UMEM Educational Pearls

In the setting of acute cyanide poisoning, it is virtually impossible to obtain a timely cyanide level to help assess toxicity.  However, there are two diagnostic tests that can help confirm your diagnosis.

1. Anion gap metabolic acidosis with elevated lactate
2. Narrowing of the venous-arterial PO₂ gradient

Remember cyanide halts cellular respiration meaning the cells cannot utilize oxygen.  Therefore, the venous PO₂ should be about the same as the arterial PO₂.  The cells then switch to anaerobic metabolism, thereby producing lactate.

How to Perform a Median Nerve Block

• The most common emergency department indication for performing median nerve blocks is to anesthetize its hand distribution (i.e. volar surface of hand) for pain control and/or to perform procedures such as laceration repair and dislocation reductions.
• The median nerve is located at the proximal flexor crease of the wrist, between the palmaris longus (PL) and flexor carpi radialis (FCR) tendons.  The FCR lies radial to the PL tendon.
• Use a 25 or 27 gauge needle, inserted to a depth of 1 cm, to inject 3-5 mL of plain lidocaine proximal to the distal wrist flexor crease, just ulnar to the PL tendon.
• If the PL tendon is absent, as is the case in 25% of people, direct the needle in line with the ring finger.
• If distal paresthesias result, withdraw and reposition the needle as this suggests that the median nerve was directly struck, which should be avoided.

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Pulmonary Contusion and Ventilator Management

• Pulmonary contusion is the most common injury in blunt thoracic trauma.
• Patients with pulmonary contusion often present with hypoxia, hypercarbia and increased work of breathing.
• Importantly, patients with pulmonary contusion have a low cardiopulmonary reserve.  Maintain a low threshold for initiating mechanical ventilation is these patients.
• When starting mechanical ventilation, think about the following:
  • Patients are at high risk for developing ARDS
  • Most centers use a low tidal volume ventilatory strategy
  • Higher levels of PEEP may be necessary to recruit collapsed alveoli
  • High frequency oscillatory ventilation (HFOV) and airway pressure release ventilation (APRV) are modes of ventilation that are gaining in popularity for ventilating patients with pulmonary contusions.

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Acute use of cocaine increases risk of acute MI due to tachydysrhythmias, vasospasm, and increased platelet aggregation. There is a 24-fold increased risk of MI in the first hour after use of cocaine. 6% of patients presenting with cocaine-chest pain rule in for acute MI.

[Weber, Acad Emerg Med 2000]

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Radiologic evaluation of the elbow (Part 2)

Helpful clues in the evaluation of elbow trauma:

• The Anterior humeral line and the Radiocapitellar line
  • The anterior humeral line: On a true lateral film, this line is drawn along the anterior aspect of the humeral shaft on the lateral radiograph This line passes through the middle one third of the capitellum in bones that are not injured. It is very useful for detecting subtle fractures.
    • http://www.radiologyassistant.nl/images/thmb_4214e859138b1anthumlinebest.jpg
  • Fractures (i.e. supracondylar) usually result in displacement of the capitellum posteriorly.
  • Thus, the anterior humeral line passes through the anterior one third or entirely anterior to the capitellum.
    • http://www.imageinterpretation.co.uk/images/elbow/RAISED FAT PADS, SUPRACONDYLAR graphic.jpg
• The Radiocapitellar line: Since the radius articulates with the capitellum, a line is drawn through the middle of the radius shaft and extended proximally through the joint should bisect the capitellum on all views (AP & lateral).
  • http://img.medscape.com/pi/emed/ckb/radiology/336139-415822-5412.jpg
  • http://nypemergency.org/images/v2c18n.jpg
  • Improper alignment indicates a radial head dislocation (which may be very subtle)
    • http://nypemergency.org/images/mont.jpg
    • http://www.radiologyassistant.nl/images/49304bf192d7e12.jpg

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A recent study examined the effects of accidental digital epinephrine injection from auto-injectors. 127 cases with complete follow-up had the following effects:

• no effects were reported in 10%
• minor effects in 77%
• moderate effects in 13%
• major effects in 1 case

Pharmacologic vasodilators were used in 23%. Four patients had possible digital ischemia. All patients had complete resolution of symptoms, most within 2 hours. No patient was admitted, received hand surgery consultation, or had surgical care. 

Although this speaks for the safety of digital anesthesia using epinephrine, it underscores the importance of providing education to patients who are prescribed epinephrine auto-injectors.

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• Ulnar nerve blocks are relatively easy to perform and excellent for anesthetizing the ulnar nerve distribution, particularly of the hand.

• Ulnar nerve blocks can be performed at the level of the wrist (dorsal or volar side) or at the elbow.  Volar side blocks at the wrist tend to be easier to perform and associated with less risk. 

• Using a 27 gauge needle, infiltrate 2 to 3 mL's of lidocaine between the flexor carpi ulnaris tendon and the distal-most aspect of the ulnar bone.  The needle should be inserted 1 to 2 cm's at about a 40 degree angle, at the proximal-most wrist crease.

• Do not puncture the actual ulnar nerve or the ulnar artery.  Should needle insertion cause distal hand paresthesias or blood withdrawal, do not inject and immediately remove the needle, as this suggests that the ulnar nerve or artery was struck, respectively.  The objective is to allow the lidocaine to infiltrate into the nerve, not to inject it directly into the nerve.

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Hyponatremia plagues many neurosurgical patients due to the syndrome of inappropriate secretion of ADH (SIADH) or the cerebral salt wasting syndrome (CSW). Both diseases may appear similar (hyponatremia, increased urine osmolarity, increased urine sodium, normal adrenal, renal and thyroid function), but there is one BIG difference. Patients with SIADH are euvolemic or hypervolemic (excess ADH causes fluid retention) whereas patients with CSW are fluid depleted (impaired renal handling of sodium and water). To differentiate, look for signs of hypovolemia: orthostatics, dry mucus membranes, hemoconcentration, pre-renal azotemia, and/or hemodynamics (IVC collapse anyone?).

Bottom line: Distinguish SIADH from CSW because the treatments are exact opposites:

SIADH: Fluid restrict

CSW: Give water and salt (i.e., 0.9% saline)

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Hypertensive Encephalopathy (HE) is a clinical diagnosis and can look like many other disease entities.

HE refers to a relatively rapidly evolving syndrome of severe hypertension in association with severe headache, nausea, and vomiting, visual disturbances, convulsions, altered mental status and, in advanced cases, stupor and coma.

The key is the presence of severe hypertension. Remember, though, that 160/105 mm Hg may be high for an individual patient. Most patients with the syndrome will have diastolic pressures well in excess of 120-130 mm Hg. The only way you will know if the diagnosis is correct is to treat the BP (carefully control), work up other etiologies, and see of symptoms improve with BP control.

Beware the patient with severe HTN and seizure. Seizure may be the first, and only, symptom of hypertensive encephalopathy. 

Some confusion exists regarding proper distinction and treatment between the different tachydysrhythmias associated with WPW. Here's the scoop:
1. orthodromic SVT: narrow regular tachycardia, looks just like a routine SVT, treat just like any other SVT (AV nodal blockers work fine)
2. antidromic SVT: wide regular tachycardia, looks just like VTach, treat like VTach (amiodarone, procainamide, shock; lidocaine won't work, though won't harm either)
3. atrial fibrillation: very different!! irregularly irregular, morphologies of the QRS complexes vary between narrow and wide, some areas may have rates as high as 250-300/min, MUST avoid all AV nodal blockers (which includes adenosine, CCBs, BBs, digoxin, amiodarone); treat with procainamide or sedation+cardioversion

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Adhesive Capsulitis -- Frozen Shoulder

1. Characterized by pain and loss of motion or stiffness in the shoulder.Normally not seen below the age of 40, affects ~2% of the population and diabetics are at increased risk.
2. Due to thickening and contracture of the capsule surrounding the shoulder joint.
3. Can occur after trauma to the shoulder if the shoulder is not moved early enough, but is also know to occur idiopathically.
4. X-rays are only helpful to rule out other causes of the shoulder pain and are typically normal in Adhesive capsulitis.
5. Typically will get better on its own over 2-3 years.
   1. Physical Therapy and home exercises aimed at restoring ROM can shorten the duration of pain and stiffness.
   2. Surgery can be done if there is no improvement with medical management and physical therapy.
6. Prevention strategies include early ROM exercises in those with shoulder injuries especially in the elderly diabetic.

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• most common cause of low platelets in children
• immune-mediated destruction of circulating platelets
• acute ITP peak incidence between 2-5 years of age; chronic ITP peaks in adolescence
• recent history (1-6 weeks) of viral infection or immunization is common
• no hepatosplenomegaly
• low platelets with megathrombocytes on smear, with normal hemoglobin (which differentiates from TTP, HUS, and DIC)
• nearly 90% of children will have normal platelet counts in 6 months
• treatment reserved for platelet counts <20,000 or significant bleeding:  IVIG (best response rate of 95%), corticosteroids (79% resposne rate), anti-rH (D) immunoglobulin (82% reesponse reate)

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In a previous pearl we were discussing the need to perform EGD for any suicidal patient with a history of ingestion of a caustic to grade injury and assess chance of perforation and/or stricture formation. Suicidal patients are intentionally ingesting the caustic and can thus justify the risk/benefit ratio more easily than the pediatric unintentional ingestion. The concerned parent will bring the child in with a possible ingestion of a caustic. The container could be simply in the same room, spilled on the child and never be ingested. Even if ingested, the amount is less if the child tastes the caustic and will reflexively cause spitting. The literature is scant in regards to this type of patient but seems to point to this general algorithm:

Child displays 2 or more of the following symptoms there is enough evidence from case series that there will be a clinically signficant lesion found on EGD.

Vomiting, Drooling, Stridor, Presence of Oropharyngeal Burns

That being said, many clinicians would elect for EGD and assessment of airway with stridor alone. Do not be fooled into thinking if you see no oral lesions that there is no way the child ingested the caustic. Each case series showed a lack of correlation of physical exam findings to EGD findings.

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• When examining the hand, care should be taken to thoroughly assess both the sensory and motor function on both the dorsal and palmar surfaces.

• The dermatomes of the hand provide sensation and are comprised of the ulnar, median, and radial nerves (see diagram below).

• (1) Light touch, (2) sharp touch (i.e. pinprick), (3) temperature, (4) propioception (joint position sense), (5) vibration, and (6) 2-point discrimination in the following nerve distributions should be assessed:

              --  ulnar nerve >>> supplies palmar surface and dorsal tips of little finger and medial half of ring finger, including

                   adjacent parts of hand.

              --  median nerve >>> supplies palmar and dorsal aspects of thumb, index finger, middle finger, and lateral half

                   of ring finger, including adjacent parts of hand.

              --  radial nerve >>> supplies most of dorsal surface of hand.

Hemostatic Therapy for ICH - Updated Guidelines

• The AHA/ASA just published updated guidelines for the diagnosis and treatment of acute spontaneous intracerebral hemorrhage (ICH).
• Regarding hemostatic therapy, new/revised recommendations from the 2007 AHA/ASA guidelines include:
  • Patients with severe thrombocytopenia or factor deficiency should receive platelets or factor replacement
  • Patients with ICH due to oral anticoagulants (warfarin) should receive intravenous vitamin-K and vitamin-K dependent factor replacement
    • Prothrombin complex concentrates (PCCs) are being increasingly used and are considered a reasonable alternative to FFP.  To date, studies have not shown improved outcome with PCCs.
    • Recombinant factor VIIa (rFVIIa) is not recommended as a sole agent for warfarin-related ICH
  • rFVIIa is not recommended in unselected patients
  • Usefulness of platelet transfusions for patients using antiplatelet medications is unclear and currently investigational.

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Beta Blockade in Treating Acute Aortic Dissection

Medical therapy for acute aortic dissection is aimed at decreasing shear stress within the aorta. Although there are many agents to choose from when treating hypertension in patients with acute aortic disease, all regimens should include a beta blocker (like esmolol) unless contraindicated. Initiation of a beta blocker before another antihypertensive agent is added is crucial as this will prevent reflex tachycardia associated with vasodilators and other afterload reducers. Reflex tachycardia may worsen the dissection. 

typical ECG findings associated with hypercalcemia: short QT (e.g. QTc < 400 msec), ST-segment depression

typical ECG findings associated with hypocalcemia: prolonged QT

note that hyperkalemia is often associated with hypocalcemia, and as a result hyperkalemic patients often have a prolonged QT, but it's not the hyperkalemia that prolongs the QT, it's the hypocalcemia

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Rotator Cuff Tears:

Four muscles make up the rotator cuff (SITS) which control internal and external rotation of the shoulder and abduct the shoulder.

1. Supraspinatus
2. Infraspinatus
3. Teres Minor
4. Subscapularis

Tears can be due to acute injuries (falls, heavy lifting, forceful abduction), though the majority (>90%) of rotator cuff tears are chronic in nature and due to subacromial impingement and decreased blood supply to the tendons.

Most patients can be treated with sling immobilization, NSAIDs and referral to sports medicine or orthopaedic surgeons.  Elderly patients should be referred quickly as prolonged immobilization can lead to a frozen shoulder.

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We will all get the patient presenting with low blood glucose on a regular basis. In general, barring any underlying infection, those who are insulin dependent can be corrected with IV dextrose and/or food and be discharged. Those on a sulfonylurea may experience repeated hypoglycemic episodes and require admission - perhaps even treatment with the antidote: octreotide.

Below is the duration of action and half-life of the sulfonylureas which illustrates the need for admission:

• Chlorpropamide (Diabinase): Duration: 24-27hrs; t 1/2: 36hrs
• Glipizide (Glucatrol): Duration 16-24hrs; t 1/2: 7hrs
• Glipizide XL (Glucatrol XL): Duration 24hrs
• Glyburide (Micronase others): Duration <24hrs; t 1/2 10hrs
• Glimepride (Amaryl): Duration 16-24hrs; t1/2: 5-9hrs

Duration of action is the physiologic effect whereas the half-life is the pharmacokinetics of elimination of the drug. Often these two numbers are different for drugs. Do not let the half-life fool you into thinking it is safe to discharge a hypoglycemic patient on a sulfonylurea.

• Cervicogenic headaches are a syndrome of chronic, hemicranial pain that is referred to the head from bony structures or soft tissue of the neck.
• Adequate treatment of these headaches is often difficult to achieve, particularly from the emergency department, as a multi-faceted approach including pharmacologic, physical, anesthetic nerve block, psychological and sometimes surgical therapy, is often required.
• The emergency physician may prescribe simple agents such as acetaminophen and ibuprofen, with or without muscle relaxants to treat cervicogenic headaches.
• When close follow up is ensured, low doses of tricyclic anti-depressants or anti-epileptics such as gabapentin, divalproex sodium, carbamazepine, and topiramate may be utilized; while these are not FDA approved for the treatment of cervicogenic headaches, they have been shown to be effective for some headache types and neurogenic pain syndromes.

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