Complications: Initial Postoperative Period

Advances in surgical techniques and anesthetic agents allow many patients to recover quickly and move from the intensive care unit (ICU) in shorter periods of time. However, many patients still experience complications of surgery and require intensive nursing care in the initial post-op period. Patients presenting for surgery are increasingly older with more risk factors and underlying comorbid conditions, which increases the risk of complications after surgery. Patients who experience complications often have a longer ICU and hospital stay and may have a higher risk of death than patients who do not experience surgical complications. Nurses must be extra vigilant to observe for and treat potential complications as early as possible.

Objectives

In this chapter, you will learn:

1. Prevention and treatment of common post-op cardiac surgery complications

2. Assessment, laboratory, and x-ray findings that may signal potential complications

CARDIAC COMPLICATIONS

Cardiac output (CO) is determined by several factors. Decreased preload and decreased contractility (myocardial depression) are the two most common causes of low CO after cardiac surgery. Bleeding, increased urinary output, increased capillary permeability (causing fluid to be lost into the tissues), decreased ventricular compliance (lower ventricular filling volumes), or cardiac tamponade may cause a decrease in preload. Decreased contractility may be caused by myocardial depression, myocardial stunning, acidosis, hypoxemia, or by the inflammatory response produced because of surgery.

Low Cardiac Output

The most common cause of mortality after surgery is a low CO state (Jacobson, Marzlin, & Webner, 2007). It can be difficult to manage low CO after surgery, as there are so many potential causes. Recognizing the factors that lead to a decrease in CO and taking action to improve CO after surgery are critical nursing functions during this initial period.

Prevention

Once the patient is in the ICU, prevention may not be possible. It is critical that a decrease in CO be recognized early and treated promptly.

Assessment

Signs and symptoms of impaired CO include altered mental status, hypotension, decreased mean arterial pressure (MAP), tachycardia, decreased pulses, lengthened capillary refill time, narrow pulse pressure, cool extremities, and oliguria or anuria.

Diagnostics

If available, a pulmonary artery catheter or continuous CO device may be used to estimate CO. If CO is not adequate, a mixed venous oxygen saturation (SvO₂) will be lower than normal (less than 70%). SvO₂ is the percentage of hemoglobin saturated with oxygen found in blood returning to the heart (right atrium or pulmonary artery).

A low reading indicates hypoperfusion or an increased metabolic rate. If CO is not adequate, metabolic acidosis and an increase in serum lactic acid will also be found.

Intervention

Inadequate CO may be caused by inadequate preload, elevated afterload, alterations in heart rate or rhythm, myocardial depression (poor contractility), or a combination of these factors. The first factor to be addressed when CO is low is preload. Fluid resuscitation with crystalloids and colloids should be continued until there is evidence of adequate intravascular volume. This would be demonstrated by a central venous pressure (CVP) or right atrial pressure of 8 mmHg and a pulmonary artery occlusion pressure (PAOP) of 15 mmHg. If preload is adequate and CO remains poor, afterload should be examined and optimized. A number of intravenous medications may be administered as per physician order to decrease afterload and improve CO. Heart rate and rhythm are critical for maintaining CO. If the patient experiences a dysrhythmia, bradyarrhythmia, or tachyarrhythmia, heart rate and rhythm should be returned to normal. If all other parameters have been optimized and CO remains inadequate, an inotropic medication may be ordered by a physician to improve CO. (See Chapter 9 for a more detailed description of optimizing hemodynamics, including medications used to improve CO.)

NURSING IMPLICATIONS: The cardiac surgery nurse plays an important role in recognizing low CO states and intervening based on physician orders. After surgery, patients typically have orders for various vasoactive, inotropic, and antiarrhythmic medications. These need to be administered according to the surgeon’s orders and the hospital and unit policy to maintain CO. Cardiac surgery nurses must have an intimate knowledge of how these medications work and when to administer or titrate each one. The new cardiac surgery nurse should work with experienced nurses until these skills are learned. (See Chapter 9 for tips on administering various medications to maintain CO.)

FAST FACTS in a NUTSHELL

Decreased CO is a major problem in the immediate postop period. Maintaining adequate CO is one of the primary nursing goals during this period and reduces other complications and organ failure.

Myocardial Ischemia and Infarction

Myocardial ischemia and infarction may occur after cardiac surgery for a number of reasons. Risk factors include older age, multiple comorbidities, large extent of coronary artery disease, decreased left ventricular function, redo surgery, long cardiopulmonary bypass time, and bypass surgery combined with another cardiac surgical procedure, such as valve surgery.

Myocardial ischemia may occur due to incomplete revascularization, poor myocardial protection during surgery, coronary vasospasm, or embolism. Myocardial infarction (MI) may be due to thrombosis (clot formation in a coronary artery or graft) or acute closure of a bypass graft. The incidence of MI after coronary artery bypass surgery is between 1% and 5% (Coventry, 2014).

Prevention

Patients should be started on aspirin (or clopidogrel if aspirin is not tolerated) prior to or within 6 hours after surgery for prevention of saphenous vein graft closure and thrombosis leading to MI (Hillis et al., 2011).

Assessment

Frequently, there are no abnormal assessment findings. Diagnosis is made based on 12-lead electrocardiogram (ECG) and laboratory findings. In the setting of vasospasm, there may be a sudden decrease in CO. (See the section on vasospasm for more information.)

Diagnostics

A 12-lead ECG frequently reveals ST-segment elevation in a specific coronary artery distribution, new Q waves, new bundle branch block, complete heart block, or ventricular dysrhythmias. If ST-segment elevation is seen in every lead, this may be caused by pericarditis, which is common after cardiac surgery and does not indicate an MI.

Cardiac markers are elevated in the presence of MI. However, elevations in cardiac markers due to surgical injury to the heart must be taken into account. As a general rule, a creatine kinase–myocardial band (CK-MB) level that is 10 times the upper limit of normal or a troponin level greater than 15 to 20 mcg/dL indicates an MI.

Intervention

Patients who experience post-op myocardial ischemia or MI often follow the same post-op course as other patients. Physician orders may include administration of nitroglycerin and beta-blockers if blood pressure will support the administration of these medications. Inotropes should be used sparingly if at all, as they increase myocardial oxygen demand. If an intervention is needed to improve CO, an intraaortic balloon pump may be used to assist the pumping ability of the heart and improve coronary artery blood flow.

If acute graft closure is suspected as the cause of MI, emergency coronary angiography with percutaneous coronary intervention may be indicated. (See Chapter 1 for a description of percutaneous coronary intervention.) Surgical reexploration may also be required.

NURSING IMPLICATIONS: Coronary vasospasm and myocardial injury or infarction may initially present in the same way. Administration of nitroglycerin, as ordered by the physician, is appropriate treatment for both. It can be difficult to tell if the patient is experiencing vasospasm or ischemia from another cause. However, with the administration of a vasodilator, coronary vasospasm should be relieved quickly and cardiac enzymes should not be elevated above what is normal after cardiac surgery. (See the next section for more information on vasospasm.)

FAST FACTS in a NUTSHELL

The goal when treating myocardial ischemia or infarction after cardiac surgery is to minimize damage to the myocardium and maintain adequate CO.

Coronary Vasospasm

Vasospasm is a potential cause of sudden cardiovascular collapse in the early post-op period and is often unrecognized. Spasm may occur in saphenous vein grafts, internal mammary or radial artery grafts, or in native coronary arteries. The cause of spasm in these vessels is unclear. Vasospasm is more likely to occur in radial artery grafts.

Prevention

Steps are taken in the operating room to prevent spasm. As grafts are prepared for implantation, manipulation is kept to a minimum. Prior to implantation, radial artery grafts are typically soaked in a solution designed to prevent vasospasm. Patients are often sent out of the operating room on infusions of medications that help to prevent spasm, such as nitroglycerin (Tridil) or diltiazem (Cardizem), especially when radial artery grafts are used.

Assessment

CLINICAL ALERT! Vasospasm of coronary arteries or grafts typically presents as sudden hypotension with decreased CO.

Diagnostics

A 12-lead ECG demonstrates ST-segment elevation in multiple leads.

Intervention

Coronary vasospasm often resolves without intervention. If these patients become hemodynamically unstable, supportive care should be instituted. Administration of vasodilators such as calcium channel blockers or nitroglycerin, as per physician’s orders, may help to resolve vasospasm.

NURSING IMPLICATIONS: Patients with radial artery grafts should be on a medication to prevent graft spasm. If a patient decompensates suddenly, a 12-lead ECG should be performed to evaluate for ischemia.

FAST FACTS in a NUTSHELL

Coronary vasospasm may cause sudden hypotension and cardiovascular collapse. It may resolve spontaneously or require administration of nitroglycerin or calcium channel blockers.

Cardiac Tamponade

The pericardial sac is entered during surgery and is usually not sewn back up. This creates a communication between the pericardial space and the mediastinum. If blood accumulates in the mediastinum, this may lead to cardiac tamponade. Cardiac tamponade is an accumulation of blood to the point where pressure is placed on the heart (Figure 10.1). This pressure constricts the thin-walled atria and reduces the amount of blood that fills the ventricles (reduces preload). This may cause a sudden and profound drop in CO.

Several things may lead to cardiac tamponade in the early post-op period. The most common is clotting of mediastinal chest tubes, which causes blood to accumulate and leads to the development of cardiac tamponade. Also, an anastamosis (point where graft is sewn into a coronary artery) may not be fully sealed or may fail suddenly, causing a rapid accumulation of blood in the mediastinum. Early cardiac tamponade typically occurs during the first 12 hours post-op.

Prevention

Maintaining patency of mediastinal chest tubes is important to prevent cardiac tamponade.

Assessment

Cardiac tamponade may be difficult to recognize in the early post-op period. Hypotension, tachycardia, and elevated filling pressures are seen, but are common in most cardiac surgery patients during this period. A high index of suspicion for cardiac tamponade assists in early recognition.

FIGURE 10.1 Cardiac tamponade.

CLINICAL ALERT! Key clinical signs and symptoms include a sudden drop in output from mediastinal chest tubes, dyspnea, hypotension, tachycardia, low CO, narrowing pulse pressure, increased CVP, altered mental status, diaphoresis, anxiety, and restlessness.

Diagnostics

Chest x-ray may reveal cardiac or mediastinal enlargement. A 12-lead ECG may indicate low voltage or electrical alternans. If cardiac tamponade is suspected, a bedside echocardiogram should be obtained as soon as possible, as this is the best way to diagnose cardiac tamponade.

Intervention

Cardiac tamponade in the immediate post-op period necessitates immediate surgical reexploration to determine the source of bleeding and evacuate accumulated blood. If cardiac arrest is imminent, emergency resternotomy may be performed. This typically involves the surgeon and operating room personnel opening the chest at the bedside. The ICU nurse should be prepared to assist with setting up a sterile field and gathering a specialized instrument tray for the surgical team.

NURSING IMPLICATIONS: It is important to keep chest tubes draining after cardiac surgery. Chest tubes may be gently milked if needed to keep them draining, but should not be stripped. Stripping chest tubes produces very high negative pressure in the chest cavity. If cardiac tamponade is suspected, the physician should be notified immediately so treatment can begin.