Serum Osmolality Verification

[Petite06]

If you have increased serum osmolality does that mean that the blood has increased it's ability to dissolve chemicals? Then if something is excreted via osmotic diuresis that the fluid will be excreted from the area with higher amts of fluid to less?Like in cerebral edema...a med will be given to get all the fluid collected and excreted out?

Thanks

[wildmountainchild]

Serum osmolality is a way of expressing how much solute is dissolved in solution. High serum osmolality implies that in the ECF (where such things are measured) that there is a high concentration of solutes compared with the ICF. This can happen through a gain of solutes (electrolytes) or a loss of water (through dehydration, lasix,etc.)If this is through dehydration the ECF is now hypertonic compared to the ICF, water will leave the ICF and move into the ECF trying to equalize the imbalance. Osmotic diuresis in this case, would make matters worse ( I think) by increasing the osmolality of an already hypertonic solution. This is what osmotic diuretics do, increase osmolality in the blood, then in the tubules after filtration in the kidneys. Increased tubule osmolality pulls water from the peritubular capillaries and excretes it. This person is already dehydrated, they don't need more fulid loss to correct thier imbalance, they need fluid! Possibly administration of a hypotonic solution such as 1/2 normal saline to encourage water to move back into the cells from the ECF.

If this is caused by too much sodium intake or a mistake with meds that leads to too much electrolyte retention, then edema can result and the use of diuretics can help. Usually the body would be able to handle this on it's own so the person is probably having kidney issues of some kind (or diabetes).

That's what I think anyway. A great book to explain all of the above is the the "Fluid and Electrolytes Made Incredibley Easy". They really do make just about any nursing subject incredibley easy.

Of course if I'm wrong, please correct me!