plasma osmolality


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plasma osmolality

The osmotic concentration of plasma. Normally the ionic concentration in the plasma is maintained within a narrow range: 275 to 295 mOsm/kg. When plasma osmolality increases above normal, antidiuretic hormone (ADH [vasopressin]) is released. ADH prevents loss of water by the kidney and thus decreases plasma osmolality. An increase in plasma osmolality also produces the sensation of thirst, which stimulates the person to drink fluids; this, too, serves to decrease plasma osmolality.
See also: osmolality
References in periodicals archive ?
Bland-Altman plot of clinically unacceptable agreement of measured and calculated plasma osmolality for juvenile rehabilitated black-bellied whistling ducks.
(2011b) clarified whether or not increases in plasma osmolality and subsequent thirst sensation produced by dry forage feeding suppress dry forage intake.
Plasma osmolality, sodium and potassium concentrations.
The patient's plasma sodium level was low (120 mmol/L), as well as her plasma osmolality (235 mOsm/kg), while urinary sodium and osmolality levels were both high.
Increased plasma osmolality further stimulates ADH secretion and promotes water retention.
Plasma glucose was measured spectrophotometrically (Sigma, kit 16-20), and plasma osmolality was determined with a vapor pressure osmometer (Wescor, model 5500, Logan, UT).
Decreased plasma osmolality causes cellular swelling.
Normal values which rule out ADH deficiency are as follows: (a) urine osmolality 500-1400 mOsm/L, (b) plasma osmolality 288-291 mOsm/L, (c) plasma osmolality: urine osmolality [is greater than] 2, and (d) urine specific gravity [is greater than] 1.010 (Johnson, 1993).
Thus, in one study of elderly people there was a greater release of AVP in response to increasing plasma osmolality [3], although the age range of the subjects was only 52-66 years.
Increase in plasma osmolality or decrease in blood volume leads to secretion of arginine vasopressin (AVP), also called antidiuretic hormone (ADH), from the posterior pituitary gland (4,5).
The water deprivation test showed elevated serum Na+, plasma osmolality, and urine osmolality (Table 2).
This was repeated twice with similar results and a measured plasma osmolality was 403 mOsm/kg.

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