Dosage calculation practice questions

Question 1

A client who weighs 84 kg (185 lb) is in the intensive care unit with septic shock. The indwelling urinary catheter drained 34 mL at 0900, 28 mL at 1000, and 22 mL at 1100. How many mL/kg/hr should the nurse document as the client's average urine output for these 3 hours? Record your answer using 1 decimal place.

Accepted Answer

0.3 or .3. Urine output is one of the best bedside measures of perfusion, because the kidneys cut back urine production as soon as their blood flow drops. The target in shock is at least 0.5 mL/kg/hr. Using the client's weight matters, because the 30 mL/hr figure often quoted is only right for a client of about 60 kg.

This client averages 28 mL/hr, which is 0.3 mL/kg/hr. The minimum for 84 kg is 42 mL/hr. The output is under target and falling each hour, so the nurse checks that the catheter is draining freely, reassesses the MAP and the rest of the perfusion picture, and reports to the health care provider.

Question 2

A newborn who weighs 4.2 kg was born to a client with gestational diabetes. At 3 hours of age the newborn is jittery and has a weak suck, and the heel-stick blood glucose is 22 mg/dL. The health care provider prescribes dextrose 10% in water 2 mL/kg IV over 1 minute. How many mL should the nurse administer? Record your answer using 1 decimal place.

Accepted Answer

8.4. A blood glucose of 22 mg/dL with symptoms in a newborn of a diabetic mother is severe hypoglycemia. The newborn's own insulin is still high from the months of maternal hyperglycemia, so feeding alone cannot raise the blood glucose fast enough, and jitteriness and a weak suck show the brain is already short of fuel. IV dextrose 10% in a small bolus of 2 mL/kg gives 200 mg/kg of glucose, followed by a continuous dextrose infusion. For this newborn, 2 mL/kg × 4.2 kg = 8.4 mL. The answer is 8.4 mL.

Concentrated dextrose such as 25% or 50% is not used in newborns. It irritates the veins and causes a sharp rise in blood glucose that triggers more insulin release and a rebound low.

Question 3

A 63-year-old client who had a stroke receives continuous enteral feeding through a gastrostomy tube. Phenytoin 100 mg is prescribed through the tube every 8 hours. The pharmacy supplies phenytoin oral suspension 125 mg/5 mL. How many mL should the nurse administer? Record your answer using a whole number.

Accepted Answer

4. Phenytoin oral suspension is used when a client cannot swallow capsules. Here the suspension holds 125 mg/5 mL = 25 mg/mL, and 100 mg ÷ 25 mg/mL = 4 mL. The answer is 4 mL. The dose is drawn up in an oral or enteral syringe, never an IV syringe, so it cannot be connected to an IV line by mistake. Phenytoin binds to the protein in enteral formula, and much of the dose is lost when the two meet in the tube. Most facilities pause a continuous feeding for 1 to 2 hours before and after each dose and flush the tube with water before and after it, and the nurse follows the facility protocol. The suspension is shaken well first, because phenytoin settles to the bottom and an unshaken bottle gives uneven doses.

Question 4

The nurse is caring for a client with heart failure who has a prescription for furosemide 60 mg orally once daily. The nurse has furosemide 40 mg scored tablets available. How many tablets should the nurse administer? Record your answer using 1 decimal place.

Accepted Answer

1.5. Dosage calculation starts by putting the prescribed dose over the dose on hand. The prescribed dose is 60 mg and each tablet holds 40 mg, so the client needs one and a half tablets. The tablets are scored, which means they are made to be split along the line, so a half tablet is an accurate dose.

Before giving furosemide, the nurse checks the BP and the most recent potassium, because a loop diuretic can cause hypotension and hypokalemia.

Question 5

After a kitchen grease fire, a 41-year-old client is admitted to the burn unit with partial-thickness and full-thickness burns covering the entire posterior trunk, the entire right arm, and the posterior right leg. The face has red, painful, intact skin with no blisters. Using the rule of nines, what percentage of total body surface area (TBSA) should the nurse use to calculate the fluid resuscitation? Record your answer using a whole number.

Accepted Answer

36. The rule of nines divides the adult body into areas worth 9% or multiples of 9%. The head and neck are 9%. Each arm is 9%. Each leg is 18%, split into 9% for the anterior surface and 9% for the posterior surface. The anterior trunk is 18%, the posterior trunk is 18%, and the perineum is 1%.

Only partial-thickness and full-thickness burns count toward the TBSA used for fluid resuscitation. The red, painful, intact skin on the face is a superficial burn, the kind a sunburn causes. The outer layer of skin is still in one piece, so the capillaries are not leaking fluid out of the circulation, and superficial burns are left out of the total.

So this client has 36% TBSA. That number goes into the Parkland formula along with the client's weight.

Question 6

During a power failure on a medical unit, the battery of an infusion pump runs down, and no replacement pump is available. A 67-year-old client is prescribed 0.9% sodium chloride 1,000 mL IV over 8 hours. The nurse sets up the infusion by gravity using tubing with a drop factor of 15 gtt/mL. How many gtt/min should the nurse regulate the infusion to deliver? Record your answer using a whole number.

Accepted Answer

31. A gravity infusion is controlled by counting drops in the drip chamber, so the nurse needs the rate in drops per minute. The drop factor on the tubing package tells how many drops make 1 mL. Macrodrip tubing is usually 10, 15, or 20 gtt/mL, and microdrip tubing is 60 gtt/mL. Here 1,000 mL ÷ 480 minutes × 15 gtt/mL = 31.25 gtt/min, which rounds to 31 gtt/min. The answer is 31 gtt/min.

The nurse counts the drops for a full minute while adjusting the roller clamp, then rechecks the rate and the volume in the bag often, because a gravity infusion speeds up or slows down when the client moves the arm or changes position.

Question 7

The nurse is caring for a 60-year-old client who receives hemodialysis 3 times a week. The prescribed daily fluid allowance is the previous day's urine output plus 1,000 mL, and yesterday's urine output was 350 mL. Since 0600 today, the client has had 180 mL of coffee, 120 mL of apple juice, 240 mL of chicken broth, and 240 mL of ice chips. Ice chips are recorded at half of their measured volume. How many mL of fluid remain in the client's allowance for today? Record your answer using a whole number.

Accepted Answer

690. A client on hemodialysis has little or no kidney function between treatments, so almost everything the client drinks stays in the body until the next run. The daily allowance replaces what the client can still lose, which is the urine output plus the insensible losses through the skin and lungs. Anything more shows up as weight gain between treatments, high blood pressure, edema, and in the worst case pulmonary edema.

Everything liquid at room temperature counts, including broth, gelatin, ice pops, and ice chips. Ice is recorded at about half its volume, because melted ice takes up less space than the chips.

This client has used 660 mL of a 1,350-mL allowance and has 690 mL left for the rest of the day, including fluid taken with medications.

Question 8

An 84-year-old client who weighs 55 kg and cannot communicate after a stroke receives a high-protein 1.5 kcal/mL formula through a gastrostomy tube at 50 mL/hr, with a 30 mL water flush every 4 hours. Over 3 days the client has become lethargic. The urine is dark amber at 20 mL/hr, the mucous membranes are dry, the serum sodium is 152 mEq/L, the BUN is 38 mg/dL, and the glucose is 136 mg/dL. Complete the following sentence by choosing from the lists of options. The client is most likely experiencing [Blank 1] as a result of [Blank 2].

Accepted Answer

Blank 1: hypernatremic dehydration; Blank 2: too little free water for a high-protein formula. Tube feeding provides less water than it seems. A 1.5 kcal/mL formula is only about 75% to 78% water, so 1,200 mL a day of this formula gives about 900 mL of free water. With six 30 mL flushes, the client receives about 1,100 mL a day, well short of the roughly 1,650 mL a 55-kg older adult needs. A high-protein formula makes it worse, because the urea produced from the protein has to be excreted in urine and pulls water with it.

The client cannot ask for a drink, so the deficit builds silently. Water loss concentrates the blood, the sodium rises to 152 mEq/L, and the brain cells shrink, causing lethargy. Dark, scant urine, dry mucous membranes, and a high BUN all point to dehydration. The nurse reports the findings and anticipates a prescription for more free water flushes, with the sodium corrected slowly.

Question 9

The nurse in a long-term care facility is preparing the morning dose of lactulose 20 g orally for a 78-year-old client with chronic constipation. The available lactulose oral solution contains 10 g/15 mL. How many mL should the nurse administer? Record your answer using a whole number.

Accepted Answer

30. Lactulose is an osmotic laxative. It is a sugar that the small bowel cannot absorb, so it reaches the colon and draws water into the stool, which softens it and makes it easier to pass. It usually works in 24 to 48 hours.

The solution contains 10 g in every 15 mL, so 20 g is twice that volume, or 30 mL. The nurse measures it in a calibrated medicine cup at eye level. Lactulose can cause bloating, cramping, and diarrhea, and the nurse watches stool frequency and fluid and electrolyte status in an older adult.

Question 10

A 72-year-old client in the intensive care unit has a new pulmonary embolism. The client weighs 80 kg (176 lb). The health care provider prescribes a heparin bolus of 80 units/kg IV followed by a continuous infusion at 18 units/kg/hr. The pharmacy supplies heparin 25,000 units in 250 mL of 0.45% sodium chloride. How many mL/hr should the nurse set the IV infusion pump to deliver? Record your answer using 1 decimal place.

Accepted Answer

14.4. Weight-based heparin protocols set both the bolus and the infusion by the client's weight in kilograms. The infusion dose is 18 units for every kilogram each hour, which for 80 kg is 1,440 units/hr. The bag holds 25,000 units in 250 mL, which is 100 units in every milliliter, so the pump runs at 14.4 mL/hr. The bolus is 80 units/kg, which is 6,400 units.

Heparin is a high-alert medication. A second nurse independently checks the concentration, the dose, and the pump setting, and the aPTT or anti-Xa level is checked 6 hours after the infusion starts and after every rate change.

Dosage calculation practice questions.

The nurse is caring for a client with heart failure who has a prescription for furosemide 60 mg orally once daily. The nurse has furosemide 40 mg scored tablets available. How many tablets should the nurse administer? Record your answer using 1 decimal place.

The nurse in a long-term care facility is preparing the morning dose of lactulose 20 g orally for a 78-year-old client with chronic constipation. The available lactulose oral solution contains 10 g/15 mL. How many mL should the nurse administer? Record your answer using a whole number.

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