Fluid Therapy Flashcards
Osmolarity
Expresses concentration of dissolved particles
- osmole/milliosmole
- isosmolar solutions are 310 mOsm/L
- quantitative
- isotonic: same osmolarity as inside of cell
- hypotonic: osmolarity less than the cell
- hypertonic: osmolarity greater than the cell
Tonicity
Effects of a fluid on a cell it surrounds
- isotonic: causes no volume change to cells placed in it
- hypertonic: cause cells to shrink
- hypotonic: cause cells to swell
- qualitative
What is “fluid diuresis”?
Fluid infusion rates in excess of maintenance needs to promote:
- removal of drugs/toxins
- increase GFR
- increase urine production
- value of 2-2.5x normal maintenance rates is common
Crystalloid
Solution that diffuses readily through semipermeable membranes
- is capable of being crystallized
- solutions with major electrolytes or dextrose as solutes
In what form of shock is fluid therapy contraindicated?
Cardiogenic shock
- heart failure
- renin-angiotensin system is in overdrive, so patients are already volume overloaded = want to minimize amount of fluids given
What are the main causes of hypovolemic shock?
- rapid blood loss
- severe dehydration from fluid loss (vomiting, diarrhea, polyuria)
Explain what “distributive shock” is and the subtypes of shock that fall under its general categorization
Relative hypovolemia due to vasodilation, NOT fluid loss!
- septic/endotoxic shock
- anaphylactic shock
- Addisonian crisis (half hypovolemia, half distributive)
- neurogenic shock
What are the ions commonly found in a Balanced Electrolyte Solution (BES, also known as a Multi‐Electrolyte Solution)?
- lactated ringers solution –> sodium lactate
- plasmalyte-A –> sodium acetate, sodium gluconate
- normasol-R –> sodium acetate, sodium gluconate
Contrast “Replacement” versus “Maintenance” crystalloid solutions as to relative sodium content
and when they are indicated.
Replacement isotonic crystalloids:
- lactated ringers: 30 mg Na lactate = mild metabolic acidosis, primary replacement fluid
- normal saline (0.95%) = metabolic alkalosis
- plasmalyte-A: 368 mg Na acetate, 502 mg Na gluconate
- normosol-R: 22mg Na acetate, 502 mg Na gluconate (questionable)
Briefly explain why oral electrolyte solutions provide better rehydration than oral water. Indicate
the role of sodium and glucose in the solution
Na-glucose symporter has NaK ATPase on basal surface –> pulls Na into the blood or lymphatics, while glucose goes through the uniport
- oral electrolytes are high in Na and glucose, without Na, intestinal glucose is not absorbed
- wherever Na goes, water follows!
Explain how D5W is considered isotonic in vitro but mildly hypotonic in vivo
When given to the animal, dextrose goes into the cell, but water stays extracellularly, creating a hypotonic environment
Why is D5W not considered appropriate for use in hypovolemia?
Very little D5W stays in the vascular space, do not want to use for volume expansion
- if animal is in shock, you need to use a solution with sodium in it!
When are hypertonic dextrose solutions indicated?What risks or side‐effects can they cause?
50%, 20%, and 10% dextrose used to stop hypoglycemic seizures and as an energy source (TPN, PPN)
- do NOT give extravascularly, injures tissues due to high hypertonicity!
- do NOT give with active CNS hemorrhage
- > 20% dex should not be given in peripheral vewin due to phlebitis
- rapid infusion could cause osmotic diuresis (give 0.5 g/kg body weight/hr)
- causes volume overload in heart or kidney failure
What are the pros and cons for hypertonic saline use in managing hypovolemic or distributive shock.Explain its mechanism, relative duration, and what follow‐up fluid therapy is warranted.
- 2% (central catheter), 3% (central or peripheral catheter) hypertonic saline
- pros: osmotically draws fluid rapidly into vascular space from interstitium to maintain bp for 30-60 min, <1 ml/kg/min in shock and over 15-20 min for cerebral edema
- cons: need to follow with isotonic crystalloids to replenish interstital fluid loss, may get phlebitis, avoid in uncontrolled hemorrhagic shock, hypernatremic patients, markedly dehydrated pateints
Name a use of hypertonic saline other than for management of shock.
Cerebral edema
Name the two common concentrations of hypertonic saline and which can be given in a peripheral vein
- 7.5%: IV infusion in central catheter at 3-8 ml/kg
- 3%: IV infusion in central or peripheral catheter at 7.5-20 ml/kg
What are the indications for use of hetastarch?What are its potential toxicities or side‐effects?
Used for vascular volume expansion, if you are only trying to maintain osmotic pressure and for hypoproteinemia
- recommended upper dose: 20 ml/kg/day in dogs (10-20 cats), any higher is too hyperosmolar
- volume overload is possible (do not use in heart failure, kidney failure)
- coagulopathies from platelet inhibition at very high doses
- FDA black box warning in humans due to kidney injury/death
Fresh whole blood
Contains RBC, platelets, leukocytes and plasma proteins including clotting factors!
- transfused within 4-6 hours following collection
Match the clinical signs and percent dehydration associated with mild, moderate, and severe
dehydration.
- 5%: mild loss of skin elasticity
- 8%: slight sinking of eyes, prolonged skin tenting, capillary refill 2-3 sec
- 10%: animal semi-comatose, >3 sec capillary refill, severe skin tenting and sinking of eyes, cool extremities, tachycardia
Be able to calculate the required fluid volume for intravenous replacement therapy based on percent deficit, maintenance fluid requirements, and ongoing losses.(Already addressed in Calculations lecture.)
Amount of fluid = deficit + maintenance + extraordinary losses
- deficit = % deficit x kg
- maintenance = 40-60 mls/kg/day (low for large, high end for small animals) x kg
- extraordinary losses = measured or estimated losses from disease
What is/are the indication(s) for oral fluid therapy?
Given for 5-6% dehydration
- if the GIT is okay, animal is willingly drinking and isotonic solutions (NOT dextrose) can be used
- used in calves, adult cattle with a stomach pump
What is/are the indication(s) for SC fluid therapy?What fluids are appropriate for SC administration?
5-6% dehydration, given in small animals or calves
- use isotonic fluids, not isotonic dextrose (lactated ringers, balanced electrolytes)
- spread amount over different spots
What is the rate of isotonic fluid therapy use in the initial management of shock for dogs versus
cats?Over what time frame should the first ¼ of that dose be given and the patient reassessed?
- 80 mls/kg/hr in dogs
- 50-55 ml/kg in cats
Give first 1/4 of dose (20 ml/kg) and reassess in 15 minutes. Decrease as needed
What is the recommended rate of fluid therapy during anesthesia in dogs and cats?
- dogs: 5 ml/kg/hr
- cats: 3 ml/kg/hr
