Fluids Flashcards
What is the 60/40/20 rule?
60% total body weight = total body water volumes are for 70kg patient
40% is intracellular 28L
20% extra cellular 14L (15/5 or 16/4)
Interstitial 16% or 11L
Plasma is 4% or 3L
intracellular ions
K Mg Phosphate
extracellular ions
Na Ca Cl Hco3
patient population with higher TBW?
neonates
paitent population with lower TBW?
females
obese
elderly
How does plasma contact interstitial fluid?
pores in capillaries allow plasma to be in direct contact with interstitial fluid
What is the glycocalx? what is its function?
protective layer on the interior of blood vessels
this is the gatekeeper that determines what can do into interstitial space.
also has anticoagulant properties
what are some things that can impair the glycocalx?
sepsis
ischemia
DM
major vascular surgery
what is the blood volume breakdown of plasma vs RBCs?
60% plasma
40% RBCs
risk of chylothorax is greatest with which side of IJ insertion?
left IJ
technically there is a thoracic duct on right side too but it is very small
normal plasma osmolarity?
280-290 mOsm/L
formula to calculate plasma osmolarity?
2Na + ((glucose/18) + (BUN/2.8))
which electrolyte is most important determinant of plasma osmolarity?
sodium
what conditions can increase plasma osmolarity?
hyperglycemia
hypernatremia
uremia
list hypotonic fluid solutions
D5w
0.45% NS
list isotonic fluids
NS
LR
plasmalyte
Albumin 3%
voluven 6%
Hetastartch 6%
list hypertonic fluids
3% NS
D5 in 0.9% NS
D5 in 0.45% NS
Dextran 10%
why is D5W hypotonic?
dextrose is metabolisted to CO2 and H20 so it is basically just free water
does the third space really exist?
debatable
colloids increase plasma volume for how long?
3-6hrs
which colloid has anti-inflammatory properties?
albumin
how does Dextra 40 affect blood viscosity?
decreases viscosity which improves microcirculatory flow in vascular surgery
how long do crystalloids improve plasma volume?
20-30min
which colloid binds calcium?
albumin
FDA black box warning for synthetic colloids
risk of renal injury
which colloids cause the most coagulopathy?
dextran > hetastarch > hextend
what is the max colloid dose?
20ml/Kg
coagulopathy is not an issue with which colloid?
voluven
with colloid carries the highest risk of anaphylaxis?
dextran
does albumin increase the risk of infections disease transmission? why?
no, because it does not contain any antibodies
what is the most important site of K homeostasis?
the kidney
name some things that can cause hypokalemia
vomitting
diarrhea
NG suction
jeguoileal bypass (Malabsorption)
kayexelate
hypokalemic periodic paralysis
zollinger-ellison syndrome
S/S of hypokalemia and associated EKG changes
skeletal muscle cramping > weakness > paralysis
PR - long
QT - long
T wave flat
U wave
s/s of hyperkalemia and associated EKG changes
cardiac rhythm disturbances
5.5-6.5 peaked t waves
6.5-7.5 p wave flattening, PR prolongation
7.5-8.5 QRS prolongation
> 8.5 QRS > sine wave > V fib
hyperkalemia treatment
Redistribution:
insulin with D50
hyperventilation
bicarb
beta 2 agonist
Elimination
k wasting diuretics
kayexelate
dialysis
most common electrolyte disorder in clinical practice?
hypokalemia
what do you need to know about hypokalemia level before you treat it? Why?
need to know the underlying cause. K is mostly intracellular so plasma level may not represent total body K.
if hypokalemia is caused by intra-cellular redistrubtion giveing K can be lethal
do you need to know underlying cause to treat hyperkalemia?
no tx is always based on serum K level
what is the most abundant extracellular electrolyte?
sodium
you should consider delaying surgery for what sodium level?
less than 130
how fast you can correct sodium level?
only 1-2mEq/L/hr
if hyponatremia is treated too quickly what is the risk?
fluid shift from ICF to ECF > central pontine myelinolysis
if hypernatremia is treated too quickly what is the risk?
fluid shift ECF to ICF cerebral edmea
what else must you evaluate with na level to detrmine cause of na disorder?
plasma osmolarity and ECF volume because sodium abnormalities an exist in various states of hydration
which electrolyte is the most abundant in the body?
calcium
ionized ca level
1.16-1.32 mmol/dL
how much calcium is ionized?
50%
how much calcium is bound to albumin
40%
how much calcium is bound to an anion?
10%
how does ca aggect mag at NMJ?
it antagonizes it
blank acts as an intravascular calcium reservoir
albumin
how does acidosis affect ionized ca level
increases ionized Ca (albumin binds H+ displacing Ca into plasma)
how does alkolosis affect ionized Ca level
decreases ionized Ca (albumin binds Ca displacing H+ into the plasma)
what hormone increases Ca level
PTH
what hormone decreases Ca
calcitonin
how does hypocalcemia affect the EKG
long QT interval
how does hypercalcemia affect the EKG
short QT interval
s/s of hypocalcemia
skeletal muscle cramps
nerve irritability > paresthesia & tetany
laryngospasm
mental status chagnes > seizure
chovstek sign
trousseau sign
tx for hypocalcemia
calcium and vit d
what is chvostek sign?
tap angle of jaw > facial contraction on ipsilateral side
what is trousseau sign
inflate the BP cuff on UE > muscle spasm of the hand/forearm
hypercalcemia tx
0.9% NS and loop diuretic
how much magnesium is in the ECF?
1%
where is 99% of the bodies magnesium?
intracellular, mostly muscle and bone
do serum mag levels correlate with total body mag levels?
no, they may not
mag is required for blank sythesis
DNA
what electrolyte can be used to treat bronchospasm
magnesium
pre-eclampsia mag dosing
4g/10-15min followed by 1g/hr for 24hrs
does mag cross the placenta?
yes
when does magnesium increase the risk of neonatal resp depression?
when given for > 48hrs
do abnormal magnesium levels affect the EKG?
no, not unless super low or super high
how do you treat hypermagnesemia?
calcium
what is an important anesthetic consideration in the setting of c-section for patient with hypermagnesemia?
hypermagnesemia can prolong sux and NDNMBs
buffer systems in the blood
bicarb (most important)
Hgb (2nd most important)
renal buffer systems
re-absorb filtered bicarb
remove titratable acids
formation of ammonia
intracellular fluid buffer system
H+ into cells adn K+ out of cells thus acidosis often presents with hyperk and viceversa
what kind of acid is CO2?
volatile
name the 4 buffer systesm within the body
blood
renal
resp
intracellular fluid
What things can cause anion gap acidosis?
MUDPILES
methanol
uremia
DKA
paraldehyde
Isoniazid
lactate
ethanol
salicylates
what can cause normal anion gap acidosis?
HARDUP
hypoaldosertonism
actazolamide
renal tubular acidosis
diarrhea
uretosigmoid fistula
pancreatic fistula
what can cause metabolic alkolosis?
loop diuretics
vomitting
antacids
hperaldosteronism
pH < X is an indication for mechanical ventilation?
< 7.20
by how much is Ph affected by PaCO2 in chronic and acute resp acidosis?
acute resp acidosis: every 10mmHg ^ in CO2 pH decreases by 0.08
chronic resp acidosis: for every ^ 10mmHg in PaCO2 pH decreases by 0.03
three physiologic consequences of resp acidosis
myocardial depression
vasodilation
SNS stimulation
(the SNS stimulation can offset the myocardial depression and vasodilation)
why should you not correct PaCO2 in chronic resp acidosis?
they normally retain bicarb, if you return PaCO2 to normal you have now created metabolic alkalosis
what is metabolic acidosis?
the accumulation of non volatile acids
by how much does pH drop for every 1mEq/L decrease in HCO3?
PaCO2 decreases by 1-1.5mmHG for every 1mmEq/L decrease in HCO3
what is gap acidosis?
accumulation of acid
how do you calculate anion gap? what is the normal anion gap range?
Na+ - (cl + HCO3)
normal 8-12mEq/L
what is non gap acidosis?
bicarb loss or ECF dilution
anion gap acidosis tx
bicarb (contraversial)
lactic acidosis tx: IVF, O2, cardiopulm support
DKA tx: IVF and insulin
uremia or drug induced acidosis tx: dialysis
non-gap acidosis tx
bicarb usually helpful because most etiologies are from bicarb loss.
why is bicarb treatment for anion gap acidosis contraversial? when should it still be used?
is contraversial, best used as a temporary measure if pH < 7.2 and patient is hemodynamically unstable.
bicarb can cause intracellular acidosis in settings of inadequette ventilation or perfusion
name the 3 causes of metabolic alkalosis
addition of HCO3 (giving bicarb, or massive tranfusion because preservatives are converted to bicarb by the liver)
loss of non-volatile acid (loss of gastric fluic, loosing acid in urine, diuretics, ECF depletion (Na reabsoprtion + H and K excretion)
^ mineral corticoid activity (Cushing syndrome and hyperaldosteronism) ( hydrogen ion excretion)
how much does PaCO2 increase for every 1mEq/L increase in HCO3?
PACO2 ^ 0.5-1mmHg for every 1mEq/L increase in HCO3
metabolic alkalosis treatment
treat underlying cause
acetazolamide: ^ renal excretion of HCO3
spironolactone: mineral corticoid antagonist
dialysis
how to calculate 4:2:1 rule
add 40 if over 20kg
how does fasting affect intravascular volume?
minimally
does the 3rd space exist?
little evidence to support its existance
explain goal directed fluid mgmt
give small 200-250 boluses to see if patient is preload dependent
what are the 4 components to old school formula to calculate intraoperative fluids
maintence rate
replace fluid defecit
replace 3rd space loss
replace blood loss
how is post induction HoTN best treated?
vasopressors
it is due to vasodilation not dehydration
is UO a reliable marker of fluid status? why?
No
surgery causes ADH release > fluid retention for up to days to weeks
why must you monitor fluid responsive throughout an entire case?
fluid balance can change acutely in surgery
when can giving a small ammount of fluid cause pulm edema?
poor ventricular function
what was ERAS originally developed for?
colon surgery
5 components of ERAS protocols?
attenuate physiologic changes that accompany surgical trauma
minimize impact of fluid shifts
maximize nutritional impact of healing
improve pain so patient can recover faster
improve patient education and compliance
clear liquids up to 2 hours before surgery has what benefits?
^ hemodynamic stability
decreased gastric volume and gastric pH
if the clear liquids that are drank up to 2 hrs before surgery have carbohydrtes waht are the added benftis?
maintains preop glucose and insulin levels
decreases body’s response to surgical stress
what must you ensure if using epidural as part of ERAS protocol?
patient must have good function of LE to encourag early ambulation
this is the benfit of a well executed thoracic epidural
