Fluid and Electrolyte Balance
Terms
undefined, object
copy deck
- 60% of the body's weight is made up of what? water
- Water
- What are the three compartments that water is stored in in the body?
- The intracellular, the extracellular and as a component of blood
- What is interstitial fluid responsible for?
- A medium for exchange between the cell and the outside, how things enter and exit cells
- Osmolarity
- Total solute concentration in a solution- osmoles/liter
- Which is more dilute a solution with an osmolarity of 100 or a solution with an osmolarity of 200?
- 100
- Osmosis
- Net movement of water through a selectively permeable membrane that seperates two solutions with different solute concentrations.
- Elevated osmolarity is indicative of what?
- Increased solute (sodium) and decreased fluid (water)
- What are the two most important extracellular solutes?
- Sodium and protein
- What are the two most important intracellular solutes?
- Potassium and protein
- What would happen to a cell that has an intracellular osmolarity of 290 mOsM when it is placed in a solution with an osmolarity of 100 mOsM?
- It will swell because the solution with 100 mOsM has more water than the cell that has an osmolarity of 290 mOsM
- Where does all the exchange between plasma and interstitial space occur?
- The capillary level
- The goal of the body is to maintain what kind of osmolarity?
- Neutral
- What does isosmotic mean?
- Equal osmolarity
- What are the two components of extracelluar fluid?
- Plasma and interstitial fluid
- What is water directly regulated by?
- Antidiuretic hormone (ADH)
- What is water indirectly regulated by and how is it regulated?
- Aldosterone- because it regulates sodium and wherever sodium goes water follows
- What organs regulate water balance?
- Kidneys, GI tract, lungs, and to a lesser extent skin
- How is fluid balance regulated?
- By regulating intake (thirst) and output (kidneys)
- What we take in should be... (Equal to, less than, or more than)what goes out
- Equal to
- What pressure does the blood enter the capillary at?
- 32 mmHg- hydrostatic pressure
- As the blood moves through the capillary to the venous end hydrostatic pressure changes to what and why?
- It decreases to 15 mmHg because of the loss of fluid to the interstitial spaces- remaining plasma solutes because concentrated.
- At the venous end, the net flow of water is where?
- Back into the capillary due to the increased osmolarity of the plasma at the venous end
- What is the increased osmolarity of the plasma at the venous end due to?
- Retained protein in the plasma- it does not leave the capillary
- What is the most abundant plasma protein?
- Albumin
- What does albumin do at the venous end of the capillary?
- It draws fluid back in, and is responsible for the osmotic effect
- Are the hydrostatic and osmotic pressures equal? (Meaning does all the fluid that goes in return?)
- No
- The excess fluid from the difference in pressures goes where?
- Into the interstitial space
- What happens to this excessive fluid in the interstitial space?
- It is returned to circulation by the lympatic system
- Edema
- Excess fluid in the interstitial space and/or body cavities
- What is exudate rich in?
- Protein and blood cells
- What is exudate type edema normally seen in?
- Inflammation
- What is purulent exudate?
- Pus
- What is transudate made of?
- Little or no protein and very few cells, it is an ultrafiltrate of plasma and it has a water like consistency.
- What is transudate normally found in?
- Edema of right heart failure
- What is the primary mechanism for formation of a transudate?
- Increased pressure at the level of the capillary
-
True or False...
In transudate there is no vascular damage and there is no leakage of protein or cells into the interstitial space. - True
-
Transudate or exudate?
Increased hydrostatic pressure within blood vessels - Transudate
-
Transudate or exudate...
Increase permeability of the vessel wall - Exudate
- What would happen if there was low albumin concentrations?
- There would be nothing to pull the fluid back in so edema would result.
-
True or False...
Edema is usually multifactorial - True
- Edema caused by chronic heart failure is usually a combination of what?
- hydrostatic (HTN) and hypervolemic
- Pitting edmea in right heart failure is prominent where and why?
- In the lower extermities due to gravity
- After a mastectomy patients may suffer from persistant edema for life- why?
- Because in a mastectomy they take out the lymph nodes and therefore it is unable to drain anymore resulting in edema.
- What is the principal regulator of water intake?
- Thirst
- What is thirst regulated by?
- The osmolarity of the plasma
- What cells monitor the osmolarity of the plasma?
- Osmoreceptors
- Increased osmolarity of the plasma activates what?
- Neural pathways that result in the conscious perception of thirst.
- Why are diabetics always thirsty?
- Because there is an increased plasma osmolarity because of the increased glucose so the regulators are always being stimulated
- What are the two mechanisms in the kidney that regulate output?
- What is filtered at the glomerulus and what is reabsorbed or secreted by the tubules.
- The amount of fluid filtered by the glomerulus is a function of what?
- Hydrostatic pressure- the pressure of the pump
- What are the tubules of the kidney are important for?
- Reabsorption and secretion of substances- modifying the filtrate.
- What is modified in the filtrate?
- Both solute and water
- What hormones are involved in the regulation of fluid balance?
- ADH, aldosterone, and atrial natriuretic peptide
- Where is ADH produced and stored?
- Produced by the neurons in the hypothalamus and stored in the axon terminals of the posterior pituitary.
- Increased osmolarity of the plasma causes what in regards to ADH?
- Results in action potential within the hypothalamic neurons and release of ADH into the plasma
- Where does ADH bind once it has been released?
- A receptor on the collecting duct cell (Found only in the kidney)
- When ADH binds to the receptor what does this stimulate?
- the formation of membrane channels in the collection duct cells to increase permeability of water from the filtrate back to the plasma.
- Lack of ADH secretion results in what?
- Copious dilute urine
- What is the only hormone that directly regulates water?
- ADH
- Where is aldosterone secreted?
- The adrenal cortex
- What does aldosterone act on?
- The renal cortical collecting duct cells to promote the movement of sodium from the filtrate back into the blood
- Movement of the sodium from the filtrate to the blood will result in what?
- Increased water retention because water follows sodium
- Where does atrial natriuretic peptide come from and what causes it to be released?
- Atrial cells in the heart in response to increased stretch.
- Increased stretch of the heart is caused by what?
- Increased venous return to the heart, caused by excess fluid volume
- What does ANP promote?
- Water and sodium loss through the kidneys
- Why is it important that aldosterone is a steroid hormone?
- Because it is a lipid itself so it crosses the plasma membrane easily.
- Where is the receptor for the aldosterone hormone?
- In the nucleus
- What stimulates the release of aldosterone?
-
low plasma sodium/
high plasma potassium - Does aldosterone directly regulate plasma postassium concentration?
- yes
- What could cause hyperaldosterone secretion?
- tumor in the adrenal cortex causing hypokalemia
- Cardiac dysrhthmias from an inability of cells to conduct action potentials are associated with what electrolyte imbalance?
-
hypokalemia
(low plasma postassium) - What could cause hypoaldosterone secretion?
- Addison's disease causing hyperkalemia
- What electrolye imbalance usually results from kidney dysfunction, and also results in cardiac dysfunction from hypoaldosterone secretion?
-
hyperkalemia
(high plasma postassium) - When blood pressure drops, baroreceptors stimulate cells in the afferent arteriole to the kidney to release this.
- Renin
- A protein that acts like an enzyme and converts a plasma protein termed angiotensinogen into angiotensin I.
- Renin
- Angiontensin I is converted into angiontensin II, how?
- By an enzyme in the lung called the Angiotensin Converting Enzyme (ACE)
-
A potent vasoconstrictor, this causes an increase in peripheral vascular resistance thatt raises blood pressure.
It is a potent stimulus for the release of aldosterone. - Angiotensin II
- What is the purpose of stimulating the release of aldosterone with low BP, in general or low pressure through the kidney, specifically?
- To conserve water in order to increase plasma volume.
- What is one treatment for patients with fluid overload and hypertension?
- ACE inhibitors, diuretics
-
1.excretion of wastes
2.regulation of body water, sodium, potassium
3.pH
4.secretion of hormones - erythropoetin, renin, vitamin D - These are the 4 functions of the kidneys.
- What 2 major waste products are eliminated by the kidney?
-
Blood Urea Nitrogen (BUN)
Creatinine -
A nitrogen waste product that is the end result of protein and nucleic acid catabolism.Breaks down into ammonia.
Normal range: 6-19 mg/dl - Blood Urea Nitrogen (BUN)
-
A product of creatine metabolism in muscle.
Normal range is 0.5 - 1.4 mg/dl - Creatinine
-
1. vary the acidity of urine - normal pH ranges from 4.5 - 8.0
2. make and release into the interstitial space bicarbonate ion - 2 ways the kidney can help regulate pH
- What is the normal pH required in the ECF?
- 7.35-7.45
-
1. the bicarbonate system
2. phosphate and protein buffering systems - How does the body maintain pH?
- Kidney can excrete hiydrogen ion into urine and return bicarbonate to the ECF.
- One mechanism to add new bicarbonate into blood.
- H ion elevated/bicarbonate ion decreased.
- acidosis
- H ion decreased/bicarbonate ion elevated.
- alkalosis
- In COPD - pt. cannot blow off CO2 as fast as it is produced. What can this cause?
- respiratory acidosis
- When CO2 is removed faster than it is produced (like in hyperventilation), it can cause this.
- respiratory alkalosis
- In the kidney, H ion is secreted and K ion is conserved.
- acidosis
- In the kidney, H ion is retained and K is secreted.
- alkalosis
-
1. correction - the cause of the disturbance is repaired
2. compensation - physiological adjustments are made - 2 ways to return pH to normal
- kidney cells sense reduced O2 carrying capacity of blood and release this to stimulate the bone marrow to produce more red blood cells
- erythropoetin
- kidney activates this, which stimulates the GI tract to absord more dietary calcium
- vitamin D
- when blood pressure drops in the kidney, kidney cells release this, resulting in vasoconstriction, elevating BP
- renin
- elevated BUN and creatinine (from inability to produce urine)
- azotemia
- when azotemia becomes associated with clinical signs and symptoms, it is termed this.
- uremia (urine in the blood)
- prolonged signs and symptoms of uremia
- chronic renal failure (scarring/irreversible)
- kidney stone formation
- nephrolithiasis
-
a clinical syndrome in which kidneys are unable to excrete waste products frequently it is reversible
increased serum BUN and creatinine
caused by glomerular disease, ischemia, nephrotxicity, acute tubular necrosis - acute renal failure
-
characterized by destruction of tubular epithelial cells and clinically by acute suppression of renal function
most common cause of acute renal failure (when urine flow is <400 ml/day)
reversible
caused by ischemia from trauma, toxicity - acute tubular necrosis
-
1.initiation - 36 hours - decline in urine output, w rise in BUN/creatinine
2.maintenance - 3 weeks - urine output only 50-400 ml/day, fluid overload
3.recovery - take up to 6 mos. - steady increase in urine output - pt usually becomes anemic f - 3 stages of acute tubular necrosis
-
Urinary outflow obstruction by renal stones.
More common in makes.
Most important fator: increased urine concetration of the stone's constituents that exceed their solubility in urine. - urolithiasis
- characterized morphologically by contracted kidneys with red-brown color and diffusely granular appearance
- end-stage kidney disease
- What electrolye imbalance usually results from kidney dysfunction, and also results in cardiac dysfunction from hypoaldosterone secretion?
-
hyperkalemia
(high plasma postassium)