• 21 Nov 2017
  • 11 min
  • 21 Nov 2017
  • 11 min

Dhineli Perera interviews Dr Trisha Peel about prophylactic antibiotics for surgical procedures and when they should and should not be used. Read the full article in Australian Prescriber.


Welcome to the Australian Prescriber Podcast. Australian Prescriber, independent, peer-reviewed and free.

I'm Dhineli Perera, your host for this episode, and it’s a pleasure to be speaking to Dr Trisha Peel. Trisha is an infectious diseases antimicrobial stewardship physician at Alfred Health. Trish's team writes about the quality of surgical antimicrobial prophylaxis prescribing in Australia in the December edition of Australian Prescriber. Trisha, welcome to the program.

Thanks Dhineli and thanks very much for the opportunity to talk to you today.

Can you start by telling us what surgical antimicrobial prophylaxis is, and why it has become such a focus area?

So we know in Australia that over 2 million Australians will undergo some form of surgical procedure each year, and every time you have surgery there's always a risk that you may get an infection of the wound afterwards. It's pretty uncommon so it's usually less than five people in 100, and most of the time patients will experience a bit of redness of the wound or discharge or pus. Most the time it settles on its own. So we have lots of strategies to prevent these infections including simple things like the patient having a shower before the surgery. In certain procedures, however, we know that we should be giving antibiotics at the time of surgery to prevent these infections, and that's called antibiotic prophylaxis, but it's not indicated for all procedures. It's only indicated for procedures where there's an increased risk of infection. The reason why it's become a big focus area is we know that antibiotic prophylaxis is the major reason for use of antibiotics on any given day in the hospital with up to 15% of patients receiving antibiotics, and unfortunately it also has the dubious honour of being the leading reason for inappropriate use of antibiotics in the hospital.

Leading from there what were the main findings from the 2016 surgical national antimicrobial prescribing survey?

We looked at antibiotics given around the procedure and also postoperatively. Unfortunately what we found is at the time of surgery only about 46% of antibiotics given were actually compliant with the Therapeutic Guidelines. And the most common reason was incorrect timing of those antibiotics. When we looked at antibiotics after surgery it was even more concerning. We found that only 18% of the prescriptions were actually compliant with Therapeutic Guidelines.

So your article highlights six key elements to be considered for appropriate prophylaxis, that is the correct indication, antimicrobial, dose, route, timing of administration and duration. Can you tell us Trisha a bit about the surgical procedures where prophylaxis is indicated?

Not all procedures need to have surgical prophylaxis. That's not to say that those procedures don't have any risk of infection. We know they do, but we only use prophylaxis when we know that there are significant risks of infections or significant consequences of infection. So for example in patients who are having operations on their bowel, the risk of infection is actually up to 10–20% so we give prophylaxis then. We also know that patients undergoing joint replacement surgery or valve replacement surgery into their heart, we know that those sort of infections whilst uncommon have significant consequences for the patients, so in that situation as well we give prophylaxis.

And so what are some typical surgical indications for which antimicrobial prophylaxis is prescribed but not indicated? I guess you'd have quite a few good examples from the survey.

Common things that we see and perhaps that are relevant to the GP setting as well is patients who are having minor procedures such as removal of their skin cancers. In most patients undergoing those sort of simple operations they don't require surgical prophylaxis. But we frequently see it being given, but also being given as prophylaxis after the procedure. So that's, you know, one of the common things. I guess any procedure which we would call a clean procedure, that is a simple operation through clean skin, they don't usually need prophylaxis.

And so in the hospital setting, what would be some of those clean procedures?

So for example some of the plastic surgery procedures, again skin flaps and so on. Sometimes when people are having simple procedures on their urinary tract, for example a cystoscopy where they insert a little tube into the bladder and simply have a look. Other examples include laparoscopic surgery, for example if they're having a removal of the gallbladder without any risk factors.

The choice of antimicrobial is obviously multifactorial. Can you tell us what the key determinants are in making the right choice?

Whenever we're doing this we think about what sorts of bacteria are likely to cause the infection, and for many procedures it's the organisms on the skin that are the likely culprits. But if patients are having operations on their bowel then we think about the anaerobic organisms and potentially gram-negatives that may cause infection. So we want to choose an antibiotic that has an appropriate spectrum and as narrow a spectrum as possible to cover those potential organisms. So whilst a skin infection might be covered by something like meropenem, that's a very broad antibiotic when it can be covered by something like cefazolin instead and that's a far more appropriate choice. The other thing we think about is the toxicity. We're giving it as prophylaxis so we don't want to cause patient harm by giving them an antibiotic that might actually result in adverse events for that patient, for example allergic reactions to the antibiotics. And the final thing, we live in the real world and we always have to think in a resource-limited setting about the cost, and as long as it fulfils the other two criteria we will then go for the lower cost antibiotic. So for the majority of surgeries actually cefazolin is the mainstay of a surgical prophylaxis because it covers the likely organisms, it's well tolerated, and it's not a costly antibiotic.

So it ticks all the boxes.

It ticks all the boxes, yes.

Okay, so what about doses of antimicrobials? Does one size fit all when it comes to surgical antimicrobial prophylaxis?

No, one size doesn't fit all. Like everything else 2 g dose of cefazolin is usually reasonable for all patients. Of course you have to adjust the dose for children but in adults 2 g is reasonable. There's a question now, particularly as we are seeing more and more overweight patients undergoing surgery, the question is should we be increasing the dose in patients who are greater than 120 kg and should we be increasing it to for example 3 g of cefazolin. We don't know whether that's truly the best thing or not. There's not a lot of evidence to necessarily say we should be doing that but again a lot of people are moving to that because it's a well-tolerated antibiotic and we think theoretically it's probably better to have that higher dose

And when it comes to the route of administration it seems as though the main debate’s around use of topical antimicrobials and their setting. Can you tell us about these controversies?

The best route for antimicrobial prophylaxis is intravenous. But we have been seeing some increase in use of topical antimicrobials, and the reason why we were concerned about that is there's very limited data to support that it actually has any efficacy over and above the intravenous prophylaxis that's given at the same time. We also don't know what the adverse complications are from administering via that route, and also we’re always worried about using antibiotics when we don't need to and what the impact of emergence of resistance will potentially be.

What would be the current recommendation for timing a prophylaxis?

Yes so there's been a number of trials looking at the optimal timing and there was a recent meta-analysis done by the WHO and from their data they suggested that antimicrobial prophylaxis should be given within 120 minutes of skin incision but they think for short-acting antibiotics such as cefazolin it really should be given within 60 minutes of incision.

And finally the duration of antimicrobial prophylaxis is often a point of contention within or between surgeons. What is the current recommended duration, and what's the big deal if it's continued a bit longer?

One of the things we know is that surgeons want the best possible outcome for their patients and they are very concerned about the risk of infection. And often there's a preconceived idea that perhaps if you give prophylaxis for longer, you have a lower risk of infection, but that hasn't been borne out in a lot of randomised controlled trials and good clinical data. We know that for the vast majority of procedures a single dose prophylaxis at the time of the operation is all that people need to prevent surgical site infections. The other thing is we know that if you give people prophylaxis for a long period of time they actually have an increased risk of infection, so they have an increased risk of Clostridium difficile but we know that they actually have an increased risk of surgical site infections due to more resistant organisms. So you may be trying to prevent an infection but in fact firstly you're actually increasing your risk.

Right. Okay, well that's interesting. I wonder if anyone's really aware that it's actually increasing the risks in some cases.

Yeah and that's part of the work that we're doing through the National Centre for Antimicrobial Stewardship is working with our surgeons and working with anaesthetic colleagues, working with theatre nurses and staff on the ward to actually educate them. A lot of people are unaware of that data and our role is really to help advocate for both the patient but also to work with the rest of our colleagues to try and support them and make sure that we're practicing good evidence-based medicine.

Fantastic, well that's unfortunately all the time we've got for this episode. Thank you for joining us today Trisha.

Thank you very much again for having me.


Dr Peel’s full article is available online at nps.org.au/australian-prescriber and like our whole journal it's free. Subscribe to get the latest Australian Prescriber delivered straight to your email inbox and follow us on twitter @AustPrescriber to get the latest updates. The views of the hosts and guests on the podcast are their own and may not represent Australian Prescriber or NPS MedicineWise. I’m Dhineli Perera and thanks for joining us on the Australian Prescriber Podcast.