Porth's Essentials of Pathophysiology, 4e

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Heart Failure and Circulatory Shock

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are used to document ejection fraction, ventricular pre- load, and regional wall motion. Invasive hemodynamic monitoring may be used for assessment in acute, life-threatening episodes of heart failure. 37 These monitoring methods include cen- tral venous pressure (CVP), pulmonary artery pres- sure monitoring, measurements of cardiac output, and intra-arterial measurements of blood pressure. Central venous pressure reflects the amount of blood return- ing to the right side of the heart. Measurements of CVP are best obtained by a catheter inserted into the right atrium through a peripheral vein or by the right atrial port (opening) in a pulmonary artery catheter. Ventricular volume pressures are obtained indirectly, such as by means of a flow-directed, balloon-tipped pulmonary artery catheter. This catheter is introduced through a peripheral or central vein and then advanced into the right atrium. The balloon is then inflated with air, enabling the catheter to float through the right ventricle into the pulmonary artery until it becomes wedged in a small pulmonary vessel. With the balloon inflated, the catheter monitors pulmonary capillary pressures (i.e., pulmonary capillary wedge pressure or pulmonary artery occlusion pressure ), which reflect pressures from the left ventricle. The pulmonary capil- lary pressures provide a means of assessing the pump- ing ability of the left ventricle. One type of pulmonary artery catheter is equipped with a thermistor probe to obtain thermodilution measurements of cardiac output. Catheters with oximeters built into their tips that permit continuous monitoring of oxygen satu- ration (SvO 2 ) also are available. Intra-arterial blood pressure monitoring provides a means for continuous monitoring of blood pressure. It is used in persons with acute heart failure who need continuous blood pres- sure monitoring, such as when aggressive intravenous medication therapy or a mechanical assist device is required. Treatment The goals of treatment for heart failure are determined by the rapidity of onset and severity of the heart fail- ure. Persons with acute heart failure require urgent therapy directed at stabilizing and correcting the cause of the cardiac dysfunction. For persons with chronic heart failure, the goals of treatment are directed toward relieving the symptoms, improving the quality of life, and treating or reducing or eliminating risk fac- tors (hypertension, diabetes, or obesity) with the long- term goal of slowing, halting, or reversing the cardiac dysfunction. 1,2 Treatment measures for both acute and chronic heart failure include pharmacologic and nonpharmacologic approaches. Mechanical support devices, including the aortic balloon pump (for short-term acute failure) and ventricular assist devices (VADs), can be used to sustain life in persons with severe heart failure. Heart transplant or a VAD remains an option for some people with end- stage heart disease.

It is important to note that current guideline-directed therapies only target HF patients with a reduced ejection fraction. Therapies specific to patients with a preserved ejection fraction or HFpEF have not been established. Nonpharmacologic Methods Exercise intolerance is typical of persons with chronic heart failure. Consequently, individualized exercise training is important to maximize muscle condition- ing. Persons who are not accustomed to exercise and those with more severe heart failure are started at a lower intensity and shorter duration than those who are largely asymptomatic. Sodium and fluid restriction and weight management are important for all persons with heart failure, with the level of sodium and fluid restric- tion individualized to the severity of sodium intake, and diuretic therapy facilitates the excretion of edema fluid. Counseling, health teaching, and ongoing evaluation programs assist persons with heart failure to self-manage and cope with their treatment regimen. 38 PharmacologicTreatment Once heart failure becomes moderate to severe, poly- pharmacy becomes a management standard. First line therapies for patients with a reduced ejection fraction include β -adrenergic inhibitors, angiotensin-converting enzyme (ACE)/angiotensin receptor inhibitors, and diuretics. But for patients who are intolerant to these drugs or who remain symptomatic despite guideline- directed therapies, additional agents may be used, such as aldosterone antagonists or digoxin. 1,2,39 The choice of pharmacologic agents is determined by problems caused by the disorder (i.e., systolic or diastolic dys- function), those brought about by activation of com- pensatory mechanisms (e.g., excess fluid retention, inappropriate activation of sympathetic mechanisms), and the person’s comorbidities. 40 Diuretics are among the most frequently prescribed medications for symp- toms of volume overload. 13 They promote the excre- tion of fluid and help to sustain cardiac output and tissue perfusion by reducing preload and allowing the heart to operate at a more optimal part of the Frank- Starling curve. In emergencies, such as acute pulmonary edema, loop diuretics such as furosemide (Lasix) can be administered intravenously. When given intravenously, these medications act quickly to reduce venous return through vasodilation so that right ventricular output and pulmonary vascular resistance are decreased. This response to intravenous administration is extrarenal and precedes the onset of diuresis. The ACE inhibitors, which prevent the conversion of angiotensin I to angiotensin II, have been used effectively in the treatment of chronic heart failure. 40 The renin- angiotensin-aldosterone system is activated early in the course of heart failure and plays an important role in its progression. It results in an increase in angiotensin II, which causes vasoconstriction, unregulated ventricular remodeling, and increased aldosterone production with a subsequent increase in sodium and water retention by