McKenna's Pharmacology for Nursing, 2e

684

P A R T 8  Drugs acting on the cardiovascular system

causing feelings of nausea and abdominal pain; swollen legs and feet; and dependent oedema in the coccyx or other dependent areas, with decreased peripheral pulses and hypoxia of those tissues. In addition, with left-sided failure, oedema of the lungs reflected in engorged vessels and increased hydrostatic pressure throughout the cardiovascular system is also seen (Figure 44.3). Left-sided heart failure Left-sided HF reflects engorgement of the pulmonary veins, which eventually leads to difficulty in breathing. The person complains of tachypnoea (rapid, shallow res­ pirations), dyspnoea (discomfort with breathing, often accompanied by a panicked feeling of being unable to breathe), and orthopnoea (increased difficulty breath­ ing when lying down). Orthopnoea occurs in the supine position when the pattern of blood flow changes because of the effects of gravity, which increases pressure and perfusion in the lungs. Orthopnoea is usually relieved when the person sits up, thereby reducing the blood flow through the lungs. The degree of HF is often calcu­ lated by the number of pillows required to get relief (e.g. one-pillow, two-pillow, or three-pillow orthopnoea).

The person with left-sided HF may also experience coughing and haemoptysis (coughing up of blood). Rales may be present, signalling the presence of fluid in the lung tissue. In severe cases, the person may develop pul­ monary oedema; this can be life-threatening because, as the spaces in the lungs fill up with fluid, there is no place Right-sided HF usually occurs as a result of chronic obstructive pulmonary disease (COPD) or other lung diseases that elevate the pulmonary pressure. It often results when the right side of the heart, normally a very low-pressure system, must generate more and more force to move the blood into the lungs. It also commonly occurs with ageing, when the venous system fails to deliver blood to the heart effectively and the hydrostatic pressure in the venous end of the capillary increases, leading to a loss of fluid in the tissues and changes in the overall efficiency of the vascular system. In right-sided HF, venous return to the heart is decreased because of the increased pressure in the right side of the heart. This causes congestion and a backup of blood in the systemic system. Jugular venous pressure (JVP) rises and can be seen in distended neck veins, reflecting increased central venous pressure (CVP). The liver enlarges and becomes congested with blood, which leads initially to pain and tenderness and eventually to liver dysfunction and jaundice. Dependent (lower) areas develop oedema or swelling of the tissues as fluid leaves the congested blood vessels and pools in the tissues. Pitting oedema in the legs is a common finding, reflecting fluid pooling in the tissues. For example, when the person with right-sided HF changes position and the legs are no longer dependent, the fluid moves back into circulation to be returned to the heart. This increase in cardiovascular volume increases blood flow to the kidneys, causing increased urine output. This is often seen as nocturia (excessive voiding during the night) in a person who is up and around during the day and supine at night. The person may need to get up during the night to eliminate all of the urine that has been produced as a result of the fluid shift. Treatments Several different approaches are used to treat HF. This chapter focuses on the cardiotonic drugs (also called inotropic drugs) that work to directly increase the force of cardiac muscle contraction. Other drug therapies used to treat HF include the following: • Vasodilators, such as angiotensin-converting- enzyme (ACE) inhibitors and nitrates, decrease cardiac workload, relax vascular smooth muscle to decrease afterload and allow pooling in the veins, for gas exchange to occur. Right-sided heart failure

Right-sided HF

Left-sided HF

elevated jugular venous pressure

anxiety

tachypnoea dyspnoea orthopnoea haemoptysis rales

splenomegaly

hepatomegaly

cardiomegaly S 3 increased heart rate

decreased renal perfusion when upright

GI upset nausea abdominal pain

increased renal perfusion when supine nocturia

pitting oedema

decreased peripheral pulses hypoxia

weakness/fatigue

FIGURE 44.3  Signs and symptoms of heart failure (HF).