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Calculations

Terms in this set (110)

Tsp
5 ml
Tbsp
15 ml
1 fl oz
30 ml
29.57 ml
1 cup
8 oz
240 ml
236.56 ml
1 pint
16 oz
480 ml
473 ml
1 quart
2 pints
960 ml
946 ml
1 gallon
4 quarts
3840 ml
3785 ml
1 kg
2.2 lbs
1 oz
28.4 g
1 lb
454 g
1 grain (gr)
65 mg
64.8 mg
inch
2.54 cm
meter
100 m
K+, Na+, other monovalent ions
1 mEq = 1 mmol
Ca++, other divalent ions
1 mEq = 0.5 mmol
kg, g, mg....?
mcg, ng, pg
aminophylline to theophylline
aminophylline x 0.8 = theophylline
theophylline to aminophylline
theophylline / 0.8 = aminophylline
Specific gravity units
g/ml
Like density
Parts per million units
same as for %w/w, %w/v and %v/v
g/g, g/ml, ml/ml
Ratio
1:x
BMI units
kg/m^2
BMI conversion factof from lb/in2 to kg/m2
lbs/in2 x 703
Underweight BMI
<18.5
Normal weight BMI
18.5-24.9
Overweight BMI
25-29.9
Obese BMI
>=30
IBW equation (male)
50 kg + 2.3 (in > 5 feet)
IBW equation (female)
45.5 + 2.3 (in > 5 feet)
Adjusted Body Weight
IBW + 0.4 (Actual BW - IBW)
Definition of obesity
> 120-130% of IBW
Which drugs are dosed with IBW?
Narrow therapeutic index drugs to avoid toxicity
Which weight to use for underweight patients?
Actual Body Weight - to avoid overdosing
When to use actual body weight for normal weight patients?
Actual Body Weight for most drugs
When to use IBW for normal weight patients?
Aminophylline, theophylline, acyclovir
When to use TBW for obese weight patients (>120-130% of IBW)?
TBW for LMWH, UFH, Vancomycin
When to use IBW for obese weight patients (>120-130% of IBW)?
IBW for aminophylline, theophylline, acyclovir
When to use AdjBW for obese weight patients (>120-130% of IBW)?
AdjBW for aminoglycosides (use Actual BW or IBW if patient is not obese)
BUN:Scr > 20:1
Dehydration
BUN:Scr < 20:1
...
Cockcroft-Gault Equation
CrCl (ml/min) = [(140-age) Weight] / (72SCr) * 0.85 if female
When to use ABW in calculating CrCl?
Underweight (ABW<IBW)
When to use IBW in calculating CrCl?
Normal weight (ABW ~ IBW)
When to use AdjBW in calculating CrCl?
Overweight (ABW > IBW)
Nutrition sources from 3 components
Carbohydrates, fat, protein
Calories of carbs in EN formulas
4 kcal/g
Calories of fats in EN formulas
9 kcal/g
Calories of protein in EN formulas
4 kcal/g
Calories of dextrose mononydrate in PN formulas
3.4 kcal/g
Calories of glycerol/glycerin in PN formulas
4.3 kcal/g
Calories of IV fat emulsion 10% in PN formulas
1.1 kcal/ml
Calories of IV fat emulsion 20% in PN formulas
2 kcal/ml
Calories of IV fat emulsion 30% in PN formulas
3 kcal/ml
Calories of amino acid solutions (Aminosyn, Freamine.... ) in PN formulas
4 kcal/g
Fluid calculations
When weight >20 kg
= 1500 ml + (20 ml)*(Wt in kg-20)

30-40 ml/kg/day
...
...
Lipid emulsions cannot be filtered through _______ micron filters. They need _____ micron filters.
NOT 0.22 micron filters
NEED 1.2 micron filters
Which of these need a filter? PN/EN/Neither/Both
PN
Sodium formulations for PN
Sodium chloride
Sodium acetate
Which sodium formulation used for acidosis?
Sodium acetate
Potassium range
3.5 - 5 mEq/L
Calcium range
8.5 - 10.5 mg/dL
When to adjust for calcium? Why?
Low albumin : <3.5 g/dL
Almost half of calcium bound to albumin. When albumin is low, Ca is falsely low.
How to adjust for calcium?
Ca (corrected) = Ca (serum) + [(4.0-albumin)*0.8)]
Calcium formulations?
Calcium gluconate
Calcium chloride
Which Calcium formulation to use in PN? Why?
Calcium gluconate
- less reactive
- lower risk of precipitation
- Lower dissociation constant vs CaCl2, leaving less free calcium available in solution to bind PO4
Order of addition of PN?
- Calcium
- Phosphate
- Dextrose
- Amino acids
- Other components
Dextrose, amino acids
Then phosphate
Then other components
Then Calcium last
Calcium and Phosphate added together must not exceed _____ mEq/L
45 mEq/L
4 Fat-soluble vitamins
A, D, E, K
9 water-soluble vitamins
Thiamine (B1)
Riboflavin (B2)
Niacin (B3)
Pantothenic acid (B5)
Pyridoxine (B6)
Ascorbic acid (C)
Folic acid (B9)
Cyanocobalamin (B12)
Biotin (B7)
Trace Elements
Zinc
Copper
Chromium
Manganese
Selenium
Trace elements not to be used in severe liver dz
Manganese
Copper
Trace elements not to be used in renal dz
Chromium
Molybdenum
Selenium
Insulin in PN
usually <=50% of what the person is expected to require per day, the rest supplemented with sliding scale.
Drugs that interfere with enteral nutrition
- Warfarin
- Tetracycline - chelates
- Oral ciprofloxacin. Use crushed IR tabs in water instead and flush with water before and after admininistration
- Phenytoin
Times to separate out drugs from enteral nutrition
1 hour before, 2 hours after
Drop factor?
drops/mL
Primary buffering system of the body. Which base, which acid?
Bicarb (HCO3-)/carbonic acid (H2CO3)
Organs involved in buffering the body, molecules
Lungs (CO2)
Kidneys (HCO3-)
Acidosis pH
pH < 7.35
Alkalosis pH
pH > 7.45
Metabolic acidosis cause
decrease in HCO3-
Metabolic alkalosis cause
increase in HCO3-
Respiratory acidosis cause
Increased pCO2
Respiratory alkalosis cause
Decreased pCO2
ABG measures ..?
pH/pCO2/pO2/HCO/O2 sat
Metabolic acidosis compensation
HCO3- decr --> CO2 decr by hyperventilation
Metabolic alkalosis compensation
HCO3- incr --> CO2 incr by hypoventilation
Respiratory acidosis compensation
CO2 incr --> HCO3 incr
Respiratory alkalosis compensation
CO2 decr --> HCO3 decr by 2 mmol/l for every 10 mmHg decrease in pCO2 from reference value of 40 mmHg
Calculation of anion gap
Na - Cl - HCO3
When pH = pKa, what is the relationship of acid to base (ionized to unionized)?
half ionized and half unionized
If pH > pKa, ratio to acid to base is ___
<1
If pH = pKa, ratio to acid to base is ___
1
If pH < pKa, ratio to acid to base is ___
>1
(Ionized/unionized) drug is soluble but (can/cannot) cross the membranes.
Ionized
Cannot
Most drugs are (weak acids/weak bases)
Weak acids
Can pick up a proton to cross the lipid layer
Weak acid formula
pH = pKa + log (salt/acid)
Weak base formula
pH = (pKw*-pKa) + log (base/salt)

OR

pH = pKa + log (base/salt)
% ionization equation for weak acid
100/[1+10^(pKa-pH)]
% ionization equation for weak base
100/[1+10^(pH-pKa)]
Calcium carbonate product names
Oscal
Tums
Calcium carbonate administration
Acid-dependent absorption. Needs to be taken with meals.
Calcium carbonate elemental calcium %
40%
Dense form of calcium
Calcium citrate product
Citracal
Calcium citrate administration
Acid-INdependent absorption
Taken with or without food
Calcium citrate elemental calcium %
21%
less dense
Calcium acetate product
PhosLo
Calcium acetate administration
NOT for calcium replacement.
Used as a phosphate binder
Absolute neutrophil count equation
WBC * [(%segs + % bands)/100]
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