He denies syncope, exertional chest pain or dyspnea. This is the first time he has experienced this sensation.
VS 98.8 F / BP 124/82 / HR 158 / RR 14 / SaO2 98%
On exam, the man appears comfortable and in no acute distress. He is awake and oriented x3. Cardiovascular exam reveals a rapid rate with regular rhythm. No murmurs, rubs or gallops are appreciated. Distal pulses +2 with normal capillary refill. Breathing is unlabored without accessory muscle use. Lungs are clear to auscultation bilaterally. No pedal edema.
A 12-lead EKG reveals a narrow complex, regular monomorphic tachycardia with a rate of 158. Bilateral IV access has been obtained.
What is the best first step in managing this patient’s tachycardia?
Synchronized cardioversion
Vagal maneuvers
Procainamide infusion at 60 mg/min until arrhythmia is suppressed
Sedation and Intubation
This patient is stable and most likely has supraventricular tachycardia, a common form of tachycardia typically caused by a reentry circuit in the conduction system. This condition most commonly presents with a narrow QRS, however the QRS interval can be >120 ms in cases associated with aberrant conduction or a fixed bundle branch block. Vagal maneuvers such as Valsalva or carotid sinus massage block conduction at the AV node, disrupting the reentry system, making them an appropriate initial intervention in these patients. Studies have shown an SVT conversion rate to sinus rhythm up to 25%, particularly with Valsalva followed by supine positioning and passively raising their legs as shown by the REVERT trial.
The EKG is unchanged. Clinical status of the patient is otherwise the same.
What is the next best step in management?
6 mg rapid IV push of Adenosine, followed by NS flush
12 mg rapid IV push of Adenosine, followed by NS flush
IV infusion of 12 mg Adenosine over 1 hour
IV infusion of 6 mg Adenosine over 1 hour
SVT that is refractive to vagal maneuvers should be treated with adenosine. Adenosine has an extremely short half-life of less than 10 seconds. It should be administered via rapid injection into a large proximal vein, followed by a normal saline flush of 20 mL and extremity elevation. Patients should be on continuous EKG monitoring during administration.
The patient reports feeling very hot and flushed, clutching his chest due to discomfort. The symptoms resolve spontaneously after just 30 seconds. There is still no change in the rhythm seen on the EKG. Vitals are otherwise stable. The patient is mildly perturbed, but is in no acute distress.
The next step is?
Retry vagal maneuvers
Increase dose to 12 mg rapid IV push of Adenosine
Repeat rapid IV push of 6 mg
Immediate defibrillation
As seen here, it’s essential that patients are warned of the significant albeit transient side effects prior to adenosine injection, which include flushing , chest pain and difficulty breathing. If the initial 6 mg dose is ineffective, it is appropriate to give a 2nd and even 3rd dose of adenosine at 12 mg. If adenosine continues to fail in converting SVT after the 2nd and 3rd attempt, you should consider other etiologies such as A-Flutter or non-reentrant SVT. It’s important to remember that larger doses (18 mg) may be needed in patients who consume very large amounts of caffeine or take theophylline, as these decrease the effectiveness of adenosine. Conversely, those receiving the injection into the central vein, a history of heart transplant, or taking the anti-epileptic carbamazepine or the vasodilator dipyridamole may need smaller doses (3 mg).
Blood pressure quickly becomes unobtainable; however, a weak pulse is palpable.
EKG exhibits a major change in rhythm, now displaying a regular, wide (>0.12 s) complex monomorphic ventricular tachycardia at a rate of 220
Immediately perform synchronized cardioversion at 100J
Start a beta-blocker
Give third dose of 12 mg rapid IV push of Adenosine
Immediately perform defibrillation at 200J
This patient has become acutely unstable, with conversion of his rhythm to a ventricular tachycardia (VT). Patients with regular, wide complex monomorphic VT and a palpable pulse should be immediately treated with 100J synchronized cardioversion.
The patient rapidly loses consciousness. Pulse is no longer palpable.
Immediately perform synchronized cardioversion at 150J
Pronounce the patient dead
Immediately perform defibrillation
Go to the supply room and retrieve an arterial line kit
The patient has continued to deteriorate, now exhibiting a pulseless VT. The best initial treatment for a witnessed cardiac arrest is delivery of an unsynchronized shock, also known as defibrillation. This should be performed as soon as possible, as decreased time to defibrillation has been shown to improve the odds for return of perfusion and survival.
What rate and compression depth should CPR be ideally performed?
120-140 per min; >3 inches
160-180 per min; 1-1.5 inches
60-80 per min; 2-2.4 inches
100-120 per min; 2-2.4 inches
In adult victims, ideal delivery of CPR should be at 100-120 compressions per minute at a minimum depth of 2 inches. Compressions >2.4 have been associated with higher rate of iatrogenic injury. It is very important to note that CPR should be performed immediately following defibrillation without a pulse recheck. Guidelines recommend CPR be continued without interruption, with assessment of pulse no more than every 2 minutes.
What is the next best step?
Start amiodarone
Deliver 2nd unsynchronized shock
Give 1 mg IV push of Epinephrine
Find another EKG machine to recheck rhythm
If after two minutes of CPR, rhythm analysis reveals ongoing pulseless VT, a second shock should be delivered at the same (maximum) biphasic dose.
What medication can be given at this time?
1 mg IV push of Epinephrine every 3-5 minutes
Alternating 1 mg IV Epinephrine and 40 U Vasopressin every 3-5 minutes
40 U IV push of Vasopressin every 3-5 minutes
0.5 mg IV push of Epinephrine every 3-5 minutes
After a second shock is delivered, the ACLS algorithm allows for initiation of 1 mg Epinephrine given intravenously every 3-5 minutes. It is very important to note that Vasopressin was removed entirely from this algorithm with the last guideline revisions.
A third unsynchronized shock is delivered and CPR is resumed.
What additional medication is appropriate at this time?
800 mg IV Dopamine
3 g IV Metoprolol
2 g IV Magnesium sulfate
300 mg IV Amiodarone
After delivery of a third shock, the ACLS algorithm recommends initiation of Amiodarone at 300 mg in patients without return of spontaneous circulation (ROSC). A repeat dose of 150 mg may be considered if necessary. If amiodarone is unavailable, Lidocaine can be considered at a dose of 1-1.5 mg/kg for the first dose, followed a second dose that is half of the first (0.5-0.75 mg/kg).
What is the most appropriate intervention at this time to reduce the risk of neurologic injury?
Targeted temperature management
Transthoracic echocardiography
Carotid doppler followed by endarterectomy if needed
Cardiac catheterization
Neurologic injury is the most common cause of mortality in out of hospital cardiac arrest, but contributes significantly to in-patient mortality as well. Studies have shown that lowering the core body temperature to 32-36 degrees C in the hours immediately following cardiac arrest improves neurologic outcomes.
In the absence of an advanced directive specifically refusing this intervention, all patients who are unable to follow commands or show purposeful movement after ROSC should undergo management of their core temperature.
