CCU: Fluids Flashcards
Total Body Water (TBW) is
60% of the body weight
The total body water is divided between
intracellular fluid (ICF) and extracellular fluid (ECF) water
In small animals, what percent of body weight is intracellular water (ICF)
40% of body weight (2/3 of TBW which is 60%)
In small animals, what percent of body weight is extracellular water (ECF)
20% of body weight (1/3 of TBW)
Extracellular water (ECF) is about 1/3 of the total body water. How is this further divided
Interstitial Water: 75%
Intravascular Water: 25%
2/3 of TBW is ________ while 1/3 of TBW is _______
2/3: intracellular fluid
1/3: extracellular fluid (75% int, 25% IV)
What is the barrier between ICF and ECF compartments
-Semi-permeable cell membrane
-Freely permeable to water based on concentration gradients
-Impermeable to electrolytes and proteins unless by tranport
Fluid moves because of osmotic forces
How does fluid move between ICF and ECF
via osmotic forces
How does fluid move within the ECF, specifically between the Interstitial and IV spaces
Endothelium
freely permeable to electrolytes based on concentration gradients- water will follow
relatively impermeable to proteins, larger molecules
*Fluid moves because of Starling forces
How does fluid move across semi-permeable membrane (between ICF and ECF)
osmotic forces
How does fluid move across endothelium (between Int and IV)
Starling’s forces
freely permeable to electrolytes based on concentration gradients
Loss of ECF is
dehydration
Loss of isotonic fluid is
loss of ECF
-osmolality does not change
-dehydration
Loss of hypotonic fluid is
loss of ICF
-may depend on how hypotonic the fluid is
Loss of intravascular fluid volume is
shock
-redistribution of fluids between ECF/ICF
Isotonic fluid will distribute to
ECF based on body fluid distribution
if you give 100mL
75mL in int while 25mL in IV
What are the signs of dehydration
-Changes in body weight
-Tacky mucous membranes
-Decreased skin elasticity
-Sunken eyes in orbit
-Signs of hypovolemia
What are the signs of mild dehydration
1) 5-7% change in body weight
2) Tacky mucous membranes
3) Slightly decreased skin elasticity
4) Normal position of the eye
What are the signs of moderate dehydration
1) 8-10% change in body weight
2) Tacky mucous membrane
3) Decreased skin elasticity
4) Eyes may be sunken
What are the signs of severe dehydration
1) 10-12% of body weight
2) Tacky mucous membranes
3) Skin stands in a fold
4) Sunken eyes
5) Hypovolemia signs
How fast should you correct dehydration
Between 4-24 hours (greater the dehydration the faster you replace it)
usually need to replace it in 8-12 hours
What factors influence the timeframe you correct dehydration
-Speed of loss
-Compensatory mechanisms
-Clinician’s experience and style
-Species
-Comobordities (heart, lung, kidneys)
-Age- young dogs very hard
-Practicality
-Monitoring abilities
-Severity of dehydration
You have a 28kg dog with 8% dehydration. How do you correct this fluid deficit over 12 hours
28 x 0.08 = 2.24 L
28 x 8 x 10= 2240mL
over 12 hours = 187 ml/hr
Can use LRS- most commonly used fluid in the US
What is the maintenance formula for dogs
132 x BW(kg)^0.75
or
70 x BW (kg)^0.75
or 40-60mL/kg/day
or 2-4mL/kg/hr (small dog higher end, big dog or cat use lower end)
or 30xBW(kg)+70ml/day
gives out mL/day
What is the maintenance formula for cat
70 x BW(kg)^0.75 =mL/day
Allometric scaling for maintenance
using BW^0.75 to determine maintenance - good because it isnt a linear scaling
the amount of fluid in the vascular space at equilibrium
depends on individual fluid behavior in the body
volume expansion power
What is the volume expansion power of hypotonic fluid
8.3%
T/F: hypotonic saline can be used for resuscitation
False- very had volume expansion power
What is the volume expansion power of isotonic crystalloid
25% (3/4 goes into the interstitial but it is cheap and forgiving)
What is the volume expansion power of colloids
80-120%
What is the volume expansion power of hypertonic saline (7.0-7.5 NaCl)
500-700% - pulls intracellular and interstitial fluid into the intravenous compartment
Why do you not want to give hypertonic saline too much
-Hypernatremia
-Intracellular dehydration
-Will go away in 30 minutes
good for TBI or equine practice
Rank the following on Volume Expansion power
Colloids, hypertonic saline, hypotonic saline, isotonic saline
HS > Colloids > isotonic fluid > hypotonic
Rank the following on Volume given for shock patients
Colloids, hypertonic saline, hypotonic saline, isotonic saline
Isotonic Fluid > Colloids > Hypertonic Saline
What is a shock dose of isotonic saline for K9-BV-EQ *
80-100 ml/kg
What is a shock dose of colloids/blood products for K9-BV-EQ *
20ml/kg
What is a shock dose of hypertonic fluid for K9-BV-EQ *
5ml/kg
What is a fluid challenge/mini-bolus for shock patients for K9-BV-EQ
10-20mL/kg (close to 1/4 of shock dose)
What is the shock dose for cats *
Isotonic Fluid: 40-60ml/kg
Colloids: 10ml/kg
Hypertonic fluid 3ml/kg
Blood products 10ml/kg
What is the isotonic fluid shock dose for cats*
40-60ml/kg
What is the colloid shock dose for cats*
10ml/kg
What is the hypertonic shock dose for cats
3ml/kg
What is the fluid challenge/mini bolus for cat patients
5-10ml/kg
How does the isotonic shock dose for dogs differ from cats
80-100ml/kg (dogs)
40-60ml/kg (cats)
How does the fluid challenge/ mini bolus dose for dogs differ from cats
Dogs: 10-20ml/kg
Cats: 5-10ml/kg
Whats a good first line of defense while you gather more information and investigate the cause of shock
Isotonic crystalloids
What is LRS shock dose for 12kg dog
800-1000mL
do 1/4 shock dose = 200-250 mL
How fast should you give the shock dose
aliquot the shock dose over a period of time
usually 5 to 30 minutes depending on
-severity of shock
-speed of loss
-compensatory mechanisms
-Clinicians experience and style
-Species
-Comorbidities
-Age
-Practicality
-Monitoring abilities
-Cause of shock
What happens if hypertonic saline is given too fast
bradycardia
vasodilation
What happens if hypertonic saline is given too slow
losses the VEP
What should you do after giving hypertonic saline
Follow up with another type of fluid
-Colloids or isotonic crystalloid
-But less volume of those are required (1/4 shock dose)
-Used as volume-sparing
T/F: hypertonic saline can be used in foals
False
Hypertonic saline should be given over
full shock dose (3-5ml/kg) over 5 minutes
will redistribute in all compartments in 20-30min
How are blood products delivered for shock
higher aliquots of volume as a shock dose (10-20ml/kg)
can be given fast (5-30minutes)
if possible, equal volume of plasma and red blood cells
What products do you want to give the full shock dose
Hypertonic saline
Blood products
For a hypotensive patient with uncontrolled hemorrhage, you need to keep the systolic blood pressure at ________ until the hemorrhage is controlled
80-90mmHg
What should you do for sepsis
-early aggressive fluid resuscitation
-find and control source of sepsis
-early anti-microbial use
use of artificial colloids is controversial
What should you do for burns
Higher volume of crystalloids to control for evaporative losses
Use colloids or albumin products (because of protein loss)
Use blood products for fluid resuscitation when
there is severe hypovolemic hemorrhage shock
What are the criteria to use blood products in vet med
-More negative base excess
-High lactate *
-More severe shock (higher HR, lower temp)
-Lower PCV and TP
-Higher ANimal Trauma score- orthopedic injuries
-Semi-quantitative FAST 3 and 4
What should you do for a patient with massive blood loss and exsanguinating regarding fluids
rapid administration of blood products (red blood cell and plasma)
-minimize crystalloid use
What is the main component of osmolality
Sodium
What is the normal plasma/extracellular sodium
140-150 mmol/L
What is the concentration of intracellular sodium
10 mmol/L
What is the plasma osmolality equation
mOsm/kg = 2(Na+K) + BUN (mg/dL) / 2.8 + glucose (mg/dL)/18
T/F: ECF osmolality = ICF osmolality
True
What is normal osmolality
280-320 mOsm/kg
What triggers ADH
1) Increase Na+
2) Hypovolemia- will dilute plasma and decrease Na+
What is the mechanism of action of ADH
plugs aquaporins in the distal tubule to reabsorb only water
What triggers thirst
increases in Na+, dehydration, hypovolemia
ADH being triggered due to increases in Na+ is______________ while those triggered by hypocvolemia is
Increases Na+: very tightly regulated
feedback loop and Na decreases
Hypovolemia: Will dilute the plasma and decrease Na but less sensitive but very efficacious
How does Na concentration change with isotonic fluid loss
Na concentration does not change
What is the only ways to change Na+
1) Losses of free water
2) Gain of free water
3) Losses of hypertonic fluid… extremely rare
4) Gain of hypertonic fluid
Hypernatremia means there is ________ water
not enough water
Hyponatremia means that there is ________ water
too much water
What are the causes of hypernatemia
Losses of free water
1) CNS disorders- hypo/adyspsia,
2) No access to water
3) Diabetes inspidus
4) Fever
5) Burns
6) Panting or tachypnea
Gain of hypertonic fluid
7) Salt intoxication
8) 7.5% NaCL
What are the three main causes of hypernatremia
1) CNS disorders (hypo/adyspsia)
2) No access to water
3) Salt intoxication
What are the causes of hyponatremia
Gain of free water
1) Fluid therapy with hypotonic fluid-D5W
2) ADH secretion- due to hypovolemia
3) High osmolality (hyperglycemia, mannitol)
4) Renal failure
5) Addison’s Disease
6) Accidental or voluntary water ingestion
Losses of hypertonic fluid
7) very rare
How do patients with diabetes insipidus keep their sodium normal so they dont become hypernatremic
keep drinking, they are PU/PD
Hyponatremia is most likely caused by________ *
ADH secretion due to hypovolemia
T/F: 1% Na variation is normal
False- Na+ is very tightly regulated
How do you treat hypernatremia
not enough water
treat the primary cause (ie DI or CNS)
use Hypotonic fluids
D5W= Dextrose 5% in Water (100% free water)
-0.45% NaCl, Plyte 56- needs double the fluid as not 100% water
How do you determine the water deficit when treating hypernatremia
0.6 x BW(kg) x [(Patient Na/Normal Na)-1]
Normal Na:
145 mmol/L (dog)
150 mmol/L (feline)
How fast do you correct hypernatremia
if chronic changes, compensatory mechanisms in place
recommend correction of chronic changes around 0.5mEq/L/h
eg.
chances from Na+ of 170 to 150 in 40 hours
Can be faster if know acuteness of disorder
If you have a free water deficit (hypernatremia) , why do you not want to correct it rapidly
the cells are shrunken and producing idiogenic osmoles to return to normal cell volume
if the clinician is aggressive they can potentially become over swollen
How do you treat hyponatremia
Too much water- treat the primary cause
1) Hypovolemia (ADH secretion)- give enough fluid any kind - IV
2) Treat renal disease
3) Mineralosteroids for addisons
4) Inappropriate ADH secretion- stop fluids +/- diurectics
5) Stop giving fluids (TPN, low Na+ containing fluids)
6) Diabetes mellitus: treat hypovolemia and hyperglycemia
When fixing the hypovolemia / hyponatremia you should match the patient’s Na concentration within
10 mmol/L
How do you treat SIADH
Stop fluids +/- diuretics
What is delta Na equation and what is it useful for
Delta Na = (fluid Na-patient Na)/ (0.6xBW)+1
shows the impact of 1L of fluid
When correcting hyponatremia, why should you never correct more than 0.5 mmol/L/hr
When there is free water excess, the cells are swollen and getting rid of idiogenic osmoles if you correct too fast then the cells will shrink
-Acute cerebral swelling shrinkage leading to seizures, changes in mentation
What happens if you fix sodium abnormalities too rapid
Acute: Seizures, changes in mentation, etc due to acute cerebral swelling or shrinkage
Delayed: Osmotic demyelination syndrome- consequence of steep rise of sodium concentration, delayed 3-4 days
due to a quick rise in Na concentration (typically low to normal)
myelin loss in the brain (pons > other locations)
lethargy, weakness, ataxia, hypermetria
no treatment
What causes osmotic demyelination syndrome
quick rise in Na concentration (typically low to normal but can also be normal to high)
delayed 3-4 days
What are the results of osmotic demyelination syndrome
myelin loss in the brain (pons > other locations)
lethargy, weakness, ataxia, hypermetria
no treatment
How does the treatment of hypernatremia differ from hyponatremia
HyperNa: give free water +/- treat primary; slow and only acute risks
HypoNa: primary cause +/- extra Na ; SLOW
acute and delayed risks
Is potassium mostly intracellular or extracellular
Intracellular- 140 mEq/L
Extracellular/Plasma K+ is only 5mEq/L
T/F: potassium has a very narrow therapeutic range
true
What does potassium contribute to
the resting membrane potential
-cell excitability
-ability to generate an action potential
What excretes potassium
Renal 90%
GI 10%
what secretes K+ in the distal nephron
Aldosterone
How does the body respond to hyperkalemia
Increased kaliuresis- increased concentration gradient in the distal nephron
What allows increased uptake of K+ by the muscle
Increase Na-K-ATPase activity
What influences regulation of K+
H+ concentration
Insulin
b-adrenergic activity
diuretics
What are the 4 main causes of hyperkalemia *
1) Oliguria/anuria **
2) Urinary obstruction/ruptured **
3) Addisons Disease
4) Pseudohypoaldosteronism (third spacing, trichuris infection)
What can cause hyperkalemia
1) Oliguria/anuria **
2) Urinary obstruction/ruptured **
3) Addisons Disease *
4) Pseudohypoaldosteronism (third spacing, trichuris infection) *
5) Increased intake (overzealous high K+ supplementation)
6) Tissue catabolism/reperfusion injury
How do you diagnose hyperkalemia
-Serum K+
-ECG: bradycardia, spiking of t waves, widened qrs, decrease/loss of p waves, increase p-R interval, sin wave
-physical examination findings: bradycardia and hypothermia in urethral obstruction in cats
in hyperkalemia, what would the ECG look like
-bradycardia
-spiking of t waves
-widened qrs
-decrease/loss of p waves
-increase p-R interval
-sin wave
In urethral obstruction in cats, what is a physical exam finding
hypothermia and bradycardia
What amount of potassium is very concerning and you should freak out
> 6-7.5mmol/L and clinical signs!
also primary disease: anuric renal failure vs urethral obstruction
How do you counteract the cardiovascular effect of hyperkalemia
calcium administration - usually gluconate 10%
How do you treat hyperkalemia
-IV fluids if able to urinate
-Insulin (+dextrose)
-Dextrose
-HCO3-
-Dialysis
Calcium gluconate to counteract cardiovascular effect
What causes hypokalemia
1) Increased renal losses- diuretics and renal insufficiency
2) Translocation of K+
3) Increased GI loss - vomiting and diarrhea
4) Decrease intake (rare)
What might cause hypokalemia due to increased renal losses
1) Diuretics *
2) Renal insufficency *
3) Hyperaldosteronism
4) Fluid therapy
5) Metabolic acidosis
6) Hypomagnesemia
What might cause hypokalemia through translocation of K+
1) Insulin/dextrose therapy
2) b-adrenergic toxicity (albuterol)
3) Hypothermia
4) Metabolic alkalosis
What might cause hypokalemia through increased GI loss
vomiting and diarrhea
How do you diagnose hypokalemia
1) Serum K+
2) Physical exam: neck ventroflexion
What is a physical exam finding of hypokalemia
neck ventroflexion
You should treat hypokalemia when it is
less than 2.5-3.0
How much KCl should you give to treat hypokalemia
supplement using table
*Do not exceed 0.5mEq/kg/hr
make sure to monitor, especially at high K+ supp rate
What commonly cause hypercalcemia
Vitamin D toxicity (e.g cholecalciferol-based rat bait)
Neoplasia
When Ca x P gets ___________ there is a risk for organ mineralization
> 60-70
How do you treat hypercalcemia
IV fluids with 0.9% NaCl, furosemide, steroids
What is a common cuase of hypocalcemia
eclampsia
How do you treat hypocalcemia
Ca gluconate 10% at 0.5-1 mL.kg over 15-20 min
What commonly causes hypomagnesemia
grass tetany in large animals
critically ill patients: SIRS, etc in SA
How do you treat hypomagnesemia
treat with IV supplementation (magnesium sulfate or chloride) or use Plasmalyte 148/ Normosol R
What is the equation for sodium deficit
0.6 x BW (kg) x (Normal Na-Patient Na)
Shock should be staged based on severity using
1) Lactate measurement
2) Blood pressure
3) Decreased urine output
What shock syndromes are not fluid responsive
Anemic
Hypoxemic
Metabolic Shock
what shock syndrome is the most responsive to fluid resuscitation
hypovolemic
Why is distributive shock only partially fluid responsive
vasopressors also needed to counteract inappropriate vasodilation
Obstructive shock may also be fluid responsive but what else do you need to do
definitive treatment of underlying cause (ie. drain pericardial fluid or correct the gastric-dilation volvulus)
