What is the osmotic pressure of plasma crystals in KPa

The normal value of plasma crystal osmotic pressure is 720-797 kPa, mainly formed by small molecular solutes such as electrolytes, glucose, and urea in plasma. Osmotic stability is crucial for maintaining water balance inside and outside cells, influenced by factors such as sodium ion concentration, blood glucose levels, renal function status, fluid acid-base balance, and hormone regulation.

1. Sodium ion dominance:

Approximately 90% of plasma crystal osmotic pressure is contributed by sodium ions and their accompanying anions. The normal blood sodium concentration is 135-145mmol/L, and every 1mmol/L increase can increase osmotic pressure by about 1.86kPa. Sodium ions are precisely regulated by the renal aldosterone system, and excessive intake of salt or dehydration may lead to an increase in osmotic pressure.

2. Blood glucose effect:

An increase of 5.6 mmol/L in blood glucose can increase osmotic pressure by approximately 0.56 kPa. When blood sugar in diabetes patients increases significantly, hyperosmolar state may be triggered. During testing, it is important to distinguish between temporary postprandial hyperglycemia and pathological hyperglycemia, which have a sustained impact on osmotic pressure.

3. Urea nitrogen action:

Urea, as a protein metabolic end product, accounts for about 5% -10% of normal osmotic pressure. When renal insufficiency occurs, the accumulation of urea can increase osmotic pressure, but urea can freely penetrate the cell membrane without causing cell dehydration. Therefore, in clinical practice, effective osmotic pressure is often calculated to exclude the influence of urea.

4. Acid base balance correlation:

During metabolic acidosis, hydrogen ions enter cells to exchange potassium ions, leading to an increase in blood potassium; The opposite is true for alkalosis. Changes in blood potassium concentration can affect crystal osmotic pressure, accompanied by changes in anion gaps, further affecting the calculated osmotic pressure.

3. Hormone regulation mechanism:

Antidiuretic hormone maintains osmotic pressure stability by regulating tubular water reabsorption. When the osmotic pressure exceeds 285mOsm/kg, hypothalamic osmoreceptors trigger ADH release, prompting the kidneys to retain water to dilute plasma solute concentration. Maintaining normal plasma crystal osmotic pressure requires attention to electrolyte balance and water intake. Drink 1500-2000ml of water daily and avoid a high salt diet. Patients with hypertension should control their sodium intake to below 5g/day. Patients with diabetes need to monitor blood sugar regularly, and those with abnormal renal function need to limit protein intake. Timely replenish electrolyte containing drinks after exercise, and increase the frequency of fluid replacement when working in high temperature environments. When experiencing persistent symptoms of osmotic pressure abnormalities such as thirst, oliguria, or confusion, immediate medical attention should be sought for electrolyte and renal function testing.