UMEM Educational Pearls

Ondansetron (Zofran) has been off patent and its price has dropped to the point that it has supplanted promethazine (Phenergan) and even metoclopramide (Reglan) as the antiemetic of choice. With its low side-effect profile and known efficacy it is now being utilized in hyperemesis gravidarum and in pediatric gastroenteritis. - A cochrane review showed ondansetron to be both safe and effective in the pediatric population. Consider it prior to attempting oral rehydration therapy to increase effectiveness. - Dose: 0.1 mg/kg - you can give the oral dissolvable tablet (ODT) - ages 4-11 you can give 4mg ODT - Above age 11 the dosing is the same as an adult.

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• Patients with severe or rapidly progressive weakness due to a Myasthenia Graves (MG) exacerbation should be admitted to an intensive care unit.
   
• Acute MG patients' forced vital capacity (FVC) should be monitored every 2 to 4 hours to accurately assess the function of their respiratory muscles.
   
• FVC can easily be measured at the bedside, particularly by a respiratory technician.
   
• Once the patients' FVC is consistently approaching or reaches 15 mL/kg, the patient should be electively intubated in order to ensure protection of their airway.  In an average sized adult, an FVC of 1000 mL is the point at which respiratory failure is eminent.
   
• Arterial blood gas abnormalities are not reliable indicators of respiratory muscle decompensation, and typically occur as a late sign of respiratory failure.
   
• Once the patient is intubated, anticholinesterase medications are typically withdrawn.

Assessing Volume Status in the Critically Ill

• In previous pearls we have discussed the many limitations of central venous pressure as an accurate marker of volume status.
• Importantly, the focus of volume assessment should be on determining which patients are likely to augment their cardiac output in response to additional IVFs, i.e. 'preload responsive'.
• Ultrasound can be used in the ED to assist in identifying which patients are preload responsive.
• In general, a 15% variation in the inferior vena cava diameter with respiration predicts response to additional fluids.

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The One Minute Preceptor Model of Teaching in the ED

This is a teaching strategy that most of us are very familiar with. Why? Because many, if not most, of us do it every day. We listen to a case, get a committment from the learner, probe for supporting evidence, and then give a teaching pearl and offer learning resources.

Perhaps one of the biggest pitfalls in teaching is NOT WAITING for the learner to answer to question. How often have you asked a question to a medical student and gave the answer? How often has a student presented a case and then they clammed up and didn't commit to a diagnosis or treatment plan?

A simple strategy for teaching success:

• Make learners "jump out there" and give you a diagnosis and treatment plan, i.e. get a commitment. Do your best to keep your mouth closed for a few seconds
• Give learners time to answer. You will be surprised. A few more seconds of waiting makes a big difference.

Dark chocolate is being touted more and more as being beneficial to vascular health. It contains polyphenols which has been found to exert anti-oxidant effects and improve endothelial and platelet function. The benefit appears to occur anywhere from 2-8 hours after ingestion of dark chocolate. Unfortunately, the same has not been found true for white chocolate or milk chocolate.

The only caveat is that most of the studies seem to originate in Switzerland and are funded by the Mars Company and Nestle...but who care?? Go ahead and have some dark chocolate every day!

[Dark Chocolate Improves Endothelial and Platelet Function (Hermann F, Heart 2006); Cocoa and Cardiovascular Health (Corti R, Circulation 2009)]
 

The French Surgeon Rene Le Fort first described these facial fracture patterns.   Reportedly he made the observations after dropping numerous skulls from the wall of a castle.  This might be why we don't see pure Le Fort fractures in our patients most of the time as they are not likely to be falling off castle falls head first.

The classic fracture patterns are:

1. Le Fort I fractures extends from the nasal septum to the lateral pyriform rims, travels horizontally above the teeth apices, crosses below the zygomaticomaxillary junction, and traverses the pterygomaxillary junction to interrupt the pterygoid plates.
2. Le Fort II fracture has a pyramidal shape and extends from the nasal bridge at or below the nasofrontal suture through the frontal processes of the maxilla, inferolaterally through the lacrimal bones and inferior orbital floor and rim through or near the inferior orbital foramen, and inferiorly through the anterior wall of the maxillary sinus; it then travels under the zygoma, across the pterygomaxillary fissure, and through the pterygoid plates.
3. Le Fort III fractures (transverse) are otherwise known as craniofacial dissociation and involve the zygomatic arch.  These fractures start at the nasofrontal and frontomaxillary sutures and extend posteriorly along the medial wall of the orbit through the nasolacrimal groove and ethmoid bones. The fracture continues along the floor of the orbit along the inferior orbital fissure and continues superolaterally through the lateral orbital wall, through the zygomaticofrontal junction and the zygomatic arch.

 

http://radiographics.rsnajnls.org/cgi/content-nw/full/26/3/783/F15

• Scabiess requires sensitization to the organism, Sarcoptes scabiei. 
• It may take weeks before pruritus develps in a child infested for the first time.  On the next exposure, however, INTENSE itching will occur within 24 hours. 
• Burrows in the webs of fingers and toes are common.
• Treatment:  Firstline is permethrin 5% cream on the entire body from the neck down, and wash off after 12 hours.  Alternative is lindane 1% (1oz of lotion or 30g of cream) applied in a thin layer over the entire body from the neck down, and thoroughly washed off after 8 hours OR ivermectin 200ug/kg orally repeated in 2 weeks.
• Many avoid lindane because of neurotoxicity.  Do not apply it after a bath, or to someone with extensive atopic dermatitis as seizures have been reported.
• Decontaminate all bedding and cloting.
• Warn patients that the rash and itching may persist for up to 2 weeks after treatment.

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Colchicine is a drug used for the treatment of acute gout attacks. It inhibits microtubule formation vital for cellular mitosis. It is also a drug with a narrow therapeutic index and lethal toxicity:

- Colchicine can be lethal at 0.5 mg/kg or even lower. Though this would be about 50 tablets and seems alot, remember it is prescribed 2 tablets initially then every hour until diarrhea presents (i.e. preliminary toxicity)

- Toxicity presents in 3 stages:

1. 0-24hrs: Nausea, vomiting, diarrhea
2. 1-7days: Sudden cardiac death, pancytopenia, renal failure, ARDS
3. >7days: Alopecia, myopathy, neuropathy (if they survive)

- No antidote, supportive care only available.

- Presentation is similiar to that of a radiation exposure

 

• Myasthenia Graves (MG) is an autoimmune disorder wherein antibodies, perhaps created by the thymus, block the acetylcholine receptors at the post-synaptic neuromuscular junction.
   
• The term "myasthenia graves" literally means "severe muscle-weakness" from its Greek and Latin origins.
   
• The clinical hallmark of this disorder is muscle weakness and fatiguability, primarily affecting the facial muscles.
   
• In spite of having personally seen about 3 cases of MG in the ED over the past couple months, this disorder is actually one of the less common autoimmune disorders, affecting 200 to 400 per 1 million persons.
   
• Treatment includes cholinesterase inhibitors, immunosuppressants, and at times, thymectomy.

Diagnostic Errors in the Emergency Department

Believe it or not, there is actually a field of medicine that is devoted to examining how physicians think in clinical practice, i.e. how we make diagnostic decisions. Much of the work on this has been done by Pat Croskerry. This is extremely important for emergency physicians because we frequently have to make split second medical decisions with little to no information.

Why is this so important? If we can understand where errors are made, we can actually improve our own diagnostic skills and reduce our errors rates.

 

Some key pitfalls that we all fall victim to:

• Bias-this refers to the chart that says under past medical history "fibromyalgia, interstitial cystitis, bipolar, chronic constipation." This type of chart has set us up to potentially miss a diagnosis because our thought processes shut down before we have even started. Ever miss a diagnosis or almost make a mistake because of your feelings about a patient (sometimes BEFORE seeing them)? This is bias. Being aware of this dangerous pitfall in practice is the first step in preventing bias-related mistakes.
• Premature closure of the differential diagnosis-Now, we do this a lot in medicine. Some diagnosis falls in our lap (patient gives it to us, or a consultant tells us that is what it is) and we fail to r/o other things on our list. Key mistake we make is related to not considering other entities on the differential diagnosis. Take home point: Don't narrow the differential diagnosis until it is time to do so.

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Mechanical Ventilation and Obesity

• Obesity is defined as a BMI of 30 - 34.99 kg/m2, with class II obesity defined as 35 - 39.9 kg/m² and extreme obesity as > 40 kg/m²
• In obese patients:
  • oxygen consumption is increased with a high proportion going to the work of breathing
  • lung volumes are abnormal with reduced expiratory reserve
  • the alveolar - arterial oxygen difference is increased
  • respiratory system compliance is markedly reduced
• These changes are futher exacerbated in the supine position
• To overcome the effects of reduced compliance, higher levels of PEEP are generally needed
• In addition, higher plateau pressures may be necessary to achieve adequate tidal volumes

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As we head into the warmer months we should remember that every year there are reports of a toddler left in his car seat for 15 min who comes in uresponsive with hyperthermia. 

Heat related illnesses are a continuum from heat cramps to heatstroke.  The hallmark of heatstroke is hyperthermia with mental status changes and when identified rapid cooling must be initiated.  Mortality for heatstroke is reported as high as 80%. 

Children are more susceptible to heat stroke because of a greater surface area to body mass ratio, higher metabolic rates, less developed sweating mechanisms, and inability to always remove themselves from the hot environment.

The quickest and easiest way to cool a conscious patient is by evaporation.  Changing water from a liquid to a vapor is an endothermic process.  Removal of all clothes, followed by misting or wiping with tepid water of the entire skin is very effective.  Having a fan pointed at the child can enhance this method.   

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Pregnancy is a risk factor for AMI, increasing the risk 3-4-fold. The risk is accentuated with age, especially in women > 40 yo in whom the risk is 30-fold higher. Overall, heart disease is the biggest [non-obstetric-related] killer of pregnant women in the developed world, surpassing even thromboembolic disease. [Roos-Hesselink, et al. Pregnancy in high risk cardiac conditions. Heart 2009;95:680-686.]

Glucose-6-Phosphate Dehydrogenase Deficiency

• G6PD Deficiency is a genetic disorder which can cause hemolytic anemia when people with the disorder come into contact with drugs, food and other substances which cause oxidative stress.
• It is the most common genetic enzyme deficiency.
• G6PD is an inherited disorder with over 400 different known variants.
• Oxidative stress can cause the premature distruction of RBC's due to the lack of the enzyme reduced glutathione which G6PD helps produce.
• Drugs that are at high risk for causing hemolytic anemia in those with G6PD deficiency are:
  • NSAIDS (Asprin, Tylenol, Ibuprophen)
  • Quinolones
  • Sulfa drugs
  • Drugs metabolized known to cause blood or liver related problems or hemolysis
  • Primaquine
  • Nitrofurantoin
  • Glyburide
  • Dapsone

Also make sure that you are not G6PD deficiency if you are eating with Hannibal Lecter as Fava beans and other legumes can also cause an episode of hemolysis.

A good reference for G6PD deficiency is http://g6pddeficiency.org/index.php

Overdoses of insulin glargine (Lantus) are rarely reported in the literature.  In fact, there are only 6 case reports.  We recently had a patient in our ED who was hypoglycemic from insulin glargine.  The hypoglycemic episode was quite prolonged (> 24 hours) in the ED before being the patient was transferred to the MICU.  Here are a few points to remember:

• Insulin glargine does not peak; it was designed to mimic basal islet cell insulin secretion.
• In the therapeutic setting, its effects can last up to about 24 hours.  In overdose the hypoglycemic effects have been reported to last up to 60-130 hours!
• Be prepared to give IV dextrose 5% or 10% infusion for the duration of the patient's hypoglycemic effect.  This can be supplemented with food.
• Octreotide will be ineffective for exogenous insulin poisonings because its effect comes from its ability to suppress insulin secretion from the pancreas.

• One may wonder how to determine whether a patient has limb ataxia in the setting of limb weakness when scoring the NIH Stroke Scale (NIHSS).

• The component of the NIHSS that tests for limb ataxia asks that the patient perform finger to nose and shin to heel testing.

• A patient who does not exhibit any ataxia would receive a score of 0 (zero), which is the best score.

• If the patient does not exhibit any ataxia because he/she has neuromuscular weakness and therefore can't perform the tasks at all, they would also receive a score of 0 (zero) on this component of the NIHSS.

Ventilation in the Brain-injured Patient

• As we have discussed in previous pearls, the ARDSnet trial forms the basis for ventilatory management in the ICU.  A primary component to current ventilatory management is the focus on maintaining lower and safer distending pressures through the use of lower tidal volumes.
• Similar to last week's pearl on the obstetric patient, these ventilatory settings may not be applicable to all patients.
• Recall that the use lower tidal volumes results in lower minute ventilation.  This leads to the accumulation of CO₂, termed permissive hypercapnia.  In general, we tolerate higher levels of CO₂ in favor of lower plateau pressures.
• For the brain-injured patient, however, increases in CO₂ may increase intracranial pressure (ICP) causing adverse effects.
• Current recommendations for mechanical ventilation in the brain-injured patient include maintaining a P_aCO₂ between 35 - 40 mm Hg.  Thus, you need to be more vigilant at following P_aCO₂ in this patient population.

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The One Minute Preceptor-Microskills in Teaching

Most clinical teaching takes place in the context of busy clinical practice where time is at a premium. Microskills enable teachers to effectively assess, instruct, and give feedback more efficiently. This model is used when the teacher knows something about the case that the learner needs or wants to know.

Most of already do this on a daily basis when a learner (student or resident) presents a case to us.

 

• Get a commitment (Make them commit to a diagnosis and/or management strategy)
• Probe for supporting evidence (why do they think this patient with CP has an MI?)
• Teach general rules
• Reinforce what was right
• Correct mistakes

One of the biggest pitfalls in teaching, particularly to medical students, is the first skill, getting a commitment. Let (i.e. make) the student commit to a diagnosis and treatment plan and avoid spoonfeeding them.

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Adenosine is everyone's favorite drug for SVTs, and it is often even used as a diagnostic maneuver in some tachydysrhythmias of uncertain origin. BUT there are some definite cautions of which we must all be wary:

1. Adenosine CAN convert some types of ventricular tachycardia to sinus rhythm. This "adenosine sensitive VT" is very well reported in the cardiology literature. Don't use adenosine as a diagnostic method of distinguishing VT from SVT (with aberrant conduction).

2. Atrial fibrillation with WPW can sometimes mimic SVT if one doesn't look closely and notice the irregularity. If you misdiagnose these patients as having SVT and give adenosine, you will likely induce VFib. Not good, Mav, not good!

3. Adenosine causes some histamine release (thus the flushing and hot sensation that patients report). That's bad for patients that have reactive airway disease (RAD). Adenosine should be avoided in patients with severe RAD by history (asthma, COPD) or if patients have active wheezing.

4. Concurrent use of adenosine in patients on digoxin or patients that have received digoxin or verapamil has been reported to cause VFib in rare cases.

5. The effects of adenosine appear to be potentiated by dipyridamole and carbamazepine. Lower the dose of adenosine in patients that take these medications.

6. The effects of adenosine are antagonized by methylxanthines such as caffeine or theophylline. You will probably need higher doses of adenosine in these patients.

7. There are rare cases of adenosine inducing atrial fibrillation. I'm not sure what to say about this, except don't be surprised if your patients goes from SVT into atrial fibrillation. Rare, fortunately.

8. And finally...always remember to push adenosine very quickly and follow immediately with saline BOLUS flush (don't just open up the IVF...you must PUSH 10-20cc of NS); and warn your patient that for ~10 seconds they are going to feel like they are about to die while the adenosine takes effect. If you don't warn them, they will never trust you or the drug again.

9. And finally finally...always have your code cart ready to go when you are using potent cardiac drugs such as adenosine. Don't let yourself be unprepared for a side effect.

Bad luck only happens when you are unprepared!

AM

Radial Head Fractures:

Radial head fractures are more common in adults, where radial neck fractures are more common in children.  Remember to look for fat pads to help make the diagnosis if it is not obvious on plain films.  On plain films, a line drawn down the middle of the radial head should always line up with the capitellum of the humerus.  If this does not occur the radial head is dislocated and/or fracture.

Orthopaedics use the Mason classification to help guide treatment, and break down fractures into 3 different types.

• Type I - is undisplaced, generally treated nonoperatively. 
  • Early mobilization prevents chronic elbow stiffness.
• Type II - a single fragment is displaced.
  • May be treated nonoperatively if the displacement is minimal.
  • The rule of threes is used. Nonsurgical treatment can be considered if the fracture involves less than one third of the articular surface, less than 30° of angulation, and if displacement is less than 3 mm
• Type III  - is comminuted.
  • Usually require operative intervention.