to its effect I believe) and caution used when prepping for regional blocks. It is frightening how many have had it injected into their nervous system. We follow the KEMH standard of using the “red” tinted solution and not allowing it to be put anywhere near nor on the epidural trolley. I have heard of some people using a common-or-garden spray bottle to apply it to the skin before a procedure…anyone else seen or heard of this?!

        • Hi Airell
          Yes the Anaesthetists are somewhat paranoid about chlorhex anywhere near the catheter that is going into the epidural space. I think this is fair enough -- it costs nothing to be a little bit extra careful. I think the 3 minute dry-time is crucial -- as it means the solution is not running everywhere as you work, and it kills the bugs as it evaporates.
          My practice is to prep the skin then spend 3 minutes getting my kit ready / drawing up, then cracking on once the skin is dry. That way the solution and the kit are never on the cart together at the same time.

          Ah, the old days -- we used to squirt peroxide all through various cavities. I heard it caused a few air emboli and was hence banned.

          Another amusing anecdote: I was once doing an epidural with a strange (to me) midwife at 3 AM and as she poured the prep into the dish it smelled of a fish ‘n chips shop. What was going on? She had inadvertently picked up a bottle of 3% acetic acid from the store room. DOH! That would surely be a bad thing to prep with! Caught that one luckily!

  2. Casey
    From a pharmacist point of view…

    For most minor things at our hospital, chlorhexidine is winning hands down. Iodine remains the
    agent of choice in theatre though (at least looking at the usage!)

    We do have the 2% alcoholic solution (tinted pink, ours is in 70% ethanol, although there is an isporopyl version available, although significantly more expensive) and use it in preference for high-risk procedures (central lines, fistula cannulation especially).

    My personal opinion is that chlorhexidine in alcohol is a good first-line option. Reasons to use iodine instead would be:
    - if there is a need to be able to clearly see the area that has been decontaminated
    - broken skin or mucous membrane
    - plan for use of heat/ignition source (e.g. diathermy)
    - chlorhexidine allergy -- becoming more common with every passing year. Have seen one anaphylactic shock-->arrest due to this, and our urologist was so suspicious of the number of periop hypotensive episodes he was seeing (at the point of catheterisation) he organised a whole-of-hospital change to chlorhex-free catheterisation gel.
    - concern about non-bacterial pathogens (unlikely in most circumstances, but worth being aware of)


  3. There is unfortunately a lot of misinterpretation going on in the literature in that area. Many authors and articles simply ignore the role of alcohols in skin antiseptics by regarding the alcohol as if it were a solvent or carrier substance for the chlorhexidine (“chlorhexidine in alcohol”). The above comparison — also the one in the Darouiche 2010 NEJM paper — is NOT a comparison of chlorhexidine vs. iodine. It is actually a comparison of chlorhexidine plus alcohol (i.e. 2 antiseptics) vs. povidone-iodine alone (i.e. one antiseptic). On microbiological grounds, the alcohol is about 10 times stronger than either chlorhexidine or podidone-iodine alone. So there is no scientifically tenable reason to assume that the beneficial effect of the chlorhexidine-alcohol combination should be solely due to chlorhexidine (which is what many authors/articles assume). The comparison of chlorhexidine plus alcohol vs. iodine plus alcohol would be much more appropriate. Note that (as correctly pointed out above) alcohol-containing antiseptics are unsuitable for mucous membranes, and aqueous solutions have to be used. We published an article trying to clarify the common chlorhexidine misinterpretation here:

  4. I don’t know if there’s much evidence about cleaning wounds with saline vs water, but there is evidence that water is harsher on tissue and causes some local damage vs saline. This has been shown more for local wound care. Why we irrigate with sterile water if there was gross tumor spillage (doubt there’s any hard evidence for that though)

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