CH 9 Acid-Base Balance

The nurse is caring for a client with severe diarrhea. The nurse monitors the client closely, understanding that this client is at risk for developing which acid-base disorder? 1. Metabolic acidosis 2. Metabolic alkalosis 3. Respiratory acidosis 4. Respiratory alkalosis

1 Rationale: Intestinal secretions high in bicarbonate may be lost through enteric drainage tubes, an ileostomy, or diarrhea. The decreased bicarbonate level creates the actual base deficit of metabolic acidosis. The remaining options are unlikely to occur in a client with severe diarrhea. Test-Taking Strategy: Focus on the subject, diarrhea. Knowing that this condition is a gastrointestinal disorder will direct you to think about a metabolic imbalance. Remembering that intestinal fluids are primarily alkaline will assist you with selecting the correct option. When excess bicarbonate is lost, acidosis will result.

Which clients would the nurse determine is at risk for development of metabolic alkalosis? Select all that apply. 1. Client with emphysema 2. Client who is hyperventilating 3. Client with chronic kidney disease 4. Client who has been vomiting for 2 days 5. Client receiving oral furosemide 40 mg daily 6. Client admitted with acetylsalicylic acid overdose

4, 5 Rationale: Metabolic alkalosis is caused by any condition that creates the acid-base imbalance through either an increase in bases or a deficit of acids, such as the client who has been vomiting for 2 days and the client receiving furosemide daily. Recall that clients with emphysema and hyperventilation are at risk for a respiratory acid-base disturbance. Chronic kidney disease and aspirin overdose will result in metabolic acidosis. Test-Taking Strategy: Focus on the subject, those at risk for metabolic alkalosis. Eliminate options that are comparable or alike and refer to respiratory conditions. From the remaining metabolic conditions, determine whether there is an increase in bases or a deficit in acids to answer correctly.

The nurse observes that a client with diabetic ketoacidosis is experiencing abnormally deep, regular, rapid respirations. How should the nurse correctly document this observation in the medical record? 1. Apnea 2. Bradypnea 3. Cheyne stokes 4. Kussmaul's respirations

4 Rationale: Abnormally deep, regular, and rapid respirations observed in the client with diabetic ketoacidosis are documented as Kussmaul's respirations. During apnea, respirations cease for several seconds. During bradypnea, respirations are regular but abnormally slow. Cheyne stokes respirations gradually become more shallow and are followed by periods of apnea (no breathing), with repetition of the pattern. Test-Taking Strategy: Knowledge regarding the description of alterations in breathing patterns is required to answer this question. Focus on options that are comparable or alike, such as apnea and Cheyne Stokes respirations, where there are periods of apnea to help you eliminate these two options. Next, note the client's diagnosis and remember that Kussmaul's respirations occur in clients with diabetic ketoacidosis.

A client has the following laboratory values: a pH of 7.55, an HCO3 level of 22 mEq/L (22 mmol/L), and a Pco2 of 30 mm Hg (30 mm Hg). Which action should the nurse plan to take? 1. Perform Allen's test. 2. Prepare the client for dialysis. 3. Administer insulin as prescribed. 4. Encourage the client to slow down breathing.

4 Rationale: The client is experiencing respiratory alkalosis based on the laboratory results of a high pH and a low Pco2 level. Interventions for respiratory alkalosis are the voluntary holding of breath or slowed breathing and the rebreathing of exhaled CO2 by methods such as using a paper bag or a rebreathing mask as prescribed. Performing Allen's test would be incorrect, because the blood specimen has already been drawn, and the laboratory results have been completed. Dialysis and insulin administration are interventions for metabolic acidosis. Test-Taking Strategy: Focus on the data in the question. Because the pH is high and the Pco2 level is low, a respiratory problem is occurring. Then, applying the ABCs—airway, breathing, and circulation—you can determine that only one intervention deals with respirations.

The nurse is told that the arterial blood gas (ABG) results indicate a pH of 7.50 and a Pco2 of 32 mm Hg (32 mm Hg). The nurse determines that these results are indicative of which acid-base disturbance? 1. Metabolic acidosis 2. Metabolic alkalosis 3. Respiratory acidosis 4. Respiratory alkalosis

4 Rationale: The normal pH is 7.35 to 7.45. If a respiratory condition exists, an opposite relationship will be seen between the pH and the Pco2, as is seen in the correct option. If an alkalotic condition exists, the pH is increased. During an acidotic condition, the pH is decreased so both metabolic acidosis and respiratory acidosis can be eliminated. Metabolic alkalosis can also be eliminated because both pH and HCO3 are increased above normal values with this condition. Test-Taking Strategy: Focus on the data in the question. Remember that with a respiratory condition, you will find an opposite relationship between the pH and the Pco2 level. Recalling that pH is increased in an alkalotic condition helps direct you to select respiratory alkalosis and eliminate respiratory acidosis. With metabolic conditions, pH and HCO3 are altered and either increase or decrease in the same direction.

Causes of Metabolic Acidosis

Diabetes mellitus or diabetic ketoacidosis ▪ Excessive ingestion of acetylsalicylic acid (aspirin) ▪ High-fat diet ▪ Insufficient metabolism of carbohydrates ▪ Malnutrition ▪ Renal insufficiency or failure ▪ Severe diarrhea

Causes of Metabolic Alkalosis

Diuretics ▪ Excessive vomiting or gastrointestinal suctioning ▪ Hyperaldosteronism ▪ Ingestion and/or infusion of excess sodium bicarbonate ▪ Massive transfusion of whole blood

Causes of Respiratory Alkalosis

Fever ▪ Hyperventilation ▪ Hypoxia ▪ Hysteria ▪ Overventilation by mechanical ventilators ▪ Pain

The nurse is caring for a client with a nasogastric tube that is attached to low suction. The nurse monitors the client closely for which acid-base disorder that is most likely to occur in this situation? 1. Metabolic acidosis 2. Metabolic alkalosis 3. Respiratory acidosis 4. Respiratory alkalosis

2 Rationale: The loss of gastric fluid via nasogastric suction or vomiting causes a metabolic condition. This also results in an alkalotic condition as a result of the loss of hydrochloric acid through gastrointestinal fluid losses. Also, the options denoting a respiratory problem—respiratory acidosis and alkalosis—can be easily eliminated. Test-Taking Strategy: Focus on the subject, nasogastric tube to low suction. Remember that hydrochloric acid is lost when the client is receiving nasogastric suctioning. This will direct you to the options that identify an alkalotic condition. Because the question addresses a situation other than a respiratory one, the acid-base disorder would be a metabolic condition.

A client is scheduled for blood to be drawn from the radial artery for an arterial blood gas (ABG) determination. The nurse assists with performing Allen's test before drawing the blood to determine the adequacy of which? 1. Ulnar circulation 2. Carotid circulation 3. Femoral circulation 4. Brachial circulation

1 Rationale: Before performing a radial puncture to obtain an arterial specimen for ABG values, Allen's test should be performed to determine adequate ulnar circulation. Failure to assess collateral circulation could result in severe ischemic injury to the hand if damage to the radial artery occurs with arterial puncture. The remaining options are not associated with this test. Test-Taking Strategy: Focus on the subject, radial artery puncture and the purpose of Allen's test. Visualize the location of each of the vessels in the options. First, eliminate carotid and femoral circulations, realizing their distance from the radial artery. From the remaining options, select the ulnar artery, realizing it runs parallel to the radial artery and supplies blood flow to the hand.

The nurse is caring for a client with respiratory insufficiency. The arterial blood gas (ABG) results indicate a pH of 7.50 and a Pco2 of 30 mm Hg (30 mm Hg), and the nurse is told that the client is experiencing respiratory alkalosis. Which additional laboratory value should the nurse expect to note? 1. A sodium level of 145 mEq/L (145 mmol/L) 2. A potassium level of 3.0 mEq/L (3.0 mmol/L) 3. A magnesium level of 1.3 mEq/L (0.65 mmol/L) 4. A phosphorus level of 3.0 mg/dL (0.97 mmol/L)

2 Rationale: Signs/symptoms of respiratory alkalosis include tachypnea, change in mental status, dizziness, pallor around the mouth, spasms of the muscles of the hands, and hypokalemia. The remaining options identify normal laboratory results. Test-Taking Strategy: Recalling the clinical manifestations of respiratory alkalosis and the normal laboratory values will assist you with answering this question. Eliminate options that are comparable or alike in that they reflect normal laboratory values. You can then determine that the only abnormal laboratory value is the potassium level.

The nurse is caring for a client with a diagnosis of chronic obstructive pulmonary disease (COPD). The nurse should monitor the client for which acid-base imbalance? 1. Metabolic acidosis 2. Metabolic alkalosis 3. Respiratory acidosis 4. Respiratory alkalosis

3 Rationale: Respiratory acidosis most often occurs as a result of primary defects in the function of the lungs or changes in normal respiratory patterns from secondary problems. Chronic respiratory acidosis is most commonly caused by chronic obstructive pulmonary disease (COPD). Acute respiratory acidosis also occurs in clients with COPD when superimposed respiratory infection or concurrent respiratory disease increases the work of breathing. The remaining options are not likely to occur unless other conditions complicate the COPD. Test-Taking Strategy: Focus on the subject, COPD, to assist with guiding you to select a respiratory acid-base balance. Then remembering that primary defects in the function of the lungs result in respiratory acidosis will direct you to the correct option.

The registered nurse (RN) reviews the results of the arterial blood gas (ABG) values with the licensed practical nurse (LPN) and tells the LPN that the client is experiencing respiratory acidosis. The LPN should expect to note which on the laboratory result report? 1. pH 7.50, Pco2 52 mm Hg 2. pH 7.35, Pco2 40 mm Hg 3. pH 7.25, Pco2 50 mm Hg 4. pH 7.50, Pco2 30 mm Hg

3 Rationale: The normal pH is 7.35 to 7.45, and the normal Pco2 value is 35 mm Hg to 45 mm Hg (35 to 45 mm Hg). In respiratory acidosis, the pH is down, and the Pco2 is up. Therefore, the pH of 7.25 and the Pco2 of 50 mm Hg (50 mm Hg) option is the only one that reflects an acidotic condition. Options with an elevated pH (options 1 and 4) indicate an alkalotic condition. Option 2 identifies normal values for pH and Pco2. Test-Taking Strategy: Focus on the subject, respiratory acidosis. Remember that with a respiratory imbalance, you will find an opposite relationship between the pH and the Pco2 value. In addition, remember that the pH is down in an acidotic condition.

Causes of Respiratory Acidosis

Asthma ▪ Atelectasis ▪ Brain trauma ▪ Bronchiectasis ▪ Bronchitis ▪ Central nervous system depressants ▪ Emphysema ▪ Hypoventilation ▪ Pneumonia ▪ Pulmonary edema ▪ Pulmonary emboli