Exam 1 - Fluid Therapy Flashcards
dehydration affects the _______ where volume depletion affects the ______
ICF - affected by dehydration
ECF - affected by volume depletion
what are the hallmarks of dehydration?
occurs over time - along a continuum
ICF volume is lost when insensible losses are not replaced
simple dehydration has mild clinical signs
severe dehydration mimics volume depletion
what are the hallmarks of volume depletion?
acute injury or disease
ECF volume is lost acutely - ICF volume can be normal
negative impact on cardiovascular parameters
EMERGENCY
what clinical signs/parameters are seen in a patient with dehydration when trying to differentiate between it & volume depletion?
simple dehydration
heart rate: mild tachycardia
mucus membrane/CRT: tacky mucus membranes & increased CRT
jugular vein fill: normal
peripheral pulse pressure: normal
extremity temperature: WNL/cool
mentation: BAR/QAR
skin tenting: +/- present
what clinical signs/parameters are seen in a patient with volume depletion when trying to differentiate between it & dehydration?
volume depletion/decreased ECV
heart rate: moderate to severe tachycardia
mucus membrane/CRT: +/- moisture/increased CRT
jugular vein fill: prolonged
peripheral pulse pressure: reduced
extremity temperature: cool/cold
mentation: +/- obtunded
skin tenting: +/- normal
what are the 4 phases of fluid therapy?
- resuscitation
- rehydration
- maintenance
- ongoing loss
when do you need to pursue resuscitation in a patient? what does that mean physiologically?
when they are showing signs of decreased effective circulating volume - patient is volume depleted
patient is losing body water & electrolytes
what is the goal of resuscitation in fluid therapy?
improve circulating volume & blood pressure
prevent circulatory collapse
improve O2 delivery to tissues
what is the body’s homeostatic response to volume depletion? what is the purpose of them?
decreased ECF volume leads to decreased venous return to the right atrium -> decreased cardiac output
activation of the autonomic nervous system, RAAS, & AVP
strive to maintain O2 delivery to tissues in the body, but these mechanisms are short-lived
what is the shock dose of fluid used for companion animals? how is it given?
80-90 ml/kg - given 1/4 bolus at a time using isotonic fluid
T/F: in fluid therapy for volume depletion, your goal is reaching the ECF quickly
true
what percentage of dehydration do you see clinical signs with?
5%
what lab abnormality is the hallmark of dehydration?
hypernatremia
what is the body’s homeostatic response to dehydration?
CNS osmoreceptors sense a change in plasma osmolality - increase in serum sodium triggers central osmoreceptors
stimulates thirst!!!
what is the mechanism of dehydration in the body?
on a daily basis, ICF contributes water to prevent dehydration
with decreased water consumption, hypertonicity of ECF occurs (increase in effective osmols) which stimulates water movement from the ICF
what is the formula for calculating a patient’s dehydration deficit for fluid therapy?
deficit (L) = % dehydration X BWT (kg)
what clinical signs are seen in an animal with 5-7% dehydration?
mild dehydration
decreased skin turgor & slightly tacky mucus membranes
what clinical signs are seen in an animal with 8-10% dehydration?
moderate dehydration
depressed mentation, tacky mucus membranes, & CRT > 2-3 seconds
what clinical signs are seen in an animal with >10% dehydration?
severe dehydration
cool extremities, poor perfusion, & CRT > 4 seconds
T/F: loss of body water is not an acute event
true - not like blood loss/hemorrhage
it occurs over time
use ____________ to replace body water over time
% dehydration of your patient
how is rehydration done in fluid therapy for a dehydrated patient?
initial bolus (1.2 of the deficit) is patient dependent & many small animal patients may not require a bolus
replace remaining 1/2 (or whole amount) over the next 12 hours (or may be able to deliver entire deficit over time period without a bolus)
what route of fluid administration is appropriate for resuscitation efforts?
intravenous
what route of fluid administration is appropriate for rehydration efforts?
in reality - depends on % dehydration but probably intravenous in small animal patients
what is phase 3 of fluid therapy?
maintenance
what are the daily fluid requirements for dogs, cats, & horses?
dogs - 60 ml/kg/day
cats - 45 ml/kg/day
horses - 50 ml/kg/day
when should you provide maintenance fluid therapy for a patient?
patient is unable to intake the appropriate amount of their daily water from:
sickness, physical inability, or reduced dietary/forage intake (horses)
what is included in maintenance fluid therapy?
daily water requirements & necessary electrolyte supplementation when necessary (dependent on patient needs, so monitor bloodwork for electrolytes and renal function)
what is ongoing loss when it comes to fluid therapy?
most difficult replacement to predict in fluid therapy
fluid loss through blood loss, vomit, diarrhea, feces, manure, gastric reflux, etc
what is the most common type of solution used for fluid therapy in veterinary medicine? what is it? what are some examples?
crystalloids
fluids that mimic the composition of the ECF with Na/Cl being the primary electrolytes
LRS, normosol-r, & 0.9% saline
how do crystalloid fluids work?
substance in a solution that is diffusible across a semi-permeable membrane
so designed to leak from the vascular space into the interstitium
what is seen within 30 minutes of administration of crystalloid fluids to a patient?
1/4 of volume administered remains in the intravascular space
3/4 diffuses out of the vasculature into the interstitium
allows for brief volume expansion without causing electrolyte imbalances or fluid shifts from the ICF
what is tonicity?
osmotic pressure of a solution based on the number of particles per kilogram of a solution
what is the tonicity of isotonic crystalloids?
osmotic pressure equivalent to the ECF, so tonicity is equal to that of plasma
1 mEq = 1 mmol = 1 mOsm, 280 mOsm/L
what is the tonicity of hypotonic crystalloids? what is the risk with giving them?
osmolality is lower than plasma
can lead to the swelling/rupture of RBC
what is the tonicity of hypertonic crystalloids? what is the risk with giving them?
osmolality is greater than plasma
RBC can shrink
what are some examples of when you should use isotonic crystalloids for a patient?
resuscitation for volume depletion/shock patients
maintenance fluids, treating disease, wound irrigation, peritoneal/pleural lavage
when should you be very cautious when using isotonic crystalloids in a patient?
if they have decreased capillary oncotic pressure (low protein), head trauma, or heart failure
what is small volume resuscitation?
when isotonic fluids aren’t enough - combo of crystalloid & colloid fluid administration
combine isotonic, hypertonic, & colloid therapy - acts as a band-aid until large volumes of crystalloid fluids can be administered
T/F: small volume resuscitation can be used in replacement for isotonic crystalloid therapy
false - doesn’t take its place
how does hypertonic saline work?
creates hypertonicity of ECF, so redistribution of fluid from the ICF is triggered
causing 2-3 times the amount of volume expansion that is short lived
hypertonic saline provides what?
immediate expansion of the vascular volume
what are some examples of situations where hypertonic saline should not be used?
never in a patient with poor ICF volume - not dehydrated!!!
never as a replacement for isotonic fluid therapy
not maintenance fluid therapy - always follow with isotonic crystalloid fluids & need to prevent persistent hypernatremia
when should hypertonic saline for small volume resuscitation be used?
prior to arrival at referral/trauma center
what is the difference between hypertonic saline & a colloid?
colloid contains molecules which exert colloid oncotic pressure
increased COP, hypertonic saline just expands ECF
what is responsible for COP in circulation?
albumin - 80% of COP provided
how do colloids work?
large molecules in colloid solution remain in the vascular space & act by drawing fluid from the interstitium into a vessel to increase COP
what are some examples of colloids used in veterinary medicine?
endogenous colloids - plasma
synthetic colloids - hetastarch
blood products - whole blood, packed red blood cells
what are some examples of when colloids should be used for a patient for their fluid therapy?
severe protein loss, PLE, endotoxemia
what is kMAX?
0.5 mEq/kg/hr - can’t exceed
what is the fluid shock dose for cats?
50 ml/kg
what are the body fluid compartments in mammals? what is included in each?
ICF - 2/3 of TBW
ECF - 1/3 of TBW, with 1/4 being intravascular compartment, 1/2 interstitial, & 1/4 transcellular
how much of the body is made up of water in mammals?
60% of body weight in kgs
the total blood volume in most patients is what?
~8-9% of body weight in kg - resides within the intravascular space of the ECF
what is the largest component of the ECF?
interstitial fluid space
why do we see plasma highly concentrated with proteins in the body?
the pores of the capillary cell membranes are highly permeable to almost all solutes in the ECF except for plasma proteins
so proteins are higher in the plasma than the interstitium
what is blood plasma?
non-cellular (liquid) portion of blood that communicates continuously with the interstitial fluid through a series of pores in the capillary cell membranes
what is the mechanism seen from proteins that maintains fluid within the vascular space to support vascular volume & patient blood pressure?
create colloid oncotic pressure
plasma proteins are negatively charged & attract cations (Na & K) from the interstitium into the vascular space
the uneven charge favoring the plasma/intravascular space & presence of high proteins within plasma act to maintain fluid within the vascular space to support vascular volume & patient blood pressure
what is the primary ECF effective osmole?
sodium cation - followed by anions chloride & bicarbonate
what is the primary ICF effective osmole?
potassium cation - followed by anion phosphate (PO4-) & ICF proteins
what is dehydration?
loss of body water
0.9% saline is the ideal fluid for what type of disease? what should you not use it for? why?
ideal for a patient with hyperkalemia
don’t use for resuscitation - risk of development of hyperchloremic metabolic acidosis
when would you use hypotonic saline for a patient?
patients with chronic hyponatremia - their cells produce idiogenic osmoles as a defense mechanism against dehydration to pull water from the interstitium to maintain normal cellular function
must replace sodium slowly with a fluid that closely resembles their abnormal plasma tonicity to prevent cell swelling
what patients need hypertonic saline? how is hypertonic saline administered?
fluid of choice in a hypovolemic patient with primary ECF fluid/electrolyte loss
quickly increases the blood volume by 2-3 times the amount of solution administered
for every liter of hypertonic given, ten liters of isotonic fluid should follow as a replacement for the ICF debt
what is the most effective route of fluids given for a horse with large colon pelvic flexure feed impactions?
nasogastric tubing - 4-6 L per dose
what is the goal of the resuscitative phase of fluid therapy?
restore vascular volume & fluid deficit & rehydration phase to restore the ICF & interstitial fluid deficits
T/F: in a patient suffering shock due to uncontrolled hemorrhage such as abdominal bleeding should not receive a shock dose of fluid
true
why do we not see signs of dehydration in patients that are <5% dehydrated?
less than 5% of water loss is managed by the ICF space as it contributes fluid to the ECF to maintain water balance when the patient has a history of water restriction or decreased consumption
T/F: water movement into & out of the cell is only determined by the osmotic pressure gradient, so at equilibrium, ICF osmolarity is equal to ECF osmolarity
true
when giving a patient hypertonic saline, what happens to the osmolarity, ECF, & ICF of the cells?
ECF volume & osmolarity INCREASE - volume injected plus the volume that moves into the ECF from the ICF increases both volume & overall osmolarity
ICF volume DECREASES & osmolarity INCREASES - movement of fluid into the ECF, but the osmolarity increases
when giving a patient hypotonic saline, what happens to the osmolarity, ECF, & ICF of the cells?
ECF volume INCREASES while osmolarity DECREASES - volume injected stays in ECF but loss of the volume that moves into the ICF
ICF volume INCREASES & osmolarity DECREASES - volume moves into ICF from ECF increasing the volume but decreasing the osmolarity
when giving a patient isotonic saline, what happens to the osmolarity, ECF, & ICF of the cells?
ECF volume INCREASES & distributes between vascular & interstitium but osmolarity remains unchanged
ICF volume stays that same & so does osmolarity because no osmotic gradient was created
what is molality?
number of moles of a solute per liter of solvent (water)
what is molarity?
number of moles of a solute per liter of solution
what is osmolality?
concentration of osmotically active particles in solution expressed in terms of osmoles of solute per kilogram of solvent (water)
what is osmolarity?
concentration of osmotically active particles in solution expressed in terms of osmoles of solute per kilogram of solution
T/F: “X”% of solution means ‘X’ g/100 mls of solution
true
