Friday, June 15, 2012

Shock Me To Death

There's nothing like watching a TV show and seeing medical personnel come in with the paddles (even these are rarely used) to shock a patient. Many people say this is "jump-starting" the heart and this is really the wrong clinical picture to give as far as medical accuracy is concerned. The use of electricity on the heart actually stalls it.


How could that possibly be helpful to a patient?

Heart cells are very unique, cool little contraptions. Each cell in your heart can generate a beat. Yes, that’s right, every little teeny one. Most often, the normal conduction system of the heart overrides this unique property of heart cells, and the electricity flows from the AV node to the SA node so the heart contracts in a normal, orderly fashion.
Heart Cells: Douglas Cowan, Children's Hospital Boston
The heart's normal beat is important because when the top (the atria) contract, it pushes the remaining blood that doesn't flow via gravity when the valves open into the ventricles. When the ventricles contract, it pushes blood out to the rest of the body.

The purpose of blood flow is really oxygen delivery to the cells. Of course, there are other functions but this is primary. Without oxygen delivery to the cells, cells will die. Lack of oxygen delivery to the cells is called shock.

We'll talk more about shock in later posts.

Defibrillation (or unsynchronized cardioversion) is only used in a few arrhythmias. Ventricular tachycardia and ventricular fibrillation. These arrhythmias appear when something has affected the heart's normal conduction system-- such as a heart attack, electrical injury, lack of oxygen. They are more common to the adult population than to the pediatric.

In these arrhythmias, the heart's normal conduction system is no longer working properly and other cells in the heart become active in an attempt to keep the patient alive. The problem with these arrhythmias is that they do not produce a pulse.
No pulse is clinical death. So, we must get back the patient's pulse back in order for them to have a chance at survival.

What defibrillation actually does is stop the heart by briefly terminating all electrical activity in hopes that the heart's normal conduction system will begin to work and a palpable pulse will then ensue.

Important note-- there must be some electrical activity for defibrillation to work. So, it is not indicated for the treatment of asystole or when the patient has "flatlined". This is done often in television shows and is a clear medical inaccuracy.

Electricity is also used in another condition called supraventricular tachycardia (SVT). Supra means above. So this rhythm is a very fast rhythm generated somewhere in the atria. Sometimes, when the heart beats incredibly fast, it doesn't have enough time to fill with blood. When it fills with less blood, it pumps less blood out. Less blood out means less oxygen delivery. The patient can have signs and symptoms of lightheadedness, dizziness, sweating, chest pain, and difficulty breathing to name a few. They still have a pulse though it may be weak and thready.

The goal of using electricity in this instance is again to disrupt this pathway by stalling it in hopes that the heart's normal conduction system will take over at a much slower rate.

There is also a medication that can be given that will chemically stall the heart, too. It is called adenosine and is used in the stable patient presenting with SVT. It is used in instances of fast rhythms to slow the pulse down.

Does this change your impression of how defibrillation really works?


  1. The heart is a fascinating creation of God's! It amazes me every time I read about or study it. I did not know that about the heart cells and that each one can generate a beat. It makes perfect sense for each cell has a design and purpose.

    When you use the term to describe the pulse reading as "thready," what do you mean by that?

    So if a pulse is present would cpr be the only method of choice or are there others? Say if my character was a nurse. I'm guessing your answer would be different if it were a layperson ( an ordinary concerned citizen/ good samaritan)

    1. Hi Miriam!

      Yes, the heart is indeed a fascinating organ-- as is the rest of the body-- truly how intricate it is.

      To answer your question-- feel your pulse at your wrist now. It should feel full, and strong. A thready pulse implies that it is not as full as normal-- thin, harder to feel, lower in amplitude.

      If a pulse is present then no CPR is required (unless the rate is less than 60 for children). Electricity is used when there is a certain rhythm but it is not generating pulsatile flow or a rhythm where the pulse is too fast that the patient can't tolerate.

      So-- it depends on the rhythm and how the patient/character feels that would determine how the nurse/character would respond.

  2. What is done, then, for a patient who has flatlined?

    1. A patient who has flatlined-- is asystolic-- and has no electrical conduction at all gets good CPR and drugs. Drug of choice for asystole is epinephrine (adrenaline) every 3-5 minutes.

      Really, the medical team needs to figure out why the patient is asystolic-- or what led to the code event. This is what needs to be reversed to "get the patient back".

      These things can be acidosis, hypothermia, hypovolemia and electrolyte imbalances to name a few.

      However, most patients will not survive this rhythm despite all efforts. It is generally a terminal rhythm and unless there is good reason for the medical team to continue, often times asystole will also mean the end of the resusitation effort.

  3. I take meds to keep SVT regulated. We found it just after I turned 40 and had most of those symptoms. It would be be okay with me if I never had to be de-fibbed. ;-)

  4. Wow, Paula!

    Yes, it is no fun getting defibbed. I did give adenosine once to a conscious male (which stops the heart chemically). It didn't terminate his arrhythmia and he felt so bad from the effects of his heart not beating those few seconds that he signed out AMA.

    Your body really likes your heart to keep beating and definitely speaks up when it stops!!