Renal Fluid And Electrolyte Therapy

Front 1

Water is what portion of body weight?

Back 1

-50% of total body weight in females
-60% of total body weight in males

Front 2

Describe how total body water is broken down in a person

Back 2

-2/3 Intracellular
-1/3 Extracellular
-Cell membrane is freely permeable to water, but dissolved electrolytes do not share the same permeability

Front 3

Describe the breakdown of the extracellular water compartment

Back 3

-1/4 Intravascular
-3/4 Extravascular (interstitial)
-Distribution of IV fluids may be further restricted by the capillary membrane
-Isotonic saline can easily cross the capillary membrane and disperse throughout the extravascular (interstitial) space

Front 4

Describe the concept of third space

Back 4

-Acute sequestration in a body compartment that is not in equilibrium with ECF
-Not intra- or extracellular
-Refers to collection of fluid (usually isotonic) that is sequestered in potential spaces
-This situation is not normal and the fluid is derived from extracellular fluid
-Since this fluid accumulates under conditions when patients are ill and htereby are not able to take in enough fluids, IV replacement frequently becomes necessary to prevent/treat extracellular volume depletion
-Examples: Intestinal obstruction, severe pancreatitis, peritonitis, major venous obstruction, capillary leak syndrome

Front 5

What is the minimum amount of fluid required by a normal person in a day?

Back 5

This should equal obligate losses
Urine: 500 ml/day
Sweat and respiratory (insensible) losses: 500-1000 ml/day
Stool: 500 ml/day
Metabolism generates 300 ml/day

1-1.5 liters/day is sufficient to maintain a normal afebrile adult

Front 6

Describe the IV fluids that should be used to replace the normal fluids lost in a day

Back 6

-1/2 to 1/4 normal saline should be used
-Dextrose may be added to provide some nutrition
-Instillation of distilled water would cause hemolysis
-With fever the losses increase by approximately 100-150ml/degree C

Front 7

Describe the IV fluids used to replace fluid following sweating

Back 7

1/4 or 1/2 normal saline

Front 8

Describe the IV fluids used to replace fluid following NG suction (hypotonic)

Back 8

1/4 or 1/2 normal saline (K losses are significant too)

Front 9

Describe the IV fluids used to replace fluid following osmotic diuresis (hypotonic)

Back 9

-This can occur in uncontrolled diabetes
-1/4 to 1/2 normal saline
-K losses are significant

Front 10

Describe the IV fluids used to replace fluid following diarrhea (hypotonic)

Back 10

1/2 normal saline

Front 11

Describe the IV fluids used to replace fluid following third spacing (isotonic)

Back 11

Normal saline

Front 12

Describe the IV fluids used to replace fluid following bleeding (isotonic)

Back 12

Normal saline

Front 13

Describe the principles of treatment for fluid loss

Back 13

-How much volume?
-Need estimate of fluid deficit
-Which fluid?
-Which fluid compartment is predominantly affected?
-Need evaluation of other acid/base/electrolyte/nutrition issues

Front 14

Describe Ringer's lactate

Back 14

-Contains K, HCO3, Mg, Ca
-Giving it to a patient with renal failure may cause hyperkalemia

Front 15

Describe the distribution of 1 L of isotonic saline

Back 15

-Isotonic (normal, 0.9%) saline is distributed in extracellular fluid since the cell membrane is not permeable to Na
-1 L of NS distributes 250ml intravascular, 750ml interstitial

Front 16

Describe the distribution of 1 L of 5% dextrose

Back 16

-Solutions containing dextrose in water are handled like free water (although dextrose enters cells, it is metabolized)
-1L will lead to 60ml intravascular, 240ml interstitial, 700ml in cells
-Not effective for treatment of shock

Front 17

Describe the distribution of 1L of 5% albumin

Back 17

-Will remain in the intravascular space
-Most efficient way to treat shock
-Effect not permanent and in patients who are hypoalbuminemic (cirrhosis, nephrotic syndrome) albumin eventually enters the interstitial space because the integrity of the capillary barrier is not intact

Front 18

Describe the outcomes of use of albumin and saline in the ICU for fluid resuscitation

Back 18

-Outcomes of 4% albumin and normal saline for fluid resuscitation is similar

Front 19

Describe total body water volume deficits

Back 19

-Water loss (dehydration)
-Depletes all compartments equally leading to hypernatremic dehydration
-Common examples include diabetes insipidus, osmotic diuresis (uncontrolled hyperglycemia), osmotic diarrheas
-A tendency towards hypernatremia is usually follwed by intense thirst and rapid restoration of the fluid deficit
-When access to free water is restricted (demented or ventilated patients), hypernatremic dehydration develops

Front 20

Describe extracellular volume deficits

Back 20

-Salt and water loss, Third spacing
-May lead to depletion of extracellular fluid
-Examples include secretory diarrhea, ascities, edema, burns, diuretic therapy, third spacing

Front 21

Describe intravascular fluid loss

Back 21

-Seen in acute hemorrhage

Front 22

Describe the clinical diagnosis of dehydration

Back 22

-Free water deficit
-Thirst and hypernatremia may be the only manifestions

Front 23

Describe the clinical diagnosis of intravascular depletion

Back 23

-Hemodynamic effects are predominant
-Initially postural hypotension, then supine hypotension
-Flat jugular veins
-Sympathetic stimulation leads to peripheral vasoconstriction and decreased auxiliary sweating and dry mucus membranes

Front 24

Describe the clinical diagnosis of extracellular fluid depletion

Back 24

-A decrease in body weight precedes physical signs such as decreased skin turgor and sunken eyeballs
-With ongoing losses, hemodynamic effects supervene

Front 25

Describe the consequences of shock

Back 25

-If extracellular volume deficits not restored, it can lead to a drop in BP and organ dysfunction
-May be associated with parenchymal damage if prolonged and severe
-Acute tubular necrosis
-Watershed CNS infarction
-"Shock" liver
-Ischemic colitis

Front 26

Describe the clinical diagnosis of dehydration

Back 26

-Free water deficit
-Thirst and hypernatremia may be the only manifestions

Front 27

Describe the clinical diagnosis of intravascular depletion

Back 27

-Hemodynamic effects are predominant
-Initially postural hypotension, then supine hypotension
-Flat jugular veins
-Sympathetic stimulation leads to peripheral vasoconstriction and decreased auxiliary sweating and dry mucus membranes

Front 28

Describe the clinical diagnosis of extracellular fluid depletion

Back 28

-A decrease in body weight precedes physical signs such as decreased skin turgor and sunken eyeballs
-With ongoing losses, hemodynamic effects supervene

Front 29

Describe the consequences of shock

Back 29

-If extracellular volume deficits not restored, it can lead to a drop in BP and organ dysfunction
-May be associated with parenchymal damage if prolonged and severe
-Acute tubular necrosis
-Watershed CNS infarction
-"Shock" liver
-Ischemic colitis

Front 30

Describe calculation of water deficit

Back 30

-Basis of calculating free water deficit lies in the fact that the product of osmolality and volume in extracellular fluid is constant
-When there is loss of free water, there is an increase in extracellular fluid osmolarity (reflected in serum sodium)
-Known parameters: Current serum Na, Current body water, Serum Na in normal circumstantces
-PNa*volume(healthy)=Pna*volume(dehydrated)
-The water deficit is the difference between healthy and dehydrated water content

Front 31

Describe what happens in cirrhosis

Back 31

-There is intravascular volume depletion because Starling forces are reversed:
-Increased portal vein (hydrostatic pressure)
-Decreased colloid osmotic pressure from hypoalbuminemia
-Althrough intravascular volume depleted, saline will cause temporary restoration of intravascular volume
-In a short time, this saline will extravasate into ascetic fluid and worsen peripheral edema
-Intravenous albumin is effective transiently as the half life in cirrotics is markedly reduced