Transcript Maintenance: Water and Electrolyte Needs

DFM Fellows
Summer 2010
Objectives
 Understand the basics of fluid administration
 Review basics of various fluid options
 Be able to calculate maintenance fluid rates based
on patient weight
 Be able to estimate fluid losses
 Be able to calculate fluid replacement
The Learning Curve
 The information provided is general information
regarding fluid administration. Keep in mind that
different clinical situations require you to integrate your
clinical knowledge of the body and its physiology to
make an educated decision. Always consider the patients
age, condition, medications and co morbidities before
administering fluids.
 And as you screw up you will learn!
IV Fluids

The role of IV fluid administration is to
Provide volume replacement
Administer medications, electrolytes, blood products,
or diagnostic reagents
Maintenance/correction of nutritional status




Components of fluid and electrolyte therapy
1.
2.
Maintenance
Replacement
Normal Plasma Electrolyte Composition
CATION
Concentration ANION
mEq/L
Concentration
mEq/L
Sodium
135-145
Chloride
95-105
Potassium
3.5-5.0
Phosphate 2.5-30
Calcium
4.0-5.5
Sulfate
1.0
Organic
acids
Protein
2.0
Magnesium 1.5-2.5
Osmolarity 285-295
1.6
Commonly Used IV Solutions
Osmolarity
(mOsm/L)
Glucose
(gm/L)
Na+
(mEq/L)
K+
(mEq/L)
Cl(mEq/L)
0.9%
NS
308
154
154
½ NS
(.45%
NS)
154
77
77
LR
274
130
D5W
278
50
D5 ½
NS
406
50
77
4.0
109
77
Lactate
(mEq/L)
Ca++
(mEq/L)
28
3
Components of Fluid and Electrolyte
Therapy
Maintenance
1.
•
meeting the requirements for fluid and electrolyte
intake that balance daily obligatory losses
2. Replacements (Ongoing Losses)
•
providing for ongoing and additional losses that
occur during the course of therapy (surgery phases:
pre/intra/post operative)
The Balancing Act
 OUT (~1-1.6L/day for ave.
 IN
 Drinking
 Eating
 Metabolism

3mL/kg
 IV Fluids?
adult)
 Urine

12-15mL/kg/day
 Feces

3mL/kg
 Insensible losses

10-13mL/kg/day
With no unusual stresses or losses and normal renal
function intake can be balanced to outputs
Maintenance: Water and
Electrolyte Needs
 Replace Urine and insensible losses (1-2 L/day)
 Replace sodium and potassium loss
 Na: need 47-147 mEq/day (1-3mEq/kg/day)
 K: leak about 20mEq/day
Osmola
rity
(mOsm/
L)
Glucose
(gm/L)
Na+
(mEq/L)
K+
(mEq/L)
Cl(mEq/L)
0.9%
NS
308
154
154
½ NS
(.45%N
S)
154
77
77
Lactate
(mEq/L)
Ca++
(mEq/L)
Calculating Maintenance Dosing
 4-2-1 rule to calculate
 100-50-20 rule for daily
hourly rate
 In one hour, a person
needs:
requirements
 In one day a person
needs:
 4mL/kg for the first
 100 mL/kg for the first
10kg (0-10)
 2mL/kg for the next
10kg (10-20)
 1mL/kg for the
remaining kg (>20)
10kg
 50 mL/kg for the second
10kg
 20 mL/kg for the
remaining
 *Remember to divide by 24 for
hourly rate*
Maintenance Considerations
 Fever or high ambient temperatures
 Water loss increases by 100-150ml/day for every degree
above 37C
 Sweating
 Consider using a hypotonic solution for fluid
replacement (0.45% saline)
 Humidity
 Breathing humid air decreases loss while dry air may
increase relative losses
Example
Calculate maintenance fluids for a 75 kg patient who is NPO
 4-2-1 Rule
 10 x 4 = 40 mL
 10 x 2 = 20 mL
 55 x 1 = 55 mL
 Total 115 mL/hr
 100-50-20 Rule
 10 x 100 = 1000mL
 10 x 20 = 200 mL
 55 x 20 = 1100
 Sub total 2300mL/day
 Total 96 mL/hr
So you know how to calculate fluid
maintenance requirements but what
happens if the patient has an initial
deficit requiring rehydration other than
maintenance?
Think About It
A 50 kg patient comes into the ED with gastroenteritis
She has had vomiting and has diarrhea x 3days
What are you concerned about?
What do you want to do?
 Dehydration
 Electrolyte imbalance
 Decrease in blood pressure
 Administer medication for nausea
 Normalize Electrolytes
 Expand her intravascular volume
 Maintain normal fluid homeostasis
(maintenance)
 Replace lost fluid (resuscitation)
 Account for ongoing losses if present
(replacement)
Clinical Signs of Dehydration
Feature Mild
Moderate
dehydration dehydration
(<5%)
(5%-10%)
Heart
Normal
Slight
Rate
increase
Systolic Normal
Normal/
BP
orthostatic
Mucous Slightly dry Very dry
Mb
Urine
Decreased Olguria
Output
< 500ml/day
Severe
dehydration
(>10%)
Rapid, weak
Hypotension
Parched
Anuria
< 50ml/day
Clinical Signs of Dehydration
 This is an objective finding
 This is a rough estimate of fluid loss
 Clinical signs may not be evident in adults
 Adults are able to compensate better than children
 Calculation
 Fluid Deficits(L) = weight (kg) x % dehydration
 Example: Our 50 kg patient with 5% dehydration:
 50kg x 5%= 2.5L deficit
Estimate Deficit by Weight
Example: Suppose our gastroenteritis patient reports a 5lb weight
loss with illness
 Fluid and Weight
 1 L of fluid = 1 kg of
weight
 1kg= 2.2 lbs
 Use weight change to
determine fluid
loss/gain
Calculate his fluid deficit
5lb = 2.3kg =
= 2.3L fluid deficit
Fluid Deficits
 After deficit is determined
 Our pt has a 2.3L deficit by weight
 Replace half in 8 hours
 1,150mL/8hrs
=143mL/hr for the first 8 hrs
 Replace other half in the next 16 hours
 1150mL/16hrs
=72mL/hr for the next 16hrs
Total Flow Rate for Maintenance
•Add maintenance to deficit and you’ll have a flow rate
•Our 50kg patient with gastroenteritis has had a 5lb (2.3kg) weight loss
Maintenance
 4mL/kg x 10kg
= 40mL (0-10)
plus
 2mL/kg x 10kg
= 20mL (10-20)
plus
 1cc/kg x 30kg
= 30mL (20-50)
TOTAL maintenance= 90mL/hr
Deficit
 1,150mL/8hrs=143mL/hr for the
first 8 hrs
 1150mL/16hrs=72mL/hr for the
next 16hrs
Total Flow Rate
 For the first 8 hrs
 90mL/hr + 143mL/hr = 233mL/hr
 For the next 16 hours
 90mL/hr + 72mL/hr = 162mL/hr
Try it!
 A 176lb athlete presents to the ER after collapsing during
football practice. He weighed 184lbs at the beginning of
practice. Write an order for IV fluids to correct for deficit
and maintenance for the next 24 hours
Note: Use patients current weight to determine maintenance
Answer
Maintenance
176lb = 80kg
 40mL (0-10)
plus
 20mL (10-20)
plus
 60mL (20-80)
Deficit
184 - 176= 8lb = 3.6kg =3.6L =
3,600mL loss
 1,800mL/ 8 = 225ml/hr
• 225 + 120=
• 345 mL/ hr for the 1st 8 hrs
 1,800/16 = 112.5mL/hr
• 112.5 + 120 =
Total= 120mL/hr
• 232.5 mL/ hr for the next 16 hrs