Cardiac Emergencies

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Chapter 31 Cardiac Emergencies

Sarah W. Alander, MD, James Edward Hulse, III, MD

1 What are the new pediatric advanced life support (PALS) recommendations regarding the use of endotracheal tube resuscitation medications?

The IV or intraosseous (IO) route of administration is preferred. The endotracheal tube (ETT) doses of resuscitation medications are not listed in the updated advanced cardiac life support algorithm for pulseless arrest. They may be used if IV or IO access is not obtained. The thinking is that drugs administered into the trachea result in a lower blood concentration than the same dose given via the IV route. Lower epinephrine concentrations may produce transient β-adrenergic effects, leading to hypotension and reduced coronary artery perfusion pressure.

American Heart Association: Currents in Emergency Cardiovascular Care. 16:2005–2006. Available at www.americanheart.org/downloadable/heart/1132621842912Winter2005.pdf.

2 If ETT resuscitation medications are used, how does the technique differ compared with the previous PALS recommendations?

The recommended dose should be diluted in water or normal saline and injected directly into the ETT. Previously, health care providers were urged to pass a catheter beyond the tip of the tracheal tube to inject the drugs.

American Heart Association: Currents in Emergency Cardiovascular Care. 16:2005–2006. Available at www.americanheart.org/presenter.jhtml?identifier=3012268.

3 Is high-dose epinephrine still recommended in pediatric cardiac arrest?

The 2005 American Heart Association recommendation is as follows: Use a standard dose of epinephrine (0.01 mg/kg body weight via IV/IO route) for the first and subsequent doses. There is no survival benefit from use of high-dose epinephrine, and it may be harmful, particularly in patients with asphyxia.

American Heart Association: Currents in Emergency Cardiovascular Care. 16:2005–2006. Available at www.americanheart.org/presenter.jhtml?identifier=3012268.

4 What is bradycardia? When is it a significant threat to the health and well-being of patients?

The definition of bradycardia is a heart rate less than 80 beats per minute in newborns and less than 60 beats per minute in infants and children. It is significant when it results in symptoms of shock such as hypotension, acidosis, lethargy, and coma.

5 What are indications for emergency or urgent intervention in a patient with bradycardia?

Intervention is necessary in the bradycardic patient with a history of syncope or with symptoms of poor perfusion (decreased capillary refill, hypotension, and altered consciousness).

6 What are the initial steps in treatment for a patient with hemodynamically compromising bradycardia?

Assess the airway. Remove any foreign body from the airway, if present, and reposition the patient (jaw-thrust maneuver). After securing a patent airway, assist respiration with 100% oxygen, and perform chest compressions for heart rate < 80 beats per minute in newborns, < 60 beats per minute in infants and children. Give atropine (0.002 mg/kg via IV route, with 0.1 mg as minimum dose and 0.5 mg as maximum dose) or epinephrine (1:10,000, 0.01 mg/kg via IV route). Recall that both atropine and epinephrine can be given via IV, IO, or endotracheal route. However, IV and IO routes are preferred.

7 What criteria are considered absolute indications for implantation of a permanent pacemaker for rate support?

Patients with a history of syncope or symptoms related to bradycardia should not be released from the emergency department (ED) until close cardiology follow-up has been arranged. Absolute indications for permanent pacemaker include the following:

Complete heart block with history of syncope or symptoms

Heart block after repaired congenital heart disease

Heart block in an infant with associated congenital heart disease

Heart block in an infant younger than 6 months of age with a sustained heart rate less than 55 beats per minute

KEY POINTS: CAUSES OF BRADYCARDIA IN CHILDREN

1 Noncardiac: Hypoxemia (most common), central nervous system insult, sepsis, hypothermia, poisoning, anorexia nervosa, hypothyroidism

2 Cardiac: Cardiomyopathy, complete heart block, sick sinus syndrome

8 Give the corrected QT criteria for determining prolongation of the QT interval for differences between children and adults and between males and females

Corrected QT is the calculation of QT measured/√RR interval.

In children and infants, the maximum normal corrected QT interval (QTc) is 440 msec.

In adolescent and adult males, it is 450 msec.

In adolescent and adult females, it is 460 msec.

Case CL: Diagnosis and treatment of pediatric arrhythmias. Pediatr Clin North Am 46:347–354, 1999.

9 List the associated electrocardiographic findings that may be useful clues to help establish the diagnosis of long QT syndrome

Torsades de pointes

Intermittent T-wave inversions (T-wave alternans)

Notched T waves

Low heart rate for age

10 What history in a patient presenting with sudden and unexpected syncope would make you consider familial long QT syndrome?

History of sudden unexplained death in an immediate family member under the age of 30

Definite family history of long QT syndrome or familial deafness

An episode of syncope precipitated by sudden stress or startle

11 What is the first treatment for patients with known familial long QT syndrome?

First-line treatment is a β-blocker, such as propanolol (2–4 mg/kg/day). In adolescents, a once-daily dose of long-acting propanolol can be used. Treatment should be instituted regardless of presence or absence of symptoms.

12 List several reasons for an abnormally long QTc interval that is not due to familial long QT syndrome

Electrolyte disturbances such as hypomagnesemia, hypocalcemia, hypokalemia

Central nervous system insult (increased intracranial pressure, hypoxia)

Anorexia nervosa or liquid protein diets

Many drug ingestions

13 What is the most common arrhythmia in childhood?

Supraventricular tachycardia.

14 What is the usual heart rate for infants and children with supraventricular tachycardia (SVT)?

Infants with SVT have heart rates of 220–230 beats per minute. Heart rates of older children are 150–250 beats per minute.

15 What is the most likely presentation for children with SVT?

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