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MONA – Has it Gone from Teaching? A Reflection on the Evidence.

What?

MONA (Morphine, Oxygen, Nitrates, Aspirin), has been a long-taught concept for ACS management (Kline, Conti, and Winchester, 2015). Though listed in reverse order and not summarised by an acronym, the same treatment list remains in Resuscitation Council ILS course slide content, and each one has ‘if required’ written in brackets – a key point when two out of four treatments have contra-indications and one is a feature of at least variable evidence. Throughout my development as an ALS instructor, I have learned to encourage giving oxygen early in a patient assessment, before reliable saturations can be gained, or ideally Pac02 readings because this can prevent early deterioration of unwell patients. There are often candidates who have heard of MONA before, or recall treatments in that order – yet I have also come across people who adamantly refuse to teach it because they disagree with oxygen being so heavily emphasised. Is MONA no longer advised – despite each element of MONA still being given? Are we to tell those familiar with the acronym that it is old news and outdated practice? I have looked into the research in order to understand this better. Is MONA still applicable?

So What?

The key focus here is on oxygen. The DETO2X-AMI clinical trial results found no reduction of mortality from oxygen delivery to ACS patients who are not hypoxic (Hofmann et al, 2017). This was a large study in Sweden, which looked at over 6,000 patients whose oxygen saturations were 90% or higher. According to the same primary author and James (2018), in another article, the same has been found for stroke patients and:

‘The oxygen saturation level below which oxygen treatment is recommended was already lowered to 90% in the 2017 European Society of Cardiology guidelines for patients with ST-elevation MI.’

The authors voice the potential for risks of oxygen delivery to this group of patients – Hyperoxia ‘may cause detrimental effects because of vasoconstriction of the vasculature and generation of reactive oxygen species potentially contributing to reperfusion injury’ and they refer to a small Australian study that demonstrated ‘increased early myocardial injury and a larger myocardial infarct size’ in patients who were given oxygen (Stub et al, 2015, in Hoffman and James, 2018). I believe this is where the anti-MONA rhetoric I have experienced in professional practice has come from. However, a more recent, large study in New Zealand found there was no effect of oxygen administration in MI patients (BMJ, 2021). There is only limited evidence – and a thought process produced by a greater understanding of cardiac perfusion – highlighting the potential for negative effects. Journal articles from as far back as 2011 (Nikolaou and Vrints, 2011) have highlighted the issue with oxygen in the MONA acronym, and the potential for stopping the use of this acronym to ‘avoid confusion, and misconceptions that might ensue as long as the subject remains unnoticed’. A further justification of stopping the use of MONA proposed by these authors was ‘to incorporate newer antiplatelet and antithrombotic therapies that are now indicated as first-line treatments of ACS.’ Kline, Conti, and Winchester (2015) suggest using ‘”THROMBINS2″ (thienopyridines, heparin/enoxaparin, renin-angiotensin system blockers, oxygen, morphine, beta blocker, intervention, nitroglycerin, statin/salicylate’ as a modern acronym, but there appears to be limited evidence of its use in practice, and it’s quite a long-winded acronym to teach.

Certainly I have been victim to the acronym-induced confusion that these authors point to. Prior to my ALS instructing, my ambulance experience and learning was very much anti-oxygen to MI patients, and often involved checking the sp02 prior to oxygen administration, and titrating oxygen delivery up, rather than down, as required. Through many scenarios acknowledging the bold point in oxygen delivery, I then began to apply oxygen before checking the sp02, and titrate down, rather than up, though the sp02 probe often goes on at the same time as this is so immediately available in my ambulance kit. I have now found more of a balance in my assessment – applying oxygen earlier than I did in the past, acknowledging, to use a simplistic term, a ‘big sick’ patient in front of me, rather than watching the sp02 waveform and waiting for a reading that looks accurate. If, however, I apply the spo2 probe and immediately gain an accurate-looking trace, and do not have a ‘big sick’ patient in front of me, I do hold off the oxygen as I once did.

I have become aware how the acronym of MONA, and the emphasis of the bold point of oxygen delivery in Resuscitation Council treatment, ‘ends up maintaining perceptions and medical practices’ (Nikolaou and Vrints, 2011), and I must be cautious in my teaching not to over-simplify treatment to a range of medical professionals, or even to those non-healthcare professionals who complete ILS courses, as doing so could encourage a ‘one-size fits all’ style of patient treatment, which simply isn’t appropriate in practice. If MONA is used as a concept in treatment, it must be taught with the usual disclaimer: check indications, cautions, and contra-indications before administration, and perhaps another disclaimer: oxygen should be given to any patient who is hypoxic. Technically, the European Society of Cardiology (ESC) guidelines advise only starting oxygen for hypoxemic patients, as mentioned above – the definition of which is associated with oxygen saturations of below 90% (Manninen and Unger, 2016; Bryne et al, 2023 – see quote below) (but good luck taking a patient into ED with abnormal saturations of 90-91%, withholding oxygen.

‘Oxygen supplementation is recommended in ACS patients with hypoxaemia (oxygen saturations <90%). Oxygen supplementation in patients who are not hypoxic (oxygen saturations >90%) is not associated with clinical benefits and is therefore not recommended.’

Bryne et al, 2023. Para 4.2.2.1.

Ah, but my decision to withhold oxygen is evidence based, you say. Perhaps, but this is counter to the current pre-hospital JRCALC guidelines for oxygen delivery, which stick with 94% as the target saturations and under 94% as the starting point for giving oxygen in myocardial infarctions (JRCALC, 2021). This is despite an acknowledgment in the guidelines that too much oxygen might cause harm in patients with AMI. Perhaps, given the uncertainties in the above research, this is the safest option. It is also specifically relating to pre-hospital care (without the aid of, for example, point of care testing), and it should be remembered that ESC guidelines are not specifically for the UK – but it is worth monitoring for changes in the guidelines. For reference, the BNF states for all patients:

‘Oxygen should not be routinely administered, however the patient’s oxygen saturation should be monitored (ideally before hospital admission) and supplemental oxygen offered if indicated. (BNF, 2023).’

The BNF then references the NICE (2010) guidelines on oxygen, which were last reviewed in 2019, which state:

‘Do not routinely administer oxygen, but monitor oxygen saturation using pulse oximetry as soon as possible, ideally before hospital admission. Only offer supplemental oxygen to:

  • people with oxygen saturation (SpO2) of less than 94% who are not at risk of hypercapnic respiratory failure, aiming for SpO2 of 94% to 98%
  • people with chronic obstructive pulmonary disease who are at risk of hypercapnic respiratory failure, to achieve a target SpO2 of 88% to 92% until blood gas analysis is available. [2010]
  • Be aware that some pulse oximeters can underestimate or overestimate oxygen saturation levels, especially if the saturation level is borderline. Overestimation has been reported in people with dark skin.’

The NICE guidelines for ACS do not mention oxygen.

Now What?

I would adjust my disclaimer when using MONA or highlighting the parts of MONA to emphasise that oxygen is only if required, under 94% or within the target saturations of retaining patients (NICE, 2010). Of course other elements of the MONA acronym also come with contra-indications, such as morphine and nitrates, and students should always be advised to check the guidelines – and in that sense, there is nothing wrong with the acronym as long as clauses are attached. Of course, the acronym does exclude other treatments such as the use of P2Y inhibitor anti-platelets (JRCALC, 2021), and I’ve come across some who are being taught ‘MONA-A’. It is important to encourage students not to follow acronyms so intently that they forget other treatments when these are clinically relevant. Beyond that, whatever assists learning, and recall is essential.

Reference List

Historical perspective and contemporary management of acute coronary syndromes: from MONA to THROMBINS2 – PubMed (nih.gov)

Oxygen Therapy in Suspected Acute Myocardial Infarction | NEJM

Routine Oxygen Supplementation in Acute Cardiovascular Disease | Circulation (ahajournals.org)

Initial treatment of acute coronary syndromes. Is there a future for MONA acronym after the 2010 guidelines? – Resuscitation (resuscitationjournal.com)

2023 ESC Guidelines for the management of acute coronary syndromes | European Heart Journal | Oxford Academic (oup.com)

Acute coronary syndromes | Treatment summaries | BNF | NICE

Recommendations | Recent-onset chest pain of suspected cardiac origin: assessment and diagnosis | Guidance | NICE

High flow oxygen and risk of mortality in patients with a suspected acute coronary syndrome: pragmatic, cluster randomised, crossover trial | The BMJ

And for further info on the definition of hypoxaemia – Pirjo H. Manninen, Zoe M. Unger, in Complications in Neuroanesthesia, 2016


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