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Ch 17 pages 990 - 1026
Terms in this set (65)
Defibrillation is the
process by which a surge of electric energy is delivered to the heart.
The idea behind defibrillation is to
deliver a current to the heart that is powerful enough to depolarize all of its component muscle cells; ideally, when those cells repolarize after the shock, they will respond to an impulse from the SA node and begin organized depolarization, leading to cardiac contraction.
Defibrillation needs to be carried out as soon as possible in 2 rhythms
V-Fib and pulseless V-Tach, because the likelihood of its success declines rapidly with time.
Defibrillation is not useful in
asystole because there is no evidence that the myocardial cells are spontaneously depolarizing.
An AED interprets the
cardiac rhythm and determines if defibrillation is needed.
Defibrillation for biphasic devices is
Defibrillation for Monophasic devices is
When using paddles, you must always use
conductive gel on the paddles or else you will cause burns to the skin and ineffective energy delivery to the heart.
Anterior defibrillation pad placement
Negative sternum pad should be just to the right of the sternum under the right clavicle. Positive pad is just below and to the left of the left nipple.
An implanted artificial pacemaker is
not a contraindication to defibrillation. Just make sure that you do not place the defibrillation pads directly over the pacemaker battery.
If at any point you see
an organized rhythm on the monitor, check for a pulse for a maximum of 10 secs.
Do not defibrillate a patient in
a pool of water, is touching metal of any kind, and if the patient has a medication patch, remove it and wipe the area before defibrillating the patient.
If an arrest interval is prolonged
metabolic waste products accumulate within the heart, energy stores are rapidly depleted, and the chance of successful defibrillation is reduced.
vital blood flow to the heart and brain, improving the patients chance of survival.
Synchronized cardioversion is the
use of a defibrillator to terminate hemodynamically unstable tachydyshythmias.
Synchronized cardioversion involves a
"timed" energy delivery after identifying R waves on the ECG and will only deliver energy at the peak of the R wave.
The peak of the R wave is significant because
the majority of the myocardial tissue is already depolarized and refractory to outside stimulus. Delivering energy during this time period increases probability of depolarizing any myocytes that are polarized, allowing the SA to resume the primary pacemaker function.
Emergency cardioversion is indicated
for rapid ventricular and superventricular rhythms that are associated with severely compromised CO, such as rapid V-Tach or SVT.
In the field
Cardioversion is only carried out for patients whose CO is severely compromised.
Cardioversion is a
painful procedure and sedation should be considered. Medications commonly used are benzodiazepines such as Valium and Versed.
For cardioversion to work
the limb leads and the defibrillation pads must be in place in order to perform Synchronized cardioversion as the device is unable to sense electrical activity and deliver electricity through the same cable.
Artificial pacemakers deliver
repetitive electrical currents to the heart and can substitute for a natural pacemaker that has become blocked or nonfunctional.
In transcutaneous pacemakers TCP
a small electrical charge is passed through the patients skin across the heart between one externally placed pacing pad and another.
The TCP is set for
a specific rate and the energy is increased until the heart begins to respond the stimulus which is known as capture.
TCP may buy time for the
patient and enable him or her to reach the hospital in a state of optimal perfusion rather than in or near cardiac arrest.
not only cardiac muscle, but also muscles in the chest wall beneath the pacing electrode, so sedation should be used when performing this procedure.
A patient who presents with
or develops symptomatic bradycardia needs to be treated in a manner that will increase the heart rate and improve CO.
S/S that indicate a treatment of bradycardia are
Altered mental status and hypotension.
In second degree type II or third degree heart blocks
TCP is the first line treatment.
Tachycardia can have
a superventricular pacemaker site or may be ventricular in origin.
Patients in unstable tachycardia have S/S such as
Chest pain, dyspnea, hypotension, or altered mental status.
It is critical to make what distinction when treating tachycardia?
You must identify if the tachycardia is occurring due to an underlying medical condition. If you slow the heart rate of a patient whose heart is compensating for a medical condition, it may be a fatal mistake.
you should attempt to stimulate the patients vagus nerve. The most common technique is having the patient bear down against a closed glottis.
The stimulation of the vagus nerve
in turn stimulates the parasympathetic nervous system to slow the heart. Never massage both carotid arteries simultaneously because bradycardia or asystole may result.
A patient with
advanced age, CAD, and high cholesterol would not be a good candidate for carotid massage because of the high risk of thromboembolism.
Adenosine is used
to transiently induce AV nodal blockade in order to interrupt tachydysrhythmias involving the AV node.
Be prepared to see
a short run of asystole after administration of adenosine.
A heart that is stressed
by the requirements of excessive tachycardia is likely to become ischemic and is at high risk for arrest.
Cardiopulmonary arrest is the
sudden and often unexpected cessation of adequate CO.
Most cardiac arrest victims
have evidence of CAD or other underlying cardiac diseases.
The calcium channel blocker Verapamil is often used by
paramedics to achieve rate control of tachydysrhythmias.
Verapamil's mechanism of action includes
blocking conduction of electrical impulses through the AV node.
Administration of Verapamil must be reserved for
patients exhibiting narrow QRS complex tachydysrhythmias and should never be administered in wide complex tachycardias.
Instead of ABC it is now CAB in
cardiac arrest, that is CPR should not be initiated prior to the assessment of the airway and breathing in an unresponsive patient.
Proper hand position for compressions is
Fingers off the chest, and hands coming up off the sternum slightly between compressions to allow for complete chest recoil.
Do not interrupt CPR except for
Advanced airway placement, defibrillation, or moving the patient.
Early quality compressions and defibrillation
both of which are BLS, are the measures that have been scientifically proven to have the greatest success for patients in V-Fib
As soon as you reach the patient in cardiac arrest
one paramedic should ready the monitor-defibrillator while the other carries out the following steps
- Assess circulation
- Assess responsiveness
* Open the airway and assess for breathing
* Give 2 slow breaths
- Check for a pulse and check the rhythm on the monitor
Patients found in V-Fib or V-Tach are the most likely
to be successfully resuscitated if they receive timely and appropriate treatment.
Recent research indicates that even if
an organized rhythm appears in the post-resuscitation period, the presence of an immediate pulse is unlikely.
2 mins of post-resuscitation CPR is unlikely
to cause a return of V-Fib
As soon as IV/IO access is established, administer
a vasopressin drug
- Epi or Vasopressin
Whenever you give a medication through a peripheral IV line during CPR
follow it immediately with a 20-30 mL bolus of IV fluid and then elevate the extremity to facilitate delivery of the medication to the central circulation, which may take 1-2 mins.
It is important not to combine
2 antiarrhythmics such as Amiodarone and Lidocaine because this can actually cause tachydysrhythmias
If at any point there is a return of spontaneous circulation
- Assess the patients V/S
- Support airway and breathing as required
- Provide medications as indicated for regulating the HR, controlling cardiac dysrhythmias, and maintaining B/P.
Pulseless Electrical Activity PEA refers to
an organized cardiac rhythm, other then V-Tach, on the monitor that is not accompanied by any detectable pulse.
PEA includes what was once called
electromechanical dissociation and conditions in which the heart beats so weakly that it cannot produce a palpable pulse
Conditions that may cause PEA are
- Cardiogenic shock
- Cardiac tamponade
- Hypovalemic shock
- Tension pneumothorax
- Massive PE
- Drug OD
Sodium bicarbonate is in the class of drugs called
Alkalinizing agents. These drugs are used to increase the pH of blood and urine in cases such as acidosis.
Possible causes of a flat line ECG are
- Leads that are not connected to the patient
- Loose leads
- Leads that are not connected to the monitor
- An incorrect monitor setting
- Very low voltage V-Fib
- And true Asystole
If an effective cardiac rhythm is restored in the field
your next task is to make sure that the rhythm stays restored and that optimal conditions are provided to promote recovery of the patients brain from the hypoxic insult of cardiac arrest.
Once the cardiac rhythm is stable
attention turns to the patients brain and to ameliorating the effects of cardiac arrest on it.
In an intubated patient
avoid tracheal suctioning unless necessary because it may cause increased ICP.
Consider elevating the patients
head about 30 degrees after R.O.S.C to increase cerebral venous drainage.
AHA criteria for terminating CPR in the field
- The arrest was not witnessed by anyone
- No bystander CPR was provided
- Spontaneous circulation did not return after complete ALS care in the field
- No shock was administered
THIS SET IS OFTEN IN FOLDERS WITH...
Ch 17 pages 964 - 989
Ch 17 Cardiovascular emergencies
12 Lead Research Notes
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