How to Calculate the Amount of Sodium in a Serum

Serum sodium level is a measure of the dissolved sodium in a patient's blood, and determining serum sodium levels is one of the standard tests hospitals use before putting a patient on IV feeding or IV-delivered drugs. When physicians need to put patients on IV saline drips, they also need to calculate how much the serum sodium levels in a patient's blood will change based on the saline intake. This is a simple equation, taking in inputs from the patient's body mass and gender and the amount of time he is on a saline drip.

Instructions

• 1

  Write down the patient's baseline serum sodium levels. For most adults, a healthy range is from 135 to 145 milliequivalents per liter (meq/L) It is a number from a blood test done by the hospital and will be on the patient's chart if the test has been run. (It's one of the routine blood tests at a hospital.)

• 2

  Determine the amount of milliliters per hour that the patient is receiving the 0.9 percent saline solution (0.9% saline solution is the medical standard for IV drips). This number is likely to be on his IV chart. Divide this number by 1,000, and then multiply the result by 154 meq/L. (154 is the constant for milliequivalents of saline in 0.9 percent saline solution.) This will give the number of milliequivalents per hour that the patient is getting. The algebraic formulation is (ml/hr) / 1,000 x 154 meq/L = meq/hr.

• 3

  Divide the meq/hr by 0.5 over the patient's weight in kilograms for women, and 0.6 over the patient's weight in kilograms for men. This will give the increase in sodium ions per each hour the subject is on saline solutions. This is the serum sodium increase. Algebraically, the formula is meq/hr / (0.5/weight in kg) for women and meq/hr / (0.6/weight in kg) for men.

• 4

  Multiply the serum sodium increase per hour times the number of hours the patient is on the saline drip. This is the amount of sodium by which the patient's serum levels will increase (in meq/L) after this many hours of treatment.