fluid compartments and fluid shifts Flashcards
kidneys maintain body fluids by
changing volume and composition
fluid intake per day
2300 mls per day 200 from synthesized carbs and 2100 from ingested fluids
fluid loss output
2300 mls insensible loss (700) sweat (100) feces (100) urine (1400)
normal body fluid weight man vs woman
60% vs 50% (more fat)
extracellular fluid percent of bodyweight and volume of fluid
20% of body weight 1/3 total volume
interstitial fluid percentage of ecf
75%
transcellular fluid percent of ecf
25% 1-2 liters
transcellular fluids
Synovial Peritoneal Pericardial Intraocular Cerebrospinal
intracellular fluid
40% of body weight 2/3 of total volume
know ionic concentrations
know non electrolytes of plasma concentrations
ions that have most osmotic effect
Na Cl
1 osmole =
1 mole of particles (6.02 x10^23)
Each mOsm of solute that cannot cross the membrane will generate
19.3 mmHg
Small changes in the concentration of impermeable solute will create
large shifts of water creating large changes in compartment volumes
.9% Na Cl solution equals
.9 grams of NaCl per 100 mls solution = 9 grams/L
Isosmotic:
Solutions with same osmolarity as intracellular
osmolarity even if some solute is permeable
Hypo-osmotic
Solutions with lower osmolarity than intracellular fluid even if some solute is permeable
Hyperosmotic
Solutions with higher osmolarity than intracellular fluid even if some solute is permeable
causes of fluid imbalance
Water ingestion Dehydration Fluid loss from gastrointestinal tract Abnormal fluid loss by sweating or kidneys
adding normal saline to blood
Osmolarity of solution same as ECF
No change in ECF osmolarity Expand volume of ECF by volume
of solution
Add 1 liter – the liter starts in the plasma of the CBV within 15 minutes 75% will move to the Interstitial fluid – 25% will remain in the CBV
adding a hypertonic solution
Osmolarity of solution higher than osmolarity of ECF so ECF osmolarity will increase
Osmolarity of ECF > than osmolarity of ICF so water moves from ICF to ECF
Overall increase in osmolarity ECF volume increases (more than
the volume added) ICF volume decreases
Most of the sodium and chloride remains in the ECF
ecf volume distribution
bodyweight times .2
icf volume of distribution
bodyweight times .4
starting mosm of ICF and ECF
7840,3920
steps in calculating fluid shifts
1) Determine starting volumes, concentrations, & total mOsm
2) Determine initial change to ECF
3) Determine NEW overall osmotic concentration
4) Determine new volumes based on new osmotic concentration
adding hypotonic
Osmolarity of solution lower than osmolarity of ECF so ECF osmolarity will decrease
Osmolarity of ECF < than osmolarity of ICF so water moves from ECF to ICF
Overall decrease in osmolarity ECF volume increases ICF volume increases
Can use the same process to calculate changes when adding a hypotonic solution
nutrient solutions
Glucose most common All usually adjusted to (or nearly to) isotonic
If not, given slowly so does not upset balance As nutrient metabolized patient often left with
surplus of water Usually removed via kidneys
NaCl account for _ amount of solute in ECF
90%
hyponatremia Caused by loss of sodium from ECF effect
Decrease in plasma [Na+] Decreased ECFV Increased ICFV
hyponatremia Caused by loss of sodium from ECF causes
Diarrhea & vomiting Diuretic overuse (inhibit ability to conserve sodium) Renal disease that “wastes” sodium
Addison’s disease results from decrease secretion of aldosterone
Hyponatremia
Caused by addition of excess water to ECF effects
Decrease in plasma [Na+] Increased ECFV Increased ICFV
Hyponatremia
Caused by addition of excess water to ECF causes
Excess water retention Excessive secretion of antidiuretic hormone
Consequences of Hyponatremia
Cell swelling – cerebral edema is major problem Symptoms: headache; nausea; lethargy;
disorientation
Significant problems as concentration falls into the 120 to 115 mE/L range
Significant brain swelling
Seizures
Coma
Permanent brain damage (if brain volume increases by more than 10%)
Death
Brain attempts to compensate by moving sodium, chloride, potassium, organic solutes from cells out to ECF
Have to be careful when treating not to correct too quickly [10 to 12 mmol/L over 24 hours]
Most common electrolyte disorder (15 to 25% of hospitalized patients)
Hypernatremia Caused by water loss from the ECF effect
Increased plasma [Na+] Decreased ECFV Decreased ICFV
hypernatremia Caused by water loss from the ECF Causes:
Inability to secrete antidiuretic hormone (needed for urine concentration) – produce large amounts of dilute urine (diabetes insipidus)
Excessive sweating so output greater than intake
Hypernatremia
Caused by addition of excess sodium to ECF
Effect:
Increased plasma [Na+] Increased ECFV Decreased ICFV
Hypernatremia
Caused by addition of excess sodium to ECF Causes:
Excessive secretion of aldosterone Reabsorb water and sodium
Consequences of Hypernatremia
ssue cells shrink
Not as common as hyponatremia and requires very high sodium concentration (158 to 160 mEq/L) since high sodium concentrations result in intense thirst
Patient’s with hypothalamic disease have an impaired thirst reflex
Slow correction best
Intracellular Edema causes
Major causes
Hyponatremia
Depression of metabolic systems within cells Sodium-potassium pump – shift of sodium into the cell
Lack of adequate nutrition delivery to cells
Inflammation Increased cellular permeability – shift of sodium into cell
Extracellular Edema Causes
Abnormal leakage of fluid from plasma to interstitial space across capillary
Most common form created by increased capillary filtration Failure of lymphatics to return fluid from interstitial
space to vascular system
