Metric System, Household Systems, Converting Within & Between

Metric System, Household Systems, Converting Within & Between Systems

Calhoun Community College A physician writes a prescription for Colchicine and accidentally orders “10.0 mg,” when he should have ordered “1.0 mg.”

That’s a tiny decimal error, a mistake even the best doctor could make.

But it can be catastrophic for the patient.

The higher dose could cause Colchicine poisoning, similar to arsenic poisoning: burning in the mouth and throat, excruciating abdominal pain. Internal organs would melt away and death would likely occur within 24 to 72 hours.

The Shocking Truth About Medication Errors (http://www.forbes.com/sites/leahbinder/2013/09/03/the-shocking-truth-about-medication-errors/)  Preferred for prescribing and administering medication  It is a decimal system based on multiples of 10  Primary units of measurement is: Gram for weight Liter for volume Meter for length 1 micro  one millionth or 0.000001 or of the base unit 1,000,000 1 milli  one thousandt h or 0.001 or of the base unit 1000 1 centi  one hundredth or 0.01 or of the base unit 100 1 deci  one tenth or 0.1 or of the base unit 10 kilo  one thousand or 1000 times the base unit

Volume L = liter (base unit) mL = milliliter cc = cubic centimeter (not used anymore)

Length m = meter (base unit) cm = centimeter mm = millimeter

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED.  The unit or abbreviation ALWAYS follows the amount, put a space between them (lowercase except for L for liters). ◦ Example: 5 g NOT g 5

 Decimals are used to designate fractional metric units. ◦ Example: 1.5 mL NOT 1 ½ mL

 Omit unnecessary zeros. ◦ Example: 1.5 g NOT 1.50 g

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED.  Use a zero to emphasize the decimal point for fractional metric units of less than 1 (National Patient Safety Goals).  Example: 0.5 mg NOT .5 mg ◦ This is critical… It will prevent confusion & potential dosage error. Think about what would happened if overlooked the decimal point and misinterpreted the medication order as 5 mg instead of 0.5 mg. The dosage would be 10 times too much. It could cause DEATH!!!!!!!!!!!  When in doubt, double check, DO NOT GUESS. Ask the writer for clarification

gram g 1 g = 1000 mg NOT Gm or gm milligram mg 1 mg = 1000 mcg microgram mcg 0.001 mg = 1 mcg

liter L 1 L = 1000 mL NOT ℓ milliliter mL 0.001 L = 1 mL = 1 cc NOT mℓ cubic Cubic 1 cc centimeter centimeter DO NOT USE LIST

meter m 1 m = 100 cm = 1000 mm centimeter cm 1 cm = 10 mm millimeter mm 0.1 cm = 1 mm

1 inch = 2.5 cm

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED. Unit Abbreviation Equivalents grain gr gr i = 60 (65) mg ounce oz 1 ounce = 30 mL pint pt 16 oz = 500 mL quart qt pt ii = 32 oz = 1000 mL = 1 L Dram* 1 dram = 4 mL

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED. a) .3g b) 0.3 Gm c) 0.3 g d) .3 Gm e) 0.30 g a) .3g b) 0.3 Gm c) 0.3 g d) .3 Gm e) 0.30 g a) 1 1/3 ml b) 1.33 mL c) 1.33 ML d) 1 1/3 ML e) 1.330 mL a) 1 1/3 ml b) 1.33 mL c) 1.33 ML d) 1 1/3 ML e) 1.330 mL a) 5 KG b) 5.0 kg c) kg 5 d) 5 kg e) 5 kG a) 5 KG b) 5.0 kg c) kg 5 d) 5 kg e) 5 kG a) Lasix 20.0 mg b) Lasix 20 mg c) Lasix 20 MG d) Lasix mg 20 e) Lasix 20 Mg a) Lasix 20.0 mg b) Lasix 20 mg c) Lasix 20 MG d) Lasix mg 20 e) Lasix 20 Mg Unit Abbreviation Equivalents

drop gtt Used for IV calculations Teaspoon* t (or tsp) 1 t = 5 mL Tablespoon* T (or tbs) 1 T = 3 t = 15 mL

ounce (fluid) oz 1 oz = 30 mL ounce (weight) oz 1 lb = 16 oz Cup* cup 1 cup = 8 oz = 240 mL

45 mg gr ¾ gr ¼ 15 mg

gr ss 30 mg

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED.  To convert from a larger unit of measurement to a smaller one; MULTIPLY or move the decimal point to the right. ◦ Example: 3 L = ? mL ◦ THINK: Larger to Smaller: (×) ◦ Equivalent: 1L = 1000mL  Conversion factor 1000  3 L = ___mL  3 × 1000 = 3000 mL  or move decimal 3 places to right 3L = 3.000 = 3000 mL

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED.  Convert 0.3 g to mg  (think 1 g = 1000 mg, conversion factor is 1000)  Think: Larger to smaller, MULTIPLY  Multiple by 1000: ◦ 0.3 g = 0.3 x 1000 = 300 mg  or move decimal 3 places to right ◦ 0.3 g = 0.300 = 300 mg

3- 23  To convert from a smaller unit of measurement to a larger one, DIVIDE or move the decimal point to the left. ◦ Example: 400 mg = ? g ◦ THINK: Smaller to Larger: () ◦ Equivalent: 1 g = 1000 mg  (conversion factor = 1000)  400 mg = 400  1000 = 0.4 g  Or move the decimal 3 places to the left 400 = 0.400 = 0.4 g

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED.  Convert 5000 mL to L  (think 1 L = 1000 mL, conversion factor is 1000)  Think: Smaller to Larger, DIVIDE  Divide by 1000: ◦ 5000 mL = 5000 ÷ 1000 = 5 L  or move decimal 3 places to left ◦ 5000 mL = 5.000 = 5 L

3- 25  You can use this diagram when converting dosages within the metric system.

Move decimal point 3 places to the left for each step. kg g mg mcg Move decimal point 3 places to the right for each step.

MEMORIZE this too: 1 kg = 2.2 lb

© 2004 Delmar Learning, a division of Thomson Learning, Inc. ALL RIGHTS RESERVED.  Can be used within the 1. Solve for X (multiply same system or between inner terms, then outer systems terms)  Solving for X 8 mg = ___ g ◦ 1 X 8 = 1000 X x 1. State the known ◦ 8 = 1000 x equivalent first, then add ◦ 1 x 8=1000x X 1 the incomplete ration to ◦ 1000 1000 the other side, labeling ◦ 8 = 1000 x all terms in the ◦ 1000 1000 proportion 1000 mg: 1 g = 8 mg : x g ◦ X = 8/1000 = 0.008 g ◦ X = 0.008 g  Simpler to multiple or divide…  Solving for X 8 mg = ___ g ◦ Convert 8 mg = ___ g ◦ Approximate equivalent: 1g = 1000 mg ◦ Conversion factor is 1000 ◦ Think: Smaller to larger, therefore divide (or move the decimal 3 places to the left)  8 mg = 8 ÷ 1000 = 0.008 g  To convert from a larger unit to a smaller unit of measure, you multiply by the conversion factor and To convert from a smaller to a larger unit of measure, you must divide by the conversion factor.

 Example: Convert 45 mL to t Approximate Equivalent 1 t = 5 mL Conversion factor = 5 THINK: Smaller to Larger so DIVIDE 45 / 5 = 9 t