Fluid Therapy – Small Animals – Flashcards
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What is the fluid composition of dogs and cats?
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Body is 60% water. Variations based on: age, lean body mass, obesity, gender.
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How is water in the body distributed?
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66% Intracellular fluid 24% Interstitial fluid 10% Blood
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How do cell membranes and endothelium differ in permeability?
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Cell membranes - permeable to water, selectively permeable to ions. Endothelium - permeable to water, large proteins (i.e. proteins, colloids) can NOT cross unless very fenestrated.
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How does fluid composition in the intracellular space differ from the interstitial and vascular space?
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Intracellular space: K+ and Phos. with protein. Interst. and vasc. space: Na+ and Cl- with HCO3-.
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What are sources of fluid gain?
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Drink Food Metabolism
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What are sources of fluid loss?
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Vomit/diarrhea Urine Wound exsudates Respiration/evaporation Salivation
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What is the *daily fluid maintenance *requirement (in mL)?
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*30 x BW kg + 70* (if 2-100 kg BW)
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What is the daily fluid maintenance requirement for a 30 kg MN labrador retriever?
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30 x 30 + 70 = 970 mL 970ml/24=32.6ml/kg/d
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What is the daily fluid maintenance requirement for a 3 kg FS yorkshire terrier?
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30 x 3 + 70 = 160 mL 160ml/24=53.3mL/kg/d
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How can hydration be clinically assessed?
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*Hydration* refers to the *extravascular* compartment (IS, IC): hydration of mucous membranes skin elasticity enopthalmus dullness of cornea Assesses whole body.
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How can perfusion be clinically assessed?
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*Perfusion* refers to cardiac output, *intravascular* volume, and vascular tone: heart rate, pulse quality jugular vein distention MM color, CRT appendage temperature arterial blood pressure urine output acid-base status Only assesses what is happening in intravascular space.
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How are hydration and perfusion related?
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Hydration and perfusion are intertwined. A dog that is severely dehydrated will be hypovolemic and have decreased perfusion.
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What are physical signs of <5% dehydration?
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<5% not detectable
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What % dehydration does subtle loss of skin elasticity occur?
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5-8% dehydration (most common)
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What % dehydration does definite delay in return of skin to normal position, slightly prolonged CRT and possible sunken eyes occur?
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6-8% dehydration
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What % dehydration does tented skin that stands in place, definite prolongation of CRT, dry mm, and possible signs of shock occur?
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10-12% dehydration
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What % dehydration does definite signs of shock and imminent death occur?
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12-15% dehydration
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How do you determine the *fluid deficit* (mL)?
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*BW (kg) x % deficit x 10*
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What is the fluid deficit of a 20kg dog with 5% dehydration?
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20 x 5 x 10 = 1000mL needed to correct dehydration Even mild dehydration in a relatively small dog requires surprisingly large amounts of fluid to correct.
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What are signs of *mild (compensated) hypovolemia*?
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HR: 130-150 Normal/pink mm CRT < 1 sec Increased pulse Metatarsal pulse ++
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What are signs of *moderate hypovolemia*?
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HR: 150-170 Pale pink mm CRT 2 sec Moderately decreased pulse Metatarsal pulse +
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What are signs of *severe (decompensated) hypovolemia*?
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HR: 170-220 White/gray/muddy mm CRT >2 sec Thready pulse Metatarsal pulse -
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What are *crystalloids*?
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Aqueous solution of small-sized particles that can freely move across capillary walls (ions). They are defined by their composition, osmolality, acidify/alkalinizing properties and their indication for replacement or maintenance fluids.
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What is the essential fact of fluid Tx?
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*Only 25-30%* of the administered volume of *isotonic crystalloids remains in the vascular space 30 min. after* rapid administration. Potential for dog to do well for 30 min then crash back to square one - constant monitoring important. *Desirable in a dehydrated patient but not a hypovolemic patient.*
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What is osmolality?
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Concentration of osmotically active particles in a solution (NOT related to size, weight, shape change, etc). It is a measure that gives you an indication of osmolar active particles (large colloids cannot cross capillary wall).
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What is the calculated plasma osmolality?
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2[Na] in serum + BUN/2.8 + glucose/18
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What is the reference range of plasma *osmolality* for dogs and cats?
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Around *300 mOsm/kg* Dog:290-310 Cat: 290-330
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Which fluids are most often used for *replacement solutions*?
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*Isotonic* solutions
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Which fluids are most often used for *maintenance solutions*?
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*Hypotonic* solutions They can *penetrate intracellular space*.
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What are examples of *isotonic crystalloids*?
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0.9% NaCl Lactated Ringers Normosol-R All ~300 mOsm/L like normal plasma.
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What are examples of *hypotonic crystalloids*?
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0.45% NaCl with 2.5% glucose Osmolality less than plasma. Initially isotonic, then hypotonic after liver consumes the glucose - just free water left.
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What are examples of *hypertonic crystalloids*?
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7.2% NaCl Vastly hypertonic (2464 mOsm/L)
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What are harmful effects of crystalloids?
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Overhydration Hemodilution Rebleeding
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When is overhydration a risk with crystalloids?
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Edema (interstitium, lung, brain) especially if low oncotic pressure and potentiated if colloid osmotic pressure is decreased (i.e. hypoalbuminemia) Lung contusions, brain trauma, oliguria/anuria, CHF.
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When is hemodilution a risk with crystalloids?
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Patients with anemia, hypoproteinemia, hypocoagulability
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When is rebleeding a risk with crystalloids?
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Freshly lacerated/ruptured blood vessels that clotted under low BP. Fluid Tx increases BP and then clot is no longer strong enough.
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What are hypertonic crystalloids?
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Very concentrated NaCl solutions (7.5%). Draw interstitial and some intracellular fluid into the intravascular space. Don't have to give large volumes to get short-lived vascular filling. Rapidly equilibrate between the 3 compartments.
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When should hypertonic crystalloids NOT be used?
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*Never use in dehydrated patients*
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When are *hypertonic crystalloids indicated*?
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*Rapid vascular expansion* desirable (severe hypovolemia, large patients). Patients' risk for increased ICP or pulmonary contusions for which interstitial edema should be avoided.
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When are *hypertonic crystalloids contraindicated*?
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Severe dehydration, hyperNa (hyperosmolality), volume overload (HF), uncontrolled hemorrhage
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What are *colloids*?
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Aqueous solution of natural or synthetic large size particles that cannot cross the capillary wall.
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What are examples of *colloids*?
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Natural: whole blood, plasma, 25% hum. albumin Synthetic: 6% hetastarch
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What is a benefit of synthetic vs. natural colloids?
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No risk of immune reaction from foreign species.
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Which colloids can be used to immediately increase COP? Which can sustain COP?
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Hetastarch and 25% albumin can immediately increase COP but only hetastarch can sustain it (25% albumin has too short a half life)
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Which colloids carry O2?
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Whole blood
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Which colloids contain albumin and coag factors?
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Whole blood and plasma
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Which *colloid* is best to use to *increase vascular filling*?
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*6% hetastarch*
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What are *indications for colloids*?
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1. Vascular filling - hypovolemic shock, septic shock 2. Maintenance of oncotic pressure 3. Anti-thrombotic effect
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What are *side effects* of *synthetic colloids*?
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1. Excessive volume expansion 2. Platelet dysfunction 3. Depression of phagocytosis 4. Depression of albumin synthesis
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When is *excessive volume expansion* a concern with *synthetic colloids*?
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*CATS* - can cause vomitting and hypotension
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When is platelet dysfunction a concern with synthetic colloids?
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Hypercoagulable patients or those with low or dysfunctional platelets.
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When is depression of albumin synthesis a concern with synthetic colloids?
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Moderately to severely hypoalbuminemic patients.
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What is the best route for fluid administration?
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Intravenous - peripheral/central
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When should you administer fluids intraosseously?
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Puppies and kitties!
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What are the only fluids you should use subcutaneously?
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Isotonic fluids
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Which route of administration is not recommended?
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Intraperitoneal
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What are normal sensible and insensible fluid losses?
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Sensible losses (urine output): 24-48 mL/kg/d Insensible losses (fecal, respiratory): 13-20 ml/kg/d
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What are abnormal ongoing fluid losses?
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V, D, PU, wound exudates
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What is the *fluid rate for isotonic crystalloids*? What is the exception?
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Usually replace at the rate it was lost. Acute loss = 6-12 hrs Chronic loss = 12-24 hrs Exception: shock patients require higher rates, HF patients require more cautious rates.
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What are the *isotonic fluid rates in hypovolemia for dogs*?
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Dog: *20 mL/kg bolus*, followed by additional 10-20mL bolus q15 min based on reassessment (max. 100mL/kg)
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What are the *isotonic fluid rates in hypovolemia for cats*?
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*10 mL/kg bolus* followed by 5-10 mL/kg q15-30 min. based on reassessment (max. 60mL/kg)
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What are *hypertonic fluid rates*?
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7.2% NaCl: One dose of *3-6mL/kg over 5 min*. Continue with colloids (and possibly isotonic crystalloids)
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What are *side effects in cats* to *hypertonic crystalloids*?
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*Cats* may occasionally develop *respiratory arrest* or *vagal reflex bradycardia*.
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What are *hetastarch fluid rates*?
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*Dog: 5-10 mL/kg* (max 20 mL/kg) *Cat: 2.5-5 mL/kg* (max 10mL/kg)
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If hetastarch is given simultaneously with crystalloids for shock treatment, what dose should be adjusted?
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Initially decreased crystalloid dose by 40-60%
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What is the "maintenance" dose for patients with low oncotic pressure? What should you be cautious of?
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0.5-2 mL/kg/hr Beware side effects, use with care in cats
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What are monitoring parameters for fluid therapy?
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1. Volume status 2. Hydration status 3. Solute status
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How do you monitor volume status?
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Preload parameters and forward flow parameters
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What are preload parameters?
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1. Venous volume - ease of venous distension, CVP, CVC 2. Heart chamber - left ventricle @ ED, left atrium
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What are forward flow parameters?
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1. Large arteries - pulse quality, arterial blood pressure 2. Precapillary arteriolar vasomotor tone - mm color, CRT 3. Tissue perfusion - appendage temp., urine output, lactic acidosis, central venous partial O2 pressure
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What are hydration status parameters?
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Skin tenting tendency Day-to-day changes in BW Urine output and conc. MM moistness Blood solute conc.
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What are solute status parameters?
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PCV of Hb Albumin/COP Potassium Sodium Bicarbonate Glucose
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What is *central venous pressure (CVP)* directly proprotional to? Where do you place the catheter?
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CVP directly proportional to blood volume in AVC and venous tone. Place jugular catheter in anterior vena cava (AVC).
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How will *hypovolemia or venodilation* affect CVP?
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*Decreases CVP*
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How will *fluid therapy or venoconstriction* affect CVP?
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*Increase CVP*
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What should you do if an animal's CVP is 0 to 10 cmH2O?
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Nothing! This is normal, no fluids needed.
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What should you do if an animal's CVP is -5 to 5 cmH2O?
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The animal is hypovolemic. Increase fluids if <0 cmH2O.
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What should you do if an animal's CVP is 5 to 15 cmH2O?
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The animal is hypervolemic. Slow or discontinue fluids if > 10 cmH2O.
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What are practical end points to monitor in acute fluid therapy?
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HR: 80-140 (dog), 180-200 (cat) MM pink MAP >80 mmHg SAP >120 mmHg CVP 5-10 cmH2O Urine output >1-2 ml/kg/hr
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What are *clinical signs* associated with *early volume overload*?
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Shivering Restlessness Serous nasal discharge Nausea, poss. vomiting Poss. polyuria Tachypnea
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What are *clinical signs* associated with *late volume overload*?
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SC edema (hock joint, intermandibular space) Chemosis Tachypnea, cough, pulmonary crackles, dyspnea Depressed mentation Tachycardia, bradycardia
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What type of fluids are appropriate for a 3kg cat with decompensated CKD and 8% dehydration? What is the fluid deficit? What is the maintenance? Total if deficits replaced over 24 hr? If deficits replaced over 12 hr?
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*Isotonic: Ringer's lactate* *Deficit* = 3kg x 8% x 10 = 240mL = 10mL/hr if 24 hr or 20 mL/hr if 12 hr *Maintenance* = 30 x 3kg + 70 = 160/day = 7mL/hr 24 hrs = 17 mL/hr 12 hrs = 24 mL/hr
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What type of fluids are appropriate for a 50kg dog with GDV in the hyperdynamic phase of shock?
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*Ringer lactate (20 mL/kg )* = 20 x 50 = 1000mL rapid IV bolus using 2 large bore cephalic catheter. Repeat after 15 and 30 min. Total crystalloids volume = 3L *Hetastarch (10 mL/kg)* = 10 x 50 =500 mL IV bolus over over 15-20 min
