Fluids and electrolytes Flashcards
What are the components of total body water?
ICV = 2/3 (main electrolytes = potassium and phosphate)
ECV = 1/3 ( main electrolytes = Sodium and Chloride)
TBW ~ 60% of lean body mass
What function helps maintain resting membrane gradient?
Na + K + ATPase pump - transport sodium into ECV
What is the daily fluid volume required to maintain TBW homeostasis?
25- 35ml/kg per day or 2-3L/day
What components make up ECV?
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)
what pressures are account for in Starling forces?
1) Capillary Hydrostatic pressure
2) Interstitial oncotic pressure
3) Interstitial fluid pressure
4) Plasma oncotic pressure
Capillary hydrostatic pressure
intravascular BP = force of CO and vascular tone
**Increases capillary hydrostatic pressure and interstitial oncotic pressure –> favor FILTRATION (fluids out to interstitial space)
Interstitial fluid pressure
-Hydrostatic pressure of the interstitial space
**Increases Interstitial fluid pressure and plasma oncotic pressure –> favor ABSORPTION (fluids goes into intravascular space)
Plasma oncotic pressure
-Osmotic force of colloidal proteins (i.e. albumin)
***Increases Interstitial fluid pressure and plasma oncotic pressure —> favor ABSORPTION (fluids goes into intravascular space)
Interstitial oncotic pressure
-Osmotic force of colloidal proteins (albumin) within interstitial space
***Increases plasma hydrostatic pressure and interstitial oncotic pressure –> favor INFILTRATION (fluids out to interstitial space)
What factors affect fluid filtration?
Increased in these factors
1) Capillary hydrostatic pressure
2) Interstitial oncotic pressure
3) filtration coefficient
What factors affect fluid absorption?
Increased in these factors:
1) Interstitial fluid pressure
2) Plasma oncotic pressure
What are the effects of net filtration?
-Positive net filtration = Fluid filtrate out to tissue
-Negative net filtration = fluid absorb into vasculature
What is the constant fluid filter rate?
2ml/min
Lymphatic system carries fluids back into the interstitial space –> under euvolemic conditions, net fluid filtration ~ equal to lymphatic flow
What is the difference of net filtration between arterial and venous capillary beds?
Positive at the arterial end
Negative at the venous end
What is glycocalyx ?
-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
how and why glycocalyx repel blood components?
-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
How does glycocalyx affect net infiltration?
- binds to Albumin
-preserve capillary oncotic pressure and decrease capillary permeability to water —> effects plasma hydrostatic pressure on net filtration
How does glycocalyx affect inflammatory processes?
-contain inflammatory mediators –>prevent leukocyte adhesion excepts when acute inflammation or endothelial damage occurs
What are other function of the glycocalyx?
1) scavenging of free radicals
2) binding and activation of coagulation factors
3) signal transduction that regulate local vasoactive responses to mechanical stress
What are the main electrolytes of ECV?
Sodium and Chloride
What are the main electrolytes of ICV?
Potassium and Phosphate
the RAAS
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
RAAS
what is the main function of Anti Diuretic Hormone?
-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
What is the effect of ADH on the kidney?
ADH causes AQUAPORIN channels within the kidney to reabsorb water –> reserve volume–> increase urine concentration and osmolality
How does ADH help to increase BP?
-ADH is a potent arterial vasoconstrictor
Stimulate when detected by baroreceptors in the atria, aorta, and carotids during hypotension conditions
What stimulate the release of Atrial Natriuretic peptide (ANP)?
-Stretch receptors in the atrial walls stimulate the ANP from cardiac myocytes when there is increased in preload or hypervolemic states
How does ANP affect the Blood volume?
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
What happen to ANP in hypotension?
atrial receptors inhibit ANP
what is the percentage of daily water fluctuation?
0.2% of TBW
Why give isotonic crystalloid?
1) hydration of ECV
2) restoring water and electrolyte homeostasis to both intravascular and interstitial spaces
Why give crystalloids?
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
why isotonic crystalloids are disadvantage?
-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
What patients population are preferrable options using NS?
-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
What acid-base imbalance will occur when 0.9% NS for fluid resuscitation?
-Hyperchloremic metabolic acidosis
What are the negative effects of hyperchloremia?
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
when to use hypertonic solutions?
-Trauma/head injured patients –> promot volume expansion that draw fluids back into the intravascular space –> reduce intracranial HTN
Risks when using hypertonic solutions
-vascular irritation
-sudden fluid shift into intravascular space –>dehydration of neural cells –> osmotic demyelination syndrome
Why LR is not good for Diabetic patients?
LR contains sodium lactate as the buffer agent –> gluconeogenesis in diabetic patients due to byproduct metabolism of lactate
Why 0.9% can cause acid-base imbalance?
- Plasma concentration of sodium is higher than chloride
-Using 0.9% NS as fluids resuscitation –> hyperchloremic state –> Metabolic acidosis
