Vol. 4 Issue 20
AMI in the CCU
Persistent monitoring post-AMI is critical to patient recovery
Mr. G, a 58-year-old widower, walks into the ED at 6:30 p.m. accompanied by his daughter. He is complaining of chest pain that began shortly after he woke up in the morning. He went to his job as a maintenance man at a local college despite his discomfort. His pain remained at 4-5 on the 10-point pain scale all day. He began feeling weak shortly after noon and left work.
Upon questioning, he admits to feeling weak and having some bilateral arm pain prior to bedtime the previous night. He denies any cardiac history. His past history does include migraine headaches, gastroesophageal reflux disease and high cholesterol. He smokes a pack of cigarettes a day.
ED staff members perform a 12 lead ECG that shows acute ST elevation in leads 1 and V1-5 consistent with an acute myocardial infarction (AMI). ACLS chest pain protocols are followed. His monitor shows normal sinus rhythm with a rate generally in the 60s, but his rate drops as low as 44 at times. His initial blood pressure was 140/70, and his lungs are clear.
Three heparin locks are started and labs are drawn, including complete blood count, electrolytes, creatine phosphokinase (CPK), troponin, prothrombin time (PT), activated partial thromboplastin time (APTT), international normalization ratio (INR) and troponin I. Oxygen is started at 3L. Mr. G is given 325 mg of aspirin. Sub.lingual nitroglycerin is administered without effect, so intraven.ous nitroglycerin is started. Mr. G also is given a morphine sulfate IV to alleviate his anxiety as well as his pain.
After a cardiology consultation, it's decided that, although it has been about 12 hours from the onset of pain, thrombolytics should be administered since the ST segments are so acutely elevated. Twelve hours is the maximum time limit recommended by the American Heart Association for thrombolytic administration. A retevase 10 mg IV is administered at 7 p.m. and 7:30 p.m. This decreased Mr. G's pain to 2 on the pain scale and also decreased the ST elevations, but not to baseline.
Mr. G is placed on a weight-based IV heparin protocol. He is not given any beta-blocker due to the drops in his heart rate. He is now ready for transfer to the critical care unit (CCU).
An RN in the CCU caring for a patient in Mr. G's condition must keep him hemodynamically stable while continuing to treat any pain and anxiety. The goal is to minimize myocardial oxygen demands. The patient must be monitored closely for any AMI extension, reocclusion or complications.
In CCU, Mr. G's heart rhythm is continuously monitored. The nurse chooses leads V2 and I as her primary leads since his ECG changes were most acute there prior to the thrombolytic therapy. If any new elevations occur, the nurse does a 12-lead ECG to evaluate the whole heart and notifies the physician. New elevations might necessitate further thrombolytic administration or other reperfusion measures such as angioplasty or coronary artery bypass graft.
Post-AMI dysrhythmias usually occur in the first 72 hours. Some are related to reperfusion and may be self-terminating, requiring no treatment. Others may be life-threatening. Mr. G has had an anterior lateral MI, so his nurse knows that his left ventricular function can be compromised by any rhythm change.
Mobitz II block, a second-degree heart block, often occurs after anterior MI and may require treatment with atropine or temporary pacing. Mobitz II can progress to a third-degree heart block, which in the light of an anterior MI is an indicator of a poor prognosis and in itself requires pacemaker insertion, regardless of the patient's vital signs.
Atrial fibrillation is common after MI. Treatment depends on how hemodynamically stable the patient is and can range from prescription of amiodarone (Cordarone®, Wyeth-Ayerst Pharmaceuticals) to DC cardioversion, which is an electrical shock delivered at a specific time in the cardiac cycle to convert the rhythm to normal sinus. Any pulseless rhythm requires immediate ACLS treatment.
Vital signs and assessments are initially done every 2 hours in pain-free patients. The target heart rate is usually in the 60s; heart rate should not fall below 50. Systolic blood pressure should be kept ³ 90. Automatic blood pressure cuffs should be used judiciously after thrombolytics since excessive inflation pressures can cause subcutaneous bleeding and hematomas. Temperature elevations may occur due to the body's inflammatory response to cellular injury. An elevated temperature may also be an indicator of pericarditis, a potential complication.
Cardiovascular assessment should include evaluation of heart sounds and pulses. Mr. G's nurse listens at the aortic, pulmonic and tricuspid areas of the chest. New murmurs may indicate structural damage after AMI. An S3 is an early indicator of left ventricular failure. An S4 indicates diastolic dysfunction and can occur during ischemia. A pericardial friction rub is associated with pericarditis. If a nurse is unsure of what she is hearing, she should report any ausculatory changes to the physician.
Peripheral pulses are assessed for presence, equality and volume. Weak, thready pulses indi.cate shock. Nurses also assess jugular veins. Jugular vein distension indicates right-sided heart failure.
Respiratory status is an important part of patient assessment. Nurses note respiratory rate and any dyspnea. In some patients, dyspnea can be an anginal equivalent. It is also associated with heart failure. Lung sounds are assessed. Crackles indicate pulmonary edema. Expiratory wheezes not responsive to bronchodilators can be associated with the paroxysmal nocturnal dyspnea of left ventricular failure. Oxygen satura.tion is also assessed, and oxygen is delivered to maintain a SaO2 ³ 93 percent. Chest X-rays are done to evaluate any respiratory symptoms.
Neurological assessment is crucial in thrombolytic patients like Mr. G since intracranial bleed.ing is a major risk. The Glasgow Coma Scale is the basis of the evaluation. Also, any headache should be carefully evaluated. Nitrate headaches are typically frontal in nature. A head.ache associated with even seemingly minor neurological changes should be reported immediately.
Mr. G's nurse monitors all his lab work and reports abnormals to the physician. Attention is paid to his hemoglobin/hematocrit, PT, APTT, INR and platelets to detect and prevent bleeding. CPK and troponin I are monitored to assess effectiveness of therapy. Electrolytes are checked and replaced as needed to help prevent rhythm disturbances.
GI and Renal Function
Nausea and vomiting are frequently associated with pain in ischemic heart disease. They can also be side effects of medications such as nitrates and morphine. Antiemetics should be administered. Mr. G's nurse tests any emesis or stools for blood since bleeding can occur with thrombolytic/anticoagulant therapy. For gastrointestinal protection, Mr. G will continue taking Prevacid® (lansoprazole, TAP Pharma.ceu.ticals) after going home. Also a stool softener should be ordered to prevent constipation and straining of stools with possible vasovagal effects.
Mr. G's urine output is measured as part of maintaining an accurate intake and output. Renal function is a good indicator of cardiac output and tissue perfusion. Mr. G is able to void into a urinal, thus avoiding a Foley catheter and potential bleeding complications. His nurse checks his urine for blood every shift.
Skin assessment is a key part of Mr. G's care. His nurse takes note of his skin color and temperature. Cyanosis is a sign of decreased oxygen perfusion in the tissues. Cool, moist skin indicates poor perfusion and shock.
Edema can follow right-sided heart failure or poor renal function following left heart failure. Hematomas can occur at puncture sites. Care is taken to preserve Mr. G's IV lines since venipuncture should be avoided for 24 hours after retevase administration. Labs should be drawn off existing lines. Also, the nurse evaluates Mr. G's skin for any signs of allergic reactions to his medications.
Pain and Patient Comfort
Mr. G is instructed to notify his nurse of any chest, arm, neck or epigastric discomfort, as well as any dyspnea. Cardiac pain can occur in any of these areas. The nurse also inquires about pain at each assessment, noting location, quality, and precipitating and alleviating factors.
The 1-10 pain scale is used to assess the severity of any pain. Cardiac pain is treated with SL and IV nitrates, morphine and oxygen. A 12-lead ECG is done with any occurrence of pain.
While in the CCU, Mr. G is kept on bed rest with commode privileges. His nurse monitors his heart rate, blood pressure, respiratory rate (RR) and SaO2 response to activity. He is given a low-sodium, low-cholesterol diet as tolerated.
On arrival to the CCU, Mr. G continues to have 2/10 chest discomfort. His blood pressure is 112/74 and he has a heart rate of 68. His lungs are clear and he has a RR of 18 with a SaO2 of 96 percent on 3L. A 12-lead ECG was unchanged from one in the ED done after the second dose of retevase. He is given SL nitroglycerine and his IV nitroglycerine is increased with a decrease in pain to 1/10. He then receives 3 mg of morphine IV with pain relief.
Mr. G later has a 16-beat run of ventricular tachycardia. He remains asymptomatic during this run. His ECG also shows an intermittent right bundle branch block (RBBB). RBBB is often found post-AMI in patients like Mr. G who have ST elevation in lead V2, which is indicative of septal damage.
The next morning Mr. G remains pain-free. His 12-lead ECG shows that his MI is evolving, but he has no new ST changes. His heart rate is 74, blood pressure 126/78, RR 22, and he has some crackles in his bases. He is given a Lasix® (furosemide, Aventis Pharmaceuticals) 20 mg IV and started on Lopressor® (metoprolol tartrate, Novartis Pharmaceuticals). His nurse monitors his intake and output, and breath sounds to assess his response to the Lasix. Later that day his IV nitroglycerine is weaned off. An echocardiogram is done, showing some left ventricular wall motion abnormalities. His ejection fraction is 40 percent.
Referral for Care
Mr. G is able to have a cardiac catheterization the next morning. The results are 95 percent occlusion of his left anterior descending artery, multiple 70 percent occlusions of his circumflex artery and 50 percent occlusion of his right coronary artery. He is referred to a tertiary care facility for further care.
Throughout his hospitalization Mr. G's nurses gave both Mr. G and his daughter concise explanations of his care. They repeated these explanations as needed because they understand that in stressful situations people don't absorb new knowledge easily. Mr. G was also given a cardiac education folder to help him learn about his disease, as well as information on the hospital's cardiac rehabilitation program.
American Heart Association. Introduction to the International Guidelines 2000 for CPR and ECC: A consensus on science. (2000). Circulation, 102(Suppl. I), I1-I11.
Fallon, E.M., & Roques, J. (1997). Acute chest pain. AACN Clinical Issues, 8(3), 383-397.
Hand, H. (2001) Myocardial infarction: Part 1. Nursing Standard, 15(36), 45-53.
Hand, H. (2001) Myocardial infarction: Part 2. Nursing Standard, 15(37), 45-53.
Kinney, M.R., et al. (1998). AACN's clinical reference for critical care nursing. St. Louis: Mosby.
Litton, K.A. (2002, May). Left vs. right ventricular MI: Which is it? RN, 5, 36ac5-36ac8, 36ac10, 36ac12.
Martha A. Smith is a clinical resource nurse at Salem (MA) Hospital's ICU.