Fluid Therapy: Crystalloids - DONE

how much of the body is made of water and what proportion is inside the cells?

body: 60%

intracellular fluid: 40% of BW (fluid within cells)

extracellular fluid: 20% BW

-->incravascular and extravascular

what is intravascular fluid?

fluid within blood vessles (5% BW)

what is intersitial fluid?

fluid around cells and outside blood vessels (15%BW)

what is the breakdown of fluid comparments?

intracellular: 2/3

extracellular: 1/3

-->intravasculae (1/5) :plasma

-->extravascular (4/5): interisitial

compared ot the extracellular fluid, what is the Na and K content within cells?

Na lower in cells than extracellular fluid

-->extra: 145

-->intra: 12

K higher in cells than extracellular fluid

-->extra: 4

-->intra: 140

what are the fluid characterisitics regarding electrolytes?

INTRACELLUALR

-low sodium

-high potassium

EXTRACELLULAR

-high sodium

-low potassium

water follows sodium

sodium concentration determines IV volume

total body Na determines hydraton

what are some methods used to calculate daily water requirments?

calculation based on daily resting energy requirement equuations

70*BW^0.75 = mL/kg/24hours

OR

[30*BW]+70 = mL/kg/24hours

you have to divide by kg once you get your answer

30 mL/kg/day for giant breed dogs

40 mL/kg/day for large breed dogs

50 mL/kg/day for medium dogs and cats

60 mL/kg/day for small dogs

80-100mL/kg/day for neonates

what is the difference between dehydration and hypovolemia?

DEHYDRATION

-intersitial/intracellular fluid loss

-usually occurs slowly over several days to weeks

-can be replaced slowyl

HYPOVOLEMIA

-intravascular fluid loss

-usually occurs more rapidly than with dehydration

-requires rapid restoration of blood volume

NOT THE SAME THINGS

-->with sevre dehydration, you can become hypovolemic

what are the general types of fluid loss?

SENSIBLE

-urine (urinary output)

-feces

-vomitus

-wound exudates

INSENSIBLE (20-30 mL/kg/day)

-sweat

-saliva

-excessive panting

what is dehydration?

seen when fluid loss exceeds fluid intake

volume of fluid needed to replace the deficit is estimated by the equation:

BW(kg) * %dehydration = volume of fluid deficit (L)

what are the percent deydrations?

<5%: mild

-->no clinical signs

5-7%: moderate

-->mildly prolonged skin tent, MM normal or slightly tacky, CRT normal

8-10%: severe

>10%: critical dehydration

what does the rate at which dehydration deficit need to be replaced depend on?

heart disease

renal disease

what are the signs of hypovolemia?

requires rapid intervention: 5-10 min

tachycardia

prolonged CRT

hypotension

hypothermia, cool extremities

weak pulses

weakness, lethargy

what do we do for hypovolemia?

usually give fluid boluses of 10-20 mL/kg when using isotonic fluids and then reassess

goal directed therapy

what is crystalloid?

solutions containing electrolyte and nonelectrolyte solutes capable of entering all fluid compartments

what are the two major determinates of fluid balance within the body?

sodium and albumin

list three different characteristics used to describe a crytsalloid solution

toniciity

buffers

balanced vs unbalanced

what is toniciity?

tonicity is the effective osmolality of a solution

an effective osmole generates osmotic pressure by causing a shift of water across a semipermeable membrane

-->mannitol

-->Na

crystalloid solutions are often classifed based on their toniicity relatvie to taht of extracellular fluid

-->hypotonic

-->isotonic (270-350 mOsm/kg)

-->hypertonic

What are buffers?

excess Cl in some fluids have mild acidifying effect

anions such as acetate, gluconate, and lactate are added to crystalloids as a source of base

metabolism of these anions leads to production of bicarbonate

reports of hypotension during high volume high pressure bolus of acetste containing fluids (mostly in cats) such as normosol-R

lactate buffered solutions should be avoided in patients with end stage liver disease

what are balanced fluids?

a fluid is balanced if its composition resembles that of extracellular fluid

-->high Na, low K

balanced vs unbalanced

BALANCED

-major electrolytes are in similar porportion to extracellular fluid

-lactated ringers, normosol R, plasmalyte 48

UNBALANCED

-electrolytes are not in proportion with ECF

-normal saline (0.9% NaCl), 5% dextrose in water (D5W)

what would happen if you bolus water IV?

cellrupture

what is plain sterile water?

tonicity of 0

water should NEVER be administered IV

cause a rapid shifting of water intracellularly, causing RBC swelling and death

what are some examples of "maintenance" fluid?

half strength saline (0.45% NaCl)

normosol M

home-made concoctions (mixing replacement fluid with 5% dextrose to lower Na concentration)

plasmalyte 56

what are maintenance fluids?

maintenance fluids are used to replace the daily obligate lossess of water and solutes in Ps that are not e/d

most of this fluid loss occurs via kidneys and is low in Na, but relatvely higher in K (when compared to extracellular fluid)

additional fluid loss occurs from water and solute contained in feces, repsiration, and sweat

-->account for about 1/3 of maintenance water lost

-->relatively low in electrolytes

what is the composition of mainteance fluids?

lower in Na and Cl

-->Na ~50-70 mEq/L

higher in K

-->K ~ 10-20 mEq/L

tend to be hypotonic, but some have dextrose added to inc tonicity

what should oyu not do with maintenance fluids?

should NEVER be bolused

maintenance fluids are intended to be used at "maintenance rates"

rarely used in vet med

what are some examples of replacement fluids?

LRS

Normosol-R

0.9% saline

plasmalyte A or 148

what are replacement fluids?

most common type of fluid used in vet med

used to replace a fluid deficit from the intravascular or interisitial spaces

-->hypovolemia

-->dehydration

what is the compositon of replacement fluids?** on test**

similar to extracellular fluid

high in Na and Cl

-->Na: 130-154 mEq/L

-->Cl: 95-154 mEq/L

low in K: 0-5 mEq/L

tend to be isotonic (270-350 mOsm/L)

can replacement fluids be bolused?

may be bolused or administered at high flow rates

often used as "maintenance fluid" as kidneys will simply excrete the extra Na

examples of hypertonic fluids and potential use

7.5% saline

3% saline

20% mannitol

what are hypertonic fluids?

often used for rapid volume expansion or reduction of intracrania P

-->hemorrhagic/hypocvolemic shock

-->head trauma

mannitol may also be used for very specific situations

-->gluacoma

-->acute oliguric renal failure (no longer routinely rec)

what do hypertonic fluids do?

pull fluid from the intersitial space into the intravascular space and cause a rapid intravascular volume expansion

the effects are usually short-lived (15-20 min) and usually need to be followed by isotonic or maintenance fluids

what can hypertonic fluids cause?

may cause significant electrolyte abnormalities and/or dehydration

usually administered as IV bolusues (5-15 min)

what are the contraindications of hyperotnic fluids?

severe dehydration

hyperNa (some exceptiosn)

what is hypertonic saline?

usually 7.2-7.5% saline used for shock and head trauma

app. osmolality = 2400 mOsm/L

expand blood volume 3-3.5x the ammount administered

dose administered is 4mL/kg IV over 5 min (may be repeated once)

what are the proposed benefits of hypertonic saline?

rpaid intravascaulr volume expansion

dec cerebral edema

inc cardaic contractility

immunomodulatory effects

improved microcirulatory perfusion due to arteriolar vasodilation

what are the proposed adverse effects of hypertonic saline?

hyperNa

rapid administration (>1 mL/kg/min)

-->bradycardia

-->hypotension

-->brochoconstriction

what is mannitol?

mannitol 20% or 25%

approximate osmolality is 2000-2500 mOsm/L

must be kept warm to prevent crystallization

should be administered thru a filter

dose administered is 0.5 to 1.5 g/kg IV over 15 min (may be repeated)

what are the propsed benfits of mannitol?

dec cerebral edema

imprives rheology (dec blood visocisity)

free radical scavenger

what are the proposed adverse effects of mannitol?

may exacerdate edema or hemorrhage

dehydration

when are fluids no longer needed?

when rehydration is complete

-->based on estimated deficit, serial PE, appropriate inc in BW

when P is eating and drinkinhg sufficiently to maintain daily losses

-->a P that is e/d will drink when the fluids are stoppped

-->dogs and cats don't drink when they are not thirsty

when on-going losses are under control

-->no more vomiting, diarrhea is improved or minimal

2yo MN, 10 kg doxen. acute v/d. 2 episodes of emesis over last 4 hours. each vomitus was 2-3 tsp. each bout of diarrhea was one cup of watery brown d. PE: 5% dehydrated. what do you do?

STEP 1: calculate percent dehydration

0.05 *10kg = 0.5 kg = 0.5 L = 500 mL

-->correct over 12 hours (500/12 = 41 ml/hr)

STEP 2: maintenance requirements

-->RER = [30*10kg] +70 = 370 kcal/day or 370 mL/day

-->370/24 hours = 15.4 mL/hr

STEP 3: ongoing losses

-->v: 30 mL

-->d: 236 mL

-->total: 266mL / 12h = 22 mL/hour

add all: 80 ml/hr