No stupid questions - page 3

by ohbet 4,169 Views | 20 Comments

Will some knowlegable nurses answer my 3 questions of the day? remember there are no stupid questions. 1.I know what a myocardial infaction is,but what is a Inferior MI? 2.I once heard a lecturer,she is a emergency dept.... Read More


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    Originally posted by ohbet
    Well thanks again all you helpful and knowledgeable nurses.
    Just one follow up question on the IV fluids. So I understand now that D5W is hypotonic,which means that once its in the vessels it will enter the cell by osmosis.
    But what happens when a combo of D5W and NS is ordered together? Why is this combo solution ordered,is it for volume repacement and nutrition?
    Hypo and Hyper refer to the concentration of the SOLUTES, not the water content, relative to the concentration inside the cell.

    Isotonic: is a solution that has the same concentration of solutes in both the cells and the extracellular fluids.

    Hypotonic: is a solution that the concentration of solutes is LOWER outside the cell. Less SOLUTES, more water. So, more WATER has to travel into the cell to achieve equilibrium of the SOLUTE. Remember that water is a TRANSPORT molecule of the solutes. This can cause lysis of the cell. But, also remember that as more water travels INTO the cells, less water is available OUTSIDE the cells.

    Hypertonic: is a solution that the concentration of solutes is HIGHER outside the cell. More SOLUTES, less water. Water travels OUT of the cells because more water is needed OUTSIDE the cell to achieve equilibrium of the extracellular fluids. Hypertonic solutions can dehydrate the cell or cause it to plasmolyze.

    OK. Now why would a MD order a combination of NS a (isotonic solution) with D5W (a hypotonic), you asked? The hyportonic solution would cause the cells to become filled with more water at the expense of total fluid volume. The D5W, then, would cause a fluid volume deficit or HYPOTONIC DEHYDRATION. Hypotonic dehydration is almost always accompanied by a sodium deficiet, because sodium is the chief extracellular ion (electrolyte). The combination of NS with D5W would help replenish fluids both inside and outside the cell.

    This combination is often used with dehydration d/t diarrhea where a lot of sodium is lost. Also for hypovolemic shock.

    The dextrose in the D5W isn't for nutrition (there isn't enough glucose there for that), but because glucose is necessary to provide the energy necessary for all the functional processes of the cell: metabolism, respiration, reproduction, etc. And that is another huge topic in itself. The glucose is to help the little cells do what they're suppose to be doing to keep the person (the cells, tissues, organs, etc.) alive.

    Are you sorry you asked ???
    Last edit by Youda on Sep 16, '02


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