Understanding Atropine

As requested, during our previous Adenosine discussion, we will briefly review, Parasympathetic stimulation and Atropine pharmacodynamics on the heart.

ACETYLCHOLINE (ACh) is one of the Neurotransmitters, a chemical signal, used by the Central Nervous System, which has many effects on the body, from stimulating muscle contraction, inducing peristalsis (digestion), Bile release by the liver, and as discussed here, decreasing Sinoatrial Node (SAN) and Atrioventricular Node (AVN) stimulation. When the later occurs, often we encounter its effect recorded on the ECG, seen as:

  • Sinus Bradycardia
  • SA Blocks
  • AV Blocks

The most common symptoms of Vagal stimulation include:

  • Vasovagal Syncope
  • Nausea and vomiting
  • Dizziness

ACh is released during Vagus Nerve (Cranial Nerve X) stimulation ,which in the heart, binds to M2 Muscarinic Receptors, one of the 5 types of Muscarinic Receptors, which mainly work in CNS and skeletal muscle. Out of all these receptors, binding of ACh to M2 receptors affects the heart and its overall conductivity.

How does this work?

  • Decrease Cyclic Adenosine Monophosphate (cAMP) intracellular
  • This slows down L-type Calcium Channel opening, leading to decreased automaticity and slightly decreasing contractility
  • Potassium (K+) efflux (leaving the cell) is delayed, which prolongs repolarization, delaying the next action potential

The combination of all these actions, hyperpolarize the cells, increasing SA Nodal and AV Nodal threshold, which decreases the overall conduction, mainly through the AVN. This is known as Negative Dromotropic Effect.

 

ATROPINE

atropine

Atropine, an antichollinergic, derived from the plant, Atropa Belladonna, or “Deadly Nightshade flower”,  blocks ACh binding to M2 receptors, giving it the “Parasympatholytic” property. The goal is not necessarily to increase SAN function, but rather, block the parasympathetic  response produced by M2 receptor stimulation, leading to normal SAN and AVN function.

 Now that we understand how Vagal Stimulation affects our cardiac function, the use of Atropine makes a bit more sense during suspected bradycardia induced symptoms.

 

Gallows humour at the hanging committee

Have you ever submitted to the EMJ or to any other journal for that matter? If so then you will know the fear and trepidation that results as you wait for the answer from the editor. Will your paper be accepted (hurrah) or rejected (boo). I’ve experienced much pain at the hands of editors and reviewers over the years and I’m doing my best not to give any pain back, but to be honest being part of an editorial team is not a popularity contest. A key part of our role is to decide what’s in and what’s out, and it will ever be thus.

The editorial decision process will vary from journal to journal but here at the EMJ all papers initially go to the editor in chief, and then are disseminated to handling editors who recruit and then manage the peer review process. Once complete the handling editors advise the editor in chief on their decisions and opinions. Ultimately the buck stops with the boss, but the handling editors clearly play a key role. That’s my position in this organisation and in the most part the acceptance/rejection decision is fairly straightforward after careful reading of the manuscript in conjunction with the reviewer comments.

However, it’s not always straightforward. There are many circumstances where it’s just really difficult to make a decision on whether to recommend publication. Here are some examples.

  • A survey paper tackles a highly controversial and politically charged subject but has a less than perfect response rate. The information will be popular, interesting and controversial. This paper will be widely read by your subscribers, may attract media interest and (hopefully) some social media activity, but it’s not great science. Would you publish it?
  • A randomised controlled trial of a new drug fabulon is submitted. It is highly effective in treating madeupitis disease in South East Somewhere. It’s a great trial, but as far as you are aware this disease would rarely be encountered by your readership. Great science, but poor applicability. Would you publish?
  • An observational study of sedation in the ED is submitted and 4 reviews are returned. 2 reviewers recommend acceptance without correction, the other 2 recommend instant rejection. Both recognise flaws but the reviewer judgements are so distant that you wonder if they read the same paper. Would you publish?

So what next? As an author you may experience a pause in proceedings. It’s quite likely that the editorial team have referred you to a special place. It’s not somewhere where we flip coins to decide who gets in, nor do we throw darts at manuscripts on the wall, nor throw papers down the stairs and publish the ones on the top steps (honestly all of these accusations have been made by the disgruntled). No. Flipping coins or other arbitary methods of choice are considered very bad practice in the editorial world. It would be highly unfair to the authors so there must be another way and it’s entirely possible that you may have experienced a referral to THE HANGING COMMITTEE!!!

wikimedia

wikimedia

When I was first referred to a hanging committee I was rather shocked as I imagined my work and toil being led to the gallows. Should it pass the committee it might receive a pardon and be passed on to production for publication. Should it be found wanting then it would be hanged there and then, despatched, killed and never seen again.

In truth my perception of the hanging committee was quite wrong, the origin of the term not being the gallows, but the rather more enticing, pleasant and appreciative world of art. I was surprised to learn that the hanging committee term originates from the art world where decisions are made on which paintings will be shown to the public. A judgement is made in committee on what to hang for public consumption and of course at this point it all makes sense. In publishing as in art there are judgements to be made on what to present and how it should be presented. The analogy fits and so the EMJ team meets to hang papers on a regular basis. The hanging committee sits not to sentence and murder, but to view, read, appreciate and try to select the best for the hard pressed pages of the journal.

So, if you get a referral to the hanging committee it’s not a death sentence and there may well be a reprieve. Hold tight and wait to see what the decision is, you might just catch the eye of the committee and find yourself hung rather than hanged.

Hanging Committee, Royal Academy, 1892 by Reginald Cleaver Wikimedia

Hanging Committee, Royal Academy, 1892 by Reginald Cleaver
Wikimedia

vb

 

S

@EMManchester

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Asthma…The Music Of The Night

 

In this episode, the first of a three part series on asthma, we will cover the diagnostic and treatment strategies that will help you rapidly move patients through your ED.  No, of course you don't need the patient's asthma classification, but you DO NEED to understand which patients need more treatment and when it's OK to stop.  I will break that all down for you with the aid of the algorithm above.  We'll talk in depth about who can go home safely and who should be in the Unit! Download the flow sheet from the link above, put it in your smart-phone so you have it for your next asthma encounter, and follow along.  It's going to get musical..

Rich Levitan's Yellowstone Advanced Airway Critical Care Course

 

 

 

 

Cabo CME Course - Levitan, Weingart, Matt & Mike, Orman, and Sloas