Introduction

Anatomy and Physiology Update

Assessment Techniques

Recording the Physical Assessment Findings

Cardiovascular Assessment in Specific Disease Conditions

Electrical Activity of the Heart Related to Normal EKG

References

Course Exam

Part IV Cardiovascular Drugs Update

We are including this section, because it is vitally important that all nurses be up-to-date on the cardiovascular drugs.  When assessing the heart, the nurse must take into consideration the effects of drugs upon the cardiovascular system.  This section will be concerned with the most common drugs used in a cardiac arrest situation.  Each drug will be presented along with its uses and other helpful information.

During a code, or cardiac arrest, it is not unusual for even the most experienced nurse to have fears concerning the administration of these potent drugs.  Since this is a life and death situation, the nurse must learn not to be overwhelmed by the numbers of new drugs being used today.  Be sure to study the drugs before the code and not during.  Some of these drugs will be new to you and others have been around for a long time.  It wouldn’t hurt to study these drugs, see if they have any new uses of which you are not aware.

1. Sodium Bicarbonate: corrects metabolic acidosis during a cardiac arrest.  It is administered by IV push in a dose of 50ml, D5W solution, 44.6mEg of sodium bicarbonate.  Metabolic acidosis occurs after the heart stops, due to a buildup of the acid waste materials in the body.  This condition will be corrected by regularly administering (approx every 10 minutes) the sodium bicarbonate.
   
   Defibrillation will be more affective if the body pH is adjusted, so will other drugs be more affective.  Arterial blood gas results will tell you the patient’s pH and if it needs correcting.  Do not administer too much sodium bicarbonate, as alkalosis may occur.  If alkalosis does occur, the patient can develop arrhythmias and other problems.
   
   
2. Lidocaine: is used for reducing the irritability of the heart muscle.  Specifically it treats the PVC’s and other ventricular arrhythmias.  The drug is usually administered intravenously, but in an emergency it can be delivered via ET tube, intratracheally.  The usual dose is 50 to 100 mgm IV push, followed by a continuous IV drip.  The continuous drip helps to overcome reappearance of the arrhythmia.
   
   It is usually mixed in the following ratio: Lidocaine 2Gms/50ml of D5W, delivers 4mg per ml 60 gtts/min gives 4mg/min
   
   
3. Epinephrine: is a potent stimulant.  It increases the contractility of the myocardium and stimulates spontaneous contraction.  It is administered IV push or via the ET tube when necessary. The dosage is 0.5mg to 1.0 mg (5 to 10 ml) of a 1:10,000 solution.  This drug in the smaller dose above can be given intracardiac as well.  This drug will also in certain conditions, make the myocardium susceptible to defibrillation.
   
   
4. Dopamine: is used for the treatment of insufficient cardiac output and for hypotension. 
   
   Dopamine is often preferable during codes because it also acts as a vasodilator, brining better circulation to the brain, myocardium and the kidneys.  The main action of this drug is due to its alpha receipt stimulation effect.  This increases blood pressure and cardiac output.  The usual dosage is 2 to 5 mcg/kg/min given in a continuous IV drip.  The dosage can be as high as 50 mcg/kg/min.  Dopamine is mixed: 400mg (2x 200mg vials) in 500ml of D5W.  This results in 800 mcg/ml.  15gtts/min of this solution would result in 200 mcg/min.  The blood pressure should be monitored closely, every 5 to 10 minutes at the beginning of the infusion and while the dosage is being adjusted.  Once stabilized, the blood pressure need be taken only as often as clinical signs warrant, approximately every half hour or one hour. Urine output should also be monitored; dopamine will cause greater kidney perfusion, but output will still need to be monitored for persistent renal failure.
   
   
5. Atropine: is a cardiac stimulant. It is used for severe cases of Bradycardia.  The drug is administered by IV push, slowly.  The action is that of blocking the vagus nerve.  The smallest dose to give is 0.5 mg, if a smaller dose is given it may have the opposite effect and cause further slowing of the heart.  The dose is then repeated every 5 minutes for up to 4 doses (2.0mg). Atrpine will usually not be given if the patient has had an acute MI.  With atropine the heart rate is increased which causes increased oxygen demands upon the myocardium.  MI patients usually cannot tolerate added oxygen demands. 
   
   
6. Isoproterenol: Isuprel is used to combat sinus Bradycardia; infused in a drip solution containing 2mg (2-1mg ampoules) in 500ml of D5W which gives dilution of 4mcg/ml. dosage range is 0.5 mcg/min to 5mcg/min.  and then the patient is titrated as the patient improves.  Very similar to atropine, the oxygen demands must be considered when using Isuprel.
   
   
7. Procainamide: is usually administered IV push at a dosage of 100 mgm pushed at a rate of 20mg/min so as not to be given too rapidly the drug is used to stop PVC’s and is the second choice if Lidocaine fails.  The above dosage can be repeated every 5 minutes, up to a dose of 1 gram.  If adverse effects occur, such as hypotension or widening of the QRS complex, then the drug should be stopped immediately.
   
   
8. Calcium Chloride: this drug is administered IV push at a dose of 5 to 10 m. at 1ml/min.  It is used to stimulate the heart to make a more forceful contraction.  In cases of asystole, the drug can be used to start spontaneous contractions. The drug can also be used in cases of electromechanical dissociation, a condition in which electrical impulses are being produced by the heart, but the heart does not respond to them.  On EKG, it seems like the heart s should be beating just fine.  However, the patient has not effective contractions.  Calcium Chloride can be given in order to make the heart respond effectively.
   
   
9. Verapamil: is one of the newer drugs which are in common use today.  It is a calcium channel blocker (also classified as slow channel blacking agents or calcium antagonists). Verapamil and others in this group are used for slowing conduction of the heart’s electrical impulses and treating such arrhythmias as atrial flutter, atrial fibrillation, atrial tachycardia and for supraventricular tachycardia. 
   
   The drug is also used for angina and the group of drugs being investigated for treating other disorders; such as hypertension and cardiomyopathy.
   

The drugs in this class have many different and varied chemical structures but they all perform the same function they inhibit calcium flux across the cell membrane the drugs do not seem to affect sodium flux or any other electrolyte in eh cells. Calcium, as you k now, is important for the contraction of all muscle cells, especially cardiac cells.  Some cells are more dependent upon calcium than other cells.  They do not all utilize it equally.  Therefore, cardiac muscle cells react differently to each of the drugs in this class. There are many different effects which can occur because of this action; it depends upon:

1. Which cardiac cells are affected by the slowing
2. The chemical structure of the particular blocker drug being used
3. The dosage
4. The route of administration
5. The extent to which that particular cardiac cell depends upon calcium

Verapamil and some of the others in the class affect the SA node and the AV node.  It depresses the SA node and also slows conduction through the AV node.  The overall effects of Verapamil are:

1. Negative chronotropic effect (slowed SA rate)
2. Negative dromotropic effect (slowed AV conduction)
3. Prolonged PR interval on EKG
4. Decreased myocardial contractility

Another effect of this group is usually coronary artery dilation.  The blood flow through these arteries is increased by relaxing the smooth muscle of the vessels.  Therefore, the drug can be useful for treating angina.  In addition, myocardial oxygen consumption is reduced because both the preload and after load are decreased. Of course, just the fact that the heart rate is reduced, however the work load on the heart.

The side effects of these drugs can be severe. They are related to the way in which the drubs work.  The drugs will have a systemic effect on the body.  Peripheral circulation is also affected, resistance is decreased and peripheral blood flow is increased.

Possible side effects are:

More serious:

1. Hypotension
2. Bradycardia
3. AV heart block
4. Dizziness
5. Headache
   

Less serious:

1. Dysestbesias
2. Constipation
3. Pedal edema
4. Vertigo
5. Flushing

Dosage of Verapamil: 60 to 80 mg PO Q8 hours

75 to 150 mcg/kg IV…or continuous infusion at: 0.005 mg/kg/minute

1. Nifedipine: (Procardia) is another calcium blocker drug. Actions and side effects are very similar to Verapamil.

Dosage: 10 to 30 mg PO Q4 to Q8 hours; 10mg SL

Caution must be observed when administering this drug.  If given to patients with refractory angina pectoris, the “coronary steal syndrome” may be set off.  This syndrome has been observed in patients taking this drug and also taking combinations of nitrates and beta blockers at the same time.  The syndrome is characterized by multiple episodes of chest pain, about 30 minutes after taking a dose of nifedipine.  It is used when the combination of drugs reduces the coronary perfusion pressure too greatly.  This can cause blood to be diverted into the extremely dilated systemic arterioles.  By slightly reducing the dosage of the drug, less dilation will occur and the syndrome is usually relieved.  Symptoms of the syndrome could include, (in addition to chest pain), hypotension and reversible myocardial ischemia.

1. Diltiazem: (Cardizem) is another calcium channel blocker.

Dosage: 60 to 90 mg PO Q8 hours

   75 to 150 mcg/kg IV

Note: each calcium antagonist drug has its own particular uses. 

Each MD will use one o the drugs as they have had success with treatment.  In the near future you will see many more uses for the drugs, as research progresses.  Before you administer any of the drugs be sure to read the literature concerning that particular drug, including its side effects.

1. Bretylium: is also one of the new drugs in common use today.  It works directly on the heart to slow the refractory period allowing the heart to have a longer recovery period between beats.  This drug is used for some of the life-threatening arrhythmias in which there is no response to Lidocaine.  Some physicians prefer Bretylium of Lidocaine for its effect upon the heart.

Dosage: 1 to 8 mg/kg per minute IV (push or infusion)
(given IV push slowly, 1 or 2 mg/kg/minute)

It is used to control severe ventricular arrhythmias such as ventricular tachycardia and or ventricular fibrillation.  Bretylium is supplied in ampoules of 10ml which contain 500 mg and can be sued for IM or IV injection.

1. Bobutamine: is similar to dopamine in that they both increase contractility of the myocardium.  It can be used to treat hypotension and/or shock.  Dobutamine (Dobutrex) works directly on the heart muscle to increase cardiac output, whereas dopamine works indirectly via the kidneys.  Dobutrex, thereby, does a better job increasing the cardiac output; but dopamine treats hypotension better. 

Dosage: 2.5 to 10 mcg/kg/min is administered by infusion only and must be reconstituted from a powder just before use.

Summary

Presented here are the most basic drugs used today in code or emergency cardiac situation. This list will vary with each hospital and each physician.  However, once you as the nurse becomes familiar with these drugs, it will be easier for you to respond to that tense situation. During a code, try to anticipate the next drug that will be given.  The nurse giving drugs during a code should have several bottles of D5W ready to be missed with infusion drips if necessary.

Be aware that there are also pre-mixed infusion available today with the more common infusions such as dopamine and Lidocaine and others.  If your hospital used these pre-mixed solutions have them handy for use.  Also ask the MD how often the sodium bicarbonate is to be administered during the code.  Some doctors will want to be reminded every 5 to 10 minutes so he/she can evaluation the patient for the need of the “bicarb” and MD’s will say to give it automatically every 5 to 15 minutes during the code.

Make sure that you know the protocol at your facility for administering the various drugs.  For instance, the proper strength for missing drugs and infusing them, not to mention the correct route. 

Remember that some prefer to use Bretylium before Lidocaine, however more MD’s will try Lidocaine first.

Other Cardiovascular Drug Updates

1. Vascor, Bepridil, a new calcium channel blocker is up for approval by the FDA.  It will be marketed by McNeil Pharmaceuticals as a treatment for chronic stable angina pectoris.  It has a much longer effect than all other calcium blockers so far.  The patient will take the drug only once a day in 300mg to 400mg doses.  So far, studies show that the drug significantly reduces the frequency of angina attacks and the consumption of nitroglycerin tablets.  The side effects are nausea, dyspepsia, diarrhea, dizziness and nervousness, not unlike the side effects of many of the other calcium blockers.  The company also reports that this drug may be safely used in combination with other drugs commonly used by these angina patients (AJN, 91).
   
   
2. Rare reaction to Verapamil One patient using the calcium channel blocker, Verapamil, (Calan, Isoptin), developed myoclonic dystopia from the drug.  The symptoms were uncontrolled, irregular, symmetrical jerking movements of the arms and legs with accompanying twisting movements of the trunk (AIM).  The patient was also taking nitroglycerin, a diuretic and a potassium supplement drug at the same time.  It is unknown the exact cause for the problem but another calcium blocker as substituted for the Verapamil and the problem stopped.
   
   
3. Norpace-Induced liver damage Norpace is commonly used antiarrhythmic agent. It is used for ventricular arrhythmias such as PVC’s.  The normal side effects and include antcholinergic reactions such as dry mouth, blurred vision, urinary retention and also constipation.  Some patients experience sever hypotension and congestive heart failure.  Liver enzyme abnormalities have been reported and even Norpace-induced cholestatic jaundice.  Recently, a case of direct hepatocellular toxicity has been reported.  It is the first case ever reported.  The treatment was to withdraw the medication.
   
   
4. Long-term Amidarone therapy – amiodarone is a very new antiarryhthmic and antianginal drug. The drug contains 75 mg of iodine per 200mg tablet and recent studies have shown it can cause thyroid dysfunctions.  These include hyperthyroidism (most commonly), goiter or hypothyroidism. The extent of the problem depends upon the “normal” intake of iodine by the person from the environment (foods).  Persons who already have sufficient iodine intake would be prone to develop hyperthyroidism faster and more severely.  The problem is that the drug causes T4 levels to increase and causes T3 levels to decrease.  Patients on short-term therapy seem to be affected the most.  The hormone levels seem to g back to normal in about 3 months, even if ht patient continues the drug.  More studies are being done on this new drug to determine why there is such a fluctuation in the hormone levels.
   
   
5. Levarterenol (Levophed) this drug is also called Norepinephrine, a naturally occurring catecholamine.  It is used really today because there are several other drugs which are preferred by most physicians. However, in some areas of the country, this drug is still used quite extensively.  It is a potent peripheral vasoconstrictor.  An alpha-receptor stimulating agent, it results in an increase in the blood pressure.  The drug is also a powerful beta-stimulating agent which works mainly upon blood vessels.  It also causes coronary vasoodilatoin.  Bevophed is also used in peripheral vascular collapse, manifested by hypotension.  However, this drug is used only in the absence of significant peripheral vasoconstriction.  Levophed works will in hypotension. But it will also cause renal and mesenteric vasoconstrtion.  This is why a drug such as dopamine usually is preferable over levophed.
   
   For the use of this drug, see the directions packed with the drug.  It usually supplied in ampoules of 4ml of a 0.2% solution.  Each ampoule contains 8.0 mg of Levophed.  It is usually mixed by adding two ampoules in a liter of D5W.  This produces a concentration of 16mg/L, or 16 uGu/ml.
   
6. Verapamil (Calan, Isoptin) another calcium antagonist, is used for flowing arrhythmias such as atrial flutter or fibrillation or supraventricular tachycardia.  Recently, it has been used for angina. 
   
   Nursing Implications:
1. Dose: 60 to 80 mg PO Q8 hours OR 75 to 150 mcg/kg IV
2. Possible headache, hypotension, AV block, constipation
3. Can also be given as a continuous IV drip at 0.005 mg/kg/minute

Verapamil Update: Verapamil Decreasing Efficacy

A 68 year old man suddenly stopped responding to his ordinary doses of the calcium channel blocker Verapamil.  For two years he successfully used oral Verapamil, 240 mg/day, to prevent the episodes of the supraventricular tachycardia. 

Then he was hospitalized with fever and leucopenia.  Intravenous gentamicin and carbenicillin were started; he continued taking the oral Verapamil. On the first hospital day, supraventricular tachycardia developed, and reverted to sinus rhythm only after injection of 2.5 mg of Verapamil. His oral Verapamil dosage was increased to 360 mg/day, but tachyarrhythmia episodes recurred.  On the second and third hospital days, 5mg and 10mg of IV Verapamil, respectively, were needed to reverse the arrhythmia.

By the fourth hospital day, arrhythmia could not be controlled even by 30 mg of IV Verapamil; infused over one hour, followed by 0.5 mg of dioxin.  Finally, reversion to the sinus rhythm was achieved with the IV administration of the antiarrhythmic, amiodarone, cardarone, 150 mg.  The man was placed on a regimen of oral amiodarone, 400mg/day and his heart remained in sinus rhythm during a one-month follow up (AJN, 86).

When a drug or hormone is administered repeatedly, resistance to its effects can build up gradually.  The phenomenon is known variously as tachyphylaxis, refractoriesness, desensitionzation and tolerance.

Pediatric Doses

1. Sodium bicarbonate: 1ml (1mEq) kg; repeat dose after pE and base deficit determinations’ are made.
2. Epinephrine: 0.1 ml/kg of 1:10,000 solution, maximum 0.1 ml to 1:10,000 solution – 0.01mg or 10 ug.
3. Atropine: 0.01 – 0.02 mg/kg IV
4. Lidocaine: infants: 0.5 mg/kg, children: 5.0mg or approx 1 mg/kg may be repeated as needed.
5. Calcium Chloride: IV infusion: minimal dose of 1ml/5kg (20mg/kg) intracardiac: 1 ml/5kg diluted 1:1 with saline.
   

Next: Part V: Cardiovascular Assessment in Specific Disease Conditions