UMEM Educational Pearls

Acute Cor Pulmonale and Ventilation In the critically ill,

Acute cor pulmonale (ACP) is usually observed in the setting of massive pulmonary embolism or acute respiratory distress syndrome (ARDS). As we manage more and more critically ill patients in the ED, it is likely that you will manage patients who develop ARDS.

We have discussed in previous pearls that, especially in ARDS, using a low tidal volume and monitoring plateau pressure are key components to mechanical ventilation.

For patients with ARDS who develop ACP, consider lower plateau pressure thresholds (< 26 cm H20) and minimizing PEEP to < 8 cm H2O.

If ACP persists despite lower plateau pressures and low PEEP, consider prone position ventilation as a last resort.

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Questioning Learners in the ED-Wait Times

When teaching medical students and residents, consider that the literature shows that we tend to wait only a few seconds (some studies say 3 seconds-which seems like a long time when you are waiting for a response) for a response. Bottom line, it has been demonstrated that many learners have the answer and will respond if simply given the time. Hard to do sometimes in a busy ED. Learners who aren't given time to respond will quickly learn that if they simply wait long enough the answers will be given to them.

So, when asking a question (NOT pimping) to a medical student or resident, simply wait a little longer. They may very well surprise you with the answer.

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• Fractures of the phalanx are common, and fractures of the proximal phalanx can lead to significant disability if not treated appropriately.

• Be sure to check for malrotation, which is a common problem.  Check for this by examing for the normal cascade in finger flexion with the tips of the fingers pointing toward the proximal portion of the scaphoid

• Acceptable Reduction:
  • No rotational deformity can be accepted
  • No more than 10 deg of angulation should be accepted in any plane
  • Malreduction will cause loss of equilibrium between flexor and extensor tendons.

• Place the splint on the dorsum side of the finger so that the patient can still have sensation of the tip of their finger tip.

• Patients requiring prompt referral to a hand surgeon are those with:
  • Intraarticular fractures
  • Malrotation
  • Unacceptable reductions
  • Unstable fractures

 

• Increasing use of OTC meds is a worldwide occurence with $3.5 billion each year spent in the US.
• About 4 million children younger than 12 yrs are treated with these meds each week in the US.
• In 2007 the FDA recommended that the use of OTC cold meds (antihistamines-brompheniramine, chlorpheniramine, diphenhydramine, doxylamine; antitussive-dextromethorphan; expectorant-guaifenesin; and decongestants-pseudoephedrine and phenylephrine) be prohibited in children < 6 yrs.
• A recent review of 103 childhood deaths due to OTC meds found that most deaths were from product misuse rather than adverse effects resulting from recommended doses particularly when the product was used with the intent to sedate a child. 
• Children less than 2 years old were most susceptible to death using these products which is why manufacturers voluntarily withdrew the use of OTC meds in this age group.

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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.