Fluids Flashcards
What are the components that make up the intravascular space
blood
platelets
wbc
plasma
- electrolytes (Na/K/HCO3)
- albumin
- Ig
- coagulation factors
What are the components that make up the interstitial space?
lymph
electrolytes
protein
water
How does the inside of the cell differ from extracellular conditions?
active pumping of ions
- Na/K ATPase
- cotransporters
high Mg and K inside the cell
low Na inside the cell
What are the components of crystalloid fluid? What do they allow for?
electrolytes (Na/Cl)
water
small molecules like dextrose and buffers
it allows the fluid to enter all body compartments (because high water content)
Compare balanced with unbalanced crystalloid fluids
balanced: with buffers added
unbalanced = no buffers
What differs between fluids that are hypo - iso - and hyper tonic?
the dextrose concentration to alter the osmolarity relative to the surrounding environment
What is the electrolyte composition in the body?
most = Na
lots of Cl
way less K, glucose and HCO3
How do you calculate osmolarity
2(Na+K) + glucose (+ BUN sometimes)
What are osmotically active particles?
mainly…
electrolytes
glucose
urea
also keytones and mannitol
It depends on the number not the size of the particles
What is the blood osmolarity of dogs
290-310 mOsm/kg
What is the blood osmolarity of cats
290 - 330 mOsm/kg
List 3 types of isotonic crystalloid fluids.
0.9% NaCl
Plasmalyte
Ringer lactate
Compare the 3 types of isotonic crystalloid fluids
0.9% NaCl: no buffer
Plasmalyte: acetate buffer
- K and Mg
Ringer lactate: lactate buffer
- K and Ca
In what situation is 0.9% NaCl fluid indicated? What situation is it contraindicated?
indicated:
- hypochloremic metabolic acidosis (ex. a vomiting dog that loses Cl)
NOT for shock
Explain how fluid moves through body compartments when you give a isotonic crystalloid fluid
If giving IV bolus
- initially expands the vessel
- 75% of fluid will diffuse into the interstitium over 45 mins
How is potassium used in fluid support?
can use to reduce dilutional hypokalemia
must supplement in CRI
- if giving bolus it must be very small to avoid cardiac failure
When is magnesium used in fluid support
supplemented in critically ill patients as they are commonly low Mg
When is calcium used in fluid support
it can help increase vascular tone and contractility
What are 2 problems that you may encounter when supplementing electrolytes
calcium can precipitate with the citrate in blood products
potassium phosphate can precipitate with calcium
- don’t give with ringer lactate
What are 2 main uses for isotonic fluid
hypovolemia
- usually an acute problem
interstitial dehydration
- usually a chronic problem
What is isotonic fluids not useful for
tx intracellular dehydration
What are the adverse effects related to isotonic fluid
pitting/interstitial edema
What are the risk factors to consider before giving isotonic fluids
hypoalbuminemia
cardiac disease
pulmonary contusions
cerebral injury
sepsis
acute renal dz
What is overhydration
> 10% body weight
What fluid should you give a dog that has hypochloremic metabolic acidosis and why?
0.9% NaCl - isotonic
the elevated Cl in the fluid will allow for a reduction in bicarb
- reducing HCO3 (base) = reduces pH
HCO3 is elevated because it is a compensatory response due to the lack of Cl (attempting to maintain electrical balance - need more negative charge)
List 4 types of hypotonic crystalloids
0.45% NaCl
D5W
2.5% dextrose in 1/2 strength lactate ringer soln
normofundin
Explain why you cannot give D5W as a bolus
The dextrose is immediately taken up by RBC and thus what is left has the osmolarity equivalent to free water
- results in lysis of RBC
Explain why you cannot bolus normofundin
It has high potassium
- if you bolus = kill patient
What is the general feature of hypotonic fluid
half the concentration of Na and Cl as the body
Explain how fluid moves through body compartments when you give a hypotonic crystalloid fluid
when giving IV
- dilutes the intravascular space
- quick movement to interstitial space
- fluid moves intracellularly
What is hypotonic fluid used for
maintenance fluid - for normal patients to account for physiologic losses
when they require fluid but have cardiac disease
if have hypernatremia
not commonly used
What is hypotonic fluids not effective in treating?
shock
it leaves the IV space too fast
How do you treat hypoglycemia with fluids?
bolus 50% dextrose with 0.9% NaCl
- give quickly (1-2 mins)
- 50% dextrose will overwhelm RBC ability to absorb all of it = avoid lysis
to prevent future hypoglycemia
- add 2.5 - 5% dextrose
- no bolus
- add to isotonic fluid
What is an example of hypertonic fluid
7.5% NaCl
Explain how fluid moves through body compartments when you give a hypertonic crystalloid fluid
via IV
- water moves from interstitium (and maybe from intracellular space)
- cause dilation of the intravascular space
- after 45mins, 75% of the water will diffuse back to the interstitium
What is hypertonic fluids used for
hypovolemic shock in non-dehydrated patients
cerebral edema
How does hypertonic fluid compare to using isotonic fluid?
a small volume of hypertonic fluid will induce a similar amount of IV fluid expansion as isotonic fluid
What is a colloid
fluid with large organic macromolecules and electrolytes
- attract water
- cornstarch/potato starch
List 2 examples of natural colloids
albumin
fresh or fresh-frozen plasma
Provide 3 examples of synthetic colloids
hydroxyl ethyl starch
dextran
gelatin
Explain how fluid moves through body compartments when you give a colloid
via IV
- cause IV fluid expansion
- water bind the protein and starch to keep it in the vessel
What are colloids used for? Why?
theoretically good for hypovolemia because they induce a rapid IV volume expansion
What are some drawbacks to colloids
they induce a primary and/or secondary coagulation problem because it messes with platelet activation and the coagulation cascade
acute renal injury (bc starch = bad)
may cause dehydration
What are the reccommended things to consider before giving colloids
patient risk assessment
can use in the short term to fix low bp in anesthesia
NOT for the critically ill
only use minimum amount
List the routes of fluid administration
IV
PO
SC
IP
IO
What are the benefits to SC fluid administration
easy
fast
minimal restraint
maintain sterility
no IVC
What sized needle should you use for SC fluid
18-22 G
How much fluid can you give SC
10-30ml/kg
- cats usually just get 100ml
10-20ml per site
there is no set volume required - more based on how much is tolerated
Does SC fluid correct dehydration? Why?
NO
if >7% dehydrated should use alternate route of administration
because only half the daily maintenance of fluid will be absorbed per day
How to calculate the maintenance fluid requirement?
30 * body weight in kg + 70
if active
70 * BW ^ 0.75
if sedentary
97 * BW ^ 0.655
What should you be sure to tell owners after giving their pet SC fluid
there may be leakage from the site and the fluid bump will fall into their elbows/chest
How long does it take for SC fluid to absorb
24-48h
What type of fluid is given SC? Which is not?
room temp/warm isotonic
NOT dextrose (can cause lesions/inflammation due to acidosis)
you can add 20-40 mEq/L of potassium
What is IV fluids mainly indicated for
to expand IV volume - hypovolemia
acute loss
more volume needed
critically ill
> 5% dehydrated
What sites are used for IV fluids
peripheral sites
- cephalic
- saphenous (med/lat)
central
- jugular
Compare central and peripheral catheters
central: less common and more expensive
- require sedation
- can give hypertonic fluid
- some have multi-lumens for non-compatible drugs
peripheral:
- higher risk of phlebitis if giving high osmolar fluid
- difficult if the patient is small/thrombotic/edema/obese/status epilepticus/vasoconstricted/vascular collapse
What to do if you cant use IV for fluid administration
use IO
if IO not available use the peripheral vein cutdown technique
When is IO fluid administration commonly used? How?
shock
puppies and kittens (20-22G catheter)
adult animals (bone biopsy needle)
into the femur or humerus
to administer med/fluid - anything that can go IV can go IO
What are some drawbacks with IO fluid admin
osteomyelitis
difficult to maintain long term
can cause bone marrow necrosis if giving more hypertonic solution
may cause fracture
- if it fractures the fluid will go out of bone into SC
pain
When is PO fluid admin usually used
large animal
When is IP fluid normally used
exotics
How much fluid do you use to treat hypovolemia
fluid bolus and then 10-20ml/kg over 15-20 min
Can you give a fluid with added potassium to a blocked cat?
yes
because when you unblock the cat it will normalize the electrolyte values
What should you do when you see a severe hyponatremia
STOP and consider
- is it acute or chronic (< 24 or > 24h)
- did the body have time to make iogenic osmoles
What are iogenic osmoles
molecules that act to increase the intracellular osmotic pressure to maintain water in the cell
the cell can produce these in response to environmental change in 2-3 days
In what situation, if any can you quickly give fluids to treat severe hyponatremia?
if it is an acute problem in which there wasnt enough time to generate iogenic osmoles
What is something that you can do that causes pontine demyelination? Why?
if you give fluid too fast to rectify severe hyponatremia
because water will rapidly leave the cell causing = shrink myelin sheath
- reduced iogenic osmoles in the cell
this is irreversible
How to safely fix severe hyponatremia
use a lactated ringer soln over 4 hours
monitor
adjust if if you are giving too high a concentration by adding 0.45% NaCL or D5W (hypotonic)
What is a safe rate to change Na concentrations with fluids?
0.5-1 mmol/L/h
How long will it take to fix a hyponatremia of 125 mmol/L (normal 145 mmol/L)
20 mmol/L deficit
0.5-1 mmol/L/h
20-40 h minimum
What should you do when you see a severe hypernatremia
STOP and consider
- is it acute or chronic (< 24 or > 24h)
- did the body have time to make iogenic osmoles
What will happen if you correct a hypernatremia too fast
neurologic signs due to intracellular edema and cerebral edema
because cells were adapted to chronically high sodium environment
- they made iogenic osmoles to compensate
