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Category Archives: Journal

The Science of Anaphylaxis

October 1st, 2011 by

Anaphylaxis is classified as an Immediate Hypersensitivity Reaction (Class 1).

The exact reason why someone becomes hypersensitive to a particular antigen is currently unknown, but research has shown that hypersensitivity occurs after an initial exposure to the antigen.

When antigens are present in a person with hypersensitivity the B Cells (immune cells) produce IgE which then activates the mast cells. The mast cells cause Calcium (Ca++) to exit causing an inflammatory response. The mast cells also release ‘mediators‘. An allergy goes from local to systemic when mediators enter the bloodstream and effect multiple systems.

There are 2 stages to anaphylaxis. The first is the release of preformed mediators which cause vasodilation, vascular leakage and smooth muscle contraction, which leads to a large decrease in blood pressure and bronchoconstriction (if anaphylactic). The second is the creation of mediators from the breakdown of the mast cell walls which cause tissue destruction, inflammation, and eosinophil infiltration.

The main difference between anaphylaxis and a local allergic reaction is that anaphylaxis is system wide and may become a type of distributive shock (aka circulatory failure) and/or result in respiratory failure.

Mediators:

“Preformed Mediators:
Histamine: bronchoconstriction, mucous secretion, vasodilation, vascular permeability.
Tryptase: proteolysis.
Kininogenase: kinins and vasodilation, vascular permeability, edema.
ECF-A (tetrapeptides): attract eosinophil and neutrophils.
Newly Formed Mediators:
Leukotriene B4: basophil attractant.
Leukotriene C4, D4:  same as histamine but 1000x more potent.
Prostaglandins D2: edema and pain.
PAF (platelet activation factor): platelet aggregation and heparin release: microthrombi.”

Sources:

http://pathmicro.med.sc.edu/ghaffar/hyper00.htm
(Mediators)

Porth, Carol, Glenn Matfin, and Carol Porth. Pathophysiology: Concepts of Altered Health States. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2009. Print.

 

Brrrr That’s Cold! Therapeutic Hypothermia for Post Arrest Patients

October 1st, 2011 by

For a cardiac arrest patient to survive, many things need to be done quickly and correctly.  While I could have written about good quality CPR, defibrillation, ALS etc. (which I might save for another digest), I thought I would talk about something a little more sexy and novel.

Achieving a ROSC is the ultimate goal of prehospital resuscitation.  Since this only happens about a third of the time, providers might be tempted to stop and exchange high-fives.  While this may represent a successful resuscitation for paramedics, the road to recovery for the patient is long from over.  After their sustained ROSC, a sepsis-like post arrest syndrome ensues…a condition that is fatal in over 50% of patients.  This condition involves multi-organ dysfunction caused by lack of oxygen, which can include brain injury, myocardial dysfunction, systemic inflammation and the underlying pathology preceding the arrest.

Until a couple of years ago, treatment options for these post-arrest patients were limited.  Patients with a coronary occlusion were sent for an urgent trip to a percutaneous coronary intervention (PCI) center while others were assessed an ICD.  But other than those tested and true interventions, there wasn’t much that could be done for the post-arrest patient.

One of the more novel interventions actually came from “old fashion” medicine.  The idea of cooling injured patients was first coined by Hippocrates when he packed wounded soldiers in ice and snow nearly 2000 years ago.  But it wasn’t until the early 1950’s that the modern use of hypothermia specifically for cardiac arrest patients was started.  However, its use was quickly abandoned due to lack of scientific literature and the challenges associated with implementing and maintaining hypothermia with the limited technology of the time.

As we moved into the 20th century, science advanced and so did the treatment and technology options available.  Therapeutic Hypothermia (TH) was reborn and brought back into the limelight.  Scientists (and the funding organizations that pay them) realized that there was room for improvement in post-arrest survival.  So some research was done and two randomized trials showed an improvement (both clinically and statistically) for post-arrest survival when patients were treated with TH.  Now before I continue, I feel I should point out that these studies weren’t the end all and be all type of study (due to small sample sizes and only patients with an initial rhythm of VF or VT were included), but they were a start.  Since those two studies almost 10 years ago, there has been a growing body of research in favour of cooling post-arrest patients.  Hypothermia has become an international standard of care as part of both the 2005 and 2010 AHA treatment recommendations and is a critical competent of the integrated post-arrest link in the “Chain of Survival”.

So to getting into a little bit of the nitty gritty, when a patient is successfully resuscitated (with a ROSC > 20 minutes) and remain comatose, they are ideal candidates for hypothermia.  The sooner hypothermia is initiated the better, but starting within 6 hours of ED arrival is deemed to be good enough.  Patients are to be cooled to about 33°C (32-34°C is acceptable) for 24 hours.  This can be done simply administering cool saline IV and placing ice bags around the head, axilla and groin.  Or the process can be more “high-tech” by using commercial cooling blankets and catheter cooling.  Narcotics, sedatives and paralytics given as needed for pain and to prevent shivering and agitation while vasopressors are given to maintain adequate MAP.  Following 24h at 33°C patients are passively re-warmed and rehabilitation begins.  And the intervention is quite successful.  Only 6 patients need to be cooled to get one survivor (which is pretty good in comparison to other interventions when NNT = 1 is the best).

Now one might say that this protocol seems so simple.  And it is in theory simple to describe the optimal way to cool a post-arrest patient.  But in actual fact there are lots of complications associated with hypothermia.  Some physicians are not aware of detailed cooling procedures or don’t have extensive experience with cardiac arrest patients.  While sometimes the hospitals don’t have a standard TH protocol.  Or there can be patient complications as well from non-cardiac etiology to not responding to treatments.  Despite some problems, the intervention is showing promise. Hypothermia is becoming more wide spread locally, nationally and internationally. More patients are being cooled…and more patients are surviving to hospital discharge.  The big next step for this protocol will be to figure out how to improve delivery and cool more patients sooner.  The early initiation of this treatment will provide EMS with an opportunity to make a vital difference in the survival rate of post-arrest patients.

Jason Buick is a researcher at Rescu, the resuscitation science program at St. Michael’s Hospital and is completing his Masters degree in Health Research at the University of Toronto.  His research interests focus around prehospital care, specifically bystander CPR and out-of-hospital cardiac arrests.

Acetaminophen Overdose: What Pre-Hospital Providers Should Know

September 4th, 2011 by

Acetaminophen is an analgesic which is a common component in over the counter and prescription medications. Preparations such as Tylenol, Tylenol #3, Tempra, Percocet, Robaxacet as well as many other pharmaceuticals all contain varying quantities of acetaminophen. Acetaminophen is perceived by many as a benign medication. However, accidental and intentional overdose account for significant morbidity and mortality primarily due to liver damage and fulminate liver failure.

Acetaminophen is a common medication intentionally ingested during attempted suicide. This is considered an “acute ingestion”. Chronic toxicity is also seen (“chronic ingestion”) in patients who either disregard medication instructions or in patients taking multiple preparations of acetaminophen without appreciating the combined toxicity.

The recommended maximum dose of acetaminophen from all sources for a healthy adult is four grams per 24 hour period (eight extra-strength Tylenol). Toxicity is seen with doses of greater than seven grams per 24 hour period or greater than 150mg/kg/day. In these doses, the liver’s ability to metabolize acetaminophen into non-toxic metabolites is overwhelmed and a toxic metabolite (NAPQI) accumulates. NAPQI actively binds to liver cells and causes cell death and potential liver failure. When acute acetaminophen ingestion is recognized, N-acetylcysteine (NAC) is administered by hospital staff and helps to metabolize NAPQI to non-toxic metabolites.

Acute Acetaminophen Ingestions:

During the first few hours after toxic levels of acetaminophen have been ingested, patients may be completely asymptomatic. Therefore it is essential that pre-hospital care providers recognize situations where toxic levels of acetaminophen have been ingested through a detailed scene survey and patient history. History should focus on determining the exact time of ingestion as well as the quantity (in milligrams) and type of acetaminophen ingested. Sustained release acetaminophen preparations are of particular concern as blood levels may take several hours to peak and may change hospital management of acute ingestions. Co-ingestion of alcohol or other medications should also be explored. Whenever possible, all pill bottles should be brought to the emergency department.

In some situations, EMS may not be called until toxic symptoms develop. In the first 12 to 24 hours after acetaminophen ingestion, symptoms are generally limited to nausea, vomiting, malaise and decreased appetite. Frank liver failure is usually not seen until two to three days after an acute ingestion. At this stage, patients appear very unwell, presenting primarily with a decreased level of consciousness. Once again, a detailed scene survey and patient history are essential to identify acetaminophen as the offending agent.

Chronic Acetaminophen Ingestion:

Pre-hospital care providers will rarely be called to a patient with a primary complaint of chronic supratherapeutic acetaminophen ingestion. Rather, the astute EMS provider may recognize chronic toxic ingestions during any patient encounter by carefully reviewing a patient’s medications. EMS providers have a unique opportunity to identify unintentional misuse of acetaminophen so that emergency medicine staff may assess and treat liver damage and educate patients regarding appropriate dosing of acetaminophen. It is important to recognize that numerous over the counter and prescription medications contain acetaminophen and in combination, may lead to chronic toxicity. Additionally, some patients may admit to taking their partner or other family member’s medications in combination with their own and, therefore, this should also be addressed during a patient encounter.  Once again, all over the counter and prescription medications should be brought with the patient to the emergency department for review.

Treatment:

The pre-hospital care for acetaminophen toxicity is primarily symptomatic. Airway, breathing and circulatory emergencies are all possible consequences, though generally they do not occur until two to four days after acute ingestion. Thus, the primary role of the EMS provider is to collect accurate and detailed information regarding the time and quantity of acetaminophen ingestion as well as any other co-ingestions such as alcohol or other medications. Literature shows that the treatment for acetaminophen toxicity should begin within six hours of acute ingestion. Therefore, prompt recognition and an accurate history are essential.

Take-Home points:

Acetaminophen is one of the most common intentional and unintentional overdoses and can lead to substantial morbidity and mortality.

Many patients are asymptomatic after acute acetaminophen ingestion and therefore, a detailed scene survey and patient history are essential to identify acute ingestion.

Determining the time, quantity and type of acetaminophen ingested is essential for proper treatment of acute toxicity.

EMS has a unique opportunity to identify patients at risk of chronic acetaminophen toxicity due to chronic unintentional acetaminophen overdose.

Knowing the common over the counter and prescription medications which contain acetaminophen can greatly aid the EMS provider in identifying chronic unintentional acetaminophen toxicity.

 

Dr. Morgan Hillier is an emergency medicine resident with the division of Emergency Medicine, faculty of Medicine at the University of Toronto. Dr. Hillier has a research interest in pre-hospital care and holds and EMR Instructor Trainer status with the Canadian Red Cross.

Light at the End of the Tunnel

September 4th, 2011 by

Although it’s a bit esoteric, I figured between the 3rd semester students starting fall rideouts, and some groups finishing up their in-class training, it was worth doing another (and final) article about preceptorship. Having now finished my time on the road, there were a few more things I wanted to add to my original thoughts in Digest #1.

Never stop studying

This sounds daunting, but we memorize by repetition, and it’s incredible how quickly small details get lost if you don’t think about them for a month.  Near the end of my time on the road, I would find myself forgetting small (but important) points in protocols we hadn’t run into for a while.  The experience was both a bit embarrassing and discouraging as I felt like there was very little excuse for not knowing the basics at this point in the process.  That said, it was a good reminder that I had to stay on top of these things and not wait for a call to come in to reinforce them.  My advice for those of you starting into this phase of your education is to set aside at least a few hours each week and force yourself to review all of your ALS and important (but obscure BLS) protocols.  That way, regardless of what you’re doing call-wise, you’ll keep those important protocol details in your head.

You are not the gum on the bottom of someone’s shoe

Before going out on the road, we got the idea that “students were the absolute bottom of the pile” drilled rather deeply into our heads.  Unfortunately the important message of “work hard, be first to offer to help, always try to make the best impression etc.” got mostly imparted on us as “most medics out there will treat you like crap because you’re a student…paramedics eat their young”.  Having been on the road, I can tell you that my experience was very different.  As a student, you are definitely at the bottom of the pecking order.  Sleeping on a couch (when there’s a medic who wants it), watching someone else clean a truck, walking by full garbage cans etc. is a sure-fire way to get a bad reputation for both yourself and your school.  That said, every medic I met treated me with respect, and I was never made to do something just because I was the student.  I might have just been lucky, but in talking with the rest of my class, it seems their experience was similar.  Long story short…expect to be “on” all the time, (you’re trying to make a good impression to your preceptor and the service…in fact, your time on the road is kind of like a painfully long job interview), but don’t worry that every medic is going to behave like the drill sergeant from hell.

Focus on your preceptorship

A few students have asked me what other stuff I did during my time on the road.  Did I do a PALS course, get my ITLS out of the way (probably a good idea), was there lots of extra CME I could do?  Everyone’s energy level is different, but my advice would be to just focus on your preceptorship for these next few months.  There is MORE than enough to study and learn without adding extra stuff to your plate.  I found 12hr shifts difficult to get used to.  It got easier, but for the first few weeks, I was literally useless after a busy day.  Some of you might have more downtime then others, but between studying on shift, running every call (another joy of being a student) and doing most of the cleaning / organizing in the truck and station…the days are long.  One thing I started doing early on was writing notes / reminders after every call (and studying them later).  I also wrote down all the medications we came across that I didn’t know, and have been trying to memorize that list as well.  Little things like that will help you get more out of your hours on the road, and will keep you busy enough that a PALS course will be the last thing you want to do.  Partway through my preceptorship, my preceptor also had me start writing 3 positive and 3 “needs improvement” things for each call, something that might be worth considering for yourself.  90% of the time I wasn’t attending a call (or sleeping), I was reading or writing in my notebook, and I think that made a big difference overall to what I learned and retained over the last 3 months.  At the end of the day, you’ll find a rhythm that works for you, I just think there’s enough to do while on the road that most of you won’t need to look outside of your preceptorship for extra work.  Focus on the experience and made the most of it that you can, because you’ll never have another opportunity like it again (until you get to your ACP preceptorship…but we’ll write about that in a few years :) )

Scenario Tips for the Road

August 1st, 2011 by

Some things that I have found to be good practice in getting more comfortable with all aspects of being a paramedic. Through and through, the bottom of the line is to train in as realistic of circumstances as possible. Below is a small list of things that I tried to do during my practice sessions:

  1. Checks against the clock: When conducting the scenario, during the breathing and the circulation checks, deliver what you actually find. Provide information closer to what is expected. If it is a breathing check, have the patient mimic the rate and depth. For the pulse check, have someone verbalize each beat. Alternatively, you can deliver how many beats were detected in a 10 second period. Practicing this now will make it more natural when you need to do this in a truly stressful situation.
  2. Give your findings before you receive it. Rather than expecting a response, diagnose and report. I found ‘this’. If the person running the scenario has something that contradicts what you say, they will let you know. (Get used to calls with little prompting).
  3. Don’t look at the person running the scenario. Ever. Use this as an opportunity to train your ability to multi-task. In the sense of training your muscle memory, the best thing you can do, is to look at the tool you are asking about. If you are asking for the blood pressure, look at the cuff and the same idea with the SpO2.
  4. If it isn’t on you. You don’t have it. Typically, this isn’t a problem coming on scene, however practice leaving the scene as well. If you forgot your bags, you forgot them. If you have other tools on you, use them. If you have a flashlight, use it to check pupils. If you don’t have it, use an alternate method to assess. Faking this, by pretending your pen is a flashlight, trains you to go to your pen holder rather than where your actual light would be.
  5. Do everything from top to bottom. This includes from the meet and greet to loading the patient in the back, to sending your patch and reporting to the triage nurse. This will train you to take better notes on scene, either written or memorized. If you get stuck at a point, this will help you revert to a route of diagnostics to which you may have missed.
  6. If you lack the basic skills, such as applying the K.E.D. work on it outside of scenarios. Challenge yourself by doing it blind folded, or with the patient in complex positions.
  7. Give both positive and negative feedback. Learn as a group and be merciless. If it was a good call, the next one has to be stepped up. Keep challenging each other. If you have become good at your trauma call, it may to be time to work outside of the lab. Use actual stair wells, closets, washrooms and cars.
  8. The final and arguably most important. If it can be argued, prove it. Hit the books and show what is right. Do not grow an ‘ego’. Expect to be wrong. Expect to loose face over something minute. Expect to look bad. We are your friends. If we didn’t like you we wouldn’t tell you.

This is just a small set of ideas that can improve your training. If anyone has other ideas, I’d love to hear them so use the comments section below to leave your suggestions.