UMEM Educational Pearls

• The Brachial Plexus is a bundle of nerve roots arising from C5, C6, C7, C8, and T1.
• Brachial plexus injuries (BPI) result from severe traction forces on the limb.
• The most common sources of BPI are motorcycle accidents and birth palsy (i.e. Erb or Duchenne Palsy) affecting the upper part of the plexus (C5, C6) and causing shoulder and biceps muscle weakness.
• Injury to C7 >>> wrist weakness.
• Injury to C8 and T1 >>>  forearm and intrinsic hand muscle weakness.
• Injury to stellate ganglion or cervical sympathetic trunk >>> Horner's Syndrome.
• MRI of the upper extremity is the standard imaging modality used to make the diagnosis.

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It is true, 1/3 of Americans are obese.  There is conflicting evidence regarding the mortality risk of obesity (defined as BMI>30 kg/m²) in critically ill patients. 

It has been shown that abdominal fat has greater consequences than peripheral obesity, and based on this, a recent study has utilized the sagittal abdominal diameter (SAD) in ICU patients to show that abdominal obesity (as differentiated from BMI) poses an independent risk of death.  The SAD detects visceral fat, which has been shown to have metabolic and immune health consequences, including the following:

-incidence and severity of certain infections is higher

-excess adipocytes are associated with elevated levels of proinflammatory factors that favor insulin resistance, diabetes, dyslipidemia and hypertension, all of which lead to microcirculatory dysfunction

-rates of required renal replacement therapy and abdominal compartment syndrome correlate to increased SAD

-there is also a trend toward a longer length of ventilator weaning

See you at the gym.

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Secondary Hypertension...say what?

We obviously see tons of patients in the ED with hypertension, and we are very comfortable with both symptomatic and asymptomatic presentations. Most of these patients have essential or primary hypertension. Some patients, however, may have secondary hypertension (i.e. something is causing it). Although we will refer patients to a primary care physician for further management and workup it is worth discussing when to suspect other diagnoses as the cause of the hypertension. Is it out job necessarily to diagnose these conditions in the ED? No. 

Causes of secondary hypertension to consider:

• Obstructive sleep apnea
• Renal disease
• Renal artery stenosis (think older person with HTN and abdominal bruit)
• Coarctation (young person with HTN-ever wonder why pediatricians palpate upper and lower extremity pulses in the office?)
• Cushing's disease (excess cortisol-patient may have new diabetes, have abdominal striae, and easy bruising)
• Hyperaldosteronism (due to an adrenal tumor)...think about if a patient comes to the ED and is repeatedly hypokalemic and hypertensive
• Pheochromocytoma (episodes of flushing, hypertension, palpitations, etc.)
• Hypothyroidism (not myxedema coma or storm)...commonly causes elevated diastolic BP. 
• Hyperthyroidism 

Consider the ABCDE mnemonic:

A-Accuracy (is it really htn?), Apnea, Aldosteronism

B-Bruits, Bad Kidneys

C-Catecholamines, Coarctation, Cushing's 

D-Drugs, Diet

E-Endocrine

Aren't you glad you didn't do a Medicine residency???

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Patients with pericarditis are generally treated with high-dose aspirin (e.g. 2-4 gms/day) or other NSAIDs in high dose. However, when myocarditis is also present (e.g. elevated TN levels), lower dosages of aspirin (e.g. 500 mg TID) or other NSAIDS should be used. The higher dosages of anti-inflammatory medications in the setting of myocarditis are thought to exacerbate the myocarditic process and increase mortality (animal studies).

Imazio M, Spodick DH, Brucato A, et al. Controversial Issues in the management of pericardial diseases. Circulation 2010;121:916-928.

All to often we see children that are sent to the ED for "Pink Eye" as the school nurse will not allow them back into class unless they are treated with antibiotics.  A recent study out of New York identified 4 factors that are associated with low risk (<8% chance) of bacterial (culture postive) conjunctivitis.  They are:

1. age 6 years
2. presentation during April through November
3. watery or no discharge
4. no glued eye in the morning

An editorial in journal watch comments that if this study can be replicated in other geographic areas we could change the practice of prescribing antibiotics that are not necessary.

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EMTALA stipulates that any patient presenting to the Emergency Department is required to receive a medical screening exam regardless of age, ability to pay, or whether or not a parent accompanies the child.

EMTALA supersedes any state/local provisions or laws.

In performing a medical screening exam if an emergency medical condition exists then diagnostic testing, surgery or even transfer of hospitals may be appropriate without ever obtaining parental consent

MInors have the right to give or refuse informed assent of a procedure

If their is conflict between physician, parent or patient in the rendering of emergent care the physician must weigh the severity of the condition, risks and benefits of the treatment, as well as the patients maturity and cognition.  The physician may have to seek ethical committee review, or assistance from either social services or the court system.

If an emergent condition does not exist, EMTALA does not apply after the MSE.

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• Cerebral edema develops in 20-90% of children with DKA, and mortality ranges from 20-90%
• Children younger than 5, and with newly diagnosed diabetes are at higher risk, and the risk in children in general is MUCH higher than the risk in adults
• Cerebral edema usually results from osmolarity changes during treatment, but may precede treatment
• Limit fluid repletion to isotonic fluids (Normal Saline), at a rate of no faster than 10-20 mL/kg/hr (In shock, resuscitate as usual)
• Head CT Is of limited value as the majority of children in DKA may show signs of subclinical cerebral edema, TREAT BASED ON CLINICAL SIGNS, and do not delay treatment for head CT which is likely to be abnormal in ALL kids
• Bicarb is implicated in increasing the risk of cerebral edema - focus on correction of acidosis with insulin and appropriate fluids, NOT bicarb

...more to come.

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Several drugs and compounds may be radiopaque on an abdominal radiograph. This may be helpful in an overdose to determine ingestion or amount ingested. Attached is a pic a patient that ingested potassium sustained release tables.

The mneumonic CHIPES will help you remember which are:

C - Calcium Carbonate, chloral hydrate

H - Heavy metal - like Mercury, lead

I - Iron and Iodine

P - Phenothiazines (compound that has S(C₆H₄)₂NH in it), drugs that include: antipsychotics like chlorpromazine (thorazine) and antiemetics like prochlorperazine (compazine)

E - Enteric coated pills

S - Solvents [halogenated ones like chloroform] and Sustained Release preparations [Lithobid and K-Dur]

Attachments

1004150936_KCl_patient_1.JPG (182 Kb)

• Bitemporal hemianopsia ("tunnel vision") is a type partial blindness affecting the lateral halves of vision in both eyes (see attached diagram), and is usually associated with lesions or compression of the optic chiasm.
• Always assess visual fields in patients presenting with neurologic complaints, particularly when associated with visual abnormality, headache, focal deficit, and endocrine-related symptoms.
• One of the simplest ways of assessing visual fields is to (1) stand directly in front of the patient, (2) instruct them to stare straight at your nose, (3) laterally extend both your arms to 2/3 of full capacity (i.e. elbows slightly bent), and (4) ask them where they see your wiggling fingers (i.e. left or right).  
• Bitemporal hemianopsia commonly results from pituitary microadenomas (< 1 cm) and macroadenomas (> 1 cm), which are sometimes associated with acromegaly and Cushing's Disease.

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Attachments

1004140823_Visual_Field_Abnormalities.jpg (44 Kb)

Type B Lactic Acidosis

• In the critically ill, patients may often have elevated lactate levels without ongoing tissue hypoperfusion.
• In these patients it is important to consider the causes of what is referred to as "Type B Lactic Acidosis".
• Pertinent to critically ill ED patients, consider the following:
  • Type B1 - related to underlying disease
    • renal faiilure
    • hepatic failure
    • malignancy
    • HIV
  • Type B2 - effects of drugs/toxins
    • acetaminophen
    • alcohols
    • beta-adrenergic agents: epinephrine
    • cocaine, methamphetamine
    • propofol
    • salicylates
    • valproic acid
    • metformin
  • Type B3 - inborn errors of metabolism

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Though most causes of acute pericarditis in patients from developed countries are viral or idiopathic, the etiology of pericarditis in patients visiting from developing countries is usually TB, and the TB accounts for > 90% of cases of pericarditis in patients with HIV infection. This group of patients, therefore, should almost always be admitted for a full workup of the cause and for appropriate treatment.

Prosthetic hip dislocations are a common occurance in the Emergency Department.  After you have gotten the hip back in place there are several ways to prevent the hip from coming out again.  An abductor pillow will work but it confines the patient to bed.  A better option to prevent further hip dislocations until the patient can get an appropriate brace made or reparative surgery is to place the patient in a straight leg knee immoblizer. It is nearly impossible to dislocate your hip if your knee is fully extended.

So after reduction of their simple hip dislocation (i.e: no fractures) place the patient in a straight leg knee immobolizer and they can followup with their orthopedist as an outpatient.

Many drugs/toxins cause nystagmus, particularly in overdose.  Vertical, horizontal, or rotary nystagmus may be noted.

The most common drug/toxin overdoses that cause nystagmus are the following:

• Anticonvulsants (phenytoin, carbamazepine, valproic acid, lamotrigine, topiramate)
• Ethanol
• Lithium
• Dextromethorphan
• Phencyclidine (PCP)
• Ketamine
• Lysergic acid diethylamide (LSD)

• Nonspecific brain atrophy is a common finding on Head CT's, sometimes without any clearly articulated clinical significance for the emergency physician.
• Generally speaking, brain atrophy is the manifestation of the effects of atherosclerosis.
• Radiographically, it typically presents as widened sulci and dilated ventricles.
• In patients with vague mental status abnormalities and limited access to medical history, consider the following brain atrophy clues in your management:

              --  Multiple areas of local cortical brain atrophy (wedge-shaped

                   appearance) suggests multi-infarct dementia.

              --  Disproportionate atrophy in the frontal and temporal lobes may be a 

                   sign of Alzheimer's Disease.

Magnesium depletion has been described as "the most underdiagnosed electrolyte abnormality in current medical practice"

Important for electrically excitable tissues and smooth muscle cells, Mg is mostly located in bone, muscle and soft tissue.  Because only 1% is located in blood, your patient can be Mg depleted with normal serum levels. 

65% of ICU patients are magnesium depleted (and may not be hypomagnesemic). Because labs are unreliable, consider predisposing causes, such as diuretics, antibiotics (aminoglycosides, amphotericin), digitalis, diarrhea, chronic alcohol abuse, diabetes and acute MI (80% of AMI patients will have magnesium depletion in the first 48 hours). 

Mg depletion is typically accompanied by depletion of other electrolytes (K, Phos, Ca), and can cause arrhythmias (especially torsades) and promote digitalis cardiotoxicity. 

Hypermagnesemia is less common, and can be caused by hemolysis, renal insufficiency, DKA, adrenal insufficiency and lithium toxicity.  Clinical findings include hyporeflexia, prolonged AV conduction, heart block and cardiac arrest.  Treatment includes fluid and furosemide, calcium gluconate and dialysis. 

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Some not too uncommon complications of Type B (distal) aortic dissection:

• Malperfusion syndrome-occurs when the dissection flap occludes a major vessel (e.g. SMA occlusion leading to bowel infarction)
• Occlusion of the spinal arteries and lower extremity arteries can lead to fleeting signs and symptoms-one minute they have left leg pain and ischemia, the next minute they don't. This is pretty classic for acute, distal aortic dissection. 
• Frank rupture (dissected aortic wall is weak and prone to aneurysm formation and subsequent rupture)
• Assume that rupture has occurred (may be intrathoracic or intrabdominal) in a Type B patient who crashes unexpectedly
• Retrograde extension into the proximal aorta is not common but does occur. Have a low threshold to whip out the sono if the patient deteriorates. 

When prescribing quinolones to elderly (e.g. for UTI) patients that are taking iron supplements, advise them to take the antibiotic several hours before taking the iron. Iron will bind the antibiotic in the GI tract and reduce its bioavailability.

[Anderson RS, Liang SY. Infections in elderly patients. Critical Decisions in Emergency Medicine, 2010;24(8):13-18.]

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• The thalamus is a major relay center of the brain locaed between the cerebral cortex and the midbrain.
• It regulates motor and sensory function as well as sleeping and waking states. 
• It is supplied by 4 arterial systems (3 from the vertebrobasilar system; 1 from the posterior communicating system) such that strokes within these territories result in 4 distinct clinical syndromes, including syndromes consisting of pure sensory, arousal, and memory deficits.
• Thalamic strokes are thought to be more common in young people, associated with smoking and hypertension, and of poorer prognosis when presented with loss of consciousness.

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Ventilator Pearls for H1N1 Influenza Virus

• As the spring/summer travel season begins, it is predicted that we will see additional cases of H1N1
• The most common presentation requiring ICU admission to date has been a viral pneumonitis
• As highlighted in previous pearls, the hallmark of disease has been refractory hypoxemia requiring mechanical ventilation in about 85% of patients.
• Current recommendations for H1N1 respiratory failure:
  • Consider early intubation
  • Noninvasive ventilation has been unsuccessful in most and should generally be avoided
  • Low tidal volume settings (6 ml/kg) with PEEP based on F_iO₂ to maintain S_pO₂ > 88% and plateau pressure < 35 cm H₂O
  • Although there is no proven mortality benefit to rescue therapies such as recruitment maneuvers, neuromuscular blockade, and prone ventilation, these can be considered in discussion with your intensivist.

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