Calculations III and IV

Question 1

equation time: daily fluid needs

Answer 1

1500 + [20 x (kg - 20)]

the above provides you with daily mL needed, only applies to pts > 20kg

Question 2

equation time: total energy expenditure (TEE)

Answer 2

BEE x activity factor x stress factor

BEE will likely be provided per RxPrep (but its usually 15-20 kcal/kg/da

Question 3

PO carbs provide how many kcal?

what TPN additives can we use to provide carbs and how many kcal do they provide?

Answer 3

• PO carbs: 4 kcal/g
• dextrose monohydrate: 3.4 kcal/g
• glycerol/glycerin: 4.3 kcal/g

Question 4

PO fat provides how may kcal?

what TPN additives can we use to provide fat and how many kcal do they provide

Answer 4

• PO fat: 9 kcal/g
• injectable lipid emulsion (ILE) 10%: 1.1 kcal/mL
• 20%: 2 kcal/mL
• 30%: 3 kcal/mL

BE CAREFUL, THESE ARE PER ML (protein and carbs are per g)

Question 5

PO protein provides how many kcal

what TPN additives can we use to provide protein and how many kcal do they provide?

Answer 5

• PO protein: 4 kcal/g
• amino acid soln: 4 kcal/g

Question 6

daily protein requirement

Answer 6

• ambulatory, non-hospitalzed: 0.8-1 g/kg/day
• hospitalzed or malnourished: 1.2-2 g/kg/day

Question 7

how much nitrogen does a patient receive in a tpn

Answer 7

• nitrogen intake dependent on protein intake
• = g of protein intake / 6.25

Question 8

equation time: calcium correction

Answer 8

reported calcium + [(4 - albumin) x 0.8]

Question 9

there’s 2 things in a TPN that should NOT be given together, one of them should be added first when making the TPN, and the other should be added last, what are they?

Answer 9

• add phosphate first, then everything else, then sahke
• add calcium towards the end (preferably Ca gluconate because it has alower risk of precipitating with phosphate)
• keep pH of the TPN low and store in refrigerator to reduce precipitation risk

Question 10

which drugs, have special considerations for feeding tubes?

Answer 10

• warfarin: many enteral products bind to warfarin, hold feeds 1 hr before and after
• tetracyclines, quinolones, levothyroxine: chelate with polyvalent cations (Ca, Mg, Fe), separate from tube ffeeds
• ciprofloxacin: sticks to tube, curhs and mix with water, flush tubes before and after
• phenytoin: binds to feeding soln -> lower levels, hold feeds 2 hrs before and after

reasonable to hold feeds for 1 hr before, 1-2 for most drugs

Question 11

equation time: BMI

as well as BMI classifications

Answer 11

wt in kg divided by (ht in meters squared)

• < 18.5 underweight
• 18.5-24.9 normal
• 25- 29.9 overweight
• > 30 obese

Question 12

equation time: IBW

Answer 12

IBW male = 50 + (2.3 x in over 60”)

IBW female = 45.5 + (2.3 x in over 60”)

Question 13

equation time: Adj body weight

Answer 13

IBW + 0.4 ( TBW - IBW)

used for obese or overweight pt

Question 14

when do we use what wt (TBW, IBW, AdjBW)

like which drugs/equations uses what

Answer 14

• if underweight, almost always use TBW
• for normal weight, IBW ~ TBW, go with TBW for most meds (IBW for cockcroft gault, aminophylline, theophylline, acyclovir, and levothyroxine)

for obese pts
- ADj BW - for aminoglycosides (use this for cockcroft gault if BMI > 25)
- TBW - for lovenox, heparin, vanco
- IBW - same as normal wt

Question 15

Cockcroft gault

Answer 15

[(140 - age) divided by (72 x SCr)] multipled by wt

additionally multiply by 0.85 for female

• TBW for underweight
• usually IBW
• Adj BW if BMI > 25

Question 16

ABG what is what x/x/x/x/x

Answer 16

pH / pCO2 / pO2 / HCO3 / O2 sat

Question 17

equation time: anion gap

Answer 17

Na - Cl - HCO3

Question 18

what is the relationship between pH and pKa

Answer 18

• pH > pKa: more of the acid is iionized
• pH = pKa: ionized and unionized forms are equal
• pH < pKa: more of the acid is unionized (more conugate base present)

Question 19

equation time: pH

Answer 19

• weak acid formula: pH = pKa + log [salt / acid]
• weak base formula: pH = pKa + log [base / salt]

Question 20

equation time: percent ionization

Answer 20

• % ionization of weak acid: 100 / [ 1 + 10 ^(pKa - pH)]
• % ionization of weak base: 100 / [ 1 + 10 ^(pH - pKa)]

Question 21

what forms of calcium are used for Ca replacement and how much elemental Ca is in them

Answer 21

• calcium carbonate: 40% elemental Ca - take with food
• calcium citrate: 21% elemental Ca - can take with or without food

calcium acetate has 25% elemental Ca, but poor absorption, so only used as a phosphate binder

Question 22

equation time: amiophylline to theophylline conversion

Answer 22

1 mg aminothylline = 0.8 mg theophylline

Question 23

equatio time: ANC

and interpretation

Answer 23

ANC = WBC x [(%segs + %bands) / 100]

• 2200 - 8000: normal
• < 1000: neutropenic
• < 500: severe neutrophenia
• < 100: profound neutropenia