Cardiac Emergencies on Board
<HTML><p><table cellpadding="0" cellspacing="0" border="0" align="right"><tr><td width="8"></td><td valign="top" align="left" width="184"><img src="http://www.sailnet.com/images/content/authors/mahaffy/050400wm_cardiac1.jpg" width="184" height="272"><br><div align="left"><font color="#318e5a" size="-1"><b>Sailing is likely to make getting to medical facilities a lengthy endeavor. A prepared crew is essential in the event of a medical emergency.</b></font></div></td></tr><tr><td height="8" colspan="2"> </td></tr></table>Statistics for cardiac emergencies occurring in the marine environment are difficult to come by. However, conventional wisdom coupled with experience and personal knowledge of the industry lead me to the conclusion that heart attacks and other cardiac emergencies are not common maladies in the sea-going population. In my opinion, this may be because sailing enthusiasts, generally, have a healthy lifestyle and are attracted to the nautical world for its physical, emotional, and spiritual benefits. This is certainly not to say that all sailors are non-smoking, sprout-eating marathon runners with cholesterol levels below 170, but rather it is a broad observation on the type of individuals attracted to sailing as both a sport and a way of life.<p>This is all well and good since an onboard cardiac emergency is difficult to manage and will require diagnostics and intervention found only in a hospital setting. Fortunately, there are a few simple steps you can take to deal effectively with such a problem.<p><b>Heart Attacks: What Happens?</b> The term <i>heart attack</i> is a broad term used to describe damage to the heart muscle (myocardium). Even though the heart is basically a "blood pump", it will help to review some specifics of the cardiac system. Those of us who work in the cardiac specialties[The author is a Physicians Assistant specializing in Cardiology.] actually think of the heart as "two" hearts: the right heart and the left heart. This is because a muscular wall (the septum) separates the two sides and each side has a similar but distinctly different function. Each side is also subject to similar but distinctly different problems. <p><table cellpadding="0" cellspacing="0" border="0" align="right"><tr><td width="8"></td><td valign="top" align="left" width="222"><img src="http://www.sailnet.com/images/content/authors/mahaffy/050400wm_cardiac2.jpg" width="222" height="244"><br><div align="left"><font color="#318e5a" size="-1"><b>Knowledge of what to do in the event of this kind of equipment failure is an important part of a sailing regimen.</b></font></div></td></tr><tr><td height="8" colspan="2"> </td></tr></table>The heart is composed of four chambers: two on the right, two on the left with an upper (atrium) and lower (ventricle) chamber on each side. The right heart is responsible for collecting all of the used (deoxygenated) blood that has circulated through the body and pumping it to the lungs for a "reload" of oxygen. The right heart is a relatively low-pressure system since the lungs (the pulmonary circuit) offer a low resistance. The rejuvenated blood then moves to the left heart via the pulmonary veins. Interestingly, these are the only veins in the body that carry oxygenated blood. This is because the true definition of a vein is a blood vessel that carries blood <b>toward</b> the heart. The left heart now takes over and the real work begins. The left ventricle is the most amazing muscle in the body. It is responsible for pumping blood out to the entire body from the moment of birth until death. It has it's own "pacemaker" and controls the heart rate and rhythm without any conscious input from its owner. This is one reason why a transplanted heart will work in a recipient even after all of the nerve connections have been separated.<p>The heart muscle has all of the same requirements as any other muscle. It needs oxygen and nutrients to maintain function, and it must be able to get rid of carbon dioxide. The coronary arteries are responsible for supplying freshly oxygenated blood to the heart muscle. In fact, the heart is the first organ to see these oxygen-rich blood cells, since the entrance to the coronary arteries is just millimeters past the exit from the left ventricle. Fresh blood will flow down the coronary arteries while the heart is between beats (diastole) and release its load of oxygen to the cells. The used blood will then travel back through the cardiac veins to the right atrium for another go-round.<p>It is when these coronary arteries become narrowed that the problems begin. A variety of causes contribute to the formation of coronary blockages, known as coronary artery disease or CAD. Age, gender, weight, diet, lifestyle, diabetes, smoking, and family history are some of the major contributors. Unfortunately, of all these, family history is the most potent indicator for CAD and is the reason for much of the recent excitement over discoveries in the field of gene therapy. <p>CAD is essentially the narrowing of the coronary arteries in response to plaque buildup. Having high cholesterol is the most common reason. When the arteries become narrowed, the blood flow is restricted and, as the heart demands more oxygen (usually during times of increased physical activity or stress) there is not enough "supply" to meet "demand". This condition is known as ischemia (pronounced is-KEY-me-yah). Ischemia often presents itself with the classic heart attack symptoms:<ol><li type="1">A pressure-like discomfort directly behind the breastbone (sternum)</li><li type="1">Pain radiating to the neck, jaw, or left arm</li><li type="1">Sweating</li><li type="1">Shortness of breath</li><li type="1">Nausea</li></ol><p>Any or all of these symptoms may be present when the heart becomes ischemic. Many patients present their doctors with vague, generalized complaints and a thorough evaluation reveals that they have had ongoing, "silent" heart attacks. Fortunately, myocardial ischemia does <i>not</i> mean permanent heart damage. The muscle can recover if it is not deprived of oxygen for very long. However, if the blood flow remains inadequate to meet the oxygen demand, the muscle will be permanently damaged. This is known as a myocardial infarction or MI. In the acute setting, this event can be caused by a small blood clot that will travel down a diseased artery and "plug up" the narrowed portion. At this point, all of the muscle "downstream" from this blockage is deprived of oxygen and it will eventually infarct. <p>This muscle damage has a broader effect than just the mechanical function of a portion of the heart. Like any "pump," the heart requires an electrical source to help it perform properly. There is an intricate set of electrical pathways within the muscle itself (the conduction system) that helps regulate the coordinated rhythm required for maximum performance of the muscle. When a portion of the heart muscle is damaged, or even just severely ischemic, this conduction system can be affected and a change of the heart rhythm can occur. The most serious of these rhythms is ventricular fibrillation and is fatal if not corrected immediately. In this rhythm, the heart has lost all semblance of pumping action and the muscle is merely "quivering". Since there is no ejection of blood from the heart to the body, there is no pulse and the vital organs are deprived of oxygen. This is the classic scenario of sudden death. The treatment for this fatal rhythm is to deliver an electrical shock to the heart using a defibrillator. Anyone who has watched more than one episode of <i>ER</i> has surely seen these "paddles" being applied to a patient's chest with the sensational, more-dramatic-than-real-life "jump" of the patient when the shock is given. This electrical jolt momentarily stuns the entire heart muscle and gives it the opportunity to regain a coordinated rhythm.<p><b>Defibrillator Controversy</b> Portable defibrillators have been around for many years and have been proven as an effective treatment for cardiac arrest. They have been so successful, in fact, that the American Heart Association has changed the initial steps for dealing with an adult cardiac arrest. Twenty-five years ago when a person was found unconscious, the initial CPR steps were: <ol><li type="1">Establish unresponsiveness</li><li type="1">Give mouth-to-mouth resuscitation</li> <li type="1">Perform one minute of chest compressions</li> <li type="1">Call for help</li> </ol>The importance of early defibrillation has been acknowledged by the medical community and the sequence of steps has changed. Now the recommended steps should be to establish unresponsiveness, <i>call for help</i>, and then proceed with resuscitation efforts. This has gained even more significance with the advent of the automatic external defibrillator (AED). This device can be attached to the patient and activated by someone with minimal training. The device will automatically evaluate the heart rhythm and deliver the appropriate shock and then continue to monitor the rhythm for any further intervention. The device even gives voice commands to the rescuers. AEDs are currently found in a wide variety of settings from industrial complexes to high-rise office buildings to commercial and corporate aircraft.<p><table cellpadding="0" cellspacing="0" border="0" align="right"><tr><td width="8"></td><td valign="top" align="left" width="222"><img src="http://www.sailnet.com/images/content/authors/mahaffy/050400wm_cardiac3.jpg" width="222" height="177"><br><div align="left"><font color="#318e5a" size="-1"><b>Defibrillators have become smaller and easier to use than ever, though the final decision to have one aboard is subject to a variety of factors.</b></font></div></td></tr><tr><td height="8" colspan="2"> </td></tr></table>In the January 2000 edition of <i>Ocean Navigator</i> magazine, a company called US Search and Rescue made the claim that using an AED would increase the chances of surviving sudden cardiac death to "more than 90 percent," and that this device is recommended for all vessels venturing offshore. The following month, a letter to the editor from a board-certified cardiologist pointed out the recent statistics from a large, multi-center study indicating that there was only a 50 percent survival rate (at one month) of those patients who were immediately defibrillated after an "observed arrest." Clearly there is a discrepancy of opinion here, and I will offer my own personal thoughts on the matter.<p>The AED has, without question, offered measurable benefit to those people suffering out-of-hospital cardiac arrest. By making this technology more readily available to the lay public, many victims have survived the initial cardiac arrest and have gone on to receive the necessary definitive treatment. It is crucial to remember that defibrillation is not the only required treatment for a cardiac arrest. The ability to use this "countershock" device early in the event only allows the patient more time to reach definitive therapy. The true increase in the survivability statistics is due, in large part, to the ability of paramedics to begin medication therapy and stabilize the patient until more definitive techniques and drugs can be administered. Unless the early defibrillation is coupled with these other treatments, the likelihood of a successful outcome is certainly far less than the quoted 90 percent survival rate. In the marine environment, these adjunct therapies are a long way off and I personally do not see the cost-benefit analysis favoring the purchase of the AED technology for the majority of voyaging sailors<p>On the other hand, I would advocate the use of the AED technology in a number of nautical areas, specifically the charter and commercial segments. A charter captain has no control over the health status of their clients and there may not even be a disclosure of a heart condition in the pre-charter agreement. As in the commercial segment, the operators of a for-hire venture have an increased responsibility to their clientele to provide top quality service in all aspects of the charter and this includes medical care. The important distinction here is that these vessels must carry, in addition to an AED, the necessary fluids and medications to manage a cardiac problem and, of utmost importance, the crew must be properly trained to deal with a wide range of medical problems. I am not talking about the limited training required to obtain a USCG license, but rather a far more comprehensive program offering experience in a broad range of illnesses and injuries. In this setting, an AED would be an integral piece of medical equipment and will hopefully become a standard for the commercial maritime industry.<p><b>Treatment</b> Even without the advanced and expensive technology, there are a number of simple, effective steps you can take on board to manage a suspected heart problem. As I have repeated ad nauseum, the first step is to go with the basics—the ABCs. If the crew member clutches his or her chest and collapses, there is not much you can do but attend to the Airway, Breathing, and Circulation. After that, an immediate call for help and course deviation to the nearest available assistance will be about the extent of your capabilities. If, on the other hand, the patient complains of any combination of symptoms that lead you to suspect a heart problem, the first step is to have the person rest. Inactivity will lessen the heart's demand for oxygen and may alleviate all of the symptoms. <p>The next step would be to give them one or two "baby" aspirin. These are 81mg tablets which are usually chewable. Regular aspirin is fine, but it takes much longer to be absorbed in the setting when minutes may be important. I would recommend carrying "baby" aspirin for just this purpose. The aspirin has the effect of a blood "thinner" by inhibiting the function of platelets. While this does not dissolve a blood clot in a coronary artery, aspirin will make the blood cells more "slippery" and improve blood flow.<p>Another useful medication is nitroglycerine. These small tablets are placed under the tongue until they dissolve. The action of this drug (a nitrate) is to relax and dilate the blood vessels. When the coronary arteries dilate, more blood can flow past the narrowing and supply blood to the myocardium. This dilation is not isolated to the coronary arteries and the response to this blood-vessel dilation is a lowering of the blood pressure. This may be beneficial, since the lower pressure will mean the heart has less work to do to pump blood to the body. However, the blood pressure should not be allowed to go so low that it will reduce blood flow to the vital organs. Therefore, I recommend that you check the patient's blood pressure after a nitro tablet has been given. Assuming an adequate blood pressure, these tablets can be given every few minutes to alleviate the chest pain. Many patients with known CAD will carry their own nitro pills and will know when to take them. Nitroglycerine also comes in a spray (like a breath spray), but this is far less common. One other common side effect of nitroglycerine is a profound headache. Medical personnel often look at this complaint as a reliable sign that the nitro was fresh and should work effectively. Nitro tablets are not considered standard medications for most medical kits and I submit that they should be. The drug is relatively inexpensive, has a reasonably long shelf life when stored properly, and can be a lifesaver when administered appropriately. Also, given the incidence of CAD in the general population, you may well find yourself at a marina or a boatyard where a cardiac emergency may occur. Your preparedness may be the key to a fellow sailor's survival.<p>Finally, one last drug can be used to aid the suspected heart attack patient—oxygen. By delivering a higher concentration of oxygen to the bloodstream, the myocardium may be able to get by with the diminished flow through the coronaries. Unfortunately, the oxygen tank and the required regulator are rather expensive to buy and are difficult to store on board a small vessel. It is important to remember that, although an episode of chest pain has been relieved, this does not mean there is no further risk of heart damage. If you suspect that someone on board is experiencing heart problems, make the call and head for help. The most common killer in cardiac cases is denial, and your commitment to the safety of the crew supersedes any objections from the patient.<p>Hopefully, this is a condition with which you will never have to deal in the marine environment, but if it should occur, you can be prepared with the right equipment and training to handle the situation.<p><table cellpadding="0" cellspacing="0" border="0" align="center"><tr><td colspan="2" height="8"> </td></tr><tr><td valign="middle" align="left" ><a href="http://www.sailnet.com/store/item.cfm?pid=658&step=4"><img src="http://www.sailnet.com/images/content/authors/mahaffy/050400_adbutton.gif" width="320" height="75" border="0"></a></td></tr></table></p></HTML>
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