Case Summary:

An ALS crew responded to a 90s man with concern for a heart attack.  They arrived to find him on his porch and he was pale, cool, diaphoretic and with a weak radial pulse.  Crew noted that patient needed immediate resuscitation, but an intoxicated person wondered onto the scene and began inhibiting their ability to provide care.  The crew called for law enforcement to assist with this person and rapidly extricated the patient to the rig due to scene safety concerns due to the presence of this intoxicated person.  Patient was complaining of chest pain and shortness of breath.  The crew quickly assessed vitals.

Initial vitals: BP 85/52,  HR 163,  RR 18,  Sat 85% RA,  ETCO2 18,  glucose 104

Crew placed the patient on oxygen and the monitor and saw that the patient had a narrow complex irregularly irregular tachycardiac consistent with atrial fibrillation with RVR.  Patient reported sudden onset symptoms right before calling 911 and has no history of atrial fibrillation.  Patient did report he has a pacemaker.  Crew placed an IV and pressure bagged 1L NS to see if the BP and/or would improve but it did not.  Crew was worried that the atrial fibrillation itself was the cause of the hypotension so they proceeded to sedate the patient with IV versed and synchronized cardiovert the patient at 100J.  The rhythm converted to a regular paced rhythm. The new HR was 108 and the new BP was 120/56.  The patient reported resolution of his chest pain and shortness of breath.  The patient remained stable for the remainder of transport to the ED.

Highlights of the case:

Scene safety always comes first.

For most critical medical patients, we want to initiate or care before extrication.  An important exception to this rule would be if the scene is not safe for some reason.  While we should never enter a scene that is dangerous, sometimes this is not apparent until after we are there.  In these situations, we should immediately extricate to a safe location and request appropriate additional resources for support.  This crew noticed that a bystander was a potential safety risk to them as well as the patient.  The correctly removed themselves and the patient from the scene and requested law enforcement come and provide support.

Is atrial fibrillation (AF) with rapid ventricular response (RVR) the primary issue or secondary to the real problem?

In all patients with AF with RVR, the first question we should be asking ourselves is if we think the tachycardia is the primary issue or is secondary to something else.  If a patient has AF but gets really dehydrated, they will present with AF with RVR but the tachycardia is secondary to being volume down and not just because the patient is in AF.  The same is true for a patient who fell or sustained a trauma.  This patient might be tachycardic because they are in AF, or they might be trying to compensate for internal bleeding and hemorrhagic shock.  The first thing this crew did was attempt to treat volume depletion with a bolus of fluids, which was perfect.  We would not due this if the patient has clear evidence of fluid overload and pulmonary edema.  Given this did not change the patients hemodynamics at all and given there was no evidence of internal bleeding, it points towards AF with RVR as the primary cause of hypotension.  If AF with RVR is the primary cause of the patients shock, we want to treat with immediate synchronized cardioversion.  There is a risk of stroke if the patient has been in AF for more than 24 hours, but there is a bigger risk of immediate adverse outcome from shock if we delay treatment.

Why does AF with RVR cause hypotension?

For the heart to pump blood effectively, it needs to have enough time to fill.  As the HR climbs faster and faster, eventually it gets to the point where the heart does not have enough time to fill between beats.  When rates exceed this point, the patient’s blood pressure drops leading to hypoperfusion of vital organs.  This is a form of cardiogenic shock.  For most patients, the heart rate needs to be greater than 150 beats per minute before the patient is likely to develop cardiogenic shock.  For example, if a patient has AF with a rate of 125 and are hypotensive, AF itself is unlikely to be the primary cause for the hypotension.  In this situation, we should be looking for alternative reasons for the low blood pressure.

Decision to sedate before cardioversion.

If you decide that a patient needs to be cardioverted, this means that they have an unstable tachyarrhythmia and most of these patients will be hypotensive.  It is important to note that our sedatives of choice in the prehospital environment, benzodiazepines, have the potential to lower the blood pressure further.  We need to balance the risk of further hypotension against how uncomfortable and scary cardioversion can be for our patients.  If a patient is so hypotensive that they are very drowsy or unconscious, the hypoperfusion of the patient’s brain from the cardiogenic shock is sedating the patient enough for us.  In this situation, the risk of cardiovascular collapse from the sedative is too great so we should not be sedating further.  If the patient is interactive, we should be providing those patients with some form of sedative since the risk of cardiovascular collapse is so much lower and they are completely aware.  This crew elected to sedate the patient with IV midazolam which was appropriate since the patient was awake and interactive.