UMEM Educational Pearls

• Although rare, it is a serious life threatening entity of pediatric emergency medicine
• Must be in the differential of those with signs of increased intracranial pressure or focal deficit and hx of sinusitis, mastoiditis or cyanotic congenital heart disease.
• Investigation and diagnosis primarily with CT scan
• CSF studies demonstrate sterile fluid with elevated protein, and mildly elevated WBC
• Antibiotic coverage should be broad Naficillin/Vanc + Ceftriaxone + Metronidazole, until speciation and susceptibilities obtained from surgical specimen
• Steroids reserved only in cases of imminent herniation
• Controversy exists over prophylactic anticonvulsants
• Mortality recently <10% attributed to early diagnosis and appropriate antibiotic coverage.

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You've probably long been taught that Sickle Cell Trait is an irrelevant piece of the PMH, unless you are a genetic counselor.  Well, thanks to Dr. Rolnick and a literature search, I (and now you) know that that is incorrect.

Though Sickle Cell Trait (SCT) does not cause exactly the same pathologies as Sickle Cell Disease (SCD), there are believed to be a variety of RBC abnormalities associated with HgbS (such as measurably lower RBC deformability, and low levels of sickling under extreme heat and exercise conditions) which contribute to increased exercise-related sudden death.  In one NEJM study of all deaths among 2 million (MILLION) military recruits over a 4 year period, the relative risk of otherwise unexplained sudden death for black recruits with HgbAS vs. black recruits without HgbS was 27.6 (p<0.001), and 39.8 (p<0.001) for all recruits (HgbAS vs. no HgbS).

I must say that this topic is not controversy-free, however, I should also note that my search for "Sickle Cell Trait and Sudden Death" turned up quite a few articles directed at plaintiff's attorneys. 

The take-home point is that SCT is likely not a benign condition, and you must be cautious in telling patients that it is.  Again, this phenomenon is best described in patients undergoing extreme physical exertion, but hopefully this will change how you think about SCT.

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• The classic triad of fever, meningismus (stiff neck), and altered mental status only occurs in 44% of cases of acute bacterial meningitis (ABM).

• Headache is a much more common presenting complaint with ABM.

• The sensitivity and specificity of Kernig and Brudzinski signs are suboptimal, making their presence or absence of little diagnostic value.

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Daptomycin and MRSA

• Several new antibiotics are approved for the treatment of infections due to MRSA: linezolid, daptomycin, and tigecycline.
• Although most are familiar with linezolid, it seems that both daptomycin and tigecycline are being used more frequently.
• A few pearls on daptomycin:
  • administered IV once daily
  • dose needs to be adjusted in patients with renal failure
  • exerts its effect through a calcium-dependent binding to the bacterial membrane resulting in cell death
• Importantly, daptomycin is inactivated by pulmonary surfactant and therefore should not be given in patients with suspected MRSA pneumonia.

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Elderly patients are at higher risk of barotrauma with positive pressure ventilation (e.g. CPAP, BiPAP, and especially after intubation) because of decreased vital capacity and lung compliance. Watch those plateau pressures closely!

If an elderly patient develops hypotension within minutes of endotracheal intubation, always consider tension PTX (and don't forget about hypovolemia, as we've discussed before).

     Most hand sanitizers contain ethanol, while some contain isopropyl alcohol. The concentration of alcohol in these products varies from 45% to 95%, with the most commonly used products containing 62%.  How much would a 15 kg child have to ingest to obtain a blood alcohol concentration of 100 mg/dL (or 0.1%)?

     Assuming a volume of distribution of 0.6 L/kg and 100% bioavailability, only 15-20 mL is required to produce this toxic level.  That is equivalent to 3-4 teaspoons or approximately 8-10 “squirts” of hand sanitizer!

The following symptoms of phenytoin toxicity typically present initially, once plasma concentrations reach the listed levels below:

• Nystagmus (on lateral gaze, at 20 mcg/mL)
• Ataxia (at 30 mcg/mL)
• Dysarthria and lethargy (at over 40 mcg/mL)

Other associated symptoms include tremor, hyper-reflexia, nausea, and vomiting.

Complications of Resuscitation

• CPR, defibrillation, endotracheal intubation, and cannulation of peripheral and central veins are common procedures during resuscitation of cardiac arrest patients
• Although not obvious immediately, complications from these procedures can develop and manifest several hours after successful return of spontaneous circulation
• Not surprisingly, the most common complications are rib and sternal fractures
• Additional complications to recall include:
  • tracheal mucosal lesions (almost 20%)
  • retropharyngeal bleeding
  • liver/spleen injuries
  • rhabdomyolysis (post-defibrillation)
  • air embolism (central venous access)
  • gastric rupture (very rare; due to continuous air insufflation into the stomach)

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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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