Chapter 10: Principles of Fluid and Electrolytes

A patient's serum sodium concentration is within the normal range. What should the nurse estimate the serum osmolality to be?

275-300 mOsm/kg Explanation: In healthy adults, normal serum osmolality is 270 to 300 mOsm/kg (Crawford & Harris, 2011c).

A client reports tingling in the fingers as well as feeling depressed. The nurse assesses positive Trousseau's and Chvostek's signs. Which decreased laboratory results does the nurse observe when the client's laboratory work has returned?

Calcium Explanation: Calcium deficit is associated with the following symptoms: numbness and tingling of the fingers, toes, and circumoral region; positive Trousseau's sign and Chvostek's sign; seizures, carpopedal spasms, hyperactive deep tendon reflexes, irritability, bronchospasm, anxiety, impaired clotting time, decreased prothrombin, diarrhea, and hypotension. Electrocardiogram findings associated with hypocalcemia include prolonged QT interval and lengthened ST.

The nurse is caring for a client in heart failure with signs of hypervolemia. Which vital sign is indicative of the disease process?

Elevated blood pressure Explanation: Indicative of hypervolemia is a bounding pulse and elevated blood pressure due to the excess volume in the system. Respirations are not typically affected unless there is fluid accumulation in the lungs. Temperature is not generally affected.

A nurse is monitoring a client being evaluated who has a potassium level of 7 mEq/L (mmol/L). Which electrocardiogram changes will the client display?

peaked T waves Explanation: The earliest changes occur when the serum potassium level is 7 mEq/L (mmol/L). Cardiac tracings include peaked and narrow T waves, ST segment depression, and a shortened QT interval

The nurse is instructing a client with recurrent hyperkalemia about following a potassium-restricted diet. Which statement by the client indicates the need for additional instruction?

"I will not salt my food; instead I'll use salt substitute." Explanation: The client should avoid salt substitutes. The nurse must caution clients to use salt substitutes sparingly if they are taking other supplementary forms of potassium or potassium-conserving diuretics. Potassium-rich foods to be avoided include many fruits and vegetables, legumes, whole-grain breads, lean meat, milk, eggs, coffee, tea, and cocoa. Conversely, foods with minimal potassium content include butter, margarine, cranberry juice or sauce, ginger ale, gumdrops or jellybeans, hard candy, root beer, sugar, and honey. Labels of cola beverages must be checked carefully because some are high in potassium and some are not

Which is considered an isotonic solution?

0.9% normal saline Explanation: An isotonic solution is 0.9% normal saline (NaCl). Dextran in normal saline is a colloid solution, 0.45% normal saline is a hypotonic solution, and 3% NaCl is a hypertonic solution.

A client has chronic hyponatremia, which requires weekly laboratory monitoring to prevent the client lapsing into convulsions or a coma. What is the level of serum sodium at which a client can experience these side effects?

114 mEq/L Explanation: Hyponatremia occurs when the serum sodium level dips below 135 mEq/L. When serum sodium levels fall below 115mEq/L, mental confusion, muscular weakness, anorexia, restlessness, elevated body temperature, tachycardia, nausea, vomiting, personality changes, convulsions, or coma can occur. A serum sodium level of 148 mEq/L would indicate hypernatremia. Normal serum concentration levels range from 135 to 145 mEq/L

A nurse can estimate serum osmolality at the bedside by using a formula. A patient who has a serum sodium level of 140 mEq/L would have a serum osmolality of:

280 mOsm/kg. Explanation: Serum osmolality can be estimated by doubling the serum sodium or using the formula: Na × 2 = glucose/18 + BUN/3. Therefore, the nurse could estimate a serum osmolality of 280 mOsm/kg by doubling the serum sodium value of 140 mEq/L

A client with excess fluid volume and hyponatremia is in a comatose state. What are the nursing considerations concerning fluid replacement?

Administer small volumes of a hypertonic solution. Explanation: In clients with normal or excess fluid volume, hyponatremia is usually treated effectively by restricting fluid with clients who are not neurologically impaired. When the serum sodium concentration is overcorrected (exceeding 140 mEq/L) too rapidly or in the presence of hypoxia or anoxia, the client can develop neurological symptoms. However, if neurologic symptoms are severe (e.g., seizures, delirium, coma), or if the client has traumatic brain injury, it may be necessary to administer small volumes of a hypertonic sodium solution with the goal of alleviating cerebral edema. Incorrect use of these fluids is extremely dangerous, because 1 L of 3% sodium chloride solution contains 513 mEq (mmol/L) of sodium and 1 L of 5% sodium chloride solution contains 855 mEq (mmol/L) of sodium. The recommendation for hypertonic saline administration in clients with craniocerebral trauma is between 0.10 to 1.0 mL of 3% saline per kilogram of body weight per hour

Which is the most common cause of symptomatic hypomagnesemia?

Alcoholism Explanation: Alcoholism is currently the most common cause of symptomatic hypomagnesemia. Intravenous drug use, sedentary lifestyle, and burns are not the most common causes of hypomagnesemia.

An adult client is brought in to the clinic feeling thirsty with dry, sticky mucous membranes; decreased urine output; fever; a rough tongue; and lethargy. The nurse reconciles the client's medication list and notes that salt tablets had been prescribed. What would the nurse do next?

Consider sodium restriction with discontinuation of salt tablets. Explanation: The client's symptoms of feeling thirsty with dry, sticky mucous membranes; decreased urine output; fever; a rough tongue; and lethargy suggest hypernatremia. The client needs to be evaluated with serum blood tests soon; a later appointment will delay treatment. It is necessary to restrict sodium intake. Salt tablets and a sodium chloride IV will only worsen this condition. A Lactated Ringer's IV is a hypertonic IV and is not used with hypernatremia. A hypotonic solution IV may be a part of the treatment, but not along with the salt tablets

A nurse is caring for a client with metastatic breast cancer who is extremely lethargic and very slow to respond to stimuli. The laboratory report indicates a serum calcium level of 12.0 mg/dl, a serum potassium level of 3.9 mEq/L, a serum chloride level of 101 mEq/L, and a serum sodium level of 140 mEq/L. Based on this information, the nurse determines that the client's symptoms are most likely associated with which electrolyte imbalance?

Hypercalcemia Explanation: The normal reference range for serum calcium is 8.6 to 10.2 mg/dl. A serum calcium level of 12 mg/dl clearly indicates hypercalcemia. The client's other laboratory findings are within their normal ranges, so the client doesn't have hypernatremia, hypochloremia, or hypokalemia.

Which intervention is most appropriate for a client with an arterial blood gas (ABG) of pH 7.5, a partial pressure of arterial carbon dioxide (PaCO2) of 26 mm Hg, oxygen (O2) saturation of 96%, bicarbonate (HCO3-) of 24 mEq/L, and a PaO2 of 94 mm Hg?

Instruct the client to breathe into a paper bag. Explanation: The ABG results reveal respiratory alkalosis. The best intervention to raise the PaCO2 level would be to have the client breathe into a paper bag. Administering a decongestant, offering fluids frequently, and administering supplemental oxygen wouldn't raise the lowered PaCO2 level.

A physician orders an isotonic I.V. solution for a client. Which solution should the nurse plan to administer?

Lactated Ringer's solution Explanation: Lactated Ringer's solution, with an osmolality of approximately 273 mOsm/L, is isotonic. The nurse shouldn't give half-normal saline solution because it's hypotonic, with an osmolality of 154 mOsm/L. Giving 5% dextrose and normal saline solution (with an osmolality of 559 mOsm/L) or 10% dextrose in water (with an osmolality of 505 mOsm/L) also would be incorrect because these solutions are hypertonic.

The nurse is caring for a client undergoing alcohol withdrawal. Which serum laboratory value should the nurse monitor most closely?

Magnesium Explanation: Chronic alcohol abuse is a major cause of symptomatic hypomagnesemia in the United States. The serum magnesium concentration should be measured at least every 2 or 3 days in clients undergoing alcohol withdrawal. The serum magnesium concentration may be normal at admission but may decrease as a result of metabolic changes, such as the intracellular shift of magnesium associated with intravenous glucose administration

A client in the emergency department reports that he has been vomiting excessively for the past 2 days. His arterial blood gas analysis shows a pH of 7.50, partial pressure of arterial carbon dioxide (PaCO2) of 43 mm Hg, partial pressure of arterial oxygen (PaO2) of 75 mm Hg, and bicarbonate (HCO3-) of 42 mEq/L. Based on these findings, the nurse documents that the client is experiencing which type of acid-base imbalance?

Metabolic alkalosis Explanation: A pH over 7.45 with a HCO3- level over 26 mEq/L indicates metabolic alkalosis. Metabolic alkalosis is always secondary to an underlying cause and is marked by decreased amounts of acid or increased amounts of base HCO3-. The client isn't experiencing respiratory alkalosis because the PaCO2 is normal. The client isn't experiencing respiratory or metabolic acidosis because the pH is greater than 7.35

A nurse reviews the arterial blood gas (ABG) values of a client admitted with pneumonia: pH, 7.51; PaCO2, 28 mm Hg; PaO2, 70 mm Hg; and HCO3--, 24 mEq/L. What do these values indicate?

Respiratory alkalosis Explanation: A client with pneumonia may hyperventilate in an effort to increase oxygen intake. Hyperventilation leads to excess carbon dioxide (CO2) loss, which causes alkalosis — indicated by this client's elevated pH value. With respiratory alkalosis, the kidneys' bicarbonate (HCO3-) response is delayed, so the client's HCO3- level remains normal. The below-normal value for the partial pressure of arterial carbon dioxide (PaCO2) indicates CO2 loss and signals a respiratory component. Because the HCO3- level is normal, this imbalance has no metabolic component. Therefore, the client is experiencing respiratory alkalosis.

A client comes to the emergency department with status asthmaticus. His respiratory rate is 48 breaths/minute, and he is wheezing. An arterial blood gas analysis reveals a pH of 7.52, a partial pressure of arterial carbon dioxide (PaCO2) of 30 mm Hg, PaO2 of 70 mm Hg, and bicarbonate (HCO3??') of 26 mEq/L. What disorder is indicated by these findings?

Respiratory alkalosis Explanation: Respiratory alkalosis results from alveolar hyperventilation. It's marked by a decrease in PaCO2 to less than 35 mm Hg and an increase in blood pH over 7.45. Metabolic acidosis is marked by a decrease in HCO3? to less than 22 mEq/L, and a decrease in blood pH to less than 7.35. In respiratory acidosis, the pH is less than 7.35 and the PaCO2 is greater than 45 mm Hg. In metabolic alkalosis, the HCO3? is greater than 26 mEq/L and the pH is greater than 7.45.

A client is diagnosed with syndrome of inappropriate antidiuretic hormone (SIADH). The nurse should anticipate which laboratory test result?

Serum sodium level of 124 mEq/L Explanation: In SIADH, the posterior pituitary gland produces excess antidiuretic hormone (vasopressin), which decreases water excretion by the kidneys. This, in turn, reduces the serum sodium level, causing hyponatremia, as indicated by a serum sodium level of 124 mEq/L. In SIADH, the serum creatinine level isn't affected by the client's fluid status and remains within normal limits. A hematocrit of 52% and a BUN level of 8.6 mg/dl are elevated. Typically, the hematocrit and BUN level decrease.