Applied Fluid Therapy Flashcards
What are the overall contents that make up the fluid compartments? How does this relate to a 10 kg dog and 5 kg cat?
OVERALL TOTAL BODY WATER = 60%
- 40% ICF
- 20% ECF —> 15% Interstitial, 5% plasma
10 KG DOG
- TBW = 6 L —> 4 L ICF, 1.5 L interstitial, 0.5 L plasma
5 KG CAT
- TBW = 3 L —> 3 L = ICF, 0.75 L interstitial, 0.25 L plasma
What are the 3 types of fluid disturbances?
- changes in volume - dehydration, blood loss
- changes in content - hyperkalemia, hyponatremia
- changes in distribution - pleural effusion, pulmonary edema
treat root causes and correct prior to anesthesia if possible
What are the 3 stages of dehydration?
- mild (5%) - dry MM and loss of skin turgor
- moderate (8%) - worsened MM and turgor with rapid, weak pulses and exophthalmos
- severe (> 10%) - thready pulses, hypotension, altered consciousness (obtunded, not responsive)
How is dehydration corrected? How is this altered if the patient is hypernatremic? What fluid is commonly used?
BW (kg) x % dehydration x 1000 mL = mL needed to replace deficit
0.6 kg x (1 - [Na]/145) = water deficit in L
5% dextrose in water, but can reduce Na (stop if more than 0.5 mEq/L/hr)
How is hypovolemia corrected? What if the patient is hypokalemic?
expand intravascular volume with crystalloids at shock doses and/or colloids
can use separate IV access to administer K without exceeding 0.5 mmol/kg/hr
How do isotonic fluids work? What are 4 examples?
distribute fluids into ECF due to electrolyte content and osmolality being similar to the plasma
- 0.9% NaCl
- LRS
- PLA 148 / PLA
- Norm R
How do hypertonic fluids work? What is the most common example?
raises osmolarity to shift fluid from ICF to ECF
hypertonic saline (7.5% NaCl)
How do maintenance fluids work? What are 2 examples?
hypotonic - distribute to all 3 compartments (avoids cerebral edema!)
- 0.45% NaCl / 2.5% dextrose
- PLA 56
What are 3 examples of shock fluids? How do they work?
- Vetastarch artificial colloid
- whole blood, plasma, packed RBCs
- hypertonic saline (7.5%)
holds fluid in vascular space
What are the shock doses of crystalloids in dogs and cats? What is their function? Why must they be used cautiously?
- DOGS = 90 mL/kg
- CATS = 50 mL/kg
stabilizes the cardiovascular system
small patients with a lot of room temperature fluids causes hypothermia
What is the point of combining colloids and crystalloids? How is this done in dogs and cats?
increases vascular volume and replenishes interstitial deficits
- DOGS = colloids 5-10 mL/kg + crystalloids 40-45 mL/kg
- CATS = colloids 1-5 mL/kg + crystalloids 25-27 mL/kg
What colloid is especially used in larger patients with large volume loss? When is it not used?
hypertonic saline - translocated fluids from interstitium to intravascular space (4-5 mL/kg dog, 2-4 mL/kg cat) to achieve the greatest cardiovascular benefit
if patient is dehydrated or hypernatremia
How are daily fluid maintenance rates calculated for dogs and cats? What is it?
- DOGS = 132 x BW^0.75 = 2-6 mL/kg/hr
- CATS = 80 x BW^0.75 = 2-6 mL/kg/hr
amount of fluid to maintain normal fluid balance
What is the most common replacement fluid used? What long-term complication is associated?
lactated ringers - isotonic polyionic crystalloid that replaces lost body fluids and electrolytes
can cause electrolyte imbalance - hypernatremia, hypokalemia —> monitor serum electrolytes every 24 hrs
What are 4 functions of anesthesia fluids?
- correct ongoing fluid loss
- support cardiovascular function
- support maintenance of whole-body fluid
- counter negative effects of anesthetic agents - vasodilation, hypotension
What are some risks and adverse effects when too much anesthetic fluids are used?
- vascular fluid overload
- increased BW and lung water
- coagulation defects
- reduced GI motility and tissue oxygenation
- increased infection rate
- decreased PCV and TP
- hypothermia - room temperature fluids
What patients require altered anesthesia fluid rates?
- cats
- renal disease
- cardiovascular disease
(typically lower rates)
What should maintenance rates + replacement rates not exceed? What should be done if the procedure is more than 1 hour?
10 mL/kg/hr
reduce fluid rate by 25% hourly until daily maintenance rates are reached
What are the overall basic maintenance anesthesia rates used in cats, dogs, and horses?
CATS = 3 mL/kg/hr
DOGS = 5 mL/kg/hr
HORSES = 5-15 mL/kg/hr
What are 6 consequences of volume overload?
- cerebral edema
- pulmonary edema
- myocardial edema
- hepatic congestion
- increased venous pressure
- tissue edema
What does the revised Starling equation state? How does this affect our approach to anesthetic fluids?
hydrostatic and oncotic pressure gradients are not only across capillary wall, but across functional and physical barrier known as the glycocalyx
- colloids are not as effective as we once thought
- fluid therapy is not benign and should be considered similar to administration of drugs
What is the new approach to fluid therapy and anesthetic hypotension?
try a small dose of a fluid bolus
- if there is improvement, the patient is a fluid responder
- if there is no improvement, the patient is not a fluid responder and more fluids will NOT improve their condition
- MAX FLUIDS = 20-30 mL/kg
What drug is recommended to anesthesia-induced refractory hypotension? How does it work?
Dopamine
- has action of alpha-1 and beta-1 receptors to improve arterial blood pressure and cardiac output
- counteracts negative effects of inhalants on vasculature and heart
When are colloids typically administered?
- when it’s difficult to administer sufficient volumes of fluids rapidly enough for resuscitation or to achieve the greatest cardiovascular benefit with the least volume of fluids
- large volume losses where crystalloids are not effectively improving or maintaining blood volume
- when increased tissue perfusion and O2 delivery is needed
- if edema develops, typically due to decreased oncotic pressure
- need for longer duration of effect
In what situation is hypertonic saline commonly used? When is it avoided?
hemorrhagic hypovolemic shock —> fast-acting, low-volume resuscitation
- hypernatremia
- severe dehydration
How is hypovolemia addressed during anesthetic fluids? How can fluid therapy be used in this situation?
- correct underlying disease, like CKD and heart disease
- decrease/stop fluids
- use diuretics
hypotonic (0.45%) NaCl for maintenance
When is hyperkalemia suspected? How are fluids used for treatment?
- urinary obstruction
- uroabdomen
- AKI
- DKA
- changes of echocardiogram
K-containing balanced electrolyte solutions - volume expansion + low K content in fluid compared to serum
What fluids are recommended for treating hypernatremia?
- replacement 0.9% saline (similar [Na] to serum)
- once volume is met, start hypotonic solutions
How are hypoproteinemic/hypoalbuminemic patients addressed?
- nutritional support
- plasma NOT often effective
- synthetic colloids maintain fluid in intravascular space
What are crystalloids?
fluids containing electrolytes and other solutes that can freely move between intra/extravascular fluid-containing spaces
What are colloids? What is the difference between natural and synthetic colloids?
fluids containing large molecules that are restricted and stay within the intravascular space longer than crystalloids
- NATURAL = blood, plasma, and albumin helpful to replacement of blood components —> potential for anaphylaxis!
- SYNTHETIC = starches, polysaccharides, gelatins —> coagulation defects, exacerbate renal disease, overload (cats!)
