question

Intravenous Fluids

answer

Total body water 1) Intracellular Fluid (2/3 of TBW) 2) Extracellular Fluid (1/3 of TBW) *Interstitial Fluid (2/3 of ECF) *Intravascular Fluid (1/3 of ECF)

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Total Body Water (TBW) constitutes ____ of lean body weight in healthy adult females and ____ of lean body weight in adult males

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females=50% males=60%

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in a 70 kg male, TBW= in a 70 kg female, TBW=

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male= 42L female=35L

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TBW in newborns

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constitutes about 75-85% of body weight for newborns

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TBW is made up of:

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2/3 is ICF 1/3 is ECF

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Intracellular Fluid (ICF)

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-makes up 2/3 of TBW -represents water inside the body cells

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ICF is rich in:

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K+ Mg2+ phosphate protein

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Extracellular Fluid (ECF)

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-makes up 1/3 TBW -water outside the cells; it is divided between two subcompartments: 1) interstitial fluid and the 2) intravascular fluid -compared with total body dehydration, intravascular depletion tends to occur ACUTELY and requires rapid and aggressive replacement (fluid resuscitation)

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ECF is rich in:

answer

Na+ Cl bicarbonate

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Interstitial fluid

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-around the cells of our tissues (fluid occupying space between cells) -makes up about 2/3 of ECF

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Intravascular fluid

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-fluid occupying the vasculature -makes up about 1/3 of ECF

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Fluid Management Strategies: Maintenance Therapy: when do you give it?

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-used during times of limited or no oral intake to prevent fluid and electrolyte imbalance and to provide a min amount of nutrition (sugar) -such times may include during short periods of bowel rest, before and after surgery, when pts are acutely ill and unable or unwilling to eat

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The goal:

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provide an IVF that will replenish all body fluid stores, ICF and ECF -often 5% dextrose and potassium are added to solutions containing sodium to provide a small amount of calories and electrolytes

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Maintenance therapy can be accomplished with:

answer

most any crystalloid -D5%/0.45%saline with 20meq KCl/L commonly used**** -monitor ins and outs, signs of edema, signs of hypovolemia, Na+ and K+ and adjust accordingly

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Adult rates=

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75-125 ml/hr or somewhere around 2 liters per day

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Rate exceptions

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if the pt is sicker or fluid loss= can be more aggressive with rate -if heart or renal failure = less aggressive

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Replacement Therapy is used when?

answer

During acute situations involving dehydration/hypovolemia -hypovolemic shock (from any cause: sepsis, anaphylaxis,etc): where acute resuscitation is needed to keep organs perfused and to prevent/treat CV collapse; -severe blood loss requiring blood volume expansion; -hypotension to maintain normal BP; - dehdyration including DKA and other causes

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****symptoms of intravascular hypovolemia:

answer

can range from mild- to life threatening if hemodynamically unstable -dizzy -decreased tissue perfusion -orthostasis -tachycardia -low central venous pressure -decreased urine output -hypovolemic shock

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treatment

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must include attempting to correct the underlying cause, normalize capillary permeability and replace lost intravascular fluid with a solution of a similar composition

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If hemodynamically unstable, what should you do first?

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-replace the vasculature fluid first (fluid resuscitation or volume expansion) -using a fluid that mostly stays within the ECF and vasculature

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What fluid would you use? (the IVF of choice for most cases of acute fluid resuscitation??

answer

1) Crystalloids=effective, cheap and most commonly used -0.9% saline is the IVF of choice for most cases of acute fluid resuscitation -NS has a better compatibility with meds, -isotonic-hypernatremia risk

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What is another choice of fluid?

answer

Lactated ringers: also works, but prolonged infusions are associated with lactic acidosis -LR may be preferred in pts with elevated sodium**** -isotonic, Na, Ca, K, Cl, lactate; more similar to blood but not much difference between NS -LR might be used more in trauma, surgery, burns, OB

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Fluid resuscitation rates:

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-are high and depend upon the severity of the situation (250-1000 ml/hr or "wide open") -rate also depends upon product, body size, CV stability, age, renal status, CO, fluid overload risk

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What fluids are generally reserved for more severe cases or special situations?

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Colloids: highly effective, but very expensive

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Crystalloids:

answer

-is a general term for a solution that contains electrolytes or small molecular substances: such as Na+, Cl-, K+ and dextrose -crystalloids pass freely through semi-permeable membranes -fill intravascular space and all components of body -used for mild dehydration and maintainable; NS and LR stay in vasculature longer than other crystalloids= so we use these for fluid resuscitation

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Crystalloids can be further classified according to their:

answer

tonicity and sodium content -they come premixed with or without dextrose and potassium

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Isotonic solutions

answer

have a tonicity equal to that of the ICF and do not cause shifts in water distribution between the ECF and ICF -NS and LR are particularly effective for fluid resuscitation (when dextrose is added to NS or LR it is ineffective for FR)

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If you add dextrose to NS or LR

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it will cause it to move out of vasculature faster so it is not as effective; use plain NS and LR

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Maintenance therapy may require:

answer

prolonged infusions -prolonged infusions of NS may increase risk of hypernatremia -prolonged LR increases risk of lactic acidosis -prolonged 0.3% or 0.2% saline increases risk of HYPOnatremia

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Colloids

answer

-a general term for a solution containing plasma proteins or other large molecular weight substances -they do not readily cross semipermeable membranes -they effectively shift fluid from the interstitial compartment to the intravascular compartment (at least short-term until the colloid particles are metabolized) -they stay inside vasculature longer than NS and LRs -also: you only have to give half to 1/3 the volume; ideal for situations where pt is highly likely to be fluid overloaded: main advantage -expensive

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1) Albumin 5% in normal saline

answer

-albumin solutions contain human proteins so are very expensive and cost more than other colloids -albumin solution should not be used as a nutritional source of proteins and should not be used for FR/volume expansion -never use to treat malnourishment

question

25% albumin solution

answer

comes in vials and is administered periodically like a med -25% albumin + furosemide administration may improve fluid balance, oxygenation, and hemodynamics in pts with acute lung injury with low serum protein (used to pull fluid outside the vasculature into the vasculature)

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2) Hetastarch (Hespan) and other brand names

answer

-contains 6% hetastarch (a starch) and 0.9% saline -not a blood derived product; about half the cost of albumin but still much more expensive than crystalloids -primarily used as a plasma expander*******

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ADRs

answer

anaphylaxis and prolonged bleeding time

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Which fluid do you choose?

answer

-maintenance? -rehydration? -volume expansion/resuscitation?

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What is the pt status?

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-baseline labs -electrolyte abnormalities -renal function, DM, CHF, frail, elderly

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Lactated Ringers (LR)

answer

-isotonic -electrolytes approx blood make-up -clinical uses similar to 0.9% NS -lactate component can increase risk of lactic acidosis in liver failure

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0.9% Saline (NS: normal saline) 0.9 grams/100 ml or 9 grams/L

answer

-isotonic -similar to body fluids -perioperative fluid -volume resuscitation -ECF volume replacement

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0.45% Saline

answer

-hypotonic (1/2 NS), but not damaging to RBCs -source of free water -typical maintenance fluid

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0.33% Saline

answer

(1/3 NS) -hypotonic

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0.2% Saline (1/4 NS)

answer

-VERY hypotonic -potential to cause RBC hemolysis

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10% Dextrose in water

answer

100 gm/L of glucose (10 g/100ml) -used to treat/prevent hypoglycemia (maybe overdose of insulin; struggling to keep blood sugar up)

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5% Dextrose in Water (D5W)

answer

50 gm/L of Glucose -source of free water -small infusions of medications -used to "keep vein open"

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5% Dextrose/ Lactated Ringers (D5W/LR)

answer

50 gm/L glucose -isotonic

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5% Dextrose/0.9% Saline (D5W/0.9% saline or D5W/NS)

answer

50 gm/L glucose -isotonic

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5% Dextrose/0.45% Saline (D5W/1/2NS)

answer

50 gm/L glucose -acts as hypotonic solution -source of free water -typical maintenance fluid

question

5% Dextrose/0.33% Saline (D5W/1/3NS)

answer

50 gm/L -hypotonic

question

Do 5% dextrose solutions affect blood sugar in non-diabetics?

answer

they do not cause hyperglycemia in non-diabetics -only continuous infusions are a concern in DM -small D5W infusions used for med administration in diabetics are usually OK

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Free water=

answer

meaning that approx 2/3 of the fluid administered will distribute into ICF and 1/3 will distribute into ECF (ECF distribution is divided between interstitial and intravascular)

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Do Isotonic NS solutions have a risk of causing hypernatremia?

answer

yes

question

Lactated ringers also contain what?

answer

28 meq lactate; 4 meq K+, 3 meq Ca2+

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Do hypotonic saline solutions have the risk of causing what?

answer

hyponatremia

question

what is the most common amount of potassium to add to 1 L bag?

answer

20 mg

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Other common hydration/replacement solutions with Potassium=

answer

most of the previously listed IV fluids are also available in pre-mixed solutions with various amounts of potassium -these can also be used as regular hydration/replacement solutions to simply help meet daily K+ requirements -most commonly the solutions contain 10 meq, 20 meq, or 40 mew KCl per liter

question

Examples of how to write this:

answer

-NS w/20 KCl = 0.9% saline/20 meq KCl per liter -D5NS w/10 KCl= Dextrose 5%/Saline 0.9%/10 meq KCl per liter -1/2 NS w/40 KCl= 0.45% saline/40 meq KCl per liter -D5 1/2 NS w/20KCl= dextrose 5%/ saline 0.45%/ 20 meq KCl per liter

question

Prolonged LR

answer

lactic acidosis

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Prolonged NS

answer

hypernatremia

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Prolonged 0.3% NS

answer

hyponatremia

question

Prolonged 0.2% NS

answer

hyponatremia, hemolysis -wouldnt be used for maintenance therapy unless pt already has high sodium for some reason

question

RBCs in different solutions

answer

-when in isotonic solution they are fine -when they come in contact with hypotonic solution= hemolysis occurs: the water tries to shift from the vasculature inside the RBCs in order to equalize salt concentration between vasculature and whats in RBCs

question

When can crenation occur?

answer

when RBCs are exposed to hypertonic solutions like 3% saline; the fluid wants to move out of RBCs into vasculature, RBCs shrivel up

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Maintenance IVF rate

answer

-adult= 75-125 ml/hr -2 L/day -23-35 ml/kg/day

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For children rate is always: Pediatric Maintenance fluid rate:

answer

weight based

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Replacement using Crystalloid IVR rate

answer

acute situations -monitor BP, HR, vital signs, lab work ordered frequently -short term; reassess frequently -250-1000 ml/hr depending on situation/pt or -wide open

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1 liter of D5W

answer

5% dextrose solution = considered free water; should distribute equally between all water components of body -expect 2/3 in extracellular (660 ml) and 1/3 in intracellular (330 ml) -2/3 into interstitial (220 ml) -1/3 into intravascular (110 ml)

question

1 L of NS solution

answer

0.9% saline= remains mostly in the extracellular space -2/3 into interstitial space (660 ml) -1/3 into intravascular (330 ml) THREE TIMES AS MUCH HERE

question

with a colloid solution what should you expect?

answer

expect almost whole liter staying in the intravascular space with very little leaving

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