UMEM Educational Pearls

This week's monday pearl is from our very own Azher Merchant....who recently gave an excellent talk on the risks of radiation.

Be afraid....be very afraid....

Radiation Risk:
Risk is based on acute exposure and is extrapolated largely from atomic bomb survivors.
Effective radiation dose = Sievert (Sv)

Adults:
Lifetime Attributable Risk of Cancer 1:1000 at 10mSv
Lifetime Attributable Risk of Cancer Mortality 1:2000 at 10mSv
 
Risk estimates follow a linear rate of change such that:
Lifetime Attributable Risk of Cancer in Adults = Radiation Dose (mSv) x 0.0001
Risk is Cumulative

Pediatrics:
Lifetime Attributable Risk of Cancer is greater than for adults and is age-dependent
Lifetime Attributable Risk of Cancer Mortality 1:1000 at 10mSv

Common Effective Dose Estimates (mSv)

Background radiation                     3.5/year (chronic exposure)
CXR                                             0.1
CT
    Head, Face                               2
    Neck, Cervical Spine                 2
    Chest, Thoracic Spine                8
    Abdomen                                7.5
    Pelvis                                     7.5
    Abdomen/Pelvis, Lumbar Spine 15
    Extremity                               0.5
 

Note that it doesn't take very much radiation to reach the 10 mSv level!

Bottom line: CT if you need to, but carefully consider whether it is worth it or not

One last pearl, carefully consider whether or not you want that d-dimer and don't order one unless you are prepared to order a CT scan.

The most common cause of delirium in the elderly is infection, and the most common type of infection is just a simple UTI. The second most common cause of delirium is medication effects. ALWAYS look carefully for signs of infection and look carefully at medication lists whenever evaluating an elderly patient with a change in mental status.

Medical Treatment of Hyperparathyroidism

• Hyperthyroidism will typically only need to be treated in the Emergency Department when they present with Hypercalcemia. 
• Outpatient management of hyperthyroidism consists of serial PTH measurements, Calcium, and Creatinine.
• Hypercalcemia should be treated with normal saline hydration. 
  • Once the patient is determined to be euvolemic you can enhance diuresis and excretion of calcium by giving the patient furosemide. 
  • Remember hydrochlorathiazide can actually increase serum calcium by preventing its excretion.
  • This patients should receive 4-10 liters of normal saline in the first day.
  • You can also give bisphosphonates and calcitonin. 
  • For high calcium levels with mental status changes consider hemodialysis.

Infantile Spasms (West Syndrome):

• Are brief contractions of the neck, trunk, arm, and leg muscles that last 2-10 seconds
• Are NOT seizures, but 86% of children with infantile spasms go on to develop a seizure disorder before 1 year of age
• Usually occur as the child is going to sleep or waking up
• Most commonly seen between 3 and 8 months of age
• Often mistakenly diagnosed as colic
• Poor prognosis as infantile spasms usually indicate an underlying genetic, metabolic, or developmental abnormality

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WBI: whole bowel irrigation

Reminder from Poisondex:

OVERDOSE: SEVERE: Stupor, shock, acidosis, GI bleed, coagulopathy, hepatotoxicity, and coma. MILD/MODERATE: Nausea, vomiting, diarrhea, lethargy, leukocytosis, and hyperglycemia. Clinical phases: (1) 0-2 hours: Nausea, vomiting, diarrhea, and abdominal pain. Lethargy, shock, GI bleeding, and acidosis if severe; (2) Apparent recovery; (3) 2-12 hours: Acidosis, hypotension; (4) 2-4 days: Hepatotoxicity; (5) days-weeks: GI strictures.

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• The therapeutic ranges for phenytoin (dilantin) and phenobarbital in adults are 10 to 20 mcg/mL and 10 to 30 mcg/mL, respectively.

• Phenytoin plasma levels rise more rapidly than phenobarbital levels; therefore, an acute overdose of the two together will likely manifest as phenytoin toxicity before phenobarbital toxicity.

• Phenytoin has a more narrow margin between therapeutic and toxic levels than does phenobarbital.

The Supraclavicular Subclavian Central Venous Cathetherization

• Central venous catheters (CVCs) are routinely placed in critically ill ED patients.
• The literature has clearly demonstrated that CVCs placed in the subclavian vein have lower risks of infection and thrombosis when compared to the femoral and internal jugular vein routes.
• Although we routinely teach the infraclavicular approach, don't forget the subclavian vein can also be cannulated via the supraclavicular approach.
• Some pearls on the supraclavicular approach:
  • Identify the clavisternomastoid angle: formed by the lateral head of the sternocleidomastoid muscle (SCM) and the clavicle
  • Insert the needle 1 cm lateral to the lateral head of the SCM and 1 cm posterior to the clavicle
  • Direct the needle at a 45-degree angle aimed at the contralateral nipple
  • The right side is preferred due to a more direct route to the SVC and a lower pleural dome (decreasing the incidence of pneumothorax)
  • Place the patient in Trendelenburg position and aim the bevel of the needle downward

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Painless thoracic aortic dissection (TAD) and syncope

Patients with TAD do not always present with chest pain. In the International Registry of Aortic Dissection (IRAD) study, 2.2% of TAD cases were painless and approximately 13% of TAD cases presented with isolated syncope (i.e. NO PAIN). Other studies have shown that as many as 15% of TAD cases are painless.

Patients with TAD may present after a syncopal episode. The underlying pathophysiology of syncope is related to proximal rupture into the pericardium with resultant tamponade.

Add TAD to your differential diagnosis of unexplained syncope, especially in older folks and especially if a patient "looks bad" and you don't have a reason.

When caring for elderly patients that are having dysrhythmias, especially ventricular dysrhythmias, or in cardiac arrest, give strong consideration to empiric use of magnesium. Elderly patients are more likely to be hypomagnesemic because of diuretic use, poor GI absorption, poor daily intake, and diabetes.

[Narang AT, Sikka R. Resuscitation of the elderly. Emerg Med Clin N Am 2006;24:261-272.]

Hyperparathyroidism results in elevated PTH and typically results in elevated calcium levels (hypercalcemia). 

• Primary hyperthryoidism is due to hyperfunction of the parathyroid glands, while secondary hyperthyroidism is a reaction of the parathyroid glands to hypocalcemia caused by another etiology, most commonly chronic renal failure. 
• Tertiary hyperthyroidism is due to hyperplasia of the parathyroid glands due to loss of response to serum calcium levels and this too is seen in chronic renal failure

Though most cases are asymptomatic, symptomatic patients can present with:

• weakness and fatigue
• depression
• aches and pains
• decreased appetitie
• constipation
• polyuria and polydipsia
• kidney stones
• osteoporosis.

Treatment options to be discussed next week....Stay tuned.

 Valproic Acid (Depakote)

• Can cause carnitine deficiency
• In overdose and therapeutic ingestions can cause hepatic enzyme elevation (idiosyncratic) but can also cause hyperammonemia without hepatic enyme elevation
• Have a patient with somnolence or altered mental status and is on valproic acid - check a level but also check an ammonia level
• Elevated ammonia levels can be treated with an antidote - carnitine (IV or PO)
• Very safe antidote (carnitine) since it is a nutritional supplement, consider in patients on valproic acid and decreased responsivness with elevated ammonia

• Status epilepticus is defined as either a continuous convulsion or serial convulsions without loss of consciousness that lasts 30 minutes.
• First line treatment:  benzodiazepine because it is absorbed rapidly into the nervous system; lorazepam (0.05 to 0.1 mg/kg) is preferred over diazepam (0.2 to 0.5 mg/kg) because of its longer half-life in the CNS; rectal administration of the intravenous formulation or the commercially available gel at the same doses may be subsitutued if no IV is attainable.
• if seizure activity persists beyond 10 - 15 min, a longer acting anticonvulsant such as phenytoin (18 -20 mg/kg), fosphenytoin, or phenobarbital (18 - 20 mg/kg) is administered; they take longer to penetrate the CNS, but have much longer half-lives than the benzodiazepines.  Phenobarbital is given to infants while phenytoin or fosphenytoin is given to older children.
• Fosphenytoin, a prodrug to phenytoin, increasingly is replacing phenytoin as the drug of choice.  It can be administered at two to three times the rate of phenytoin and is less caustic to skin in teh event of vein extravasation.  It can als be given intramuscularly, while phenytoin can't.

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• Glucose abnormalities and hyponatremia are the two laboratory findings most frequently associated with triggering first-time seizures in adult patients.

• Always check an HCG in women who present with their first seizure, as this may reveal the source (i.e. eclampsia) and/or may affect testing, disposition, and initiation of an anti-epileptic drug (AED).

• Drug abuse screens should be considered in patients with their first seizure, but no prospective studies have demonstrated benefit from routine use.

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Pulse Pressure Variation and Volume Responsiveness

• Assessing volume status in the critically ill is extremely challenging, as up to 50% of patients do not respond to a fluid challenge (i.e. increase their stroke volume/cardiac output with additional IVFs).
• As highlighted in previous pearls, traditional measurements such as blood pressure, heart rate, and urine output are extremely variable and inaccurate in determining volume status.
• Pulse pressure variation is an emerging method of volume assessment that, to date, seems even better than ultrasound measurements of the IVC.
• To calculate PPV, print out a tracing from an arterial line that captures both inspiration and expiration use the following formula:
  • ΔPP = 100 × (PPmax - PPmin)/[(PPmax + PPmin)/2]
• Values > 13% indicate that the patient is likely on the ascending portion of their Starling Curve and will augment their cardiac output with additional IVFs.
• Note that arrhythmias and spontaneous breathing can affect measurements, thus patients should be mechanically ventilated and well sedated when measuring PPV.

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Unusual Presentations of AAA

Many unusual presentations of AAA have been reported in the literature and include:

• Musculoskeletal complaints (thigh or groin pain)
• Bilateral testicular pain
• Unexplained inguinal pain-VERY well described
• Femoral neuropathy
• Abdominal pain and urge to deficate (and, NO, I am not making that one up)

One more note on the whole urge to deficate thing: any thing that leads to hemoperitoneum may cause this strange complaint (ruptured AAA, ruptured ectopic pregnancy).

Be wary of the limitations of correlating a temperature with infection in the elderly:
1. The elderly are 3-4x more likely to develop hypothermia in response to serious infections. Never rule out a serious infection simply based on a low or normal body temperature.
2. The elderly take longer to mount a fever than younger patients.
3. The elderly have a slightly lower body temperature at baseline, possibly 1 degree lower. As a result, "fever" in the elderly is sometimes defined as 99.5 degrees rather than the traditional 100 or 100.4 used in younger patients.

Hypertensive encephalopathy is generally seen in children with renal disease, e.g. acute glomerulonephritis or ESRD. 

Signs and symptoms include bp >99th percentile for age and height and neurologic impairment.  May present acutely with seizure or coma, or subacute with HA, vomiting, lethargy, blurry vision or change in mental status.  Exam findings may also include papilledema.

MRI may show increased signal in occipital lobes of T2 weighted images, known as reversible posterior leukoencephalopathy.

Treatment is to lower BP by 20-25% for the first 8 hours and to normative levels over 24-48 hrs.  IV therapy with esmolol drip, labetalol or nicardapine are the treatments of choice.  Nitroprusside prudent in most hypertensive adult emergencies must be used cautiously  if history of renal disease secondary to cyanide toxicity. Seizure should also be treated as you would with status epilepticus.

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Rhogam Dosing:

Though most textbooks recommend Micro-Rhogram (50mcg) for woman that have miscarried and are less than 12 weeks gestation, you might find it a real challenge to get that dose from your pharmacy or blood bank.

The cost difference between microRhogram and Rhogam is minimal so most hospitals have decided to only stock full dose (300 mcg) Rhogam.  The full dose can be given to woman in their 1st trimester without any deleterious effects. 

Just remember if you are giving it as a result of a delivery you should order a Kleihauer-Betke test to determine if additional doses of Rhogam are needed.

Priapism - prolonged involuntary erection - is an adverse effect with some drugs. Here is a list of the more commonly reported:

• Androgens
• Anticoagulants
• Antihypertensives: Hydralazaine, labetolol, phentolamine, prazosin
• Antipsychotics
• Cantharidin
• Cocaine
• Diazepam
• Marijuana
• Sildenafil
• Trazadone
• Yohimbine

• To be conscious, one must be both awake and alert.

• Patients who sustain severe anoxic cortical damage, with brainstem sparing, exhibit wakefulness and sleep, but are not aware, and thus, are unconscious.

• This description is the hallmark of a "vegetative state."

• A coma is a deep depression in the state of altered level of consciousness, which is characterized by the patient's response to verbal or painful stimuli.