PHRM 844 Fluids/Electrolytes Review

what are fluid and electrolyte calculations

estimates

what three types of weight are equal

dry weight, admit weight, actual weight

male ibw formula

50 + (2.3 * inches over 60)

female ibw formula

45.5 + (2.3 * inches over 60)

when to use dosing body weight

certain drugs (antibiotics --> fat feeding drugs)

when to use nutrition body weight

fluid, electrolyte, nutrition paramaters

what is different between dbw and nbw

dbw uses 0.4 and nbw uses 0.25

why does nbw use 0.25

we dont want to feed the fat so we want a lower weight

what percent of body weight in adults are fluids

60

2 types of extracellular fluids

interstitial and plasma (intravascular)

why do geriatric patients have lower body water composition

decreases with age, skeletal muscle mass declines, proportion of fat increase

why do we want to balance fluids

maintain temp, cell shape, transport nutrients, gases, wastes

two types of fluid losses

sensible and insensible

3 types of sensible fluid loss

urination, defecation, wounds

2 types of insensible fluid loss

skin, lungs

between sensible and insensible which fluid loss can be larger

sensible (1-1.5 L/day)

3 ways volume is regulated

kidneys (nephron), thirst, hormonal changes

isotonic range

275 - 290 mOsm/L

how does hypotonic fluid affect cells

fluid moves into the cell which increases cellular volume

how does hypertonic fluid affect cells

fluid is pulled into the bloodstream from cells which increases the volume of blood

which types of tonicity cause fluid shifts

hypotonic and hypertonic

define osmolarity

measure of solute concentration (want it to be isotonic)

what is total osmolarity

osmolarity of iv solution plus osmolarity of electrolytes

clinical estimate of MIVF

30-40 mL/kg/day

what is MIVF

maintenance iv fluids (normal amount needed over 24 hours)

what type of fluid is hypertonic

colloid

what tonicity can crystalloids be

isotonic, hypertonic, hypotonic

what tonicity can colloids be

hypertonic

crystalloid examples

NS, 1/2NS, D5W, LR, balanced salt solutions

colloid examples

albumin, heta/tetrastarch, blood, plasmanate

what do crystalloid solutions maintain

osmotic gradient between intravascular and extravascular compartments

what can normal saline be used for

resuscitation, intravascular fluid replacement, sodium replacement, chloride replacement

what can 1/2 normal saline be used for

maintenance fluids (in combination)

what can LR be used for

replacement of blood loss, human plasma (replicates blood), increases volume, resuscitation (for trauma patients)

what is LR

lactated ringers

what can D5W be used for

free water replacement, NOT maintenance, NOT for resuscitation, mimics water

why is normal saline not normal

10% higher sodium and 50% higher chloride

what are balanced salt solutions

physiologic levels of chloride/buffer solutions

balanced salt solutions examples

LR, normosol-R, plasma-lyte

which crystalloid has 100% ECF distribution

normal saline

which crystalloid mimics normal distribution (1/2 water)

1/2 normal sailne

normal sodium levels in the blood

135-145

why is normal saline worse than balanced salt solutions

increases mortality, acidosis, renal injury, blood transfusions, harder to clot

why would you use a colloid solution

to increase plasma oncotic pressure and to move fluid from the interstitial compartment to the intravascular compartment

why are colloids called plasma expanders

increased molecular weight, maintain bp, expand volume, long half-life

what is a second-line therapy for hypovolemic shock

colloid in a large 1 L bag

why do we use albumin

volume expansion, shock, burn, ARDS, bypass, OR

adverse effects of albumin

hypervolemia, azotemia, anaphylaxis

why do we use albumin 5 over albumin 25

higher volume, lower concentration for hypovolemic (intravascularly depleted) patients

why do we use albumin 25 over albumin 5

smaller volume, higher concentration for fluid/Na restricted patients that need protein

when do we use blood

acute blood loss, unable to resuscitate from fluids alone, pre-op, low hemoglobin (need transfusion)

how many units of RBCs are needed to increase hemoglobin levels by 1 g/dL

1

MIVF formula

D5W + 1/2 NS + 20 mEq KCl/ L

how can we monitor fluid status

weight, ins/outs, volume status, urine output, vitals

how to tell if patient is dehydrated

physically (tent, throat dry, finger capillary), fast hr and hypotension, weak pulses, decrease urine, SCR > 20

loop

what kind of diuretic is this

amount of Na in NS

154 mEq/L

which electrolyte lives outside the cell

Na

which electrolyte lives inside the cell

K

normal sodium values

135-145

3 uses for Na

extracellular cation, maintain cellular integrity, maintains osmolar gradient (fluid homeostasis with water)

most common electrolyte disturbance

hyponatremia

osmolality range

275-290

define osmolality

number of particle per liter of water

osmolality calculation

(2*Na) + (BUN/2.8) + (glucose/18)

define pseudo hyponatremia

sodium appears low but is displaced by extreme elevations of lipids and proteins, mOsm 275-290

define hypertonic hyponatremia

mOsm >290

what to give patient with hypertonic hyponatremia with corrected serum Na in ok Na range

insulin to lower glucose levels

define hypotonic hyponatremia

mOsm < 275, 3 types

define isovolemic hypotonic hyponatremia

increase in TBW and normal Na

define hypervolemic hypotonic hyponatremia

high volume holding on to Na which lowers Na levels

define hypovolemic hypotonic hyponatremia

low volume, very dehydrated, extremely sick, decrease in water/Na

how do you become hypovolemic hypotonic hyponatremia

diuretics, adrenal insufficiency, cerebral salt wasting, blood loss/hemorrhage, skin loss (burns, wounds), GI loss (vomiting/diarrhea)

how do you become isovolemic hypotonic hyponatremia

adrenal insufficiency, hypothyroidism, psychogenic polydipsia, SIADH

SIADH

syndrome of inappropriate antidiuretic hormone (making too much ADH)

how do you get SIADH

tumors, CNS disorder, DRUGS

drugs that cause SIADH

antipsychotics, carbamazepine, SSRIs

how to treat SIADH

remove medications, free water restriction, conivaptan/tolvaptan (if free water doesn't work)

how to get hypervolemic hypotonic hyponatremia

cirrhosis, heart failure, kidney failure, nephrotic syndromes

NMT for hyponatremia

>0.5 mEq/L/hr or 8-12 mEq/L/day

hypovolemic hyponatremia treatment

hypertonic 3% NaCl for symptomatic, 0.9% NaCl for asymptomatic

isovolemic hyponatremia treatment

furosemide and 3% NaCl for symptomatic and 0.9% NaCl/water restriction if asymptomatic

hypervolemic hyponatremia treatment

furosemide and judicious 3% NaCl for symptomatic and furosemide for asymptomatic

what type of hyponatremia is death more likely

acute

why is death/brain herniation more likely in acute hyponatremia than in chronic hyponatremia

because the brain is swelling at a faster rate and is herniating faster, making symptoms more severe

symptoms of acute symptomatic hyponatremia

altered mental status, seizures, fatal

what tonicity is hypernatremia

hypertonicity

how to get hypovolemic hypernatremia

loss of water from renal, GI, lung, skin

how to get isovolemic hypernatremia

diabetes, skin loss, osmotic diuresis

how to get hypervolemic hypernatremia

sodium overload, mineralocorticoid excess

normal potassium levels in blood

3.5-5

4 uses for potassium

intracellular cation, cell metabolism, glycogen/protein synthesis, resting potential across cell membranes

causes of hypokalemia

diuretics, b agonists, alkalosis, diarrhea, magnesium depletion

how to treat hypokalemia range 3.5-4

nothing unless in ICU (then treat)

how to treat hypokalemia range 3-3.4

debatable, but if patient has cardiac problems give oral potassium

how to treat hypokalemia range under 3

oral is preferred for asymptomatic, iv for symptomatic, correct mg deficit

why do we only want iv potassium in severe cases of hypokalemia

thrombophlebitis at infusion site, arrythmia/cardiac arrest if given too quickly

how to administer iv potassium

10 mEq/hr (no monitoring), 20 mEq/hr (with monitoring), no iv push

what happens in hyperkalemia

STeMi

how to treat hyperkalemia

C A BIG K DROP