FLUID Therapy

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FLUID Therapy

• Dan Belz, July 2008

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Fluid and electrolyte balance is an extremely
complicated thing.
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Importance

• Need to make a decision regarding fluids in
  pretty much every hospitalized patient.
• Can be life-saving in certain conditions
• loss of body water, whether acute or chronic, can
  cause a range of problems from mild
  lightheadedness to convulsions, coma, and in some
  cases, death.
• Though fluid therapy can be a lifesaver, it's
  never innocuous, and can be very harmful.

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Kinds of IV Fluid solutions

• Hypotonic - 1/2NS
• Isotonic - NS, LR, albumen
• Hypertonic Hypertonic saline.
• Crystalloid
• Colloid

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Crystalloid vs ColloidType of particles (large
or small)

• Fluids with small crystalizable particles like
  NaCl are called crystalloids
• Fluids with large particles like albumin are
  called colloids, these dont (quickly) fit
  through vascular pores, so they stay in the
  circulation and much smaller amounts can be used
  for same volume expansion. (250ml Albumin 4 L
  NS)
• Edema resulting from these also tends to stick
  around longer for same reason.
• Albumin can also trigger anaphylaxis.

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• There are two components to fluid therapy
• Maintenance therapy replaces normal ongoing
  losses, and
• Replacement therapy corrects any existing water
  and electrolyte deficits.

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Maintenance therapy

• Maintenance therapy is usually undertaken when
  the individual is not expected to eat or drink
  normally for a longer time (eg, perioperatively
  or on a ventilator).
• Big picture Most people are NPO for 12 hours
  each day.
• Patients who wont eat for one to two weeks
  should be considered for parenteral or
  enteralnutrition.

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• Maintenance Requirements can be broken
• into water and electrolyte requirements

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Water

• Two liters of water per day are generally
  sufficient for adults
• Most of this minimum intake is usually derived
  from the water contentof food and the water of
  oxidation, therefore
• it has been estimated that only 500ml of water
  needs be imbibed given normal diet and no
  increased losses.
• These sources of water are markedly reduced in
  patients who are not eating and so must be
  replaced by maintenance fluids.

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• water requirements increase with fever,
  sweating, burns, tachypnea, surgical drains,
  polyuria, or ongoing significant
  gastrointestinal losses.
• For example, water requirements increase by 100
  to 150 mL/day for each C degree of body
  temperature elevation.

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Several formulas can be used to calculate
maintenance fluid rates.
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• A comparison of formulas produces a widevariety
  of fluid recommendations
• 2000 cc to 3378 cc for an obese woman who is65
  inches tall and weighs 248 pounds (112.6 kg)
• This is a reminder that fluid needs, no matter
  what formula is used, are at best an estimation.

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4/2/1 rule a.k.a Weight40

• I prefer the 4/2/1 rule (with a 120 mL/h limit)
  because it is the same as for pediatrics.

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• 4/2/1 rule4 ml/kg/hr for first 10 kg
  (40ml/hr)then 2 ml/kg/hr for next 10 kg
  (20ml/hr)then 1 ml/kg/hr for any kgs over
  thatThis always gives 60ml/hr for first 20
  kgthen you add 1 ml/kg/hr for each kg over 20
  kg
• This boils down to Weight in kg 40
  Maintenance IV rate/hour.For any person weighing
  more than 20kg

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Maintenance IV rate4/2/1 rule -gt Weight in kg
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What to put in the fluids

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Start D5 1/2NS20 meq K _at_ Wt40/hr

• a reasonable approach is to start 1/2 normal
  saline to which 20 meq of potassium chloride is
  added per liter. (1/2NS20 K _at_ Wt40/hr)
• Glucose in the form of dextrose (D5) can be added
  to provide some calories while the patient is
  NPO.
• The normal kidney can maintain sodium and
  potassium balance over a wide range of intakes.
• So,start
• D5 1/2NS20 meq K
• at a rate equal to their weight 40ml/hr, but
  no greater than 120ml/hr.
• then adjust as needed, see next page.

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Start D5 1/2NS20 meq K, then adjust

• If sodium falls, increase the concentration (eg,
  to NS)
• If sodium rises, decrease the concentration (eg,
  1/4NS)
• If the plasma potassium starts to fall, add more
  potassium.
• If things are good, leave things alone.

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Usually kidneys regulate well, butAltered
homeostasis in the hospital

• In the hospital, stress, pain, surgery can alter
  the normal mechanisms.
• Increased aldosterone, Increased ADH
• They generally make patients retain more water
  and salt, increase tendency for edema, and become
  hypokalemic.

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• Now onto Part 2 of the presentation

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Hypovolemia

• Hypovolemia or FVD is result of water
  electrolyte loss
• Compensatory mechanisms include
  Increased sympathetic nervous system stimulation
  with an increase in heart rate cardiac
  contraction thirst plus release of ADH
  aldosterone
• Severe case may result in hypovolemic shock or
  prolonged case may cause renal failure

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Causes of FVDhypovolemia

• Gastrointestinal losses N/V/D
• Renal losses diuretics
• Skin or respiratory losses burns
• Third-spacing intestinal obstruction,
  pancreatitis

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Replacement therapy.
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• A variety of disorders lead to fluid losses that
  deplete the extracellular fluid .
• This can lead to a potentially fatal decrease in
  tissue perfusion.
• Fortunately, early diagnosis and treatment can
  restore normovolemia in almost all cases.

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• There is no easy formula for assessing the degree
  of hypovolemia.
• Hypovolemic Shock, the most severe form of
  hypolemia, is characterized by tachycardia, cold,
  clammy extremities, cyanosis, a low urine output
  (usually less than 15 mL/h), and agitation and
  confusion due to reduced cerebral blood flow.
• This needs rapid treatment with isotonic fluid
  boluses (1-2L NS), and assessment and treatment
  of the underlying cause.
• But hypovolemia that is less severe and therefore
  well compensated is more difficult to accurately
  assess.

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History for assessing hypovolemia

• The history can help to determine the presence
  and etiology of volume depletion.
• Weight loss!
• Early complaints include lassitude, easy
  fatiguability, thirst, muscle cramps, and
  postural dizziness.
• More severe fluid loss can lead to abdominal
  pain, chest pain, or lethargy and confusion due
  to ischemia of the mesenteric, coronary, or
  cerebral vascular beds, respectively.
• Nausea and malaise are the earliest findings of
  hyponatremia, and may be seen when the plasma
  sodium concentration falls below 125 to 130
  meq/L. This may be followed by headache,
  lethargy, and obtundation
• Muscle weakness due to hypokalemia or
  hyperkalemia
• Polyuria and polydipsia due to hyperglycemia or
  severe hypokalemia
• Lethargy, confusion, seizures, and coma due to
  hyponatremia, hypernatremia, or hyperglycemia

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Basic signs of hypovolemia

• Urine output, less than 30ml/hr
• Decreased BP, Increase pulse

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Physical exam for assessing volume

• physical exam in general is not sensitive or
  specific
• acute weight loss however, obtaining an accurate
  weight over time may be difficult
• decreased skin turgor - if you pinch it it stays
  put
• dry skin, particularly axilla
• dry mucus membranes
• low arterial blood pressure (or relative to
  patient's usual BP)
• orthostatic hypotension can occur with
  significant hypovolemia but it is also common in
  euvolemic elderly subjects.
• decreased intensity of both the Korotkoff sounds
  (when the blood pressure is being measured with a
  sphygmomanometer) and the radial pulse
  ("thready") due to peripheral vasoconstriction.
• decreased Jugular Venous Pressure
• The normal venous pressure is 1 to 8 cmH2O, thus,
  a low value alone may be normal and does not
  establish the diagnosis of hypovolemia.

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SIGNS SYMPTOMS OF Fluid Volume Excess

• SOB orthopnea
• Edema weight gain
• Distended neck veins tachycardia
• Increased blood pressure
• Crackles wheezes
• pleural effusion

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For the EBM aficionados out there.

• A JAMA 1999 systematic review of physical
  diagnosis of hypovolemia in adults
• CONCLUSIONS A large postural pulse change (gt or
  30 beats/min) or severe postural dizziness is
  required to clinically diagnose hypovolemia due
  to blood loss, although these findings are often
  absent after moderate amounts of blood loss. In
  patients with vomiting, diarrhea, or decreased
  oral intake, few findings have proven utility,
  and clinicians should measure serum electrolytes,
  serum blood urea nitrogen, and creatinine levels
  when diagnostic certainty is required.

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Which brings us to Labnormalities seen with
hypovolemia

• a variety of changes in urine and blood often
  accompany extracellular volume depletion.
• In addition to confirming the presence of volume
  depletion, these changes may provide important
  clues to the etiology.

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BUN/Cr

• BUN/Cr ratio normally around 10
• Increase above 20 suggestive of prerenal state
• (rise in BUN without rise in Cr called prerenal
  azotemia.)
• This happens because with a low pressure head
  proximal to kidney, because urea (BUN) is
  resorbed somewhat, and creatinine is secreted
  somewhat as well

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Hgb/Hct

• Acute loss of EC fluid volume causes
  hemoconcentration (if not due to blood loss)
• Acute gain of fluid will cause hemodilution of
  about 1g of hemoglobin (this happens very often.)

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Plasma Na

• Decrease in Intravascular volume leads to greater
  avidity for Na (through aldosterone) AND water
  (through ADH),
• So overall, Plasma Na concentration tends to
  decrease from 140 when hypovolemia present.

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Urine Na

• Urine Na goes down in prerenal states as body
  tries to hold onto water.
• Getting a FENa helps correct for urine
  concentration.
• Screwed up by lasix.
• Calculator on PDA or medcalc.com

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IV Modes of administration

• Peripheral IV
• PICC
• Central Line
• Intraosseous

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IV ProblemExtravasation / Infiltrated

• The most sensitive indicator of extravasated
  fluid or "infiltration" is to transilluminate the
  skin with a small penlight and look for the
  enhanced halo of light diffusion in the fluid
  filled area.
• Checking flow of infusion does not tell you where
  the fluid is going

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• Thats it folks.