血液渗透压测试

定义

Osmolality is a test that measures the concentration of all chemical particles found in the fluid part of blood.

Osmolality can also be measured with a 尿检.

How the Test is Performed

A 需要血液样本.

How to Prepare for the Test

Follow any instructions from your health care provider about not eating before the test. Your provider may tell you to temporarily stop taking any medicines that may interfere with test results. Such medicines may include water pills (diuretics).

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a slight bruise. 这很快就会消失.

Why the Test is Performed

This test helps check your body's water balance. Your provider may order this test if you have signs of any of the following:

• 低钠(低钠血症)或失水
• Poisoning from harmful substances such as 乙醇, 甲醇, or 乙二醇
• Problems producing urine

In healthy people, when osmolality in the blood becomes high, the body releases 抗利尿激素 (抗利尿激素).

This hormone causes the kidneys to reabsorb water. This results in more concentrated urine. The reabsorbed water dilutes the blood. This allows blood osmolality to fall back to normal.

Low blood osmolality suppresses ADH. This reduces how much water the kidneys reabsorb. Dilute urine is passed to get rid of the excess water, which increases blood osmolality back toward normal.

正常的结果

Normal values range from 275 to 295 mOsm/kg (275 to 295 mmol/kg).

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

A higher than normal level may be due to:

• 尿崩症
• High blood sugar level (高血糖)
• High level of nitrogen waste products in the blood (尿毒症)
• High sodium level (hypernatremia)
• 中风 or head trauma resulting in decreased ADH secretion
• 失水(脱水)

Lower than normal levels may be due to:

• 抗利尿激素oversecretion
• Adrenal gland not working normally
• 与…相关的十大赌博靠谱网络平台 肺癌 (causing syndrome of inappropriate ADH production, or SIADH)
• Drinking too much water or fluid
• Low sodium level (低钠血症)
• SIADH, condition in which the body makes too much ADH
• Underactive thyroid gland (甲状腺功能减退)

风险

There is little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• 大出血
• Fainting or feeling lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

参考文献

Oh MS, Briefel G, Pincus MR. Evaluation of renal function, water, electrolytes, and acid-base balance. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24日艾德. Philadelphia, PA: Elsevier; 2022:chap 15.

还詹. Disorders of water balance. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11日艾德. Philadelphia, PA: Elsevier; 2020:chap 15.