Chapter 8 Converting between

Measurement Systems

Dr. Kevin Perrino

Critical Thinking

Q: Why is it important to learn the standard conversions among the measurement systems used in medical situation?

Critical Thinking A: While tables are available and are useful in

confirming that the conversion ratio has been correctly identified, it is important that healthcare professionals learn the standard conversion ratios. When these ratios are known and understood, professionals will have a better understanding of how the measurement systems relate to one another. As a result errors will be less frequent and possibly less significant. When tables are relied upon for the conversions, the measurement can be viewed as simply numbers rather than as the physical quantities they represent. Resulting in possible errors that have serious consequences for patient care.

Ratios and Proportions

• Used to convert when the dosage available is not in the same measurement unit as the doctor prescribed.

• Ratio: expression comparing two quantities

• Proportion: comparing two equivalent fractions or ratios

What is a ratio and how is it written?

Solving Unknown Variables

• Numerators must be of the same units.

• Denominators should be of the same units.

• 1 mL : 15 gtts is the same as 2 mL : 30 gtts

• 1 mL/15 gtts = 2 mL/30 gtts

Solving Unknown Variables (cont’d.)

Using Ratio/Proportion

• When setting up both ratios, be sure to label all of the terms, including x with the correct measurement to ensure that the equations are equivalents.

Common Measurements Used in Conversions

Volume Conversions – Apothecary to Metric

fʒ x = ______ mL

• Remember, this is 10 fluid drams• 4 mL = fʒ i• 4 mL / fʒ i = x mL / fʒ x•

• 4 x 10 = 40• 1 x x = x• 1 x = 4 x 10 = 40• fʒ x = 40 mL

Volume Conversions – Metric to Household

• Known amounts – 1 pint = 500 ml

• 750 mL = ________________ pint(s)

• 500mL/1 pint = 750 mL / x pint

• 500 x = 750

• x = 750/500

• x = 1.5 pt

Weight Conversions

Weight Conversions between the Metric and Apothecary Systems

300 mg = gr ______• Remember 60 mg = 1 gr or 60 mg / gr i• 60 mg / gr i = 300 mg / x gr

• 60 x x = 60x• 300 x 1 = 300• 60x = 300• 60x/60 = 300/60• x = 5• 300 mg = gr v

Convert quantities into same unit of measure as Convert quantities into same unit of measure as you convert within the metric system.you convert within the metric system.

60 mg 300 mg gr i x gr

Length Conversions

• 2.5 cm = 1 inch• 2.5 cm / 1 in = x cm / 14 in

• 2.5 x 14 = 35• 1 x x = x• x = 35• 14 inches = 35 cm

An abdominal cavity was opened with a 14-inch incision. Convert this measurement into cm.

2.5 cm x cm1 in 14 in

Chapter 21

Endocrine System Disorders

Critical ThinkingJane has been a patient at the practice for

nearly 25 years. Her medical history is well known by the doctor and staff alike. She has been on a maintenance program of antidepressants for nearly 10 years and has been doing well. Five years ago, she was diagnosed with type II diabetes and has been using an oral hypoglycemic agent very effectively. As she is making her next appointment, she causally mentions that her antidepressant has been changed recently. Given her history of doing well with the combination of prescription medications, would this comment raise any questions for you?

Critical ThinkingA: At this point, it is important to ask Jane which

antidepressant she is now taking and the dosage. If she is now taking a monoamine oxidase (MAO) inhibitor - - a more rarely prescribed class of antidepressant – it could inter act with her oral hypoglycemic medication. It is important to note the change and check with the physician before she leaves the office. Even the most cooperative patients sometimes unknowingly fail to provide information. That lack of information could affect drug efficacy or result in dangerous drug interactions.

The Endocrine System

• Endocrine system is a network of glands that secretes hormones necessary for body functions directly into bloodstream

• Hormones are carried by circulatory or lymphatic system to tissues and other glands.

Major Endocrine Glands

Endocrine Disorders: Common Symptoms

• Mental deviations• Exceptional changes in energy levels• Growth abnormalities• Skin, hair, nail changes• Weakness and atrophy of muscles• Emotional disturbances, psychological disorders• Edema• Changes in blood pressure with heart irregularities• Sexual irregularities• Changes in urinary output

Endocrine Disorder Medications:Common Side Effects

• Increased appetite, swelling• Palpitations, tremors, nervousness• Tachycardia, increased blood pressure,

headache• Hypoglycemia, nausea, heartburn, diarrhea• changes in diet

Thyroid Gland• Largest gland• Located in anterior neck• Two lobes on either side of larynx

Thyroid Gland Hormones

• T3—triiodothyronine

• T4—thyroxine

• calcitonin• T3 and T4 controlled by TSH• T3 and T4 stimulate protein

synthesis, increase blood sugar levels, decrease serum cholesterol levels.

Goiter

Thyroid Replacement Therapy• TSH and T4 levels routinely measured to

evaluate thyroid function

• Thyroid hormones treat hypothyroidism, not obesity.

• Therapy starts with small doses; incrementally increased until adequate response is reached.

• Long-term thyroxine use associated with osteoporosis.

Synthroid/Levothyroid

Thyroid Agents: Patient Education for Compliance

• Thyroid replacement therapy is lifelong.

• Do not discontinue medication without consulting physician.

• Take medication in AM on empty stomach to avoid insomnia.

• Palpitations, nervousness, headache may be signs of toxicity.

• Iodized salt is an excellent source of iodine necessary for thyroid hormone effectiveness.

Hyperthyroidism

• Hypersecretion of thyroid hormones due to tumors or Graves’ disease in most cases

• Symptoms include increased cell metabolism, weakness, anxiety, heat production

• Treatment may include antithyroid medications, irradiation of thyroid gland, surgical removal of tissue

Antithyroid Medications• Interfere with synthesis of thyroid hormones

• Drugs—iodine, radioactive iodine, thioamide derivatives

• side effects—rashes, nausea and vomiting, stomach pain, myalgia, fever

• Agents cross placenta and stop fetal development

Hyperthyroidism:Patient Education for Compliance

• Patients taking radioactive iodine should avoid prolonged contact with people, especially children.

• Dispose of body waste products properly.

• Report any signs of sore throat, fever, or bruising to physician.

• Dilute iodine solutions with fruit juice to make them more palatable.

Pancreatic HormonesPancreatic Hormones

Insulin

• Aids in utilizing glucose as energy

• Stores excess glucose as glycogen in liver

• Converts glucose to fat

• Decreases blood glucose levels

Diabetes Mellitus• Disorder of carbohydrate metabolism

• insulin deficiency• insulin resistance

• Classic signs—polydipsia, polyphagia, polyuria

• Sixth leading cause of death in United States

• Affects about 16 million Americans

• 90%–95% of cases are adult onset

Diabetes Mellitus: T1DM vs. T2DM• Type I insulin-dependent diabetes mellitus

(T1DM) (formerly IDDM)

• Patients have little or no endogenous insulin; require exogenous insulin to survive.

• likely due to genetic abnormality

• Type II: non-insulin dependent diabetes mellitus (T2DM) (formerly NIDDM)

• usually mature onset, with patient having some insulin function with low production or insufficient secretions of beta cells.

• can be result of aging, poor diet, or genetic factors

Treatment of Diabetes Mellitus

• Dietary adjustment to limit carbohydrates

• Consistent exercise

• Drug control

• Insulin

• oral hypoglycemics

• drugs affecting glucose absorption or production

Insulin: Clinical Tips• Regular insulin is always clear.

• Other insulins are cloudy because of added precipitates.

• Return precipitates to solution by rolling vials or pens between hands.

• Never shake or agitate insulin.

• Store prefilled syringes vertically to prevent clogging of needle with precipitate.

Insulin and Other Drugs

Oral Antidiabetic/Hypoglycemic Agents

Families of oral hypoglycemic agents:

• Sulfonylureas• Glucose absorption inhibitors• Biguanides• Thiazolidinediones• Metglitinides• DPP-4 inhibitors

Thiazolidinediones (glitizones)

• Indicated in insulin-resistant patients

• Avandia improves function of beta cells and delays progression of diabetes

• Side effects—headaches, edema, weight gain

Sulfonylureas

• first oral hypoglycemic agents

• Severe hypoglycemia often pronounced unless strict diet is observed

• Become less effective after 10 years of use

• believed to increase risk of death from cardiovascular disease