Transcript classes/nsg101/Acid Based balance student

ACID BASE BALANCE
Spring 2010
WHAT YOU WILL LEARN
Definition of Acid-Base Balance
 Deference between regulation of buffers,
respirations and renal system
 What acidosis is and the Difference between
Metabolic and Respiratory
 What alkalosis is and the Difference between
Metabolic and Respiratory
 Complications and diseases associated with both
processes

KEY TERMS
WHAT IS ACID BASE BALANCE

Acid-Base Balance refers to homeostasis of
hydrogen ion concentration in body fluids
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Expressed as pH
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Acids

Bases
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Health problems that may lead to an imbalance
PH AND
HYDROGEN ION CONCENTRATION

Lower the pH Higher the ?
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Heath Issues that can cause decrease in pH
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Higher the pH Lower the ?
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Heath issues that can cause increase in pH
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Normal pH of blood 7.35 to 7.45 (arterial)
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Normal pH of blood 7.32 to 7.42 (venous)
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Critical Values of pH
ACID-BASE REGULATION
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Buffer Systems
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Respiratory System
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Renal System
BUFFER SYSTEM
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What is a Buffer?
Fastest acting and primary regulator of Acidbase balance
3 types of chemical buffers
Buffers can not work with out proper function of
what systems
BICARBONATE BUFFER
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Bicarbonate is found in Extra-cellular and intracellular fluid
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Controls small fluctuation in pH
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Responds immediately
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Mainly buffers what 2 fluids
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Assisted by what organs
PHOSPHATE BUFFER
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Found in intra-cellular fluid as bicarbonates.
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Control small fluctuation in pH
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Responds Quickly
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Effective in Renal tubules, due to high levels of
phosphates
PROTEIN BUFFER
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
Most abundant buffer in the body
Found in ICF as hemoglobin and ECF as albumin
and globulins
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Works rapid

Works along same lines of bicarbonate system
RESPIRATORY REGULATION
Helps maintain pH
 Second line of defense
 Responds with in minutes
 Temporary
 Relies on Kidneys for long term regulation

RESPIRATORY
CO2 levels in blood regulated by Lungs
 Receptors in brain Medulla sense Ph changes
 Rate and Depth of Breathing changed to
compensate
 Low pH = faster or deeper breaths to eliminate
more CO2 from lungs; CO2 blood levels in blood
drop and pH increases

RESPIRATORY

High pH levels
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Respirations slow and shallow
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Reduces CO2 elimination
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Lower pH
RESPIRATORY

PaCO2 (partial pressure of Arterial CO2 in
arterial blood)
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Used to assess effectiveness of ventilation
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PaCO2 levels reflect CO2 in the blood.
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Normal levels 35-45 mm Hg
RENAL SYSTEM FOR REGULATION
Slowest of all regulating systems
 Can permanently adjust Blood pH
 Considered most powerful
 Kidneys can reabsorb acids and bases and
excrete them in urine
 Kidneys produce bicarbonate to replenish
 Kidneys regulate bicarbonate
 Normal levels of bicarbonate 22-26 mEq/L in
ABG
 Three mechanism of acid eliminations

RENAL
1.
2.
3.
Secretion of small amounts of free hydrogen in
renal tubule
Combination of hydrogen with ammonia to
form ammonium
Excretion of weak acids
RENAL
To much Acid or not enough Base




ph drops – kidneys reabsorb sodium bicarb
Hydrogen phosphate and ammonia excreted by
kidneys
Urine more Acidic (Normal Acidic level is 6pH)
Bicarb levels rise to normal levels and ph
Increases
RENAL
More base and less acid
 pH rises Kidneys excrete bicarb retain hydrogen
 Urine becomes alkaline, Bicarb levels drop and
pH decreases
IMBALANCES
Occur with compensatory mechanism fail
 Acidosis is excess of hydrogen ions and arterial
pH of less that 7.35
 Alkalosis is excess of base mainly bicarb in ECF
caused by increase of pH greater than 7.45
 ROME
Respiratory Opposite Metabolic Equal

RESPIRATORY OPPOSITE
Respiratory Acidosis level
 pH < that 7.35
 PaCO2 is > 45 mm Hg

Respiratory Alkalosis
 pH > than 7.45
 PaCO2 is < 35 mm Hg

METABOLIC EQUAL
Metabolic Acidosis Levels
 pH is < 7.35
 HCO3 < 24 mEq/L

Metabolic Alkalosis
 pH is >7.35
 HCO3 > 28 mEq/L

RESPIRATORY ACIDOSIS
Occurs whenever there is hypoventilation
 Common Causes include
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COPD
Over sedation
Chest Wall abnormality (obesity)
Severe Pneumonia
Atelectasis
Respiratory Muscle Weakness (Gilliain-Barre
syndrome)
Mechanical hypoventilation
CLINICAL MANIFESTATIONS

Neurologic

Cardiovascular

Gastrointestinal

Neuromuscular

Respiratory
DIAGNOSTIC FINDINGS

pH < 7.35

PaCo2 > 45mm Hg
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HCO3 is normal if uncompensated
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HCO3 is elevated if compensated
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Hyperkalemia
THERAPEUTIC MANAGEMENT
NURSING DIAGNOSIS
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Treatment of underlying cause
Improved Ventilation
Nursing Diagnosis
Ineffective breathing Patterns
Impaired Gas Exchange
Medications
Bronchodilators
Antibiotics
Agents used to decrease viscosity of secretions
Anticoagulants and thrombolytic to prevent emboli
RESPIRATORY ALKALOSIS
Caused by Hyperventilation as result of
pulmonary disorders
 Mechanical over ventilation
 Hypoxia
 Pulmonary Emboli
 Anxiety
 Fear
 Pain
 Exercise
 Fever

CLINICAL MANIFESTATIONS
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Cardiovascular

Respiratory
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Neurologic

Gastrointestinal
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Neuromuscular

Respiratory
CLINICAL FINDINGS

pH > 7.45

PaCO2 < 35mm Hg
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HCO3 normal if uncompensated
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HCO3 decreased if compensated
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Urine pH > 6
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Hypokalemia

Hypocalcemia
THERAPEUTIC MANAGEMENT
NURSING DIAGNOSIS
Therapeutic Management
 Treatment of underlying cause
 Re-breathe CO2 Re-breather Mask or paper bag
 O2 if patient is Hypoxic

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Nursing Diagnosis
Medication
 Sedatives to control Hyperventilation
 Antianxiety Me
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METABOLIC ACIDOSIS

Base bicarbonate loss from body fluids or occurs
when other acid other than Carbonic Acid
accumulates Either way Bicarbonate is deficient
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Very rarely occurs spontaneously

Usually occurs accompanied by other problems
CLINICAL MANIFESTATIONS
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Neurologic
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Cardiovascular

Gastrointestinal
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Neuromuscular
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Respiratory
CLINICAL FINDINGS
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pH < than 7.35
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Remember in Metabolic you look at HCO3
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HCO3 < 22 mEq/L
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PaCO2 is normal if uncompensated
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PaCO2 is decreased in compensated
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Hyperkalemia
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EKG Changes
THERAPEUTIC MANAGEMENT
NURSING DIAGNOSIS
Correct Underlying Problem
 Hydration
 Nutrients
 Electrolytes
 Administration of Sodium Bicarb or Sodium
lactate
 Administration of N/S Reg. Insulin and
potassium for DKA
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Nursing Diagnosis
METABOLIC ALKALOSIS

Loss of acid or gain on bicarbonate – Which in
turn causes Increase pH and Increase in HCO3
Conditions that cause Alkalosis
 Gastric suction, Prolonged vomiting
 Ingestion of bicarbonate bases (baking soda
antacids)
 Diuretic Therapy
 Potassium Deficit
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CLINICAL MANIFESTATIONS

Respiratory

Cardiovascular

Gastrointestinal
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Neuromuscular

Respiratory
CLINICAL FINDINGS
pH > 7.45
 Remember HCO3 is the focus
 HCO3 > 26 mEq/L
 PaCO2 is normal uncompensated
 PaCO2 is elevated if compensated
 Urine pH is >6 if compensated
 Hypokalemia
 Hypocalcemia
 Hyponatremia and Hypochloremia
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THERAPEUTIC MANAGEMENT
NURSING DIAGNOSIS
Correct Underlying Problem
 Provide sufficient chloride to enhance renal
absorption of sodium and excretion of HCO3 and
restore normal fluid balance
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Nursing Diagnosis
ABG INTERPRETATION
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
Step One
Assess the pH to determine if the blood is within
normal range, alkalotic or acidotic. If it is above
7.45, the blood is alkalotic. If it is below 7.35, the
blood is acidotic.
ABG’S
Step Two
 If the blood is alkalotic or acidotic, we now need
to determine if it is caused primarily by a
respiratory or metabolic problem. To do this,
assess the PaCO2 level. Remember that with a
respiratory problem, as the pH decreases below
7.35, the PaCO2 should rise. If the pH rises
above 7.45, the PaCO2 should fall. Compare the
pH and the PaCO2 values. If pH and PaCO2 are
indeed moving in opposite directions, then the
problem is primarily respiratory in nature.
ABG’S
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Step Three
Finally, assess the HCO3 value. Recall that with
a metabolic problem, normally as the pH
increases, the HCO3 should also increase.
Likewise, as the pH decreases, so should the
HCO3. Compare the two values. If they are
moving in the same direction, then the problem is
primarily metabolic in nature.
ABG’S
pH
PaCO2
HCO3
Respiratory
Acidosis
Normal
Respiratory
Alkalosis
Normal
Metabolic
Acidosis
Normal
Metabolic
Alkalosis
Normal
TEST OURSELVES
Jane Doe is a 45-year-old female admitted to the
nursing unit with a severe asthma attack. She
has been experiencing increasing shortness of
breath since admission three hours ago. Her
arterial blood gas result is as follows:
 Clinical Laboratory
PATIENT: DOE, JANE
DATE: 6/4/03 18:43
pH 7.22
PaCO2 55
HCO3- 25

Follow the steps:
 1. Assess the pH. It is low (normal 7.35-7.45);
therefore, we have acidosis.
 2. Assess the PaCO2. It is high (normal 35-45)
and in the opposite direction of the pH.
 3. Assess the HCO3. It has remained within the
normal range (22-26).
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ANSWER

Acidosis is present (decreased pH) with the
PaCO3 being increased, reflecting a primary
respiratory problem. For this patient, we need to
improve the ventilation status by providing
oxygen therapy, mechanical ventilation,
pulmonary toilet or by administering
bronchodilators.
ANOTHER CHANCE
John Doe is a 55-year-old male admitted to your
nursing unit with a recurring bowel obstruction.
He has been experiencing intractable vomiting
for the last several hours despite the use of
antiemetic. Here is his arterial blood gas result:
 Clinical Laboratory
PATIENT: DOE, JOHN
DATE: 3/6/03 08:30
pH 7.50
PaCO2 42
HCO3 - 33

Follow the three steps again:
 1. Assess the pH. It is high (normal 7.35-7.45),
therefore, indicating alkalosis.
 2. Assess the PaCO2. It is within the normal
range (normal 35-45).
 3. Assess the HCO3. It is high (normal 22-26) and
moving in the same direction as the pH.

ANSWER

Alkalosis is present (increased pH) with the
HCO3 increased, reflecting a primary metabolic
problem. Treatment of this patient might include
the administration of I.V. fluids and measures to
reduce the excess base.
COMPENSATION
The bodies attempt to return to normal state
using the opposite system
 pH is out of balance because of a respiratory
disorder, it will be the renal system that makes
the corrections to balance the body pH
 renal system is to blame for the pH disorder, the
respiratory system will have to compensate
 Complete compensation returns the pH balance
to normal.
 There are times when the imbalance is too large
for compensation to return the pH to normal.
This is called incomplete compensation.
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NURSING SCHOOL SURVIVAL RULES

When in doubt, wash your hands.
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The correct answer is either "hand washing" or
"patent airway."
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If it moves, ambulate it. If it doesn't move, turn and
reposition it Q2H.

Remember the 11th Commandment: Thou shalt not
cross thy sterile field.
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The instructor is ALWAYS right.

See Rule #5.