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FLUIDS AND ELECTROLYTES

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					  FLUIDS AND
ELECTROLYTES
Terms to KNOW
• Total Body Water (TBW)
• Intracellular fluid
• Extracellular fluid
• Intravascular fluid
• Interstitial fluid
• Solvent
•   Electrolyte
•   Dissociate
•   ion
•   cation
•   Anion
•   Buffer
•   Isotonic
•   Hypotonic
•   Osmotic gradient
•   Diffusion
•   Osmosis
•   Active transport
•   Facilitated diffusion
•   Osmolality
• Osmolarity
• Osmotic pressure
• pH
•   PaO2
•   PaCO2
•   HCO3-
•   Acidosis
•   Alkalosis
•   Metabolic Acidosis
•   Respiratory Acidosis
•   Respiratory Alkalosis
WATER
• Most abundant substance in the body
• Aprox. 60% of TBW
• 70 kg adult (154 lbs) TBW aprox. 42L (11
  gallons)


             Water distribution
Various compartments all separated by a
  cell membrane
• Intracellular fluid (ICF)
Fluid inside body cells
Largest compartment
Contains 75% of TBW
Extracellular Fluid (ECF)
• All of the fluid found outside the body’s
  cells
• Contains the 25% of TBW
• Two divisions
      intravascular fluid
      interstitial fluid
Intravascular Fluid
• Outside the cells, within the circulatory
  system
• Pretty much the same as blood plasma
Interstitial Fluid
• Outside the cell membranes but outside
  the circulatory system
Examples of Interstitial Fluid
• Synovial fluid
• Aqueous humor of the eye
• Secretions
Water is a universal solvent
• Solvent
     dissolves other substances yeilding a
     solution
ELECTROLYTES
• when placed in water dissociates into
  electrically charged particles or IONS
Cation
• Positively charged ion
Anion
• Negatively charged ion
              Cations in our body
Sodium
• Na+
• Common in extracellular fluid
• Regulates the distribution of water
     WATER FOLLOWS SALT
• Transmission of nervous impulses
Potassium
• K+
• Prevelent in extracellular fluid
• Transmission of electrical impulses
Calcium
• Ca++
• Muscle contraction
• Nervous impulse transmission
Magnesium
• Mg++
• Several biochemical processes
    enzymes require magnesium to
          function
    ATP, DNA and RNA also need
          Magnesium
Anions in our body
Chloride
• Cl-
• Balances cations
• Renal function
• Closely associated with sodium
Bicarbonate
• HCO3-
• Primary buffer
Phosphate
• HPO4-
• Energy stores
• Buffer primarily in the intracellular space
OSMOSIS AND DIFFUSION
• Cells have semipermeable membranes
• When the concentration of fluid is equal on
  both sides of the membrane this is
  ISOTONIC
• When the concentration of fluid is less on
  one side of the membrane this is
  HYPOTONIC
• When the concentration of fluid is greater
  on one side of the membrane this is
  HYPERTONIC
• The difference in concentration is the
  OSMOTIC GRADIENT
• There is a shift to maintain homeostasis or
  a state of equilibrium
• Molecules will normally move to an area of
  higher concentration to that of lower
  concentration which is DIFFUSION
• Diffusion does not require E
• Water, which moves faster than
  electrolytes moves across the membrane
  to dilute the higher concentration of
  electrolytes
Osmosis
The movement of any solvent across the
  membrane
Active Transport {requires E}
• Movement against the osmotic gradient
     less concentrated to more concentrated
     area
                     i.e.
The inside of a myocardium cell must be
 negatively charged. Sodium being
 positively charged diffuses passively into
 the cell.
Sodium ions are pumped out of the cell
 while potassium is pumped into the cell
More sodium than potassium is moved
 achieving equillibrium
• Facilitated diffusion
Requires the assistance of a helper protein
  to move into the cell
An example is Glucose
Osmolality
• The concentration of solute per Kg
• The movement of water and solutes
  across the cell membrane maintains a
  state of equilibrium of osmolality
Osmolarity
• The concentration of solute per L of water
• Sodium maintains osmolality in the
  extracellular space
• Potassium maintains omolality in the
  intracellular space
ACID-BASE BALANCE
Acid-Base Balance
• The regulation of H+ in the body
• H+ Is acidic
• A deviation has an adverse affects on all
  biochemical functions of the body
pH
• Potential of Hydrogen
• Through metabolism and other
  biochemical processes, H+ is constantly
  produced
Normal pH is 7.35 to 7.45
<7.35 = Acidosis
>7.45 = Alkalosis
THREE FORMS OF REGULATION
Bicarbonate Buffer System
• The fastest
• The players [in equilibrium with H+ ]
      Bicarbonate {HCO3-}
      Carbonic Acid {H2CO3-}
• Either H+ will combine with bicarbonate ion
  to produce carbonic acid
                      or
Carbonic acid will dissociate into
  bicarbonate ion and hydrogen ion
• Erythrocytes contain have an enzyme
  called carbonic anhydrase which converts
  carbonic acid into CO2 and H2O and this
  occurs very rapidly
• Most buffering occurs in the erythrocytes
Respiration     | two other mechanisms
Kidney function| of regulation
Respiration
• An increase blows off CO2 thus decreases
  H+ thus decreases pH
Kidneys
• Modifies the concentration of HCO3- in the
  blood
• Increased elimination of HCO3- lowers pH
• Decreased elimination of HCO3- raises pH
The kidneys achieve acid-base balance by
  removing or retaining certain chemicals



   So what is the significance of all this?
The bottom line is to determine:
• If a patient is in a state of acidosis
• If a patient is in a state of alkalosis
• If the disturbance is respiratory in nature
• If the disturbance is metabolic in nature

In order to make this determination we must
  know the norms
• pH
7.35 to 7.45
• PaCO2
35 to 45 mm Hg
• HCO3-
22 to 26 mEq/L
• PaCO2
75 to 100 mm Hg
The first determination is if the patient is in a
  state of acidosis or alkalosis
• <7.35 Acidosis
• >7.45 Alkalosis
Next is to determine if the disturbance is
  respiratory or metabolic in nature
Assess the PaCO2 level
• If respiratory the PaCO2 should rise as the
   pH falls {acidosis} conversely the PaCO2
   should fall as the pH rises
SO…….
If the pH and PaCO2 are moving in opposite
   directions then the disturbance is
   respiratory
To determine if the disturbance is metabolic
   in nature the HCO3- is considered
• As pH increases, so should the HCO3-
• The opposite is true
                      Thus
If the pH and HCO3- is moving in the same
   direction then the disturbance is metabolic
   in nature
              Ph          PaCO2    HCO3-
              7.35-7.45   35-45    22-26
Respiratory   Fall        Rise     Normal
Acidosis

Respiratory   Rise        Fall     Normal
Alkalosis

Metabolic     Fall        Normal   Fall
Acidosis

Metabolic     Rise        Normal   Rise
Alkalosis
              Ph     PaCO2   HCO3-
              7.22   55      25

Respiratory
Acidosis

Respiratory
Alkalosis

Metabolic
Acidosis

Metabolic
Alkalosis
              Ph        PaCO2       HCO3-
              7.22      55          25

Respiratory   decreased increased   normal
Acidosis

Respiratory
Alkalosis

Metabolic
Acidosis

Metabolic
Alkalosis
              pH     PaCO2   HCO3-
              7.50   42      33

Respiratory
Acidosis

Respiratory
Alkalosis

Metabolic
Acidosis

Metabolic
Alkalosis
              pH          PaCO2    HCO3-
              7.50        42       33

Respiratory
Acidosis

Respiratory
Alkalosis

Metabolic
Acidosis

Metabolic     increased   normal   increased
Alkalosis
  COMPENSATION
• Remember with the buffering systems the
  body attempts to regulate hence a state of
  compensation
     uncompensated
     partially compensated
     fully compensated
• In a state of uncompensated or partially
  compensated the ph is still abnormal
• In full compensation the pH is normal but
  other values may not be
Partial Compensation
• Assess the pH
      this step is unchanged
• Assess the PaCO2
      remember the pH and PaCO2 should
      be moving opposite
If however they are moving in the same direction
   would indicate a metabolic disturbance
If as an example the PaCO2 was decreasing
   it would mean the body was blowing off
   CO2 in order to return pH to normal limits.
   Meaning the respiratory system is acting
   as a buffer system
As evidenced that this is actually metabolic
   in nature then plugging in the PaCO2
   moving in the same direction………
The determination then would be a metabolic
   disturbance with partial respiratory
   compensation
• Assess the HCO3- which moves in the same
   direction as the pH
If they move in the opposite direction, the
   disturbance would actually be respiratory in
   nature with the kidneys acting as the buffer
   system by retaining HCO3- .
TO SUMMARIZE
Fully
Compensated
              Ph          PaCO2   HCO3-
              7.35-7.45   35-45   22-26
Respiratory   Normal      Rise    Rise
Acidosis      but <7.40
Respiratory   Normal      Fall    Fall
Alkalosis     but >7.40
Metabolic     Normal      Fall    Fall
Acidosis      but <7.40
Metabolic     Normal      Rise    Rise
Alkalosis     but >7.40
Partially
Compensated
              Ph          PaCO2   HCO3-
              7.35-7.45   35-45   22-26
Respiratory   Fall        Rise    Rise
Acidosis

Respiratory   Rise        Fall    Fall
Alkalosis

Metabolic     Fall        Fall    Fall
Acidosis

Metabolic     Rise        Rise    Rise
Alkalosis
• The only difference between fully
  compensated and partially compensated is
  whether the pH has returned to within the
  normal range
RESPIRATORY ACIDOSIS
• Causes [hypoventilation]
Head injury
Narcotics
Sedatives
Spinal cord injury
Neuromuscular disease
Atelectasis
Pneumonia
Pneumothorax
Pulmonary edema
Bronchial obstruction
Pulmonary embolus
Pain
Chest wall injury or deformity
Abdominal distension
Signs and symptoms of respiratory acidosis
• Dyspnea
• Respiratory distress
• Headache
• Restlessness
• Confusion
• Drowsiness
• unresponsiveness
• Tachycardia
• Dysrhythmias
Respiratory Alkalosis
Causes [hyperventilation]
• Anxiety
• Fear
• Pain
• Fever
• Sepsis
• pregnancy
Signs and Symptoms
• Light-headedness
• Numbness/tingling
• Confusion
• Inability to concentrate
• Blurred vision
•   Dysrythmias
•   Palpitations
•   Dry mouth
•   Diaphoresis
•   Spasms of arms and legs
Metabolic Acidosis
Causes
• Renal failure
• DKA
• Anaerobic metabolism
• Starvation
• Salicylate intoxication
Signs and Symptoms
• Headache
• Confusion
• Restlessness into lethargy
• Kusmal respirations
• Warm flushed skin
• Nausea and vomiting
Metabolic Alkalosis
Causes
• Antacids
• Overuse of bicarbonate
• Lactate as used in dialysis
• Protracted vomiting
• Gastric suction
• High levels of aldosterone
Signs and symptoms
• Dizziness
• Lethargy
• Disorientation
• Seizure
• Coma
• Weakness
• Muscle twitching
• Muscle cramps
• Tetany
• Nausea and vomiting
• Respiratory depression
• Tetany
Involuntary contraction of muscles
• Proracted
Prolonged
• Aldosterone
a hormone that increases the reabsorption
  of sodium ions and water and the release
  of potassium ions
• Atelectasis
the lack of gas exchange within alveoli, due
  to alveolar collapse or fluid

				
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posted:1/18/2013
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