Calculation of Maintenance Fluids

Question 1

What is the 100/50/20 rule?

Answer 1

Maintenance IV fluids for a 24-hour period:
100 mL/kg for the first 10 kg
50 mL/kg for the next 10 kg
20 mL/kg for every kg over 20 (divide
by 24 for hourly rate)

Question 2

What is the 4/2/1 rule?

Answer 2

Maintenance IV fluids for hourly rate:
4 mL/kg for the first 10 kg
2 mL/kg for the next 10 kg
1 mL/kg for every kg over 20

Question 3

What is the maintenance for

a 70-kg man?

Answer 3

Using 100/50/20:
100 x 10 kg = 1000
50 x 10 kg = 500
20 x 50 kg = 1000
Total = 2500
Divided by 24 hours = 104 mL/hr
maintenance rate

Using 4/2/1:
4 x 10 kg = 40
2 x 10 kg = 20
1 x 50 kg = 50
Total = 110 mL/hr maintenance rate

Question 4

What is the common adult

maintenance fluid?

Answer 4

D5 1/2 NS with 20 mEq KCl/L

Question 5

What is the common pediatric

maintenance fluid?

Answer 5

D5 1/4 NS with 20 mEq KCl/L (use
1/4 NS because of the decreased ability
of children to concentrate urine)

Question 6

Why should sugar (dextrose)
be added to maintenance
fluid?

Answer 6

To inhibit muscle breakdown

Question 7

What is the best way to

assess fluid status?

Answer 7

Urine output (unless the patient has
cardiac or renal dysfunction, in which
case central venous pressure or wedge
pressure is often used)

Question 8

What is the minimal urine
output for an adult on
maintenance IV?

Answer 8

30 mL/hr (0.5 cc/kg/hr)

Question 9

What is the minimal urine
output for an adult trauma
patient?

Answer 9

50 mL/hr

Question 10

How many mL are in 12 oz

(beer can)?

Answer 10

356 mL

Question 11

How many mL are in 1 oz?

Answer 11

30 mL

Question 12

How many mL are in 1 tsp?

Answer 12

5 mL

Question 13

What are common isotonic

fluids?

Answer 13

NS, LR

Question 14

What is a bolus?

Answer 14

Volume of fluid given IV rapidly (e.g., 1 L
over 1 hour); used for increasing intravascular
volume, and isotonic fluids should
be used (i.e., NS or LR)

Question 15

Why not combine bolus fluids

with dextrose?

Answer 15

Hyperglycemia may result

Question 16

What is the possible consequence
of hyperglycemia in
the patient with hypovolemia?

Answer 16

Osmotic diuresis

Question 17

Why not combine bolus fluids
with a significant amount of
potassium?

Answer 17

Hyperkalemia may result (the potassium

in LR is very low: 4 mEq/L)

Question 18

Why should isotonic fluids
be given for resuscitation
(i.e., to restore intravascular
volume)?

Answer 18

If hypotonic fluid is given, the tonicity of
the intravascular space will be decreased
and H2O will freely diffuse into the
interstitial and intracellular spaces; thus,
use isotonic fluids to expand the intravascular
space

Question 19

What portion of 1 L NS will
stay in the intravascular
space after a laparotomy?

Answer 19

In 5 hours, only 200 cc (or 20%) will

remain in the intravascular space!

Question 20

What is the most common

trauma resuscitation fluid?

Answer 20

LR

Question 21

What is the most common
postoperative IV fluid after
a laparotomy?

Answer 21

LR or D5LR for 24 to 36 hours, followed

by maintenance fluid

Question 22

After a laparotomy, when
should a patient’s fluid be
“mobilized”?

Answer 22

Classically, POD #3; the patient begins to
“mobilize” the third-space fluid back into
the intravascular space

Question 23

What IVF is used to replace
duodenal or pancreatic fluid
loss?

Answer 23

LR (bicarbonate loss)