Chapter 9: Altered Acid-Base Balance

A newly admitted client's diagnostic testing indicates metabolic acidosis. What action should the nurse take when working to determine the cause?

Assess the client's blood glucose levels -Hyperglycemia can result in diabetic ketoacidosis, a form of metabolic acidosis. Changes in respiratory status would result in acid-base disorders of the respiratory, not metabolic, type. The presence of fecal occult blood and disruptions to the pupillary reflex are not likely to result in metabolic acidosis.

The nurse recognizes the role of the lungs in acid-base balance is regulation of which of the following?

Carbon dioxide (CO2) is regulated by the lungs. HCO3 and H+ are regulated by kidneys.

A client is admitted after losing 44 lb (20 kg) over the past 3 months, largely due to frequent vomiting. What intervention should the nurse anticipate in the treatment of the client's resulting acid-base imbalance?

Fluid replacement with an intravenous solution containing electrolytes as prescribed -Vomiting ultimately results in the increase in pH that constitutes metabolic alkalosis; intravenous potassium chloride (KCl) solutions are a mainstay of treatment for this acid-base imbalance. Respiratory interventions will not have an appreciable effect because of the metabolic nature of the imbalance. Sodium bicarbonate would exacerbate the client's condition.

The nurse is aware that the major role of the kidneys in regulating acid-base balance is to increase the production of which chemical component?

HCO3- -The kidneys play a critical role in maintaining acid-base balance. They accomplish this through the reabsorption of HCO3-, regulation of H+ secretion, and generation of new HCO3-. The hydrogen/bicarbonate exchange system regulates pH through the secretion of excess H+ and reabsorption of HCO3- by the renal tubules. Bicarbonate is freely filtered in the glomerulus and reabsorbed or reclaimed in the tubules. Each HCO3- that is reclaimed requires the secretion of an H+. H2CO3 is a weak acid. HCl is found in gastric fluid. The kidneys would eliminate, not increase, production of H ion.

A middle-aged woman has presented to the emergency department following a panic attack. Her blood pressure, respiratory rate, and heart rate are all highly elevated, while her temperature and oxygen saturation are within normal ranges. What is the woman's body most likely doing to address the changes in pH associated with her situation?

Her kidneys will limit the amount of bicarbonate that they reabsorb. -Renal compensation for respiratory alkalosis involves decreased bicarbonate reabsorption. Manipulation of Cl- ions is not a compensatory mechanism that the body is capable of, and increased CO2 levels and decreased H+ would compensate for her acid-base imbalance.

Respiratory alkalosis can be caused by a respiratory rate in excess of that which maintains normal plasma PCO2 levels. What is a common cause of respiratory alkalosis?

Hyperventilation -One of the most common causes of respiratory alkalosis is hyperventilation, which is characterized by episodes of overbreathing, often associated with anxiety.

Which arterial blood gas (ABG) values tell the nurse a client is in respiratory alkalosis? Select all that apply.

PCO2 of 27mm Hg (3.59 kPa) pH 7.52 -ABGs measure pH, carbon dioxide (PCO2), bicarbonate ion (HCO3-), oxygen PO2, base excess, and the anion gap. A pH that is below 7.35 is considered acidic while above 7.45 is considered alkaline. The PCO2 is considered the primary indicator of respiratory function. Elevation above 45mm Hg indicates acidosis while a decrease below 35mm Hg indicates alkalosis. Bicarbonate (HCO3-) is the primary indicator of metabolic function and is considered alkaline if greater than 26 mEq/L, and acidic if below 22 mEq/L. Base excess measures the level of all the buffer systems in the blood. If the level is more than 0.2 mEq/L above the normal pH of 7.4 it is considered an excess and indicates metabolic alkalosis. Anion gap indicates the difference between plasma concentration of the major measured cation (sodium) and the sum of the measured anions (chloride and bicarbonate). This level rises in conditions of acidosis. Anion gap and base excess or deficit are used primarily to indicate metabolic acid-base disorders.

The condition of a client with metabolic acidosis from an intestinal fistula is not improving. The pulse is 125 beats/min and the BP 84/56 mm Hg. ABG values are: pH 7.1, HCO3- 18 mEq/L (18 mmol/L), PCO2 57 mm Hg (7.58 kPa). What IV medication should the nurse expect to provide next?

Sodium bicarbonate -When a client with acidosis has the pH drop to 7.1 to 7.2 there is a decrease in cardiac contractility and output. The heart is less responsive to catecholamines, and fatal ventricular dysrhythmias may occur. Sodium bicarbonate (NaHCO3) is used to partially correct the acidosis in this type of normal anion gap condition. This improves cardiovascular responsiveness. Antibiotics would be used for sepsis. Potassium would not be appropriate because levels are already elevated in acidosis.

The nurse is evaluating a client's blood gases. The client has a pH of 7.35. How does the nurse interpret this value?

It is within a normal range. -The normal body range of pH is 7.35 to 7.45. The other answers are incorrect. An acidotic value would be indicated by a pH less than 7.35 and an alkalotic level would be indicated by a pH greater than 7.45.

A nurse is providing care for several clients on an acute medicine unit. Which client should the nurse recognize as being at the highest risk for metabolic alkalosis?

A client on continuous nasogastric suction and whose hypertension is being treated with diuretics -Nasogastric suction creates a significant risk for metabolic alkalosis due to the loss of gastric acids. This risk is compounded by the concurrent use of diuretics. Alcohol use is associated with metabolic acidosis. Infections are not directly linked with the development of metabolic alkalosis.

The nurse who is providing care for several clients recognizes which client is at the highest risk for developing an acid-base imbalance?

A client who is being treated for acute kidney injury and who requires dialysis -Because of the key role that the kidneys play in the maintenance of acid-base balance, individuals with kidney disease are vulnerable to acid-base disorders. Anaphylaxis, syphilis, and fistulas do not present particular risks for acid-base imbalances.

In which client would the nurse be most likely to assess the signs and symptoms of an acid-base imbalance?

A client with chronic obstructive pulmonary disease (COPD) whose most recent arterial blood gases reveal a PCO2 of 51 mm Hg -An elevated PCO2 is commonly associated with respiratory acidosis because excess CO2 ultimately increases the concentration of H+ ions. Increased intracranial pressure, oxytocin infusion, and the administration of hypotonic fluids are not directly linked to common alterations in acid-base balance.

A client's most recent laboratory results suggest the presence of metabolic alkalosis. What action by the nurse best addresses a potential cause of this acid-base imbalance?

Administering an antiemetic to treat the client's frequent vomiting -Vomiting results in the loss of hydrogen ions, potentially resulting in metabolic alkalosis. Constipation and skin breakdown are not among the most common causes of metabolic alkalosis. Acid-base imbalances frequently affect cognition, but a change in level of consciousness would not be a cause of the imbalance.

The nurse is caring for a client who has developed hypoxemia and tissue hypoxia. Which of these interventions does the nurse set as a priority intervention?

Administration of supplemental oxygen -Hypoxia and hypoxemia may be corrected by administration of supplemental oxygen. People with hyperventilation may benefit from reassurance, rebreathing from a paper bag during symptomatic attacks, and attention to the psychological stress. The other options are not appropriate for the treatment of hypoxia.

The nurse is caring for a client with dehydration who reports urine with a strong ammonia odor. How will the nurse explain this finding to the client?

Ammonia chloride is normally produced in the kidney's renal tubules to buffer acids. The odor is stronger because the urine is concentrated. -The ammonia buffer system is a normal physiologic process that promotes excretion of H+ in the urine. The secreted H+ ions combine with ammonia (NH3) and are eliminated in the urine as NH4Cl (ammonium chloride). So, it is normal to have ammonia in urine, and this ammonia contributes to the odor of urine. More concentrated urine will have a stronger odor of ammonia. Dehydration does not lead to an increased amount of ammonia in the blood. If this is present, it is evidence of liver disease, because the liver converts ammonia to urea for elimination by the kidneys. If ammonia is accumulating in the blood, the ammonia is not in the urine. Metabolic acidosis will lead to a lower urine pH, not a higher one.

Which laboratory test is used to determine the cause of metabolic acidosis?

Anion gap -The anion gap is often useful in determining the cause of the metabolic acidosis. None of the other tests are used to determine the cause of metabolic acidosis.

The nurse is caring for a client with ketoacidosis who is complaining of increasing lethargy and occasional confusion following several weeks of rigid adherence to a carbohydrate-free diet. The nurse understands which phenomenon is most likely occurring?

In the absence of carbohydrate energy sources, her body is metabolizing fat and releasing ketoacids. -Low carbohydrate diets can induce the fat metabolism and consequent metabolic acidosis that is more commonly associated with diabetic ketoacidosis. The acidotic state is not classified as respiratory in nature, and does not involve a buffer role for carbohydrates or insulin deficiency.

The nurse is caring for a client with lactic acidosis syndrome. Which assessment finding(s) is evidence the client is responding positively to treatment? Select all that apply.

Increase in bicarbonate, decrease in lactate, decrease in respiratory rate. -Lactic acidosis syndrome is caused by the effects of metabolic acidosis on body systems. The nurse observes for evidence of resolution of metabolic acidosis, such as a decrease in the lactate level, increase in bicarbonate level, and an increase in pH. A decrease in pH would indicate worsening acidosis. The nurse would expect less respiratory compensation for acidosis as the pH normalizes, which would be evidenced by a decrease in the client's respiratory rate. The nurse also observes for indication of improved liver function, which would include an improvement of albumin levels, not a decrease.

A client who has just had her first postoperative dinner out to celebrate her recovery from an intestinal bypass is brought to the emergency room by her spouse. He reports that his wife seems disoriented and is slurring her words. The client did not have any alcohol with her pasta dinner. What might be the cause of her symptoms?

Lactic acidosis -A unique form of lactic acidosis, called D-lactic acidosis, can occur in persons with intestinal disorders that involve the generation and absorption of D-lactic acid. D-lactic acidosis can occur in persons with jejunoileal bypass, in which there is impaired reabsorption of carbohydrate in the small intestine. Persons with D-lactic acidosis experience episodic periods of metabolic acidosis often brought on by eating a meal high in carbohydrates. Manifestations include confusion, cerebellar ataxia, slurred speech, and loss of memory. They may complain of feeling (or may appear) intoxicated.

A client has these arterial blood gas values: anion gap 20 mEq/L (20 mmol/L), pH 7.29, PCO2 37 mm Hg (4.92 mmol/L), HCO3- 11 mEq/L (11 mmol/L), base excess -6 mEq/L (-6 mmol/L). With what condition do these values correspond?

Lactic acidosis -Anion gap (AG) is the difference between the plasma concentration of sodium ions and the sum of the measured anions (chloride and bicarbonate). Normally, the AG value should be between 8 and 16 mEq/L. AG will rise above normal for conditions that commonly cause acidosis such as lactic acidosis and ketoacidosis. Hyperkalemia, lithium toxicity, hypercalcemia, hypermagnesemia, and multiple myeloma will cause a drop in the AG by raising the level of unmeasured cations. ABGs measure pH, carbon dioxide (PCO2), bicarbonate ion (HCO3-), oxygen (PO2), base excess, and the anion gap. A pH that is below 7.35 is considered acidic. The PCO2 is the primary indicator of respiratory function and falls between 35 and 45mm Hg. Bicarbonate (HCO3-) is the primary indicator of metabolic function and is acidic if below 22 mEq/L. Base excess measures the level of all the buffer systems in the blood. If the level is more than 0.2 mEq/L below the normal pH of 7.4 it is considered deficit and indicates metabolic acidosis.

The nurse is reviewing laboratory data for the client with an anion gap of 17. The nurse recognizes which condition is associated with an increased anion gap mEq/L (mmol/L)?

Lactic acidosis -The anion gap describes the difference between the serum concentration of the major measured cation (Na) and the sum of the measured anions (Cl and HCO3 ). This difference represents the concentration of unmeasured anions, such as phosphates, sulfates, organic acids, and proteins (Fig. 8-18). Normally, the anion gap ranges between 8 and 12 mEq/L (8 and 12 mmol/L). Lactic acidosis and ketoacidosis results in an increased anion gap as a result of elevated levels of metabolic acids. The other options result in a decreased anion gap.

The nurse is caring for a client with worsening respiratory acidosis. Which of these interventions does the nurse anticipate if the client's condition continues to deteriorate?

Mechanical ventilation -The treatment of acute and chronic respiratory acidosis is directed toward improving ventilation. In severe cases, mechanical ventilation may be necessary. The remaining options would not effectively treat respiratory acidosis.

A client has been brought to the emergency department after experiencing an apparent heroin overdose. The client's respiratory rate on admission is 5 breaths/min. What interventions have the potential to address this client's acid-base imbalance? Select all that apply.

Mechanical ventilation Administration of supplemental oxygen -Hypoventilation creates a risk for respiratory acidosis. The restoration of normal oxygenation is key to resolution, so mechanical ventilation and oxygen supplementation are indicated. Bronchodilators will not help increase the client's respiratory rate or address the client's risk of acid-base imbalance. Sodium bicarbonate would not be effective because the etiology of the client's acidosis would be respiratory, not metabolic. Hypertonic intravenous solutions do not resolve acid-base disorders.

A child accidentally consumes a container of wood alcohol. The ED physician knows that the child is at risk of developing which of the following? Metabolic acidosis Respiratory alkalosis Metabolic alkalosis Respiratory acidosis

Metabolic acidosis - Ingestion of methanol (wood alcohol) results in the production of metabolic acids and causes metabolic acidosis.

The nurse is caring for a client who has excessive diarrhea. Which acid-base disturbance does the nurse anticipate will result from having excessive diarrhea?

Metabolic acidosis -The client who has diarrhea has increased loss of bicarbonate from the intestinal tract, which results in metabolic acidosis. The pH value would be decreased, and the bicarbonate would be decreased.

The nurse is caring for a client with metabolic alkalosis. The nurse accepts which prescription(s) as appropriate for this diagnosis? Select all that apply.

Potassium supplementation antiemetics to reduce vomiting intravenous sodium chloride -Common causes of metabolic alkalosis include upper gastrointestinal fluid loss, leading to a potassium and acid deficit. Preventing vomiting will prevent acid and potassium loss, reducing alkalosis. There should also be a correction of chloride deficit with sodium chloride as needed. The nurse would not accept a prescription for loop diuretic therapy as appropriate, because a loop diuretic would promote further loss of potassium and worsen alkalosis. Sodium bicarbonate would add more bicarbonate, worsening alkalosis.

The renal control mechanism of restoring the acid-base balance is accomplished through which process?

Reabsorption of HCO3 and excretion of H+ restores acid-base balance through the renal control mechanisms. -Reabsorption of HCO3 and excretion of H+ restores acid-base balance through the renal control mechanisms. Respiratory control mechanisms of restoring acid-base balance are done via regulation of production of carbonic acid and stimulation of the chemoreceptors in the brain.

The nurse is caring for a client who complains of headache and blurred vision. The nurse recognizes that these symptoms, accompanied by increased plasma partial pressure carbon dioxide (PCO2) level and decreased pH level, are consistent with which diagnosis?

Respiratory acidosis -Respiratory acidosis is reflected in the ABG as an increased PCO2 and decreased pH level as well as headache, blurred vision, irritability, muscle twitching, and psychological disturbances.

The nurse is caring for a client who has developed lactic acidosis syndrome (LAS). Which intervention is the nurse's priority?

administering intravenous fluids -If a client develops lactic acidosis syndrome (LAS), the cause will first be addressed. For example, if linked to the use of a nucleoside reverse transcriptase inhibitor (NRTI), the medication will be discontinued. Once LAS has developed, serious hypotension can develop. Therefore, intravenous fluids are the priority, because the fluids will expand intravascular volume to prevent cardiovascular collapse while also promoting renal clearance of lactate. Urine sample collection will not actively treat the LAS, nor will client teaching, making these actions less of a priority. Low oxygen levels are not associated directly with LAS. If respiratory function is affected due to organ failure, the nurse will apply oxygen based on the client's oxygen saturation levels.

A client with a long history of alcohol abuse has been admitted to the emergency department after several of days of heavy drinking. The nurse can best promote the restoration of the client's acid-base balance by:

administering intravenous sodium bicarbonate as prescribed. -Sodium bicarbonate is among the more common treatments for the metabolic acidosis that results from high alcohol intake. Breathing exercises do not have appreciable effect, though respiratory compensation will likely be taking place. Magnesium sulfate addresses a likely electrolyte imbalance, not an acid-base imbalance. The client's position will have a negligible effect on acid-base balance.

As other mechanisms prepare to respond to a pH imbalance, immediate buffering is a result of increased:

bicarbonate/carbonic acid regulation. -The bicarbonate buffering system, which is the principal ECF buffer, uses H2CO3 as its weak acid and bicarbonate salt such as sodium bicarbonate (NaHCO3) as its weak base. It substitutes the weak H2CO3 for a strong acid such as hydrochloric acid or the weak bicarbonate base for a strong base such as sodium hydroxide. The bicarbonate buffering system is a particularly efficient system because its components can be readily added or removed from the body. Hydrogen and potassium exchange freely across the cell membrane to regulate acid-base balance. Sodium is not part of the buffering system. Intracellular protein is part of the body protein buffer system; albumin is extracellular.

The nurse is caring for a client who has an elevation of carbon dioxide (CO2) on an arterial blood gas test. The nurse will prioritize assessment for which condition?

condition that affects the client's respiratory functioning -Carbon dioxide (CO2) is a volatile acid that is excreted by the lungs, so the nurse would prioritize assessing the client's respiratory function. The respiratory compensation for metabolic acidosis is to lower CO2 levels, not elevate them. If bicarbonate is being converted into carbonic acid, this lowers bicarbonate levels, which is associated with metabolic acidosis. Although increased metabolic rates increase the production of CO2 by cellular respiration, if the client has a functioning respiratory system, the respiratory rate will rise, which excretes the CO2. An example is increased respirations when exercising.

The nurse is examining a client's laboratory results and notes a decreased blood pH level. Which finding will the nurse apply as the best evidence that the client is experiencing metabolic acidosis?

decreased HCO3− -Metabolic disorders result in an alteration in HCO3− caused by the addition or loss of nonvolatile acid or base in the extracellular fluid. Therefore, the nurse applies the low HCO3− as the reason for the client's decrease in pH in the case of metabolic acidosis. Although compensation for metabolic acidosis may cause a decrease in CO2 level, this cannot confirm the diagnosis. Similarly, an elevated anion gap and elevated potassium are both associated with metabolic acidosis, but these can be absent in metabolic acidosis or may have other causes. It is only the combination of a low pH and a low HCO3− that confirms metabolic acidosis.

The nurse cares for a client diagnosed with diabetic ketoacidosis. Which finding will the nurse document as evidence of compensation for this type of metabolic acidosis?

increased depth and rate of respirations -Compensation for metabolic acidosis is performed by the respiratory system. Increasing the rate and depth of respirations enables excess carbon dioxide to be exhaled. In other words, the body creates a state of respiratory alkalosis to raise the pH and reduce the degree of acidosis. Although increased thirst and urine output are symptoms of diabetic ketoacidosis, these are not compensations for acidosis. The renal system is not able to actively absorb bicarbonate when metabolic dysfunction is present.