Total Nody Water (TBW)=
- 60% OF BW
- 70% in LA <30 days old
- 60% of lean BW in obese animals (LBW= 0.7xBW)
Why are cats more/less susceptible to volume overload than dogs?
MORE: cats normally have 4-6% of BW as intravasulcar water (dogs usually 8-9%)
What is the barrier between the ICF and ECF, and what are its properties?
- cell membrane
- freely permeable to water (conc gradients)
- impermeable to electrolytes and proteins
What is the barrier between the ISF and IVF, and what are its properties?
- freely permeable to water (conc gradients)
- freely permeable to electrolytes (conc gradients)
- relatively impermeable to proteins and large molecules
What is the law of electroneutrality?
the number of positively and negatively charged ions must be equal
Extracellular water is composed on __(2)__.
interstitial water + intravascular water
In SA patients, TBW= _____ ICF + _____ ECF.
In LA patients, TBW= ______ ICF + _______ ECF.
In LA patients <30 days old, TBW= _____ICF + _____ECF.
How do you calculate intravascular water in a dog, cat, and horse?
- Dog: 8-9%*BW (5%*BW=plasma)
- Cat: 4-6%*BW (3%*BW=plasma)
- Horse: 8%*BW (5%*BW=plasma)
__________ is the predominant extracellular ion; _________ is the predominant intracellular ion.
What is the clinical significance of K+ being an intracellular ion?
Blood levels of K+ may not be reflective of how much potassium is inside the cells (you can have ow potassium and maintain relatively normal blood K+ levels)
Potassium is primarily responsible for ___________.
Sodium is predominantly responsible for __________.
When ions have a different conc on either side of a semi-permeable membrane, it creates ____________.
Oncotic forces are generated by...
macromolecules that do not readily move across the endothelium.
Generate osmotic pressure across a semi-permeable membrane that is not permeable to that particle, resulting in the movement of water.
What are the main effective osmoles? (2)
Effective osmoles determine _________.
Molecules that have osmotic potential but are able to diffuse across the barrier, resulting in no generation of osmotic pressure and no movement of water.
What are examples of ineffective osmoles? (2)
urea (diffusible), glucose (metabolized)
Ineffective osmoles contribute to ___________ but not _________.
What is the equation to calculate osmolality?
Osm= 2 (Na + K) + glucose/18 + BUN/2.8
What are the consequences of hypotonic loss (loss of water in excess of electrolytes)? (4)
- water shifts from ICF to ECF
- ECF supported, ICF decreases, TBW decreased
What are the consequences of hypertonic loss (loss of electrolytes in excess of water)? (4)
- water shifts from ECF to ICF
- ECF decreased, ICF increased, TBW stays the same
What are the consequences of isotonic loss (loss of equal parts electrolytes and water)? (4)
- no shift in water from ECF to ICF
- ECF decreased, TBW decreased, no change in ICF
What is capillary hydrostatic pressure, and what does it cause?
pressure of fluid within the capillary, causing net movement out of the vessel
Capillary hydrostatic pressure is primarily dependent on __________ because...
venous pressure; arterial pressure is not transmitted across the pre-capillary sphincter (hypertension does not cause edema!)
What are causes of increased capillary hydrostatic pressure? (4)
venous obstruction, congestion from CHF, thrombosis, volume overload
What is the interstitial hydrostatic pressure and what does it cause?
- pressure of fluid within interstitium
- positive interstitial hydrostatic pressure causes net movement INTO vessels (negative causes fluid to move out of vessels)
Interstitial hydrostatic pressure is primarily dependent on ____________; the clinical significance of this is...
- "looseness" of tissue (extracellular matrix arrangement)
- edema more common in looser tissues (skin)
What is the capillary oncotic pressure and what does it cause?
- force exerted by proteins (primarily albumin) which do not readily move across the endothelium
- serves to keep fluid in the vessel; positive moves fluid into vessels
What is the interstitial oncotic pressure and what does it cause?
- force of protein in tissue to draw out water
- net movement out of vessels
With oncotic pressure, it's the _________, not the __________, that contributes to pressure.
quantitiy; size of the protein
What is the safeguard system against edema?
lymphatic drainage (lymphatic obstruction can lead to edema); has a large capacity to drain fluid from interstitium
What are crystalloids, and how are they categorized?
- varying electrolyte composition in water
- categories- tonicity [hypotonic, isotonic, hypertonic], electrolyte composition [saline, balanced electrolyte], effects of acid-base[ acidifying NaCl, alkalinizing LRS or plasmalyte]
Describe hypotonic crystalloids.
osmolality less than that of blood--> net increase in free water
Where is the volume of distribution of hypotonic crystalloids?
total body water (across all fluid compartments)
What are examples of hypotonic crystalloids? (3)
- dextrose 5% in water (D5W- dextrose not effective osmole- metabolized leaving free water)
- 0.45% NaCl (half saline)
- Normosol M (maintenance fluid)
What are the clinical indications for hypotonic crystalloids? (3)
- replace free water deficit (hypernatremia)
- heart and renal disease (can't handle sodium load)
- maintenance fluid
When should you NEVER use hypotonic crystalloids and why?
- never use for resuscitation! never use as a bolus! (never administer rapidly)
- dramatic change in blood osmolarity causes RBC damage
Describe isotonic crystalloids.
osmolality is approximately equal to blood--> replace electrolytes and water
Where is the volume of distribution for isotonic crystalloids?
extracellular space (redistribution to interstitium within 20-30 min after being put in vasculature)
What are examples of isotonic crystalloids? (4)
- Non-balanced acidifying electrolyte solution: Normal Saline (0.9% NaCl)
- Balanced alkalinizing electrolyte solutions: Plasmalyte, LRS, Norm-R
Why is 0.9% NaCl acidifying?
it's equal parts sodium and chloride, but blood is more sodium that chloride--> relative increase in Cl- causes decrease in SID--> bicarb loss--> acidify
Why are balanced electrolyte solutions alkalinizing?
they provide bicarbonate precursors, increasing the body's production of bicarb
What are clinical indications for isotonic crystalloids? (4)
correct acid-base disorders, rehydrate, replace ongoing losses, resuscitation
What are potential adverse effects of isotonic crystalloids? (3)
creation of acid-base disturbances, tissue edema (fluid goes to interstitium), pro-inflammatory effects
Describe hypertonic crystalloids.
osmolality greater than that of blood--> shift fluid from interstitium into vascular space
Where is the volume of distribution of hypertonic crystalloids?
- rapid volume expansion within the vascular space early on (transient)
- within 10-30min, redistributes across the extracellular fluid (interstitium)
What are clinical indications for hypertonic crystalloids? (3)
resuscitation, head trauma/ cerebral edema, correction of acute hyponatremia
What are potential adverse effects of hypertonic crystalloids? (4)
- short duration of volume expansion
- transient hypernatremia
- reflex bradycardia (with overly rapid administration)
- contraindicated in dehydration
molecules that do not readily cross capillary membranes and stay in vascular space
Where is the volume of distribution of colloids?
contribute to capillary oncotic pressure--> increase intravascular fluid (blood volume)
__________ is the most important colloid in blood.
In states of increased vascular permeability, colloid administration can lead to...
colloid accumulation in the interstitium and edema.
What is the synthetic colloid, and where is its volume of distribute?
- hydroxyethyl starch
- vascular space--> increases intravascular volume and prolonged vascular expansion
What does it mean that synthetic colloids are polydispersed complex starches?
smaller molecules confer oncotic pressure and larger molecules confer duration of action
What are the clinical indications for synthetic colloid use? (2)
- resuscitation and sustained vascular expansion
- oncotic support for hypoproteinemia
What are the potential adverse effects of using synthetic colloids? (2)
- dose-dependent coagulopathy (dilution of clotting factors, impaired platelet aggregation, interference with clotting factors)
- renal injury (don't use in renal patients)
What is the natural colloid and where is its volume of distribution?
- vascular volume--> expands intravascular fluid equal to amount given
What are clinical indications for use of natural colloids (plasma)? (1)
What is a potential adverse effect of administering natural colloids (plasma)? (1)
What is the newer synthetic colloid formulation, and what is it's advantage?
VetStarch- decreased chance of coagulopathy
What are advantages to using IV route of administration of fluids? (3)
- direct vascular access
- rapid administration possible
- almost all types of fluids can be given IV
IV fluid administration is preferred for... (4)
resuscitation, anesthetic patient, significant dehydration and ongoing losses, critically ill patients
What are the advantages of placing a peripheral IV catheter (as opposed to central)? (3)
- faster/ easier to place
- shore, large bore for faster administration
- less expensive
What are disadvantages to placing a peripheral IV catheter (as opposed to central)? (3)
- position limb movement can cause occlusion
- relatively short term
- hypo-or hypertonic fluids and some drugs can be irritating
What are advantages to placing a central catheter (as opposed to periph)? (4)
- safer administration of hypo- or hypertonic fluids
- large bore for rapid administration
- measurement of central venous pressure available
- serial blood sample possible
What are disadvantages of placing a central IV catheter (as opposed to a periph)? (3)
- time/ cost/ expertise
- might require sedation
- caution with bleeding disorders
What are potential complications with catheterization for fluid administration? (5)
- extravasation of catheter
- thrombosis/ thromboembolism
- infection (at catheter site or blood infection/ bacteremia)
- catheter fragment foreign body
When is the intraosseous route of fluid administration used?
neonates and avian
What are advantages to using the intraosseous route for fluids? (3)
- access to vascular space when IV not possible
- equivalent to IV
- relatively rapid placement
What are disadvantages to using the intraosseous route for fluids? (3)
- short-lived access
- technically challenging
When is SQ route of fluid administration applicable?
for administration of fluid for gradual absorption and distribution across fluid compartments
Uptake of SQ fluids is dictated by... (3)
- hydration status
- peripheral perfusion
- body temperature (worse absorption in cold patients)
What types of fluids can be given SQ?
near-isotonic fluids (except: do not give dextrose SQ...it hurts!)
Advantages of SQ fluids? (3)
practical, less expensive, out-patient basis
SQ fluid administration is preferred for... (3)
- mild to moderate dehydration
- prevention of dehydration for anorexic/ NPO patients
- unable to hospitalize
What are disadvantages of administering SQ fluids? (4)
- unreliable absorption
- cannot be used for resuscitation or replacement in shocky patients
- limited in options of types of fluid
- may cause pain/ irritation or pressure necrosis (uncommonly)
What are advantages of enteral administration of fluids? (3)
- most natural way to provide fluids
- low cost
- can also provide nutritional support
What are disadvantages of enteral administration of fluids? (4)
- need functional GI tract
- can't keep up with losses
- not effective for resuscitation
- potential risk for aspiration pneumonia