Fluid Therapy

Question 1

Special Features of Water

Answer 1

Polarity = responsible for many of chemical, physical properties

High surface tension, high specific heat, high heat of
vaporization, low vapor pressure, high boiling point

Water ionizes in nature, substances dissolved in water segregate into individual components

Also exists as a negatively charged hydroxyl ion (OH-), positively charged protonated ion (H3O+)

Question 2

How much water in adult animal?

Answer 2

60%

Question 3

How much water in neonate?

Answer 3

80%

Question 4

Separation of ECF, ICF

Answer 4

separated by cell membranes

Freely permeable to water with use of carrier proteins, active
transport, passive transfusion

Governed by osmotic gradient

Question 5

Separation of ISF, IVF

Answer 5

Endothelium

Freely permeable to water, various ionic solutes

Question 6

Major cation in ECF

Answer 6

Na, 142mEq/L (plasma)

Question 7

Major anion in ECF

Answer 7

Cl, 104mEq/L; HCO3 24mEq/L (plasma)

Question 8

Major cation in ICF

Answer 8

K 140, Mg 34mEq/L (intracellular)

Question 9

Major anions in ICF

Answer 9

OPs (40), proteins (50)

Question 10

Osmolality

Answer 10

Determined btw different solute pressures

Solutes that cannot cross cell membrane contribute to effective osmolality = effective osmoses

Depends on NUMBER of particles in solution

Question 10

Osmolality

Answer 10

Determined btw different solute pressures

Solutes that cannot cross cell membrane contribute to effective osmolality = effective osmoses

Question 11

Ineffective Osmoses

Answer 11

Solutes that can readily diffuse across cell membrane, do not contribute to fluid shifts

In equilibrium on both sides of semi-permeable membrane

Question 12

Osmolality of plasma, ISF

Answer 12

-Ions: K, Na, Cl, HCO3, glucose, urea
-Larger molecules (eg albumin) = important component in colloid oncotic pressure, contribute to little osmolality

Question 13

ECF Osmolality

Answer 13

Mainly governed by Na, also glucose

Question 14

Plasma Osmolality

Answer 14

Plasma osmolality (mOsm/kg)= 2 [(Na+) + (K+)] + [(Glucose)/18] + ([BUN] /2.8)

Normal = 300mOsm/L

Question 15

Extracellular loss of Free Water

Answer 15

concentration of ECF concentrates increases causing osmotic pull (osmosis) of water through cell membrane to ECF

Question 16

Movement of Fluid btw IVS, ISF

Answer 16

Occurs at level of capillaries, Starling’s Equation

Question 17

Endothelial glycocalyx

Answer 17

glycocalyx model of transvascular fluid exchange and modification of starling’s equation

Filtration properties of capillary wall reside in endothelial glycocalyx layer (EGL)

Matrix covers the intracellular clefts

Glycocalyx COP replaces oncotic pressure of interstitum

Question 18

Crystalloids

Answer 18

Classified based on tonicity relative to plasma

Question 19

Isotonic crystalloids

Answer 19

Similar tonicity/osmolality vs plasma

Stay within ECF, no alteration in ICF volume
Fluids in ECF redistribute to IVF, ISF

Shock patients: up to one blood volume, start with 1/4-1/3 dose

Question 20

LRS

Answer 20

–Racemic mixture of L and D lactate or just L lactate
–Ca ions: not recommended with blood products, may antagonize common anticoagulants -> production of micro emboli

Question 21

Acetate Containing Solutions

Answer 21

–Maybe have more profound alkalinizing effect
–Large quantities (Norm R, Plasmalyte) rapidly bolused: VD DT release of adenosine from muscles = hypertension, esp in hypovolemic patients

Question 22

Hypertonic Crystaloids

Answer 22

–Increased tonicity, osmolality vs plasma
–Increased osmotic pressure in IVF –> pulls water from ISF, ICF (ICF > ISF) –> immediate plasma expansion
–Follow with crystalloids
–Most common: 7.5% HSS

Question 23

Components of 0.9% NaCl

Answer 23

154 Na, 154 Cl - hypertonic to plasma

Question 24

LRS

Answer 24

Na 130
Cl 109
K 4
Ca 3
272mOsm/L

Question 25

Plasmalyte

Answer 25

Na 148
Cl 98
K 5
Mg 3
294 mOsm/L - about isotonic to plasma

Question 26

HSS

Answer 26

–Contraindicated with preexisting dehydration
–Effects can be prolonged with a colloid
–Cardiac arrhythmias, bradycardia, hypotension
–Dosing: 4-6mL/kg no faster than 1mL/kg/min

Question 27

HSS Potential Clinopathologic Changes

Answer 27

hypernatremia, hypochloremic metabolic acidosis,
hyperosmolar renal failure, and hypokalemia

Question 28

What equilibrium is responsible for maintaining slightly different concentrations of anions, cations in ICF vs ECF?

Answer 28

Gibbs Donnan Equilibrium

Question 29

Filtration under normal conditions

Answer 29

Net filtration pressure responsible for movement out of capillaries into interstitum

Some of fluid normally returned to circulation via lymphatic system