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Emergency Cardiac Care

Christy McKendrew, BS, MS, EMT-P

Eric Rodgers, NREMT-P

Our courses fulfill continuing nursing education requirements in all 50 states. For more accreditation information, click here.

All material contained herein, unless otherwise cited, is based on 2005 guidelines issued by the American Heart Association. These guidelines first appeared in Circulation 112 (suppl IV).

This course is designed as a review of emergency cardiac care. If you need initial certification in basic or advanced life support, please click here to go to the AHA website. (This link opens a new window in your web browser.)

The recently published revision of the American Heart Association (AHA) Emergency Cardiac Care (ECC) guidelines represents some of the most radical changes in many years. Many peer-reviewed studies were considered and the emphasis has shifted. Ventilation and oxygenation and defibrillation are being de-emphasized in favor of well-performed chest compressions in order to maintain perfusion to vital organs and provide adequate coronary artery pressure. With early cardiopulmonary resuscitation (CPR) that is well-performed and sustained through the resuscitation process, survival rates can greatly increase.

BASIC CARDIAC LIFE SUPPORT (BCLS)

It's a simple but true statement that good advanced cardiac life support (ACLS) starts with good basic skills. The most recent guidelines for healthcare providers focus on high-quality CPR for cardiac-arrested patients.

First Response

Start by establishing unresponsiveness using the shake-and-shout method. If you are a lone healthcare provider with an unresponsive patient, your next step is determined by what type of cardiac arrest you suspect. A lone rescuer who decides that the patient has most likely gone into sudden cardiac collapse should first call the emergency response number to get an automated external defibrillator (AED), if available. If the unresponsive patient has likely gone into an asphyxial arrest (eg, in drowning), the lone rescuer should provide about 2 minutes of CPR before calling for help. If there is more than one person available, at least one person should start the process of CPR while another activates the emergency response system.

Airway

The head-tilt–chin-lift is still the preferred method of opening the airway of an adult patient. If trauma is involved or suspected, first use the jaw-thrust method; but, if ventilations are ineffective using the jaw-thrust and readjustment still does not provide an effective airway, then the head-tilt–chin-lift may be used. The head-tilt–chin-lift is performed by placing one hand on the victim's forehead while the other hand is on the chin and tilting the head back. Resist the temptation to lift up on the neck instead of the chin. This can cause hyperextension of the neck and partly close the airway.

Breathing

After opening the airway, look, listen, and feel for breathing. Place your ear over the victim's mouth to listen and feel for adequate breathing. While doing this, you should be looking at the chest to see if it rises. Do this for at least 5 seconds, but no longer than 10 seconds. If apnea or agonal ineffective breathing is detected, give two rescue breaths. Each breath should be delivered over 1 second. Use any delivery method available, such as mouth-to-mouth, mouth-to-mask, bag-mask device (with or without oxygen) or an advanced airway. A good rescue breath will cause the chest to rise. If you don't see the chest rise, readjust the airway and attempt ventilation again.

Pulse Check and Compressions

After giving the two rescue breaths, check for a pulse. The carotid is still the location of choice. Use two fingers find the trachea and slide your fingers into the groove on either side. Feel for a pulse for at least 5 seconds but no longer than 10 seconds. If a pulse is found, but breathing is absent, rescue breathing should be continued. The rescue breaths should be delivered at a rate of one breath every 5 to 6 seconds, or 10 to 12 per minute.

If no definite pulse is found, move the patient to a hard surface (eg, a backboard, the floor) and start chest compressions. If the pulse is so weak that you're not sure it's really there, start compressions anyway. A slow weak pulse will not maintain adequate perfusion and the patient can benefit from the compressions. The location of compressions has not changed. On the adult patient, the lower half of the sternum is still used. In order to get the correct compression depth of 1.5 to 2 inches, place the heel of one hand on the sternum and the other hand on top of the first, with the fingers linked. Position your body directly over the patient's chest and keep your elbows locked and arms straight.

Compressions should be fast and hard, at a rate of at least 100 per minute, and the chest should be compressed 1.5 to 2 inches. The recommended compression:ventilation ratio for adult patients is now 30:2 with less than a 10-second pause to deliver the breaths. The 30:2 ratio is based on a consensus of experts rather than clear evidence. Some emergency medical services (EMS) and hospitals have decided to give even more compressions. Ratios of 50:2, 100:2 or greater may be seen depending on the location in which you practice.

The ventilatory rate may seem a little slow to some people, with the past emphasis being on ventilation almost to the point of hyperventilation. But the decreased blood flow to the lung during a resuscitation situation will allow ventilation:perfusion ratios to be maintained with lower rates and tidal volume. Hyperventilation can actually reduce survival by increasing intrathoracic pressure and decreasing venous return.

When you push down on the chest during CPR the pressure in the chest rises, which forces blood out of the heart chambers. Allowing the chest to recoil completely between compressions is very important. When you allow the chest to recoil the negative pressure created allows blood to return to the heart. This feeds the coronary arteries and fills the chambers, so that the next compression will be even more effective. This effect is cumulative; successive compressions will continue to increase coronary artery pressure and organ perfusion. Failure to allow full recoil will result in increased intrathoracic pressure and reduced cardiac output.

In the absence of an advanced airway, pause compressions for the ventilations. Each breath should be delivered over one second and CPR should only be interrupted for them if an advanced airway has not yet been placed. After an advanced airway is placed, the compressions and ventilations should be done asynchronously, meaning continuous compressions with one breath every 8 seconds.

.When you stop compressions to deliver a breath or check a pulse, the coronary artery pressure drops quickly and must be built up again once compressions are resumed. Five cycles of the 30:2 compressions and ventilations should be delivered over approximately 2 minutes. Only then is the pulse check repeated. All BCLS and ACLS interventions are completed around the 2 minutes of CPR and pauses in compressions are kept to an absolute minimum.

Delivery of chest compressions is tiring and the emphasis on fast, hard compressions makes it even more so. Research has shown that compressions can become ineffective after 1 to 3 minutes. Rescuers may think they're doing effective compressions for several minutes after their technique has deteriorated. In order to get the best and most effective compressions, the AHA recommends that personnel be rotated every 2 minutes, or at the end of every fifth cycle.

Automated External Defibrillators

The question of when to use an automated external defibrillator (AED) is often asked. If a victim collapses of a sudden cardiac event, the AED should be applied as soon as one is available, whether the patient is pediatric or adult. If the victim is unresponsive from a respiratory event (most common in pediatrics) or from an asphyxial event, such as drowning, CPR should be performed for a period of 2 minutes prior to the application of an AED. For outside-of-hospital cardiac arrests, when the arrival of EMS has been greater than 4 minutes and CPR has not been performed, studies have shown a greater benefit to performing CPR for a period of 2 minutes prior to using an AED. Medical directors may change protocols to reflect this information.

The most recent recommendation for defibrillation is just one shock at a time, instead of the previously recommended three stacked shocks for patients in a shockable rhythm. Research shows that the average hands-off time to deliver three shocks is about 40 seconds, which allows the coronary artery pressure to fall greatly. It is also important to continue compressions until you are ready to deliver a shock. There should be no more than 5 seconds from the time of the last compression to shock delivery for the most effective outcome. The increased coronary artery pressure will make successful conversion more likely.

After delivering a shock, there is no pulse check. Chest compressions should be started immediately, and five cycles of CPR performed before a pulse check is done. Even if the patient has an organized rhythm, the compressions will not harm the patient. Most of the time if a rhythm is present, cardiac output is still too low to provide adequate perfusion, and the patient benefits from the assistance.

Another reason for the one-shock change lies in the new biphasic defibrillators. Research shows that they can eliminate ventricular fibrillation with one shock more than 90% of the time. This does not necessarily mean that a perfusing rhythm results. Asystole or pulseless electrical activity is quite common, so CPR is likely to have a greater value than an immediate second shock.

The energy doses given to adult victims have also changed:

• If using a manual monophasic defibrillator, start at 360 joules (J) and maintain at that energy setting for all subsequent shocks.
• If using a manual biphasic defibrillator with the truncated exponential waveform, start at 150J or 200J. If you start at 150J, increase to 200J for subsequent shocks
• If using a manual biphasic defibrillator with the rectilinear waveform, start at 120J. Increase the energy setting to 150J for the second shock and 200J for the third and subsequent shocks.
• If you are unsure which biphasic monitor is in use, the default consensus is 200J for the initial and all subsequent doses.

If using an AED on your unit, you should contact the manufacturer so the software can be updated and changed from the three-shock method to the current one-shock recommendation.

Adult Choking

The foreign body airway obstruction (FBAO) sequence for the adult has been simplified for both the responsive and unresponsive victim. Healthcare providers are now told to distinguish between mild and severe airway obstructions, intervening only if the obstruction is severe. The signs of severe obstruction include respiratory difficulty, poor air exchange, cyanosis, or an inability to cough or talk . Only one question should be asked: Are you choking?

If the person nods yes, position yourself behind, and wrap your arms around, the person. Make a fist with one hand and place the thumb (flat side) against the abdomen between the naval and the xiphoid process. Place the other hand on top of your fist. Using both hands with an upward and inward motion, give abdominal thrusts until the foreign body has been dislodged or the patient goes unresponsive.

If the patient becomes unresponsive, activate an emergency response before proceeding any further if you are by yourself. If you are with others, have them do so as soon as you recognize that the victim is in distress.

The steps for managing an unresponsive patient with an airway obstruction have completely changed. Studies show that chest compressions can produce intrathoracic pressures as high as or higher than abdominal thrusts. Therefore, CPR is performed as it would be for a pulseless victim—with one exception. As the airway is opened, you must look inside the mouth for any foreign body. If a foreign body is seen, remove it, taking care not to push it further down the trachea. Blind finger sweeps are no longer recommended because of the potential damage to the mouth or throat, or even to the healthcare professional's finger.

THINKING AHEAD TO ADVANCED CARDIAC LIFE SUPPORT (ACLS)

Assessment of a patient with cardiovascular compromise has been reorganized; very little has been added or deleted. Instead, an organized step-by-step approach has been offered, along with mnemonics and other memory aids. These steps can be taken while good CPR is being performed; they are divided into five quadrads.

The first quadrad encompasses the primary survey, and it has already been completed if CPR is being performed. These are the ABCD's that we have been doing for many years.

Quadrad 1

• Airway. Is it open? If not open it.
• Breathing. Is the patient breathing adequately? If not, give rescue breaths.
• Circulation. Does the patient have a definite pulse? If not, start compressions.
• Defibrillation. Attach an AED or manual defibrillator as soon as it is available and deliver a shock if indicated.

The second quadrad expands on the ABCD's and is used to perform a secondary survey.

Quadrad 2

• Airway. Remove obstructions and consider the placement of an advanced airway.
• Breathing. Support ventilation as needed and give oxygen.
• Circulation. Establish intravenous (IV) access. Apply a cardiac monitor and determine the rhythm.
• Differential diagnosis. Consider causes for the patient's condition and treat as indicated. Consider the H's, hypoxia, hypovolemia, hypoglycemia, hypothermia, hypo-or hyperkalemia and hydrogen ions (acidosis) Consider the T's thrombus, either cardiac or pulmonary, toxins, tamponade, tension pneumothorax, or trauma.

If the patient has converted to a perfusing rhythm, or if you are caring for a cardiac patient who has not yet arrested, go on to the last three quadrads.

Quadrad 3

• Quadrad 3 is the baseline treatment given for every patient with cardiovascular compromise. These are IV oxygen, cardiac monitor and fluids (as needed).

Quadrad 4

• Quadrad 4 is assessment of vital signs: blood pressure, heart rate, respirations and temperature.

Quadrad 5

• Quadrad 5 is a consideration of the elements of adequate systemic perfusion. Evaluate the tank for adequate volume and resistance. Make sure the heart can pump adequately and support as needed. Evaluate and maintain an appropriate heart rate.

THE PULSELESS ARREST ALGORITHMS

There have been very few changes to the ventricular fibrillation (V-fib)/pulseless ventricular tachycardia (V-tach) and asystole/pulseless electrical arrest (PEA) algorithms. They reflect the new BCLS guidelines, with the emphasis on continuous CPR and the importance of timing interventions to keep interruptions to a minimum.

Ventricular fibrillation (V-fib) is the most common rhythm seen in cardiac arrest victims in the out-of-hospital setting. It is a chaotic rhythm with no organization. The foci in the ventricles are firing randomly and none are conducting, ultimately causing the heart to quiver uselessly. No pumping action occurs and there is no cardiac output. V-fib may be categorized as course or fine. Course V-fib occurs early in the arrest and is characterized by more electrical activity than fine V-fib. If the patient remains in V-fib, the electrical activity will gradually decrease because of hypoxia and acidosis. Without intervention, it will progress to flat line or asystole.

Ventricular tachycardia (V-tach) may present itself in one of two ways—monomorphic or polymorphic. Monomorphic is the more common of the two types. All of the QRS complexes will have the same morphology, indicating that they originate from the same location in the ventricles. Polymorphic V-tach originates from multiple locations, causing the complexes to take on different shapes and sizes. Torsades de pointes (twisting of the points) is one of the more commonly recognized polymorphic V-tachs. V-tach may or may not have pulses, so the pulse check should be done with care. If pulses are clearly palpable, the tachycardia algorithm should be used. If pulses are not clearly felt, treat as V-fib.

The treatment of choice for V-fib/pulseless V-tach is defibrillation. Some studies show a benefit from doing 2 minutes of CPR prior to defibrillation if the arrest time has been greater than 4 to 5 minutes when the defibrillator becomes available. Defibrillate at 360J with a monophasic defibrillator, or 150J with a truncated biphasic, or 120J with a rectilinear biphasic. Start CPR immediately after defibrillation with no pulse or rhythm check.

Several activities may take place during the 2-minute cycle of CPR. If not already in place, IV or intraosseous (IO) access should be established. A vasopressor may be given as soon as venous access is available. Charge the defibrillator before the cycle of CPR is completed. Do a pulse and rhythm check at the end of the cycle. If the rhythm is no longer shockable, go to the appropriate algorithm. If the rhythm is still V-fib or Pulseless V-tach, defibrillate using 360J with a monophasic defibrillator, 200J with a truncated biphasic, or 150J with a rectilinear biphasic.

After the shock, resume CPR immediately without an additional pulse or rhythm check. Continue CPR for 2 minutes and give an antiarrhythmic medication during compressions. Again, have the defibrillator charged and ready at the end of the cycle and do a pulse and rhythm check. If the rhythm is still V-fib or pulseless V-tach, then defibrillate (360J for a monophasic defibrillator, 200J for a rectilinear biphasic, or 200J for a truncated biphasic).

The cycle is repeated with vasopressors and antiarrhythmics as long as the patient remains in V-fib or pulseless V-tach. All subsequent shocks should be delivered at the highest energy level. Intubation or the insertion of an advanced airway should be considered at this point; however, the need for intubation must be weighed against the need for continuous chest compressions. If adequate airway and ventilations are achieved by BVM, advanced airways may be deferred until the patient is more stable.

ASYSTOLE AND PULSELESS ELECTRICAL ACTIVITY (PEA)

With either of these rhythms you need to decide early whether this is a sudden unexplained event or if it is truly an end-of-life event. This is often easier to determine in a hospital setting where medical history and advance directives are more readily available. Information from family members, advance directives, hospice workers, and local protocols are considered in determining whether any resuscitation should be attempted.

Asystole, flat line, or complete cardiac standstill is often a confirmation that death has occurred. No electrical activity is seen occurring from either the atria or the ventricles, but you must confirm this by viewing at least two leads. At times, very fine V-fib can be mistaken for asystole.

Pulseless electrical activity (PEA) is not, in itself, a rhythm. There is organized electrical activity seen on the monitor that could be expected to produce a pulse but there is little to no actual mechanical activity occurring, so no pulses are being generated.

If either of these arrhythmias is present and the determination has been made to resuscitate, start CPR. Establish an IV or IO line as soon as possible. Vasopressors may be given as soon as venous access is in place.

After 2 minutes of CPR, perform a pulse and rhythm check. If asystole or a bradycardic PEA is still present, continue CPR immediately and give 1mg of atropine.

Repeat the cycle of vasopressors and atropine as long as the patient remains in asystole or PEA. Intubation or placement of an advanced airway should take place as soon as it becomes necessary. Again, weigh the benefit of continuous compressions and consider postponing placement if good ventilation is obtained with a BVM.

There is no benefit to either defibrillating or pacing with asystole.

Medication Delivery

Peripheral IV access should be established as soon as possible for the administration of medications and fluids. If access is difficult and results in delayed therapy, the IO route is now available for adults. The IO route has the advantage of being quick and easy to place. Any medications or other fluids that can pass through an IV can be delivered through an IO, and uptake is almost as rapid. The location and technique of placement depends on which device is used, but possible sites include the distal femur, humeral head, tibial plateau, and manubrium.

Should attempts at establishing an IV or IO fail, endotracheal administration can be considered as a last resort. The IV or IO route is greatly preferred because it provides a more predictable drug delivery and pharmacologic effect. Doses should be doubled for endotracheal delivery and diluted with saline, if needed, to a volume of at least 5 to 10 ml.

Medications

A vasopressor should be the first medication considered, after oxygen, in any pulseless arrest. There is evidence that vasopressors can facilitate the return of spontaneous circulation (ROSC) during a code, even though they have not been shown to increase the rate of neurologically intact survival to hospital discharge. The two recommended vasopressors are epinephrine and vasopressin.

EPINEPHRINE

Epinephrine is the most familiar and commonly given of the two medications. During cardiac arrest, the primary beneficial effects are secondary to the alpha-adrenergic receptor-stimulating properties. This causes an increase in myocardial and cerebral blood flow during CPR and increases peripheral vascular resistance. The dosing for epinephrine is still 1mg IV/IO of the 1:10,000 solution given every 3 to 5 minutes. High-dose epinephrine is no longer recommended as a routine therapy.

VASOPRESSIN

Vasopressin can be given as an alternative to epinephrine as either the first or second dose. Dosing for vasopressin is 40 units given IV/IO, one time only. If resuscitation continues for more than 20 minutes after vasopressin is administered, continue with epinephrine 1mg every 3 to 5 minutes.

ATROPINE

Atropine interrupts the parasympathetic nerve impulses in the central and autonomic nervous systems, allowing an increase in the heart rate, systemic vascular resistance, and blood pressure. It has been shown to be beneficial in asystole and bradycardic PEA although the studies of the medication are limited. The dose for pulseless rhythms is 1mg given every 3 to 5 minutes to maximum dose of 3 mg (Nursing 2006 Drug Handbook, 2006).

AMIODARONE

A few changes have taken place within the antiarrhythmic category. Amiodarone is now the preferred antiarrhythmic for V-fib/pulseless V-tach. Studies have shown that it increases short-term survival to hospital admission when compared to other antiarrhythmics and placebos. It did not increase survival to hospital discharge, nor did any other antiarrhythmic studied.

Amiodarone has multiple effects on the myocardium, affecting the sodium, calcium, and potassium channels. It is also an alpha- and beta-adrenergic blocker. It does have many side effects and interactions with other drugs and should only be given by those very familiar with its administration. The V-fib/pulseless V-tach dose for amiodarone is 300 mg rapid IV/IO push. If the rhythm has not converted after 10 minutes, it may be followed by an additional dose of 150 mg IV/IO. If amiodarone converts the rhythm, consider an amiodarone drip.

LIDOCAINE

Lidocaine is still considered an alternative for V-fib/pulseless V-tach if amiodarone is not available. Lidocaine decreases the automaticity of the myocardium, which helps to reduce fibrillation, especially in ischemic tissue. The dosing remains unchanged: give 1 to 1.5 mg/kg IV initially. If the arrhythmia persists, doses of 0.5 to 0.75 mg/kg IV push can be administered at 5- to 10-minute intervals, to a maximum dose of 3 mg/kg. If the rhythm converts, a lidocaine drip at 1 to 4 mg/min should be considered (Nursing 2006 Drug Handbook, 2006).

MAGNESIUM SULFATE

Another antiarrhythmic that can be considered with the V-fib/pulseless V-tach is magnesium sulfate. Hypomagnesemia can appear transiently in acute myocardial infarction (AMI) and is associated with ventricular arrhythmias. Magnesium is only given, however, with torsades de pointes and documented hypomagnesemia. A dose of 1 to 2 g, diluted in 10 ml D₅W, IV/IO is administered over at least 5 minutes.

Bretylium is no longer manufactured. Procainamide is no longer recommended in the V-fib/pulseless V-tach cardiac arrest patient because of the long period of infusion and uncertain efficacy in emergency situations.

ADVANCED AIRWAYS

The placement of an advanced airway can take significant time, which may cause a prolonged interruption of CPR. Healthcare providers should weigh the need for compressions against the need for an advanced airway. If adequate ventilations can be accomplished by a bag-mask device, and no immediate risk for occlusion or aspiration is seen, it may be prudent to delay placement of an advanced airway until several cycles of CPR have been performed and several shocks have been delivered. This is a major change from earlier accepted practice but, again, the current emphasis is on getting good coronary-artery perfusion pressure by doing nearly continuous compressions without any lengthy delays.

Advanced airways can include endotracheal tube (ETT), laryngeal mask airway (LMA), or a Combitube. Whichever device is chosen, it should be placed by the most experienced person available, one who has mastered the skill through practice, frequency of placement, and education. If an attempt to place an advanced airway fails, a cycle of CPR and bag-mask ventilation should be performed before any subsequent attempts are made. All equipment should be checked and be close at hand before compressions are stopped for the placement attempt.

BRADYCARDIAS

The bradycardia algorithm covers symptomatic bradycardia as well as atrioventricular (AV) blocks. The first rule of cardiac care has not changed. We will still Treat the patient, not the monitor! Many people, especially well-conditioned athletes, have resting heart rates in the 50s, 40s, or even lower. Just because the monitor shows a slow heart rate does not mean the patient needs immediate treatment. The primary and secondary examinations that have already been performed are essential to making treatment decisions. Signs and symptoms such as chest pain, shortness of breath, altered mental status, hypotension, or shock require immediate treatment. If the patient has adequate perfusion, observation may be all that is needed until a physician can do a full work-up.

Pacing

Immediate pacing is the treatment of choice for symptomatic bradycardia. Many monitor/defibrillators also offer a transcutaneous pacing function, so delays in pacing are becoming less common. Cleanse the skin and clip excess hair to enhance adhesion and conduction. Place the pacemaker pads in the recommended position, usually anterior-posterior. Be sure monitoring leads are also in place. Pacing can be very painful, so consider sedation and analgesia if it can be accomplished quickly.

The pacemaker rate should be set at a heart rate for an adult patient, usually 60 to 80 bpm. When setting the current, start low and increase until capture is seen on the monitor. This is characterized by pacemaker spikes consistently followed by a wide QRS complex. Check for a pulse that correlates with the monitor rhythm using a site other than the carotid. Once capture is achieved, increase the current another 2 mA and maintain that setting. Sedation should be considered if it was not initiated before starting. An unresponsive patient may become responsive and very uncomfortable with successful pacing.

Medications

ATROPINE

Although pacing is the treatment of choice for the symptomatic bradycardias, you may consider atropine for sinus bradycardia as well as first- or second-degree AV blocks if pacing is not immediately available. Atropine is rarely effective on high-degree blocks such as second-degree type II or third-degree and may cause further deterioration in your patient's condition. Be aware that patients with transplanted hearts don't respond to atropine because their hearts have been denervated. Currently the suggested dosage for atropine is 0.5mg IV every 3 to 5 minutes, to maximum dose of 3 mg. Be sure to give at least 0.5 mg of atropine. Smaller doses may have the paradoxical effect of slowing the heart rate even further (Nursing 2006 Drug Handbook, 2006).

EPINEPHRINE AND DOPAMINE INFUSIONS

If atropine and pacing fail, and the patient remains hypotensive, an epinephrine infusion can be considered. The dosing for an epinephrine infusion is 2 to 10 mcg/min titrated to the patient's response.

Another medication to consider in this situation is dopamine. It is a catecholamine agent with dose-related dopaminergic and beta- and alpha-adrenergic agonist activity. The dose is 2 to 20 mcg/kg/min. The effect is rate-dependent and the rate should be titrated as needed:

• Less than 5 mcg/kg/min will increase renal, splanchnic, coronary, and cerebral blood flow
• 5 to 10 mcg/kg/min will increase heart rate and contractility
• 10 mcg/kg/min will demonstrate vasoconstriction as the dominant effect

The dopamine infusion can be administered alone or along with epinephrine (Nursing 2006 Drug Handbook, 2006). Isuprel has no role at all in the treatment of bradycardias.

TACHYCARDIAS

The tachycardia algorithm has been greatly simplified. As with all of the algorithms, start with the basics of airway, breathing, and circulation and correct any problems. Obtain an initial electrocardiograph (ECG) reading as soon as possible. Remember that if the rate is less than 150 the patient's symptoms are probably not related to the rate, so look for other causes. Treatment decisions are made on the basis of three factors: Whether the rhythm is stable or unstable, whether the QRS is narrow or wide, and whether the rhythm is regular or irregular.

Stable or Unstable?

The stability of the patient is determined during the primary and secondary survey. If the patient has signs of poor perfusion—such as chest pain, hypotension, shortness of breath, or altered mental status—consider immediate synchronized cardioversion. If IV access is in place, you may consider sedation if it can be done without significant delay. The first energy dose is 100 J to 200J for monophasic machines or 100J to 120J for biphasic machines. For monophasic machines, subsequent shocks, if needed, should be 200 J, 300 J, then 360 J. There is no clear concensus about energy levels for biphasic machines. If the rhythm is PSVT or atrial flutter, it may respond to a lower dosage, so 50 J may be attempted first.

If the patient is stable and tolerating the tachycardia well, there is more time for decision making. Establish an IV if one is not already in place. Obtain a 12-lead ECG for a better look at the arrhythmia. Determine the width of the QRS complexes. This will determine the next steps of treatment. If the QRS complex is less than 0.12 second it is considered narrow; if it is greater than or equal to 0.12 second it is considered wide. If a 12-lead is not immediately available, check the rhythm in more than one lead. Many times an aberrantly conducted SVT will look like V-tach in lead II, but MCL1 will show a narrow complex.

If the QRS complex is narrow in any lead, determine next whether the rhythm is regular or irregular. With a narrow regular rhythm, vagal maneuvers can be considered, either as a treatment or as a diagnostic tool. They are generally simple to perform and are successful in about 20% of cases. However, they should not be performed if the patient has severe coronary artery disease, has had a recent heart attack, or has a reduction in blood volume. A patient with any of these conditions could experience detachment of blood clots resulting in CVA, vertigo, cardiac arrhythmias or even arrest.

Valsalva's maneuver has fewer complications than other methods but it depends on the patient's cooperation and ability perform the maneuver. Some methods to try include having the patient bear down (as if having a bowel movement), forcibly exhale while keeping their mouth and nose closed, blow into a large syringe against the plunger, or blow into an occluded straw. Carotid sinus massage must be done with great care as carotic plaques can be dislodged causing a cerebrovascular accident (CVA), or stroke. If vagal maneuvers fail to convert the rhythm, the medication of choice is adenosine.

Medications

ADENOSINE

Adenosine (Adenocard) depresses the pacemaker activity of the SA node, reducing the heart rate and the ability of the AV node to conduct impulses from the atria to the ventricles (Nursing 2006 Drug Handbook, 2006). It is also especially effective on re-entry tachycardias that involve the AV node. It has been shown to be effective in over 90% of paroxysmal supraventricular tachycardias (PSVT).

When giving adenosine for this type of rhythm, location and speed are key considerations. The half-life of this medication is only about 5 seconds, so it needs to get from the IV injection site into central circulation very quickly. The IV site should be proximal, preferably in the antecubital (AC) with the largest catheter possible. Give 6 mg IV by rapid bolus injection followed immediately by 20 ml of normal saline flush by rapid bolus injection.

If the arrhythmia has not converted after 1 minute, a second dose of 12 mg is delivered in the same manner as the first. This dose may be repeated once more, if necessary. Remember that you are chemically cardioverting the patient's heart, so conversion may be preceded by a short period of asystole, chest pain, hypotension, arrhythmias, and nausea. These side effects are usually self-correcting and short lived.

OTHER MEDICATIONS

There are a few other medications to be aware of when giving adenosine:

• Dipyridamole (Persantine) may potentiate the effects of adenosine. Because of this, a smaller dose may be needed.
• Patients on theophylline may not respond too well to adenosine, therefore a higher dose may be needed.
• Use adenosine with caution in patients taking carbamazepine (Tegretol). Higher degrees of heart block may occur with concurrent use of this medication or with methylxanthines because they antagonizes the effects of adenosine.
• Caffeine also may antagonize the effects of adenosine, so a higher dose may be needed and it is possible that the patient may not respond at all.

If the tachycardia does not convert with adenosine or if the rhythm is irregular, consider diltiazem hydrochloride (Cardizem). This medication is a calcium channel blocker which prevents the passage of calcium ions across the myocardial cell membrane and vascular smooth cells and thus slows the heart rate (Nursing 2006 Drug Handbook, 2006). It causes dilation of the coronary and peripheral arteries, which decreases afterload and reduces the workload of the heart. Cardizem should be avoided in patients with a known history of Wolff-Parkinson-White (WPW) syndrome, sick sinus syndrome, and high-degree AV blocks unless the patient has a pacemaker in place. It should also be avoided in patients receiving oral or IV beta blockers because severe hypotension can occur.

Wide-Complex Tachycardias (Regular)

The most common form of regular wide-complex tachycardias is monomorphic ventricular tachycardia. Ventricular filling time is short and cardiac output can drop quickly. Usually, adult patients will quickly become unstable in this arrhythmia. If the patient is stable, consider a trial of antiarrhythmics. Monitor the patient closely and if at any time they become unstable proceed with cardioversion.

When giving amiodarone for stable V-tach, the dosage is 150 mg over 10 minutes (Nursing 2006 Drug Handbook, 2006). This may be facilitated by diluting the drug with 20 to 30 ml of D₅W. Repeat the dose as needed until the rhythm converts, the patient becomes unstable, or a maximum dose of 2.2 g is given in a 24-hour period.

If amiodarone is not available, consider lidocaine. The initial dose is 1 to 1.5 mg/kg. Repeat 0.5 to 0.75 mg/kg every 5 to 10 minutes to a maximum total dose of 3 mg/kg. A maintenance infusion of 1 to 4 mg/min should be started if the arrhythmia converts.

Although procainamide is no longer recommended for V-fib/pulseless V-tach, it can be considered for stable V-tach. It can also be used for stable, irregular wide-complex tachycardias. Procainamide reduces automaticity in all pacemakers and slows intraventricular conduction. It also has vasodilatory effects, especially with rapid administration and high doses. Give procainamide at a rate of 20 mg/min IV until the arrhythmia is suppressed, hypotension occurs, the QRS widens by >50% from baseline, or the maximum dose of 17 mg/kg is given. If the arrhythmia is suppressed by procainamide, start a maintenance infusion at 1 to 4 mg/min.

Wide-Complex Tachycardias (Irregular)

The three most common irregular wide-complex tachycardias are a polymorphic V-tach such as torsades de pointes, aberrantly conducted A-fib, or pre-excited A-fib such as A-fib with WPW syndrome.

A polymorphic V-tach is one in which different foci of the heart are initiating the impulse. It tends to have a poorer prognosis than monomorphic V-tach and usually deteriorates quickly into a pulseless arrhythmia. It is often associated with a prolonged QT interval prior to collapse. If this has been documented, stop any medications that may prolong the QT interval, then correct problems such as electrolyte imbalance or drug overdose.

If medications are needed, consider a ventricular antiarrhythmic. If the patient is in torsades de pointes, has documented hypomagnesemia or documented long QT interval, magnesium may be considered. Give a dose of 1 to 2 g diluted in D₅W over 5 to 60 minutes. Slower rates are preferred in the stable patient.

If it is a polymorphic V-tach other than torsades, treat it as a regular wide-complex tachycardia with amiodarone. If amiodarone is not available, consider lidocaine as an alternative.

Patients in polymorphic V-tach become unstable quickly, so be prepared for defibrillation. This rhythm is usually too irregular to cardiovert because most monitors cannot synchronize to it. Treat it as a pulseless rhythm and be prepared to start compressions after defibrillation.

If the rhythm is an aberrantly conducted A-Fib, treat as an irregular narrow-complex tachycardia with the initial focus on rate control. Conversion of the rhythm can be done later under more controlled circumstances. If the patient has a documented pre-excitation syndrome such as WPW, do not use medications that block the AV node, calcium channel blockers or beta blockers; these drugs can actually increase the rate.

ACUTE CORONARY SYNDROME

Most cases of sudden cardiac death are immediately preceded by acute myocardial infarction (AMI), therefore early recognition and prompt aggressive care of this condition is very important. There are very few changes from earlier recommendations, but some of them have been further refined.

We've all grown accustomed to hearing that Time is muscle! and it remains true. The overall goal that directs all therapies and protocols is for the patient to get the treatment they need in the shortest time possible. The interval between onset of symptoms and delivery of definitive care has many stages where delay may occur. The first and longest delay is from the time of onset of symptoms to the decision by or for the patient to seek care.

We need aggressive and ongoing public education on the importance of calling 911 early. Emergency dispatchers should be trained to ask a series of questions while dispatching an ambulance. If they determine that the patient is having signs or symptoms of an AMI they should advise the patient to immediately chew an aspirin (160 to 325 mg) as long as the patient does not have an aspirin allergy or recent gastrointestinal bleeding.

Prehospital emergency medical service (EMS) personnel need to recognize an ACS immediately and deliver the patient to an appropriate facility in a timely manner. The EMS team should have protocols in place to initiate care and notify the receiving facility to prepare for a cardiac patient. Systems that obtain 12-lead ECGs and either send a copy or report the interpretation to the receiving facility can significantly shorten the time to definitive care. And, finally, the hospital emergency department should be ready to evaluate the patient rapidly and facilitate definitive care.

The first healthcare provider to encounter any patient with signs and symptoms of ACS should begin with general assessment and treatment as previously outlined in the five quadrads. Further assessment covering cardiac history, signs and symptoms, risk factors for cardiac disease, and screening for the administration of fibrinolytics must be completed in less than 10 minutes.

Specific care for ACS still includes MONA: morphine, oxygen, nitroglycerin and aspirin. Oxygen delivery should begin first and should be titrated to the patients SaO₂ levels. Even in the absence of hypoxemia, oxygen is still appropriate for the early treatment of ACS. Nonenteric aspirin, 160 to 325 mg, should be chewed as soon as possible. This may be deferred in the presence of a recent GI bleed or true aspirin allergy.

Nitroglycerin should be administered by sublingual tablet or spray as long as the patient has a systolic BP over 100 mmHg and a pulse between 50 and 100. A dose of 0.4 mg is given every 3 to 5 minutes while the symptoms persist and the vital signs remain stable. Once three doses of nitroglycerin have been given, morphine may be given for persistent symptoms.

Assessment will stratify the patient's condition into one of three categories, and this will determine subsequent treatment. If the patient has a left bundle branch block that is new, or presumed to be new, or if the patient has ST-segment elevation >1 mm (0.1 mV) in two or more contiguous precordial leads or two or more adjacent limb leads, they are classified as having an ST-elevation MI, or STEMI. Patients demonstrating ischemic ST-segment depression of at least 0.5 mm (0.05 mV) or dynamic T-wave inversion with chest pain or discomfort are classified as non–ST-elevation MI (NSTEMI). High-risk patients with unstable angina are also included in this category, as are patients whose ST elevation of more than 0.5 mm or lasts less than 20 minutes. If the patient has normal or non-specific ECG changes, they are considered indeterminate, pending further evaluation.

ST-Elevation MI (STEMI)

Most patients in this category have blockage of a coronary artery. The goal of treatment is early reperfusion to eliminate or minimize necrosis of the heart muscle. This can be done with fibrinolytics or by performing percutaneous coronary intervention (PCI). In many instances, PCI is superior to fibrinolytic administration because the restoration of vessel patency occurs more often and there is a lower rate of reocclusion. Fibrinolytics can have the advantage of being available in smaller hospitals and they are very effective when administered within three hours of symptom onset. Hospitals should have protocols in place that take into account their capabilities and available resources.

Non–ST-Elevation MI (NSTEMI)

Generally, patients with ST-segment depression do not have a complete coronary artery blockage and may not even be having an ACS. However, patients with chest pain and positive or elevated serum cardiac markers, diffuse or widespread ECG abnormalities, or heart failure have an increased risk of major acute cardiac event, or MACE. Patients displaying ST-segment depression may be having a posterior myocardial infarction (MI), and this should be confirmed with diagnostic tests. Treatment options for these patients can include beta-adrenergic blockers, clopidogrel, heparin therapy, and/or glycoprotein IIb/IIIa inhibitors, as well as early PCI. These patients should not receive fibrinolytics.

Normal or Nondiagnostic ECG

Patients with a normal or nondiagnostic ECG will seldom be having an ACS. For these patients further evaluation is needed, including cardiac markers and possibly a stress test. Consider therapies on the basis of risk vs. benefit.

CONCLUSION

This information covers the early, basic care of most cardiac patients encountered. Many factors can complicate care, including drug overdose, hypothermia, trauma, or pregnancy and are beyond the scope of this course. Providers who can expect to encounter such conditions regularly will need additional education appropriate to their situation. Remember that the guidelines for cardiac care are just that—guidelines. Local protocol should be the ultimate authority for any care given.

Posted November 1, 2006

Expires December 1, 2008

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