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Emergency coronary artery bypass grafting

An overview

MacLeod, Carrie E., PhD, APRN-BC

doi: 10.1097/01.CCN.0000554831.89961.bc
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Abstract: This article reviews coronary artery bypass grafting preoperative preparation, operative procedure, and postoperative care. A patient case study frames this article's discussion of clinician action, patient healthcare options, and nursing considerations. Preoperative patient education, postoperative complications, and interventions are reviewed.

Framed around a patient case study, this article reviews the preoperative, operative, and postoperative aspects of nursing care surrounding emergency coronary artery bypass grafting. Patient education, postoperative complications, and interventions are discussed.

Carrie E. MacLeod is an assistant professor at Saint Anselm College, Department of Nursing, Manchester, N.H.

The author has disclosed no financial relationships related to this article.

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Figure

Mrs. J, a 55-year-old woman with type 2 diabetes mellitus (T2DM) and dyslipidemia, presented to the ED with diaphoresis, dyspnea, and jaw and upper back pressure. The woman's coworkers called 911 after her symptoms persisted for 1 hour. The 12-lead ECG transmitted to the ED from the emergency medical services team confirmed ST segment elevation in Leads I, AVL, V3-V6 with reciprocal ST depression in Leads II, III, aVF consistent with ST elevation myocardial infarction (STEMI). On the patient's arrival to the ED, clinicians initiated the STEMI algorithm and immediately transported the patient to the cardiac catheterization lab. Coronary angiography revealed a totally occluded proximal left anterior descending (LAD) artery and high-grade (80%) stenosis of the proximal circumflex artery. Left ventriculography revealed an ejection fraction (EF) of 35% (normal, 50%-75%) and anterior wall motion abnormality.1Balloon angioplasty was performed and a drug-eluting stent was placed in the LAD. Ongoing ischemia and hemodynamic instability require the placement of an intra-aortic balloon pump (IABP). The cardiac surgery team was consulted for emergency coronary artery bypass grafting (CABG).

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Background

The American Heart Association (AHA) and the American College of Cardiology (ACC) guidelines provide evidence-based, goal-directed medical and surgical strategies for emergency coronary revascularization.2 (See Normal anatomy of the coronary arteries.) Healthcare providers must determine the most appropriate interventions to optimize myocardial salvage and quality of life. Initial management of the patient with a STEMI is beyond the scope of this article but is included in the AHA and ACC STEMI algorithm.2

The Society of Thoracic Surgeons provides a summary of patient demographics associated with CABG procedures. Increasingly, these patients have diabetes (49%), nonelective status (63%), and have previously undergone PCI (31%). CABG procedures are performed on-pump (87%) and off-pump (13%). The decision to perform an on-pump versus off-pump CABG depends on multiple variables, including location of coronary stenosis, patient condition, surgeon preference and training, and the medical center. Fewer patients are receiving greater than three-vessel grafts, most likely because of the increased use of staged CABG and PCI.3 Last, the use of the radial artery as a graft has declined over the past decade. This is because of the increased frequency of transradial catheterizations that cause structural and functional changes in the artery that may persist for up to 12 months.4

Because critical care nurses need to act swiftly when patients require emergency CABG, this article reviews CABG preoperative preparation and patient education, outlines the operative procedure, and addresses postoperative patient complications and nursing interventions.

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Revascularization strategies

Several criteria are used to determine the severity of coronary artery disease (CAD), including:5

  • thrombolysis in myocardial infarction (TIMI) flow—the degree of perfusion in the infarct-related artery
  • fractional flow reserve (FFR)—the ratio between the maximum achievable blood flow in a diseased coronary artery and the theoretical maximum flow in a normal coronary artery. An FFR of 1.0 is considered normal and lower than 0.75 to 0.80 is associated with myocardial ischemia.6
  • synergy between percutaneous coronary intervention with taxus and cardiac surgery (SYNTAX) score II–predicts mortality risk for PCI versus CABG in patients with multivessal coronary disease.

Since 2011, the AHA/ACC has defined significant stenosis as angiographic evidence of at least 70% diameter narrowing of a coronary artery and at least 50% for the left main coronary artery.7 The patient in this case study required urgent PCI to the LAD culprit lesion. Immediate surgical revascularization on the nonculprit lesions was required because of ongoing ischemia.8

Hemodynamic instability may occur in 5% to 10% of patients with acute myocardial infarction after PCI and is associated with early mortality of 40% to 50%.9 Research indicates that CABG is associated with lower mortality risk than PCI in most patients with diabetes mellitus and complex multivessel disease.10,11 This patient is best served with a staged PCI/CABG intervention.12 For recommendations for emergency CABG for patients with STEMI, see the 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction at www.ahajournals.org/doi/full/10.1161/CIR.0b013e3182742cf6.5

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Preoperative preparation

The need for emergency CABG may limit the preoperative workup. Mrs. J was transported to the OR with the IABP in place to reduce perioperative mortality.13 Transesophageal echocardiography was done after anesthesia induction and endotracheal intubation for evidence of ventricular systolic/diastolic dysfunction and pulmonary hypertension, which could place her at increased risk for postoperative complications.14

Standard preoperative lab work includes a type and crossmatch for packed red blood cells, platelets, and fresh-frozen plasma; complete blood cell count; complete metabolic profile; PT/INR/PTT; urinalysis; and ABG. Patients with T2DM have an increased risk of death or major cardiovascular event at hemoglobin A1C levels above 8.1%.15 Significant carotid artery disease is a direct cause of cerebral ischemia during cardiopulmonary bypass and may result in postoperative neurologic dysfunction, but time constraints may prohibit carotid ultrasonography.16

Medications. Preoperative medications such as antibiotics and anxiolytics should be prescribed, and contraindicated medications, as noted below, should be discontinued in a timely manner.

  • prophylactic antibiotics: preoperative dosing and 24 hours postoperative administration of weight-based cefazolin or vancomycin. Regimens extended for longer durations may place a patient at risk for increased antibiotic resistance and other major infections.17
  • antiplatelet therapy: aspirin should be continued. Antiplatelet activity decreases postoperative myocardial infarction, improves oxygenation, reduces rates of acute bypass graft occlusion, and increases survival rates.18 P2Y12 inhibitors or glycoprotein IIb/IIIa inhibitors should be discontinued immediately to reduce the risk of bleeding and increased blood product use.19
  • anticoagulants: unfractionated heparin, low-molecular-weight heparin, or bivalirudin should be discontinued 6 to 24 hours before CABG.20
  • beta-blockade: beta-blockers reduce the risk of postoperative atrial fibrillation. Continuation of beta-blocker medications is suggested in the perioperative setting for patients, unless contraindicated. Preoperative use of beta-blockers in patients with diabetes is associated with improved cardiovascular survival after CABG.21
  • statins: statins are associated with improved postoperative outcomes through reduction of the systemic inflammatory response associated with CABG, the risk of postoperative inflammation-induced atrial fibrillation, and perioperative mortality.22
  • anxiolytics: oral benzodiazepines are often used to ensure that the patient is in a relaxed state when entering the OR.

Preoperative education is an important factor for successful postoperative recovery. However, research indicates that this information is best relayed during a time of low anxiety, and prior to her CABG procedure may not be the best time to discuss postoperative expectations with this patient.23 (See Preoperative education for the patient undergoing CABG.)

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Operative procedure

CABG surgery may take 2 to 5 hours, depending on the number of grafts, conduit harvest, and patient stability. For an on-pump CABG, cannulas are placed in the right atrium and the aorta, and the patient is placed on cardiopulmonary bypass (CPB), which is a mechanical means of oxygenation, carbon dioxide removal, and blood circulation. The heart is stopped with cold cardioplegia.24 Preferred conduits for grafts include the left internal mammary artery (LIMA), radial artery (RA), and the greater saphenous vein.25 For this patient, the LIMA was dissected distally and placed to the diagonal, and an RA will be placed to the circumflex. When anastomoses are completed, the patient is removed from CPB. Epicardial pacing wires are placed on both the atrium and the ventricle and brought through the skin just below the xiphoid process. Mediastinal chest tubes are placed—pleural chest tubes are placed if either pleural cavity is entered during the procedure. The sternum is closed with surgical steel wires followed by tissue and skin closure. Extubation appropriateness is determined by the patient's hemodynamic status, anesthetic techniques, and cardiopulmonary stability.26

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Postoperative care

Effective postoperative care begins with a structured report from the OR team to the ICU team.27 The ICU nurse is responsible for the close monitoring of the patient's postoperative hemodynamic stability, return to normothermia, dysrhythmias, respiratory status, fluid and electrolyte balance, bleeding (incisional/chest tube drainage), coagulopathies, organ perfusion insult, infection, and blood glucose control.24-27 The potential causes of these postsurgical complications are listed below:

  • hemodynamic instability: cardiac function is decreased secondary to myocardial edema and ischemia-reperfusion injury.28
  • dysrhythmias: atrioventricular blocks and bradycardia occur because of myocardial edema. Atrial and ventricular ectopy occur with electrolytes imbalances and inflammation. Atrial fibrillation continues to affect over 30% of patients undergoing CABG.3
  • alterations in respiratory status: anesthesia, thoracic manipulation, alteration of rib cage mechanics, and CPB decrease in pulmonary function.29
  • fluid and electrolyte imbalance: initial intravascular fluid depletion followed by fluid shifts resulting from lowered oncotic pressure, release of vasoactive substances, and other complications of CPB. Electrolyte imbalances occur because of sodium and water retention.
  • bleeding (incisional and chest tube drainage): caused by coagulopathies or surgical issues.
  • coagulopathies: caused by hypothermia, destruction of platelets, and the large amounts of heparin administered during CPB or preoperative anticoagulants or antiplatelets. Heparin administration may also produce heparin-induced thrombocytopenia.28
  • organ perfusion insult: related to surgical manipulation of the heart and cross-clamping of the aorta, which can lead to thrombus formation and embolism as well as low flow state while on CPB.28
  • hyperglycemia: acute physiologic stress and preoperative factors such as older age, lower EF, higher BMI, and emergency surgery produce higher postoperative glucose levels. Hyperglycemia is directly correlated to increased postoperative infections.30,31
  • infection: immunosuppression from acute physiologic stress, hyperglycemia, and steroids during CPB.28
  • pain: incisional, sternal stabilization, chest tube insertion sites, and discomfort related to immobility during the operative procedure.

The ICU nurse's ability to detect subtle changes in the patient post-CABG is essential to a successful surgical recovery and prevention of postoperative complications. (See Potential early postoperative CABG complications.)

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Conclusion

The staged intervention for this patient was successful. The IABP was removed on the operative night, and she was extubated on postoperative day 1. Per AHA/ACC recommendations, she was discharged home on aspirin, P2Y12 inhibitor for the LAD stent, beta-blocker, statin, and an angiotensin-converting enzyme inhibitor as well as her preoperative diabetes medication. Discharge information included advice on medications, wound care, daily weights, cardiac rehabilitation, continuum of care, physical activity, and restrictions including no lifting anything greater than 10 lb and no driving for 1 month after surgery. The patient should have a clear understanding to call her healthcare provider for temperatures higher than 100°F (37.8°C), chest pain or palpitations, new wound drainage, or a weight gain of more than 5 lb in 2 days. Research indicates this information is crucial to maintaining adherence to post-CABG recommendations, especially with women and individuals who have had previous coronary interventions.32

Isolated or staged multiarterial coronary revascularization continues to represent the most effective therapy for multivessel CAD.12 Additionally, multivessel disease treated with CABG rather than PCI results in reduced mortality and reintervention-free survival.11 ICU nurse preparedness and familiarity with post-CABG complications can have a profound impact on achieving optimal patient outcomes.

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Normal anatomy of the coronary arteries

A, aortic valve; CB, conus branch of the right coronary artery; diagonals, first and second diagonal branches of the left anterior descending coronary artery; LAD, anterior descending branch of left coronary artery; LCX, circumflex branch of the left coronary artery; LMCA, left main coronary artery; M1/M2, first and second marginal branches of the right coronary artery; OM1/OM2, first and second obtuse marginal branches of the left coronary artery; P, pulmonic valve; RCA, right coronary artery.

Figure

Figure

Source: Allen HD, Shaddy RE, Penny DJ, Feltes TF, Cetta F. Moss & Adams' Heart Disease in Infants, Children, and Adolescents, Including the Fetus and Young Adult. 9th ed. Philadelphia, PA: Wolters Kluwer; 2016.

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Preoperative education for the patient undergoing CABG

The critical care nurse should address the following:

  • sights and sounds of perioperative environment
  • insertion of monitoring lines
  • preoperative medications and anticipated sensations
  • use of incentive spirometer
  • length of surgery
  • expectations related to the postoperative environment
  • postoperative pain management
  • endotracheal tube: time of intubation and anticipated time of extubation, communication issues
  • postoperative activity
  • preparation of the significant other

Adapted from: Martin CG, Turkelson SL. Nursing care of the patient undergoing coronary artery bypass grafting. J Cardiovasc Nurs. 2006;21(2):109-117. Used with permission.

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Potential early postoperative CABG complications3,28-31

  • decreased myocardial function
  • dysrhythmias
  • respiratory distress
  • fluid and electrolyte imbalances
  • bleeding
  • decreased organ perfusion
  • hyperglycemia
  • infection
  • pain
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Keywords:

coronary artery bypass grafting (CABG); coronary artery disease (CAD); emergency revascularization; left anterior descending (LAD) coronary artery; percutaneous coronary intervention (PCI); stenosis; surgery

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