UMEM Educational Pearls

• Anisocoria is when pupillary size is assymetric.

• Anisocoria suggests a lesion in the efferent fibers supplying the pupillary sphinter muscles.

• In order to localize the causative lesion, you must first determine which pupil is abnormal, the smaller one or the larger one.

• The smaller pupil is abnormal when the degree of assymetry is more pronounced in darkened settings.

• The larger pupil is abnormal when the degree of assymetry is more pronounced in bright light.

 Quick Pearls for Intubating:

1. When intubating, make sure to use two hands!

• Have the person holding cricoid pressure let up...cricoid pressure many times makes your job more difficult
• You as the intubator then swing your right hand around and manipulate the larynx (left, right, up, down, etc)
• When you get the view you want, have someone take over pressure and then pass the tube
• Using two hands makes your job so much easier

2. Resist the urge to look for cords

• Your job is to get the tube in the airway
• If you can identify the two arytenoid cartilages, you are home free. Aim north of these structures.
• You don't have to see cords to intubate. All you need are the landmarks that identify the entry into the glottis....just pass the tube north!
• I had a case just a few days ago where the only thing we saw were the two arytenoids (covered in blood). No cords were seen, but we passed the tube above (i.e. north) the arytenoids and we were in.

3. Stylet shape is crucial

• Shape your tube with the "straight to cuff" technique
• The tube is straight and then bent 15-20 degrees at the beginning of the cuff
• This shape will prevent the tube from actually obscuring your view and will increase your success.

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 Phentolamine for vasopressor extravasation

I was recently informed of a case from an another institution in which a patient was started on a vasopressor medication via a peripheral IV while attempts at central access where attempted.  The patient unfortunately suffered permanent extremity ischemia due to significant extravasation of the vasopressor medication into the soft tissue.

• Phentolamine is reportedly the antidote for vasopressor extravasation into the skin and soft tissues (the evidence is not robust and limited primarily to case reports and animal data)
• Phentolamine is a non-specific alpha-blocking agent that inhibits vasoconstriction and theoretically improves blood flow through the affected area
• Take 5-15 mg of phentolamine and mix in 10 mL of normal saline - inject this into the affected area as soon as possible
• Give the patient concurrent IVFs in the event of some systemic absorption

The longitudinal subcostal view on bedside ultrasound can be very helpful at addressing a patient's fluid status. 
Take a look at the diameter of the IVC 2 cm proximal to the hepatic vein on this view and ask the patient to quickly sniff. If the patient has normal fluid status, the diameter of the IVC will collapse approximately 50%.

If you notice that the IVC completely collapses during the sniff, the finding is highly accurate at predicting hypovolemia and a low CVP.

If, on the other hand, the IVC doesn't appear to collapse much at all, the finding is highly accurate at predicting a high CVP and elevated right atrial pressure. This may occur in the presence of fluid overload from decompensated CHF, cardiac tamponade, and conditions associated with RV failure (e.g. massive pulmonary embolism).

Splinting Pearls:

1. When using plaster of paris remember to use at least 10 layers for upper extremities and 15-20 layers for lower extremities.
2. Always apply the splint so that the joint above and below the fracture is immobilized.
3. On radius and ulnar fractures, a sugar tong splint will provide better immobilzation as it also prevents supination/pronation where a posterior long arm or volar splint only prevent flexion and extension.
4. Remember to make sure that the hand is placed in the position of function.
5. Though not required a stockinette provides an additional layer of skin protection and helps to make the ends of the splint looking cleaner.  It can also help hold the splint in place as you ace wrap it.
6. Finally, make sure that you document neurovascular status pre and post splint placement and if any manipulation is done you should have a follow up xray taken to ensure alignment is satisfactory.

Bladder ultrasound increases catheterization success in pediatric patients

• Next time before you attemt to catheterize a child under 36 months measure the transverse bladder diameter with the ultrasound first. 
• If it is > 2 cm you are much more likely to be successful in obtaining the specimen on the first attempt. 
• 94% when ultrasound measurement was used versus 68% patients who had conventional catheterization.

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 A recent landmark article has cited a connection between non-insulin dependent diabetes and low-level arsenic in our drinking water.

• Approximately 13 million in the USA are drinking water that contains Arsenic levels higher than EPA allowable standards
• This study controlled for organic arsenic (found in seafood) and was looking for the effect of inorganic arsenic which is the more toxic compound - don't have to stop eating sushi
• This study essentially found a dose response curve with people with lower arsenic levels having lower incidence of non-insulin dependent diabetes, those with higher levels, higher risk.

Show References

 Navas-Acien A, Silbergeld EK, Pastor-Barriuso R, Guallar E.

 

Arsenic exposure and prevalence of type 2 diabetes in US adults.

JAMA. 2008 Aug 20;300(7):814-22.

• Most studies suggest that the risk of aneurysm rupture significantly increases after the size of 7 mm.

• The risk of rupture is greater for posterior circulation aneurysms.

• Five-year risk of aneurysmal rupture based on size (for anterior and posterior circulation aneurysms, respectively):
  
  ---  7 to 12 mm --> 2.6 and 14.5%              

             ---- 13 to 24 mm --> 14.5 and 18.4%

Complications of Subarachnoid Hemorrhage

The three dreaded complications of SAH include the following:

• Rebleeding
• Hydrocephalus-occurs in as many as 33-50% of patients with SAH. Intraventricular blood (in 20% of cases) acutely occludes the foramen of Monroe and Luschka and obstructs CSF outflow. This is treated by inserting a ventriculostomy catheter. 
• Vasospasm-Usually develops several days after the initial SAH. May be an asymptomatic angiographic phenomenon or cause cerebral ischemia-an important cause of morbidity after SAH. Prophylactic administration of Nimodipine improved outcomes. 

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PEEP in Nonhypoxemic Respiratory Failure

• Patients with ALI/ARDS typically receive PEEP to improve oxygenation
• Patients without ALI/ARDS, however, receive PEEP less frequently (some recent reports indicate that < 50% of these patients receive PEEP)
• A recent study by Spanish investigators found that the use of PEEP (5 - 8 cm H₂0) in nonhypoxemic patients decreased the incidence of ventilator-associated pneumonia and decreased the number of patients who developed hypoxemia
• Interestingly, no differences were found in hospital mortality, duration of mechanical ventilation, or ICU LOS
• Take Home Point: In nonhyoxemic intubated patients, the addition of 5-8 cm H₂0 of PEEP is a reasonable practice and may be beneficial in preventing VAP (pending further study)

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The apical 4-chamber view of the heart on bedside ultrasound gives an excellent comparative view of the sizes of the right ventricle (RV) and left ventricle (LV). The RV is normally ~ 0.5-0.6 the size of the LV. When the RV appears too large, certainly if the RV > LV in size, it indicates RV dilatation.

RV dilatation can be chronic (e.g. COPD or sleep apnea with pulmonary hypertension, etc.) or acute (e.g. PE, RV MI). How can you tell whether the condition is chronic or acute? Just take a look at the RV free wall. If the RV free wall measures < 5 mm, it's a pretty good indication that you are dealing with an acute condition. Think PE or RV MI!

[thanks to Dr. Jim Hwang from Brigham and Women's Hospital for providing this pearl]

Olecranon Bursitis is inflammation and swelling of the bursa overlying the olecranon process of the ulna.  Can result from trauma, overuse, or infection. 

Treatment can consist of:

• Aspiration:  Can be done to rule out infection [send gram stain, culture, and cell count], and be therapeutic by removing the excess fluid.
• NSAIDs
• Local injection of corticosteroids into the bursa
• Wearing of a neopryne elbow sleeve, or ace wraps to provide compression over the bursa and may help prevent reaccumulation of the fluid.

Remember aspiration has some major risks that need to be explained to the paitent:

• Infection may be introduced during the aspiration.  [Follow aseptic techniques and ensure that the skin is adequately prepped with chlorhexidine or betadiene].
• Formation of fistula tract with chronic drainage. [Use a Z or zigzap approach to minimize this complication.]
• Ulnar nerve injury.  Avoided by using a posterior lateral approach and avoiding a medial approach.

They also need to know that the fluid will likely reaccumulate.  So aspiration is not a guaranteed cure. 

In the rush of adrenaline that goes hand in hand with a pediatric intubation often the ETT tip can sometimes be coming out of the little guys toes after passing successfully through the vocal cords, so remember once you get it in and confirm with end-title CO2 detection (capnography or on a monitor) always remember:

Depth of insertion (cm at lip) = 3 x  normal size of ETT

Start at this depth, auscultate bilaterally in the axilla to listen for equal breath sounds, and look for equal chest rise.  If all are good then secure tube and get your chest xray. 

• Cerebral aneurysms are usually not congenital, but rather often form over days, weeks, or months.  

• It is hypothesized that the critical size for rupture is smaller for newly formed aneuryms; thus, treat newly discovered aneurysms that were previously radiographically absent more proactively and cautiously.

• While hypertension and cigarette smoking are not thought to cause aneurysmal rupture, they do contribute to the problem;  Hypertensive smokers are at a 15-fold increased risk of SAH compared to non-hypertensive non-smokers.

Pressure Regulated Volume Control (PRVC)

• PRVC is a mode of mechanical ventilation that combines both volume and pressure control modes
• The main advantage to PRVC is that the tidal volume / minute ventilation is guaranteed while controlling airway pressures, thereby reducing the risk of ventilator induced lung injury
• In PRVC, the ventilator delivers a pressure-controlled breath, but tidal volume is the key setting
• The ventilator will automatically adjust inspiratory pressures until the desired TV is achieved
• When using PRVC you need to set: target TV, RR, peak pressure alarm, inspiratory time, FiO2, and PEEP

Currently Approved LMWHs for the Treatment of Acute PE:

• Enoxaparin-1 mg/kg every 12 hours subcut
• Tinzaparin 175 Units/kg once daily subcut
• The pentasaccharide: Fondaparinux- at a dose of 5 mg for body weight <50 kg, 7.5 mg for 50-100 kg, and 10 mg for >100 kg, once daily

Make sure to monitor platelet counts regardless of agent chosen.

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"The most common EKG abnormalities are non-specific ST-T wave changes, followed by RBBB. A normal EKG does not exclude the possibility of cardiac injury, although some investigators report a negative predictive value of up to 80-90%."

[El-Chami MF, Nicholson W, Helmy T. Blunt cardiac trauma. J Emerg Med 2008;35:127-133.]

Placing a foley catheter in a patient with BPH or acute urinary retention can be very difficult at times.  Here are some tips to increase your chance of a successful placement.

1. Use a Uroject lidocaine gel syringe to help anesthesize the urethra and lubricate the tract.  The lidocaine gel should be slowly expressed (injected) into the urethral meatus.  This helps to provide lubrication further down the urethra, as opposed to just wiping the catheter tip in the lubricant.
2. When using a Coude catheter, ensure that the curved tip points upward.
3. Apply gentle continuous pressure to help open the prostrate spincter.  This will be more successful than trying to ram it through which can increase spincter contracture.
4. Do not inflate the balloon until you have confirmed placement with urine return.
5. Don't forget the ultrasound.  You can calculate urinary volume (post void residual) prior to catheter placement and confirm placement with ultrasound.

If all else fails, a suprapubic catheter may need to be placed.  For a great review on evaluation and treatment please see Drs. Vilke, Ufberg, Harrigan, and Chan's article in the August edition of Journal of Emergnecy Medicine entitled Evaluation and treatment of acute urinary retention.

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Alcohol-Drug Interactions

• There are a number of medications that produce the disulfiram-like reaction when ingested with alcohol.
• The disulfiram reaction is a very uncomfortable reaction characterized by severe flushing, and may be accompanied by tachycardia and hypotension.
• Although we always think of metronidazole, there have been well described cases of bactrim causing this reaction.
• Tinidazole, a new antiprotozoal used in the treatment of trichomonas, causes this as well.
• Patients should be advised to avoid alcohol for 24 hours after metronidazole, and 72 hours after bactrim and tinidazole.

Other common medications that produce this reaction:

1. Sulfonylureas: chlorpropamide, tolbutamide, glyburide

2. Cardiovascular medications: Isosorbide dinitrate, nitroglycerin

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• About 2% of the adult population have an asymptomatic cerebral aneurysm.

• Unruptured aneurysms can cause symptoms such as headache, visual acuity loss, cranial neuropathies (particularly thrid nerve palsy), pyramidal tract dysfunction, and facial pain; these are thought to be due to mass effect on the aneurysm.

• 20 to 30% of people with a cerebral aneurysm, have multiple aneurysms; Don't miss co-existing aneurysms on CTA or MRI. 

• The majority of intracranial aneurysms are located in the anterior circulation, most commonly in the Circle of Willis.

• When localizing aneurysm on CTA and MRI, common sites include: 

              ---  junction of the anterior communicating artery (ACOM) with the anterior cerebral artery (ACA)

              ---  junction of the posterior communicating artery (PCOM) with the internal carotid artery (ICA)

              ---  bifurcation of the middle cerebral artery (MCA)

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