In order to truly understand Cardiac Emergencies it will be helpful to have a clear understanding of the cardiovascular system and it interaction with the lungs.
In this drawing, the right side of the heart is illustrated in blue and the left side in red. The heart is actually two pumps (in series) where the output of the first pump (the right side) is fed into the input of the of the second pump (the left side.) Okay, so it's "piped" through the lungs between the two pumps. The system is a "closed system," which means that the output of the second pump is then fed into the input of the first pump. And, yes, it's "piped" through the body between the two.
One of the explanations that many students have found helpful is one where we ask the class to imagine that they are a red blood cell, and we follow the cell through the entire "trip." So, if you'll bear with us, let's get ready to take a trip. We start in the right ventricle. It seems that we have just arrived with all the other blood products, when without warning, we are suddenly pushed into the Pulmonary Artery. Incidentally, arteries always carry blood away from the Heart (two "A's" artery and away.) This is the only artery in the male body that carries deoxygenated blood, in a pregnant female the placental arteries carry deoxygenated blood away from the baby. Sorry, we have this habit of digressing. So.....the blood moves away from the Heart in the pulmonary artery toward the lungs. It enters smaller and smaller blood vessels until the red blood cells (that's you) are forced to "line-up" one behind the other. As this happens, you're entering the alveoli. These are the very delicate lung tissues. Imagine a bunch of grapes. Big round healthy grapes, packed together as tightly as you can visualize. Now, because the grapes are round, no matter how tightly you pack the grapes, there will always be a space between adjacent grapes. In this "space" place a blood vessel. Remember that the grapes are three dimensional and that the blood vessels could branch off in several directions at any space. Now, construct this three dimensional grape structure so that the "skin" of the grape and the wall of the blood vessel are one membrane. Inside the grapes is air, in the blood vessels is ..............YES, blood. The membrane separating them (the air and the blood) is only one cell thick. In other words, the blood is only one cell away from the air. This is where the blood cell (you) is going to give up it's Carbon Dioxide and assume Oxygen. That smart little blood cell knows that it's supposed to give up Carbon Dioxide at this end of the journey and give up Oxygen at the other end of the journey (later on,... out in the body.) Not so. The whole "transaction" is based on a rather simple concept from Physics. That all matter seeks a state of equilibrium. For example, if you took the room that you are in right now, and constructed as water tight divider in the center of the room. Then, filled one side of the room with water. Then, removed the divider. The water would flow into the "dry" side of the room until the level of the water was at the same height in both sides of the room. So, here you come into the alveolus, with your arms full of Carbon Dioxide and a empty wheel barrow that would normally carry oxygen. At the same time, another "guy" is marching into the lungs with his arms full of Oxygen and an empty wheel barrow that would normally carry Carbon Dioxide. You get to one of those grapes and suddenly you can "dump" some of that Carbon Dioxide into his wheel barrow and he dumps some of his Oxygen into your wheel barrow, until equilibrium is achieved. If you can't get rid of ALL the CO2, or can't get enough O2, from the first guy, don't worry, the trip through the grapes is a long winding one, that will expose you to a whole bunch of "guys," and as long as they have more Oxygen than you or you have more Carbon Dioxide than they, a transfer will occur. And so, you exit the lungs, very happy, with lots of Oxygen (looking very proud and red,) and you start moving into larger and larger blood vessels until you enter the Pulmonary Vein returning to the Heart. You enter the Heart through the Left Atrium and flow into the Left Ventricle. It's at this point that we usually ask the class, "What is the purpose of the atrium." Invariably, students will respond with, "It pumps blood from the atrium to the ventricle." This answer is not completely wrong, but it is somewhat misleading. The flow of blood into the heart (all four chambers) is "passive". There's no "sucking" action that draws blood into the heart. The valves between the atria and the ventricles are normally open during diastole (at rest,) while the heart is filling. When blood enters the atria, it flows all the way down into the ventricles, until each ventricle is full, then continues to flow into the heart until each atrium is full. At this point, the atrium contracts, causing an additional volume of blood to be forced into the ventricle, increasing the pressure in the ventricle, which "helps" close the valve between the atrium and ventricle, just before the ventricle contracts. This creates a kind of "explosive" ejection of blood from the ventricle and creates the systolic blood pressure in the two large arteries leaving the heart. Now, if you have just been forced out of the left ventricle, you find yourself entering the Aorta. A large vessel that is at the top of the heart. You travel upward for a short period then find yourself "turning" downward through a part of the Aorta called the "Aortic Arch." As long as we're here, let's talk about what it does. This is going to be a lengthy digression. So if you're hungry or thirsty, why not go get a snack (or drink) and hurry back...........I'll wait.............................Back so soon? Okay, let's talk about the heart for a minute. First of all, we know that the heart is a muscle, and, when it contracts, it pumps blood into the body. But there's one part of the body that it can not "pump into" during it's contraction. ITSELF. The muscle fibers in the heart are tense at this point and all the little blood vessels in the heart are "squeezed shut" by that tension. Consequently, we have to find another way, another time to profuse the heart muscle. The heart receives blood through a process called "retrograde profusion." Most of the blood that is in the Aorta makes it all the way over the Aortic Arch and flows (through the "Descending Aorta") into the body, some blood enters smaller arteries at the top of the arch (and just outside the aortic valve) and travels into the head (and the very beginning of the heart's circulatory system.) Some is left in the first part of the Aorta (before the Arch) and, at the end of the systolic cycle, it "falls" back toward the heart and enters the heart's arterial system and profuses the heart muscle during the next diastolic cycle. This "retrograde" flow continues until the Aortic Valve closes. It has just been forced open by the flow of blood coming from the Left Ventricle during the Systolic Cycle. At the end of the Systolic Cycle, it take a few milliseconds for the Aortic Valve to close and it is during this time that the blood flows back into the heart. When you take a blood pressure by auscultation, you are listening for a change in the sound that the pulse is making as you lower the external pressure exerted on the artery. The systolic pressure is heard during the Systolic Cycle (as long as the external pressure that is being exerted is the same as, or less than, the pressure created by the heart,) it is the pressure that the blood exerts against the artery during the time that the aortic valve is opened. Immediately following the end of the Systolic Cycle, the pressure in the artery begins to drop. It will continue to drop until the aortic valve closes. When this occurs, the pressure against the artery stabilizes and the sound changes, as we continue to reduce the pressure against that artery, and it is at this "change" in sound that we record the Diastolic pressure, and it is at this point at which the Aortic Valve closes, and the heart receives NO MORE retrograde flow. Now, if the difference between the Systolic and Diastolic "numbers" is called the "Pulse Pressure," then pulse pressure is a measure of how well the heart is being profused. That is actually an over-simplification. One must consider heart rate as well, because Diastolic Fill Time (when the heart is filling) has a direct effect on the cardiac output, which might not necessarily affect blood pressure, but would affect retrograde profusion. Hey, listen, if we've confused you will all of this, write to us and we'll try to clear it all up. We just thought you might like to know. It's not really that important, at this stage of your development. Meanwhile, back in the Descending Aorta, you continue to flow down into the body (let's assume that you're going to travel all the way down to the feet.) You keep flowing through smaller and smaller blood vessels until, once again, you (a red blood cell) are forced to line up single file behind the other red blood cells. The exchange of CO2 and O2 again take place, much the same as they did in the lungs, and the return trip starts. Another digression. The question is posed, "What gets the blood back to the heart." Some of our students have suggested that it is 'blood pressure.' Think about it for a minute. If any "blood pressure" existed in the alveolus or in the capillary, the pressure would destroy the delicate tissue. The fact is that the journey into smaller and smaller blood vessels, has also served to reduce the blood pressure until once at the endpoint (alveolus or capillary) the blood pressure is non-existent. So now, the journey begins back to the heart. The veins are surrounded by skeletal muscles, and if one contracts those muscles, the blood in the vein is "squeezed" out. The veins also have valves in them so that the blood can only flow in one direction, back toward the heart. So the return of blood to the heart is not dependant on blood pressure, but movement of the extremity from which the blood is returning. If that "return" is from the lungs, negative pressure in the thoracic cavity and the fact that the blood is moving into ever larger and larger blood vessels, helps return the blood to the heart. Lack of extremity movement is one of the reasons that bed ridden people may have some swelling in the lower extremities (the heart is pumping the blood "down," but they are not walking around to help "pump" it back.) And so, the journey continues into larger and larger blood vessels until you enter the Vena Cava (a large vein that conducts the return blood flow from the body to the right side of the heart.) You flow through the right atrium into the right ventricle, and the journey starts all over. WOW, all of that and we haven't even begun to address the title of this page, "Cardiac Emergencies." Well, as mentioned earlier, a clear understanding of how the system works is a good beginning, and our intent here has been to give you a proper start. The cardiac emergency , that is addressed in an EMT-B course is a condition call angina. Defined by the "On Line Medical Dictionary," as chest pain that occurs secondary to the inadequate delivery of oxygen to the heart muscle. Often described as a heavy or squeezing pain in the midsternal area of the chest. It becomes obvious, after consideration of the above definition, why one need know how the system supplies oxygen to the heart. It is our feeling that proper treatment of any medical emergency starts with a clear understanding of how the entire system (affected by the emergency) operates. In the section on "The Human Body," we stated that the interaction of different systems would be discussed. This in one such instance. Here, the Cardiovascular system is dependent on the Respiratory system for "fuel."
Let's talk about chest pain for just a minute, cardiac chest pain to be specific. Notice in the definition above that the pain is located in the "midsternal area". Unlike most other pain in the body, this pain doesn't seem to have a specific location. As a matter of fact, one of the questions that is commonly asked of chest pain patients is, "Can you point to the pain using one finger?" Cardiac chest pain is usually so diffuse that the patient can not, and when they can it's a probable indicator that the origin of the pain is not cardiac (not enough of an indicator, however, to delay or withhold treatment according to "chest pain protocols.") So why is cardiac chest pain so diffuse? The answer lies in the fact that the heart muscle does not have any pain sensors. That is not to say that situations in the cardiac muscle can not ultimately lead to a painful condition, just that the impulse, usually interpreted as pain, is not so interpreted in the heart. The sensation, nevertheless, is still "transmitted" along afferent nerve pathways toward the brain. We agree that at one point in the body (namely, the brain) all nerve pathways come to together to "share" information. At other points in the body, nerve pathway interrelate with pathways that are serving areas that are anatomically close together. For example, pathways from the front of the heart might interrelate with pathways coming from the left shoulder or left arm. When the "message" is received by the brain, it (the brain) serves to interpret the sensation and identify it's origin (The reality is that this function, in an instance where immediate reaction is needed to correct a dangerous situation, is probably performed in the spinal column.) When the brain tries to identify the origin of the pain, the return pathway is "incomplete." The brain "knows" that the sensation came from the area of the shoulders, but can't seem to find a specific location. Consequently, the pain is "experienced" as a dull pain, a heavy sensation, or a squeezing pain, that may even radiate down the arm, but there is no clear cut return pathway to the heart. Pain, so described, is probably an indication that the patient is having an anterior wall infarct or has an inadequate oxygen supply to the anterior wall. This interaction of nerve impulses may also account for patients describing inferior wall infarcts (or inadequate oxygen supply) as "indigestion". Okay, so the pain is diffuse. What about it's intensity. Another question asked of suspect cardiac patients is, "If you could rate the pain, on a scale of 1 - 10 how would you rate your pain, assuming that 1 is very mild and 10 is very severe?" This is just a scale, so that we can better evaluate the effectiveness of any treatment performed for the patient. But to justify treating this patient we need nothing more than the existence of pain or "discomfort." Let us try to explain. Stand up. Now, raise your right foot over your left foot, and then start stomping on your left foot until you cause enough pain in your left foot to "feel" the pain in your left arm. It doesn't take a rocket scientist to understand that you are going to have to inflict a lot of pain in your foot before you feel it in your arm, probably more pain than you can tolerate. Well the heart is "inflicting" enough pain in your heart for you to "feel" it in your arm. Even if the patient describes the pain just as a "slight discomfort," the fact that the patient feels any pain (or discomfort) at all is indication enough that there is a "world of hurt" going on in the heart. So......, what would correct the situation? What would make the pain subside? Well....., re-profusing that part of the heart that is in distress would certainly be a start. Herein lies the problem. If this is "new onset" angina, the likelihood is that a partial obstruction to the cardiovascular system and some sort of additional cardiac work load (which is commonly the "trigger" that initiates angina) has rendered part of the heart oxygen deficient. If, however, as is commonly the case, the patient has ignored initial "attacks," and the condition has been left to worsen, then there is a possibility that the obstruction may be complete (or near complete) and the attack may require the intervention of a medical professional in a suitable cardiac care center. For our purposes here we will assume that this patient has had previous "attacks," that his cardiac care physician has prescribed medication, and that he has in his possession the medication that has been prescribed.
The medication most commonly prescribed for angina is nitroglycerin. Yes, it's the same nitroglycerin that they put in dynamite. BE VERY CAREFUL NOT TO DROP IT, IT MIGHT BLOW UP! Just kidding, that always gets a rise out of new EMT students. It's very safe, no risk of explosion. But is does "paint" a useful picture in the minds of new students, because nitroglycerin, when properly administered to the angina patient does indeed "blow up" the cardiovascular arteries. Not "blow up" BOOM, but "blow up" POOF, POOF, POOF, like a balloon.
Interestingly, the drug is very specific in it's effect on the human body. It seems to dilate (blow up) arteries in the heart, while constricting veins in the rest of the body. The effect we hope to achieve here is to dilate the vessels near the obstruction, allowing a larger amount of blood to pass into the affected area, and re-profuse the hypoxic cardiac tissue, thus relieving the pain. Understand that the "problem" has not been corrected. The blockage (or partial blockage) has not been removed. But, for the time being, the patient's pain has resolved. This leads a lot a patients to think that they are "better" and nothing could be farther from the truth. This patient needs to be evaluated by a physician, NOW. The administration of nitroglycerin, in the field, is accomplished by using a sublingual route, that is to say that the medication is administered by "placing" it under the tongue. In other settings, the medication may be administered by other routes (PO or IV,) but the sublingual route is the only administration route approved for EMT-B intervention. Nitroglycerin may be prescribed in either of two different forms. Tablets or Spray and both are approved for EMT-B intervention.
There are several "prerequisites" that must be met in order for an EMT to assist an angina patient in the administration of nitroglycerin. (Local protocols may differ.)
1. The EMT must have medical control. That is to say that a physician must be aware that this patient is having an angina attack, and has authorized the EMT to help administer the medication. Some states have developed a set of "standing orders" for EMT's creating an "off-line" medical control situation. This means that as long as the EMT has well documented proof that the other "prerequisites" have been met, the EMT can help administer the medication with the same authority as if he were speaking directly to the doctor (on-line medical control.)
2. Since the administration of nitroglycerin may affect blood pressure, the patient's documented B/P MUST be above 100 mm Hg systolic (some areas of the country have raised this lower limit to 120 mm Hg.)
3. The patient must be experiencing chest pain, that he describes as similar to previous events, where nitroglycerin was useful in eliminating or reducing the pain.
4. The medication that has been prescribed by the patient's doctor must be nitroglycerin (tablets or spray) administered sublingually.
5. The nitroglycerin must be prescribed to the patient that is experiencing the chest pain.
6. The patient, as a result of this administration, must not have taken more than three tablets, within this occurrence. That means that if the patient has already taken three tablets and still has chest pain, the EMT can not help administer any more medication. If, however, the patient experienced chest pain earlier, self administered up to three tablets, and the pain resolved, but now is experiencing a second bout of chest pain, the "tablet counter" has been reset and the patient is entitled to three more tablets.
7. The prescribed nitroglycerin must not be expired. Please note that the EMT is not administering the medication (only a physician can order the administration of medication by qualified personnel), but is assisting or helping the patient "self administer" a physician prescribed medication. The EMT-B is encouraged to frequently monitor the patient's blood pressure, before and after, each administration of nitroglycerin. In an attempt to minimize the likelihood of sudden drop in B/P, wait 5 minutes between doses to give the medication time to work. If the systolic blood pressure drops 15 -20 mm Hg following the administration of nitroglycerin, and the patient experiences dizziness or nausea, place the patient in a supine position, elevate the legs, and treat for shock. Discontinue further administration of the medication until blood pressure recovers and symptoms of dizziness or nausea subside, if the chest pain has not resolved.
There are some problems that the EMT may encounter.
The bottle from which the patient will retrieve the nitroglycerin is a very small bottle. Too small, in fact, to accommodate a pharmacy label noting the patient's name and the proper dosage. This label will usually be found on the box in which the small bottle was originally packed. If it is available, refer to it, to ascertain that the medication was, indeed, prescribed for this individual. All too often, however, the patient will have already discarded the box and with it the pharmacy label. If this is the case, the EMT is encouraged to exercise normal common sense and some deductive reasoning, to help assure himself that the medication was actually prescribed for this patient. The EMT is further encouraged to clearly document those reasons in his subsequent report. In either case, the subsequent documentation should also include a record of the time that he assisted with the administration of each tablet, and the reaction, or effect (in any) to each of those assisted administrations.
There may be times when the patient is unable, be it due to the level of pain, or some other unforeseen factor, to self-administer the medication. In these cases, it may become necessary for the EMT-B to actually place the medication in the patient's hand and move the patient's hand to the patient's mouth in order to place the tablet under the tongue. Be aware of, and very careful to avoid, the possibility of the patient dropping the tablet. They're very small, hard to find, expensive, and you don't want them blowing up (just kidding.) It may be necessary to actually hold the tablet with the patient in order to assure that it "makes the mark" under the tongue. Whenever handling any medication, due so with a gloved hand. This particular mediation is absorbed through the mucosa of the skin under the tongue (consequently, the patient should be instructed to allow the tablet to dissolve under the tongue, and further instructed not to swallow the tablet,) there is a possibility that a small amount of nitroglycerin might be absorbed through the skin of an ungloved hand. This is NOT a medication that has been prescribed for the EMT and there is no good reason for subjecting himself to it's possible side effects by improper handling. Passing out, secondary to hypotension is, at best, embarrassing.