Dictionary

hypovolemia Abnormal decrease in the volume of blood plasma. Hypovolemia occurs with dehydration or bleeding.

hypoventilation The state in which a reduced amount of air enters the alveoli in the lungs, resulting in decreased levels of oxygen and increased levels of carbon dioxide in the blood. Hypoventilation can be due to breathing that is too shallow (hypopnea) or too slow (bradypnea), or to diminished lung function. The opposite of hypoventilation…

hypotonic solution A solution that contains fewer dissolved particles (such as salt and other electrolytes) than is found in normal cells and blood. Hypotonic solutions are commonly used to give fluids intravenously to hospitalized patients in order to treat or avoid dehydration.

hypotonia Decreased muscle tone and strength that results in floppiness. Hypotonia is a common finding with cerebral palsy and other neuromuscular disorders. Untreated hypotonia can lead to hip dislocation and other problems. Treatment is via physical therapy. In some cases, braces may be needed to permit a full range of movement in patients with hypotonia.

hypothyroidism, infantile Underactivity of the thyroid gland that starts after birth in infancy or early childhood, as manifested by delays in growth and development, and by myxedema (a dry, waxy type of swelling, often including swollen lips and nose). Treatment involves use of thyroid hormone medication. Also known as Brissaud infantilism and infantile myxedema.

hypothyroidism, congenital See cretinism.

hypothyroid Deficiency of thyroid hormone. The hypothyroid state (hypothyroidism) is characterized by fatigue, weight gain, and constipation. Severe, longstanding hypothyroidism can lead to swelling of the extremities, coma, and death.

hypothermia Abnormally low body temperature. Someone who falls asleep in a cold temperature may become hypothermic, and the condition can be fatal. Hypothermia is intentionally produced to slow the metabolism during some types of surgery. Severe hypothermia can be fatal. Those with mild or moderate hypothermia (are alert and conscious, and have not lost the…

hypothalamus The area of the brain that secretes substances that influence pituitary and other gland function and is involved in the control of body temperature, hunger, thirst, and other processes that regulate body equilibrium.

hypotension, postural See hypotension, orthostatic.

hypotension, orthostatic A temporary lowering of blood pressure, usually related to suddenly standing up. Healthy people may experience orthostatic hypotension if they rise quickly from a seated position, especially after a meal. Orthostatic hypotension occurs most commonly in older people. The change in position causes a temporary reduction in blood flow and therefore a shortage…

hypotension Blood pressure that is below the normal expected for an individual in a given environment. Blood pressure normally varies greatly with activity, age, medications, and underlying medical conditions. Hypotension can result from conditions of the nervous system, conditions that do not begin in the nervous system, and drugs. Neurological conditions that can lead to…