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ACID – BASE BALANCE
HOMEOSTASIS
Relative [ ] of hydrogen ions
pH – potential hydrogen
Normal pH: 7.35 – 7.45
<7.35 is acidosis
>7.45 is alkalosis
Deviation of 0.4 in either direction
can be fatal
ACIDOSIS
Metabolic Acidosis
Excessive blood acidity or loss of
bicarbonate
Causes
ingestion of something that is or
can
be metabolized to an acid
such as…..
Wood alcohol
Antifreeze
Large doses of ASA
Abnormal metabolism
Advanced stages of shock
Poorly controlled IDDM
Normal levels of acid if kidneys aren’t
functioning normally
Symptoms
Mild metabolic acidosis may have no sx.
Usually experiences
nausea
vomiting
fatigue
Breathing becomes deeper and slightly
faster
As acidosis worsens:
Extremely weak and drowsy
May feel confused
Increasingly nauseated
Eventually b/p can fall leading to shock,
coma, or death
Treatment:
Depends primarily on the cause
insulin
removing toxic substances
RESPIRATORY ACIDOSIS
Build up of CO2 in the blood from
poor lung function or slow breathing
Blood becomes acidic -> pH drops 
respiratory center in the brain
stimulates faster and deeper
breathing
Develops when…….
Develops when the lungs do not expel
CO2 adequately….such as
Emphysema
Chronic bronchitis
Severe pneumonia
Pulmonary edema
Asthma
Diseases of the nerves or muscles of
the chest
If overly sedated from narcotics and
strong sleeping medications that
slow respirations
Symptoms:
First symptom may be headache and
drowsiness
Drowsiness may progress to stupor
or coma
ABGs
Treatment…..
Aims at improving function of the
lungs
i.e. drugs to improve breathing
If acidosis is mild, IV fluid may be all
that is needed
If severe; HCO3- (provides only
temporary relief and may cause
harm by overloading the body with
Na+ and H2O
Treatment
Slow down rate
Pain relief
Other facts to ponder………….
J:\Class Presentations\BA Acid Base
Disturbances.doc
Life essential functions like K+ and
Na+ channels are inactivated by
acidosis
A habitually acid pH can directly
cause immediate weight gain
Fasting and dieting are known acid
producing conditions
One way the body compensates is to
deposit excess acid into tissues and
joints
Acid producing foods create excess
mucus, which congests the system
and block oxygen from entering
ALKALOSIS
Overabundance of bicarbonate in the
blood
Loss of acid from the blood
Respiratory Alkalosis
Low levels of CO2 in the blood that results
from rapid or deep breathing
Hyperventilation
anxiety
cirrhosis
low levels of oxygen in the blood
fever
ASA overdose
METABOLIC ACIDOSIS
Body looses too much acids
Gain too much base
stomach acid is lost during periods of
prolonged vomiting
excessive loss of Na+ or K+ affects the
kidney’s ability to control the
blood’s acid-base balance
loss of K+ - use of diuretics or
corticosteroids
Corticosteroids
Steroid hormones
Synthesized from cholesterol
Involved in stress response, immune
response, regulation of inflammation,
carbohydrate metabolism, protein
catabolises blood electrolyte level
and behavior
Catabolism: breaks down molecules
into smaller units and releases
energy
Alkalosis may cause:
Irritability
Muscle twitching
Muscle cramps
If severe, prolonged contraction and
spasms of muscle (tetnaory)
Treatment
Metabolic
Replacing H2O, Na+, and K+ while
treating underlying cause
Next: …………..
FLUIDS AND
ELECTROLYTYES
Water
60% total body weight
Distributed into various compartments,
separated by cell membranes
Largest compartment is intracellular
environment
ICF
All the fluid found inside body cells
75% of all water is found within this
compartment
Extracellular compartment
2 divisions
Intravascular fluid
Outside the cells and within the
circulatory system. Essentially the
same as the blood plasma
Interstitial fluid
Outside the cell membranes, not
within the circulatory system
TBW
Infants – 75-80%
Infants have less fat. Fat does not
absorb water. Less fat, more water
Water is essential for high rates of
metabolism necessary to promote growth
With age
Loss of muscle mass inc. % of fat
Body’s decreasing ability to regulate fluid
levels lower TBW to 45-55%
Elderly and very young are at high risk for
dehydration and disorders related to to
electrolyte imbalances
ELECTROLYTES
Dissociate in electronically charged
particles when placed into water
ions
Cations
+ charge
Anions
- charge
Cations
Na+
Most prevalent in extracellular fluid
Plays major role in distribution of
water
Important in the transmission of
nervous impulses
K+
Intracellular fluid
Transmission of electrical impulses
Ca++
Major role in muscle contraction
Nervous impulse transmission
Mg++
Necessary for several biochemical
processes (over 300)
Prevents over excitability of muscles
½ found in bone
½ found predominantly inside cells of
tissues and organs
Helps maintain normal nerve and muscle
function
Regulates heart rhythm
Supports healthy immune system
Keeps bones strong
Helps regulate blood sugar levels
Promotes normal blood pressure
Known to be involved in protein
synthesis and metabolism
ANIONS
ClPlays a major role in fluid balance
and renal function
HCO3Principal buffer
Phosphate
HPO4Body energy stores
Closely associated with Mg++ in
renal function
Acts as a buffer primarily in the
intracellular space
OSMOSIS AND DIFFUSION
Isotonic
When solutions on opposite sides of a
semipermiable membrane are equal
in [ ]
> on one side – hypertonic
< on one side – hypotonic
Difference in [ ] – osmotic gradient
Homeostasis
The tendency to keep the balance of
water
electrolytes are = on both sides of
the
membrane.
Diffusion
Movement from an area of higher [ ]
to lower [ ] and does not require
energy
Osmosis
The passage of any solvent usually water
through a membrane
Active Transport
Movement of a substance across the cell
membrane against the osmotic gradient or
toward the side that already has more of
the substance; requires an expenditure of
energy
Facilitated diffusion
Diffusion of a substance such as
glucose that requires the assistance
of a helper or carrier protein
FLUIDS
COLLOIDS
Contain large proteins
Cannot pass through a capillary
membrane
Remains in the circulatory system
Increases volume of blood and fluid
contained within the blood vessels
CRYSTALLOID
Contain electrolytes and water
Tonicity: number of particles per unit
volume
Isotonic
Tonicity equal to blood plasma
Will not cause a significant fluid or
electrolyte shift
HYPERTONIC
Higher solute [ ] that the cells
Causes fluid shift out of intracellular
compartment into extracellualar
compartment
HYPOTONIC
Lower solute [ ] than the cells
Movement extracellular 
intracellular
ABGs
Determine pH but also to differentiate
respiratory / metabolic acidosis / alkalosis
Norms
pH
7.35
- 7.45
PaCO2
35 - 45
PaO2
greater than 80
HCO322 - 28
PaCO2
Amount of CO2 dissolved in arterial
blood
PaO2 amount of oxygen dissolved in
arterial blood
HCO3 amount of bicarbonate
Interpretation
(R)espirtory (O)pposite, (M)etabolic
(E)qual
If the pH is opposite the PaCO2 (high
or low) then it’s respiratory if the pH
is equal to the HCO3, it is metabolic
Problem #1
pH
7.30
PaCO2
50
HCO3
26
PaO2
60
Acidosis or Alkalosis?
Metabolic or Respiratory?
Answer………
Respiratory Acidosis
Why?
pH is high indicating Acidosis
pH is low; PaCO2 is high {opposite}
indicating this is respiratory
Problem #2
pH
7.50
PaCO2 43
HCO3
45
PaO2
80
Acidosis or Alkalosis?
Metabolic or Respiratory?
Answer………
Metabolic Alkalosis
Why?
pH is high indicating alkalosis
pH high; HCO3- high {equal}
Indicating this is metabolic
METABOLIC ACIDOSIS