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Calculating Parenteral Dosages in Solution

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Presentation on theme: "Calculating Parenteral Dosages in Solution"— Presentation transcript:

1 Calculating Parenteral Dosages in Solution
Injections mixtures that contain the drug dissolved in an appropriate liquid Dosage or solution strength the amount of drug contained within a volume of solution Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Dosage or solution strength - found on the label

2 Calculating Parenteral Dosages In Solution (cont.)
Dosage strength expressed in milligrams per milliliter as a percent Lidocaine 1% = 1 g lidocaine /100 mL as a ratio Epinepherine 1:1000 = 1 g epinepherine / 1000 mL Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

3 Calculating Parenteral Dosages In Solution (cont.)
Physician’s order – the amount of medication Calculate – milliliters of solution that contains the desired dose Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Physician’s order – usually in milligrams, units, grams, etc.

4 Calculating Parenteral Dosages In Solution (cont.)
Follow the ABCs of dosage calculation. Start with H, Q, and D Step A: Convert Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. H = dose on hand Q = units of quantity of dose on hand D = desired dose Convert units of dosage ordered to units of desired dose.

5 Calculating Parenteral Dosages In Solution (cont.)
Step B: Calculate Proportion Dimensional Analysis Formula Method Step C: Think!...Is It Reasonable? Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Use the method of your choice to calculate the amount to administer. Does the amount calculated make sense?

6 Syringe Sizes After you determine the amount to give, you must select the appropriate syringe and needle. Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

7 Syringe Sizes (cont.) Rule 14-1 Selecting a syringe:
If the amount of injection to administer is 1 mL or more, use a standard 3 mL syringe. Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

8 Syringe Sizes (cont.) Rule 14-1 (cont.)
If the amount of injection to administer is less than 1 mL, use a 1-mL tuberculin syringe. If the amount of injection to administer is less than 0.5 mL, use a 0.5-mL tuberculin syringe. Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

9 Calculating Parenteral Dosages in Solution (cont.)
Amount to be administered is calculated at 0.6 mL. Which syringe would you use? Since this is less than 1 mL and greater than 0.5 mL, a tuberculin syringe should be used. Example Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

10 Calculating Parenteral Dosages in Solution (cont.)
Rule 14-2 Rounding the Amount to Administer: Round volumes greater than 1 mL to the nearest tenth (one decimal). Round volumes less than 1 mL to the nearest hundredth (two decimals). Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. 3 mL syringe is calibrated in tenths. Tuberculin syringe is calibrated in hundredths.

11 Calculating Parenteral Dosages in Solution (cont.)
Amount to be administered is calculated to be 1.66 mL The volume is greater than 1 mL – round to the nearest tenth – 1.7 mL Example Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

12 Calculating Parenteral Dosages in Solution (cont.)
Amount to be administered is calculated to be mL. The volume is less than 1 mL – round to the nearest hundredth – 0.53 mL. Example Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

13 Calculating Parenteral Dosages in Solution (cont.)
Can the amount to be administered be safely injected into one site? If not, divide the amount into equal (or nearly equal) parts. Administer them in separate sites. Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

14 Calculating Parenteral Dosages in Solution (cont.)
Rule 14-3 Maximum volumes for injections: Intramuscular Injections Adult mL Adult Deltoid (arm) 1 mL Child (6-12 years old) 2 mL Child (0-5 years old) 1 mL Infant (premature) 0.5 mL Subcutaneous injections 1 mL Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Dosages larger than these maximum volumes are rare and should be checked and verified.

15 Calculating Parenteral Dosages in Solution (cont.)
Ordered: Compazine 7.5 mg IM On hand: Compazine 5 mg/mL Find the amount to administer and select the proper syringe. Example Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. H = 5 mg Q = 1 mL D = 7.5 mg

16 Calculating Parenteral Dosages in Solution (cont.)
H = 5 mg Q = 1 mL D = 7.5 mg Step A No conversion is needed. Example (cont.) Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Dose ordered is in same units of measure as dose on hand.

17 Calculating Parenteral Dosages in Solution (cont.)
Step B Use method of choice to calculate amount to administer. 7.5 mg / 5 mg x 1 mL = A 1.5 x 1 mL = 1.5 mL = A Example (cont.) Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. 7.5 mg / 5 mg x 1 mL = A [cancel units (mg)] 1.5 x 1 mL = 1.5 mL = A

18 Calculating Parenteral Dosages in Solution (cont.)
Step C Desired dose is 1.5 times the dose on hand, so it is reasonable. Standard 3 cc syringe is used since amount to administer is greater than 1 cc. Example (cont.) Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Step C Desired dose is 1.5 times the dose on hand, and amount to administer is also 1.5 times as quantity of dose on hand so it is reasonable. Standard 3 cc syringe is used since amount to administer is greater than 1 cc.

19 Medications Expressed in Percent or Ratio Format
Rule 14-4 When a solution strength is expressed as a percent or ratio: Convert the percent or ratio to a dosage strength of g/mL, mg/mL, or units/mL. Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation.

20 Medications Expressed in Percent or Ratio Format
Rule 14-4 (cont.) Calculate the amount to administer; then apply Rules 14-1 to 14-3. Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Rule 14-1: Select proper syringe size. Rule 14-2: Round correctly.

21 Practice Find the amount to administer, and select appropriate syringe. Ordered: 0.4 mg Epinephrine stat On Hand: Epinephrine 1 : 1000 Solution Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Epinephrine 1: 1000 = 1 g epinephrine in 1000 mL solution H = 1 g Q = 1000 mL D = 0.4 mg Step A 1g : 1000 mg = D : 0.4 mg [cancel units (g)] 1000 x D / 1000 = 1 x 0.4 mg/ 1000 D = mg Step B Use calculation method of choice. g / 1 g x 1000 mL = A [cancel units (g)] X 1000 mL = A 0.4 mL = A Step C The concentration is 1 mg/1 mL, so 0.4 mg/0.4 mL is reasonable. The dose is less than 0.5 mL; use a 0.5 mL tuberculin syringe. Answer: 0.4 mL Use a 0.5 mL tuberculin syringe.

22 Practice Find the amount to administer. Ordered: Zinacef 500 mg IM On Hand: Zinacef (cefuroxime for injection) 750 mg reconstituted with 3mL sterile water. Dosage strength after reconstitution is 225 mg/mL Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. H =225 mg Q = 1 mL D = 500 mg Step A No conversion is needed. Step B Use calculation method of choice. 500 mg / 225 mg x 1 mL = A [cancel units (mg)] 2.22 x 1 mL = 2.27 mL = 2.2 mL = A 2.22 greater than 1 so round to nearest tenth Step C 500 mg is slightly more than twice 220 mg, and 2.2 mL is slightly more than twice 1 mL, so it is reasonable. Since the amount is greater than 1 mL – use a standard 3 mL syringe. Answer: 2.2 mL in a standard 3 mL syringe

23 Apply Your Knowledge What kind of syringe would you use to administer 0.4 mL IM? What kind of syringe would you use to administer 2.3 mL IM? Answer: 0.5 mL tuberculin syringe Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. Amount to administer is less than 0.5 mL, so a 0.5 mL tuberculin syringe should be used. Amount to administer is greater than 1 mL, so a 3 mL standard syringe can be used. Answer: 3 mL standard syringe

24 Apply Your Knowledge What is the maximum amount of medication that can be administered IM in one site to an adult? Learning Outcome: 14.1 Calculate doses of parenteral medication in solution and select a syringe based on the dosage calculation. This is the maximum amount to administer for an adult. Answer: 3 mL


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