SUPPOSE YOU'RE CARING for two patients who've just had coronary artery bypass graft (CABG) surgery. One underwent surgery while on a cardiopulmonary bypass (CPB) machine; the other had surgery without CPB. In this article, I'll explain how differences in the two techniques affect the postoperative nursing care you provide for each patient.
Operating while the patient is on the CPB machine (also called on-pump surgery) allows the surgeon to work on a motionless heart. While the heart is still, the CPB machine oxygenates the patient's blood and maintains circulation.
To use the CPB machine, the surgeon performs a median sternotomy, cross-clamps the aorta, and attaches the patient to the pump. He then arrests the heart's action with a cardioplegic solution, usually a potassium-rich solution delivered cold (39.4° F [4° C]) to protect the heart from ischemia.
After bypass grafting, the blood in the CPB machine is gradually warmed and pumped back into the patient's body. Internal paddles are used to shock the heart to restart it. Pacing wires are placed in the epicardium, and chest tubes are inserted.
Performed on a beating heart, off-pump surgery is becoming increasingly popular because it avoids the complications associated with CPB, such as platelet dysfunction, perfusion deficits to major organs, and cognitive complications. Off-pump surgery may be especially appropriate for elderly patients, who are at higher risk for CPB-related complications such as stroke. The procedure isn't recommended for patients with small coronary arteries or diffuse cardiac disease.
The surgeon usually performs a sternal incision. Before partial cross-clamping of the descending aorta, the patient's arterial blood pressure (BP) is reduced to below 80 mm Hg either with nitroglycerin or mechanically. The surgeon uses stabilizers to hold a section of the beating heart still during surgery. The rest of the heart continues to work, supplying blood to the body.
Common aspects of postoperative care
The following aspects of postoperative care apply to all patients who've had CABG surgery.
- Maintain airway patency. Monitor the patient's pulmonary status closely and report any changes, such as pulmonary congestion, dyspnea, or SpO2 below 92%. Follow the weaning protocol per orders.
- Monitor vital signs and record intake and output hourly. Note the urine's color, clarity, and specific gravity. Notify the surgeon of any signs of decreased renal perfusion.
- Assess the patient's hemodynamic and cardiac status. Atrial fibrillation (AF) is a common complication of cardiac surgery, although it's rarely life-threatening. Treat persistent AF with medication or synchronized cardioversion as ordered.
- Perform peripheral and neurovascular assessments hourly for the first 8 hours. Then, if the patient is stable, perform these checks every 2 hours for the next 8 hours and every 4 hours for the following 8 hours.
- Monitor his neurologic status and notify the surgeon and anesthesia provider if he hasn't awakened within 8 hours after surgery. Elderly patients and those with liver or kidney problems, history of stroke, or perfusion deficits during surgery may need more time to recover from anesthesia.
- Gradually rewarm the patient with warmed blankets, but avoid temperature-regulating blankets or devices. Warming him too rapidly can cause vasodilation and a rapid drop in BP, possibly leading to hemodynamic compromise.
- Titrate drugs to optimize cardiac function and BP. Notify the surgeon of changes in cardiovascular status as reflected by electrocardiogram (ECG) and hemodynamic monitoring.
- Monitor chest tube drainage (generally serosanguineous) and report drainage of over 100 ml/hour.
- Watch for signs of bleeding by checking the patient's hemoglobin and hematocrit levels at least every 4 hours. Administer blood if ordered.
- Monitor the patient's electrolytes and report abnormal values. Provide replacement electrolyte therapy as indicated.
- Manage the patient's pain. Morphine, the drug of choice, may be given by patient-controlled analgesia pump.
- Assess the incision and monitor for wound infection and abnormal bleeding.
Complications following on-pump surgery
Now let's look at some of the complications you should watch for if your patient had on-pump surgery:
- systemic inflammatory response syndrome, possibly triggered by damage to red blood cells and platelets from contact with the pump surfaces. Signs and symptoms include hypothermia or fever, tachycardia, and hyperventilation.
- coagulopathies caused by the destruction of platelets and the large amounts of heparin administered during CPB. Because this can lead to hemorrhage, the patient may need blood transfusions.
- perfusion insult to the brain, kidneys, liver, and lungs, which can lead to complications such as cognitive changes, embolic stroke, and renal insufficiency. Perfusion insults are related to surgical manipulation of the heart and cross-clamping of the aorta, which can lead to clots and emboli.
- heparin-induced thrombocytopenia, a serious complication of heparin use during on-pump surgery. Anticoagulation during surgery helps prevent thromboembolic complications, but excessive bleeding can lead to thrombocytopenia. Researchers are investigating the use of Iloprost (a form of prostacyclin), a platelet aggregation inhibitor, to prevent bleeding and thrombosis in patients undergoing cardiac surgery.
- edema, including pulmonary edema. This complication may result from lowered oncotic pressure, release of vasoactive substances, and other complications of artificial circulation.
- electrolyte imbalances from excess sodium and water retention. Administer diuretics, potassium replacement, and fluids as ordered.
As a rule, patients who've undergone off-pump surgery have fewer perfusion problems affecting the brain, lungs, and kidneys. Compared with patients who've had on-pump surgery, they typically recover faster, require fewer blood transfusions, spend less time on mechanical ventilation, and have fewer problems with edema or volume overload. However, they're still susceptible to the following potential complications:
- acute occlusion or graft failure. The development of newer cardiac stabilizers means that precise anastomosis is possible even with lateral and posterior bypass grafts. However, the technical difficulties of beating-heart surgery mean graft failure is a bigger risk following off-pump surgery. Signs and symptoms include chest pain and ST-segment elevation. The surgeon may order an angiogram a few days postoperatively to assess graft patency.
- postpericardiotomy syndrome, which can lead to life-threatening cardiac tamponade. This complication is more common in patients who've had off-pump surgery because of the use of cardiac stabilizers. Signs and symptoms include a pericardial friction rub, fever, pleuritic chest pain, pleural effusions, and eosinophilia. Watch for ECG changes, including ectopy, bradycardia, and signs of cardiac tamponade (including alternating QRS amplitudes and ventricular tachycardia). Patients are treated with a nonsteroidal anti-inflammatory drug (NSAID) such as indomethacin; patients with renal failure or aspirin allergy can take milder NSAIDs such as naproxen or ibuprofen.
A patient who underwent off-pump CABG surgery is likely to be discharged from the hospital earlier than someone who had on-pump surgery. Plan to spend additional time teaching him and his family how to monitor his recovery at home, including what signs and symptoms to report and when to follow up with his surgeon.
Two paths to good outcomes
By understanding the differences in on- and off-pump CABG surgery, and how the differences affect postoperative nursing care, you can help your patient recover uneventfully no matter which type of surgery he had.
Joan Marie Hyett is coordinator of the Valor program at South Texas Veterans Health Care System (Audie L. Murphy Memorial Veterans Hospital) and an adjunct clinical faculty member at the University of Texas Health Sciences Center–San Antonio School of Nursing, both in San Antonio, Tex.
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