UMEM Educational Pearls

• 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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• 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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Acute Mesenteric Ischemia

Although we all know the classic presentation of acute mesenteric ischemia (AMI), it can be tough to diagnose.

Some pearls about AMI:

• Embolization to the superior mesenteric artery (SMA) is the most frequent cause of AMI.
• Most patients present with acute, severe abdominal pain. 
• Classic presentation: acute severe abdominal pain with a paucity of physical examination findings
• Presence of tenderness in most cases indicates bowel infarction has already occurred
• The disease may be more insidious in patients with diseased mesenteric vessels (presence of collaterals). These patients may very well NOT present with acute, severe pain.
• Must have a high index of suspicion (i.e.-suspect this disease in patients at risk who present with abdominal pain)
• If you are standing at the bedside and you say, "Self, this looks like AMI," then rally the troops BEFORE labs and before CT. Get a surgeon to see the patient as soon as possible. Tell them you think the patient has AMI. Get them to move. "TIme is bowel."

Three groups of patients are at especially high risk of bleeding from excessive anticoagulation with renally-excreted medications: women, the elderly, and patients with chronic renal insufficiency. For all of these patients, ALWAYS dose their renally-cleared medications based on creatinine clearance, NOT just the creatinine.

Which medications in ACS does this apply to?--enoxaparin and G2B3A inhibitors are the most prominent here to consider.

The literature not only demonstrates increased bleeding complications but also increased MORTALITY if you don't dose based on creatinine clearance!

Review of the Appearance of Ossification Centers in Children's Elbows

Determing if a child's elbow has a fracture or if you are looking at an ossification center is easier if you remember the mnemonic CRITOE.  This is the order that the ossification centers appear:

• Capitellum 1 to 8 months
• Radial Head 3 to 5 years
• Internal (medial) Epicondyle 5 to 7 years
• Trochlea 7 to 9 years
• Olecranon 8 to 11 years
• External (Lateral) Epicondyle 11 to 14 yeras

• the most common cause of stridor in the newborn
• the laryngeal skeleton is not stiff enough to resist the negative pressure during inspiration causing narrowing and stridor
• can occur at birth but most commonly seen at 2 weeks of age, and is more pronounced with agitation
• for most, close observation is sufficient as the cartilage becomes more rigid with age
• usually outgrown by 12-18 months of age
• in severe cases, feeding may be affected and nighttime obstructive hypoxia may occur

• Etiologic causes of hearing loss can be categorized into three groups:  (1) Sensorineural, (2) Conductive, and (3) Sensorineural and Conducitve.
• Sensorineural hearing loss results from problems with the vestibulocochlear nerve (cranial nerve VIII), inner ear, or central processing centers of the brain.
• When performing the Weber Test on patients with sensorineural hearing loss (tuning fork touched to midline of skull), sound localizes to the normal ear (i.e. sound conducts normally through bone, which measures sensorineural function, on the side without the abnormality).
• Examples of conditions that cause sensorineural hearing loss include:  Acoustic neuroma and other cerebellopontine angle tumors, perilymph fistula, noise trauma, and ototoxic medications.     

Catheter-related bloodstream infections occur in 3-8 percent of insertions, and are the highest cause of nosocomial bloodstream infections in the ICU. 

The most effective measures to prevent catheter-related infections are as follows:

Especially applicable to those of us placing these lines in the ED or in the ICU is the last recommendation, based on a prospective study from Greece

-adequate knowledge and use of care protocols

-qualified personnel involved in changing and care

-use of biomaterials that inhibit microorganism growth and adhesion

-good hand hygiene

-use of an alcoholic formulation of chlorhexidine for skin disinfection and manipulation of the vascular line

-preference for subclavian route for placement

-use of full barrier protection during placement

-removal of unnecessary catheters

-use of ultrasound for placement of central lines

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Complications of Liver Biopsy

Some considerations for the patient who presents with pain after a liver biopsy:

• Hemothorax
• Pneumothorax
• Biopsy of other organ
• Hemorrhage (subcapsular hematoma, intraperitoneal bleeding, hemobilia)
• AV Fistula

Consider getting a chest xray and a RUQ ultrasound to evaluate for these complications if they show up in the ED. CT scanning might also be required.

Also consider getting Interventional Radiology  involved early in cases of bleeding as this is often the preferred treatment for biopsy site bleeding. In addition, a surgical consult is wise

in case the patient requires operative intervention. 

Although supplemental oxygen has long been considered standard care for patients with ACS, the evidence supporting this concept is largely based on animal studies in which acute MI was artificially induced. Should these studies be extrapolated to humans? Maybe not....


Further review of the animal and human literature actually indicates that the routine use of supplemental oxygen and induction of hyperoxia can actually induce adverse hemodynamic consequences such as increased coronary artery tone and reduction in coronary artery blood flow; reductions in cardiac output and increased systemic vascular resistance; and potentially increased infarction size. It certainly seems prudent to treat hypoxia, but if the patient is not hypoxic, skip the supplemental oxygen!

Wijesinghe M, et al. Routine use of oxygen in the treatment of myocardial infarction: systematic review. Heart 2009;95:198-202.
AND
Farquhar H, et al. Systematic review of studies of the effect of hyperoxia on coronary blood flow. Am Heart J 2009;158:371-377.