Calculations IV: Clinical
What is the CockCroft-Gault Equation?
(140 - age)(weight) / (72)(SCr) all x(0.85 if female) used to determine renal function
Calculate the BMI for a male who is 6' tall and weighs 198 pounds. Round to the nearest tenth. What category do they fall under?
- 6'0'' = 72 inches - BMI = [198/(72^2)] *703 = 26.85 = 26.9 BMI of 27 = Overweight
What medications require adjusted body weight (ABW)?
- Aminoglycosides
What percent of elemental calcium does calcium carbonate contain?
40%
What is the equation for BMI (kg/m)^2
BMI = Weight (kg)/ height (m)^2
When do you use TBW?
When TBW < IBW or TBW = IBW
When do you use ABW?
When TBW is 120% or greater than IBW
Does calcium carbonate need to be taken with or without food?
With food
What is the pH of a solution prepared to be 0.4 M ammonia and 0.04 M ammonium chloride (pKb for ammonia = 4.76) Round to the nearest hundredth.
pH = (14-4.76) + log (0.4/0.04) = 10.24
What is the pH of a solution prepared to be 0.5 M sodium citrate and 0.05 citric acid? pKa for citric acid = 3.13. Round to the nearest hundredth.
pH = 3.13 + log(0.5/0.05) = 4.13
What is the weak base formula?
pH = pKa + log[acid/base]
What is the weak acid formula?
pH = pKa + log[base/acid]
What is alkalosis?
pH above 7.45
What is acidosis?
pH below 7.35
The 8 AM medications scheduled for a patient include Tygacil dosed at 6 mg/kg. The patient weighs 142 pounds. The nurse has Tygacil labeled 500 mg/50 mL NS. The dose will be administered over thirty minutes. The IV tubing in the unit delivers 15 drops per milliliter. What is the correct rate of flow in drops per minute? Round to the nearest drop.
- 142 pounds = 64.55 kg - 6 mg/kg * 64.55 kg = 387.2727 mg - 500 mg/50 mL * x = 387.2727 mg = 38.73 mL - 15 drops/mL * 38.73 mL = 581 drops - 581 drops/30 minutes = 19 drops/min
The pharmacy has insulin vials containing 100 units of insulin/mL. A physician orders 15 units of regular insulin to be added to a liter of D5W to be given over 10 hours. How many units of insulin will the patient receive each hour if the IV set delivers 15 drops/mL? Do not round the answer.
- 15 units/10 hrs = 1.5 units/hr
A patient is taking 3 calcium citrate tablets daily (one tab TID). Each weighs 1500 mg total. She wishes to trade her calcium tablets for the carbonate form. If she is going to use 1250 mg carbonate tablets (by weight) how many tablets will she need to provide the same dose?
- 1500 mg * 0.21 = 315 mg elemental calcium - 315 mg * 3 = 945 mg elemental calcium/day - 1250 mg * 0.40 = 500 mg elemental calcium - 945/500 = 1.8 tablets = 2 tablets
A 165 pound patient is to receive 250 mL of a dopamine drip at a rate of 17 mcg/kg/min. The pharmacy has dopamine premixed in a concentration of 3.2 mg/mL in D5W. Calculate the infusion rate in mL/minute. Round to the nearest tenth.
- 165 pounds = 75 kg - 17 mcg/kg/min * 75 kg = 1275 mcg/min - 3.2 mg/mL = 3200 mcg/mL - 1 mL/3200 mcg * 1275 mcg/min = 0.398 mL/min = 0.4 mL/min 0.4 mL/min
A physician writes an order for aminophylline 500 mg IV, dosed at 0.5 mg per kg per hour for a female patient (185 pounds, 5'1''). There is only theophylline in stock. How many milligrams (mg) of theophylline will the patient receive per hour? Round to the nearest whole number.
- 185 pounds = 84 kg - IBW = 45.5 + (2.3*1) = 47.6 - 0.5 mg/kg * 47.6 = 23.8 - 23.8 * 0.8 = 19.04 mg = 19 mg per hour 19 mg per hour
JY is a 58 year old male hospitalized for a total knee replacement. He was given UFH and developed HIT. Argatroban was ordered a dose of 2 mcg/kg/min. The pharmacy mixes a concentration of 100 mg argatroban in 250 mL of D5W. JY weighs 187 lbs. At what rate (mL/hr) should the nurse infuse argatroban to provide the desired dose? Round to the nearest whole number.
- 187 lbs = 85 kg - 85 kg * 2 mcg/kg/min = 170 mcg/min - 100 mg = 100,000 mcg - 100,000 mcg/250 mL = 400 mcg/mL - 1 mL/400 mcg * 170 mcg/min = 0.425 mL/min - 0.425 mL/min * 60 min/1 hr = 26 mL
If 200 mg of drug are added to a 500 mL bag, what rate of flow, in milliliters per hour, will deliver 500 mcg of drug per hour? Round to the nearest hundredth.
- 200 mg = 200,000 mcg - 200,000/500 mL = 400 mcg/mL - 400 mcg/mL * x = 500 mcg - x = 1.25 mL - 1.25 mL/hr 1.25 mL/hr
A patient is to receive 600,000 units of penicillin G potassium in 100 mL D5W. A vial of penicillin G potassium 1,000,000 units is available. The manufacturer states that when 4.6 mL of diluent is added, a 200,000 units/mL solution will result. How many milliliters of reconstituted solution would be withdrawn and added to the bag of D5W?
- 200,000 units/mL *x = 600,000 units - x = 3 mL
A 64 year old female patient (5'5'', weight 205 pounds) is hospitalized with a nosocomial pneumonia which is responding to treatment. Her current antibiotic medications include Ciprofloxacin, Primaxin and vancomycin. Her morning laboratory values include: K 4mEq/L, BUN 60 mg/dL, SCr 2.7 mg/dL, and glucose 222 mg/dL. Based on the renal dosage recommendations from the package labeling below, What is the correct dose of primaxin for this patient? CrCl. 71 or more = 500 mg IV Q6h 41-70 = 500 mg IV Q8h 21-40 = 250 mg IV Q6h 6-20 = 250 mg IV Q12h
- 205 pounds = 205/2.2 = 93.18 kg - IBW = 45.5 *(2.3*5) = 57 kg - 93.18/57 = 1.63 - ABW = 57 + (93.18-57) = 71.5 kg - CrCl = (140 - 64) * 71.5 = 5432 - 72*2.7 = 194.4 - 7081.82/194.4 = 28 mL/min - 28 * 0.85 = 23.75 - 250 mg IV Q6h
The pharmacist has an order for heparin 25,000 units in 250 mL D5W to infuse at 1,000 units/hr. How many hours will it take to infuse the entire bag?
- 25,000 units * 1 hr/1000 units = 25 hours 25 hours
The pharmacist has an order for heparin 25,000 units in 250 mL D5W to infuse at 1000 units/hr. The pharmacy has the following premixed heparin bags in stock: 25,000 units in 500 mL 1/2 NS, 10,000 units in 250 mL D5W, and 25,000 units in 250 mL D5W. What should the infusion rate be set at in mL/hr?
- 25,000 units/250 mL = 100 units/mL - 100 units/mL - 1000 units/hr * 1 mL/100 units = 10 mL/hr 10 mL/hr
A physician has ordered 2 grams of cefotetan to be added to 100 mL NS for a 56 year old female with an anaerobic infection. Using a reconstituted injection containing 154 mg/mL, how many milliliters should be added to prepare the order? Round to the nearest whole number.
- 2g = 2000 mg - 2000 mg * 1 mL/154 mg = 12.98 mL = 13 mL 13 mL
An order is written for phenytoin IV. A loading dose of 15 mg/kg is to be infused at 0.5 mg/kg/min for a 33 pound child. The pharmacy has phenytoin injection solution 50 mg/mL in a 5 mL vial in stock. The pharmacist will put the dose into 50 mL NS. Over how many minutes should the dose be administered? Round to the nearest whole number.
- 33 pounds = 15 kg - 15 kg * 15 mg/kg = 225 mg - 0.5 mg/kg/min = 7.5 mg/min - 225 mg * 1 min/7.5 mg = 30 minutes 30 minutes
A patient will receive 400 mg of a drug that has been put in a 250 mL IV bag. The rate of drug administered is 375 mcg per minute. Calculate the flow rate in milliliters per hour. Round to the nearest whole number.
- 375 mcg = 0.375 mg - 0.375 mg/minute * 60 minutes/hr = 22.5 mg/hr - 250 mL/400 mg * 22.5 mg/hr = 14 mL/hr
A nurse is hanging a 4% lidocaine drip for a patient. If the dose ordered is 6 mg/min, how many hours will a 250 mL bag last? Round to the nearest tenth.
- 4% = 4 g/100 mL = 4000 mg/100 mL - 4000 mg/100 mL * 250 mL = 10,000 mg - 10,000 mg/6 mg/min = 1666.67 min - 1666.67 min * 1 hour/60 min = 27.77 hours = 27.8 hours 27.8 hours
A 68 kg patient is receiving a drug in a standard concentration of 400 mg/250 mL of 1/2 NS running at 15 mL/hr. Calculate the dose in mcg/kg/min. Round to the nearest hundredth.
- 400 mg = 400,000 mcg - 400,000 mcg/250 mL = 1600 mcg/mL - 15 mL/hr *1600 mcg/mL = 24000 mcg/hr - 24000 mcg/hr *1 hr/60 min = 400 mcg/min - 400 mcg/min/68 kg = 5.88 mcg/kg/min
A patient is to receive Keppra at a rate of 5 mg/min. The pharmacy has a 5 mL keppra vial (100mg/mL) which will be diluted in 100 mL of NS. What is the keppra infusion rate, in mL/min? Do not include the volume of the 5 mL additive.
- 5 mL * 100 mg/mL = 500 mg - 500 mg/100 mL = 5 mg/mL - 1 mL/5 mg *5 mg/min = 1 mL/min 1 mL/min
If 50 mg of drug are added to a 500 mL bag, what rate of flow, in milliliters per hour, will deliver 5 mg of drug per hour?
- 50 mg/500 mL = 0.1 mg/mL - 0.1 mg/mL * x = 5 mg - x = 50 mL - 50 mL/hr
A male patient comes to the pharmacy and tells the pharmacist he is 6'7'' tall and weighs 250 pounds. His waist circumference is 43 inches. Calculate his BMI. Round to the nearest whole number. What is the patient's category in regards to their BMI?
- 6'7'' = 79 inches - BMI = 250/(79)^2 * 703 = 28.16 = 28 BMI = 28 ---> Overweight
A patient is being seen at the oncology clinic today after her first round of chemotherapy one week ago. A CBC with differential is ordered and reported back as WBC = 14.8 x 10^3 cells/mm^3, sees 10% and bands 11%. Calculate this patient's ANC.
- ANC = 14.8 x10^3 *[10 +11]/100 = 3108 cells/mm^3
A patient is taking clozapine and is at the linic for a routine visit. Today's labs include WBC = 4300 cells/mm^3 with 48% sets and 2% bands. Calculate this patient's ANC.
- ANC = 4300 *[48+2]/100 = 2150 cells/mm^3
What medications require IBW if TBW is greater than 120%?
- Aminophylline - Theophylline - Acyclovir - Levothyroxine
Looking at the laboratory values below, what is the hydration status of the patient? BUN = 54 mg/dL Creatinine = 1.8 mg/dL
- BUN:SCr = 54/1.8 = 30 Patient is dehydrated
A female patient is to receive 5 mg/kg/day of theophylline. The patient is 5'7'' and weighs 243 pounds. Calculate the daily theophylline dose the patient should receive?
- IBW = 45.5 + (2.3*7) = 61.6 kg - TBW = 243/2.2 = 110.5 kg - 110.5/61.6 = 1.8 = 180% more than IBW - Theophylline uses IBW - 61.6 kg * 5mg/kg/day = 308 mg/day
A 34 year old male (height 6'7'', weight 287 pounds) is hospitalized after a motor vehicle accident. He develops a Pseudomonas aeruginosa infection. The physician orders tobramycin 2 mg/kg IV Q8h. Calculate the tobramycin dose. Round to the nearest 10 milligrams.
- IBW = 50 + (2.3*19) = 93.7 kg - TBW = 287/2.2 = 130.45 kg - 130.45/93.7 = 1.4 = 140% more than IBW - ABW = 93.7+(0.4*(130.45-93.7)) = 108.4 kg - 2 mg/kg * 108.4 kg = 216.8 mg = 220 mgIV Q8h
How do you know if the body is in respiratory acidosis or alkalosis?
- If CO2 is low = Respiratory alkylosis - If CO2 is high, Respiratory acidosis
How do you know if the body is in metabolic acidosis or alkalosis?
- If bicarbonate is high = metabolic alkalosis - If bicarbonate is low = metabolic acidosis
A physician orders 15 units of regular insulin to be added to a liter of D5W to be given over 10 hours. What is the infusion rate, in drops/minute, the IV set delivers 15 drops/mL? Do not include the insulin volume in the calculation.
- Need drops/mL - 1 L = 1000 mL - 10 hours = 600 minutes - 15 drops/mL * 1000 mL * 1/600 minutes = 25 drops/minute
An order is written for 10 mL of a 10% calcium chloride injection and 10 mL of multivitamin injection (MVI) to be added to 500 mL of D5W. The infusion is to be administered over 6 hours. The IV set delivers 15 drops/mL. What should be the rate of flow in drops/minute to deliver this infusion?
- Need drops/min - 10 mL + 10 mL + 500 mL = 520 mL - 15 drops/mL * 520 mL * 1/360 minutes = 21.67 drops/min = 22 drops/min 22 drops/min
A physician orders an IV infusion of D5W 1 liter to be delivered over 8 hours. The IV infusion set delivers 15 drops/mL. How many drops/min will the patient receive? Round to the nearest whole number.
- Need drops/min - 8 hours = 480 minutes - 15 drops/mL * 1000 mL* 1/480 minutes = 31.25 minutes = 31 drops/minutes 31drops/ minutes
RS is a 45 year old male, 5'5'', 168 pounds, hospitalized with a diabetic foot infection. The pharmacist prepared a 500 mL bag of D5W containing 1 gram of vancomycin to be infused over 4 hours using a 20 gtts/mL IV tubing set. How many mg of vancomycin will the patient receive each minute? Round to the nearest tenth.
- Need mg/minute - 1 g = 1000 mg - 1000 mg/4 hours = 1000 mg/240 minutes = 4.16 mg/min = 4.2 mg/min 4.2 mg/min
Levofloxacin, dosing per pharmacy, is ordered for an 87 year old female patient (5'4'', weight 103 pounds). Her labs include BUN 22 mg/dL and SCr 1 mg/dL. Choose the correct dosing regimen based on renal dosage adjustments from the package labeling below. CrCl 50 mL/min or more = 500 mg Q24h 20-49 mL/min = 250 mg Q24 hours < 20 mL/min = 250 mg Q48 hours
- TBW = 46.8 kg - IBW = 45.5 +(2.3*4) = 54.7 - CrCl = (140-87) *46.8 = 2480.4 - 2480.4 *.85 = 2108.34 - 2108.34/72 = 29 mL/min 250 mg Q24h
A 50 year old male (height 6'1'', weight 177 pounds) has HIV and is being started on tenofovir, emtricitabine, and efavirenz therapy. His laboratory values include K 4.4 mEq/L, BUN 40 mg/dL, SCr 1.8 mg/dL, and CD4 count of 455 cells/mm^3. Using the renal dosage, what dose should be given? CrCl 50 mL/min = 300 mg/day 30-49 mL/min 300 mg Q48 hours 10-29 mL/min 300 mg Q72-96 hours - Less than 10 mL/min = 300 mg weekly
- TBW = 80.45 kg - IBW = 50 + 2.3*13 = 79.9 kg - 80.45/75.3 = 1.06 - CrCl = (140-50)*79.9/(72*1.8) - CrCl = 55 mL/min 300 mg/day
What weight do you use for CCG?
- TBW if less than IBW - IBW if TBW is greater - ABW is TBW is 120% greater than IBW
When is CCG not accurate?
- Used in young children - Used in ESRD - When renal function is fluctuating rapidly
Which drugs use TBW no matter what the patient weighs?
- Vancomycin - LMWH - UFH
An elderly female is admitted to the hospital after a motor vehicle accident. She suffered a head injury and is in the ICU. An ABG is obtained and the results are as follows: 8.25/29/97/26/98%. What acid/base disorder does the patient have?
- pH = Alkylosis - PCO2 = Low = Alkylosis - PO2 = Normal - HCO3 = Normal - PO2 = Normal Respiratory alkalosis
A babysitter brings a 7 year old boy to the emergency department. He is unarousable. Labs are ordered and an ABG is drawn. The ABG results are as follows: 6.72/40/90/12/94%. What acid base disorder does this child have?
- pH = acidic - PCO2 = Normal - PO2 = Normal - Bicarbonate = Acidic - O2 sat = Low Metabolic acidosis
A patient is to receive 1.5 liters of NS running at 45 gtts/min using a 15 gtts/mL IV tubing set. Calculate the total infusion time in hours. Round to the nearest tenth.
1.5 liters = 1500 mL - 1 mL = 15 drops - 45 drops/15 drops/mL = 3 mL/min - 1500 mL * 1/3 mL/min = 500 minutes = 8.33 hours 8.3 hours
A patient is to receive Flagyl at a rate of 12.5 mg/min. The pharmacy has a 5 mL (100 mg/mL) Flagyl injection vial to be diluted in 100 mL of NS. How much drug in milligrams will the patient receive over 20 minutes?
12.5 mg/min * 20 minutes = 250 mg
What percent of elemental calcium does calcium citrate contain?
21%
What is the normal range for HCO3?
22-26 mEq/L
What is the normal range for pCO2?
35-45 mmHg
What is the normal pH of blood?
7.35-7.45
What is the normal range for PO2?
80-100 mmHg
What are the different categories for BMI?
< 18.5 = Underweight 19.5-24.9 = Normal 25-29.9 = Overweight 30 and above = Obese
What are the causes of anion gap?
<MUDPILERS> Methanol Uremia Diabetic ketoacidosis Paraldehyde Isoniazid Lactic Acidosis Ethyl Alcohol (ETOH) Rhabdomyelitis Salicylates
- What is creatinine?
A breakdown product produced when muscle tissue makes energy.
What is an acid?
A compound that donates H+ ions to a solution
What is body mass index?
A measure of body weight relative to height
A patient in the ICU has recently developed an acidosis. Using the laboratory parameters below, calculate the patient's anion gap Na = 139 Cl = 101 K = 4.6 HCO3 = 19 SCr = 1.6 BUN = 38
AG = 139-101-19 = 19
What is the equation for anion gap?
AG = Na-Cl-HCO3
What is the equation for absolute neutrophil count?
ANC = WBC *[% segs +% bands]/100
What is the normal range for O2 sat?
Above 95%
What is the equation for adjusted body weight?
Adj = IBW + 0.4 * (TBW - IBW)
What is a flow rate?
Amount of fluids that is given IV over a period of time
What does CO2 act as in the body?
An acid
What is absolute neutrophil count?
An indication of the immune system's ability to fight infection.
What is the equation for BMI in regards to inches and pounds?
BMI = weight (lbs)/height (inch)^2 to convert to kg/m^2 multiply by 703
NK is receiving a furosemide infusion at 5 mg/hr. The nurse notices her urine output has decreased in the last hour. Laboratory values are drawn and the patient ha sa SCr of 1.5 mg/dL and a BUN of 26 mg/dL. The nurse wants to know if she should stop the furosemide infusion due to the patient becoming dehydrated. What is the correct assessment of the patient's hydration status?
BUN:SCr ratio = 26/1.5 = 17.33 The patient is not dehydrated because 17.33 < 20
How do you change from theophylline to aminophyline?
Divide by 0.8
Does elemental calcium need to be taken with or without food?
Either
What does bicarbonate do in the body?
Helps control pH in the body by acting as a base
What is a base?
Hydrogen acceptor
What is the equation for ideal body weight?
IBW (males) = 50 kg + 2.3*(number of inches greater than 5 feet) IBW (females) = 45.5 kg + 2.3*(number of inches greater than 5 feet)
How is creatinine cleared from the body?
Kidneys
Calculate log (1/0.5) Round to the nearest tenth
Log (1/0.5) = 0.3
How do you change from aminophyline to theophylline?
Multiply by 0.8 Remember ATM
What happens if the kidney function declines?
SCr increases (creatinine in the blood increases)
What is ideal body weight?
The optimal weight for one's height, age, sex, and body build.
What is actual body weight (also known as total body weight)?
Weight of a patient on a weighed scale
What is adjusted body weight?
Weight used when patients are obese or overweight
What indicates dehydration?
When BUN:SCr ratio > 20.1
