Medical myth : Give Max with your Morph?

Gday readers.  This post is the result of a recent Twitter discussion involving a group of FOAMites including: @EMManchester, @smotovmd, @EMS_Junkie, @ KangarooBeach, @rfdsdoc, @MDAware, @Darn_if_i_know, @OneArmWonder, @Lyall

I had a very Orthopaedic weekend – footy season is back, lots of minor injuries.  And then the seasonal influx of tourists – means a lot of older folk with less robust skeletal integrity!

So we ending up giving a lot of IV morphine in ED over the weekend – I always like to get it in early, hate to see patients in pain “awaiting Xray”.

Our team got into a bit of a debate around the practice of giving an antiemetic routinely with the first dose of opiate IV to prevent nausea or vomiting.  The “standard” seems to be an order for Maxolon [metoclopramide] to go with a dose of morphine.  Now – this is something I have seen go in and out of fashion many times over the last 15 years.  In fact I have a vague recollection that this may have been the first thing I ever prescribed as a doctor – at the request of a very stern senior nurse.

So last Saturday I was bemused to be once again “requested to chart” some Max to go with the morphine I had just prescribed.  I declined.  I recall reading papers over the years that suggest it just isn’t as effective as the logic would suggest.  This is classical “physiology or pharmacology-based medicine” i.e. PBM.  Drug X treats symptom Y so if you want to fix symptom Y – then give drug X.  However, as we know – things are not always what they seem – sometimes things just don’t pan out like the basic sciences might suggest.  So is that dose of anti-emetic really doing what you hope?

So I asked the Twitter crew – what is the evidence, how do the FOAMy docs prescribe their opiates – and I managed to get a really great batch of opinions and papers.

Lets start with the best evidence out there that can answer this question: does  giving prophylactic anti-emetic medication have a benefit for patients receiving parenteral opiates in the ED?

There is a “Best Bet” from the UK which included 3 papers – in summary – they showed no benefit and a non-significant trend towards increased vomiting and other medication side-effects in the groups receiving metoclopramide.

In June 2011 the journal Emergency Medicine Australasia [free full text] published a review article that looked at the same papers as well as some others looking into side effects.  Same conclusion – low incidence of vomiting, no benefit, possible harms.

So there is not a huge body of evidence  -but it certainly does not support the routine use of metoclopramide  in the ED for patients requiring IV opiates.

So I do not do this routinely.  In fact the low incidence of vomiting after opiates makes me worry that a vomiting patient may actually be suffering from another, non-opiate related  problem.

For example –

• young, fit trauma patients with evolving hypovolemia / shock often vomit despite no overt signs of shock – they need an operation or blood – not Maxolon!
• the actual pain itself commonly provokes a profound vagally-mediated reflex with bradycardia and vomiting.  Treating the pain, e.g. splinting the fracture will fix this.   Max will not.
• Vomiting plus abdo pain – sure they might need opiates – but just be aware they may have an obstructive problem – so you really need to think about that before giving a prokinetic agent

On one final note – as a GP-anaesthetist I frequently give multiple anti-emetics in the context of operative analgesia to prevent nausea and vomiting.  There is a large body of evidence to support this practice

I think that this is reasonable – if you anticipate that your patient will require ongoing parenteral opiates for their problems – then using a longer-acting antiemetic agent will likely be beneficial.  However, if you really want to maximise the benefit: risk ratio – then you could ask a few extra history questions to try and identify patients who might be prone to opiate-induced vomiting.

• History of postoperative nausea and vomiting with previous procedures
• History of motion sickness
• Women are more prone to vomiting than men

OK – bottom lines :  

1. Just say “NO” to prophylactic anti emetics.  
2. Consider other causes of vomiting in the context of the patient’s problems.  
3. Try and risk-stratify your patient and use longer-acting agents if you really want to prevent nausea associated with opiates.

Casey