Question

A patient is receiving Dextrose 5% in 0.45% Sodium Chloride Injection and 40 mEq of potassium chloride in a total volume of 1000 mL through an IV set that delivers 15 drops per ml. The IV fluid has been running at a rate of 12 drops per minute for 15 hours. Molec Weights: Dextrose = 180, Na = 23, K = 39, CI = 35.5 1. How many mEq of potassium chloride have been administered so far? K = 39; Cl = 35.5; Na = 23; Dextrose = 180 II. How many grams of KCl have been administered over the 15 hour period? III. How many millimoles of KCl have been administered over the 15 hour period? IV. What is the total osmolarity of the IV fluid being administered? Express your answer as milliosmoles, rounded to the nearest whole number, per 1000 ml.

Answer 1

1)

no. of drops delivered in 15 hours = 12x15x60 = 10,800 ( since 12 drops delivered per minute and 1 hour = 60 min )

15 drops = 1 mL

therefore, 1 drop is equivalent to 1 / 15 mL

therefore,

10,800 drops is equivalent to 10,800 x (1 / 15) = 720 mL of solution

1000 mL of solution contains 40 mEq of potassium chloride

therefore ,

720 mL of solution contains (40/1000)x720 = 28.8 mEq of potassium chloride

therefore ,

28.8 mEq of potassium chloride is administered in 15 hours.

2)

1 mEq of potassium chloride = 1 millimole of potassium chloride ( since valency of potassium and chlorine is one )

therefore ,

28.8 mEq of potassium chloride = 28.8 millimole of potassium chloride

therefore ,

weight of 28.8 millimole of potassium chloride = 28.8x74.5 mg = 2145.6 mg = 2.1456 grams ( since molecular weight of potassium chloride = 74.5 g )

therefore,

2.1456 grams of potassium chloride have been administered over 15 hour period .

3)

1 mEq of potassium chloride = 1 millimole of potassium chloride ( since valency of potassium and chlorine = one )

since 28.8 mEq is administered in 15 hours,

therefore,

28.8 millimoles of potassium chloride is administered over 15 hours period.

4)

1000 mL of solution contains 40 mEq = 40 millimoles = 40x2 = 80 milliosmoles of potassium chloride ( since potassium chloride dissociates into potassium and chloride ions in solution )

1000 mL of solution contains 50 g of dextrose = 50 / 180 = 0.28 moles = 280 millimoles = 280 milliosmoles of dextrose ( since solution contains 5% dextrose , dextrose does not dissociates in solution and molecular weight of dextrose = 180 g )

1000 mL of solution contains 4.5 g of sodium chloride = 4.5 / 58.5 = 0.077 moles = 77 millimoles = 77x2 = 154 milliosmoles ( since solution contains 0.45% sodium chloride, sodium chloride dissociates into sodium and chloride ions and molecular weight of sodium chloride is 58.5 g )

therefore,

1000 mL contains 80 milliosmoles of KCl + 280 milliosmoles of dextrose + 154 milliosmoles of NaCl = 514 milliosmoles per 1000 mL of solution.