Acid-Base Balance

ACID-BASE BALANCE

Objectives

  • Define and describe the concept of acid-base balance.

  • Identify risk factors for disorders that cause acid-base imbalances.

  • Recognize when an individual has an acid-base imbalance.

  • Provide appropriate nursing and collaborative interventions to optimize acid-base balance.

pH

  • Blood is slightly alkaline at pH levels of 7.35 to 7.45.

  • A pH less than 7.35 indicates acidosis.

  • A pH greater than 7.45 indicates alkalosis.

  • pH is a measure of H+ ion concentration:

    • Increase in H+ concentration = acidity.

    • Decrease in H+ concentration = alkalinity.

Definition of Acid-Base Balance

  • Acid-base balance is the process of regulating:

    • pH

    • Bicarbonate concentration

    • Partial pressure of carbon dioxide within body fluids.

  • Normal values:

    • pH: 7.35-7.45

    • pCO2: 35-45 mmHg

    • pO2: 60-80 mmHg

    • HCO3: 22-26 mEq/L

Mechanisms to Regulate Acid-Base Balance

  • Three primary mechanisms maintain pH between 7.35 and 7.45:

    • Buffer system

    • Respiratory system

    • Renal system

Blood Gas Values

  • Arterial blood gas (ABG) values provide objective information about:

    • Acid-base status

    • Underlying causes of imbalance

    • Body's ability to regulate pH

    • Partial pressure of arterial O2 (PaO2) and O2 saturation.

Exemplars of Acid-Base Imbalances

  • Respiratory Acidosis

  • Respiratory Alkalosis

  • Metabolic Acidosis

  • Metabolic Alkalosis

Metabolic Acidosis

  • Definition:

    • pH less than 7.35 and bicarbonate less than 22 mEq/L.

  • Causes:

    • Lactic acidosis

    • Diabetic ketoacidosis

    • Aspirin excess

    • Renal failure

    • Accumulation of metabolic acids.

  • Pathophysiology:

    • Increased acid production leads to decreased bicarbonate concentration.

    • CO2 levels decrease (PaCO2 < 35 mmHg) due to respiratory compensation.

    • Potassium (K+) and H+ ions exchange places; K+ shifts into blood, leading to hyperkalemia.

Metabolic Acidosis - Risk Factors

  • Rarely a primary disorder; often secondary.

  • Causes include:

    • Tissue hypoxia (shock, cardiac arrest)

    • Type I diabetes

    • Aspirin excess

    • Renal failure

    • Loss of bicarbonate (e.g., diarrhea).

Metabolic Acidosis - Clinical Manifestations

  • Weakness

  • Fatigue

  • Headache

  • Diminished appetite

  • Nausea and vomiting

  • Abdominal pain

  • Change in level of consciousness (LOC), potential coma

  • Cardiac dysrhythmias

  • Cardiac arrest

  • Kussmaul’s respirations (rapid and deep respiration).

Metabolic Acidosis - Collaborative Care

  • Focused on treating the primary disorder and reducing effects on cardiac function:

    • Diagnostics include ABGs and electrolytes.

    • Pharmacological treatments:

    • Bicarbonate supplementation if indicated.

    • In instances of diabetic ketoacidosis, administer normal saline IV and insulin followed by glucose.

    • For lactic acidosis, correct underlying issues.

    • In chronic renal failure, management depends on pH and bicarbonate levels.

    • In diarrhea-induced acidosis, correct the cause, and ensure fluid and electrolyte replacement.

Metabolic Acidosis - Assessment

  • Health History:

    • Monitor symptoms such as diminished appetite, nausea, vomiting, lethargy.

    • Duration of symptoms and precipitating factors.

  • Physical Assessment:

    • Assess mental status and LOC.

    • Monitor vital signs and ABGs.

    • Evaluate fluids and outputs.

    • Check for abdominal distention.

Metabolic Acidosis - Clinical Problems

  • Potential problems include:

    • Acute confusion related to acid-base imbalance and associated electrolyte disturbance.

    • Impaired memory due to metabolic acidosis.

    • Imbalanced nutrition due to inability to ingest or absorb nutrients.

    • Risk for electrolyte imbalance due to renal function impact.

    • Risk for injury related to disorientation, weakness, or stupor.

    • Risk for decreased cardiac output from dysrhythmias or hyperkalemia.

    • Risk for shock due to abnormal metabolic states or decreased tissue perfusion.

Metabolic Acidosis - Planning

  • Goals include:

    • Client will describe and demonstrate preventive measures connected to chronic conditions.

    • pH will remain normal range.

    • Control over disease processes causing acid-base imbalances.

    • Vital signs remain stable and within normal limits for age/condition.

    • Maintain baseline cardiac rhythm.

    • Serum electrolyte levels will normalize.

Metabolic Acidosis - Implementation

  • Risk for Decreased Cardiac Output:

    • Monitor vital signs and ECG for dysrhythmias.

    • Track laboratory values including ABGs and serum electrolytes.

  • Risk for Excess Fluid Volume:

    • Maintain fluid replacement, check heart and lung sounds, assess for edema, monitor urine output hourly, assess daily weights, consider diuretics.

  • Risk for Injury:

    • Monitor neurological functions, implement safety measures, and provide orientation support.

Metabolic Acidosis - Care in the Community

  • Important aspects include:

    • Dietary management and medication adherence.

    • Strategies for managing alcohol dependency.

    • Guidance for renal failure maintenance.

    • Instructing patients to contact healthcare providers for uncontrolled diarrhea.

Metabolic Acidosis - Evaluation

  • Expected outcomes include:

    • Client maintains pH in the normal range.

    • Vital signs consistently within the normal range for respective age and condition.

    • Adequate oxygenation of tissues.

    • Client able to describe measures to control disease processes preventing pH imbalance.

Metabolic Alkalosis

  • Definition:

    • Characterized by a pH greater than 7.45 and bicarbonate greater than 25 mEq/L.

    • Caused by excessive acid loss, often via kidneys or gastric suction, or by a shift of H+ into the cells.

  • Compensation:

    • Respiratory system adjusts by slowing respiration, retaining CO2, leading to an increase in PaCO2 (> 45 mmHg).

    • K+ moves into cells, causing hypokalemia.

Metabolic Alkalosis - Risk Factors

  • Rarely occurs as a primary condition; commonly associated with:

    • Hospitalizations

    • Hypokalemia

    • Use of alkalinizing solutions.

Metabolic Alkalosis - Clinical Manifestations

  • Result from decreased ionization of calcium, symptoms may include:

    • Numbness or tingling around the mouth, fingers, and toes.

    • Dizziness.

    • Trousseau’s sign (tetany).

    • Muscle spasms.

    • Respiratory depression, potentially leading to respiratory failure with hypoxemia.

Metabolic Alkalosis - Collaborative Care

  • Pharmacologic therapies:

    • Potassium chloride and sodium chloride fluids.

  • Laboratory/Diagnostic tests:

    • ABGs, serum electrolytes, urine pH, and ECG monitoring.

Metabolic Alkalosis - Assessment

  • Obtain health history to identify precipitating factors and duration of symptoms.

  • Physical Assessment:

    • Monitor vital signs, muscle strength, and deep tendon reflexes.

Metabolic Alkalosis - Clinical Problems

  • Potential issues include:

    • Impaired gas exchange due to ineffective breathing patterns.

    • Deficient fluid volume resulting from fluid loss through vomiting or gastric suctioning, or failure of regulatory mechanisms.

Metabolic Alkalosis - Planning

  • Goals include:

    • Returning oxygen saturation levels to 95% or greater.

    • Restoring fluid and electrolyte volumes to normal or nearly normal.

Metabolic Alkalosis - Implementation

  • Impaired Gas Exchange:

    • Monitor respiratory status; assess skin color and mental status.

    • Position client in Semi-Fowler’s as tolerated.

    • Administer ordered oxygen and allow rest periods.

  • Deficient Fluid Volume:

    • Accurately assess intake and output.

    • Monitor vital signs and central venous pressure (CVP).

    • Perform daily weights and administer IV fluids as needed.

    • Check serum electrolytes, osmolality, and ABG values.

Metabolic Alkalosis - Care in the Community

  • Instruct on appropriate antacid use and potassium supplementation.

  • Encourage communication with healthcare providers about uncontrolled vomiting.

Metabolic Alkalosis - Evaluation

  • Desired outcomes include:

    • The client can describe appropriate antacids and their acceptable usage to prevent metabolic alkalosis.

    • The client describes the self-administration procedures for oral potassium supplements.

    • The client knows when to notify their provider based on daily weight changes.

    • pH and serum electrolyte values return to a normal range.

Respiratory Alkalosis

  • Characterized by:

    • Lethargy, confusion, and possibly seizures.

    • Presentation of deep, rapid breathing, tachycardia, hypokalemia, numbness, tingling of extremities.

    • Loss of CO2 from lungs.

    • Common causes include hyperventilation (due to anxiety, pulmonary embolism, fear) and mechanical ventilation.

Respiratory Alkalosis - Definition

  • pH greater than 7.45 and PaCO2 less than 35 mmHg indicating carbonic acid deficit, often due to hypoxemia or hyperventilation.

  • The kidneys may fail to adapt rapidly, with bicarbonate levels remaining normal.

  • Alkalosis increases the extracellular calcium binding to serum proteins, giving rise to neuromuscular excitability.

Respiratory Alkalosis - Risk Factors

  • Common causes:

    • Anxiety

    • Mechanical ventilation

    • Critical illness conditions.

Respiratory Alkalosis - Clinical Manifestations

  • Symptoms include lightheadedness, panic feelings, circumoral and distal extremity paresthesia, positive Chvostek and Trousseau’s signs.

Respiratory Alkalosis - Collaborative Care

  • Pharmacologic Therapies:

    • Sedatives or antianxiety medications may be used.

  • Respiratory Therapies:

    • Paper bag breathing with caution, breathing exercises, environmental control, oxygen administration, and correction of ventilatory settings if needed.

Respiratory Alkalosis - Assessment

  • Health History:

    • Investigate history of anxiety disorders and triggering events.

  • Physical Assessment:

    • Monitor breath sounds, neurological functions, respiratory and cardiac status, and changes in LOC.

Respiratory Alkalosis - Clinical Problems

  • Potential issues include ineffective breathing pattern related to anxiety and risk for electrolyte imbalance due to over-ventilation from mechanical support.

Respiratory Alkalosis - Planning

  • Goals include:

    • Normalizing respiratory rate and rhythm.

    • Maintaining safety and appropriate fluid status.

Respiratory Alkalosis - Developmental Considerations

  • Adjustments for different age groups:

    • Infants: Soft, comforting touch and swaddling.

    • Toddlers/Preschoolers: Recognize emotions, calm holding, provide toys.

    • School Age: Gentle discussions, storytelling, explain sensations.

    • Older Children: Techniques like guided imagery and music may help reduce anxiety.

Respiratory Alkalosis - Implementation

  • Assess respirations and vital signs.

  • Identify underlying cause and reassure the patient.

  • Teach slow breathing techniques and protect from injury.

  • Consider referrals for counseling as needed.

Respiratory Alkalosis - Evaluation

  • Successful outcomes include:

    • Client does not experience hyperventilation episodes.

    • Client can describe coping strategies for future anxiety episodes.

    • Family can support calmness during anxiety.

    • Engagement in supportive counseling or groups is noted.

Respiratory Acidosis

  • Directly related to hypoventilation leading to hypoxia.

  • Symptoms: Warm, flushed skin, headache, hyperkalemia, dysrhythmias, rapid shallow respirations, low blood pressure, confusion, dizziness, and muscle weakness.

Respiratory Acidosis - Definition

  • A condition characterized by pH less than 7.35 and PaCO2 greater than 45 mmHg, indicating carbonic acid excess.

  • Compensation occurs as kidneys conserve HCO3− and secrete H+ into the urine, typically taking 24 hours to adjust.

Respiratory Acidosis - Acute vs. Chronic

  • Acute Respiratory Acidosis: Sudden failure of ventilation leading to complex issues such as hypoxemia, intracranial pressure increases, and rapid pH decreases that threaten life.

  • Chronic Respiratory Acidosis: Associated with long-term respiratory or neuromuscular issues, where the respiratory system compensates over time, maintaining pH close to normal while being at risk for carbon dioxide narcosis.

Respiratory Acidosis - Risk Factors

  • Common conditions include:

    • Pneumonia

    • Chronic Obstructive Pulmonary Disease (COPD)

    • Asthma

    • Cystic Fibrosis

    • Multiple Sclerosis

    • Opioid overdose.

Respiratory Acidosis - Clinical Manifestations

  • Acute Symptoms: Headaches, elevated pulse, irritability, visual disturbances, altered LOC, risk of cardiac arrest.

  • Chronic Symptoms: Weakness, memory disturbances, sleep problems, personality alterations.

Respiratory Acidosis - Collaborative Care

  • Focus on treatments such as:

    • Bronchodilators, antibiotics for infection, narcotic antagonists, and respiratory support systems like pulmonary hygiene and ventilation support.

Respiratory Acidosis - Assessment

  • Health History: Review manifestations, duration, precipitating factors.

  • Physical Assessment: Assess mental status, LOC, vital signs, skin color, and respiratory patterns.

Respiratory Acidosis - Clinical Problems

  • Increase risk for:

    • Impaired gas exchange r/t ventilation-perfusion mismatch.

    • Activity intolerance from an imbalance between oxygen supply and demand.

    • Impaired memory due to hypoxia.

    • Risk for decreased cardiac perfusion due to dysrhythmias related to respiratory acidosis.

Respiratory Acidosis - Planning

  • Goals include:

    • Client maintains adequate fluid intake.

    • Client keeps oxygen saturation above 90%.

    • Client upholds balanced pH level and normal PaCO2 values.

Respiratory Acidosis - Implementation

  • Impaired Gas Exchange:

    • Evaluate and report ABG results timely.

    • Appropriate positioning of clients to enhance breathing, and administer oxygen.

  • Ineffective Airway Clearance:

    • Frequent assessment and encouragement of breathing exercises, positioning changes, and ambulation.

  • Anxiety Management:

    • Maintain proximity for client monitoring, explain procedures consistently, and reduce environmental stimuli.

  • Risk for Injury:

    • Regularly assess LOC and provide supportive safety measures including encouraging mobility while avoiding falls.

Respiratory Acidosis - Care in the Community

  • Emphasis on preventive strategies and educational outreach on measures to avert future respiratory crises. This could include immunizations, cautions with narcotics, and clear instructions around respiratory care.

Respiratory Acidosis - Evaluation

  • Goals include ensuring the following:

    • Client has a patent airway.

    • Client follows breathing routines fulfilling oxygen needs.

    • Client remains oriented without anxiety indicating potential hypoxia.

    • ABG reports indicate pH and PaCO2 are within acceptable ranges.

Acid-Base Imbalances and Nursing Interventions

  1. Acidosis:

    • Characterized by too much acid or too little base.

    • Respiratory acidosis - Increased PaCO2 due to decreased respiratory stimuli.

    • Metabolic acidosis - Decreased ability of kidneys to conserve base or excrete acid.

  2. Alkalosis:

    • Defined by too little acid or too much base.

    • Respiratory alkalosis - Decreased PaCO2 due to over-excretion of carbonic acid (hyperventilation).

    • Metabolic alkalosis - Increased bicarbonate or loss of acid due to causes like vomiting or diuretic use.

  3. Common Causes of Imbalances:

    • Acidosis Causes: Hyperkalemia, DKA (Diabetic Ketoacidosis), renal failure, shock, and severe diarrhea.

    • Alkalosis Causes: Overuse of antacids or baking soda, vomiting, and excessive diuretics.

  4. Clinical Manifestations:

    • Acidosis: Headaches, changes in LOC, hypoventilation, warm skin, flushed appearance.

    • Alkalosis: Decreased LOC, nausea, muscle tremors, hypokalemia.

  5. Body's Compensatory Mechanisms:

    • For acidosis, kidneys reabsorb more HCO3 and excrete carbonic acid.

    • For alkalosis, deep rapid breathing helps rid CO2.

  6. Treatment Protocols:

    • Acidosis entails bronchodilators, oxygen support, and monitoring.

    • Alkalosis may use sodium bicarbonate and treat underlying causes.

Interpretation of Arterial Blood Gases (ABGs)

  1. Examine each value by assessing:

    • pH: First factor to evaluate.

    • Determine if the imbalance is respiratory or metabolic using chosen methods.

    • Assess patient’s compensation capabilities to address the disorder.

Acid-Base Mnemonic - ROME

  • ROME: Respiratory Opposite (alkalosis = ↑pH, ↓PaCO2; acidosis = ↓pH, ↑PaCO2).

  • For Metabolic, it is Equal (alkalosis = ↑pH, ↑HCO3; acidosis = ↓pH, ↓HCO3).

Case Studies for Practice

  1. Case Study #1: 24-year-old with:

    • pH 7.25, PaCO2 60, PO2 65, HCO3 26. Determine acid-base status.

  2. Case Study #2: 60-year-old with:

    • pH 7.37, PaCO2 57, PO2 70, HCO3 32. Determine acid-base status.

  3. Case Study #3: 65-year-old with:

    • pH 7.45, PaCO2 49, PO2 68, HCO3 34. Determine acid-base status.

  4. Case Study #4: 47-year-old with:

    • pH 7.28, PaCO2 34, PO2 88, HCO3 16. Determine acid-base status.