# RECONSTITUTION OF DEXTROSE SOLUTIONS INTO DESIRED STRENGTH |Ogunlabi David | Featured Article | Care City Learning  National Cancer Institute | Unsplash

## RECONSTITUTION OF DEXTROSE SOLUTIONS INTO DESIRED STRENGTH.

Ogunlabi, David (RN)

Example 1:
Prepare 150ml of a 8.5% dextrose solution. You have D5W and D10W. How much of each solution is needed?

In the example above, there are three (3) different strengths/concentrations/percentages of dextrose solution:
5%, 8.5% and 10% dextrose solution.

The constituting strengths are 5% (solution A) and 10% (solution B).
The final strength is 8.5% (solution C).

METHOD 1.

The standard formula for calculating the strength and volume of constituted solution is:

(% of sol. A * Vol of sol. A) + (% of sol. B * vol of sol. B) = (% of sol. C * Vol of sol C)

% of Sol. A = 5%= 5÷100= 0.05
% of Sol B = 10%= 10÷100= 0.1
% of Sol C = 8.5%= 8.5÷100= 0.085
Vol of Sol A is unknown
Vol of Sol B is unknown
Vol of Sol C = 150ml

Vol A + Vol B = Vol C
A+B = 150
A= (150-B)

Insert the values into the formula.

(% of sol. A * Vol of sol. A) + (% of sol. B * vol of sol. B) = (% of sol. C * Vol of sol C)

(5%A) + (10%B) = (7.5%C) (5%)(150-B) + (10%B) = (8.5%150)
0.05(150-B) + (0.1B) = (0.085150) (0.05150 – 0.05*B) + 0.1B = 12.75
7.5 – 0.05B + 0.1B = 12.75
Collect like terms
0.1B – 0.05B = 12.75-7.5
0.05B = 5.25
B = 5.25 ÷ 0.05
B = 105ml

Remember that A = 150-B
A= 150-105
A= 45ml.

Therefore, 45ml of sol A (5% dextrose) will be added to 105ml of sol B (10% dextrose) to produce 150ml of sol C (8.5% dextrose). Crissy Jarvis | Unsplash

ALTERNATIVE METHOD (METHOD 2).
Step 1: Find the difference between each constituting strength and the final strength.
Constituting strength= 5% and 10%
Final strength= 8.5%
Difference between 5% and 8.5%= 8.5%-5%= 3.5% (higher difference)
Difference between10% and 8.5%= 10%-8.5%= 1.5% (lower difference)

Step 2: Add the results of the difference in Step 1 above.
3.5+1.5= 5

Step 3: Divide each difference in step 1 by the sum of the difference in Step 2 and multiply by the volume of final solution.
(3.5÷5)150ml = 105ml (1.5÷5)150ml
= 45ml

Step 4: Assign the higher value to the constituting strength with lower difference (look at step 1); and the lower value to the constituting strength with higher difference (look at step 1)
There are two constituting strength: 5% and 10% dextrose.
So the higher value (105ml) is assigned to the constituting strength with lower difference (10% dextrose)
And the lower value (45ml) is assigned to the constituting strength with higher difference (5% dextrose)

In conclusion, 45ml of sol A (5% dextrose) will be added to 105ml of sol B (10% dextrose) to produce 150ml of sol C (8.5% dextrose).

Try this.

1. Prepare 20 mL of dextrose 7.5% weight in volume (w/v) using dextrose 5% and dextrose 50%. How many milliliters of each will be needed?

## About The Author David Ogunlabi

A Certified Critical Care Nurse driven with strong passion to impact knowledge. Founder of the Global Impact Health Initiative (GiHi), a nongovernmental organization that seeks to impact knowledge through organizing trainings, seminars, tutorials and lectures for nurses and nursing students. The organization also holds a yearly national drug dosage calculation competition for nurses.

Author of THE NURSE, THE MATH AND THE MEDICATION, a Handbook on Drug Dosage Calculation, to get a copy of the book, send the author a direct message here. You can reach Ogunlabi David on Facebook, or on WhatsApp here and Instagram.

## GLOBAL IMPACT HEALTH INITIATIVE (GiHi)

Presents

NATIONAL DRUG DOSAGE CALCULATION COMPETITION FOR NURSES (NDDCCN).

2nd Edition

CASH PRIZE: #50,000

REGISTRATION FEE: #1,000

DEADLINE FOR REGISTRATION:
30TH JUNE, 2020.

Interested nurses and nursing students should contact GiHi

Study materials and curriculum will be given to participants to guide their reading.

About Care City Learning

Processing…
Success! You're on the list.