Care And Treatment Of The Chest Pain Patient

     Paramedics save lives, the saying goes, and EMTs save paramedics. That's glib and debatable, but it's certainly true that the role of the EMT-Basic is a vital one, and that there's relatively little out there in the way of information and tools to help him do it better. This new column, which will appear several times a year, is a resource for EMT-Basics. It will cover everything from reviews of basic skills to assisting ALS providers with more advanced interventions in a way designed to enhance understanding and develop a more complete provider. As always, we welcome your comments; send thoughts, feedback and ideas for future columns to nancy.perry@cygnusb2b.com.

Scenario
     At approximately 1530 hours, Rescue 24 responds to a person complaining of chest pain. Upon arrival, the crew performs an initial assessment. It reveals a patient in moderate distress, diaphoretic and with cool skin, but alert, oriented and cooperative. The patient, an overweight 64-year-old male, informs the crew that he was watching television when he began to experience epigastric discomfort and became nauseous.

     The crew completes a head-to-toe assessment, obtains vital signs (BP 88/50, pulse 94, respiratory rate 18), administers 100% oxygen via a non-rebreather mask, applies an ECG monitor and performs a 12-lead ECG, attaches an SaO2 monitor, assesses blood glucose (125 mg/dL) and initiates two intravenous lines of normal saline. They administer a 500cc fluid bolus and note improvement in the patient's blood pressure to 142/86 mmHg. The crew then administers 0.4 mg of sublingual nitroglycerin, which further reduces the blood pressure to 134/78 and completely relieves the chest discomfort.

     Upon arrival at the emergency department, the patient experiences a generalized seizure and goes into cardiac arrest-the ECG monitor displays ventricular fibrillation. The crew begins CPR with bag-valve mask ventilations and applies a defibrillator. The patient is shocked using 200 joules of energy. The crew then reassesses and notes a pulse rate of 70 and a blood pressure of 110/78. The patient is given 100 mg of lidocaine (an anti-arrhythmic medication) and a maintenance infusion at 2 mg/min. The patient also begins breathing on his own at a rate of 18 breaths per minute. Shortly thereafter, he awakes and can speak with the ED physician.

Keeping It Basic
     The above scenario was pretty straightforward, but let's discuss some of the tools and medications the crew employed.

     First, this patient presented with epigastric discomfort. This is sometimes misdiagnosed as some form of indigestion, especially because of its location right below the xiphoid process. The patient was pale, diaphoretic and overweight. There may be many medical conditions that present similarly, so it is important to rule out some of the most emergent conditions and treat the signs and symptoms.

     As the crew identified that the patient was hypotensive, they began to work on raising his blood pressure. The crew opted to administer a 500cc IV fluid bolus. An IV fluid bolus is when a certain amount of fluid is administered into the circulatory system. This is done to hydrate the patient and/or attempt to restore adequate circulatory volume, thereby increasing blood pressure. In addition, the extra fluid may cause the heart muscle to stretch and contract more forcefully. The fluid administered may be normal saline, lactated Ringer's, D5W (dextrose in water) or blood products. The downside of administering normal saline or a non-blood product is that these don't carry oxygen. The most common range for prehospital fluid boluses is between 250-500 cc.

     Once the blood pressure was stable (>100 mmHg systolic), the crew began to treat the chest pain with nitroglycerin. Nitroglycerin is a medication that dilates the blood vessels; it works rapidly when administered sublingually (under the tongue). This is why it is critical to assess the patient's blood pressure before and after administering the medication: If the patient is already hypotensive and receives nitroglycerin, it may drop the blood pressure further. This will be extremely detrimental to the patient.

     Why administer nitroglycerin? The patient suffering cardiac-related chest pain is most likely experiencing angina or myocardial infarction. The pain is due to a lack of perfusion (circulation) to the heart tissue. The coronary arteries are the arteries responsible for feeding the heart tissue with oxygenated blood. If one, two or all of the arteries become blocked or partially blocked, blood can't reach the target myocardial tissue. The lack of oxygen to the tissue results in chest discomfort. Nitroglycerin dilates these arteries with the intention of allowing more blood to travel through the partially blocked vessel(s) and deliver oxygenated blood to the myocardial tissue.

     Here, the patient's chest pain did subside; however, upon arrival at the emergency department, the patient went into cardiac arrest. Ventricular fibrillation is uncoordinated muscle contraction of the ventricles; the heart consequently fails to pump blood into the vital organs, resulting in cardiac arrest. The treatment for managing a VF patient will depend on whether the arrest is witnessed or unwitnessed. If the event is witnessed and a defibrillator (AED) is available, then defibrillation must be considered. However, if the event is unwitnessed, then five cycles, or two minutes, of CPR should be considered prior to defibrillation, if the victim has been pulseless for more than 4-5 minutes.

     Lidocaine is a medication used to treat ventricular arrhythmias. Prehospital care providers will use ventricular anti-arrhythmic agents, such as lidocaine, when attempting to suppress ventricular irritability. A maintenance infusion is used after an IV bolus of lidocaine is administered and pulses have been restored. The goal is to ensure that therapeutic drug levels are maintained and help prevent recurrence of the ventricular irritability.

     As we can see, the patient's presentation can change without warning. Therefore, it is critical to continuously assess your patients and try to anticipate the next treatment modality. As a basic provider, this can only be accomplished by working closely with advanced providers and becoming familiar with the ALS equipment within your service.

Glossary
12-lead ECG-An electrocardiogram that provides a view of 12 different areas of the heart. This is helpful when searching for signs of ischemia (lack of oxygen), muscle injury or necrosis (tissue death).

Arrhythmias-Abnormal heart rhythms.

Diaphoretic-Sweating profusely.

Epigastric-Related to the epigastrium, the region of the abdominal wall between the xiphoid process and umbilicus.

Lidocaine-A medication used to suppress ventricular irritability.

Maintenance infusion-Used to maintain therapeutic blood levels of a specific medication.

Nitroglycerin-A medication that dilates blood vessels and is used to treat certain cardiac emergencies.

SaO₂-The percentage of all red blood cell oxygen-carrying sites saturated with oxygen.

Ventricular fibrillation-A cardiac arrhythmia that results in uncoordinated ventricular contraction leading to cardiac arrest.

Orlando J. Dominguez, Jr., MBA, FF/EMT-P, is chief of EMS and public information officer for Brevard County Fire Rescue in Rockledge, FL.