CH 14 Concepts of Acid-Base Balance

Which client arterial blood pH value will the nurse interpret as normal? 7.37 7.27 7.47 7.5

7.37 The normal range for arterial blood pH is 7.35 to 7.45. A value of 7.27 indicates acidosis. Values of 7.47 and 7.5 indicate alkalosis.

Which client arterial blood pH value indicates to the nurse the lowest concentration of free hydrogen ions? 7.45 7.42 7.36 7.29

7.45 The concentration of hydrogen ions is inversely (negatively) related to the pH. Thus the lower the pH, the higher the concentration of hydrogen ions and the higher the pH, the lower the concentration of free hydrogen ions. The pH of 7.29 represents the greatest concentration of free hydrogen ions in this list and the pH of 7.45 represents the lowest concentration of free hydrogen ions.

Which client will the nurse observe frequently for indications of hyperkalemia? A 72 year old receiving total parenteral nutrition A 65 year old taking furosemide for chronic heart failure A 38 year old being managed for diabetic ketoacidosis A 30 year old who has anxiety-induced hyperventilation

A 38 year old being managed for diabetic ketoacidosis Hyperkalemia occurs as compensation for any type of acidosis, including diabetic ketoacidosis, by having cells take up excess hydrogen ions (from the acidosis) in exchange for releasing intracellular potassium to maintain electroneutrality in both fluid compartments. The client receiving TPN is at risk for metabolic alkalosis due to an increase in base components. Hyperventilation leads to respiratory alkalosis, which causes hypokalemia. Furosemide increases potassium loss, leading to hypokalemia.

Which acid-base problem does the nurse expect when the ventilator of a client being mechanically ventilated is set at too high a rate of breaths per minute for 6 hours? Acid-deficit alkalosis Acid excess acidosis Base excess alkalosis Base-deficit acidosis

Acid-deficit alkalosis A ventilator set at either too high a ventilation rate and/or at too great a tidal volume will cause the client to lose too much carbon dioxide, leading to an acid-deficit respiratory alkalosis.

For which signs and symptoms will the nurse assess in a client who has acute respiratory acidosis with a PaCO2 level of 88 mm Hg? (Select all that apply.) Hyperactive deep tendon reflexes Acute confusion Lethargy Hypotension pH 7.49 Tall T-waves

Acute confusion Lethargy Hypotension Tall T-waves When caring for a client with acute respiratory failure and respiratory acidosis, the nurse would assess for lethargy, hypotension, and fatigue. Clients with acidosis have problems associated with decreased excitable tissues, including hypotension and decreased perfusion, impaired memory and cognition, increased risk for falls, and reduced neuromuscular responses (not hyperactive deep tendon reflexes). The pH will be below 7.35, which is a characteristic of acidosis. Acute confusion occurs because of reduced gas exchange and reduced cognition.

Which problem does the nurse expect resulted in a client's acid-base imbalance during an illness that causes vomiting for 2 days? Alkalosis from overelimination of hydrogen ions Acidosis from overproduction of of hydrogen ions Alkalosis from overproduction of bicarbonate ions Acidosis from underelimination of bicarbonate ions

Alkalosis from overelimination of hydrogen ions Prolonged or excessive vomiting results in alkalosis from overelimination of hydrogen ions when stomach hydrochloric acid is lost in the vomit.

What is the relationship between free hydrogen ions and carbon dioxide? An increase in free hydrogen ions always lowers carbon dioxide levels. Carbon dioxide can bind free hydrogen ions to increase the pH. Carbon dioxide can bind free hydrogen ions to decrease the pH. An increase in free hydrogen ions always increases carbon dioxide levels.

An increase in free hydrogen ions always increases carbon dioxide levels. In human physiology and homeostasis, free hydrogen ions and carbon dioxide levels are directly related. Any condition that changes the concentration of one always causes a corresponding change in the concentration of the other in the same direction. Carbon dioxide is not a buffer and does not directly bind free hydrogen ions.

Which action does the nurse expect is most likely to help restore acid-base balance in a client whose arterial blood pH is 7.17 immediately after a grand mal seizure? Administering bicarbonate orally or intravenously Providing hydration with IV normal saline Administering insulin Applying oxygen

Applying oxygen The severe acidosis seen immediately following a grand mal seizure is both respiratory and metabolic in origin (a combined acidosis). The client does not breathe during the actual seizure, which causes a huge retention of carbon dioxide (respiratory acidosis). The carbon dioxide level is very high because the seizing muscles are working hard under anaerobic conditions creating lots of lactic acid and hydrogen ions (metabolic acidosis), which are then converted to carbon dioxide through the carbonic anhydrase reaction. If the client stops having seizure activity, he or she will return to acid-base balance without intervention. This return occurs earlier when oxygen is applied. Bicarbonate is not lost during a seizure and most definitely should not be replaced. Hydration and insulin do nothing to restore acid-base balance in this situation.

Which body system will the nurse assess first to prevent harm for a client who has severe metabolic acidosis? Gastrointestinal system Respiratory system Cardiovascular system Autonomic nervous system

Cardiovascular system During acidosis, the body attempts to bring the pH closer to normal by moving free hydrogen ions into cells in exchange for potassium ions. This exchange can cause hyperkalemia, which alters all excitable membranes. In the heart, hyperkalemia can block electrical conduction through the heart and cause severe bradycardia and even cardiac arrest. Although all body systems are affected to some degree, the cardiovascular system must be assessed first to institute actions to prevent death.

For which client does the nurse remain alert for the possibility of respiratory acidosis? Client with increased urinary output Client who is anxious and breathing rapidly Client receiving IV normal saline bolus Client with multiple rib fractures

Client with multiple rib fractures A client with multiple rib fractures may have poor gas exchange from shallow breathing because of pain and because the rib fractures may inhibit adequate chest expansion. A client who is anxious and breathing rapidly is at risk for respiratory alkalosis, not acidosis. A normal saline bolus does not result in respiratory acidosis. An increased urinary output would not be a stimulus for a respiratory acid-base imbalance.

Where do free hydrogen ions normally come from in the human body? (Select all that apply.) Free hydrogen ions are produced by-products of carbohydrate and protein metabolism. Heavy exercise and muscle work produce hydrogen ions in the form of lactic acid. Ingestion of spicy food increases the concentration of uncontrolled free hydrogen ions. The kidney produces hydrogen ions when a urinary tract infection is present. Humans breathe in free hydrogen ions in the atmosphere from the buildup of greenhouse gases. Hydrochloric acid is produced in the stomach and is a normal source of free hydrogen ions.

Free hydrogen ions are produced by-products of carbohydrate and protein metabolism. Heavy exercise and muscle work produce hydrogen ions in the form of lactic acid. Hydrochloric acid is produced in the stomach and is a normal source of free hydrogen ions. Normal metabolic functions such as metabolism of carbohydrates, proteins, and fats for fuel all result in products that contribute to the free hydrogen ion concentration. Hydrochloric acid in the stomach is broken down into free hydrogen ions and chloride ions. Exercising muscles produce some lactic acid, which also contributes to normal hydrogen ion production. The hydrogen ions present in the urine during a urinary tract infection are produced by the bacteria, not the kidney. Greenhouse gases are not a normal source of free hydrogen ions and neither is the ingestion of spicy foods.

Which condition does the nurse consider as most likely to have caused a client's arterial blood gas value to show an increased pH? Water retention Partial airway obstruction Nasogastric suction Diabetic ketoacidosis

Nasogastric suction Nasogastric suction results in alkalosis from overelimination of hydrogen ions when stomach hydrochloric acid removed by the continuous suction.

Which mechanism will the nurse consider the most likely cause of pure acute respiratory acidosis in a client who has bilateral pneumonia? Underelimination of bicarbonate ions Underproduction of hydrogen ions Overelimination of bicarbonate ions Overelimination of hydrogen ions Overproduction of hydrogen ions Underelimination of hydrogen ions Underproduction of bicarbonate ions Overproduction of bicarbonate ions

Overproduction of hydrogen ions Unlike metabolic acidosis, respiratory acidosis results from only one cause—retention of CO2, causing overproduction of free hydrogen ions. Bicarbonate is not involved as a cause or as a compensatory mechanism. Recall that carbon dioxide and hydrogen ions are directly related in human physiology. An increase in one always causes an increase in the other. Retention of CO2 is the problem, not failure of the body to directly eliminate hydrogen ions.

Which acid-base disturbance will the nurse remain alert for when caring for a client who has chest burns with tight eschar banding the chest? Respiratory acidosis Metabolic acidosis Metabolic alkalosis Respiratory alkalosis

Respiratory acidosis The tight eschar on the chest can limit chest movement and make breathing less effective with hypoventilation. This problem results in inadequate oxygenation and retention of carbon dioxide, causing respiratory acidosis. Respiratory alkalosis is caused by hyperventilation, increased rate or depth of breathing, causing carbon dioxide to be eliminated in excess. Metabolic acid-base disturbances are usually caused by nonrespiratory issues.

Which laboratory value will the nurse check immediately to prevent harm for a client with metabolic alkalosis who now has a positive Chvostek sign? Serum calcium Serum magnesium Serum glucose level Serum sodium

Serum calcium A positive Chvostek sign is associated with alkalosis accompanied by a low serum calcium level. The hypocalcemia cause overexcitement of the nervous system with dizziness, agitation, confusion, and hyperreflexia, which may progress to seizures. Tingling or numbness may occur around the mouth and in the toes. If the client has hypocalcemia, the nurse must report the finding immediately to the health care provider so actions can be taken to prevent harm.

Which conditions could cause a client to develop acidosis? (Select all that apply.) Ventilator at too low a tidal volume Sepsis Severe diarrhea Hypovolemic shock Prolonged nasogastric suctioning Hyperventilation

Ventilator at too low a tidal volume Sepsis Severe diarrhea Hypovolemic shock Sepsis and hypovolemic shock result in anaerobic metabolism and increased production of carbon dioxide, lactic acid, and free hydrogen ions. When a ventilator is set at too low of a tidal volume for the client's size, hypoventilation occurs with poor gas exchange and retained carbon dioxide. Severe diarrhea causes excess loss of bicarbonate ions in the stool, resulting in a base-deficit metabolic acidosis. Hyperventilation can result in respiratory alkalosis, not acidosis. Prolonged nasogastric suctioning results in a loss of hydrochloric acid and leads to an acid-deficit metabolic alkalosis.