Fluids and electrolytes

Question 1

What are the components of total body water?

Answer 1

ICV = 2/3 (main electrolytes = potassium and phosphate)
ECV = 1/3 ( main electrolytes = Sodium and Chloride)
TBW ~ 60% of lean body mass

Question 2

What function helps maintain resting membrane gradient?

Answer 2

Na + K + ATPase pump - transport sodium into ECV

Question 3

What is the daily fluid volume required to maintain TBW homeostasis?

Answer 3

25- 35ml/kg per day or 2-3L/day

Question 4

What components make up ECV?

Answer 4

1) plasma (1/4 of ECV)

2) Interstitial (3/4 of ECV) - composed of extravascular fluid in the tissue spaces

3) transcellular fluids - include cerebrospinal fluid, synovial, GI secretions, and intraocular fluids (Isolated from fluid dynamics –> NON functional)

Question 5

what pressures are account for in Starling forces?

Answer 5

1) Capillary Hydrostatic pressure
2) Interstitial oncotic pressure
3) Interstitial fluid pressure
4) Plasma oncotic pressure

Question 6

Capillary hydrostatic pressure

Answer 6

intravascular BP = force of CO and vascular tone

**Increases capillary hydrostatic pressure and interstitial oncotic pressure –> favor FILTRATION (fluids out to interstitial space)

Question 7

Interstitial fluid pressure

Answer 7

-Hydrostatic pressure of the interstitial space

**Increases Interstitial fluid pressure and plasma oncotic pressure –> favor ABSORPTION (fluids goes into intravascular space)

Question 8

Plasma oncotic pressure

Answer 8

-Osmotic force of colloidal proteins (i.e. albumin)

***Increases Interstitial fluid pressure and plasma oncotic pressure —> favor ABSORPTION (fluids goes into intravascular space)

Question 9

Interstitial oncotic pressure

Answer 9

-Osmotic force of colloidal proteins (albumin) within interstitial space

***Increases plasma hydrostatic pressure and interstitial oncotic pressure –> favor INFILTRATION (fluids out to interstitial space)

Question 10

What factors affect fluid filtration?

Answer 10

Increased in these factors

1) Capillary hydrostatic pressure

2) Interstitial oncotic pressure

3) filtration coefficient

Question 11

What factors affect fluid absorption?

Answer 11

Increased in these factors:

1) Interstitial fluid pressure

2) Plasma oncotic pressure

Question 12

What are the effects of net filtration?

Answer 12

-Positive net filtration = Fluid filtrate out to tissue

-Negative net filtration = fluid absorb into vasculature

Question 13

What is the constant fluid filter rate?

Answer 13

2ml/min

Lymphatic system carries fluids back into the interstitial space –> under euvolemic conditions, net fluid filtration ~ equal to lymphatic flow

Question 14

What is the difference of net filtration between arterial and venous capillary beds?

Answer 14

Positive at the arterial end

Negative at the venous end

Question 15

What is glycocalyx ?

Answer 15

-composed of a matrix of

1) glycoprotein
2) polysaccharides
3) hyaluronic acid

-Binds to ionic side chains and plasma proteins to create physiologically barrier within vascular space

Question 16

how and why glycocalyx repel blood components?

Answer 16

-Acts a barrier that repels negative charged polar compounds and blood components -> prevent blood component adhesion to the vascular wall and augmenting LAMINAR blood flow

Question 17

How does glycocalyx affect net infiltration?

Answer 17

• binds to Albumin
  -preserve capillary oncotic pressure and decrease capillary permeability to water —> effects plasma hydrostatic pressure on net filtration

Question 18

How does glycocalyx affect inflammatory processes?

Answer 18

-contain inflammatory mediators –>prevent leukocyte adhesion excepts when acute inflammation or endothelial damage occurs

Question 19

What are other function of the glycocalyx?

Answer 19

1) scavenging of free radicals
2) binding and activation of coagulation factors
3) signal transduction that regulate local vasoactive responses to mechanical stress

Question 20

What are the main electrolytes of ECV?

Answer 20

Sodium and Chloride

Question 21

What are the main electrolytes of ICV?

Answer 21

Potassium and Phosphate

Question 22

the RAAS

Answer 22

Renin is released by juxtaglomerular cells from the kidneys when hypotension and systemic sympathetic stimulation detected by baroreceptors in the atria, aorta, and carotid and renal afferent arterioles

Question 23

RAAS

Answer 23

Question 24

what is the main function of Anti Diuretic Hormone?

Answer 24

-regulate water balance!!!

-When there is an increased in serum osmolality (detected by osmoreceptors in the hypothalamus), the posterior pituitary gland release ADH

***Hypothalamus also stimulate thirst

Question 25

What is the effect of ADH on the kidney?

Answer 25

ADH causes AQUAPORIN channels within the kidney to reabsorb water –> reserve volume–> increase urine concentration and osmolality

Question 26

How does ADH help to increase BP?

Answer 26

-ADH is a potent arterial vasoconstrictor

Stimulate when detected by baroreceptors in the atria, aorta, and carotids during hypotension conditions

Question 27

What stimulate the release of Atrial Natriuretic peptide (ANP)?

Answer 27

-Stretch receptors in the atrial walls stimulate the ANP from cardiac myocytes when there is increased in preload or hypervolemic states

Question 28

How does ANP affect the Blood volume?

Answer 28

1)ANP stimulates kidney to release sodium and water –> reduce blood volume, offloading the heart

2) Produce vasoactive responses in the afferent and efferent renal arterioles to increase GFR

3) inhibit release of renin and ADH

Question 29

What happen to ANP in hypotension?

Answer 29

atrial receptors inhibit ANP

Question 30

what is the percentage of daily water fluctuation?

Answer 30

0.2% of TBW

Question 31

Why give isotonic crystalloid?

Answer 31

1) hydration of ECV
2) restoring water and electrolyte homeostasis to both intravascular and interstitial spaces

Question 32

Why give crystalloids?

Answer 32

1) restoration of vascular volume
2) preservation of flow
3) decrease in hormone-mediated vasoconstriction
4) correction of plasma hyperviscosity d/t acute hemorrhage
5) Preferred for lack of allergenic potential

Question 33

why isotonic crystalloids are disadvantage?

Answer 33

-Evenly distributed –> expand plasma volume is transient
-low molecular weight –>hemodilution of plasma proteins and loss of capillary oncotic pressure —> 75-80% volumes goes into interstitial space

Question 34

What patients population are preferrable options using NS?

Answer 34

-0.9% saline is the least physiologic
-0.9% saline is preferred for patients at risk for cerebral edema
-NS is preferred for patients with anuria, and ESRD (NS does not have potassium)

• NS contains equal parts of sodium and chloride = isotonic crystalloid

Question 35

What acid-base imbalance will occur when 0.9% NS for fluid resuscitation?

Answer 35

-Hyperchloremic metabolic acidosis

Question 36

What are the negative effects of hyperchloremia?

Answer 36

1) decreased GFR (due to increased reabsorption of chloride on renal arteriolar vascular resistance)

2) impair renal regulation of bicarbonate

3) causes increased in salt and water retention –> hemodilution –> interstitial edema

Question 37

when to use hypertonic solutions?

Answer 37

-Trauma/head injured patients –> promot volume expansion that draw fluids back into the intravascular space –> reduce intracranial HTN

Question 38

Risks when using hypertonic solutions

Answer 38

-vascular irritation
-sudden fluid shift into intravascular space –>dehydration of neural cells –> osmotic demyelination syndrome

Question 39

Why LR is not good for Diabetic patients?

Answer 39

LR contains sodium lactate as the buffer agent –> gluconeogenesis in diabetic patients due to byproduct metabolism of lactate

Question 40

Why 0.9% can cause acid-base imbalance?

Answer 40

• Plasma concentration of sodium is higher than chloride
  -Using 0.9% NS as fluids resuscitation –> hyperchloremic state –> Metabolic acidosis