Download ACID BASE BALANCE

NUR 101
M. Gardner
Copyright2/4/2013
 In
order to meet homeostasis, the body
fluids must maintain a stable chemical
balance of hydrogen ions in body fluids.
 This is done by regulating their acidity
/alkalinity.
 Deviation from a normal value indicates
that the client is experiencing an
acid/base imbalance
 ACID
– substance that releases hydrogen
ions (H+)
 BASE
 This
– accept hydrogen ions in solution
relationship is measured as pH.
 Measurement
of ABGs involves analysis
of several components:
 pH
 PCO2
 PO2
 HCO3
Arterial blood gas analysis
 pH – measures the hydrogen ion
concentration
 it is an indication of the blood’s acidity or
alkalinity.
 Normal pH of body fluids is 7.35-7.45
 pH 7 is neutral
 pH <7 is acid, pH >7 is alkaline (base)
acidic----neutral----alkaline
PaCO2/PCO2 35-45mmHg
 Carbon
dioxide/CO2
 Reflects adequate ventilation by the lungs
 Hyperventilation occurs PaCO2 <35mmHg.
RR/depth increases the more carbon dioxide is
exhaled
 Hypoventilation occurs PaCO2>45mmHg.
 RR/depth decreases, more carbon dioxide is
retained – increasing the concentration of CO2
HCO3 /Bicarbonate
 normal range 22-26mE/L
 base regulated by the kidneys
 the kidneys excrete and retain HCO3 to
maintain a normal acid/base balance
 is a principal buffer of the ECF compartment
<
22mEq/L – indicates metabolic acidosis
 >26meq/L – indicates metabolic alkalosis
 PO2
– oxygen in arterial blood
 Normal range – 90-100mmHg
 Several
body systems are actively involved
in maintaining the narrow pH range
necessary for optimal function.
 This includes  buffers, respiratory system,
renal system
 Buffers
 maintain acid/base balance by
neutralizing excess acids/bases
 The lungs/kidneys help maintain a normal
pH by either excreting/retaining
acid/bases.
A
strong acid added to the ECF causes
the bicarbonate to become depleted 
neutralizing the acid  pH drops
acidosis
 A strong base is added to the ECF,
depleting carbonic acid  the pH rises
 alkalosis
 Buffer
reaction is immediate
 Lungs
regulate acid/base balance by
eliminating or retaining carbon dioxide
(CO2)
 Carbon
dioxide  powerful stimulator of
the respiratory center
 CO2
+H2O=H2CO3  this reaction is
reversible
 Kidneys
kick in by excreting or retaining
bicarbonate and hydrogen ions.
 Slower
to respond to changes 
hour/days to correct imbalances
 Excessive
hydrogen ions are present and
the pH falls (acidosis)  kidneys
reabsorb bicarbonate & excrete
hydrogen ions.
 With
alkalosis and high pH  excess
bicarbonate is excreted and hydrogen
ions are retained.
pH
Pa CO2
PaO2
HCO3
7.35 – 7.45
35-45 mm Hg
80 -100 mm Hg
22-26 mEq/L
O2 Saturation
95-100%
 Are
classified as respiratory or metabolic
 considering the general/underlying
cause of the disorder.
 Respiratory acidosis/alkalosis 
retention/excretion of CO2
 Bicarbonate /hydrogen levels are
regulated by the kidneys, any problems
 metabolic acidosis/alkalosis
 Client
hypoventilates CO2 builds up in
the bloodstream and the pH drops below
normal.
 Kidneys try to compensate by conserving
bicarbonate  raises the pH
pH <7.35
PaCO2 >45
HCO3 normal or elevated if compensating
Causes:
 asthma, COPD
 chest wall trauma
 sedation medications
 Acute lung conditions
Clinical Manifestations
 apprehension
 dizziness
 muscular twitching
 warm flushed skin
 lethargy
 diminished/absent breath sounds over
the affected area
Interventions
 bronchodilator
 chest physiotherapy
 suction
 T,C, & DB
 narcotic antagonist
 Pt. hyperventilating
 this causes the
lungs to blow off CO2.
ABG
pH > 7.45
pCO2 <35
HCO3 - normal or below 22, if
compensating
Causes
Hyperventilation due to
 extreme anxiety
 pain
 inappropriate mechanical ventilator
settings
 elevated body temperature
Clinical Manifestations
 increase in rate & depth of respirations
 tachycardia
 anxious, restlessness
Interventions
 treat the underlying disorder
 allay anxiety – prevent hyperventilation
 monitor VS
 assist client to breathe in a paper bag
 Bicarbonate
levels are low in relation to
the amount of carbonic acid  pH low.
ABG
 pH is below 7.35
 pCO2 normal, if less than 35 may be
compensated
 HCO3 -- <22 mEq/L
Causes
 starvation
 diarrhea
 poisoning
 diabetes
Clinical Manifestations
 headache
 lethargy
 confusion
 tachypnea with deep respirations
Interventions
 treat the underlying problem
 replace F/E
 sodium bicarbonate – IV
 monitor neurological status
 Commonly
associated with hypokalemia
 Increase levels of bicarbonate
ABG
 pH >7.45
 pCO2 normal or above 45 if
compensating
 HCO3 >26
Cause
 Excessive acid loss from the GI tract
 Diuretic therapy
Clinical manifestations
 Slow, shallow respirations
 S&S are commonly associated with an
underlying condition
Interventions
 monitor VS
 maintain patent IV access
 monitor I&O
 replace F&E
 It
is a respiratory problem if the pH and
CO2 are traveling in the opposite
directions.
 pH<
7.35 & CO2 >45 = Respiratory Acidosis
 pH >7.35 & CO2<35 = Respiratory Alkalosis
 It
is a metabolic problem if the pH & HCO3
are traveling in the same directions
 pH
<7.35 and the HCO3 <22 = Metabolic Acidosis
 pH >7.45 and the HCO3>26 = Metabolic Alkalosis
 pH
– 7.30
 pCO2 – 36mmHg
 HCO3 – 14mEq/L
 pH
– 7.52
 pCO2 – 47 mmHg
 HCO3 – 43 mEq/L
 The
patient comes to the ER with
complaint of vomiting for 3 days. Which
acid base imbalance is she at risk for?
 The
patient has just returned from
surgery. He was medicated twice with
narcotic analgesics in the PACU. He is
difficult to arouse and has a respiratory
rate of 12. what acid/base imbalance is
he at risk for?
 Some
day you will know all of this!!!!!!!!