PEMDoc Pearls: ECGs and overdoses

by Kaynan Doctor
Children's National

[We're restarting our PEMDoc Pearls series. Each week, Kaynan Doctor--PEM fellow at Children's National--will post a few learning pearls identified from our weekly PEM conferences at Children's National. As always, comments are welcomed!]

ECG Basics with Drs. Anne Greene and Priya Gopwani

• Lead 1 and V6 should look the same in terms of axis. If they are opposite you have arm lead reversal

• When calculating QTc best to use leads II or V5. If the T wave does not return to baseline you can draw a line along the T wave and see where it intersects the isoelectric line

• In an irregular rhythm – where calculating the QTc may be difficult the gold standard would be to calculate multiple QTc values and take the average. Additionally you can look at the shortest RR interval – if this is normal then it is likely that QTc may be normal. Another strategy would be to measure the QT interval after 2 to 3 regular RR intervals to get a baseline measurement.

• The QT interval can be falsely prolonged if the T wave is combined with a large U wave. In these circumstances the T wave may appear noticed.

Notched T waves Image courtesy of Dr. Greene

Dr. Greene is a pediatric cardiologist at Children's National and Priya Gopwani is a PEM fellow. 

Toxicology: Acetaminophen and Salicylate Poisoning with Drs. Clancy and Naomi Hughes

Acetaminophen Toxicity 

• 1 in 500 Suicidal ideations will fail to disclose an acetaminophen ingestion.

• Patients presenting with an acetaminophen overdose who have co-ingested substances that reduce gastric emptying (e.g. opiates) may benefit from an acetaminophen level at 6- 8 hours in addition to the initial 4 hour level    

• Acetaminophen toxic doses

Under 6 years of age:

200mg/kg single dose
150mg/kg over 2 days
100mg/kg over 3 days

Over 6 years of age

10g over 24 hours

150mg/kg/d over 48 hours

6g/d for over 48 hours

• For chronic ingestions you cannot use the Rumack-Matthew nomogram for acetaminophen toxicity Likewise the regular plasma concentration values of between 150-200µg/ml cannot be used with IV acetaminophen due to a difference in pharmacokinetics. Values of between 60-80 µg/ml have been suggested but this is still under study.

• If you are running an acetylcysteine infusion during a transport, the transport should be at least a Charlie.

• Severe acetaminophen poisoning can cause gap metabolic acidosis

Salicylate Toxicity

• Toxic dose is >150mg/kg oral aspirin
• Toxic Levels are 60-100mg/dl or 30-40mg/dl if chronic ingestion

• Always be on the look-out for a history of  tinnitus, hearing loss and muffled hearing.

• Alkalization of urine as management for salicylate toxicity can be achieved by infusing a 20cc bolus of the following, followed by 2x maintenance:   1L of  D5W with 150 mEq (3 amps) of sodium bicarbonate

Dr. Clancy is a toxicologist at the National Poison Center and Naomi Hughes is a PEM fellow. 
 
Follow-up Rounds:

• The rule of 3’s and 9’s method of estimating head circumference as introduced by Dr. Paul Mullan:

0 mo = 35cm

3 mo = 40cm

9 mo = 45cm

3 yr = 50cm

9 yr = 55cm

• Also remember that Shaken Baby Impact Syndrome can present with an acute increase in head circumference.