UMEM Educational Pearls

There are many causes of rightward axis on electrocardiography: RVH, COPD, acute (e.g. PE) or chronic (e.g. COPD, cor pulmonale) pulmonary hyptertension, sodium channel blocking drug toxicity (e.g. TCAs), ventricular tachycardia, hyperkalemia, dextrocardia, left posterior fascicular block, prior lateral MI, and of course misplaced leads.

In emergency medicine, however, the causes of acute/NEW rightward axis constitutes a smaller list. Perhaps the two most important causes of acute/new rightward axis in emergency medicine that should be remembered are PE and sodium channel blocker toxicity. In both of these conditions, the rightward axis may be the only obvious finding on the ECG.

The takeaway point is this: when you see new righward axis (compared to an old ECG) and you see nothing else "jumping out" at you, consider PE and consider sodium channel blocker toxicity.

Most people are now using Ultrasound to aid in cannulation of the femoral and internal jugular veins, but if you find yourself without the ultrasound machine you can increase your chance of successful cannulation of the femoral vein by positioning the leg properly.

Werner et al looked at the common femoral veins of 25 healthy volunteers and noted that the femoral vein was accessable more often when the hip was abducted and external rotated.  This simple position change increased the mean diameter of the vein, and prevented the vein from being directly posterior to the artery.

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Pyloric Stenosis

• The cause of the hypertrophied pylorus muscle is unknown, but it is usually not present at birth.  Mean onset of symptoms is 2-3 weeks of life, but range can be birth to 5 months with a 4:1 male to female occurrence.
• Clasic presentation is projectile, nonbilious vomiting of last feed which may be immediate or hours later.
• Pyloric Stenosis is the most common reason for abdominal surgery in the first 6 months of life.
• Textbook lab abnormality is a Hypochloremic hypokalemic metabolic alkalosis but this is a later finding and can not be used to rule out the diagnosis.
• Ultrasonography has become the standard imaging technique for diagnosis. It is reliable, highly sensitive, highly specific, and easily performed.
• Muscle wall thickness 3 mm or greater and pyloric channel length 14 mm or greater are considered abnormal in infants younger than 30 days. 
• DDX includes :  Normal Regurgitation (all babies do it!!!), GERD, Milk Intorerance, Obstruction (antral webs, volvulus,intussusception)

• Elemental Mercury is found in manometers, some mercury switches and thermometers.
• Elemental Mercury is also in the CFLs (Compact Fluoroscent Lightbulbs) that are popular now due to rising energy cost (approx 4 mg)
• Organic mercury found in seafood is only toxic in high consistent doses - though has been catastrophic. See attached picture which was the award winning Time magazine cover of the year showing a mother holding her child who had congenital disfigurement due to mercury being dumped into Minamata Bay
• Elemental Mercury is mostly a neurotoxin causing personality changes, nervousness, shyness and depression.
• Acrodynia is pain and pink discoloration of hands and feet due to mercury poisoning in children.

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• Don't forget to check for distal lower extremity neurologic deficit after knee injury, particularly when there is a direct blow to the popliteal fossa.
• The common peroneal and tibial nerves exit from the lateral and middle sections of the popliteal fossa, respectively.
• The common peroneal nerve wraps laterally around the fibula (where it's palpable), primarily supplying the lateral portions of the lower leg and foot.
• The tibial nerve primarily supplies the muscles of the posterior compartment of the lower leg (i.e. gastrocnemius, soleus, popliteus).
• Both the common peroneal and tibial nerve fibres branch into the sural nerve, which supplies the lateral foot.
• Common peroneal also splits into deep and superficial branches which supply the muscles of the anterior lower leg compartment and lateral lower leg compartment, respectively.  The deep branch also provides cutaneous innervation of the cleft between the great and second toes.

--  IN SUMMARY:

• Neurologic deficit of the posterior lower leg muscles likely = tibial nerve injury.
• Neurologic deficit of the anterior and lateral lower leg muscles likely =  peroneal nerve injury.
• Decreased sensation in the web space between the great and 2nd toes likely = (deep) peroneal nerve injury.
• Decreased sensation over the lateral dorsum of the foot likely = sural nerve injury.

*** Speaking of such deficits by naming the affected nerve distribution is particularly helpful when consulting orthopedists, neurologists, etc.

Mechanical Ventilation in Asthma

• Approximately 25,000 asthmatics are intubated each year
• Mismanaged mechanical ventilation in asthma carries significant morbidity and mortality
• One of the primary goals of ventilating the asthmatic is to allow for lung deflation
• The most effective way to allow for lung deflation, and reduce hyperinflation, is to reduce minute ventilation (TV x RR)
• Initial tidal volume settings should be 6 ml/kg of predicted body weight; if plateau pressures are > 30 cm H₂O tidal volume should be decreased to 4 - 5 ml/kg
• Reduced respiratory rates will also allow longer exhalation times; initial recommended rates are 6 - 8 breaths per minute
• If plateau pressures are still high despite lowering tidal volume and respiratory rate, you can then shorten the inspiratory time to allow for longer exhalation

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How good was that CT Pulmonary Angiogram You Ordered?

CT is currently the gold standard imaging modality for pulmonary embolism. Since we order these quite a bit in the ED, we should know some of the important nuances regarding interpretation of the scan. All of us at some point have looked at a pulmonary CTA and thought that it looked a bit "fuzzy" or perhaps it didn't "look right"  This happens more often in obese patients. There is good literature to show that a suboptimal CTA misses clinically significant PE. So, it is important for emergency physicians to know a little about the CT scan ordered for our patients. 

How can you know if the CT scan YOU ordered to rule out PE is really "good enough" to rule out PE?

• Well, you can rely on the radiologist. But remember they may not comment of the quality of the scan. Or, they may simply recommend another test.
• Look at the Hounsfield Units (HU). For those who have PACS or some other computer radiology display,all you need to do is move the cursor to the main pulmonary artery and see what value (usually on the bottom of the screen) is displayed. 
• A HU >280 indicates that the CT is "good" (i.e. good enough contrast bolus to detect clot). By the way, >350 looks white.

So, a 34 yo obese patient who gets a CT scan to rule out PE, who has 170 HU in the main pulmonary artery, has not had an optimal CT. Thus, you really haven't ruled out PE even if the read is "negative." Often this is due to poor bolus timing. 

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Fracture Management:

In order to maximize billing when caring for patients with fractures two things should be done:

1. The physician does not need to place the splint, but the physican must document that they checked the splint for proper placement and alignment for it to be billed appropriately..
2. Emergency physicians also provide a lot of "definitive" care for fractures.  (i.e.: we provide the same care that the treating specialist would provide) and can bill for a higher level if this is documented properly. 
   1. For instance, if you are treating a impacted, stable distal radius fracture with a splint and pain medication this is the same definitive care the orthopedist would do as they are only going to exchange your splint for  a cast. 
   2. Another example is the treatment of rib fractures which may consist only of pain control, incentive spirometry and instructions to prevent pneumonia.
   3. In these patients, have the patients follow up more than 48 hours later.  If you document that the patient will followup in less than 48 hours, most auditors and billing companies will assume you are not providing definitive care and will not code for the higher earning RVU.

Finally,  you should obtain post-reduction x-rays on any fracture that you manipulate and document that the patient is neurovascularly intact prior to discharge.

 The most common misdiagnosis in cases of missed acute MI is reflux esophagitis. Various studies have demonstrated the following factors that lead to this misdiagnosis:
1. 20% of patients with acute MI describe their pain using the words "indigestion" or "burning."
2. Almost 50% of patients with acute MI report an increase in belching during their ischemic symptoms.
3. 15% of patients get some relief of their ischemic pain with antacids and 7% of patients get complete relief of their ischemic pain with antacids.
4. 8% of patients report that their ischemic pain began while eating.

Before you ever write "Reflux esophagitis" or "GERD" on the chart of a patient you are about to send home, think twice about the possibility of acute cardiac ischemia.
 

PEDIATRIC FEVER + SEIZURE = FEVER

When a child has a fever and a seizure, do the age appropriate workup for a fever and you won't go wrong!!!

•  Therapeutic concentration considered 10-20 mg/dL
•  Some hospitals report in "mg/L" thus a level of 110 mg/L is therapeutic
•  Symptoms of Toxicity usually > 40 mg/dL
•  Consider Hemodialysis in any patient with a serum concentration >100 mg/dL

First Line Therapy:  Urine Alkalinization (pH >7.5) by administrating NaHCO3

Other Indications for Hemodialysis in Salicylate Poisoned Patient:

1. Renal Failure
2. CHF
3. Acute Lung Injury
4. Persistent CNS disturbances
5. Refractory metabolic acidosis or electrolyte abnormality
6. Hepatic insufficiency with coagulopathy

• The Sciatic Nerve is commonly injured during intramuscular buttocks injections as well as hip fracture dislocations and posterior dislocations.  In such instances, always confirm and document preserved sciatic nerve function.

• Sciatic nerve injury often results in foot drop due to decreased function of the hamstring, calf, and anterolateral lower leg muscles.

• Sciatic nerve injury may also cause loss cutaneous sensation over the calf , as well as the sole and lateral portions of the foot.

 Noninvasive Ventilation Pearls

• Multiple studies support the use of noninvasive positive pressure ventilation (NPPV) in acute exacerbations of COPD, acute cardiogenic pulmonary edema, and immunocompromised patients (organ transplant) with hypoxic respiratory failure.
• The timing of NPPV initiation is important.  NPPV should be started as soon as possible, as delays increase the likelihood of intubation
• The best predictor of success is a favorable response to NPPV within the first 1 to 2 hours
  • reduction in respiratory rate
  • improvement in pH
  • improved oxygenation
  • reduction in PaCO2
• Also crucial to NPPV success is a well fitting interface (mask)
• Although patients report greater comfort with nasal masks, they also permit more air leakage through the mouth and have been associated with a higher rate of initial intolerance in the acute setting.
• For acute applications of NPPV in the ED, a full face mask is preferred 

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Evaluating for Pulmonary Embolism During Pregnancy

Highest risk of PE is within the first week postpartum

Acceptable, safe, and medico-legally sound strategies to rule out PE in pregnancy:

• Pulmonary CTA-this strategy is safe and accepted. Plenty of data to support you if you choose this strategy. Some evidence recently that shielding the baby may actually increase scatter radiation to the fetus. Check with your Radiologist. 
• V/Q scan-also an acceptable strategy. Probably more radiation to the fetus. If you choose this test, remember that many experts recommend you insert a foley to drain the bladder (reduces radiation exposure to the fetus). 
• Negative PERC (Pulmonary Embolism Rule Out Criteria) + Negative, trimester adjusted d-dimer level. Adjusted trimester cutoffs for d-dimer in pregnancy are: 1st 750 ng/dL, 2nd 1000 ng/dL, and 3rd 1250 ng/dL. So, figure out what trimester your patient is and if they are PERC - and the d-dimer falls below the cutoff,  you are done. Remember to adjust the pulse to 105 bpm if using the PERC rule for rule out as heart rate goes up in pregnancy.
• Start with lower extremity US, if DVT +, you are done

**For explanation of PERC rule, see earlier pearl.

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The pericardium is electrically silent, and so true acute pericarditis should not be associated with ECG changes. STE actually implies concurrent involvement of the myocardium; i.e. myopericarditis. The greater the degree of myocardium involved, the more ECG changes will develop, including STE, AV blocks, and dysrhythmias. Additionally, myocardial involvement is implied by elevated troponin levels, the magnitude of which is related to the amount of myocardial involvement.

[Imazio M, Trinchero R. Myopericarditis: etiology, management, and prognosis. Int J Cardiol 2008;127:17-26.]

SCAPHOID FRACTURE:

• One of the most frequently missed fractures in the ED
• Most common carpal fracture.
• 10-20% fractures are “occult”
• Significant long-term complications:
  
  • Non-union
  • Avascular necrosis
• Complications more common due to the fact the blood supply comes form from the distal end of the bone.
• The more distal the fracture, the greater risk of complications
• MR remains the best test for occult fx.

•  Intussusception is the telescoping or prolapse of one portion of the bowel into an immediately adjacent segment.
• 90 % occur at the terminal ileum (ie, ileocolic).
• Male-to-female ratio is approximately 3:1.
• Usually seen between 5-9 months of age and 66% of all cases are in the first year of life.
• The classic triad of colicky abdominal pain, vomiting, and red currant jelly stools occurs in only 21% of cases
• Currant jelly stools are observed in only 50% of cases.
• Most patients (75%) without obviously bloody stools have stools that test positive for occult blood.
• If intussusception is strongly suspected, perform a contrast or air  enema without delay.
• Mortality with treatment is 1-3%.
• If untreated, this condition is uniformly fatal in 2-5 days.

• Metformin is the most commonly prescribed oral diabetic mediction in US
• Relative contraindication is in renally impaired patients, they are susceptible to the lactic acidosis
• Lethal adverse effect is the increase production of lactate
• ED patient with an anion gap metabolic acidosis, check for metformin and check the lactate
• The lactic acidosis is often severe (>10 mmol/L) and carries a high mortality rate that has been estimated at >40%
• Correction of pH and emergent hemodialysis are essential

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Top Reasons to call your Neurointerventionalist:

1. Vascular "blowouts" (i.e carotid tumor or trauma). 
2. Symptomatic dissections within 6 hours of onset (i.e. carotid or vertebral).
3. Ischemc Stroke with visible clot on CT angiogram outside of 3-hour IV tPA window.
4. Ischemic Stroke with visible clot on CT angiogram outside of 3-hour IV tPA window or with contraindication for tPA (i.e may be MERCI Device candidate).
5. Subarachnoid hemorrhage of aneurysmal origin.

Hypotension begins at 110 mmHg?

• Many of us use the historical SBP cut-off point of 90 mmHg or less to identify hypotension and shock
• Importantly, there is no data to support this arbitrary value
• Particularly in older patients, hypotension, hypoperfusion, and increased mortality may begin sooner than previously realized
• In this study of over 80,000 patients from the National Trauma Data Bank, a SBP < 110 mmHg was found to be more clinically relevant for identifying hypotension and hypoperfusion
• Take Home Point: strongly consider raising your threshold for identifying hypotension and initiating resuscitation, especially in the older trauma patient.

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