Circulation, also known as perfusion, is the body’s method of delivering oxygen-rich blood and nutrients to tissues and organs while simultaneously removing waste products. This process is necessary for maintaining the health and function of every cell. When circulation is compromised, tissues do not receive the necessary oxygen, a condition called ischemia, which can lead to significant health consequences. Assessing this fluid delivery system is a fundamental step in monitoring overall health and identifying potential problems early.
Assessing Peripheral Blood Flow
Peripheral blood flow refers to the circulation in the extremities, such as the hands and feet, and can be checked using simple, non-invasive methods. The Capillary Refill Time (CRT) test measures how quickly blood returns to the tiny vessels beneath the skin. To perform this test, firmly press on a fingertip or nail bed for about five seconds until the area turns white or “blanches.”
Upon releasing the pressure, the color should return almost immediately as blood refills the capillaries. A normal CRT is two seconds or less in healthy adults. A time longer than two seconds suggests delayed peripheral perfusion, which may indicate issues like dehydration or poor blood flow to the extremities.
The appearance and temperature of the skin offer clues about peripheral circulation. Healthy skin should be warm and have a consistent color. Poor circulation often causes the skin to feel noticeably cool to the touch.
Changes in skin color, such as paleness (pallor) or a bluish-gray tinge (cyanosis), indicate that tissues are not receiving enough oxygenated blood. A lack of blood flow can also slow the delivery of nutrients necessary for tissue repair, resulting in dry skin or sores on the lower extremities that are unusually slow to heal.
Evaluating Central Circulatory Function
Evaluating the central circulatory system involves assessing the performance of the heart, the body’s central pump, primarily by checking the pulse. The pulse is the palpable pressure wave created as the heart ejects blood into the arteries. The most common and accessible sites for checking this wave are the radial artery at the wrist and the carotid artery in the neck, found next to the windpipe.
When assessing the pulse, it is important to feel for more than just the rate. The rhythm should be regular, meaning the beats are evenly spaced, and any persistent irregularity should be noted. The strength, or force, of the pulse reflects the volume of blood being pumped and the pressure in the arteries.
A pulse can be described as strong or “bounding” if it feels very forceful, or weak and “thready” if it is faint and easily compressed. A diminished or weak pulse suggests decreased cardiac output or low blood volume. Peripheral pulses, such as the posterior tibial pulse near the ankle bone or the dorsalis pedis pulse on the top of the foot, are also useful for assessing blood flow farthest from the heart.
Recognizing Signs of Systemic Perfusion Failure
When circulation fails to meet the body’s overall oxygen demands, systemic perfusion failure, or shock, can result. This condition triggers the body’s compensatory mechanisms, which prioritize blood flow to vital organs like the heart and brain. Recognizing these signs indicates that vital organs are struggling to function.
One of the clearest indications of poor systemic perfusion is a change in mental status. The brain is sensitive to a lack of oxygen, so inadequate blood flow can cause symptoms like confusion, disorientation, dizziness, or lethargy. These changes reflect cerebral hypoperfusion, meaning the brain is not receiving sufficient blood supply.
The body’s attempt to compensate for low blood volume or pressure often leads to other changes. A rapid heart rate (tachycardia) is a common sign as the heart tries to pump faster to move available blood. Breathing may also become rapid and shallow (tachypnea) as the body attempts to increase oxygen intake to compensate for poor oxygen delivery to tissues.
A significant sign of systemic failure involves the kidneys, which are sensitive to changes in blood flow. When perfusion drops, the kidneys reduce their function to conserve fluid, leading to a decrease in urine output. A sustained urine output below 30 milliliters per hour suggests renal hypoperfusion and is a serious indicator of circulatory compromise that requires immediate medical attention.