Calculations- NAPLEX

Calcium Salt Conversions

*Calcium Carbonate* (Oscal, Tums), has *acid-dependent absorption* and should be taken with meals. Calcium carbonate is a dense form of calcium and contains *40% elemental calcium*. A tablet that advertises 500mg elemental calcium weighs 1,250mg. 1,250 times 0.4 is 500mg. *Calcium Citrate* (Citracal) has *acid-independent absorption* and can be taken with or without food. Calcium Citrate is less dense and only contains *21% elemental calcium*. A tablet that advertises 315mg elemental calcium weighs 1,500mg total. 1,500 times 0.21 is 315. This is why calcium citrate tablets are noticeably larger than Ca Carbonate and provide less total calcium. However, Ca Citrate may be preferred in patients who have a more basic gut (e.g. in PPI use). Calcium Acetate (PhosLo) is used as a phosphate binder and *is not for calcium replacement*. Though the capsules contain 25% elemental calcium, absorption from this formulation is poor. Carbonate and Citrate are the two main forms used for Ca replacement.

Dissociation Factor Value based on Dissociating Ions

- 1 ion: 1 - 2 ions: 1.8 - 3 ions: 2.6 - 4 ions: 3.4 - 5 ions: 4.2 - 6 ions: 5

Neutropenia Classification based on ANC

- 2,200 to 8,000 cells/mm3: Normal - <1,000 cells/mm3: Neutropenia (at risk for infection) - <500 cells/mm3: Severe neutropenia - <100 cells/mm3: Profound neutropenia

Tube Names in EN

- A tube in the nose going to the stomach is called a *Nasogastric (NG)*, or nasoenteral tube. - A tube that goes through the skin into the stomach is called a *Gastrostomy (G), or Percutaneous Endoscopic Gastrostomy (PEG) tube*. - A tube into the small intestine is called a *Jejunostomy (J) or a Percutaneous Endoscopic Jejunostomy (PEJ) tube*.

Estimated Protein Requirements based on Condition

- Ambulatory, non-hospitalized (non-stressed): 0.8 to 1 gram/kg/day - Hospitalized or malnourished: 1.2 to 2 grams/kg/day

BMI Classifications

- BMI < 18.5 = Underweight - BMI *18.5 to 24.9 = Normal weight* - BMI 25 to 29.9 = Overweight - BMI 30 or more = Obese

Arterial Blood Gases- Reference Ranges

- pH: 7.35 to 7.45 - pCO2: 35 to 45 mmHg - pO2: 80 to 100 mmHg - HCO3: 22 to 26 mEq/L - O2 Saturation: > 95% Bicarbonate on an ABG is a calculated value and the reference range will differ from a venous sample.

Common Liquid Volume Conversions

- tsp (t) = 5 mL - tbsp (T) = 15 mL - 1 fl oz = ~30 mL, 29.57 mL (actual) - 1 cup = 8 fl oz, ~240 mL, 236.56 mL (actual) - 1 pint = 16 fl oz, ~480 mL, 473 mL (actual) - 1 quart = 2 pints, 32 fl oz, ~960 mL, 946 mL (actual) - 1 gallon = 4 quarts, 8 pints, 128 fl oz, ~3,840 mL, 3,785 mL (actual)

Common Drug-Nutrient Interactions in EN

1. *Warfarin* - Many enteral products bind warfarin, resulting in low INRs and the need for dose adjustments. - *Hold tube feeds one hour before and 1 hour after warfarin administration*. - EN formulas also contain varying amounts of vitamin K, which can complicate warfarin dosing in some patients. 2. *Tetracyclines, Quinolones, and Levothyroxine* - These drug classes will *chelate* with metals, including Ca, Mg, and Iron, which reduces drug availability. - *Separate from tube feeds* 3. *Ciprofloxacin oral suspension* - A special case because the oral suspension is not used with tube feeds because not only will it chelate metals (as mentioned above), but the *oil-based suspension adheres to the tube*. - Use the *immediate-release tablets* instead. Crush and mix the tablets with water, flush the line with water, administer the medication, then flush the line with water again. 4. *Phenytoin suspension* - *Levels are reduced* when the drug binds to the feeding solution, leading to less free drug availability and sub-therapeutic levels. - *Separate tube feeds by 2 hours*

Common Compounds and # Dissociation Particles

1. Dextrose- 1 2 Mannitol- 1 3. Potassium Chloride- 2 4 Sodium Chloride- 2 5. Sodium Acetate- 2 6. Magnesium Sulfate- 2 7. Calcium Chloride- 3 8. Sodium Citrate- 4

pKa Rules

1. If *pH > pKa, more of the acid is ionized*, meaning more of the acid is in its conjugate base/salt form and un-ionized. 2. If the *pH EQUALS pKa, the ionized and un-ionized forms are equal*. 3. If the *pH < pKa, more of the acid is un-ionized*, and more of the conjugate base/salt form is ionized.

Lithium Conversions

5 mL of Lithium Citrate syrup = 300mg Lithium Carbonate = 8 mEq of Lithium ion.

Calories

A calorie is a measurement of the energy, or heat, it takes to raise the temperature of 1 gram of water by 1 degree Celsius. Calories are associated with nutrition because humans obtain energy from the food they consume or from EN/PN. Calories are provided by three components, called the Macronutrients: - *Carbohydrates* - *Fats* - *Protein* A calorie is a very small unit, and these are therefore measured in *kilocalories*, or *kcals*. Kcals are equal to 1,000 calories. However, the term *calories is used interchangeably with kcals*. On nutrition labels for foods, the calorie count of the food is labeled as Calories, with a capital C. For pharmacy calculations, *calories or Calories are meant to refer to as kilocalories, or kcals*.

Moles and Millimoles- Overview and Formula

A mole is the molecular weight of a substance in grams, or grams/mol. A millimole is 1/1,000 of the molecular weight in grams, or 1/1,000 of a mole. For *monovalent species* the numerical value of the *milliequivalent and millimole are identical*. Moles = grams / molecular weight mmols = mg / molecular weight

Body Mass Index

AKA BMI, this is a measure of body fat based on height and weight that applies to adult men and women. BMI is a useful measure of body fat, but the BMI can over-estimate body fat in persons who are muscular, and can under-estimate body fat in frail elderly persons and others who have lost muscle mass. BMI, however, is still a useful calculation because it can help classify people who are overweight or obese. Overweight and Obesity are health problems associated with increased morbidity from hypertension, dyslipidemia, diabetes, CAD, stroke, gallbladder disease, osteoarthritis, and some other conditions. Higher body weights are also associated with increases in all-cause mortality.

Acid-Base Reactions

Acid-base reactions are equilibrium reactions. There are drugs moving back and forth between the acid and base state. We can determine if the drug is acting as an acid or a base in the reaction by measuring the pH of the solution and the pKa of the compound. When the pH = the pKa, the molar concentration of the salt form and the molar concentration of the acid form of the buffer acid-base pair will be equal: *50% of the buffer will be in salt form and 50% will be in acid form*. Put in another way, when the pH = the pKa, *this is the point at which half the compound is ionized and half the compound is unionized*. If this is an acid, the unionized form will be *protonated* and the ionized form will be *de-protonated*. A "strong" acid or base means the compound dissociates 100% and a "weak" acid or base means very limited dissociation. Any time a pKa is provided, it refers to the acid form losing protons to give to the base or salt form. If the pKb is provided, think base simply because of the definitions of the two terms.

ABW and IBW

Actual Body Weight (ABW) - This is the actual/total body weight of the patient when weighed on a scale. Ideal Body Weight (IBW) - Ideal body weight is the healthy (ideal) weight for a person. It is calculated based on the sex of the patient. - Male: 50 kg + 2.3 kg x # of inches >60 - Female 45.5 kg + 2.3 kg x # of inches >60

AdjBW

Adjusted Body Weight is a very important weight for patients who are overweight/obese. It is calculated: - *IBW + 0.4(ABW - IBW)* Adults doses are generally the same for all patients (e.g. lisinopril 10mg daily), but some doses are based on weight. *Weight-based dosing (mg/kg)* is common in pediatrics and is recommended for some medications in adults. *ABW is used for weight-based dosing of most drugs in adults, but there are exceptions*. Some drugs with narrow therapeutic indexes (e.g. Aminophylline and Theophylline) are dosed based on *IBW* to avoid toxicity. Some drugs like Enoxaparin and Vancomycin are dosed based on *ABW, even if the patient is obese* because of the results from clinical trials. Drug dosing in obesity is challenging because there is a risk of underdosing (when standard dosing is used) and overdosing (when ABW is used for dosing). In clinical practice, the primary literature is typically consulted for the best dosing strategy in obese patients. However this is an algorithm in place for certain drugs that have special dosing based on overweight/obesity that is followed by many institutions.

Amino Acid Calculations in PN

Amino acids are the protein source in PN. Amino acids come in stock preparations of 5%, 8.5%, 10%, 15%, and others. They ALL provide *4 kcals/gram* in energy. Branded AA solutions commonly used in PN include: - *Aminosyn* - *FreAmine* - *Travasol* - *TrophAmine* - *Clinisol* - And others

Aminophylline and Theophylline

Aminophylline and Theophylline are narrow therapeutic index drugs. They are dosed based on *IBW* in ALL patients for safety. *Conversions between Aminophylline and Theophylline must be known*. The conversion between the two is shortened to *ATM*. - Aminophylline to Theophylline: Multiply by 0.8 - Theophylline to Aminophylline: Divide by 0.8 This is because Aminophylline is a salt form of theophylline. 100 mg of aminophylline is 80mg of theophylline.

Acids and Bases

An acid is a compound that dissociates, *releasing/donating protons (H+) into the solution*. Once the proton is released, the compound is now a conjugate base, or its salt form. - For example, HCl in solution is an acid and dissociates into H+ and Cl-. A base is a compound that *picks up or binds a proton*. - For example, NH3 is a base that can pick up a proton and become NH4+.

Acid-Base Disorders

An acid-base disorder that leads to a *pH of < 7.35* is called an *acidosis*. If the disorder leads to a *pH of > 7.45*, it is called an *alkalosis*. These disorders are further classified as either *metabolic or respiratory* in origin. The primary disturbance in a *metabolic* acid-base disorder is the *plasma HCO3 concentration*. Metabolic acidosis is characterized by a decrease in the plasma HCO3 concentration, whereas metabolic alkalosis is characterized by an increase in plasma HCO3 concentration. - Metabolic acidosis may be associated with an increase in the anion gap as well. The primary disturbance in a *respiratory* acid-base disturbance is the *pCO2*. Respiratory acidosis is characterized by an elevation of the pCO2, whereas respiratory alkalosis is characterized by a decrease in the pCO2. Each disturbance will cause the body to *compensate* or have a *compensatory response* that attempts to correct the imbalance toward normal and keep the pH neutral.

Re-feeding Syndrome

An intracellular loss of electrolytes, particularly phosphate, which can cause serious complications during PN.

Anion Gap

Anion Gap, or the difference between the measured *cations and the anions* in the blood, is an important measurement in *metabolic acidosis*. When a patient is experiencing a metabolic acidosis, it is common to calculate the Anion Gap, as this result will assist in determining the cause of the acidosis. A mnemonic to remember for causes of gapped metabolic acidosis is *CUTE DIMPLES* (Cyanide, Uremia, Toluene, Ethanol [alcoholic ketoacidosis], Diabetic ketoacidosis, Isoniazid, Methanol, Propylene Glycol, Lactic Acidosis, Salicylates). The anion gap is considered high if it is *> 12 mEq/L*. This means the patient has a gap acidosis. The anion gap can be low, which is much less common. A non-gapped acidosis is caused by other factors, mainly *hyperchloremic acidosis*. Anion gap is calculated using the values rom the Basic Metabolic Panel, a venous sample: - Anion Gap = Na - (Cl + HCO3)

E Value- Overview

As mentioned earlier, *body fluids are isotonic*, having an *osmotic pressure equivalent to 0.9% NaCl*. When making a medication to place into a body fluid, the *drug provides solutes* to the solvent and needs to be accounted for in the prescription in order to avoid making the prescription *hypertonic or hypotonic*. The relationship between the amount of drug that produces a particular osmolarity and the amount of NaCl that produces the same osmolarity is called the *sodium chloride equivalent* or the *E-Value* for short.

Calculating BMI

BMI is calculated as follows: - BMI (kg/m2) = weight (kg) / height (m) x height (m) Alternatively, BMI can be calculated with weight in pounds and height in inches using a conversion factor to convert to units of kg/m2: - BMI (kg/m2) = [weight (pounds) / height (in) x height (in)] x 703

Protein-Sparing Nutritional Technique

Because critically ill patients are catabolic, meaning their protein breakdown occurs faster than their protein synthesis, many clinicians prefer to use "protein sparing" techniques in this population. This means that most or all of the TEE calories are provided by dextrose and fat. If adequate calories are provided this way, the body will *"spare"* the protein and use it for muscle and protein synthesis. However, the protein calories may not all totally end up in the intended locations. If "protein sparing" is used, the energy required by the patient will come from only dextrose and lipids, which are the *"non-protein calories" (NPC)*. Overall, whether to include the protein calories in the total calories provided by a PN regimen remains controversial.

Insulin in PNs

Because of the large carbohydrate component in PNs, insulin may be required (even in patients WITHOUT diabetes). Insulin is typically added as *regular insulin* to safely control blood glucose, and it is added as half the previous day's sliding scale requirement or less. This insulin can be supplemented with SC injections of insulin, if needed. PN formulas are often titrated on and off (e.g. started at less than the goal rate and not abruptly stopped) to facilitate physiologic glucose regulation.

Buffer Systems

Buffer systems in the body help to reduce the impact of too few or too many hydrogen ions in body fluids. These hydrogen ions could cause harm, including degrading some drugs, destabilizing proteins, inhibiting cellular functions, and with too much of a change outside the narrow range, cells die and death can occur. Therefore, buffers minimize fluctuations in pH so that harm is avoided. Buffer systems are common in the body and are composed of either a weak acid and salt of the acid (its conjugate base, such as acetic acid and sodium acetate), or weak base and salt of the base (its conjugate acid, such as ammonium hydroxide and ammonium chloride).

Corrected Calcium Equation

Ca Corrected (mg/dL) = Reported Serum Calcium (mg/dL) + {[4.0 - serum albumin (g/dL)] x [0.8]} This equation provides an estimate of what the patient's serum calcium would be if the albumin was normal.

Calcium in PN

Calcium is important for many functions, including cardiac conduction, muscle contraction, and bone homeostasis. The normal serum calcium concentration is *8.5 to 10.5 mg/dL*. However, almost half of serum calcium is bound to albumin. *Low albumin* will lead to a *falsely low serum calcium concentration*. If albumin is low, considered <3.5 grams/dL, the calcium level must be corrected using the Corrected Calcium equation prior to addition of calcium in the PN or when providing calcium replacement in any manner.

Calories Provided from Macronutrients in PN

Carbohydrate - Dextrose Monohydrate: 3.4 kcals/gram - Glycerol/Glycerin: 4.3 kcals/gram (these may be used to decrease hyperglycemia. However, most commonly the dextrose load will be decreased or the insulin dose will be increased) Fats - Injectable Lipid Emulsion 10%: 1.1 kcals/mL - Injectable Lipid Emulsion 20%: 2 kcals/mL - Injectable Lipid Emulsion 30%: 3 kcals/mL Protein - Amino Acid Solutions (Aminosyn, FreAmine, others): 4 kcals/gram

Fahrenheit to Celsius Conversion

Celsius = (F-32)/1.8 Fahrenheit = (C x 1.8) + 32

Weight Used in the CrCl Calculation

Compare ABW to IBW: 1. If underweight (ABW < IBW) - Use TBW 2. If normal weight (ABW about equal to IBW) - Use IBW 3. If overweight/obese - *BMI <25: Use IBW* - *BMI 25 or more: Use AdjBW*

Choosing the Correct Weight for Dosing Algorithm

Compare ABW to IBW: 1. If underweight (ABW < IBW): - Use TBW for ALL medications 2. If normal weight (ABW is about equal to IBW OR ABW is <120% of IBW) - Use ABW for MOST medications. - Use IBW for *Aminophylline, Theophylline, Acyclovir, and Levothyroxine*. 3. If obese (ABW 120% or more of IBW) - Use IBW for *Aminophylline, Theophylline, Acyclovir, and Levothyroxine* - Use TBW for *LMWH, UFH and Vancomycin* - Use AdjBW for *Aminoglycosides* HOWEVER, if a question on NAPLEX specifies what weight to use, even if different than above, USE THAT WEIGHT. Aminoglycosides are dosed based on ABW or IBW unless the patient is obese, then it AdjBW is used.

Renal Function and CrCl Estimation

Creatinine is a break-down product produced when muscle tissue makes energy. The normal range for SCr is about *0.6 to 1.3 mg/dL*. If kidney function declines and creatinine cannot be excreted (cleared), *the creatinine level will increase in the blood and the creatinine clearance (CrCl) will decrease*. This tells us that the concentration of drugs that are renally cleared will also increase and a dose reduction may be required. Sometimes the SCr can appear normal even when renal function is compromised (e.g. in the elderly). Sometimes SCr will increase because of a drug (some drugs will inhibit tubular secretion of creatinine, increasing the SCr), or it can be elevated d/t dehydration. Before changing doses or evaluating for other causes of SCr elevation, it is important to assess for dehydration and correct it if present. The main way CrCl and renal function is assessed is through the use of the *Cockcroft-Gault Equation*.

Steroid Conversions

Cute Hot Pharmacists and Physicians Marry Together and Deliver Babies - Cortisone = 25mg - Hydrocortisone = 20mg - Prednisone = 5mg - Prednisolone = 5mg - Methylprednisolone = 4mg - Triamcinolone = 4mg - Dexamethasone = 0.75mg - Betamethasone = 0.6mg

Dehydration

Dehydration is a serious condition where the body does not have enough fluid. Dehydration should be assessed when the SCr is elevated before considering other reasons, as this is the easiest thing to correct. Dehydration can cause both the *SCr and Blood Urea Nitrogen (BUN) to increase*. A *BUN:SCr ratio of >20 to 1 indicates dehydration*. Correcting the dehydration will reduce both BUN and SCr, and can prevent or treat acute renal failure. Signs of dehydration should also be assessed and can include: - Decreased urine output - Tachycardia - Tachypnea - Dry skin/mouth/mucous membranes - Skin tenting (skin does not bounce back when pinched into a fold) - Fever (possibly) Dehydration is usually caused by diarrhea, vomiting, and/or an inadequate fluid intake.

Percentage Strength

Drug concentrations can be expressed in many ways, but there are a ratio of the amount of an ingredient to the total amount of product. A percent is the number of parts in *100*. Percents are often written as decimals or fractions, such as 0.25 or 25/100. The type of percentage concentrations are as follows: 1. Percent weight-in-volume (% w/v), which is expressed in *g/100mL*. This is a solid mixed into a liquid. This % concentration also applies to common IV fluids. 2. Percent volume-in-volume (% v/v), which is expressed as *mL/100mL*. This is a liquid mixed in a liquid. 3. Percent weight-in-weight (% w/w), which is expressed as *g/100g*. This is a solid mixed into a solid.

Expressing Drug Concentrations

Drugs can be expressed in solution in different ways: - Milliosmoles refers to the number of particles in solution - Millimoles refers to the molecular weight - Milliequivalents represents the amount, in mg, of a solute equal to 1/1,000 of its gram equivalent weight, taking into account the valence of the ions.

Measuring Drugs

Drugs can be measured in different ways: - As weights, using grams (g), milligrams (mg), micrograms (mcg), and nanograms (ng). - A liquid volumes, using liters (L), or milliliters (mL) - As percentage strengths (grams in 100mL, grams in 100g, or mL in 100mL) - As concentrations of a given amount of a drug in a given volume of liquid (mcg/mL, mg/L). Very small amounts of measured in ng/mL. BUN and SCr are measured in mg/dL (1 liter is 10 dL, so 1 dL is 100mL or 0.1 Liters). - As concentrations using milliequivalents (mEq) per Liter (mEq/L).

E-Value Formula and Explanation

E = [(58.5) X i] / [MW of drug x 1.8] - The E Value formula takes into account the molecular weight of 58.5 and the *dissociation factor of 1.8 d/t NS being around 80% ionized*. 0.8 is added for each additional ion beyond 1 into which the drug dissociates. The compound is compared to NaCl because NaCl is the major determinant of the isotonicity of body fluid.

Electrolytes in PN

Electrolytes in PN must be individualized to the patient's needs. The electrolytes that are typically added to PNs are: - Sodium - Potassium - Phosphate - Chloride - Calcium More or less of an electrolyte may be needed based on the patient's condition (e.g. renal disease).

Enteral Nutrition

Enteral Nutrition is the provision of nutrients via the gastrointestinal tract (GI tract). Sometimes this is achieved through a feeding tube, often called a tube feeding. *Nasogastric tubes (NG tubes) are often used*, primarily for short-term administration. For longer-term use, or if the stomach cannot be used, tubes are placed farther down the GI tract. EN is the preferred route for patients who cannot meet their nutritional needs through voluntary oral intake. Tube feedings can range from providing adjunctive support to providing complete support. Examples of EN formulas include: - *Ensure* - *Osmolite* - *Jevity* - *Glucerna* - *Novasource* - and many others. Some of these are specialized for certain types of patients (e.g. Nepro is a renal formula, Glucerna is for diabetics), and some can be purchased OTC for meal replacement or those needing additional calories.

Fats in EN/PN

Fats, or lipids, are used by the body for energy or for various critical functions, including being an essential component of cell membranes, a solvent for fat-soluble vitamins, hormone production and activity, cell signaling, and other functions. In food or EN formulas, fat is provided as 4 types: - Saturated Fats - Trans Fats - Monounsaturated Fats - Polyunsaturated Fats Each of these provide *9 kcals/gram*. In PN however, fats are provided as *injectable lipid emulsions (ILE)*. Lipids in PN are not measured in grams, but in kcals/mL instead due to the caloric contribution provided by the egg phospholipid and glycerol components in the ILE. There are three types of ILE formulas: - *10% ILE*, which provides *1.1 kcals/mL* - *20% ILE*, which provides *2 kcals/mL* - *30% ILE*, which provides *3 kcals/mL* When determining total amount of fats for the patient, it is important to take into account vehicles for drug delivery. Some medications are formulated in a lipid emulsion (*propofol* and *clevidipine*), and this *provides fat calories to the patient*. If the patient is receiving PN along with one or both of these medications, the calorie contribution from the medication must be considered.

Iron Conversion

Ferrous Sulfate is 20% elemental iron. - So 325mg Ferrous Sulfate is 65mg elemental iron. - Ferrous Gluconate = 12% Elemental Iron - Ferrous Sulfate = 20% - Ferrous Sulfate, Dried (Slo-Fe, Slow Iron) = 30% (50 mg Elemental iron in 160 mg tablet) - Ferrous Fumarate = 33% - Carbonyl Iron, Polysaccharide Iron Complex, Ferric Maltol = 100%

Determining Fluid Needs

Fluid requirements are determined *first* when designing a PN regimen. Enough, but not too much, fluid needs to be given to maintain adequate hydration. Daily fluid needs can be calculated using the following formula: - When weight >20 kg: 1500 mL + 20 mL(weight in kg - 20) --- Total body weight is used for most PN calculations, unless specifically mentioned. Some institutions estimate adult fluid requirements using a general guideline of 30-40 mL/kg/day. The PN and fluid volume should be tailored to the patient. If the patient has problems with fluid accumulation, such as HF or renal dysfunction, the amount of fluid provided should be reduced. Fluid volume from medications, including IV piggybacks, should be included in the calculation of the overall volume the patient is receiving.

Carbohydrates in PN/EN

Glucose is the *primary energy source*. Unless a patient purchases glucose tablets and gel, however, carbohydrates are consumed as simple sugars, such as fruit juice, or as complex, "starchy" sugars, such as legumes and grains. These sugars are hydrolyzed in the intestine into the monosaccharides fructose, galactose, and glucose, which are absorbed. The liver then converts the first two into glucose, and the excess glucose is stored as glycogen. *Carbohydrates from food or in EN formulas provide 4 kcals/gram*. In PN, *dextrose monohydrate* provides the carbohydrate source, which is the isomer of glucose (D-glucose) which can be metabolized for energy. The *dextrose in PN provides 3.4 kcals/gram*. Occasionally, glycerol is used as an alternative to dextrose in patients with impaired insulin secretion. Glycerol provides 4.3 kcals/gram and comes pre-mixed with amino acids.

Flow Rates

IV infusions are commonly used to deliver medications in different settings, including hospitals. Flow rates are used to specify the volume or amount of drug a patient will receive over a given period of time. An order can specify the flow rate in many different ways. Some examples include: - *Milliliters per hour* - *Milligrams per hour* - *mcg/kg/min* - The total time to administer the entire volume of infusion (e.g. give over 8 hours). Sometimes flow rates are expressed as *drops/min*, which is important in only certain medications. Flow rates depend on the *dose* of the medication and the *concentration* available.

Levothyroxine Conversion and Tablet Colors

IV to PO for Levothyroxine is 0.75 to 1, so 0.75 mcg IV levothyroxine is 1mcg PO levothyroxine. Orangutans Will Vomit On You Right Before They Become Large, Proud Giants. - Orange (25 mcg) - White (50 mcg) - Violet (75 mcg) - Olive (88 mcg) - Yellow (100 mcg) - Rose (112 mcg) - Brown (125 mcg) - Turquoise (137 mcg) - Blue (150 mcg) - Lilac (175 mcg) - Pink (200 mcg) - Green (300 mcg)

Metoprolol Conversions

IV to PO is 1 to 2.5, so 1mg IV is 2.5mg PO

Drop Factor

IV tubing is set to deliver a certain number of drops per minute (gtts/min). There are various types of IV tubing and each as a hollow plastic chamber called a drip chamber. The number of drops per minute can be counted by looking at the drip chamber. It is important to know how big the drops are to calibrate the tubing in terms of drops/mL. This is called the *drop factor*. Calculating flow rates from a drop factor is not as common with the prevalence of programmable "smart" pumps, but is it a good skill to know for situations when a programmable pump is not available, fails, or as a double-check.

Converting KCl Liquid and Tablets

If asked to convert KCl liquids to tablets or vice versa, use a simple proportion since *KCl 10% = 20 mEq/15mL*.

Henderson-Hasselbalch Equation

If the compound is a weak acid: - *pH = pKa + log [salt/acid]* If the compound is a weak base: - *pH = (pKw {usually 14} - pKb) + log [base/salt]* - *pH = pKa + log [base/salt]*

0% and 100% Purity

If the prescription calls for an ingredient that is *pure*, the concentration is 100%. A diluent, such as petrolatum, lanolin, alcohol, ointment base, inert base, lactose, or Aquafor, does not contain any drug, so the concentration of the diluent is 0%.

Milliequivalents

Milliequivalents represents the amount, in mg, of a solute equal to 1/1,000 of its gram equivalent weight, taking into account the valence of the ions. Like osmolarity, the quantity of particles is important, but so is the electrical charge. Milliequivalents refers to the *chemical activity* of an electrolyte and is related to the total number of ionic charges in solution and considers the valence, or charge, of each ion. - mEq = (mg x valence) / MW - mEq = mmols x valence

Shortcut for Ratio Strength Calculations

Most multi-step calculations will require converting ratio strength to percentage strength. If a ratio strength is presented in a problem, convert it to a percentage strength and convert it back if needed. 1. Ratio strength to percentage strength: 100/ratio strength = % strength 2. Percentage strength to ratio strength: 100/% strength = ratio strength

Other Additives in PNs

Multivitamins and trace elements are usually added to the PN formula. Insulin and H2RAs are also occasionally added as well. Adding any other IV medications to the PN is generally discouraged, because the entire PN would be wasted if a medication was discontinued or changed during the day.

Compounding PN Admixtures

PN admixtures are considered *Compounded Sterile Products (CSPs)*. Therefore, the preparation MUST comply with the *USP Chapter <797>* requirements. PN admixtures are also classified as high-alert medications by the Institute for Safe Medication Practices (ISMP). Many large hospitals use automated compounding devices to combine the ingredients into a single container, but *multi-chamber bags* can be purchased for convenience. Two-chamber premixed PNs have amino acid solution in one chamber and a dextrose solution in another chamber. The seal between the chambers is broken before administration to mix the solutions together. Three-chamber options (with lipids in the 3rd chamber) are also available. *Clinimix* is one of the commonly used multi-chamber products. *Clinimix-E* products contain electrolytes. Each patient's fluid, kcals, protein, and lipid requirements, plus the initial electrolyte, vitamin, and trace element requirements will be determined. PN requires careful monitoring, including assessing the degree of glucose intolerance and the risk of refeeding syndrome.

Parts Per Million/Billion and Shortcuts

PPM and PPB are used to express the strength of very dilute solutions. They are defined as the number of *parts of the drug per 1 million (or 1 billion) parts of the whole*. The same designations are used as for percentage strength (% w/w, %w/v, % v/v). The shortcuts for PPM and PPB and converting to percentage strength and back are as follows: - If PPM to % strength: Move the decimal *to the left 4 places* - If % strength to PPM: Move the decimal *to the right 4 places* If the question asks to express something in PPB, divide by 1,000,000,000 (9 zeros).

Parenteral Nutrition- Overview

Parenteral Nutrition, or PN, is delivering nutrition via the vein. When feeding a patient, it is preferable to use the *least invasive and most physiologic* method. PN is neither, and has a high risk of complications, including infection and thrombosis. It may be indicated when the patient is not able to absorb adequate nutrition via the GI tract for *>5 days*. Conditions that often require PN include bowel obstruction, ileus, severe diarrhea, radiation enteritis, and untreatable malabsorption. If a PN is expected to be used short-term (<1 week), peripheral administration may be possible, but has a high risk of phlebitis (inflammation of the vein) and vein damage. Central line placement allows for a higher osmolarity and a wider variation in pH. Common types of central lines include *peripherally-inserted central catheters (PICC lines)*, Hickman, Broviac, Groshong, and others.

Statin Conversions

Pharmacists Rock At Saving Lives and Preventing Fatty-Deposits - Pitavastatin = 2mg - Rosuvastatin = 5mg - Atorvastatin = 10mg - Simvastatin = 20mg - Lovastatin = 40mg - Pravastatin = 40mg - Fluvastatin = 80mg

Calcium and Phosphate Solubility

Phosphate and Calcium can be dangerous when added to PNs, as they can *bind together and precipitate*, which can cause a *pulmonary embolus, which can be fatal*. The following steps can help reduce the risk of a calcium-phosphate precipitate: - *Choose calcium gluconate* over calcium chloride for calcium replacement in PNs. Ca Gluconate is less reactive and has a *lower risk of precipitation with phosphates*. Ca Gluconate has a lower dissociation constant compared to CaCl2, leaving less free calcium available in solution to bind to phosphate. - *Add phosphate FIRST* (after adding the dextrose and amino acids), followed by the other PN components. Next, agitate the solution, then *add calcium near or at the end* to take advantage of the maximum volume of the PN solution. - The MAX calcium and phosphate ADDED TOGETHER (units must be the same to do this) should NOT exceed *45 mEq/L*. Meaning no more than 45 mEq of Ca and PO4 total should be in the bag. - Maintain a proper pH. pH of the PN should be lower, as there is less risk of precipitation of Ca and PO4 in acidic environments. Refrigerate the bag once fully prepared. When temperature increases, more Ca and PO4 dissociate in solution and precipitation risk increases.

Phosphate in PN

Phosphorus, or Phosphate (PO4), is present in DNA, cell membranes, and ATP. It acts as an acid-base buffer and is vital in bone metabolism. Phosphate can be provided by Sodium Phosphate (NaPO4) or Potassium Phosphate (KPO4). *The two forms do not provide equivalent amounts of phosphate*. Orders for phosphate should be written in mmols of phosphate, followed by the salt form it is to be provided in (either potassium or sodium). Phosphate will often need to be reduced in renal disease.

Potassium in PN

Potassium is the principal *intracellular cation*. Potassium can be supplied using Potassium *Chloride* (KCl), Potassium *Phosphate* (KPO4), Potassium *Acetate*, or as a combination of these. The normal serum range for potassium is *3.5 to 5 mEq/L*. The amount supplied may need to be reduced in patients with renal or cardiovascular disease.

Protein in PN/EN

Protein is used to either *repair or build muscle cells* or as a source of *energy*. Protein in EN is present in various forms, and in PN as the constituent *amino acids*. Protein calories from food, enteral formulas or a parenteral amino acid solutions each provide *4 kcals/gram*. The typical protein requirement for a non-stressed, ambulatory patient is about *0.8-1 gram/kg/day*. Protein requirements increase if the patient is placed under stress, which is defined as illness severity. The more severely ill, the greater the protein requirements will be. In patients with a high degree of metabolic stress, the protein requirements can be as high as *2 grams/kg/day*. The desired weight is likely specified in the exam scenario, but some prescribers order protein based on the patient's IBW.

Nitrogen Balance and the NPC:N

Proteins contain nitrogen. When proteins are broken down during catabolism, nitrogen is released. The body packages up this nitrogen and excretes it mainly as urea in the urine. Nitrogen balance is the difference between the body's nitrogen gains and losses. While grams of protein are calculated in the nutritional plan, grams of nitrogen are used as an expression of the amount of protein received by the patient. There is *1 gram of nitrogen (N) for each 6.25 grams of protein*. This ratio is used to determine the *Non-Protein Calories to Nitrogen Ratio (NPC:N)*. This ratio is used to determine if the protein being received by the patient is adequate for their stress levels. Desirable NPC:N ratios are: - 80 to 1 for the most severely stressed patients - 100 to 1 for severely stress patients - 150 to 1 for unstressed patients Nitrogen Intake is calculated by dividing the grams of protein intake by 6.25. This gives us the grams of nitrogen the patient is consuming. Next, the NPC:N ratio is calculated by *dividing the total non-protein calories (dextrose + lipids) by the grams of nitrogen*. This value gives us the NPC:N ratio.

Dissociation Factor

Since isotonicity is related to the number of particles in the solution, the *dissociation factor* or the ionization, symbolized by the letter i, is determined for the compound. Non-ionic compounds do not dissociate and will have a dissociation factor of one. Every particle over 1 will have a dissociation factor of 1 +0.8(# of particles). This 0.8 is due to the dissociation of saline in blood, which is 80% ionized in water. Therefore every other drug is based on NS for their dissociation factor. For example, a dissociation factor of 1.8 means that 80% of the compound will dissociate in a weak solution. This compound has 2 dissociating ions.

Sodium in PN

Sodium is the principal *extracellular cation*. It is typically supplied as sodium *chloride* but may also be added in as sodium *acetate*, sodium *phosphate*, or a combination of these. The type of sodium added is based on the patient characteristics. For example, if the patient is *acidotic, sodium acetate* should be added. Sodium acetate is converted to sodium bicarbonate and may help correct the acidosis. Sodium chloride comes in many concentrations, such as 0.9% (NS), 0.45% (1/2NS), and others. NaCl 23.4% is used in PN preparation and contains *4 mEq/mL of sodium*. This is very hypertonic and is dangerous if used incorrectly. Any NaCl greater than 0.9% is hypertonic. Sodium may need to be reduced in patients with renal dysfunction or cardiovascular disease, including hypertension. Remember to take into account patient characteristics when adding sodium in as an electrolyte.

Specific Gravity

Specific Gravity is the ratio of the density of a substance to the density of water. SG can be important for calculating doses of IV medications, in compounding, and interpreting a urinalysis. *Water has a SG of 1, 1g water = 1mL water*. Substances with a SG <1 are *lighter* than water and those with a SG >1 are *heavier* than water. Essentially, specific gravity is mass of the substance over the volume it takes up, in mL. So SG is: - SG = grams of substance/mL of substance *SG is essentially equivalent to density in g/mL*. If asked for the density in the problem, the specific gravity is what they are looking for.

Determining Primary Acid-Base Disorder

Step 1: Is it acidosis or alkalosis? - Look at the blood pH. If the pH is <7.35, it is acidosis. If the pH is >7.45, it is alkalosis. Step 2: What other values are abnormal? - Respiratory: decreased CO2 = alkalosis, increased CO2 = acidosis. - Metabolic: increased HCO3 = alkalosis, decreased HCO3 = acidosis. Step 3: Which of the abnormal values in Step 2 match the pH in Step 1? - Low pH is acidosis. If CO2 is elevated, it is respiratory acidosis. If HCO3 is decreased, it is metabolic. - High pH is alkalosis. If CO2 is decreased, it is respiratory alkalosis. If HCO3 is elevated, it is metabolic alkalosis. Step 4: BUT what if both CO2 and HCO3 are abnormal?? - Usually only one of the values will match the pH, and the other will go in the opposite direction from the pH. This is called compensation. - Example: low pH, low CO2, low HCO3. Low pH indicates acidosis. Low CO2 indicates *alkalosis* and low HCO3 indicates *acidosis*. Therefore, this is *metabolic acidosis with some respiratory compensation*.

TEE Formula, Activity Factor, and Stress Factor

TEE = BEE x Activity Factor x Stress Factor The activity factor is either 1.2 if confined to bed (non-ambulatory) or 1.3 if out of bed (ambulatory). Commonly used stress factors are: - Minor Surgery: 1.2 - Infection: 1.4 - Major Trauma, sepsis, burns up to 30% BSA: 1.5 - Burns over 30% BSA: 1.5-2

Calculating the ANC

The ANC is calculated by multiplying the WBC (in total cells/mm3) by the percentage of neutrophils (the segments PLUS the bands), and divide by 100. Neutrophils can be labeled as Polymorphonuclear cells (PMNs or Polys) or Segmented Neutrophils (Segs) on a lab report. They are both neutrophils and should be added together to get the % TOTAL NEUTROPHILS. *ANC (cells/mm3) = WBC x [(% segs + % bands)/100]*

ANC and Neutropenia- Overview

The Absolute Neutrophil Count, or ANC. This calculation is useful to determine the patient's immune function. Neutrophils are our body's main defense against infection. The lower a patient's neutrophil count, the more susceptible that patient is to infection. Some drugs, like Clozapine, can severely decrease neutrophils, leading to serious immunodeficiency. The Clozapine REMS program is designed to reduce the risk of Clozapine-related neutropenia. Clozapine CANNOT be refilled is the patient's ANC is <1,000 cells/mm3. A neutropenic patient should be monitored for signs of infection, including fever, shaking, general weakness, or flu-like symptoms. Precautions to reduce infection risk, such as proper hand-washing and avoiding others with infection, should be followed.

Percent of Drug Ionization in a Solution

The HHE can be modified to calculate the % ionization of a drug. Since the pH is a measurement of the hydrogen ions (protons) in the solution, the % ionization is the percentage of the drug in the solution that has deprotonated. To calculate % ionization of a weak acid: - *% ionization = 100 / [1 + 10^(pKa-pH)]* To calculate the % ionization of a weak base: - *% ionization = 100 / [1 + 10^(pH-pKa)]*

Acid-Base Disorder Physiology

The acid-base status of the patient can be determined with an arterial blood gas measurement (ABG). The primary buffering system of the body is the *bicarbonate/carbonic acid system*. The kidneys help to maintain a neutral pH by controlling bicarbonate (HCO3) reabsorption and elimination. *Bicarbonate* acts as both a buffer and a base. The lungs help to maintain a neutral pH by controlling carbonic acid, which is *directly proportional* to the partial pressure of carbon dioxide, or pCO2. *Carbon dioxide* acts as both a buffer and an acid. Alterations from the normal values leads to acid-base disorders. Diet and cellular metabolism lead to a large production of protons (H+) that need to be excreted to maintain acid-base balance. The ABG is typically presented this way in a written chart note: *ABG: pH/pCO2/pO2/HCO3/O2 Sat*

Ratio Strength

The concentration of a weak solution can be expressed as a ratio strength. It is denoted as *one unit of solute* contained *in the total amount* of the solution or mixture (e.g. 1:500). Ratio strength is another way of presenting a percentage strength. This makes sense because percentages are ratios of parts per 100. However, in clinical practice, ratio strengths have been associated with medication errors. The FDA now requires removal of ratio strengths from the labeling of injectable drug products with only 1 active ingredient (e.g. epinephrine, isoproterenol). Ratio strength is still commonly used in compounding.

pH and Physiology

The pH refers to the overall acidity or basicity of the solution. As a solution becomes more acidic (the concentration of protons increase), the *pH decreases*. Conversely, when the *pH increases, proton concentration is decreasing, and the solution is more basic or alkaline*. Pure water is neutral, and has a pH of 7. Blood is slightly alkaline, with a pH of 7.4. Stomach acid has a pH of about 2, and is therefore very acidic, with many protons in solution. If the pH of the blood is too acidic or too basic, an acid-base disorder develops.

Importance of pKa Rules

The percentage of drug in the ionized/un-ionized form is important because *ionized drugs are soluble in water, but cannot easily cross lipid membranes*. An un-ionized drug is not soluble in water, but can cross the membranes and reach the proper receptor site. *Most drugs are weak acids* meaning they are soluble and can pick up a proton to cross the lipid bi-layer. The degree of ionization depends on the dissociation constant, Ka, of the drug and the pH of the environment. This leads to the *Henderson-Hasselbalch Equation*, AKA the buffer equation, which is used *to solve for the pH*.

Administration of ILE in PNs

The standard distribution of non-protein calories is 70-85% carbohydrate (dextrose) and 15-30% fat (lipids, or ILE). Lipids are available as 10%, 20%, and 30% emulsions, with brand names Intralipid (all concentrations) and Smolipid (20% only). Smolipid contains 4 oils, while traditional ILE contains only soybean oil, so these two *are not interchangeable*. ISMP has reported numerous reports of mix-ups between these two formulations. Lipids do not need to be given daily. If triglycerides are high, lipids may be given 3 times a week or even just once weekly. If lipids are given once weekly, divide the total calories by 7 to determine the daily amount of fat the patient receives. Due to the risk of infection, the recommended hang time limit for ILE is *12 hours when infused alone*. However, an admixture containing fat emulsion, such as a TNA, may be administered over *24 hours*. *PN requires a filter itself due to the risk of a precipitate*. However, lipid emulsions cannot be filtered through 0.22 micron filters, so *1.2 micron filters* are commonly used for lipids.

Trace Elements in PN

The standard mix of trace elements used in PN includes: - Copper - Zinc - Chromium - Manganese - Selenium (sometimes) Manganese and copper should be *withheld* in patients with *severe liver disease*. Chromium, molybdenum, and selenium should be *withheld* in *severe renal disease*. *Iron is not routinely given in a PN*.

Determining Caloric Needs

The total caloric need for the patient is the next step to creating a PN regimen. This is calculated using the *Basal Energy Expenditure (BEE)* and the *Total Energy Expenditure (TEE/TDE)*. The BEE, otherwise referred to as the Basal Metabolic Rate (BMR), is the energy expenditure in the *resting state*, exclusive of eating and activity. It is the minimum amount of energy needed to just exist. It is *estimated differently in males and female adults using the Harris-Benedict Equations*. These are not memorized. The BEE *can be estimated using 15-25 kcals/kg/day*. The TEE, or the Total Daily Expenditure (TDE) *is a measure of the BEE PLUS excess metabolic demands* as a result of stress, the thermal effects of feeding, and energy expenditure for activity. Once the BEE is calculated, the TEE is calculated by taking the BEE calories and multiplying by the appropriate *activity factor and stress factor*. Energy requirements are increased by 12% with each degree of fever over 37 degrees Celsius.

Osmolarity

The total number of particles in a given solution is directly proportional to its osmotic pressure. The particles are usually measured in milliosmoles. Osmolarity is the measure of total number of particles, or solutes, per liter of solution, defined as osmoles/liter (Osmol/L), or more commonly milliosmoles/liter (mOsmol/L). Solutions can either be *ionic*, such as NaCl, which dissociates into two solutions in solution Na and Cl, or *non-ionic*, which does NOT dissociate (such as glucose or urea). Since the volume of water changes according to temperature, the term osmolality is used in clinical practice (mOsmol/kg). It is independent of temperature. When solute concentrations are very low, osmolarity and osmolality are similar. Milliosmole calculation problems differ from osmolarity calculations in that *osmolarity will always need to be normalized to a volume of 1 liter*. When doing these calculations, the dissociation particles need to be known for the exam.

Carbohydrate Calculations in PN

The usual distribution of non-protein calories is 70-85% carbohydrate (dextrose) and 15-30% fat (lipids). Dextrose comes in concentrations of 5%, 10%, 20%, 30%, 50%, 70% and others. The higher concentrations are used for PN. When calculating dextrose in PN formulas, *do not exceed 4 mg/kg/min*. Some use 7 grams/kg/day. These are the conservative estimates of the maximum amount of dextrose that the liver can handle.

Valence of a Compound

The valence is the charge of an ion. To count the valence, divide the compound into its positive and negative components, and then count the number of *either the positive or the negative charges*. For a given compound, the mEqs of cations (positive charges) anions (negative charges). The NAPLEX exam requires the valence be known for certain compounds. It is important to remember that the *divalent* cations (Ca, Mg, Iron) have a LOT of *chelation DDIs* with other drugs.

Multivitamins in PN

There are 4 fat-soluble vitamins (A, D, E, and K) and 9 water-soluble vitamins (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid, cyanocobalamin, and ascorbic acid OR vitamins B1, B2, B3, B5, B6, B7, B9, B12 and vitamin C, respectively) in the standard MVI-13 mixture. The MVI-12 mixture does NOT contain vitamin K since certain patients may need more or less of this vitamin. If patients are taking warfarin, the INR must be monitored.

Advantages and Disadvantages of EN

There are several advantages of EN over PN, making EN the preferred way to feed a patient if they are unable to meet their nutritional needs through voluntary oral intake. 1. *Lower cost* 2. *Uses the GI tract, which prevent atrophy* and other problems 3. *Lower risk of complications* (e.g. less infections, hyperglycemia, reduced risk of cholelithiasis and cholestasis) However, there are some risks. The most common risk associated with enteral feeding is *aspiration pneumonia*. Enteral feedings can also cause drug interactions. The general rule for preventing drug-enteral feeding interactions is to *hold the feedings one hour before or two hours after the drug is administered*. Some drugs require further separation. Another issue is that tube feeds do not provide enough water for the patient. Water needs to be given in addition to the tube feeds. If fluid intake is inadequate, it the feeding will be uncomfortable for the patient, and place them at risk for complications, including hypernatremia.

Body Weight in Medication Dosing

There are three potential measures of body weight for a patient when it comes to medication dosing: - Actual/Total Body Weight (ABW or TBW) - Ideal Body Weight (IBW) - Adjusted Body Weight (AdjBW) In pharmacy, weights are used to calculate drug doses, flow rates, creatinine clearance, and more. The weight that should be used for each type of calculation (in an individual patient) is not always the same.

Types of Parenteral Nutrition

There are two types of PN admixtures, *2-in-1 and 3-in-1 formulations*. Both types contain sterile water for injection, electrolytes, vitamins, and minerals. 2-in-1 Formulations contain *two macronutrients (dextrose and amino acids)* in one container. Lipids are infused separately, if needed. 3-in-1 Formulations contain *three macronutrients (dextrose, amino acids, and lipids)* in one container. 3-in-1 Formulations are also called Total Nutrient Admixtures (TNAs) or "All-in-One" Formulations.

Loop Diuretics Conversion

These are all equivalent doses: - Ethacrynic Acid: 50mg - Furosemide: 40mg - Torsemide: 20mg - Bumetanide: 1mg IV to PO ratios: - Furosemide: IV to PO is 1 to 2, so 20mg IV is 40mg PO - Other loops: IV to PO is 1 to 1.

Friedewald Equation

This equation is used to calculate total LDL for the patient: - LDL = TC - HDL - [TG/5] Do not use when TG is > 400.

Q1C1 Calculations

This formula can be used to change the strength of the quantity. Q1C1 is used specifically when the problem deals with *two concentrations*. Be careful, as *the units on each side must match*, and one or more may need to be changed, such as mg to grams, or vice-versa. Q1 x C1 = Q2 x C2, where Q1 is the old quantity, C1 is the old concentration, and C2 is the new concentration and Q2 is the new quantity.

Cockcroft-Gault Equation

This formula is used to estimate renal function in patients. It is fairly accurate, but is *not reliable* in *very young children, those with ESRD, or when renal function is fluctuating rapidly*. This is why it is important to assess for dehydration, as CrCl will be falsely decreased and inaccurate in that setting. In these settings, there are different methods used to estimate renal function. The equation *must be known* as it is used commonly in practice: - CrCl (mL/min) = ([140 - age of patient] / [72 x SCr]) x weight in kg (x 0.85 if female) Use age in years, weight in kg, and SCr in mg/dL. Weight can be tricky when calculating the CrCl, as those who are obese will have a false answer if their ABW is used. The weight is chosen based on an algorithm. Once CrCl is calculated, it is used to renally adjust ALL necessary medications, unless SCr changes. The proper weight used in the CGE *will not always be the same* weight used to calculate weight-based dose of medications.

Time to Burn Equation

Time to Burn (with sunscreen in minutes): TTB = SPF x TTB (without sunscreen)

Important Compounds and their Valence

Valence of 1: - Ammonium Chloride (NH4Cl) - Potassium Chloride (KCl) - Potassium Gluconate (KC6H21O2) - Sodium Acetate (NaC2H3O3) - Sodium Bicarbonate (NaHCO3) - Sodium Chloride (NaCl) Valence of 2: - Calcium Carbonate (CaCO3) - Calcium Chloride (CaCl2) - Ferrous Sulfate (FeSO4) - Lithium Carbonate (Li2CO3) - Magnesium Sulfate (MgSO4)

Common Solid Weight, Height, and Other Conversions

Weight - 1 kg = 2.2 pounds - 1 oz = 28.4 grams - 1 pound = 454 grams - 1 grain (gr) = ~65 mg, 64.8 mg (actual) Height - 1 inch (in) = 2.54 centimeters (cm) - 1 meter (m) = 100 cm Other: Milliequivalents and Millimoles - K, Na, and other MONOvalent ions: 1 mEq = 1 mmol - Ca, Mg, and other DIvalent ions: 1 mEq = 0.5 mmol If mEq are provided for potassium, and the answer requires mmols, use the same numbers. When mEq is provided for calcium, and the answer requires mmols, use half the mEq number.

Parenteral and Enteral Nutrition

When a patient cannot eat enough to stay healthy, nutrition support may be required. Examples include patients with coma, stroke, cancer, and GI disorders (such as bowel obstruction, Crohn's Disease, ulcerative colitis). *Enteral Nutrition uses the GI tract* to deliver all or part of a patient's caloric needs (e.g. eating food orally or delivering a formula via a "feeding tube" into the stomach or intestine). *Parenteral Nutrition delivers calories into a vein* through a central or peripheral line. When the GI tract is working, *EN is preferred* as it is the most physiologic, has *fewer complications*, and is generally less expensive. PN can be used for patients whose GI tract is not functioning, who cannot/will not eat, or who cannot maintain nutritional status enterally.

Waist Circumference

When assessing overweight/obesity, BMI is used concurrently with *Waist Circumference*. If most of the fat is around the waist, there is a higher disease risk. High risk is defined as a waist size of >35 inches in women and >40 inches in men. Underweight can be a problem as well if the person is fighting a disease such as a frail, hospitalized patient with an infection.

Isotonicity

When discussing osmotic pressure gradients between fluids, the term tonicity is used. Solutions can be isotonic (osmolarity is the same as the blood, which is about 300 mOsmol/L, hypotonic or hypertonic. When solutions are prepared, they need *to match the tonicity of the body fluid* as closely as possible. If the osmolarity of the solution is higher than the body fluid in one cellular compartment, it will cause water to move from the lower to higher concentration of solutes. If a PN solution is injected with a higher osmolarity than the blood, fluid will flow into the vein, resulting in edema, inflammation, phlebitis, and possible thrombosis. Isotonicity is *desired when preparing eye drops and nasal solutions*.

Osmolarity Equation

[weight of substance in *g/L* / MW (*g/mole*)] X # of dissociation particles X 1,000