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Acid-Base Imbalances Unit 6 chapter 50 Nursing care of clients with Fluid/Electrolyte/ Acid-Base imbalances Chapter 50 Acid-Base Imbalances Overview ●● For cells to function optimally, metabolic processes must maintain a steady balance between the acids and bases found in the body. ◯◯ ◯◯ ●● Acid-base balance represents homeostasis of hydrogen (H+) ion concentration in body fluids. Hydrogen shifts between the extracellular and intracellular compartments to compensate for acid-base imbalances. Minor changes in hydrogen concentration have major effects on normal cellular function. Arterial pH is an indirect measurement of hydrogen ion concentration and is a result of respiratory and renal compensational function. Arterial blood gases (ABGs) are most commonly used to evaluate acid-base balance. ◯◯ 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. ■■ ■■ The greater the concentration of hydrogen, the more acidic the body fluids and the lower the pH. The lower the concentration of hydrogen, the more alkaline the body fluids and the higher the pH. Maintenance of Acid-Base Balance ●● Acid-base balance is maintained by chemical, respiratory, and renal processes. ◯◯ ◯◯ Chemical and protein buffers: ■■ Are the first line of defense. ■■ Either bind or release hydrogen ions as needed. ■■ Respond quickly to changes in pH. Respiratory buffers: ■■ Are the second line of defense. ■■ Control the level of hydrogen ions in the blood through the control of CO2 levels. ■■ When a chemoreceptor senses a change in the level of CO2, a signal is sent to the brain to alter the rate and depth of respirations. ☐☐ Hyperventilation = decrease in hydrogen ions ☐☐ Hypoventilation = increase in hydrogen ions 586Rn adult medical surgical nursing acid-base imbalances ◯◯ Renal buffers: ■■ ■■ ■■ ■■ ●● ◯◯ ●● This buffering system is much slower to respond, but it is the most effective buffering system with the longest duration. The kidneys control the movement of bicarbonate in the urine. Bicarbonate can be reabsorbed into the bloodstream or excreted in the urine in response to blood levels of hydrogen. The kidneys may also produce more bicarbonate when needed. ☐☐ High hydrogen ions = bicarbonate reabsorption and production ☐☐ Low hydrogen ions = bicarbonate excretion Compensation refers to the process by which the body attempts to correct changes and imbalances in pH levels. ◯◯ ●● The kidneys are the third line of defense. Full compensation occurs when the pH level of the blood returns to normal (7.35 to 7.45). If the pH level is not able to normalize, then it is referred to as partial compensation. Metabolic alkalosis, metabolic acidosis, respiratory alkalosis, and respiratory acidosis are examples of acid-base imbalances. Acid-base imbalances are a result of insufficient compensation. Respiratory and renal function plays a large role in the body’s ability to effectively compensate for acid-base alterations. Organ dysfunction negatively affects acid-base compensation. 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. Rn adult medical surgical nursing 58 7 Acid-base imbalances Assessment ●● Risk Factors/Causes of Acid-Base Imbalances Respiratory Acidosis–Hypoventilation Respiratory acidosis results from: • Respiratory depression from poisons, anesthetics, trauma, or neurological diseases (myasthenia gravis, Guillain-Barré). • Inadequate chest expansion due to muscle weakness, pneumothorax/hemothorax, flail chest, obesity, tumors, or deformities. • Airway obstruction that occurs in laryngospasm, asthma, and some cancers. • Alveolar-capillary blockage secondary to a pulmonary embolus, thrombus, cancer, or pulmonary edema. • Inadequate mechanical ventilation. Respiratory acidosis results in: • Increased CO2. • Increased H+ concentration. Metabolic Acidosis Metabolic acidosis results from: • Excess production of hydrogen ions ◯◯ DKA ◯◯ Lactic acidosis ◯◯ Starvation ◯◯ Heavy exercise ◯◯ Seizure activity ◯◯ Fever ◯◯ Hypoxia ◯◯ Intoxication with ethanol or salicylates • Inadequate elimination of hydrogen ions ◯◯ Renal failure • Inadequate production of bicarbonate ◯◯ Renal failure ◯◯ Pancreatitis ◯◯ Liver failure ◯◯ Dehydration • Excess elimination of bicarbonate ◯◯ Diarrhea, ileostomy Metabolic acidosis results in: • Decreased HCO3-. • Increased H+ concentration. Respiratory Alkalosis–Hyperventilation Respiratory alkalosis results from: • Hyperventilation due to fear, anxiety, intracerebral trauma, salicylate toxicity, or excessive mechanical ventilation. • Hypoxemia from asphyxiation, high altitudes, shock, or early-stage asthma or pneumonia. Respiratory alkalosis results in: • Decreased CO2. • Decreased H+ concentration. Metabolic Alkalosis Metabolic alkalosis results from: • Base excess ◯◯ Oral ingestion of bases (antacids) ◯◯ Venous administration of bases (blood transfusions, TPN, or sodium bicarbonate) • Acid deficit ◯◯ Loss of gastric secretions (through prolonged vomiting, NG suction) ◯◯ Potassium depletion (due to thiazide diuretics, laxative abuse, Cushing’s syndrome) Metabolic alkalosis results in: • Increased HCO3-. • Decreased H+ concentration. 588Rn adult medical surgical nursing acid-base imbalances ●● Subjective and Objective Data Respiratory Acidosis–Hypoventilation Respiratory Alkalosis–Hyperventilation • Vital signs: Tachycardia (severe acidosis may lead to bradycardia), tachypnea • Dysrhythmias • Neurological: Anxiety, irritability, confusion, coma • Respiratory: Ineffective, shallow, rapid breathing • Skin: Pale or cyanotic • Vital Signs: Tachypnea • Neurological: Anxiety, tetany, convulsions, tingling, numbness • CV: Palpitations, chest pain, dysrhythmias • Respiratory: Rapid, deep respirations Metabolic Acidosis Metabolic Alkalosis • Vital Signs: Bradycardia, weak peripheral pulses, hypotension, tachypnea • Dysrhythmias • Neurological: Muscle weakness, hyporeflexia, flaccid paralysis, fatigue, confusion • Respiratory: Rapid, deep respirations (Kussmaul respirations) • Skin: Warm, dry, flushed ◯◯ • Vital Signs: Tachycardia, normotensive or hypotensive • Dysrhythmias • Neurological: Numbness, tingling, tetany, muscle weakness, hyperreflexia, confusion, convulsion • Respiratory: Depressed skeletal muscles resulting in ineffective breathing Laboratory Tests and Diagnostic Procedures ■■ To determine the type of imbalance, follow these steps: Step 1: Look at pH. If < 7.35, diagnose as acidosis. If > 7.45, diagnose as alkalosis. Step 2: Look at PaCO2 and HCO3- simultaneously. Determine which is in the normal range. Conclude that the other is the indicator of imbalance. Diagnose < 35 or > 45 PaCO2 as respiratory in origin. Diagnose < 22 or > 26 HCO3- as metabolic in origin. Step 3: Combine diagnoses of Steps 1 and 2 to name the type of imbalance Step 4: Evaluate the PaO2 and the SaO2. If the results are below the normal range, the client is hypoxic. Rn adult medical surgical nursing 58 9 Acid-base imbalances Step 5: Determine compensation as follows: Uncompensated: The pH will be abnormal and either the HCO3- or the PaCO2 will be abnormal. Partially compensated: The pH, HCO3-, and PaCO2 will be abnormal. Fully compensated: The pH will be normal, but the PaCO2 and HCO3- will both be abnormal. Looking back at the pH will provide a clue as to which system initiated the problem, respiratory or metabolic. If the pH is < 7.40, think “acidosis” and determine which system has the acidosis value. If the pH is > 7.40, think “alkalosis” and determine which system has the alkalosis value. ■■ The following are the five classic types of ABG results demonstrating balance and imbalance. Step 1 Step 2 Step 3 If Determine which is in normal range Combine names pH PaCO2 HCO3 Diagnosis 7.35-7.45 35-45 22-26 Homeostasis < 7.35 > 45 22-26 Respiratory acidosis < 7.35 35-45 < 22 Metabolic acidosis > 7.45 < 35 22-26 Respiratory alkalosis > 7.45 35-45 > 26 Metabolic alkalosis - Collaborative Care ●● Nursing Care ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ●● For all acid-base imbalances, it is imperative to treat the underlying cause. Respiratory acidosis: Oxygen therapy, maintain patent airway, and enhance gas exchange (positioning and breathing techniques, ventilatory support, bronchodilators, mucolytics). Respiratory alkalosis: Oxygen therapy, anxiety reduction interventions, and rebreathing techniques. Metabolic acidosis: Varies with causes (if DKA, administer insulin; if related to GI losses, administer antidiarrheals and provide rehydration; if serum bicarbonate is low, administer sodium bicarbonate [1 mEq/kg]). Metabolic alkalosis: Varies with causes (if GI losses, administer antiemetics, fluids, and electrolyte replacements; if related to potassium depletion, discontinue causative agent). Interdisciplinary Care ◯◯ Respiratory services can be consulted for oxygen therapy, breathing treatments, and ABGs. ◯◯ Pulmonology services can be consulted for respiratory management. 590Rn adult medical surgical nursing acid-base imbalances ●● Care after Discharge ◯◯ Client Education ■■ ■■ ■■ ■■ ■■ ◯◯ ●● Education may vary in relation to the client’s condition. Encourage adherence to the prescribed diet and dialysis regimen for clients who have kidney dysfunction. Encourage the client to weigh self daily and notify the provider if there is a 1 to 2 lb gain in 24 hr or a 3 lb gain in 1 week. Promote smoking cessation if the client is a smoker. Teach the client to take medication as prescribed. Encourage adherence to the medication regimen for clients who have COPD. Set up referral services (home oxygen). Client Outcomes ◯◯ The client will be free from anxiety. ◯◯ The client will maintain an adequate gas exchange. ◯◯ The client will have arterial blood gas results within the expected reference range. Complications ●● Convulsions, Coma, and Respiratory Arrest ◯◯ These are potential complications of acid-base imbalances. ◯◯ Nursing Actions ■■ ■■ Implement seizure precautions and perform management interventions if necessary. Provide life-support interventions if necessary. Rn adult medical surgical nursing 59 1 Acid-base imbalances Chapter 50: Acid-Base Imbalances Application Exercises 1. Interpret each of the following ABG results. Possible interpretations: Respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis, partially compensated metabolic acidosis, partially compensated metabolic alkalosis, partially compensated respiratory acidosis, partially compensated respiratory alkalosis, normal. pH 7.28 PaCO2 56 mm Hg HCO3- 25 mEq/L SaO2 89% Interpretation: pH 7.49 PaCO2 30 mm Hg HCO3- 23 mEq/L SaO2 96% Interpretation: pH 7.28 PaCO2 43 mm Hg HCO3- 18 mEq/L SaO2 96% Interpretation: pH 7.40 PaCO2 40 mm Hg HCO3- 24 mEq/L SaO2 98% Interpretation: pH 7.50 PaCO2 36 mm Hg HCO3- 27 mEq/L SaO2 97% Interpretation: pH 7.33 PaCO2 29 mm Hg HCO3- 16 mEq/L SaO2 95% Interpretation: pH 7.35 PaCO2 42 mm Hg HCO3- 26 mEq/LSaO2 95% Interpretation: pH 7.12 PaCO2 60 mm Hg HCO3- 29 mEq/ SaO2 94% Interpretation: pH 7.48 PaCO2 33 mm Hg HCO3- 24 mEq/L SaO2 96% Interpretation: pH 7.58 PaCO2 47 mm Hg HCO3- 30 mEq/L SaO2 95% Interpretation: pH 7.36 PaCO2 44 mm Hg HCO3- 24 mEq/LSaO2 98% Interpretation: pH 7.30 PaCO2 59 mm Hg HCO3- 38 mEq/L SaO2 94% Interpretation: 592Rn adult medical surgical nursing acid-base imbalances 2. A young adult female client who has a history of depression is admitted with confusion and lethargy. She was found at home with an empty bottle of aspirin next to her in the bed. Vital signs reveal a blood pressure of 104/72 mm Hg, pulse rate of 116 beats/min with a regular rhythm, and a respiratory rate of 42/min and deep. Which of the following arterial blood gas results should the nurse expect? A. pH 7.38, PaO2 96 mm Hg, PaCO2 38 mm Hg, HCO3- 24 mEq/L B. pH 7.48, PaO2 100 mm Hg, PaCO2 28 mm Hg, HCO3- 23 mEq/L C. pH 6.98, PaO2 100 mm Hg, PaCO2 30 mm Hg, HCO3- 18 mEq/L D. pH 7.58, PaO2 96 mm Hg, PaCO2 38 mm Hg, HCO3- 29 mEq/L 3. An adult male client was involved in a single-vehicle car crash. He is reporting chest pain and difficulty breathing, A chest x-ray reveals a pneumothorax and blood gas analysis is obtained. Which of the following results should the nurse expect? A. pH 7.06, PaO2 86 mm Hg, PaCO2 52 mm Hg, HCO3- 24 mEq/L B. pH 7.42, PaO2 100 mm Hg, PaCO2 38 mm Hg, HCO3- 23 mEq/L C. pH 6.98, PaO2 100 mm Hg, PaCO2 30 mm Hg, HCO3- 18 mEq/L D. pH 7.58, PaO2 96 mm Hg, PaCO2 38 mm Hg, HCO3- 29 mEq/L 4. A client is in the first trimester of pregnancy. She has experienced approximately 1 week of severe nausea with frequent vomiting. Which of the following conditions should the nurse expect to find if an arterial blood gas is analyzed? A. Respiratory acidosis B. Respiratory alkalosis C. Metabolic acidosis D. Metabolic alkalosis Rn adult medical surgical nursing 59 3 Acid-base imbalances Chapter 50: Acid-Base Imbalances Application Exercises Answer Key 1. Interpret each of the following ABG results. Possible interpretations: Respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis, partially compensated metabolic acidosis, partially compensated metabolic alkalosis, partially compensated respiratory acidosis, partially compensated respiratory alkalosis, normal. pH 7.28 PaCO2 56 mm Hg HCO3- 25 mEq/L SaO2 89% Interpretation: Respiratory acidosis pH 7.49 PaCO2 30 mm Hg HCO3- 23 mEq/L SaO2 96% Interpretation: Respiratory alkalosis pH 7.28 PaCO2 43 mm Hg HCO3- 18 mEq/L SaO2 96% Interpretation: Metabolic acidosis pH 7.40 PaCO2 40 mm Hg HCO3- 24 mEq/L SaO2 98% Interpretation: Normal pH 7.50 PaCO2 36 mm Hg HCO3- 27 mEq/L SaO2 97% Interpretation: Metabolic alkalosis pH 7.33 PaCO2 29 mm Hg HCO3- 16 mEq/L SaO2 95% Interpretation: Partially compensated metabolic acidosis pH 7.35 PaCO2 42 mm Hg HCO3- 26 mEq/LSaO2 95% Interpretation: Normal pH 7.12 PaCO2 60 mm Hg HCO3- 29 mEq/L SaO2 94% Interpretation: Partially compensated respiratory acidosis pH 7.48 PaCO2 33 mm Hg HCO3- 24 mEq/L SaO2 96% Interpretation: Respiratory alkalosis pH 7.58 PaCO2 47 mm Hg HCO3- 30 mEq/L SaO2 95% Interpretation: Partially compensated metabolic alkalosis pH 7.36 PaCO2 44 mm Hg HCO3- 24 mEq/LSaO2 98% Interpretation: Normal pH 7.30 PaCO2 59 mm Hg HCO3- 38 mEq/L SaO2 94% Interpretation: Partially compensated respiratory acidosis NCLEX® Connection: Reduction of Risk Potential, Laboratory Values 594Rn adult medical surgical nursing acid-base imbalances 2. A young adult female client who has a history of depression is admitted with confusion and lethargy. She was found at home with an empty bottle of aspirin next to her in the bed. Vital signs reveal a blood pressure of 104/72 mm Hg, pulse rate of 116 beats/min with a regular rhythm, and a respiratory rate of 42/min and deep. Which of the following arterial blood gas results should the nurse expect? A. pH 7.38, PaO2 96 mm Hg, PaCO2 38 mm Hg, HCO3- 24 mEq/L B. pH 7.48, PaO2 100 mm Hg, PaCO2 28 mm Hg, HCO3- 23 mEq/L C. pH 6.98, PaO2 100 mm Hg, PaCO2 30 mm Hg, HCO3- 18 mEq/L D. pH 7.58, PaO2 96 mm Hg, PaCO2 38 mm Hg, HCO3- 29 mEq/L An aspirin overdose would result in metabolic acidosis. Metabolic alkalosis, respiratory acidosis, and respiratory alkalosis would not be indicated in the client. NCLEX® Connection: Reduction of Risk Potential, Laboratory Values 3. An adult male client was involved in a single-vehicle car crash. He is reporting chest pain and difficulty breathing, A chest x-ray reveals a pneumothorax and blood gas analysis is obtained. Which of the following results should the nurse expect? A. pH 7.06, PaO2 86 mm Hg, PaCO2 52 mm Hg, HCO3- 24 mEq/L B. pH 7.42, PaO2 100 mm Hg, PaCO2 38 mm Hg, HCO3- 23 mEq/L C. pH 6.98, PaO2 100 mm Hg, PaCO2 30 mm Hg, HCO3- 18 mEq/L D. pH 7.58, PaO2 96 mm Hg, PaCO2 38 mm Hg, HCO3- 29 mEq/L Pneumothorax can cause alveolar hypoventilation and increased carbon dioxide levels, resulting in a state of respiratory acidosis. Respiratory alkalosis, metabolic alkalosis, and metabolic acidosis would not be indicated in the client. NCLEX® Connection: Reduction of Risk Potential, Laboratory Values 4. A client is in the first trimester of pregnancy. She has experienced approximately 1 week of severe nausea with frequent vomiting. Which of the following conditions should the nurse expect to find if an arterial blood gas is analyzed? A. Respiratory acidosis B. Respiratory alkalosis C. Metabolic acidosis D. Metabolic alkalosis Excessive vomiting causes a loss of gastric acids and an accumulation of bicarbonate in the blood, resulting in metabolic alkalosis. Respiratory acidosis, respiratory alkalosis, and metabolic acidosis would not be indicated in the client. NCLEX® Connection: Reduction of Risk Potential, Laboratory Values Rn adult medical surgical nursing 59 5
