The medical condition of decreased or low cardiac output is the result of many different causes and is exhibited in the form of various symptoms. Decreased cardiac output related to hypertension, aging and many other causes is discussed in the article. Cardiac output decreases with slowing down of heart beats. Another reason behind low cardiac output is the inability of heart muscles to pump blood in a proper manner; many a time, a damaged heart muscle is responsible for this condition. The following write-up discusses the pathophysiology, causes and the treatment or care plan for this medical condition.
What is Cardiac Output?
It is the amount of blood pumped by the heart (ventricle) in a single minute. The unit that is used for measuring cardiac output is cubic dm/min. The average rate of cardiac output for men and women is 5 cubic dm/min. and 4.5 cubic dm/min. respectively. This medical condition is described as the reduction in outflow of blood from ventricles of the heart. There could be a variety of reasons behind the condition of low cardiac output; details of the causes are given below.
The common causes behind this medical condition are hypertension, myocardial infarction, congenital heart disease, valvular heart disease, cardiac arrhythmias, pulmonary disease, cardiomyopathy, fluid overload, drug effects, electrolyte imbalance and decreased fluid volume. Geriatric patients are at a high risk of suffering from decrease cardiac output due to the reduced compliance of ventricles that results from aging.
The symptoms of this medical condition include arrhythmias, electrocardiogram changes, variations in hemodynamic parameters, tachypnea, orthopnea, dyspnea, frothy sputum, abnormal arterial blood gases, edema, weight gain, decreased urine output, dizziness, syncope, restlessness, anxiety, fatigue, weakness, cold clammy skin, decreased peripheral pulses, change in mental status, confusion, pulsus alternans, angina, etc. Decreased cardiac output and blood pressure are interrelated since the decrease in cardiac output results into low blood pressure.
The medications recommended for decreased cardiac output depend on the etiological factors. However, common medications used in the treatment include diuretics, digitalis therapy, vasodilator therapy, ACE inhibitors, antidysrhythmics and inotropic agents. Maintaining the optimum fluid balance is also a part of treatment. Administration of the prescribed fluids helps increase the extracellular fluid volume thereby, raising the cardiac output. It is also important to maintain the hemodynamic parameters. Patients with increased preload need to restrict sodium and fluids, which helps in decreasing the extracellular fluid volume. Maintaining perfusion and ventilation is also an important part of the treatment. Placing the patient in a high-Fowler position helps in reducing the ventricular filling and preload. The patient should be placed in the supine position to promote diuresis and to increase vanous return. Restricting the physical activities of patients helps in reducing the oxygen demands of the body. A quiet and peaceful environment must be provided to patients, since emotional stress may lead to increased cardiac demands. Stool softeners should be given to patients because if the body gets strained owing to bowel movements, there arises a possibility of further decrease in cardiac output. The decreased or low cardiac output interventions or nursing interventions include hemodynamic regulation and cardiac care. Decreased cardiac output RT (Respiratory Therapy) is useful from the point of increasing fluid volume and reducing bilateral ankle edema & clammy skin.
Factors Affecting Cardiac Output
The volume of blood leaving the heart i.e. cardiac output is dependent on the volume entering it. In the condition of decreased or low cardiac output, volume of blood entering the heart is less than usual. The ventricle from which blood is released doesn't contract in a forceful manner and therefore, the cardiac output is low. Thus, the output depends on the degree to which muscles of ventricles are stretched by the incoming blood flow.
Negative inotropic effect is one of the factors responsible for low cardiac output. Alteration in the contraction of muscles and especially the heart muscles caused by intake of certain medications is termed as inotropic effect. Medications that have a negative inotropic effect are responsible for weakening the force of heart required to contract its muscles; it is therefore, responsible for low cardiac output. The positive inotropic medications are recommended for conditions like myocardial infarction.
The medical condition of decreased cardiac output is a result of a variety of health problems. Therefore, the treatment measures must be devised on the basis of specific cause. Some of the common treatment measures listed in the article should be helpful for readers.