Anesthesia - Fluid therapy

drraythe's version from 2016-04-13 21:34


Question Answer
How much of the body is water? What about neonates?Adults 60%
Difference btwn cats & dogs regarding the volume of their extracellular fluid?Cat 8%
Dogs 10%
(of total body)
*Extracellular compartment → the intravascular space is what % of the body fluids & what % of the BW? (on average)15% of body fluids & 9% of BW
Extracellular compartment → the interstitial space is what % of body fluids & what % of the BW? (on average)25% of body fluids & 15% of BW
**Intracellular space is what % of body fluids & what % of the BW? (on average)60% of fluids & 36% of BW
Main intracellular electrolyte?K+
Main plasma electrolyte?Na+
Main interstitial electrolyte?Na+
Which 3 electrolytes primarily determine the extracellular water content?Na, Cl, HCO3
Which 3 electrolytes mainly dominate the intracellular fluid compartment?Potassium
Rough guideline formula for how much fluid to replace in a deficit?(% dehydrated x BW(kg) / 100
The intracellular fluids differ from extracellular fluids mainly inThe ↑ K & ↓ Na levels
What is osmosis?Movement of water through semipermeable membranes
What is osmotic pressure?Pressure on 1 side of the membrane that prevents movement of water
Explain osmolarity vs osmolalityOsmoLARITY = (particles/l solution) which has to do w/ VOLUME
OsmoLALITY is (particles/kg H2O) which has to w/ WEIGHT (which is why she always says osmolaLity even tho we all learned osmolaRity...bc we are referring to the weight of the animal) (also you think the 1 w/ the L would be Liters but its not, its weight of course)
Explain what is going on w/ oncotic pressurePressure created by large molecules which cannot pass the membrane
**What is serum osmolality? What kinda __tonic is it?ISOTONIC – 300 mOsm/kg (270-350)
What is hydration? What is volemia?Hydration = state of extracellular volume (interstitial & intravascular space)
Volemia = refers to ONLY the intravascular volume
Assessment of hydration status → signs at: <5%?Not detectable
Assessment of hydration status → signs at: 5%?Dry MM (tachy)
Normal skin turgor
Assessment of hydration status → signs at: 6-7%?Dry MM (tacky)
mildly ↓ skin turgor
Assessment of hydration status → signs at: 10%?Eye sunken in orbits
Highyly ↓ skin turgor
Assessment of hydration status → signs at: 12-15%?Signs of shock
Death imminent
To determine what KIND of fluid has been lost in a PTx, what must you do?Look at LAB Parameters (is it crystalloid, colloid, or pure water loss?)
What are crystalloids?Solutions of small solutes (<200) such as electrolytes (Na,K,Cl, HCO3)
When are some situations where you'd use NaCl INSTEAD of LRS?Acute kidney failure
Postrenal uremia
(bc LRS is converted into Bicarb by the liver, so dont want a MORE basic solution, Addison’s = imbalance of Na,↓Na, so want Na & LRS has K+. Also in post-renal uremia also ↑ K & LRS has ↑ K & in acute kidney failure, cant excrete K, don't want MORE K from LRS)
When would you use colloids instead of LRS?Hypoproteinemia
Not responding to crystalloids
Max infusion rate of K+0.5 mmol/kg/hr OR 0.5 mEq/kg/hr (Conversion of mmol to mEq depends on the valency of the ion. Monovalent ions like K+ are 1 mmol:1mEq. Divalent Ions like Ca++ are 0.5 mmol:1 mEq)
If the fluid bag has 5mmol/L of K+ it has 5 mEq/L (ie. LRS)
Calculation for how much bicarb to give?Base excess x BW(kg) x 0.3
How do you lose crystalloids?Vomiting
Diuresis (pee)
How do you gain crystalloids?Gain fluids w/ Na concentrations near plasma
What are colloids? (Exs?)Solutions of large solutes (>20,000) such as albumin, dexTRANS, hetastarch
How do you lose colloids?Whole blood or plasma-rich fluid losses
How do you gain colloids?Dextran
*How much for how long of crystalloids stay in the blood stream after infusion? What problem can this lead to?Only 1/3-1/4 of volume infused is still present in the intravascular space after 1 hour-this can lead to edema
Which fluids shouldnt be used for shock fluid therapy? Why?Fluids w/ ↓ or no sodium...bc they're basically just water which then diffuses into the cells & doesnt help much w/ blood volume
Examples of free water/hypotonic fluid solutions?Free water
Dextrose in water solutions
Hypotonic saline solutions
2 uses for hypotonic crystalloid fluid solutions?Replace water deficit/losses, drug admin
How can you end up misusing hypotonic crystalloids?If you give large doses rapidly, you can cz water intoxication. Also you can cz cellular edema (free water/hypotonic tend to basically go right into the cells)
What "tonic" are the REPLACEMENT fluids?ISOTONICS
What are 3 examples of isotonic fluids?LRS (Na 130)
Saline (Na 154)
Plasmalyte 148 (Na 140)
Where do isotonic fluids tend to go?Into the interstitial (extracellular) space
Where do hypotonic fluids tend to go?Into the intracellular space
Which fluids do not tend to alter normal electrolyte values?Polyionic crystalloids (types of isotonic solutions)
Disadvantage → crystalloids are usually rapidly redistributed to the ___ compartment, meaning about only _________% is retained intravascularly. Bc of this you need to...Interstitial, only 25% retained intravascularly, which means you need to admin LARGE volumes
Crystalloids can cz what kinda edema? Give 3 examplesInterstitial edema, such as cerebral, pulmonary (esp cats) & systemic interstitial
What czs hemodilution? Describe it a littleCrystalloids can cz hemodilution. W/ will dilute RBCs, albumin & coagulation factors which can lead to bleeding
What are the 2 main crystalloid replacement solutions?LRS, 0.9% NaCl
LRS versus NaCl → what kinda __tonic? Is it balanced? Which is more commonly used? Any other disadvantages?BOTH are isotonic. NaCl is NOT balanced, LRS IS balanced bc it has mult. Electrolytes & also has lactate as a buffer (in the liver lactate is converted into bicarbonate). LRS is very commonly used bc of its buffering abilities. NaCl CAN cz a metabolic acidosis if overdosed
Will improper use of a crystalloid cz a metabolic acidosis or alkalosis?Acidosis (too much LRS can cz alkalosis tho)
**Normal replacement of normal ongoing losses, aka maintenance, RATE?2-3ml/kg/hr
**What is the rate for support of circulating blood volume during general anesthesia? (Maintenance)10ml/kg/hr (10 is the standard-can be 5 too, if the PTx has congestive heart failure, kidney problems, or there is risk of overhydration)
**What is the rate of fluid for moderate to severe hypovolemia (shock)?20-40-80ml/kg (NO TIME UNIT HERE BC YOU NEED TO GIVE IT NOW, RIGHT THE FUCK NOW)
Whos at big risk for pulmonary edema?Cats
Risk of fluid therapy pertaining to bloodHemodilution can lead to a coagulopathy
When might you want to give a little extra fluid during intraoperative fluid maintenance? (Also say normal rate & what ↑ rate would be)Normal intraoperative fluid maintenance rater would be 5-10ml/kg/hr. ↑er rate would be 20ml/kg/hr. You might want a ↑er rate if the PTx is mildly hypovolemic, hypotensive, dehydrated, has had mild hemorrhage
You must be extra careful giving fluids (use a ↓ rate) in what types of PTx?(1) PTxs w/ pulmonary edema or lung contusions
(2) Kidney failure
(3) Congestive heart failure
(4) Hypertensive or hypervolemic
(5) Brain edema
(6) Cardiac PTxs in general
In an isotonic crystalloid solution, what % of the infused solution is still present in the vessels after 30 minutes?25-30% (30 min only 30 percent...ISO hate when that happens)
Hypotonic solutions usually used for?Hypertonic dehydration, possibly cardiac PTxs (bc↓Na)
Isotonic saline solution is best used when?Correct hyponatremia or metabolic alkalemia
When are hypertonic solutions usually used?Hypovolemia, shock & cerebral edema
When are dextrose solutions usually used?When glucose substitution is necessary, such as in young animals, badly managed diabetic PTxs, or↓glucose levels due to other reasons
What are 3 synthetic colloids?HES (aka hydroxyethyl starch aka hetastarch)
What are 2 natural colloids? (& 2 "others" colloids)Natural: Plasma, Whole blood
Others: Oxyglobin, Human albumin
Are colloids homo or heterogeneous?Heterogeneous (all sorts of diff sized molecules)
What are the Hyperoncotic & iso-osmotic colloids? What is their osmolality?The 6% or 10% hetastarch, or the 6% dextran
Their osmolality (in saline) is 308
How much of synthetic colloids is retained in the intravascular space & for how long?60-80% retained intravascular, for SEVERAL DAYS (im gonna 68 some large molecules, bc 69ing them would just be too much!)
What is the needed volume like for a colloid versus a crystalloid?60-80% of colloids are retained, which means they need a much smaller resuscitation volume (crystalloids only 1/3-1/4 volume retained after 1hr)
3 main indications for using colloids?(1) Shock/hypotension
(2) Protein loss, eg ↑ vascular permeability (sepsis), loss via GIT or kidneys, exudate
(3) Hypoproteinemia/edema
What are 2 major disadvantages to synthetic colloids?(1) Interstitial deficits are usually not corrected (meaning they are not suitable in case of pure loss of crystalloid)
(2) Dilution of coag factors possible → bleeding tendency
HES is aka? What does it do to the oncotic pressure? How long can you give it & through what route?Hydroxyethylstarch, aka hetastarch. It is used to ↑ the oncotic pressure & can be given up to 24hr intravenously (I did the HES program for 1 day w/ results! - TV commercial)
Why do you want to give hetastarch w/ crystalloids?Acts so fast due to oncotic pressure it can cz dehydration (if not given w/ crystalloid) or they can irritate the BVs
**If you want to bolus hetastarch, you give how much over what amount of time?5-10ml/kg over 10-15 minutes
How much hetastarch would you give in a CRI to replace or maintain oncotic pressure?CRI of 1-2ml/kg/hr (I only want 1 or 2 packets of starch if you're going to keep giving it to me, bc I dont use it that often)
*What is the max amount of hetastarch you can give in 1 day?Max 20ml/kg/day (5-10 trannies a day & 20 heteros a day)
What is "hyperhes" & what do you use it for? What is the MAX amount you can give & why?This is a combination of a hypertonic (7.5%) saline solution w/ hyperoncotic (6%) hetastarch (HES). This is helpful in shock (esp cats) bc it can treat both dehydration & & ↓ oncotic pressure at the same time. MAX DOSE is 5ml/kg bc any more can lead to hypernatremia (5 is hyper)
Dextran solution → what is a dextran? What is it used for? How does it affect oncotic pressure? What is the half-life like? What is a caution about using this?It is a polysaccharide which works as a plasma expander by increasing oncotic pressure. Its half-life is less than hetastarch's. **ANAPHYLACTIC RXN IS POSSIBLE!!!!!!** (I'm allergic to sugar-sweet Trans people)
What is the max amount of dextran solution you can give in a day?5-10ml/kg/day max (5-10 trannies a day is all I can handle, he said)
What are the natural colloids & what is their inherent risk?Plasma/whole blood-risk of a transfusion rxn.
What are 3 indications for natural colloids?(1) Anemia (indication for whole blood)
(2) Coagulation disorders (fresh frozen plasma or fresh whole blood)
(3) extreme hypoproteinemia (indication for plasma)
What is 25% human albumin used for & what risk is there?Colloid osmotic pressure support in critically ill PTx mostly w/o adverse effects-however there have been some immediate or delayed transfusion rxns in dogs
What is oxyglobin I? What is it used for? How long is the shelf life?It is purified polymerized bovine Hb, which can be used as a UNIVERSAL Hb DONOR TO ALL VET SPECIES(licensed for use in dogs in Europe) & no cross matching is necessary. It works as a colloidal solution w/ O2 carrying capacity which can be used if no blood products are available. It has a 3 YEAR shelf life at room temp!
Oxyglobin II → how quickly can you admin it? What is its half-life? What are the risks of using it?SLOW admin, w/ a half-life of 30-40 hours. There is a risk of CIRCULATORY OVERLOAD (esp in cats) & it can cz jaundice & hematuria.
What is oxyglobin II most often used for?IMHA (bc the RBCs are just gonna get destroyed anyway)
5 major disadvantages of colloids?(1) Doesnt replace INTERSTITAL deficits
(2) Not good replacement fluid for GI losses
(3) Hemodilution (dilute RBCs & coag factors)
(4) Rebreeding from damaged blood vessels
(5) Can cz coagulopathies (impaired factor VIII (8) & VwB factor activity, as well as ↓ platelet fxn)
What bad things happen if you give too much dextran solution?(Colloid) Allergic rxns, renal insufficiency & hemorrhage
Why are some reasons you'd totally want intraoperative fluid therapy?Maintain blood volume, CO & BP bc of anesthetics having negative inotropic & vasodilatory effects
When should fluid deficits be corrected?PREOPERATIVELY IF AT ALL POSSIBLE
**Whats the intraoperative fluid rate?5-10ml/kg/hr
**What is the intraoperative fluid rate if you are doing a laparotomy?20ml/kg/hr
**If there is hypotension/hemorrhage, what can you ↑ your intraoperative fluid rate to?Up to 20-60ml/kg/hr (start w/ 10 tho & see how it is)
**What is the intraoperative fluid rate you'd give for cardiac PTx, PTx w/ pulmonary edema, or hypertension?2-5ml/kg/hr
A large drip set will have _________ drops per mL of fluid10, 15 or 20
A small drip set will have _________ dops per mL of fluid60 drops/ml (Small, Sixty)
**What is the equation for drops/min?(BW(kg) x rate (ml/kg/hr) x infusion set calibration (drops/ml) ) / 60 (min/hr)
Ex for drops/min equation: 10kg dog w/ a planned infusion rate of 10ml/kg/hr & there is a set calibration of 15drops/min..... how many drops per minute, or drops per second?(10kg x 10ml/kg/hr x 15drops/ml) / 60 = 25 drops per minute OR 0.4 drops per 2nd which would better be said as about 1 drop every 2 seconds
Ex for drops/min equation: 500kg horse, infusion rate 10ml/kg/hr, set 10 drops/min... How many drops a sec?(500kg x 10ml/kg/hr x 10drops/min) / 60 = 13.8 (roughly 14) drops per second
**Explain how you'd go about giving a shock infusionStart w/ LRS, you can give up to 90ml/kg to effect! Do it in a bolus of 20ml/kg at a time & reassess after each bolus. ALSO you can give a colloid, 5ml/kg as a bolus repeated up to a max of 20ml/kg a DAY

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