FLUID THERAPY

NIKHIL NANJAPPA B A

FLUID AND ELECTROLYTE BALANCE IS AN EXTREMELY

COMPLICATED THING.

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.

KINDS OF IV FLUID SOLUTIONS

• HYPOTONIC - 1/2NS

• ISOTONIC - NS, LR, ALBUMEN

• HYPERTONIC – HYPERTONIC SALINE.

• CRYSTALLOID

• COLLOID

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 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

• 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 enteralnutrition.

MAINTENANCE REQUIREMENTS CAN BE

BROKEN

INTO WATER AND ELECTROLYTE

REQUIREMENTS:

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.

• 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 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 that

this 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

MAINTENANCE IV RATE:4/2/1 RULE -> WEIGHT IN KG +

40

WHAT TO PUT IN THE FLUIDS

•

START: D5 1/2NS+20 MEQ K @ WT+40/HR

• 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.

• So,start:

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 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.

USUALLY KIDNEYS REGULATE WELL, BUT:

ALTERED 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.

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

CAUSES OF FVD=HYPOVOLEMIA:

• GASTROINTESTINAL LOSSES: N/V/D

• RENAL LOSSES: DIURETICS

• SKIN OR RESPIRATORY LOSSES: BURNS

• THIRD-SPACING: INTESTINAL OBSTRUCTION, PANCREATITIS

REPLACEMENT THERAPY.

• 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.

• 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.

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

BASIC SIGNS OF HYPOVOLEMIA

• URINE OUTPUT, LESS THAN 30ML/HR

• DECREASED BP, INCREASE PULSE

PHYSICAL EXAM• 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.

SIGNS & SYMPTOMS OF FLUID VOLUME EXCESS

• ORTHOPNEA

• EDEMA & WEIGHT GAIN

• DISTENDED NECK VEINS & TACHYCARDIA

• INCREASED BLOOD PRESSURE

• CRACKLES & WHEEZES

• PLEURAL EFFUSION

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.

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

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.)

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.

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

IV MODES OF ADMINISTRATION

• PERIPHERAL IV

• PICC

• CENTRAL LINE

• INTRAOSSEOUS

IV PROBLEM:EXTRAVASATION / “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