FLUID AND ELECTROLYTE
BALANCE IS AN EXTREMELY
• 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
• Though fluid therapy can be a lifesaver, it's never
innocuous, and can be very harmful.
CRYSTALLOID VS COLLOID
TYPE OF PARTICLES (LARGE OR
• Fluids with small “crystalizable” particles like NaCl are
• Fluids with large particles like albumin are called colloids,
these don’t (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.
THERE ARE TWO COMPONENTS TO FLUID THERAPY:
• MAINTENANCE THERAPY REPLACES NORMAL
ONGOING LOSSES, AND
• REPLACEMENT THERAPY CORRECTS ANY
EXISTING WATER AND ELECTROLYTE DEFICITS.
• 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 won’t eat for one to two weeks should be
considered for parenteral or enteral
MAINTENANCE REQUIREMENTS CAN BE
INTO WATER AND ELECTROLYTE
• Two liters of water per day are generally sufficient for
• Most of this minimum intake is usually derived from the
of 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
• 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.
SEVERAL FORMULAS CAN BE USED TO CALCULATE
MAINTENANCE FLUID RATES.
• A comparison of formulas produces a wide
variety of fluid recommendations:
• 2000 cc to 3378 cc for an obese woman who is
65 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.
4/2/1 RULE A.K.A WEIGHT+40
• I PREFER THE 4/2/1 RULE (WITH A 120 ML/H LIMIT)
BECAUSE IT IS THE SAME AS FOR PEDIATRICS.
• 4/2/1 rule
4 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 that
this always gives 60ml/hr for first 20 kg
then you add 1 ml/kg/hr for each kg over 20 kg
this boils down to: weight in kg + 40 = maintenance IV
For any person weighing more than 20kg
MAINTENANCE IV RATE:
4/2/1 RULE -> WEIGHT IN KG +
START: D5 1/2NS+20 MEQ K @
• A reasonable approach is to start 1/2 normal saline to which 20 meq of
potassium chloride is added per liter.
(1/2NS+20 K @ wt+40/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.
d5 1/2ns+20 meq k
at a rate equal to their weight + 40ml/hr, but no greater than 120ml/hr.
• Then adjust as needed, see next page.
START D5 1/2NS+20 MEQ K, THEN
• IF SODIUM FALLS, INCREASE THE CONCENTRATION (EG, TO
• IF SODIUM RISES, DECREASE THE CONCENTRATION (EG,
• IF THE PLASMA POTASSIUM STARTS TO FALL, ADD MORE
• IF THINGS ARE GOOD, LEAVE THINGS ALONE.
USUALLY KIDNEYS REGULATE
ALTERED HOMEOSTASIS IN THE
• 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.
• 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 &
• Severe case may result in hypovolemic shock or prolonged
case may cause renal failure
• A variety of disorders lead to fluid losses that deplete the
extracellular fluid .
• This can lead to a potentially fatal decrease in tissue
• Fortunately, early diagnosis and treatment can restore
normovolemia in almost all cases.
• There is no easy formula for assessing the degree of
• 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.
HISTORY FOR ASSESSING
• The history can help to determine the presence and etiology of volume
• 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
BASIC SIGNS OF HYPOVOLEMIA
• URINE OUTPUT, LESS THAN 30ML/HR
• DECREASED BP, INCREASE PULSE
• Physical exam in general is not sensitive or specific
• Acute weight loss; however, obtaining an accurate weight over time may
• 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.
WHICH BRINGS US TO:
LABNORMALITIES SEEN WITH
• 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.
• BUN/cr ratio normally around 10
• Increase above 20 suggestive of “prerenal state”
• (rise in BUN without rise in cr called “prerenal
• This happens because with a low pressure head
proximal to kidney, because urea (bun) is resorbed
somewhat, and creatinine is secreted somewhat as well
• 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.)
• 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.
• Urine na – goes down in prerenal states as body tries to hold
• Getting a fena helps correct for urine concentration.
• Screwed up by lasix.
• Calculator on pda or medcalc.Com
IV MODES OF ADMINISTRATION
• PERIPHERAL IV
• CENTRAL LINE
• 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
• CHECKING FLOW OF INFUSION DOES NOT TELL YOU
WHERE THE FLUID IS GOING