Pediatric emergency medicine trisk 0227 0227

The differential diagnosis of tachycardias includes sinus tachycardia (ST), SVT,
and VT. Narrow-complex morphology and beat-to-beat variability are usually
present in children with ST ( Fig. 9.16 ). Rates rarely exceed 220 bpm in infants
and 180 bpm in children. Common causes of ST include hypoxemia,
hypovolemia, hyperthermia, metabolic abnormalities, and pain/anxiety. Therapy
is directed at treating the underlying cause.
SVT can be distinguished from ST by its lack of beat-to-beat variability and
rate (most often >220 bpm in infants, and >180 bpm in children). In children,
aberrant conduction yielding a wide-complex rhythm SVT occurs less than 10%
of the time. SVT is most commonly caused by accessory reentry pathways.
Patients with stable SVT have adequate oxygenation and perfusion; those with
unstable SVT have inadequate perfusion and thus require rapid intervention.
Chemical or electrical conversion can be used for the treatment of SVT.
Adenosine is a safe and effective treatment of SVTs, it is the drug of choice when
vascular or IO access is available. In infants, verapamil can cause myocardial
depression or arrest and thus should be used only in consultation with a
cardiologist. It is optimal to obtain a 12-lead ECG prior to and during treatment
administration to aid in the diagnosis. If the patient fails to convert to sinus
rhythm after two doses of adenosine, synchronized cardioversion (0.5–1 J/kg) is
recommended. If vascular access or medication availability is delayed, consider
synchronized cardioversion early. Consider use of sedation/analgesia when using
electrical conversion as appropriate to the clinical situation. Vagal maneuvers
were reintroduced in the 2000 AHA guidelines for stable SVT. In infants and
young children, ice may be applied over the upper half of the face or rectal temp
can be taken. In older children, Valsalva maneuvers, such as knee to chest or
forceful blowing on an obstructed straw, may be attempted. Avoid ocular pressure
and carotid massage. Use of other therapies, such as procainamide or amiodarone,
or less commonly, verapamil, digoxin, or beta-blockers, may be considered after
pediatric cardiology consultation.