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Acid-Base Balance

Terms in this set (58)

Acid-Base Balance Definition:
-Homeostasis of hydrogen ion (H+) concentration in body fluids.

-Fluid contains equal number of positive charges, ions with negative charges.

-Balance occurs by matching rate of hydrogen ion production with loss
pH Scale
-pH lower the number= more acidic.

pH higher the number= more alkalotic.
Normal Blood pH
Arterial blood = 7.35 to 7.45.

Venous blood = 7.31 to 7.41
Changes in pH can affect
-Shape of hormones and enzymes

-Distribution of other electrolytes (fluid and electrolyte imbalance)

-Excitable membranes

-Effectiveness of hormones and drugs
Arterial pH is measured through ...

it is a measurement of....
arterial blood gas (ABG).

-Indirect measurement of hydrogen ion concentration
The pH is the expression of the balance between:
carbon dioxide (CO2), which is regulated by the lungs, and bicarbonate (HCO3 -), a base regulated by the kidneys.
More hydrogen=
more acidic the body fluids = the lower the pH.
Lower the concentration of hydrogen=
more alkaline the body fluids = the higher the pH.
Origination of Metabolic Acids:
Incomplete breakdown of glucose:
--Often occurs in anaerobic metabolism (hypoxia, sepsis, shock)
--Produces lactic acid

Breakdown of protein and fats
--From ketoacids

Destruction of cells
Bicarbonate
Weak base

Major buffer of extracellular fluid (ECF)
Two sources of bicarb
-Intestinal absorption of ingested bicarbonate into ECF.

-Kidney absorption and breakdown of carbonic acid.
Level of Bicarb is usually....
20 times greater than that of carbonic acid
Compensatory Mechanisms
Chemical and protein buffers (Are the first line of defense).

Respiratory buffers (Second line of defense)

Renal buffers (Third line of defense)
Chemical and protein buffers:
--Either bind or release hydrogen ions as needed.

--Respond quickly to changes in pH
Respiratory Buffers:

it controls levels of:
-Second line of defense

-Controls level of H+ through control of CO2 levels.
When level of CO2 changes , signal sent brain:
~Hyperventilation to decrease H+ ions

~Hypoventilation to increase H+ ions
Lungs compensate for acid-base imbalances:
of metabolic origin
Acid-Base Control Actions & Mechanisms: Kidneys

effectiveness:


Speed:
Third line of defense against pH changes.

More effective at regulating acid-base balance.

Slower mechanisms for regulating acid-base balance
Kidney movement of bicarbonate
Increased level of H+ = reabsorption and production of bicarbonate

Decreased level of H+ = excretion of bicarbonate
Kidneys help to form:
Formation of acids and ammonium
Kidneys can correct/compensate for pH changes when:
respiratory system is overwhelmed or unhealthy
Compensation: definition
Process by which the body attempts to correct the changes/imbalances
Fatal pH levels
pH <6.9 or >7.8 usually fatal
Respiratory system is sensitive to
acid-base changes; can begin compensating in seconds to minutes
Kidneys more powerful:
result in rapid changes in ECF composition; fully triggered for imbalance of several hours to days
Metabolic acidosis:
Cause:
Compensation:
Effects on ABGs:
Cause: excess nonvolatile acids; bicarbonate deficiency

Compensation: rate and depth of respirations increase, eliminating additional CO2

Effects on ABGs:
Decrease pH
Decrease HCO3-
Decrease PaCO2
Metabolic alkalosis:
Cause:
Compensation:
Effects on ABGs:
Cause: bicarbonate excess

Compensation: rate and depth of respirations decrease, retaining CO2

Effects on ABGs:
Increase pH
Increase HCO3-
Increase PaCO2
Respiratory Acidosis:
Cause:
Compensation:
Effects on ABGs:
Cause: retained CO2 and excess carbonic acid.

Compensation: Kidneys conserve bicarbonate to restore carbonic acid: bicarbonate ratio of 1:20

Effects on ABGs:
decrease pH
Increase PaCO2
Increase HCO3
Respiratory Alkalosis
Cause:
Compensation:
Effects on ABGs:
Cause: loss of CO2, and deficient carbonic acid.

Compensation: Kidneys excrete bicarbonate and conserve H+ to restore carbonic acid: bicarbonate ratio.

Effects on ABGs:
Increase pH
Decrease PaCO2
Decrease HCO3
Acid Base Balance: Health Promotion and Disease Prevention
-Encourage a healthy diet and physical activity.

-Limit the consumption of alcohol.

-Encourage drinking six to eight glasses of water daily.

-Maintain an appropriate weight for height and body frame.

-Promote smoking cessation
Metabolic acidosis: Laboratory Assessment:
-pH <7.35 (LOW)

-Bicarbonate <21 mEq/L (LOW)

-Pao2 normal

-Paco2 normal or slightly decreased

-Serum potassium high
Metabolic Acidosis causes.
Cardiac arrest, renal failure, DKA, extended diarrhea, tachypnea, ingestion of aspirin or antifreeze.
Metabolic Acidosis:
Hydrogen Ions:
Overproduction
Under-elimination
Metabolic Acidosis: Bicarbonate ions
Under-production
Over-elimination
Metabolic Acidosis:
~~Acid in the blood combines with oxygen for metabolism.

~~Lack of oxygen-rich blood results in lack of acid use
Metabolic Acidosis: Presentation:
Tachycardia, pulmonary edema, tachypnea, confusion, coma
Metabolic Acidosis subjective and objective findings:
-Bradycardia, weak peripheral pulses, hypotension, tachypnea

-Dysrhythmias

-Neuro: Muscle weakness, hyporeflexia, flaccid paralysis, fatigue, confusion

-Respiratory: Rapid, deep respirations
Skin: Warm, dry, flushed
Interventions for Metabolic Acidosis:
Treat the underlying cause.
~Hydration
~Drug therapy
---Insulin to treat DKA
---Antidiarrheals
---Bicarbonate (only with low serum level)
........Dose is 1 mEq/kg
Respiratory Acidosis Levels:
~pH <7.35 (LOW)

~Pao2 low

~Paco2 high

~Serum bicarbonate variable

~Serum potassium levels elevated (if acute acidosis)

~Serum potassium levels normal or low (if renal compensation present)
Respiratory Acidosis
Respiratory function is impaired, causing problems with O2 and CO2.
Respiratory Acidosis: Retention of CO2
~Respiratory depression

~Inadequate chest expansion

~Airway obstruction

~Reduced alveolar-capillary diffusion
Hallmark of respiratory acidosis:
Decreased Pao2 with rising Paco2
With respiratory acidosis the patient is not
breathing adequately.

~~Not removing enough CO2
Respiratory Acidosis: Clinical presentations:
-Altered level of consciousness
-Tachycardia
-Diaphoresis
-Headache
Respiratory Acidosis Causes:
-Poor respirations
-COPD
-Overdose
-Pneumonia
-Smoke inhalation
-Pneumothorax
-Airway obstruction
Respiratory Acidosis Subjective and Objective Findings
Tachycardia (severe may result in bradycardia); tachypnea

Dysrhythmias

Neuro: Anxiety, irritability, confusion, coma

Respiratory: Ineffective, shallow, rapid respiration
Skin: Pale, cyanotic
Interventions Respiratory Acidosis:
-Treat the underlying cause

-Focus is on improving ventilation and oxygenation, maintaining patent airway.

-Drug therapy
~~~Bronchodilators
~~~Anti-inflammatories
~~~Mucolytics

-Oxygen therapy

-Pulmonary hygiene

-Ventilation support- includes positioning for better lung expansion and possibly mechanical ventilation.

-Prevention of complications
Metabolic Alkalosis:
base excess:
- Excessive intake bicarbonates, carbonates, acetates, citrates
Metaboliv alkalosis: Acid Deficit
- Prolonged vomiting, excess cortisol, hyperaldosteronism, thiazide diuretics, prolonged NG suction
Hallmark of base excess acidosis:
ABG result with ↑ pH and ↑ bicarbonate level with normal O2 and CO2 levels
Metabolic Alkalosis Causes:
-Diuretics

-Cystic fibrosis

-Chewing tobacco

-Penicillin

-Too much bicarbonate administration
Metabolic Alkalosis S/S
Tachycardia, normo/hypotensive

Dysrhythias

Neuro: headache, numbness, tingling, tetany, muscle weakness, confusion, hyperreflexia, seizures, confusion

Respiratory: Depressed skeletal muscles resulting in ineffective breathing
Respiratory Alkalosis:
Hyperventilation - Anxiety, fear, improper vent settings, stimulation of central respiratory center due to fever, CNS lesion, salicylates

Results in removal of too much CO2
Hallmark of respiratory alkalosis:
-ABG result with ↑ pH coupled with low CO2 level

-O2 and bicarbonate usually normal
Respiratory Alkalosis Causes:
-Shock

-Kussmaul's respirations
Respiratory Alkalosis S/S
Tachypnea
Neuro: Anxiety, tetany, convulsions, tingling, numbness
Palpitations, chest pain, dysrhythmias
Rapid, deep respirations
Interventions: Alkalosis
Treat the underlying cause

Prevent further losses of hydrogen, potassium, calcium, chloride ions

Respiratory: Administer oxygen, reduce anxiety, rebreathing techniques

Metabolic: Varies with cause:
~~Restore fluid balance
~~Antiemetics

Monitor changes, provide safety

Modify or stop gastric suctioning, IV solutions with base, drugs that promote hydrogen ion excretion

Administer electrolyte solutions when indicated
Interpreting ABGs
Step 1: Analyze the pH
Step 2: Analyze the CO2 level and Bicarb (HCO3) level
Step 3: Identify the type of imbalance
Step 4: Evaluate the PaO2 and SaO2
Step 5: Determine Compensation
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