An elderly diabetic patient who has acute cholecysti-tis is found to have a serum sodium level of 122 mEq/L a blood glucose of 600 mg/dl. after correcting the glucose concentration to 100 mg/dl with insulin the serum sodium concentration would:
|A||Decrease significantly unless the patient also received 3% saline.|
|B||Decrease transiently but return to approximately 122 meq/L without specific therapy|
|C||Remain essentially unchanged|
|D||Increase to the normal range without specific therapy.|
(Ref: Schwartz :Principles of surgery 8th edition page no.69-71)
a. The physiologic and chemical activity of eletrolyes depend on .
i. Number of particles present per unit volume.
ii. The number of electrical charges per unit volume.
iii. The number of osmotically active particles per unit volume.
b. The difference in the ionic composition between intracellular and extracellular fluid are maintained by the semipermeable cell membrane.
c. The total no of osmotically active particles is 290- 310 osmoles in each compartment.
d. A rise in extracellular fluid concentration of a substance that doesn’t diffuse passively across cell membrane (e.g glucose or ureA. causes an increase in effective osmatic pressure, a transfer of water from cell, and dilutional hyponatremia.
e. For each 100 mg/L rise in blood glucose above normal, the serum sodium level falls approximately 3 meq/l.
f. Alternatively serum sodium level would increase by about 15 meq/L if blood glucose level falls from 600 to 100mg/dl.
g. Since the cell membranes are completely permeable to water , the effective osmotic pressure in two compartments are considered equal.
h. Any condition that alters the effective osmotic pressure in either compartment will result in redistribution of water between the compartments