Fluids & Electrolytes Flashcards
fluid changes with age
- lose % of body wight as we age
- both sides of spectrum at risk for dehydration
- thirst drive decreases with age
osmosis
water moves from high water concentration to low water concentration
diffusion
particles move from high particle concentration to low particle concentration across semi-permeable membrane
active transport
ATP requires
Na-K pump
regulation of fluid balance
- thirst (main)
- hypothalamus
- thirst centre
antidiuretic hormone (ADH)
- opposite of diuretics; holds onto fluid
- made in hypothalamus in response to concentrated fluids —> released from pituitary and acts on renal tubules—> water reabsorbed to increase fluid volume
- opposite occurs if fluid in vascular space is dilute
nervous system regulation of fluids
baroreceptors sense change in pressure and decrease in CO —> SNS increases HR resulting in peripheral vasoconstriction —> vasoconstriction in renal arteries results in decreased glomerular filtration, decreased urine output and increased BV
increase HR for vasoconstriction to decrease urine output and increase BV
renin-angiotensin-aldosterone
- decreased BV = decreased renal perfusion = kidneys secrete renin
- renin acts on angiotensin to cause vasoconstriction = increased BP and renal perfusion
- kidneys retain Na and water increasing BV
H2O follows…
Na
cortisol
- released in stress response
- increases BG
- causes increased Na and fluid retention
- cause of fluid retention post op
kidneys
- primary organ in F&E
- adjusts urine volume to maintain balance
- urine specific gravity = hydration status
- 1.5L of urine in 24hrs
tonicity
- concentration of solutes/particles (in bag)
- determines where fluid will go
tonicity categories
- isotonic
- hypertonic
- hypotonic
isotonic IV solutions
- N/S, R/L, 2/3 & 1/3
- tonicity similar to plasma
- remains in vasculature
normal saline
0.9% NaCl
ringers lactate
closest to plasma
2/3 & 1/3
2/3 dextrose 1/3 saline
hypertonic IV solutions
- D5S, D5 1/2 N/S
- osmolality > plasma
- pulls fluid from cells into vasculature
- decreases post op edema and increase urinary output
- risk for fluid overload
- will increase BP
D5S
5% dextrose in N/S
D5 1/2 N/S
5% in 0.45% N/S
total parenteral nutrition
- TPN
- very hypertonic solution
hypotonic IV solutions
- 1/2 N/S, D5W
- osmolality < plasma
- pulls fluid from vasculature into cells/interstitial spaces
- hydrates cell while decreasing fluid in circulatory system
- risk of cardiovascular collapse as decrease volume in vessles
- risk of cells swelling and bursting (ICP)
forces within capillaries
- hydrostatic pressure
- osmotic/colloid pressure
hydrostatic pressure
- blood pumping forcing fluid/nutrients into interstitial space
- higher at arterial end
osmotic/colloid pressure
- created by plasma (albumin)
- pulls fluid from interstitial space into venous end of capillaries
- proteins pull fluid back to vessel at venous end
most common abnormal fluid shift
intravascular to interstitial space
abnormal fluid shifts
- intravascular to interstitial space
- trauma, burns, massive infection
- compression stockings
intravascular to interstitial space fluid shift
- edema when hydrostatic P increases in vessles
- decrease in plasma oncotic P - pull created by albumin not enough to draw fluids back into capillaries
- high BP and low albumin —> fluid shifts without enough albumin to pull fluid back in
causes of low albumin (plasma proteins)
- excessive protein loss
- poor nutrition (low intake)
- deficit protein synthesis by liver
causes of intravascular to interstitial space fluid shift
- fluid overload
- CHF
- surgery
- liver failure
- obstruction of venous return to heart
1st spacing
normal distribution of fluid in ICF and ECF
2nd spacing
abnormal accumulation of interstitial fluid (edema)
3rd spacing
- fluid accumulation in part of body where it is not easily exchanged with ECF
- fluid shifts into abnormal areas and body retains it
- eventually start to diuresis and lose fluid
trauma, burns, and massive infection fluid shift
- damage to capillary walls
- albumin collects in interstitial space
- albumin pulls fluid from vessels to interstitial spaces
- fluid lost to effective circulating volume = relative hypovolemia - fluid still in body but not effective
compression stocking fluid shift
- increases tissue hydrostatic P
- forces fluid from interstitial space to vessels
- decreases peripheral edema
- increases fluid available to circulation
dealing with fluid shifts
- IV colloids
- Mannitol
IV colloids
- albumin, volumen, pentaspan, dextran
- synthesis volume expanders
- increase BP and renal perfusion
- used if not responding to fluid bolus or cant tolerate it
mannitol
- med given to decrease ICP
- pulls fluid out of brain cells
hyperglycaemia and fluid shifts
- pulls H2O from cells
- dehydrates cells
BP fluid balance assessment
- fluid deficit = decrease in systolic and pulse pressure
- fluid excess = increase in systolic and pulse pressure
- change in BP late sign in children
HR fluid balance assessment
- fluid deficit = increased rate, weak, thready
- fluid excess = increased rate, strong, full, bonding
respiration fluid balance assessment
- fluid deficit = normal (12-20)
fluid excess = tachypnea, moist lung sounds, crackles
intake/output fluid balance assessment
- fluid deficit= decreased urine output, concentrated during, amber colour
- fluid excess = intake > output
24 hr fluid balance assessment
- fluid deficit = intake < output; - fluid balance
- fluid excess = intake > output; + fluid balance
edema fluid balance assessment
- fluid deficit = rare
- fluid excess = dependent, extremities, face, sacral area, cites, anascara
weight fluid balance assessment
1kg = 1L
- fluid deficit = loss
- fluid excess = gain
skin turgor fluid balance assessment
- fluid deficit = poor
- fluid excess = taut
jugular vein (JVP) fluid balance assessment
- fluid deficit = flat
- fluid excess = distended
urine specific gravity fluid balance assessment
- fluid deficit = increase/high, concentrated urine, high osmolality
- fluid excess = decrease/low, dilute urine, low osmolality
calculating fluid requirements
- 100ml for first 10kg
- 50 ml for next 10 kg
- 20ml for remaining kg
fluid balance assessment (8)
- ins/outs
- 24hr fluid balance (+/-)
- 30ml/hr urine output = renal perfusion
- chest/respiratory
- edema
- vitals
- wound drainage/GI losses
- electrolytes, Hbg, hematocrit
sodium
Na+
- primary extracellular cation
- serum Na reflect H2O/Na ratio
- imbalance r/t Na & H2O increase/decrease
functions of Na
- neuromuscular - transmits/conducts nerve impulses
- body fluid - controls extracellular osmolality
- cellular - Na pump (Na into cells K out of cells)
- large amount in saliva, pancreatic, GI, intestinal secretions, bile, & sweat
hyponatremia (8)
- low Na
- N&V
- headache
- confusion
- decreased energy, drowsy, fatigue
- restless/irritable
- muscle weakness, spasm, cramps
- seizures
- coma
hypernatremia (7)
- high Na
- muscle weakness
- restless/irritable
- extreme thirst
- confusion
- lethargy
- seizures
- unconsciouness
potassium
K+
- primary intracellular cation
- conducts nerve impulses
- skeletal & smooth muscle
- small margin
- contraction of myocardium
- increase/decrease can cause arrhythmia
- increased in renal failure
hypokalemia causes (6)
- low K+
- stress of surgery
- K wasting diuretics
- hyperglycaemia = osmotic diuresis = K+ loss
- acidosis = H+ enters cells K+ lives cells
- GI losses
- poor nutrition
stress of surgery and hypokalemia
- adrenal cortex releases aldosterone
- conserves Na and excretes K+
- post op usually IV with K+
potassium replacements
- food (bananas, citrus fruits, dried fruits, meats, veggies, nuts, potato skin)
- Meds micro K, slow K, IV K
- never give IV K direct push as can = cardiac arrest; give over 1hr
clinical concerns with hypokalemia
- cardiac arrhythmia/arrest
- too high = cardiac irritability
- too low = weakened contraction
- in renal failure; acidosis
- med kayexalate binds with K to excrete
calcium
Ca++
- 99% in bones/teeth; 1% in serum/tissue
- vitamin D needed to absorb from GI tract
- contraction of cardiac, smooth, and skeletal muscle
- important for coagulation
- regulated by parathyroid gland hormone and calcitonin
hypocalcemia (5)
- low Ca
- renal failure; low albumin
- thyroid & parathyroid surgery
- tingling lips/extremities
- Chvosteks & Trousseaus signs
- give CaCl or carbonate
hypercalcemia
- high Ca
- metastatic CA
- causes bones to release Ca
- treatment = hydration & meds
- renal calculi (kidney stones)
- foods
magnesium
Mg++
- important in CHO & protein metabolism
- influences neruomuscular activity
- if K & Ca low then Mg low too
- PPIs decrease Mg
magnesium effects of muscle activity
- low = increased neuromuscular activity = tremors, seizures, cramps
- high = decreased tendon reflexes, sedative effect on neuromuscular system
phosphate
PO4 3-
- primary anion in intracellular fluid
- essential to function of muscles, RBC, NS
- need adequate renal function to maintain levels
- when Ca high PO4 low
- increased in renal failure
- decreased in malnutrition and alcohol withdrawal
potassium values
normal range 3.5-5.0 mol/L
hemoglobin values
normal range 115-155g/L
