FEN: Fluid Management

Question 1

Describe distribution of total body fluid (TBF)

Answer 1

1. TBF = 60% lean body weight in men and 50% in women (about 42 L)
2. 60% TBF is IntraCellular, 40% is ExtraCellular
3. 75% of EC is InterStitial, 25% of EC is IntraVascular
4. This means 10% of TBF is IntraVascular

Question 2

Describe distribution of Normal Saline, Lactated Ringer and Normosol-R and Plasma-Lyte

Answer 2

1. 100% of Infused Volume stays in the ExtraCelular space
2. The volume distributes evenly across capillary membrane in the EC compartment. Na and Cl do not freely cross into cells.
3. 25% of EC is Intravascular
4. 1L infusion = 250 mL volume expansion

Question 3

Describe distribution of 5% dextrose

Answer 3

1. 5% dextrose in metabolized into free water and carbon dioxide
2. Free water distributes evenly across capillary AND cell membranes
3. 10% of total body fluid is intravascular
4. 1L infusion = 100 mL volume expansion

Question 4

Describe distribution of most colloids (packed red blood cells, pooled human plasma, semisynthetic glucose polymers (dextran), and semisynthetic hydroxyethyl starch (hetastarch)

Answer 4

1. Colloids are too large to cross capillary membranes, so they remain in intravascular space
2. Albumin 25% is a special case that does not follow this rule
3. 500 mL infusion = 500 mL volume expansion

Question 5

Describe distribution of albumin 25%

Answer 5

1. 25% albumin has an oncotic pressure about 5-fold that of normal plasma
2. This pulls water from other side of capillary, moving fluid from IS space to IV space
3. 100 mL infusion = 500 mL volume expansion

Question 6

What are components/amounts of total blood volume

Answer 6

1. Total blood volume is about 5 L
2. 3 L is plasma, which is EC fluid in intravascular space
3. 2 L is intracellular fluid within red blood cells

Question 7

What are the contents of Sodium chloride 0.9% (NS) (mEq/L of each component and total osmolarity)

Answer 7

1. Na 154
2. Cl 154
3. Osmolality: 308

Question 8

What are the contents of Lactated Ringer (LR) (mEq/L of each component and total osmolarity)

Answer 8

1. Na 130
2. Cl 109
3. K 4
4. Ca 3
5. Lactate 28
6. Osmolality: 273

Question 9

What are the contents of Normosol-R (mEq/L of each component and total osmolarity)

Answer 9

1. Na 140
2. Cl 98
3. K 5
4. Mg 3
5. Acetate 27/Gluconate 23
6. Osmolality: 295

Question 10

What are the contents of D5W (grams of dextrose and kcal)

Answer 10

1. 5 g of dextrose per 100 mL of water

2. This is about 17 kcal/100 mL

Question 11

D5W has the net effect of administering “free water.” What is a safety concern about it crossing into cells?

Answer 11

1. Many experts avoid adminsitering D5W whenever possible in patients with neurologic injury and elevated intracranial pressure (ICP) because it can cross into cerebral cells causing further elevation in ICP.

Question 12

Describe three safety concerns with hydroxyethyl starch (hetastarch)

Answer 12

1. Increased mortality in critically ill patients
2. Coagulopathy
3. Acute kidney injury

Question 13

Describe two safety concerns with dextran products

Answer 13

1. Coagulopathy

2. Kidney impairment

Question 14

List two causes of intravascular fluid depletion

Answer 14

1. Hypovolemic shock

2. Distributive (septic) shock

Question 15

List two complications of intravascular fluid depletion

Answer 15

1. Reduced cardiac function

2. Organ hypoperfusion

Question 16

When do signs or symptoms of intravascular fluid depletion typically occur?

Answer 16

1. When about 15% of blood volume is lost (e.g. hemorrhage) or shifts out of the intravascular space (e.g. sepsis)
2. Blood volume = 5 L, so 15% = 750 mL of blood volume.

Question 17

List 9 signs or symptoms of intravascular volume depletion

Answer 17

1. Tachycardia (HR > 100 bpm)
2. Hypotension (SBP < 80 mmHg)
3. Orthostatic changes in HR or BP
4. Increased BUN/SCr ratio > 20:1
5. Dry mucous membranes
6. Decreased skin turgor
7. Reduced urine output
8. Dizziness
9. Improvement in HR and BP after a 500-1000mL fluid bolus

Question 18

When is fluid resuscitation indicated?

Answer 18

Patients with signs or symptoms of intravascular volume depletion

Question 19

What is the goal of fluid resuscitation?

Answer 19

Restore intrasvascular volume depletion and prevent organ hypoperfusion

Question 20

What is a common fluid resuscitation strategy?

Answer 20

1. In sepsis: 30 ml/kg
2. 500-1000 mL fluid bolus of NS or LR
3. Reevaluate and repeat as long as signs and symptoms are improving

Question 21

Describe differences between crystalloids and colloids in time to achieve fluid resuscitation and patient outcomes

Answer 21

1. Colloids have not been shown to be superior

2. Colloids are associated with higher cost and some adverse effects (e.g. coagulopathy, kidney impairment)

Question 22

What is a reasonable role for colloids in fluid resuscitation

Answer 22

1. When fluid resuscitation with crystalloid (usually 4-6L) has failed to achieve hemodynamic goals OR
2. Clinically significant edema limits the further administration of crystalloid

Question 23

When should albumin be considered in the setting of fluid resuscitation

Answer 23

Albumin can be considered in patients:

1. Who have required a large volume of resuscitation fluids (e.g. crystalloids)
2. and have a low albumin concentration

Question 24

How to use albumin 25% in setting of clinically significant edema?

Answer 24

1. Patients who do not require fluid resusictation but may benefit from redistribution of fluid (ascites, pleural effusions, pulmonary edema causing respiratory failure)
2. Low albumin concentration
3. In conjunction with appropriately dosed diuretics that are ineffective alone

Question 25

What fluids are recommended for first line fluid resuscitation in HYPOVOLEMIA?

Answer 25

NS or LR are equal

Question 26

What fluids are recommended first line fluid resuscitation in surgery and trauma patients?

Answer 26

1. NS or LR

2. Historically LR is preferred in surgery and trauma but no evidence suggests superiority over NS

Question 27

Can LR be used in metabolic acidosis?

Answer 27

1. Lactate is metabolized to bicarbonate
2. However, lactate metabolism is impaired during shock
3. Therefore LR may be an ineffective source of bicarbonate

Question 28

Describe chloride-restrictive fluid resuscitation strategies in critically ill patients

Answer 28

1. NS has 154 mmol/L chloride while LR has 109 mmol/L, which is closer to normal physiologic (i.e. balanced)
2. In ICU patients, balanced fluids have lower rate of any cause of death, new renal replacement therapy and persistent renal dysfunction.
3. In non-ICU patients, there was no difference found in hospital-free days. A secondary outcome still showed better renal outcomes with balanced fluids.

Question 29

When are maintenance fluids indicated

Answer 29

When patients are unable to tolerate oral fluids

Question 30

What is the goal of maintenance fluids

Answer 30

Prevent dehydration and maintain a normal fluid and electrolyte balance

Question 31

What is a typical strategy for administering maintenance IV fluids?

Answer 31

1. Calculate daily volume requirement

2. Administer as a continuous infusion through a peripheral or central catheter

Question 32

Roughly how much water is required for an adult

Answer 32

20-40 mL/kg/day (adults only)

Question 33

What is the 4-2-1 method for daily volume requirement?

Answer 33

1. Administer 100 mL/kg/ for first 10 kg, followed by 50 mL/kg for the next 10 kg (i.e. 1500 mL for the first 20 kg), plus 20 mL/kg for every kg greater than 20 kg
2. It’s called 4-2-1 because you can divide into hourly rates, i.e. 4 ml/kg/hr for first 10 kg, followed by 2 ml/kg/hour for next 10 kg, plus 1 ml/kg/hr for every kg after 20.

Question 34

What is the most common maintenance IV fluid

Answer 34

1. D5W with 0.45% NaCl plus 20-40 mEq of potassium chloride per L (adjusted for the individual patient)
2. e.g. “D5W in 1/2 NS with 20 KCl”

Question 35

When an infusion of 150 mEq of Sodium bicarbonate is required, should it be added to NS?

Answer 35

1. 150 mEq of Sodium bicarbonate added to 850 mL of NS results in 1.6% sodium chloride.
2. Instead it is recommended to add the sodium bicarb to D5W or sterile water for injection instead of NS.