hypoxia


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Related to hypoxia: hypoxemia, hyperoxia

hypoxia

 [hi-pok´se-ah]
diminished availability of oxygen to the body tissues; its causes are many and varied and includes a deficiency of oxygen in the atmosphere, as in altitude sickness; pulmonary disorders that interfere with adequate ventilation of the lungs; anemia or circulatory deficiencies, leading to inadequate transport and delivery of oxygen to the tissues; and finally, edema or other abnormal conditions of the tissues themselves that impair the exchange of oxygen and carbon dioxide between capillaries and tissues. adj., adj hypox´ic.  

Signs and symptoms vary according to the cause. Generally they include dyspnea, rapid pulse, syncope, and mental disturbances such as delirium or euphoria. cyanosis is not always present and in some cases is not evident until the hypoxia is far advanced. The localized pain of angina pectoris due to hypoxia occurs because of impaired oxygenation of the myocardium. Discoloration of the skin and eventual ulceration that sometimes accompany varicose veins are a result of hypoxia of the involved tissues.

The treatment of hypoxia depends on the primary cause but usually includes administration of oxygen by inhalation (see oxygen therapy). In some vascular diseases, administration of vasodilators may help increase circulation, hence oxygen supply, to the tissues.
affinity hypoxia hypoxia resulting from failure of the hemoglobin to release oxygen to the tissues, as may occur with a left-shifted oxyhemoglobin dissociation curve.
anemic hypoxia hypoxia due to reduction of the oxygen-carrying capacity of the blood as a result of a decrease in the total hemoglobin or an alteration of the hemoglobin constituents.
circulatory hypoxia stagnant hypoxia.
histotoxic hypoxia that due to impaired utilization of oxygen by tissues, as in cyanide poisoning.
hypoxemic hypoxia (hypoxic hypoxia) that due to insufficient oxygen reaching the blood, as at the decreased barometric pressures of high altitudes.
stagnant hypoxia that due to failure to transport sufficient oxygen because of inadequate blood flow, as in heart failure.

hy·pox·i·a

(hī-pok'sē-ă),
Decrease below normal levels of oxygen in inspired gases, arterial blood, or tissue, without reaching anoxia.
[hypo- + oxygen]

hypoxia

/hy·pox·ia/ (hi-pok´se-ah) reduction of oxygen supply to a tissue below physiological levels despite adequate perfusion of the tissue by blood.hypox´ic
anemic hypoxia  that due to reduction of the oxygen-carrying capacity of the blood owing to decreased total hemoglobin or altered hemoglobin constituents.
histotoxic hypoxia  that due to impaired use of oxygen by tissues.
hypoxic hypoxia  that due to insufficient oxygen reaching the blood.
stagnant hypoxia  that due to failure to transport sufficient oxygen because of inadequate blood flow.

hypoxia

(hī-pŏk′sē-ə, hĭ-)
n.
1. Deficiency in the amount of oxygen reaching body tissues.
2. Depletion of dissolved oxygen in aquatic environments to levels that are detrimental or fatal to aerobic organisms, often caused by eutrophication.

hy·pox′ic adj.

hypoxia

[hīpok′sē·ə]
Etymology: Gk, hypo + oxys, sharp, genein, to produce
inadequate oxygen tension at the cellular level, characterized by tachycardia, hypertension, peripheral vasoconstriction, dizziness, and mental confusion. Mild hypoxia stimulates peripheral chemoreceptors to increase heart and respiration rates. The central mechanisms that regulate breathing fail in severe hypoxia, leading to irregular respiration, Cheyne-Stokes respiration, apnea, and respiratory and cardiac failure. Increased sensitivity to the depressant effect of opiates on the respiratory system is common in chronic hypoxia, causing severe depression of respiration or apnea from relatively small doses. If the availability of oxygen is inadequate for aerobic cellular metabolism, energy is provided by less efficient anaerobic pathways that produce metabolites other than carbon dioxide and water. The tissues most sensitive to hypoxia are the brain, heart, pulmonary vessels, and liver. Treatment may include cardiotonic and respiratory stimulant drugs, oxygen therapy, mechanical ventilation, and frequent analysis of blood gases. Compare hypoxemia. See also acute hypoxia, anoxia, chemoreceptor, chronic hypoxia, hyperventilation, respiratory center. hypoxic, adj.

hypoxia

Cardiology A low O2 concentration in arterial blood. See Cerebral hypoxia.

hy·pox·i·a

(hī-pok'sē-ă)
Lower than normal levels of oxygen in inspired gases, arterial blood, or tissue, short of anoxia.

hypoxia

Deficiency of oxygen in the tissues. Local hypoxia can lead to GANGRENE; general hypoxia to the death of the individual. Hypoxia occurs mainly as a result of obstructive artery disease, especially ATHEROSCLEROSIS. It may also occur from respiratory disease that prevents access of oxygen to the blood, ANAEMIA, certain forms of poisoning and suffocation.

hypoxia

the reduction of oxygen levels.

Hypoxia

Hypoxia, or altitude sickness, reduces the amount of oxygen in the brain causing such symptoms as dizziness, shortness of breath, and mental confusion.

hypoxia

deficiency of oxygen in the body due to (1) low partial pressure of oxygen in the blood, because of (i) low oxygen in inspired air, e.g. at altitude, (ii) inadequate ventilation due to lung disease or depression of breathing by drugs (in this case accompanied by hypercapnia), (iii) defective transfer of oxygen from lung alveoli to blood; (2) low content of oxygen in the blood due to inadequate or abnormal haemoglobin; (3) failure of the heart and circulation to deliver an adequate oxygen supply to the tissues, even though the content in the blood may be normal; (4) poisoning of cells so that they cannot use the oxygen delivered to them.

hypoxia

subnormal levels of blood (and tissue) oxygenation (see wound hypoxia)

hypoxia (hī·pkˑ·sē·),

n insufficient oxygen supply to tissues in the body; symptoms include hypertension, dizziness, peripheral vasoconstriction, tachycardia, mental confusion, and other manifestations.

hypoxia

An inadequate supply of oxygen to tissues. It may occur in some pathological conditions. Examples: in long-standing cases of diabetes there is corneal hypoxia (with consequent high epithelial fragility and some neovascularization) and retinal hypoxia (with consequent neovascularization). Corneal hypoxia (with consequent oedema, loss of sensitivity, etc.) may also occur in contact lens wear. See anoxia; epithelial microcysts; mitosis; oedema; critical oxygen requirement; proliferative retinopathy; corneal exhaustion syndrome; overwear syndrome; tear pumping.

hy·pox·i·a

(hī-pok'sē-ă)
Decreased below normal levels of oxygen in inspired gases, arterial blood, or tissue, without reaching anoxia.
[hypo- + oxygen]

hypoxia (hīpok´sēə),

n low oxygen content or tension.
hypoxia, anemic,
n a type brought about by a reduction of the oxygen-carrying capacity of the blood because of a decrease in the complete blood counts or an alteration of the hemoglobin constituents.
hypoxia, anoxic,
n a type resulting from inadequate oxygen in inspired air or interference with gaseous exchange in the lungs.
hypoxia, histotoxic,
n a type resulting from the inability of the tissue cells to use the oxygen that may be present in normal amount and tension.
hypoxia, metabolic,
n a type resulting from an increased tissue demand for oxygen.
hypoxia, stagnant,
n a type resulting from decreased circulation in an area.

hypoxia

a broad term meaning diminished availability of oxygen to the body tissues.
Its causes are many and varied. There may be a deficiency of oxygen in the atmosphere, as in altitude sickness, or a pulmonary disorder that interferes with adequate ventilation of the lungs. Anemia or circulatory deficiencies can lead to inadequate transport and delivery of oxygen to the tissues. Finally, edema or other abnormal conditions of the tissues themselves may impair the exchange of oxygen and carbon dioxide between the capillaries and the tissues. The effect of hypoxia is to reduce the functional activity of tissues. The initial response may be one of temporarily increased activity. Terminally the tissue may be irreparably damaged.

anemic hypoxia
due to inadequate supply of hemoglobin in the blood.
cerebral hypoxia
may be acute or chronic causing either a tremor-convulsion syndrome or one of longer term weakness, ataxia, apparent blindness and lethargy.
fetal hypoxia
occurs as a result of deprivation of the fetus of oxygen during parturition, because it is delayed or the umbilical cord pinched off. Clinically there is weakness, imbecility, disinclination to suck, possibly hypothermia. Foals experience a much more violent, convulsive or dummy syndrome. See also neonatal maladjustment syndrome. Called also intrapartum hypoxia.
intrapartum hypoxia
see fetal hypoxia (above).
ischemic hypoxia
insufficient oxygen in tissues because of an inadequate blood supply.
stagnant hypoxia
inadequate supply of oxygen to tissues because of slow rate of passage of the blood through the tissues.
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