UMEM Educational Pearls

Knee dislocations are uncommon, and prosthetic knee dislocations even rarer.  Some general facts about prosthetic knee dislocations are:

• Posterior dislocations typically occur in the post-operative period and are usually the result of trauma that disrupts the PCL ligament.
• Factors that predispose a person to posterior dislocations are valgus deformity of the knee, malposition or improper selection of prosthetic components, patellar instability, and extensor mechanism dysfunction.
• The mechanism for this dislocation is typically flexion and external rotation of the knee when the lateral side of the knee is too loose.
• Anterior dislocations more commonly occur months to years after surgery and usually are not associated with trauma.
• Many of these dislocations result from loss of integrity of the posterior cruciate ligament, which provides anteroposterior stability of the knee and assists in femoral rollback. This motion is essential for the extensor mechanism of the knee to function.
   

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So the magnesium didn't work, and the baby is on the way!  You're prepared with everything you need for the delivery from bulb suction to a tripod for Dad's camera...  But what is going to special about this baby?  

Babies born to mothers who received magnesium therapy for any reason are at risk for hypotonia and severe respiratory depression.

• DO provide respiratory support as needed, as respiratory depression is the only dangerous side effect of hypermagnesemia in the neonate (be prepared to provide supplemental oxygen, positive pressure ventilation (PPV), and possibly intubation)
• DO recognize that generalized hypotonia may be a clue as to how significantly affected the neonate may be, however, don't let the hypotonia itself scare you - it will go away, and is not dangerous in and of itself
• DO follow neonatal resus guidelines (PPV for HR<100, CPR for HR<60), but remember that supportive measures will resolve all problems related to hypermagnesemia in the neonate...if there are other issues, don't blame the mag
• DO NOT give calcium as, in contrast to their mothers, these patients are not hypocalcemic (and the hypermagnesemia will spontaneously resolve in 48 hours)
• DO remember that these infants frequently require a brief NICU stay until they no longer require respiratory support

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·      In the event a nuclear power plant accident, people may be exposed to a mixture of radioactive products. The main radionuclides representing health risk are radioactive caesium and radioactive iodine.

·      Iodine-131 is concentrated in the thyroid gland and may eventually lead to development of thyroid nodules and thyroid cancer.

·      Radioiodine uptake by the thyroid can be blocked by taking potassium iodide (KI) pills or solution, preventing these effects.

·      KI should not be taken in the absence of a clear risk of exposure to a potentially dangerous level of radioactive iodine because KI can cause allergic reactions, skin rashes, salivary gland inflammation, hyperthyroidism or hypothyroidism.

·      Since radioactive iodine decays rapidly, current estimates indicate there will not be a hazardous level of reaching the United States from this accident.

·      There are three FDA approved KI products: Iosat, Thyrosafe and ThyroShield.

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• Trigeminal Neuralgia (TN) presents with unilateral, lancinating head and facial pain, affecting one or more of Cranial Nerve V's divisions.

• The pain occurs in 1 to 5 second multiple attacks throughout the day.  Symptoms may remit and recur.

• TN is associated with trigger points, but lacks any associated focal neurologic deficit or abnormality.

• These characteristics will help distinguish TN from other sources of unilateral headache, such as migraines, cluster headaches, sinusitis, and glaucoma.

• There are a host of treatments for TN, including options such as medical management with anti-convulsants and/or muscle relaxants, surgical ablation, alcohol injection (induces numbness), glycerol injection (destroys affected part of nerve), balloon compression, and administration of electrical current.

• Medical management with analgesics and muscle relaxants is typically the most appropriate, first-line treatment in the emergency department.

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Hemorrhagic bullae in an ill-appearing patient with underlying cirrhosis should prompt consideration for an invasive infection due to Vibrio vulnificus.

V. Vulnificus is a gram negative rod and causes a highly lethal infection in patients with cirrhosis.

Antibiotics for these patients should include coverage for this organism. This should include doxycycline and a third genaration cephalosporin.

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Severe hemolysis/hemolytic anemia in a patient with a prosthetic cardiac valve suggests a paravalvular leak. In this condition, a portion of the valve becomes dislodged from the valve annulus. It can occur immediately after surgery or delayed if from endocarditis. Paravalvular leaks are more common with mechanic valves. Patients may also present with sudden pulmonary edema.

The treatment will focus on management of the pulmonary edema and prompt surgical repair.

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For patients with normal renal function, enoxaparin dosing for treatment of VTE is 1 mg/kg subcut every 12 hours OR 1.5 mg/kg subcut every 24 hours.

Studies have evaluated dosing for patients weighing up to 190 kg and found the 1 mg/kg q 12 hours dose to be safe and effective.  It can even be used for patients heavier than 190 kg, but anti-Xa monitoring is recommended.

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Extravasation from radiocontrast, phenytoin and promethazine have resulted in significant tissue necrosis sometimes requiring surgical debridement and reconstructive plastic surgery. 

Pearl: Keep the infiltrated peripheral IV in and inject hyaluronidase 3-5mL (150U/mL) into the same subcutaneous pocket of medication. Hyaluronidase will increase the systemic absorption of the drug, decreasing its time in the SQ tissue. Extremely safe drug (we have the enzyme in our body) and has been used in neonates as well as adults. Also used for SQ hydration in palliative care and pediatrics.

Controversy: Hot vs Cold - Heat will cause vasodilation and hopefully increase systemic absorption but will likely also increase SQ spread possibly increasing the surface area of injury. Cold will cause vasoconstriction and decrease size of injury however will concentrate drug and possibly worsen the local injury.

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  1: Sokol DK, Dahlmann A, Dunn DW. Hyaluronidase treatment for intravenous  phenytoin extravasation. J Child Neurol. 1998 May;13(5):246-7.     2: Cochran ST, Bomyea K, Kahn M. Treatment of iodinated contrast material  extravasation with hyaluronidase. Acad Radiol. 2002 Aug;9 Suppl 2:S544-6.     3: Few BJ. Hyaluronidase for treating intravenous extravasations. MCN Am J Matern Child Nurs. 1987 Jan-Feb;12(1):23.     4: Kuensting LL. Treatment of intravenous infiltration in a neonate. J Pediatr  Health Care. 2010 May-Jun;24(3):184-8. Epub 2010 Mar 20.     5: Raszka WV Jr, Kueser TK, Smith FR, Bass JW. The use of hyaluronidase in the  treatment of intravenous extravasation injuries. J Perinatol. 1990  Jun;10(2):146-9. 

• Myasthenic patients who initially present in a stable fashion with normal ventilation and minimal dyspnea can decompensate rapidly.
• In Myasthenia Gravis, the body produces antibodies against native post-synaptic acetylcholine (Ach) receptors. Adding a paralytic that occupies the few remaining functional Ach receptors could significantly prolong general muscular dysfunction and the need for ventilatory support during a myasthenic crisis.
• If intubation is required, DO NOT administer neuromuscular blocking/paralytic agents such as succinylcholine or rocuronium, as these agents antagonize Ach binding receptors at the post-synaptic membrane of the neuromuscular junction.
• Studies have shown that the use of propofol and fentanyl, without any paralytic, provides sufficient analgesia and sedation to successfully complete a humane intubation in these cases.
  
   

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Emergency Medicine physicians are gaining experience with non-invasive ventilation (i.e., Bi-level ventilation and continuous positive-pressure ventilation) in managing respiratory distress and failure. Although NIV is commonly used across a variety of pathologies, the best data exists for use with COPD exacerbation and cardiogenic pulmonary edema (CHF, not an acute MI) 

Although other indications for NIV have been studied, the data is less robust (eg., smaller study size, weak control groups, etc.). If there are no contraindications, however, many experts still support a trial of NIV in the following populations:

• Asthma
• Severe community acquired pneumonia
• Acute lung injury / Acute Respiratory Distress Syndrome
• Chest trauma (lung contusion, rib fractures, flail chest,etc)
• Immunosuppression with acute respiratory failure
• Neuromuscular respiratory failure (eg., Myesthenia Gravis)
• Cystic Fibrosis
• Pneumocystis Jiroveci Pneumonia
• “Do not intubate” status

Failure to clinically improve during a NIV trial should prompt invasive mechanical ventilation.

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Question

25 year old male presents after falling from 10 feet and landing on right shoulder. Diagnosis?

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Aortocaval compression occurs often when gestational age is > 20 weeks. This compression significantly compromises the chances of maternal survival in cardiac arrest. Because it is often difficult to know the exact gestational age, it is commonly recommended that emergency C-section in maternal cardiac arrest be performed when the fundus extends above the level of the umbilicus.

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GOUT part 1

Gout is an inflammatory arthritis that classically affects the first metatarsal phalangeal joint

Gout prefers cool ambient temperature hence gouty tophi prefer the great toe (one of the coldest parts of the body) and avoids "warmer" joints such as the hip and shoulder.

Remember that gout can affect other joints as well (elbow, wrist, knee and ankle) and  can cause painful bursitis and tendonitis

Multiple joints can be involved simultaneously (leading to confusing with RA and OA)

The involved joint will often be red, hot, swollen and very painful leading to easy confusion with cellulitis and or a septic arthritis

Diagnose gout by demonstrating monosodium urate crystals in the synovial fluid.

**Remember previous pearl by Dr. Bond regarding the coexistence of gout with septic joint**

Serum uric acid levels are commonly elevated but can be normal or even low

Use caution with this test because asymptomatic hyperuricemia is much more common than gout

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• seborrheic dermatitis is most common in infants within the first two months of birth
• appears as  erythematous, greasy yellow scales most commonly on the scalp (cradle cap), and may also occur on the face
• most cases resolve spontaneously within weeks to months, but severe cases may be treated with 1% hydrocortisone cream, sahmpooing with selenium sulfide, and using an emollient to remove scales
• in extreme cases, consider hte possibility of Langerhans cell histicytosis, especially if atrophy, ulceration, or purpura are also present
• rarely occurs in children between 1 and 12 as they do not have active sebaceous glands, but will appear as dandruff in adolesecents
   

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Note that yesterday's Neurology pearl should have read as follows -

Amongst others, diagnostic criteria for NMS includes:

Exposure to a dopamine ANTAGONIST (NOT AGONIST) or dopamine agonist withdrawal within past 72 hours.

Apologies for the type-o.

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Could this be another risk factor for DVT/PE. Maybe not yet but it is worth mention. A recent observatioal study in BMJ showed that there was  an associated increase with DVT or PE. From a database of 25,532 patients over a 3 year period of time and finding match controls, the results were:

1. 32% overall increase risk of DVT/PE in patient who were taking antipsychotics
2. Recent initiation of therapy within 3 months increased risk 2-fold
3. Risk was greater with atypical antipsychotics (Odds Ratio 1.73 Atypical vs 1.23 Old)
4. Risk was greater with lower dose than higher dose

Limitations were this is was an observational study with missing data. BMI was missing in these records and it is always difficult to tease out the multiple medications these patients are on.  Also don't have a great biological mechanism (yet). Still makes you go hmm....

Antipsychotic drugs and risk of venous thromboembolism, Parker, BMJ, 2010.

• Neuroleptic Malignant Syndrome (NMS) is a life-threatening complication of anti-psychotic medication therapy.
   
• While NMS is rare (0.02 to 2.44% amongst those taking neuroleptic drugs), its associated mortality (up to 12%) and morbidity (i.e. rhabdomyolysis, pneumonia, seizures, renal failure, disseminated intravascular coagulation (DIC), respiratory failure) are severe.
   
• Historically, there has been little consensus about universally accepted diagnostic criteria for NMS, until an expert panel of various physician specialists recently convened and determined the following criteria:

           - Exposure to dopamine agonist or dopamine agonist withdrawal within past 72 hours
           - Hyperthermia
           - Rigidity
           - Mental status alteration
           - Elevated creatinine phosphokinase
           - Sympathetic nervous system lability (2 or more of the following: elevated blood pressure, fluctant blood pressure, urinary incontinence, diaphoresis)
           - Tachycardia and tachypnea
           - Negative work-up for infectious, metabolic, neurologic, or toxic etiologies.

• Treatment includes immediate withdrawal of any antipsychotic medication and is, otherwise, largely supportive.

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Aspiration Pneumonitis and Pneumonia

• Aspiration of low pH gastric fluid or food matter is common in critically ill patients and often underdiagnosed.
• Patients with aspiration initially develop a pneumonitis that, in some, can be complicated by bacterial pneumonia.  Up to 33% develop severe ALI/ARDS, with an associated 30% mortality rate.
• Aspiration pneumonitis presents with hypoxia and a CXR demonstrating infiltrates in the dependent portion of the lungs.  Often, the degree of respiratory distress is worse than the CXR appearance.
• Since it is challenging to differentiate aspiration pneumonia from aspiration pneumonitis, current recommendations suggest initiating empiric antibiotics with agents that have adequate Gram-negative coverage.  Routine coverage against anaerobic bacteria is not currently recommended, except in patients with severe periodontal disease and those with a lung abscess on CXR or CT.
• Despite the initial inflammatory response, steroids are not indicated for patients with aspiration.

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Rib fractures are associated with significant morbidity and mortality in the elderly, and the risk increases dramatically with each successive rib fractured. An elderly patient with 3 rib fractures has a mortality of 20% and risk of pneumonia is 31%. As a general rule, you should really think twice about discharging home any elderly patients with rib fractures.

[credit to Dr. Joe Martinez for bringing forth this information]

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Talar Neck Fractures

Have a high rate of avascular necrosis (AVN), nonunion, and arthritis.  Almost all require ORIF

• Hawkins 1:
  • 0- 13% AVN rate
  • non-displaced fracture
• Hawkins 2:
  • 20- 50% AVN rate
  • Displaced fracture with subluxation or dislocation of the posterior facet of the subtler joint. Subtalar joint usually dislocated posteriory
• Hawkins 3:
  • 20-100% AVN rate
  • Displaced fracture of the talar neck with dislocation of the body of the talus from both the subtalar joint and the ankle joint

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