出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/24 18:28:14」(JST)
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Cyanosis of the hand in someone with low oxygen saturations
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| ICD-10 | R23.0 |
|---|---|
| ICD-9 | 782.5 |
| eMedicine | med/3002 |
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface having low oxygen saturation. Based on Lundsgaard and Van Slyke's work, Lundsgaard C, Van Slyke DD. Cyanosis. Medicine. 2(1): is classically described as occurring if 5.0 g/dL of deoxyhemoglobin or greater is present.[1] What is commonly forgotten, however, is that this was based on an "estimate" of capillary saturation based on a mean of arterial versus peripheral venous blood gas measurements.[2] Since estimation of hypoxia is usually now based either on arterial blood gas measurement, or pulse oximetry, this is probably an overestimate, with evidence that levels of 2.0 g/dL of deoxyhemoglobin may reliably produce cyanosis.[3] Since, however, the presence of cyanosis is dependent upon there being an absolute quantity of deoxyhemoglobin, the bluish color is more readily apparent in those with high hemoglobin counts than it is with those with anemia. Also the bluer color is more difficult to detect on deeply pigmented skin. When signs of cyanosis first appear, such as on the lips or fingers, intervention should be made within 3–5 minutes because a severe hypoxia or severe circulatory failure may have induced the cyanosis.
The name cyanosis, literally means "the blue disease" or "the blue condition." It is derived from the color cyan, which comes from kyanos, the Greek word for blue.[4]
Cyanosis is defined as a bluish discoloration, especially of the skin and mucous membranes, due to excessive concentration of deoxyhemoglobin in the blood caused by deoxygenation.
Cyanosis is divided into two main types: Central (around the core, lips, and tongue) and Peripheral (only the extremities or fingers).
Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood oxygenation in the lungs. It develops when arterial oxygen saturation drops to ≤85% or ≤75%.
Acute cyanosis can be a result of asphyxiation or choking, and is one of the surest signs that respiration is being blocked.
Central cyanosis may be due to the following causes:
1. Central nervous system (impairing normal ventilation):
2. Respiratory system:
3. Cardiovascular diseases:
4. Blood:
5. Others:
Peripheral cyanosis is the blue tint in fingers or extremities, due to inadequate circulation. The blood reaching the extremities is not oxygen rich and when viewed through the skin a combination of factors can lead to the appearance of a blue color. All factors contributing to central cyanosis can also cause peripheral symptoms to appear, however peripheral cyanosis can be observed in the absence of heart or lung failures. Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.
Peripheral cyanosis may be due to the following causes:
Differential cyanosis is the bluish coloration of the lower but not the upper extremity and the head. This is seen in patients with a patent ductus arteriosus. Patients with a large ductus develop progressive pulmonary vascular disease, and pressure overload of the right ventricle occurs. As soon as pulmonary pressure exceeds aortic pressure, shunt reversal (right-to-left shunt) occurs. The upper extremity remains pink because the brachiocephalic trunk, left common carotid trunk and the left subclavian trunk is given off proximal to the PDA.
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| リンク元 | 「中心性チアノーゼ」 |
| 関連記事 | 「central」 |