Electrolytes and IV Fluids Flashcards
total body water
what %
how much is extra and intracellular
types of extracellular
Total Body Water: % of water, or lean body weight of an individual
- varies with gender: males = more water because more muscle
- varies with age
- higher bpdy fat = less body water percentage
water stored as extra and intra
2/3rds of TBW is intracellular = within the cells
1/3 = extracellular
extracellular = plasma fluid (blood) = intravascular
extracellular = interstitial fluid (majority of extracellular water, between the vessels and the cell membranes)
Extracellular Fluid: typically 1/3 of TBW & this can vary based on amount of Na and water within the body
- the extracellular fluid cannoy cross intracellularlly freely, except pure water can cross membranes via osmosis
what are the major eletrolytes in the intracellular space
extracellular? (vessels and interstitum)
Intracellular
- K+ is major
- phosphate
- magnesium
- proteins
Extracellulat (in equal concentrations beterrn vessels and the interstitum)
- Na+
- Cl-
- Ca+ (calcium)
- bicarb
explain the concept of osmolality
how does the boyd regulalte osmolality
osmolality = ration of solutes and water
solutes = proteins and electrolytes
- attempt to be equal at all times
- a normal osmolality = 275-290
water will move via the process of osmosis in order to maintain equal concentrations (osmolality) between two areas
attempt to achieve = concentrations of solutes/solvent ratios inside the cell and outside the cell
approx. 290 in the human body
Regulation
- the body regulates osmolality via the hypothalmus and thirst hormone stimulates (ADH release to uptake water)
- the body also regulates osmolality via the kidneys and the renin release to trigger the RAAs system to increase volume (vasoconstrict and increase Na+ reabsorb and water reabsorb)
Role of Renin release from the kidneys and how it adjusts osmolality in the body
what are the triggers for renin release
- JG cells in the kidney (affernt arteriole): sense a drop in pressure to the kidneys - trigger renin to be released
- macula densa cells in the kidney (distal tubule) they sense the low amoutn of Na+ in the filtrate = release PGE1 (to try to increase pressure locally) which triggers renin
- a sympathetic nerve cell trigger due to a stressor (hemorrhage, etc.) - triggers renin release
renin then goes and activats the RAAS system which will trigger increased volume and sodium retention and increase BP
when delivering NaCl into the patient (via extracellular vessel repletion) what is it doing
NaCl = IV = into the extracellular fluid: specifically the intravascular fluid
- this will increase extravascualr fluid
- this will increase the osmolality of the ECF (becuase giving Cl and Na = which are solutes)
- this will shirnk the cells: because there is more solutes outside the cells now than inside, so overtime this may pull fluid out of the cell as it maintins its balance
- the cells will respond to this by exchanging water into the ECF to maintain their homeostatsis
so when giving NaCl = the cells are releaseing water to maintain proper osmolality and acheive equal osm levels
if too much NaCl is given, this resulrs in intracellular dehydration
explain the mechanism
if there is an increase in solutes intravascularlly: like NaCl given, there will be a higher osmolality outside the cells than inside the cells
so the cells will be dehydrated intracelllularl as they release thier water to balance out the osmolality
- this will trigger the release of ADH: to increased free water absorbtion to hold onto water
- this will trigger the thrist reflex in the hypothlamus to increase water intake
net result: the lack of water intracellularly triggers, the hypothalmus and ADH all to increase water resobrtion & infux = this in term increases water levels outside the cells & thus water can flow back INTO the cells to restore osmoliality
explain the mechanism of extracellular dehydration
when there is extracellular dehydration: there is a decrease in the solutes AND the water amounts : they’re leabing together
- so there is no NET CHANGE IN THE OSMOLALITy: just a change in volume osmolality still 290 because the solutes and teh water are freely leaving the extracellular space
RESULT - HYPOTENSION: loss of volume!!!
compared to intracellular: where only water could leaves solutes were stuck
if the osmolality does not CHANGE, ADH and hypothalmus will NOT be stimulated
instead; RAAS system will be stimulated!!! because the blodo volume/pressure will drop
this triggers the reuptake of solutes ad fluid through RAAS
when are IV fluids needed?
energy source
- in a fasting state: glycogen will only fuel thebody for 24 hours; need to give sugar to fuel via fluids
- starting IVF early on in the malnoursihed population can help decrease or delay the need for parenteral feeding (because you can provide energy via sugar)
Maintenance Fluids
- to replease an ongoing loss of water and electrolytes during normal conidtions of urine, sweat, respiration and stool
- the best tool to indicate if water balance is needed is teh Na level on the BMP
Replacement Fluids
- during water and electroyte losses from
- GI losses (diarrhea, vomiting)
- urinary losses
- skin losses (excessive)
- bleeding
- thrid-spacing (a shift from intravascualr to interstital fluids)
how much free water do pts. need?
what might increase their need for free water? decrease need?
formula for total daily water replacment for insensible and urinary losses
Free Water needs : typical pt. needs approx < 1 L of electrolyte free water
Those who may need more
- burn pts.
- fever
- polyuria/diarrhea pts.
Those who may need less
- edematous
- hypothyroid (slow metabolism)
- SIADH: those impropering releasing ADH and inc. fluid level
- humidified air (those on it?)
Holliday_Segar Formula
- approx. 100mL/100kcal/day : thus for every 100kcal burned the pt. needs 100 mL of fluid
this is maitnence fluid replacement
calculate via weight
- first 10 kg = 100mL per kg
- second 10 Kg = 50 mL per kg
- remainig weight = 20 mL per kg
so if my pt. weight 75 kg
first 10 kg = 100 mL per = 1000 mL for 10 kg
next 10 kg = 50 mL per = 500 mL for 10 kg
(thats 20 kg = 75-20= 55kg remaining)
55kg x 20 mL/kj = 20 x 55 = 1100 mL
so then add = 1000 + 500 + 1100 = 2600 mL for the day
Types of Fluid
- colloid v crystalloid
- what is colloid
Colloid: think proteins
- colloid osmotic pressure: the pull from protein compounds on the water to pull it to where the proteins are (usually into the vessels)
- the pull of fluid back into the vessels from the proteins
administration of colloid fluids = will increased plasma colloid osmotic pressure
administration of crystalloid fluids = will decrease plasma colloid osmotic pressure
what are colloids
- large, INSOLUABLE molecules: proteins, complex polysaccharides, albumin, dextrans, starches
COLLOIDS WILL ALWAYS STAY IN THE EXTRACELLUAR INTRAVASCUALR SPACE BECAUSE THEY ARE TOO BIG TO CROSS MEMBRANES
when is colloid fluid given
what are some types
what are the advantages
Colloid fluid given in..
- burn victims: helps increase the plasma volume to improve the ability of blood flow to make it to the skin layers and help repair damange
- when crystalloid fluid is failing (because colloid is expensive)
Types of Colloid Fluids
- 5% albumin
- 25% albumin
- dextran (sugar!)
- hetastarch
- FFP: fresh frozen plasma
Posittives to Colloid:
- a 1:1 ratio of fluid and protein: so the rate of loss = rate of gain
- good in hypovolemic shock pts. to rapidly pull and maintin fluid in the intravascular spcaes to maintina flow/perfusion to organs
- can help to reduce the risk of fluid overload: since the ratio of solutes to solvent is 1:1 in these formulations
Negatives
- EXPENSIVE
- can ellict adverse reactions since delivering protiens or plasma
what is crystalloid fluid
three types of crsytalloid fuid
deciding which crystalloid to use
Crystalloid Fluid: water and electroyltes (which are water soluable)
- crystalloid fluid: has the ability to flow out of the intravascular spaces because they are water solubale compounds
- normal saline is the most commonly used
Types
- isotonic : same amout of solutes to solvent ratio as the blood
- hypotonic : less solutes than the blood
- hypertonic: more solutes than the blood
- pt is only loosing water (hyponatermic or hypovolemic) = give hypotonic fluids to replete the water without giving too much solutes: this will allow water to flow from the high concentration (plasma) into lower (cells wehre thgey had released their water already to try to help)
- pt is losing water and sodium: replace both via isotonic solutions
- pt is losing only sodium: replace the sodium via hypertonic solution to help allow water to exit the cell and “dilute” the sodium
Fluids
- isotonic: .9% saline (normal saline), d5W, D5 1/4NS, lactated ringers
- hypotonic: 1/2 normal saline, 1/4 normal saline
- hypertonic: 3% saline, D10W, D5 1/2 NS, D5LR
specifics about normal saline
Normal Saline (NS) = .9% sodium chloride = 154 meq/L (which is what the body is)
- used for ER resusitation (in hypovolemia) when pts. are losing water and electrolytes
- use at a low rate of < 12 mEq/day: because too much sodium can cause demyelination syndrome in the brain and AMS
- ** risk of hyperchloremic acidosis**
Specifics about lactated Ringers
an isotonic crystalloid fluid
- gives water, NaCl, K, Ca and Sodium Lactate (which is a buffer when converted into bicarb by the liver)
good for
- hypovolemic pts.
- burn viticums (when colloid cant be used)
- metabolic acidosis pt.
Risks
- metabolic alkalosis
- fluid overload
often what is given pre and post and during surgery to replete pts. after operations
D5W specifics
D5W is a HYPOTONIC solution: because there is 50 g of dextrose per 1 L of water: and teh dextrose is immediately used up for energy leaving mainly just water
(maybe their electrolyte balances are okay, but they need some extra fuel and water)
Contraindicated in
- hypersensitive to dextrose, corn
- previous interspinal/cranial hemorrhage
- delirum tremens
- devere dehydration
- hyperglycemic
- anuria
- coma
Risks
- confusion
- dehydration
- hyperosmoalr syndrome
- hypokalemia
- pulmonary edema
