UMEM Educational Pearls

• Myasthenia Graves (MG) is a chronic, autoimmune disorder which causes voluntary (skeletal) muscle weakness.
• In MG, antibodies block, destroy, or alter acetylcholine receptors at the neuromuscular junction (NMJ), which impedes nerve conduction to the muscle.
• The hallmark of MG is weakness, classically of the muscles controlling bulbar function, mastication, neck movement, and facial expression, that worsens with activity and improves with rest.
• A true MG crisis ensues once respiratory muscles weaken to the point of requiring assisted ventilation. Such a medical emergency can be triggered by fever, infection, or an adverse reaction to medication.
• Edrophonium chloride (or Tensilon) can be administered intravenously to confirm the diagnosis of an MG attack. This drug increases levels of acetylcholine at the NMJ and temporarily relieves the symptoms of an MG.
• Assisted ventilation, plasmpharesis, and high dose IV immune globulin can all be used to treat an acute MG crisis.
• MG can chronically be controlled with anticholinesterase agents such as neostigmine and pyridostigmine, as well as immunosuppressives such as prednisone, cyclosporine, and azathioprine. Thymectomy is also a surgical treatment option.

Dialysis Disequilibrium Syndrome (DDS)

• Although typically seen in ESRD patients who are being initiated on hemodialysis, DDS can be seen in the critically ill
• Critically ill patients at risk for DDS include recent CVA, head trauma, subdural hematoma, hyponatremia,, hypertensive emergency, and hepatic encephalopathy
• Mild cases are characterized by restlessness, nausea, vomiting, headache, disorientation, and tremors
• More severe symptoms include seizures and coma
• The exact pathogenesis is debated but centers around acute cerebral edema
• Treatment of DDS primarily centers around manipulation of hemodialysis
• For the EP: patients with DDS presenting with seizures can be treated by rapidly increasing plasma osmolality with either hypertonic saline or mannitol (12.5 gms)  

Neutropenic Fever

A few pearls about neutropenic fever:

• Usually occurs a few weeks after chemotherapy (14-21 days)
• Defined as a fever in the setting of rapidly declining neutrophil count
• Patients who report fever at home but who are not febrile in the ED should be treated as if they are neutropenic
• ANC=absolute neutrophil count. Calculated by adding neutrophils and bands together
• Classification of neutropenia, use the ANC to calculate:  Mild: 1000-1500 cells/mm³, Moderate 500-1000 cells/mm³, and Severe Less than 500 cells/mm³.
• Mortality rate increases as the ANC drops to below 500 and the duration of neutropenia. These people die of overhwhelming bacterial infections/sepsis.
• Treatment: #1 Consider the diagnosis, #2 Broad spectrum antibiotic coverage: Imipenem, or Pip/Tazo, or Cefipime. Consider adding Vanc if the patient has a line, looks ill or is hypotensive, or if the patient has been on a fluoroquinolone.

#1 Pitfall:

• Not initiating broad spectrum antibiotic coverage fast enough. These patients can crash very rapidly.
• Patients do not have to be febrile in the ED to be diagnosed with this. Their report of fever is enough.
• Mortality rates drop the faster big gun antibiotics are given. Don't be skimpy and give Unasyn. Use the big bad boys like single agent Pip/Tazo (4.5 grams, not 3.375), Cefipime, etc. Have a low threshold for adding Vancomycin.

IDSA Guidelines on Neutropenic Fever, 2002. New Guidelines coming Summer 2008!

Pulsus paradoxus (exaggerated decrease in BP during inspiration) > 10 mm Hg is a physical exam finding that is often considered diagnostic of cardiac tamponade. The sensitivity of the finding, based on pooled studies, is actually only 82% and specificities are reported as low as 70%. In other words, the presence of the PP does not guarantee the presence of tamponade, and (more importantly) the absence of PP does not rule it out.

Conditions that can mask the presence of PP include hypotension, pericardial adhesions, aortic regurgitation, atrial septal defects, and RVH.

Conditions that can produce a PP in the absence of tamponade include severe COPD, CHF, mitral stenosis, massive PE, severe hypovolemic shock, obesity, and tense ascites.

The bottom line...when you are considering the diagnosis of tamponade, get the bedside ECHO. Don't hang your hat (and the patient's life!) on a pulsus paradoxus.

DeQuervain and Intersection Syndromes:
 

• DeQuervain's Syndrome (Tenosynovitis of the Abductor Pollicus Longus and Extensor Pollicus Brevis tendons) is a common disorder that has received a lot of press lately as BlackBerry Thumb or Gamer's Thumb.
  • This condition can be diagnosised by the Finklestein test [Have the patient bend their thumb into the palm of their hand, and then make a fist.  They should then ulnar deviate their wrist.  Pain along the tendons secures the diagnosis.]
  • The pain of DeQuervain's syndrome is typically along the distal end of the radius at the base of the thumb.
• Intersection syndrome is a less common disorder though closely related to DeQuervain's Syndrome
  • The pain is usually felt on the top of the forearm about three inches proximal to the wrist. 
  • The pain from this condition is due to tenosynovitis of the Extensor carpi radialis longus and Extensor Carpi radialis brevis muscles/tendons caused by the intersection of them with the Extensor pollicus brevis and Abductor pollicus longus tendons.
  • Occurs due to excessive wrist movements.
  • Intersection syndrome can be seen in weight lifters, skiers, and can be seen in homeowners in the fall and winter when they rake a lot of leaves or shovel snow.
• Treatment is the similar for both conditions and consists of:
  • NSAIDS
  • Cortisone injections can be effective
  • Thumb and wrist immobilization with a Thumb Spica Splint or Cock Up Wrist Splint
     

Hypertension

• Normative BP values are based on Age, Sex, and Height (check Harriet-Lane).
• BP should be measured in all children >3yrs and in selected children <3yrs.

• The younger the child and the higher the BP, the more likely there is a secondary cause. 
• Most common secondary causes:
  • 1st year of life: RenoVascular anomalies and aortic coarctation.
  • Early childhood/school-aged kids: Renal Parenchymal Disease
  • Adolescents: Essential hypertension

• 25% of children that present with HTN requiring emergent management present with hypertensive encephalopathy (ie.  it is a more common presentation of HTN in pediatrics than in adults).
• Initial Work-up:
  • Upper and Lower Extremity BP measurement
  • BMP and U/A – look for renal disease
  • CBC – microangiopathic process c/w HUS?
    
    
     

Show References

There is actually very little data that actually supports the administration of activated charcoal (AC) to the poisoned patient.  AC works by binding the toxin and preventing its absorption from the GI tract. Here are some of the practical points:

• Most effective if given within one hour of the overdose
• Do not give if patient is sedated, going to be sedated or has a chance for seizure
• Always assess risk of aspiration versus possibly binding drug by asking the following:

1. Is this drug dangerous enough that I have to try to prevent its absorption?
2. Can this drug cause sedation, seizures or impair protective airway reflexes?
3. Do I lack an antidote or alternative treatment?

Once you have assessed your risk:benefit ratio, then administer AC. Of note, it definitely works in the right situation as noted in a landmark article that showed a decrease in mortality following poisoning by oleander - a plant that contains a digoxin like substance.(1)

1 - de Silva HA, et al. Multiple-dose activated charcoal for treatment of yellow oleander poisoning: a single-blind, randomised, placebo-controlled trial. Lancet 2003: 361(9373):1935-8.

• Animal models have shown that neuroprotectants, including free radical trapping agents, decrease injury after ischemic stroke.

• NXY-059 is a promising neuroprotective agent that was studied in the SAINT I and II trials.

• SAINT I showed that NXY-059 used within 6 hours of ischemic stroke resulted in significant improvement in the primary outcome measure of reduced disability at 90 days.

• SAINT II was done to confirm the results of SAINT I with a larger study population, but unfortunately did not show any significant difference in mortality between NXY-059 and placebo.  There was also no difference in adverse reactions, however.

• More research is needed to determine the best neuroprotective agent to be used acutely for ischemic stroke.

• The future of emergency treatment of ischemic stroke will likely include such agents, to be administered by emergency physicians.

Treatment of Pulmonary Embolism

Treatment of acute PE:

• Unfractionated Heparin (80 units/kg intravenous bolus followed by 18 units/kg/hour) or,
• Fractionated (i.e. low molecular weight heparin) Heparin. For example, Enoxaparin, in a dose of 1 mg/kg subcutaneously every 12 hours. Some also give this dose IV every 12 hours.

If administering thrombolytic therapy (currently tPA is the only FDA approved drug) for massive PE, most authorities recommend UFH (Unfractionated Heparin) because the infusion needs to be turned off while the tPA hangs for 2 hours.

Although other agents are being promoted for the treatment of acute PE, like direct thrombin inhibitors, many institutions do not have these drugs available yet. Plus, they are expensive and have not been shown to be superior to standard therapy (at least yet)

References: Kline, Journal of Thrombosis and Hemostasis, 2005, 2006, 2007

Guidewire length for central venous catheterization

• 18 cm should be considered the upper limit of guidewire insertion during internal jugular or subclavian central venous catheterization (16cm for right IJ)
• There is the Peres Nomogram for determining guidewire length, which is based on patient height
• However, height is less reliable in predicting safe guidewire length

Sternoclavicular Dislocation:

• A rare cause of chest/shoulder pain following trauma, but one that can be associated with serious vascular injuries.
• Anterior dislocations of the Sternoclavicular(SC) Joint are much more common  than posterior and  usually resulting from  blow to the anterior shoulder that rotates the shoulder backward and transmits the stress to the medial clavicle and SC joint.
• A blow to the posteior shoulder that drives the shoulder forward or a direct blow to the medial clavicle can cause a posterior dislocation.
• Anterior SC dislocations
  
  • Generally not associated with any underlying injury and can be safely reduced in the ED. 
  • Ligaments and joint capsule entrapment can make it difficult to reduce the joint, and often it is difficult to maintain the reduction. 
  • It is not uncommon for these to require open reducation and internal fixation.
  • Can be reducted by abducting, extending, and applying traction to the ipsilateral arm/shoulder while applying posterior and inferior pressure on the medial clavicle.
• Posterior SC dislocations
  
  • Rare
  • Associated with injuries to the underlying vasculature,  dyspnea due to tracheal compression, and parasthesias.
  • Often missed on plain films (CXR, Shoulder Series or Clavicular Series)
  • Best visualized with enhanced CT Scan of the Chest.  IV enhancement recommended to ensure that their is no associated vascular injury.
  • Can be reducted by abducting, extending, and applying traction to the ipsilateral arm/shoulder while pulling the clavicle forward.  Several references recommend using a towel clip to grasp the clavicle if you are unable to grab it effectively with your fingers. 

Sorry this is being delivered to you late.

Here's a nice, simple pearl for cardiogenic shock:
"A normal ECG virtually rules out shock due to myocardial infarction."

Essentially, even though MI may be associated with a normal ECG in approximately 5-8% of cases, if a patient has cardiogenic shock due to MI, the ECG will ALWAYS be abnormal.

Gowda RM, Fox JT, Khan IA. Cardiogenic shock: basics and  clinical considerations. Int J Cardiol 2008;123:221-228.

Amal

Diarrhea and the Petting Zoo

Now that it is Spring Time, trips to the Zoo and to Pools will become more frequent… consider them as potential environmental exposure sites.

Petting Zoos, Farmers Markets and Fairs, and Swimming Pools (especially kiddie swimming pools) are known sources of enteropathogens that can cause diarrhea (sometimes bloody).

• Salmonella (turtles, baby chicks)
• E. Coli (newborn calves)
• Cryptosporidium (farm animals and swimming pools – it is chlorine resistant)

Consider these on your DDx of vomiting/diarrhea.

Ask about these possible exposure sites along with Travel History and Nontraditional Pets.

Heparin FDA Alert

In case you had not heard, there was a major recall of Baxter's Heparin. It was responsible for dozens of deaths in the USA and an investigation was launched. It has been found that the contaminant comes from manufacturing plants in China. The most concerning part is that it looks like it was chemically synthesized sulfated chondroitin. This brings the suspicion of intentional adulteration. First lead in toys now cartilage in our heparin - what's next?

Some fascinomas of Heparin:

• Overdose of heparin is treated with either time or protamine
• Protamine can actually worsen anticoagulation if you give too much
• Dose of Protamine: 1 mg of Protamine neutralizes 90 USP Units of Heparin but you must cut dose in half if 30 minutes have passed from heparin dose

News link for FDA Heparin Alert:

http://www.fda.gov/medwAtch/safety/2008/safety08.htm#HeparinInj2

• The risk of symptomatic intracerebral hemorrhage after use of IV tPA for acute stroke is 6% (within 36 hours of administration).

The NINDS tPA Stroke Study Group.  "Intracerebral Hemorrhage after Administration of Intravenous tPA for Ischemic Stroke."  Stroke.  1997; 28:  2109-18.

Potassium Phosphate ("K-phos")

Over the weekend, I had a patient with Dr. Scott that had a phosphate of 0.8 mmol/L.  Phosphate < 1.0 mmol/L is an indication for IV repletion.  IV repletion involves giving potassium phosphate.  An important clinical question, therefore, is how much potassium does the patient actually get?

• 1 mmol of IV phosphate delivers 1.46 mEq of potassium
• Recommended infusion rate is 5 mmol/hr
• Rapid infusion may lead to severe hypocalcemia, hypotension, acute renal failure, hypomagnesemia, and hypernatremia

Cardiogenic shock associated with LV outflow obstruction is managed best without the use of vasoconstrictive agents and vasopressors. Ideally, patients should be treated with IVF and beta blockade. Alpha agonists (e.g. ISO) can also be added.

Typical vasopressors may actually worsen LV outflow obstruction in these patients.

Dental Emergency -- Avulsed Tooth

• Never reimpant a primary tooth.  If replaced, primary teeth have a high likelihood of fusing to underlying alveolar bone, which causes dentoalveolar ankylosis and can result in facial deformities
• Never wipe off a tooth, or hold it by the root. The periodontal ligament is easily wiped off and the tooth will not reimplant without it.
• For maximal success, the tooth should be reimplanted within 60 minutes.
• Avoid allowing the periodontal ligament from drying out.  Transport the tooth in (listed in order of preference):
  • Hanks Solution or EMT Tooth Saver
  • Milk
  • Saline
  • Saliva
• Once the tooth is reimplanted it should be held in place with a wire splint or Coe-Pak that bridges the avulsed tooth to the ones on either side of it.
• Place the patient on antibiotics (Penicillin or Clindamycin) in order to prevent any infections.
• If the avulsed tooth can not be found a Chest X-ray should be obtained to ensure that the tooth was not aspirated.

Sexual Abuse

• The only positive vaginal culture that is DEFINITIVE confirmation of sexual abuse is Neisseria gonorrhea.
  • Vertically transmitted Chlamydia may persist for up to 3 years (does not confirm abuse in children <3yrs)
  • Syphilis may also be present due to vertical transmission (often presents as secondary syphilis)
  • Trichomonas can also be transmitted perinatally and may persist for 6-9 months. 
    • However, it has NOT been found in children >1 year without history of sexual contact.

• Remember that CULTURES need to be sent for GC and Chlamydia.  DNA probes and nonculture methods are NOT recommended in this age group for evaluation of potential sexual abuse.
   

• A triptan that is a serotonin agonist
• SQ administration better
• High first pass effect and thus not effective often PO
• Sulfhemoglobinemia see with high dose PO
• Adverse Effects: MI and ischemia , CVA
• Be wary with elderly, hx of CAD/CVA or hx of cocaine use