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Course: Fundamentals of Nursing�Topic: Acid Base Imbalance

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Module Goals

Learners will be able to:

Identify key components of acid-base balance.
Recognize normal acid-base values.
Interpret arterial blood gas draw results.
Apply acid-base knowledge to nursing practice.

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Arterial Blood Gases

Blood draw from artery

Commonly drawn from radial artery.

Measures

pH in the blood.
Partial pressure of arterial oxygen (PaO2).
Partial pressure of arterial carbon dioxide (PaCO2).
Bicarbonate level (HCO3).
Oxygen saturation (SaO2).

Determines the status of the acid-base balance of client.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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Blood pH

Scale of 0-14 and used to determine the bloods acidity or alkalinity.
pH values

Neutral: 7
Normal range: 7.35-7.45
Low pH, less than 7.35: acidic, high hydrogen ion concentration
High pH, more than 7.45: alkaline, low hydrogen ion concentration

Hydrogen ion values are produced through metabolism and the goal is to have these values balanced within normal pH range.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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Lungs and Kidneys

Lungs and kidneys help maintain pH.
Acidosis:

Respiratory rate increases eliminating acid in carbon dioxide.
Kidneys retain bicarbonate (a base) and eliminates hydrogen ions in urine.

Alkalosis:

Respiratory rate decreases to hold in carbon dioxide (acid).
Kidneys excrete bicarbonate (base) and retain hydrogen ions.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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PaCO₂

Normal value: 35-45.
Carbon dioxide (acid) is regulated by lungs.

Done through altering the rate of respirations or depth of respirations.

Increased respiratory rate and depth:

Excess CO₂ is removed therefore decreasing hydrogen ions in blood and increased pH, making the blood more alkaline.

Decreased respiratory rate and depth:

Less CO₂ is removed, increasing hydrogen ions in the blood and decreased pH, making blood more acidic.

Quick revisions from lungs and ventilation.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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HCO₃

Normal range: 22-26.
Bicarbonate levels regulated by the kidneys and make the blood become more alkaline.
Longer adjustment time period for correction and is not physically visible.
Kidneys retain or excrete HCO₃ depending on the need.

Retains HCO₃ if pH is acidic.
Excretes HCO, if pH is alkalotic.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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PaO₂ and Arterial Blood Gas Draw

More accurate measurement of oxygenation status of client than pulse oximetry.
Arterial blood gas draw most accurate in assessing clients in respiratory distress.
Knowing critical values of arterial blood gas draw is imperative in knowing client status.
Critical values of arterial blood gas draws can indicate serious adverse reactions, including death.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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Review

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Arterial Blood Gas (ABG) Draw Interpretation

Interpreting ABGs can identify the source of the acid-base imbalance, the targeted interventions, and the effectiveness of the interventions.
Interpreted as:

Respiratory acidosis
Respiratory alkalosis
Metabolic acidosis
Metabolic alkalosis

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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ROME Interpretation Method

ROME: Respiratory Opposite Metabolic Equal.
Respiratory component: PaCO₂.
Metabolic component: HCO₃.
Compare the pH reading with the PaCO₂ and HCO₃ to determine origin of imbalance.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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Case Study

The nurse receives the arterial blood gas results as followed. Determine the ABG interpretation:

pH: 7.29
PaCO₂: 28
HCO₃: 25

Determine if the pH is showing alkalosis or acidosis.
Determine what value (PaCO₂ or HCO₃) is out of normal range.
Compare the abnormal value to the pH. Are they both low? Are they both high? Are they opposite (one high/one low)?
If they are both high or low, it is Metabolic. If they are opposite, it is Respiratory.
Identification would be either Metabolic or Respiratory, and then evaluation of pH (acidosis or alkalosis).
Answer located in notes below.

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Respiratory Acidosis

Buildup of CO₂ in body -- also known as hypercapnia -- increasing blood acidity.
pH is low, PaCO₂ is greater than 45.
Potential causes:

Decreased exchange of oxygen and carbon dioxide at alveolar level.
Examples: Pulmonary edema, chronic obstructive pulmonary disease (COPD), acute asthma exacerbation, decreased ventilation related to anesthesia, alcohol use, or medications (opioids or sedatives).

Assess for signs of hypercapnia:

Mild: anxiety, dyspnea, headache.
Higher levels: delirium, paranoia, confusion.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

clients with chronic diseases, who stay in prolonged periods of respiratory acidosis, generally have compensated balances by the kidneys keeping in HCO3. If the client has chronic respiratory acidosis, the body has time to adapt, unlike acute phases. In acute phases, ventilation decreases by having slower breathing and shallower breaths, increasing the levels of PaCO2 and decreasing levels of CO2.

In normal lung functioning clients, a decrease of consciousness is typically seen with levels of PaCO2 greater than 75. For clients with chronic hypercapnia, these symptoms may not appear until the levels reach above 90.

Nursing assessment for a client exhibiting respiratory acidosis:

Assess airway, breathing, circulation (ABC)
If the client is showing signs of respiratory distress, assistance should be sought quickly.
Interpretation of an ABG will dictate interventions for the client.

Typical treatments:

Goal: improving ventilation to remove carbon dioxide, increase respiration depth, and oxygenate the client
decreasing sedation
giving nebulizer treatments
use of a BiPAP or CPAP machine
remove airway restrictions
If above treatments do not work, the client will typically be intubated and the use of mechanical ventilation is utilized.

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Respiratory Alkalosis

Occurs when too much CO₂ leaves the body through respiration.

Increases pH of blood.
Seen as ABG result of high pH (greater than 7.45) and low PaCO₂ (less than 35).

Potential causes:

Hyperventilation (anxiety, fear, mechanical ventilation settings, pain, head injury).
Overdoses initially send body to respiratory alkalosis prior to metabolic acidosis.

Assess for signs of respiratory alkalosis:

Dizziness, shortness of breath, chest pain, chest tightness, palpitations, paresthesias.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

Respiratory alkalosis is not fatal, but should be recognized because certain causes of the body going into respiratory alkalosis can cause serious complications or death if left untreated. Examples of this are acute asthma exacerbations and a pulmonary embolism.

Typical treatments:

Main goal: treating underlying cause of why the client is in respiratory alkalosis
If the client is hyperventilating: reassure client, have client describe symptoms, slow breathing down through breathing retraining.

Breathing retraining is instructing the client to focus on abdominal breathing. This is also known as diaphragmatic breathing. This is done by having the client either sit or lay supine while they place one hand (if able) on their abdomen, and the other on their chest. As they are breathing, ask the client to take note of what hand is moving greater. If the client is hyperventilating, a typical response is that the hand on the chest is moving greater than the one on the abdomen. Instruct the client to focus on their breaths with the goal of adjusting their breathing to allow the hand on the abdomen to move greater and so that the hand on the chest barely moves.
Additional breathing techniques include having the client take a deep, slow breath (if able) for four seconds, then hold their breath momentarily, then breathe the breath out for eight seconds. After repeating this five to ten times, the client should have a reduction in their anxiety and hyperventilation.

After noninvasive treatment techniques, the client may be prescribed a short-acting benzodiazepine such as lorazepam if severe symptoms persist.

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Metabolic Acidosis

Occurs when the body has an excessive amount of hydrogen ions and not enough HCO₃

Seen as ABG result of pH of below 7.35 and HCO₃ below 22

May result from kidney dysfunction

Typically, the kidneys are able to rid acids through excretion of urine and neutralize acids through HCO₃ reabsorption

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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Metabolic Acidosis

Potential causes:

Diabetic ketoacidosis.
Lactic acidosis secondary to impaired tissue oxygenation.
Severe diarrhea.

Assess for signs and symptoms of metabolic acidosis:

Increased, rapid respiration rates, confusion, delirium, hypotension, decreased level of consciousness, electrolyte imbalances, death.

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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Metabolic Alkalosis

Occurs when excessive loss of hydrogen ions or retaining too much bicarbonate

Seen as ABG result of pH greater than 7.45 and HCO₃ greater than 26

Potential causes:

Excessive urination, high levels of bicarbonate, hydrogen ions moving into the cells from bloodstream
Diuretics
IV solutions of sodium bicarbonate given to client
Hypokalemia

Assess for signs and symptoms of metabolic alkalosis:

Decreased respiratory rate, exhibiting confusion, hypotension, cardiac dysfunction

Ernstmeyer & Christman, 2021

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Analyzing ABG Results Review

Ernstmeyer & Christman, 2021

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Analyzing ABG Results Review

(Ernstmeyer & Christman, 2021)

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Nursing Application

Assess client frequently and comprehensively to look for any changes of status.
Understand client’s past medical history to identify risk factors that may attribute to potential acid-base imbalances.

Examples: diabetic, kidney disease, asthma.

Analyze vital signs, trends, and any changes.
Track inputs and outputs and identify any changes of trends.
Identify any changes during auscultation of heart for cardiac changes
Complete neurology checks.

Is the client newly confused? Is there a decrease of consciousness that is new?

Ernstmeyer & Christman, 2021

Contact info: info@nursesinternational.org

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What would the nurse do?

As the nurse was completing their rounds, they find their client, in their room coughing with audible wheezing. The client is displaying signs of confusion and states they have a headache.

With the knowledge that the client was admitted to the unit for management of newly diagnosed asthma. What condition does the nurse suspect and what should the nurse do?

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References:

Ernstmeyer, K., & Christman, E. (Eds.). (2021). Open RN Nursing Fundamentals. By Chippewa Valley Technical College, licensed under CC BY 4.0. https://wtcs.pressbooks.pub/nursingfundamentals/open/download?type=pdf

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