Fluid Assessment and Balance

Question 1

How is total fluid requirement determined?

Answer 1

Total requirement = maintenance + deficit + ongoing loss

Question 2

Average healthy adult daily water requirement / loss sites?

Answer 2

Average adults needs 2.5L/d
Loss to:
-200mL/d GI
-800mL/d insensible (resp, perspiration)
-1500mL/d urine (caution w/ renal failure)

Question 3

Conditions increasing fluid requirement?

Answer 3

• Fever
• Sweating
• GI loss (NGT/ V / D)
• Adrenal insufficiency
• Hyperventilation
• Polyuric renal disease

Question 4

Conditions decreasing fluid requirements?

Answer 4

• Anuria / oliguria
• SIADH
• Highly humidified atmospheres
• CHF

Question 5

How are the maintenance requirements for crystalloids calculated?

Answer 5

4: 2:1 rule =
- 4mL/kg/h ==> 1st 10kg
- 2mL/kg/h ==> 2nd 10kg
- 1mL/kg/h ==> thereafter

Question 6

What are the maintenance requirements for electrolytes for average person?

Answer 6

Na+: 3mEq/kg/d

K+ : 1mEq/kg/d

Question 7

What are the signs and symptoms of mild dehydration?

Answer 7

Mild = 3% water loss

• Decreased skin turgor
• sunken eyes
• dry mucous membranes
• dry tongue
• reduced sweating

Question 8

What are the signs and symptoms of moderate dehydration?

Answer 8

Mod = 6% water loss

• Oliguria
• Orthostatic hTN
• tachycardia
• low volume pulse
• cool extremities
• reduce filling of peripheral veins and CVP
• Haemoconcentration
• apathy

Question 9

What are the signs ad symptoms of severe dehydration?

Answer 9

Severe = 9% water loss

• Profound oliguria / anuria
• Compromised CNS function w/ or w/o altered sensorium

Question 10

Sources of ongoing fluid loss?

Answer 10

• Tubes: Foley catheter, NGT, surgical drain
• 3rd spacing (pleura, GIT, retro-/peritoneal); evaporation via exposed viscera, burns
• ongoing loss due to surgical exposure and evaporative losses

Question 11

Do IV fluids alter O2 perfusion capacity?

Answer 11

NO. Improve perfusion but NOT O2 carrying capacity of blood.

Question 12

What is crystalloid?

Answer 12

Salt-containing solutions that distribute within the ECF

Question 13

Replacement with crystalloid to maintain euvolemia in pt with blood loss?

Answer 13

Replace 3:1

Question 14

What should be used if large volume replacement required?

Answer 14

Balanced fluids e.g Ringer’s lactate (too much NSal may lead to hyperchloremic metabolic acidosis)

Question 15

What is colloid?

Answer 15

-Includes protein colloids (albumin and gelatine solutions) and non-protein colloids (starches e.g. hydroxyethol starch/HES and dextrans)

Question 16

Where do colloids distribute?

Answer 16

Within the ICF

Question 17

Replacement with colloid in blood loss?

Answer 17

1:1 (to replace intravascular volume)

Question 18

What must you monitor for with large volume colloid infusions?

Answer 18

Coagulopathy

Question 19

Describe the extracellular volume environment

Answer 19

• Sodium and Chloride
• Environment supports intracellular osmolality, cell membrane transport and delivery of nutrients and removal of waste (circulation)

Question 20

Describe the intracellular volume environment

Answer 20

• Potassium, organic anions

- Environment supporting intracellular function and cell membrane transport

Question 21

What percentage of body weight is total body water?

Answer 21

Total body water ~60% body weight

Question 22

Percentage of TBW in ECF volume?

Answer 22

33% TBW

Question 23

Primary influence on ECF volume?

Answer 23

ECF primarily varies with osmolar (Na+ and Cl-) content.
Subject to intake less than excretion.
i.e. LOW Na+ Content = LOW ECV; HIGH Na+ = HIGH ECV

Question 24

Percentage of TBW in ICF?

Answer 24

66%

Question 25

Primary influence on ICF volume? WHY?

Answer 25

Intracellular osmolarity held fairly constant (i.e. K+, organic anions)
ICV varies when water intake

Question 26

How is ECV assessed?

Answer 26

• Hx (abn intake/excretion)
• Oedema / CV exam
• Urine concentration / [Na+]

Question 27

Water shifts following loss of sodium rich fluid (e.g. diarrhoea)

Answer 27

ECV deplete: 
-low BP
-tachycardia
-peripheral vasoconstriction
-low urine sodium
-concentrated urine
ICV UNCHANGED

Question 28

What is the cause of low osmolality / sodium?

Answer 28

Water intake greater than ability to excrete (N = 20L/d)

Question 29

What are the causes of low plasma osmolality / sodium?

Answer 29

• Increased ADH
• Decreased distal tubule flow (decreased renal perfusion)
• Other tubular factors (limiting free water excretion)
• Drugs (with variable contributions from above factors): diuretics, carbamazepine, antidepressants (SSRis 12%)