Clinical Pearls

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Posted on 03/07/2009

What is the dose for epinepherine for severe allergic reactions?

Answer

Epi is used for severe allergic reactions and can be used in the IM or (SC administration should not be used in severe allergic reactions as there is decreased blood flow to the subcutaneous tissues and absorption is limited) or IV form. The dose for epi in allergic reactions is 0.1mg-0.5mg IM or IV.

When using Epi IM one must use the 1:1,000 concentration. This concentration is equivalent to 1mg of epi in 1cc of solution. The starting dose of IM epi should be 0.3mg-0.5mg IM every 5 min for three doses. (that means you should give 0.3cc-0.5cc of IM 1:1000 epi) If this does not change the clinical situation or the patient gets worse, one should consider IV epi.

When using Epi IV one must us the 1:10,000 concentration. This concentration is equivalent to 1mg of epi in 10cc of solution. The starting dose should be 0.1mg delivered IV over 10 min. To deliver such a small volume (0.1mg of 1:10,000 solution is 1cc) over a 10 min is difficult. So one should create a 1:100,000 concentration by taking the 1cc of 1:10,000 epi and diluting it in 9cc of NS. Then you have 10cc of 1:100,000 epi, which you can push over 10min. This should be repeated upto 3 times; then an epi infusion should be started if needed.

PS: the dose of the epi pen is 0.3mg (1:1000) IM. Epi pen JR: 0.15mg (1:1000) IM.

These calculations should never be done at the bedside: THEY NEED TO BE MEMORIZED. This can be very confusing in a stressful situation. A severe allergic reaction is bread and butter emergency medicine and needs to be mastered by all EM residents.

Posted on 02/25/2009

What are the four physical exam signs (Kanavel's signs) for diagnosing flexor tenosynovitis?

Answer

Finger held in flexion position
Fusiform swelling of the finger: AKA sausage finger (as opposed to local joint swelling)
Tenderness along the flexor sheath
Pain with passive extension of the finger

Flexor tenosynovitis is an orthopedic emergency; as it can rapidly destroy the functionality of the hand.

Posted on 02/23/2009

How might an ABG and/or VBG help make the diagnosis of cyanide toxicity?

Answer

Cyanide toxicity is suggested when the arterial-venous O₂ saturation difference exceeds 10%. The presence of severe metabolic acidosis and a serum lactate> 10 mmol/L indicates significant exposure.

Posted on 02/21/2009

What is the emergent treatment for hyperkalemia?

Answer

Elevated plasma potassium is toxic to the cardiac cell membranes and will cause life threatening cardiac conduction disease. If you have a patient with high potassium, there are four main ways to restore normal serum potassium:

Pee it out, Poop it out, Push it back into the cells, or clean out the Plasma.

This is what I mean:

Pee: Furosemide or another loop diuretic is used to excrete potassium from the urine

Poop: Sodium polystyrene is used to excrete potassium in the stool

Push it back: Albuterol nebulizer, NaHCO3, Insulin (after giving D50) will all transport potassium back into the cell and reduce the amount that is in the plasma.

Clean out the Plasma: Hemodialysis will directly remove K from the blood

Remember Calcium in the form of CaCl (in life threatening cardiac toxicity) or Ca gluconate in all other situations does not alter plasma K levels, but will help protect the cardiac tissue, by "stabilizing the cell membrane".

The following table will summarize the emergent therapy for hyperkalemia:

Therapy

Mechanism

Dose

Onset

Duration

Albuterol

Push into cells

2.5mg nebulized

15min

2-4hours

CaCl (10%)

Stabilizes membrane

10ml IV push

1min

30min

Ca gluconate (10%)

Stabilizes membrane

20ml over 10min

1min

30min

NaHCO3

Push into cells

50mEq IV

5min

1hours

Lasix

Pee it out

40mg IV

(depends on renal function)

Sodium polystyrene

Poop it out

50g PO/PR

1-2hr

4-6hr

Hemodialysis

Clean out Plasma

Minutes

varies

Insulin

Push into cells

10 units of regular

30min

4hr

Posted on 02/17/2009

What is the maximum dose of lidocaine one can use when using it for local or regional anesthesia?

Answer

The maximum dose of lidocaine depends on if it is mixed with epinephrine or if it is used by itself.

The max dose of lidocaine for local anesthesia is 5mg/kg.

The max dose for lidocaine with epinephrine for local anesthesia is 7mg/kg.

When using 1% lidocaine you have 10mg of lidocaine in 1 cc.

When using 2% lidocaine you have 20mg of lidocaine in 1 cc.

So lets do some math. Say you have a 70kg patient and he had a 10cm thigh laceration. You want to use lidocaine for local anesthesia prior to your repair. You pull out a bottle of 2%lido, and because you read this clinical pearl you know that you can use at most 5mg/kg. That means if the bottle of 2% has 20 mg per ml and your patient weighs 70 kg; your maximum dose would be 5 * 70 = 350 mg which equals 17.5 mls of 2%lidocaine. This is not much volume if you are repairing a large laceration or multiple lacerations. You may want to consider using regional anesthesia or using 1%lidocaine instead.

Some of the commonly tested complications of lidocaine are: cardiac dysrhythmias, seizures, and methemoglobinemia.

Posted on 02/14/2009

What is Seidel's sign in the context of eye trauma?

Answer

When evaluating the eye that has been subjected to penetrating ocular trauma, one should always look for seidel's sign. You should suspect penetrating ocular trauma on anyone who works with metal (shaping, hammering, etc), that now has a FB sensation of the eye. After obtaining visual acuity, and evaluating the anterior chamber without staining, one should stain the cornea with fluorescein dye. Under cobalt blue light, corneal defects will pick up green stain. The seidel's sign or the percolation sign is when one notices a waterfall-like effect of fluid percolating into the anterior portion of the eye. The significance of a positive seidel's sign is the possibility of a penetrating FB to the posterior portion of the eye. This patient should be seen by an opthalmologist immediately. A CT scan of the eye may be obtained to attempt to locate the FB. Ocular pressures should be avoided. The patient may be patched with a hard patch (or a cut off paper cup) to protect the eye; making sure the patch is applied without putting pressure on the eye.

Posted on 02/11/2009

What are the Centor Criteria for the diagnosis of acute group A B-hemolytic streptococal (GABHS) phayngitis?

Answer

The Centor Criteria is used to risk stratify patients with a sore throat that may have strep pharyngitis. Most patients with a sore throat will have a viral infection. But some may have a bacterial infection. Group A Beta Hemolytic streptococcal infections are important not to miss, as untreated strep infections may lead to glomerularnephritis. The criteria are:

Absence of a cough
Fever
Tonsilar exudates
Tender anterior cervical lymph nodes

Patients with 3 or more of the criteria should be treated for acute streptococcal pharygitis; as they are about 60% likely to have a streptococcal infection. Those with less than 3 criteria should be cultured and treated symptomatically awaiting culture results.

Posted on 02/09/2009

What are the manifestations of the following types of strokes:

Middle Cerebral Artery
Anterior Cerebral Artery
Posterior Cerebral Artery
Vertebrobasilar CVA
Cerebellar bleeding

Answer

Middle Cerebral Artery

Contralateral hemiplegia and anesthesia, Ipsilateral homonymous hemianopsia, aphasia or agnosia

Anterior Cerebral Artery

Contralateral LE paralysis and sensory deficit, gait abnormalities, bowel/bladder incontinence, AMS

Posterior Cerebral Artery

Cortical blindness, CN III paralysis, Agnosia, Alexia, AMS, memory difficulties

Vertebrobasilar CVA

Vertigo, nystagmus, dysarthria, loss of contralateral pain and temperature control, diplopia, coma, vomiting

Cerebellar bleeds/lesions

Repeat vomiting, inability to walk or stand, vertigo

Posted on 02/08/2009

What is Nagele's Rule?

Answer

Nagele’s Rule is used to estimate the patient’s estimated date of delivery. It is 9 months and 7 days after the first day of the patient’s last menstrual period. Once one knows the EDD, one may calculate the current gestational age (GA). Knowing the gestational age is clinically relavant because is will allow one to estimate sonographic landmarks on transabdominal (TA) and transvaginal (TV) sonograms. The landmarks are also loosely correlated with BHCG levels. The following table will summarize:

GA	TA landmarks	TV landmarks	BHCG
4-5 weeks	+/- gestational sac	Gestational sac	1000
5 weeks	Gestational sac +/- Yolk sac	Gestational sac with yolk sac +/- fetal pole	1000-7000
6 weeks	Yolk sac and fetal pole	Yolk sac and fetal pole with FH	10,000-23,000

Source: Emergency Medicine: A Comprehensive Study Guide 6th edition by Judith E Tintinalli (Editor), Gabor D., Md. Kelen (Editor), J. Stephan Stapczynski (Editor)

Posted on 02/04/2009

What is the significance of Lhermitte sign?

Answer

Lhermitte sign is the sensation of electricity down one's back triggered by flexion or extension of the neck. Classically associated with multiple sclerosis, it can be caused by any demyelinating injury to the cervical spinal cord.

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Source: Emergency Medicine: A Comprehensive Study Guide 6th edition by Judith E Tintinalli (Editor), Gabor D., Md. Kelen (Editor), J. Stephan Stapczynski (Editor)