If vagal maneuvers fail, the next step is adenosine, a very short-acting
AV nodal blocking medication. Initially, adenosine 6 mg (b)is rapidly
pushed through the IV in a site as close to the heart as possible. Patients
may experience a few seconds of discomfort, including chest pain and
facial flushing on receiving the adenosine. If the patient remains in SVT 2
minutes after receiving adenosine, a second dose of adenosine at 12 mg
(c)is administered. If the second dose of adenosine fails and the patient
remains stable, short-acting calcium channel blockers (eg, verapamil),
(e)β-blockers, or digoxin can be administered. If at any time the patient
is considered unstable (hypotension, pulmonary edema, severe chest
pain, altered mental status, or other life-threatening concerns), synchro-
nized cardioversion (a)should be performed immediately.
192.The answer is b.(American Heart Association Guidelines, 2005. Tinti-
nalli, pp 189-191.)Ventricular tachycardia (VT)originates from ectopic
ventricular pacemakers and is usually a regular rhythm with rate greater
than 100 beats per minute and wide QRS complexes. Treatment of VT is
primarily dependent on whether or not the patient is stable. Evidence of
acute altered mental status, hypotension, continued chest pain, or other
signs of shock are signs of instability. Unstable patients, such as the pas-
senger on this airplane, should receive immediate synchronized car-
dioversion.It is critical that the cardioverter be placed in the synchronized
mode, which permits a search for a large R wave and a corresponding
shock around the incidence of such a wave. A shock administered outside
of this constraint can induce ventricular fibrillation (VF).
Stable patients can be treated with antidysrhythmics. Amiodarone (a)
150-mg IV over 10 minutes is currently first-line treatment as recom-
mended by the American Heart Association (AHA). Lidocaine (d)and pro-
cainamide(e)can also be administered. Verapamil (c)should not be used
in VT as it may accelerate the HR and cause hypotension.
193.The answer is e.(Roberts and Hedges, pp 486-493.)Endotracheal
administration of drugsis indicated whenever there is a need for emergent
pharmacologic intervention in the absence of other access routes, such as IV or
intraosseous. There are a limited number of emergency medications that can be
administered safely and effectively via the endotracheal route. These include
naloxone, atropine, versed, epinephrine,andlidocaine.This is remem-
bered by the mnemonic NAVEL.Specific medications shown to be unsafe
include sodium bicarbonate, isoproterenol, and bretylium. The endotracheal
222 Emergency Medicine