Chapter 7: Fluids, Electrolytes and Acid-Base Disorders
A patient is admitted with diabetic ketoacidosis (DKA). Labs include blood glucose 500 mg/dL, potassium 3.8 mg/dL, magnesium 1.9 mg/dL and sodium 128 mEq/L. What is the correct diagnosis? A. Hypertonic hyponatremia B. Isotonic hyponaremia C. Hypotonic hyponatremia D. Pseudohyponatremia
A. Hypertonic hyponatremia When blood glucose is elevated sodium appears low. The sodium value can be adjusted with the following formula: Corrected Na = serum Na + [0.016 x (serum glucose) - 100] Sodium is measured in mEq/L Serum glucose is measured in mg/dL
What is the compensatory response for acute respiratory acidosis? A. Increase serum HCO3 B. Decrease serum HCO3 C. Increase PCO2 D. Decrease PCO2
A. Increase serum HCO3 In acute respiratory acidosis the primary disturbance is an elevated PCO2. The expected compensatory response is a 1 mEq/L increase in HCO3 for every 10 mm Hg increase in PCO2. In chronic respiratory acidosis the compensatory response would be a 3.5 mEq/L increase in HCO3 for every 10 mm Hg increase in PCO2.
How are fluid needs impacted by fever? A. Increased B. Decreased
A. Increased Fluid needs increase by 7% for every degree Fahrenheit above normal (13% for each degree Celsius above normal).
What is the most accurate measure of calcium? A. Ionized calcium B. Corrected calcium C. Serum calcium D. Urinary calcium
A. Ionized calcium Direct measurement of ionized calcium is the most accurate method. This is especially important in critically ill patients because the equation often overestimates the corrected calcium concentration. Be aware that an ionized calcium can be painful without an arterial line as it will require an arterial puncture.
What does an elevated base excess indicate? A. Metabolic alkalosis B. Metabolic acidosis C. Respiratory alkalosis D. Respiratory acidosis
A. Metabolic alkalosis Base excess is a calculated value that estimates the metabolic component of an acid-base disorder. Elevated base excess indicates metabolic alkalosis. Base deficit occurs in metabolic acidosis
What is the primary symptom of magnesium deficiency? A. Neuromuscular hyperexcitability B. Ataxia C. Flaccid myelitis D. Hypotension
A. Neuromuscular hyperexcitability Neuromuscular hyperexcitability is the primary symptom of magnesium deficiency. Latent tetany elicited by positive Chvostek and Trousseau signs may be present. Frank generalized seizures may also occur in severe cases.
Which acid base disorder would be anticipated in a patient with GI and renal losses of bicarbonate? A. Normal anion gap metabolic acidosis B. Normal anion gap metabolic alkalosis C. Increased anion gap metabolic acidosis D. Increased anion gap metabolic alkalosis
A. Normal anion gap metabolic acidosis Normal anion gap metabolic acidosis can result from gastrointestinal loss of HCO3, renal loss of HCO3, ingestion of ammonium chloride and/or parenteral nutrition containing chloride salts.
What lab would you look at to determine the lungs ability to excrete carbon dioxide? A. PCO2 B. PO2 C. pH D. HCO3
A. PCO2 The partial pressure of carbon dioxide (PCO2) provides information on the lungs ability to excrete CO2. Changes in PCO2 are associated with respiratory processes that can lead to acid base disorders. An increases in PCO2 represents an acidosis, a decrease in PCO2 represents an alkalosis.
If serum potassium level is inappropriately elevated what should be done prior to treatment? A. Recheck the lab B. Order sodium zirconium cyclosilicate (Lokelma) C. Order EKG D. Replete IV instead of PO
A. Recheck the lab A repeat potassium level should be obtained, this often occurs with hemolyzed samples.
What must be present for maintenance of metabolic alkalosis? A. Renal impairment B. Liver impairment C. Maintenance IVF D. Renal replacement therapy
A. Renal impairment Some degree of impairment in renal HCO3 excretion must be present for maintenance of metabolic alkalosis. Mechanisms that sustain metabolic alkalosis can be classified into (1) volume-mediated processes (saline responsive) or (2) volume-independent processes (saline unresponsive).
What is an acid? A. Substance that can donate hydrogen ions (H+) B. Substance that can accept hydrogen ions (H+)
A. Substance that can donate hydrogen ions (H+) An acid is a substance that can donate hydrogen ions (H+). A base is a substance that can accept or combine with hydrogen ions. pH refers to the free H+ concentration that determines the acidity of body fluids. pH varies inversely with the H+ concentration. An increase in H+ concentration reduces the pH, a decrease in H+ concentration elevates the pH.
A patient who initially presents with generalized weakness, lethargy and constipation that progresses to ascending paralysis, muscle necrosis, arrhythmias and eventually death is most likely deficient in which electrolyte? A. Sodium B. Potassium C. Magnesium D. Phosphorus
B. Potassium Consequences of non-severe hypokalemia include generalized weakness, lethargy and constipation. Severe hypokalemia leads to muscle necrosis, ascending paralysis, arrhythmias and death.
What is considered clinically relevant hyponatremia? A. < 135 mEq/L B. < 130 mEq/L C. < 120 mEq/L D. < 115 mEq/L
B. Serum sodium < 130 mEq/L Upon recognition of clinically relevant hyponatremia (serum sodium < 130 mEq/L) determine the patient's sodium concentration, volume status. Identify the etiology of the hyponatremia and appropriate treatment.
Each compartment contains a major osmotically active solute that determines its osmotic pressure. What is the dominant extracellular osmole and Intracellular osmole, respectively? A. Potassium, sodium B. Sodium, potassium C. Nitrogen, sodium D. Bicarbonate, potassium
B. Sodium, potassium Sodium is the dominant extracellular osmole. Potassium is the primary intracellular osmole.
What enzyme allows for the maintenance of solute composition in the ECF and ICF and the regulation of cell volume? A. Cytochrome p450 B. Sodium-potassium-ATPase pump C. Lysozyme D. Alanine transaminase
B. Sodium-potassium ATPase pump Sodium-potassium-adenosine triphosphatase (Na-K-ATPase) pumps allows for the maintenance of the unique solute compositions of the ECF and ICF. It also plays a key role in the regulation of cell volume.
How does urine osmolality compare with serum osmolality in hypovolemic hypotonic hyponatremia? A. Urine osmolality = serum osmolality B. Urine osmolality > serum osmolality C. Urine osmolality < serum osmolality
B. Urine osmolality > serum osmolality In hypovolemic, hypotonic hyponatremia urine osmolality in these patients is always greater than serum osmolality indicating concentrated urine as the body attempts to retain fluid. Losses may be renal or extrarenal. Renal losses are usually caused by diuretic and identified by urine sodium < 20 mEq/L. Extrarenal losses can be caused by diarrhea, GI fistula output, excessive sweating, burns, open wounds and fluid drains and are associated with urine sodium > 20 mEq/L.
What is the mainstay of treatment for SIAD? A. Fluid resuscitation B. Hypertonic saline C. Fluid restriction D. medications such as octreotide
C. Fluid restriction The mainstay of treatment for SIAD is to restrict fluids to 500 to 1000 mL/d. If the patient is symptomatic exogenous salt is also administered. If SIAD is refractory to conventional treatment it may require pharmacologic therapy with loop diuretics and/or vasopressin-2 receptor antagonists (conivaptan or tolvaptan).
What diagnosis would be suspected in a patient with a total serum calcium < 8.4 mg/dL and ionized calcium < 1.12 mmol/L for one week after having a parathyroidectomy? A. Primary calcium deficiency B. Hyperaldosteronism C. Hungry bone syndrome D. Osteoporosis
C. Hungry bone syndrome (HBS) HBS is a rare significant and prolonged hypocalcemia that follows parathyroidectomy or thyroidectomy. It is refractory to elemental calcium, active vitamin D and calcitriol.
What are the differences between acute and chronic electrolyte abnormalities?
Development of an acute abnormality (less than 48 hours)is associated with symptoms that require immediate treatment (AMS w/acute hyponatremia) Chronic electrolyte disorder is often asymptomatic, and the patient may be harmed if the disorder is corrected too rapidly, as in the case of chronic hyponatremia. Absence of symptoms the chronologic trends in electrolyte values are generally more important than the absolute value on any given day
What urine chloride level is consistent with saline responsive metabolic alkalosis? A. Urine chloride < 20 mEq/L B. Urine chloride > 20 mEq/L C. Urine chloride < 10 mEq/L
A. Urine chloride < 20 mEq/L Saline responsible metabolic alkalosis is defined by a urine chloride level < 20 mEq/L. The increase in HCO3 reabsorption that maintains the alkalosis can be reversed by the administration of half isotonic or isotonic saline. Note in the setting of moderate to severe hypokalemia saline administration will not reverse the metabolic alkalosis, administration of potassium chloride will correct the disorder.
What are the 3 body compartments and what fraction of total body water (TBW) is contained within each? A. ⅔ Intracellular fluid ICF, ⅓ Extracellular fluid ECF, 3% Transcellular fluid TCF B. 1/3 Intracellular fluid ICF, 2/3 Extracellular fluid ECF, 3% Transcellular fluid TCF C. 3/4 Intracellular fluid ICF, 1/4 Extracellular fluid ECF D. 1/2 Intracellular fluid ICF, 1/2 Extracellular fluid ECF
A. ⅔ Intracellular fluid ICF, ⅓ Extracellular fluid ECF, 3% Transcellular fluid TCF
What is the most serious complication of hyperphosphatemia? A. Muscle cramps or spasms B. Bone and joint pain C. Red, itchy rash D. Soft tissue and vascular calcification
D. Soft tissue and vascular calcification All of the answer choices are symptoms of hyperphosphatemia, calcification is the most serious. Calcification occurs when the calcium-phosphorus product exceeds 55 mg2/dL (total serum calcium x serum phosphorus) .
Which of the following would alter an ionized calcium measurement? A. Albumin B. Phosphorus C. Magnesium D. Blood glucose level
B. Phosphorus Increase in serum phosphorus decreases the percentage of ionized calcium. Ionized calcium is also impacted by serum pH, metabolic alkalosis decreases the percentage of ionized calcium. Hypoalbuminemia decreases total serum calcium but does not affect ionized calcium levels. Magnesium and blood glucose do not directly impact ionized calcium levels.
In a metabolic acidosis with the primary disturbance loss of bicarbonate what would be the anticipated compensatory response? A. Decrease in PCO2 B. Increase in PCO2 C. Decrease in HCO3 D. Increase in HCO3
A. Decrease in PCO2 In a metabolic acidosis where the primary disturbance is a loss of HCO3 the anticipated compensatory response: would be a 1.2 mm Hg decrease in PCO2 for every 1 mEq/L increase in HCO3. The lungs will hyperventilate. In a metabolic alkalosis where the primary disturbance is retention of HCO3 the compensatory response is a 0.7 mm Hg increase in PCO2 for every 1 mEq/L increase in HCO3, or hypoventilation.
What are the 3 characteristics of metabolic acidosis? A. Decreased pH, primary disturbance HCO3, compensatory response PCO2 B. Increased pH, primary disturbance HCO3, Compensatory response PCO2 C. Decreased pH, primary disturbance PCO2, compensatory response HCO3 D. Increased pH, primary disturbance PCO2, compensatory response HCO3
A. Decreased pH, primary disturbance HCO3, compensatory response PCO2 Metabolic acidosis: 1. Decreased pH 2. Primary disturbance HCO3 3. Compensatory response PCO2
Which IVF should be provided with potassium repletion? A. Half normal saline B. D5 half normal saline C. D5W D. D5 normal saline
A. Half normal saline Consider the diluent when repleting potassium. Dextrose solutions should be avoided because they may worsen the hypokalemia by stimulating insulin release that promotes an intracellular shift of potassium.
If a patient presents with diaphoresis, flushing, drowsiness, AMS, weakness, hypotension and bradycardia which disorder of magnesium would you suspect? A. Hypermagnesemia B. Hypomagnesemia
A. Hypermagnesemia Physical findings of hypermagnesemia include: nausea/vomiting, diaphoresis, flushing, sensation of heat, depressed mental functioning, drowsiness, muscular weakness, loss of deep tendon reflexes, hypotension, bradycardia
What percentage of EN formulas is usually water? A. 70% B. 50% C. 25% D. < 10%
A. 70% EN tube feeding formulas are 67% to 87% water (about 160 to 210 mL water per 8 oz container) remainder is solids. The more energy dense a formula the lower the percentage of water.
What is the maximum infusion rate for IV repletion of magnesium? A. </= 1 g/hr B. < 5 g/hr C. </= 0.5 g/hr D. < 10 g/day
A. </= 1 g/hr Maximal magnesium infusion rates should not exceed 1 g/h (8 mEq/h) in asymptomatic patients because more than 50% of the dose may be lost in the urine as renal magnesium reabsorption is exceeded. Recommended empirical doses should be reduced by approximately 50% or more when administered to patients with renal impairment to reduce the risk of hypermagnesemia. IV treatment can be generally expected to produce a serum magnesium change of 0.1 mg/dL for each gram (8 mEq) administered. Plasma concentrations typically take up to 48 hours after the bolus to equilibrate
Assuming the same weight and serum sodium concentration, which of the following patients has the greatest free water deficit? A. A 35 year old man B. A 75 year old man C. A 35 year old woman D. A 75 year old woman
A. A 35 year old man Free water deficit = TBW x [1 - (140/serum sodium)] Free water deficit and total body water TBW are measured in liters, serum sodium is measured in mEq/L Given the same body weight and serum sodium concentration, the only variable is the percentage of TBW. Percentage of TBW increases as the proportion of lean body mass (LBM) to adipose tissue increases. Percentage of TBW decreases with age and is lower in females than in males. Younger men would be expected to have the highest proportion of LBM, highest percentage of TBW and largest free water deficit.
Which nutrition related process produces the most body acid? A. Cellular metabolism B. Intake of protein, carbohydrate and fat
A. Cellular metabolism Although small amounts of acidic substances enter the body via ingested foods most hydrogen ions originate as byproducts or end products of cellular metabolism. Metabolism of carbohydrates and fats alone result in the daily production of approximately 15,000 mmol carbon dioxide which combines with water to form carbonic acid (H2CO3). Protein metabolism accounts for another 50 to 100 mEq of daily acid (non-carbonic acid) production.
What are the 3 Characteristics of Metabolic alkalosis? A. Decreased pH, Increase serum HCO3, hyperventilation B. Increased pH, Increase serum HCO3, hypoventilation C. Increased pH, Decreased serum HCO3, hypoventilation D. Decreased pH, Decreased serum HCO3, hyperventilation
B. Increased pH, Increase serum HCO3, hypoventilation Metabolic acidosis is characterized by an increased pH with the primary disturbance in bicarbonate level and the compensatory response PCO2 via the lungs. Compensatory hypoventilation results in a rise in PCO2.
Which of the below choices are common causes of SIAD? A. Brain or CNS malignancy B. Lung malignancy C. Pneumonia D. Head trauma E. A, C, D F. All of the above
F. All of the above Brain or CNS malignancies, head trauma, lung malignancies and pneumonia are all common causes of SIAD.
Process of H+ regulation involves 3 sequential steps. Put the steps in the appropriate order 1. Control of the partial pressure of CO2 (PCO2) in the blood by alterations in the rate of alveolar ventilation 2. Chemical buffering by extracellular and intracellular mechanisms. Buffering prevents large changes in the H+ concentration 3. Control of the plasma bicarbonate concentration by changes in renal H+ excretion
Answer: 2, 1, 3
What value on the blood gas represents the ability of hemoglobin to carry oxygen? A. PCO2 B. PO2 C. pH D. HCO3
B. PO2 Partial pressure of oxygen represents the ability of hemoglobin to carry oxygen. The higher the PO2 value is the more saturated hemoglobin is with oxygen. The PO2 value is directly related to the arterial oxygen saturation (SaO2). When PO2 is high then the SaO2 of the blood is high.
In a patient who presents with elevated serum phosphorus and hypocalcemia what is the initial step in treating the patient's hypocalcemia? A. Thiamin supplementation B. Phosphate binders C. Optimize magnesium level D. Provide IV calcium
B. Phosphate binders Treatment with phosphate binders is warranted prior to calcium replacement in order to reduce the risk of soft tissue calcification.
What is the principal role of the lungs in maintaining acid-base balance? Regulation of: A. Oxygen B. Carbon dioxide C. Bicarbonate D. Hydrogen ions
B. Carbon dioxide The principal role of the lungs in acid-base balance is to regulate the pressure exerted by dissolved CO2 gas in the blood (PCO2). Rate and depth of ventilation can be altered to allow for the excretion of CO2 generated by the diet and metabolism. Rate and depth of ventilation begin to compensate for acid-base disturbances within minutes. Conditions that impair respiratory system functioning (opiate overdose) have the potential to cause acid-base imbalances
How does metabolic acidosis impact serum potassium? A. Causes hypokalemia B. Causes hyperkalemia C. Does not impact potassium levels
B. Causes hyperkalemia Metabolic acidosis causes hyperkalemia. Extracellular potassium shifts to maintain electroneutrality because some of the excess hydrogen ions are buffered intracellularly. For every 0.1 decrease in pH, potassium will increase by an average of 0.6 mEq/L *the increase can range from 0.3 to 1.3 mEq/L
What commonly causes euvolemic hypernatremia? A. Pituitary tumors B. Diabetes insipidus C. Subarachnoid hemorrhage D. Cerebral salt wasting
B. Diabetes insipidus Euvolemic hypernatremia is commonly caused by diabetes insipidus. Diabetes insipidus can be either central or nephrogenic in etiology. Central diabetes insipidus is an impairment of ADH secretion. Nephrogenic condition occurs when the kidneys cannot respond to ADH circulating in the serum. Both types of diabetes insipidus lead to excessive water losses via the urine
What results when there is a disruption between plasma oncotic and hydrostatic pressures? A. Dehydration B. Edema C. Thrombosis D. Embolism
B. Edema (or third spacing) Disruption in oncotic and/or hydrostatic pressure results in a net flow of fluid from one compartment to another. This disruptions favors a plasma to interstitial fluid shift or "third spacing". The accumulation of excess fluid in the interstitial space is termed edema. Fluid can also accumulate in other spaces and is termed effusion or ascites. Although the fluid will be absorbed back into the extracellular compartment over a period of days to weeks acute reduction in blood volume if not replaced can lead to severe volume depletion
What fluids are included in the transcellular fluid compartment TCF?
Includes specialized fluids cerebrospinal fluid, aqueous humor of the eye, secretions of the GIT
How would you expect adrenal insufficiency, immobilization and/or tuberculosis to impact calcium levels? A. Hypocalcemia B. Hypercalcemia
B. Hypercalcemia Hypercalcemia most often occurs in hyperparathyroidism and cancer with bone metastases (primarily breast cancer, lung cancer and multiple myeloma). It can also occur with toxic levels of vitamin A or vitamin D, chronic ingestion of milk and/or calcium carbonate containing antacids in the setting of renal insufficiency (aka milk-alkali syndrome), adrenal insufficiency, immobilization, tuberculosis and medications such as thiazide diuretics and lithium.
How would you anticipate rhabdomyolysis to impact a patient's serum phosphorus level? A. No change B. Increase C. Decrease
B. Increase Hyperphosphatemia may be caused by the endogenous release of phosphorus into the ECF from cellular destruction that occurs during rhabdomyolysis. This can also be seen in massive trauma, cytotoxic treatments (especially in lymphomas and leukemias with large tumor burden), catabolic states, hemolysis and malignant hyperthermia.
How does 1 liter of D5W distribute between the extracellular ECF and intracellular ICF? How much volume will remain in the intravascular space? A. 800 mL ICF, 150 mL ECF with 50 mL in the intravascular space B. 667 mL ICF, 333 mL ECR with 83 mL in the intravascular space C. 700 mL ICF, 100 mL ECF with 200 mL in the intravascular space D. 1000 mL ICF, no fluid will remain in the ECF
B. 667 mL ICF, 333 mL ECR with 85 mL in the intravascular space Exogenous administration of intravenous (IV) fluid 1 liter 5% dextrose in water (solute-free water) is infused dextrose is metabolized. The resulting 1L water distributes proportionately to all fluid compartments. ⅔ (667 mL) of the fluid distributes to the ICF ⅓ (333 mL) distributes into the ECF 1/4 distributed into the ECF 25% (83 mL) remains in the intravascular space
On an arterial blood gas, how would you classify a pH > 7.45? A. Acidemia B. Alkalemia C. Normal D. Isotonic
B. Alkalemia pH of arterial blood is normally maintained within the narrow range of 7.35 - 7.45. A pH below 7.35 is called acidemia. A pH greater than 7.45 is called alkalemia.
What is serum CO2? A. Carbon dioxide B. Bicarbonate C. Carbonic acid D. Carbon monoxide
B. Bicarbonate Serum CO2 (HCO3) is a component of the carbonic acid/bicarbonate buffer system. Calculated HCO3 reported in a blood gas or the measured serum HCO3 can be used to evaluate acid-base status An increase in serum HCO3 represents an alkalosis, a decrease represents acidosis.
Serum calcium concentrations are under hormonal control Primarily mediated by what 3 hormones? A. parathyroid, vitamin D, thyroxine B. calcitonin, vitamin D, parathyroid C. calcitonin, prostacyclin, vitamin D D. parathyroid, osteocalcin, vitamin D
B. Calcitonin, vitamin D and parathyroid hormone PTH, vitamin D and calcitonin are the primary mediators of serum calcium concentration. Low serum calcium concentrations stimulate release of PTH which increases bone resorption, augments renal conservation of calcium, and activates vitamin D. Calcitonin released by the thyroid gland in response to elevated serum calcium concentrations, acts to inhibit bone resorption and increases urinary calcium excretion
IV potassium phosphate is the preferred treatment of hypophosphatemia except in what 2 situations? (choose 2 of the below answers) A. Hyperkalemia B. Hypomagnesemia C. Renal insufficiency D. Liver failure
Both A. Hyperkalemia and C. Renal insufficiency are correct IV potassium phosphate is contraindicated if the potassium concentration is greater than 4 mEq/L and/.or if renal insufficiency exists. Remember that 3 mmol potassium phosphate will provide 4.4 mEq potassium.
What is the final and slowest mechanism by which the body maintains acid-base balance? A. Altering ventilation to change CO2 excretion B. Altering renal CO2 excretion C. Altering renal H+ excretion D. Altering ventilation to change HCO3 excretion
C. Altering renal H+ excretion Only the kidneys have the ability to regulate levels of alkaline substances in the blood and eliminate metabolic acids (organic acids other than carbonic acid) from the body. The kidneys accomplish this through 2 processes, (1) reabsorption of filtered HCO3 and (2) excretion of the H+ produced daily. Excretion of hydrogen ions is the final protective mechanism for acid-base balance.
What is the primary disturbance in acute respiratory alkalosis? A. Increased PCO2 B. Increased HCO3 C. Decreased PCO2 D. Decreased HCO3
C. Decreased PCO2 In acute respiratory alkalosis the primary disturbance is a decrease in PCO2. The compensatory response is 2 mEq/L decrease in HCO3 for every 10 mm Hg decrease in PCO2. In chronic respiratory alkalosis the compensatory response would be 4 mEq/L decrease in HCO3 for every 10 mm Hg decrease in PCO2.
What is the common iatrogenic cause of metabolic alkalosis? A. Fluid resuscitation with normal saline B. Fluid resuscitation with lactated ringers C. Excess bicarbonate or acetate in IV solutions D. D5W as the primary IV medication carrier
C. Excess bicarbonate or acetate in IV solutions Metabolic alkalosis is most often caused by the overzealous treatment of metabolic acidosis with bicarbonate or an excess of acetate in PN solutions (which is metabolized to bicarbonate with a normally functioning liver). Transcellular shift of H+ that typically occur with severe hypokalemia may contribute to the development of a metabolic alkalosis.
Serum osmolality can be directly measured or it can be calculated. What would be an appropriate next step if there is a difference between the 2 values? A. Serum lab should be repeated B. It is likely chronic, no treatment to be pursued C. Assess for ethylene glycol ingestion D. Provide normal saline at 20 mL/kg
C. Assess for ethylene glycol ingestion Serum and calculated osmolalities should be relatively close in value. If there is a difference between the 2 values the patient should be assessed for possible ingestion of toxic substances (ethylene glycol, propylene glycol) that can cause a gap between serum and calculated osmolality Serum osmolality = 2 x {[(serum Na) + (serum glucose)/18] + [BUN/2.8]} Serum osmolality is measured in mOsm/kg, serum sodium is measured in mEq/L and serum glucose and BUN are measured in mg/dL
How is chronic or asymptomatic hypocalcemia treated? A. Monthly IV calcium supplementation B. Oral calcium supplements C. Oral calcium and vitamin D supplements D. Parathyroid hormone replacement
C. oral calcium and vitamin D supplements
Which of the following is not a treatment for hyperkalemia? A. Insulin B. Dialysis C. Beta blockers D. Diuretics
C. Beta blockers Hyperkalemia can be corrected with insulin and dextrose, sodium bicarbonate, beta-adrenergic agonists (ie albuterol), loop and thiazide diuretics, cation-exchange resins (sodium polystyrene sulfonate), dialysis and calcium gluconate. Beta blockers may actually lead to hyperkalemia by causing potassium to shift from the ICF to the ECF.
What is the treatment for chronic hypercalcemia of malignancy? A. Ambulation and hydration B. Normal saline maintenance IVF daily C. Bisphosphonates D. Calcium restricted diet
C. Bisphosphonates Bisphosphonates have a primary role as maintenance therapy in the treatment of hypercalcemia of malignancy. The delayed onset of action of 4 to 10 days renders these agents useful only as maintenance therapy.
What is the recommended maximum infusion rate for replacing potassium? A. 20-40 mEq/h B. < 10 mEq/h C. 10-20 mEq/h D. 30-50 mEq/h
C. 10-20 mEq/h IV potassium infusion rates should generally not exceed 10 to 20 mEq/h. Infusion rates as high as 40 mEq/h have been used for emergent cases or severely symptomatic patients. If an infusion rate exceeding 10 mEq/h is required, continuous cardiac monitoring is recommended to detect any signs of hyperkalemia. Administration via a central venous catheter is recommended to minimize phlebitis and burning.
How is IV administration of 1 liter 0.9% NaCl (isotonic saline) distributed in the fluid compartments? A. 800 mL ICF, 150 mL ECF with 50 mL in the intravascular space B. 700 mL ICF, 300 mL ECR with 100 mL in the intravascular space C. 1000 mL ECF, no fluid will distribute to the ICF (250 mL intravascular space) D. 1000 mL ICF, no fluid will remain in the ECF
C. 1000 mL ECF, no fluid will distribute to the ICF Normal saline is an isotonic fluid and will retain in the extracellular fluid. One quarter or 250 mL remains in the intravascular space.
Due to risk for cerebral edema with rapid correction of acute hypernatremia (< 48 hours) what rate of correction is recommended? A. 6-8 mEq/L/d B. 10-12 mEq/L/d C. 2 mEq/L/hr D. 6-8 mEq/L/hr
C. 2 mEq/L/hr Due to the risk for cerebral edema and neurologic impairment sodium correction should be corrected at a rate of 2 mEq sodium per liter per hour until the serum sodium reaches 145 mEq/L in acute hypernatremia. In chronic hypernatremia (or unknown duration) correction rate should not exceed 10 mEq/L/d.
What is considered a clinically relevant osmolar gap between calculated and measured serum osmolality? A. > 1 mOsm/kg B. > 5 mOsm/kg C. > 10 mOsm/kg D. > 20 mOsm/kg
C. > 10 mOsm/kg Difference is > 10 mOsm/kg between calculated and serum osmolality is considered an osmolar gap.
What is the principal buffer system? A. Intracellular proteins B. Hemoglobin C. Carbonic acid/bicarbonate system D. Phosphate
C. Carbonic acid/bicarbonate system The carbonic acid/bicarbonate (H2CO3/HCO3)system is the principal buffer system. Intracellular proteins, hemoglobin and phosphate are all additional buffer systems. Buffer systems are primarily weak acids and base pairs can take up or release H+ so that changes in the free H+ concentration are minimized.
What is the treatment for mild hypercalcemia? A. Calcium binder B. Insulin C. Hydration and ambulation D. Bed rest
C. Hydration and ambulation Mild hypercalcemia usually responds well to hydration and ambulation. If hypercalcemia is severe IV hydration using 0.9% NaCl should be started promptly at 200 to 300 mL/h to reverse the volume depletion caused by hypercalcemia. After adequate hydration 40-80 mg IV furosemide may be used to enhance renal calcium excretion, diuretic use is controversial. Saline hydration can reduce serum calcium levels by 2 to 3 mg/dL within the first 48 hours of treatment. Calcitonin can also be used to treat acute hypercalcemia, however tachyphylaxis often limits its usefulness after 48 hours.
What is the common cause of saline-resistant metabolic alkalosis? A. High NGT output B. Diuretic use C. Hyperaldosteronism D. Daily antacid usage
C. Hyperaldosteronism Saline resistant metabolic alkalosis is commonly associated with hyperaldosteronism. It is characterized by a high urinary chloride concentration. Management consists of the treatment of the underlying cause of the mineralocorticoid excess. Aggressive potassium repletion should also be employed when hypokalemia is present with metabolic alkalosis in primary hyperaldosteronism.
What electrolyte abnormality would be anticipated after massive blood transfusion? A. Hypokalemia B. Hypophosphatemia C. Hypocalcemia D. Hyponatremia
C. Hypocalcemia Hypocalcemia is common in critically ill patients. It is associated with sepsis, rhabdomyolysis and massive blood transfusions. Hypocalcemia occurs with blood transfusions secondary to the citrate preservative in the blood binding to serum calcium.
A patient with severe intractable nausea and vomiting is at risk for which of the following acid-base disorders? A. Hyperchloremic metabolic acidosis B. Hyperchloremic metabolic alkalosis C. Hypochloremic metabolic alkalosis D. Hypochloremic metabolic acidosis
C. Hypochloremic metabolic alkalosis Gastric fluids contain approximately 130 mEq chloride per liter and are very acidic (pH 1 to 2). Losing large amounts of gastric fluids via vomiting can result in a hypochloremic metabolic alkalosis as the loss of acid from the stomach leaves the body with a relative excess of alkali.
What is the treatment for severe symptomatic acute hypocalcemia? A. Elemental calcium orally B. Vitamin D combined with calcium C. IV calcium D. Calcitonin intramuscularly
C. IV calcium In severe symptomatic acute hypocalcemia initially 1 g of calcium chloride (13.6 mEq calcium) or 3 g calcium gluconate (14 mEq calcium) may be given IV push over 10 minutes to control hypocalcemia symptoms. Continuous infusion of IV calcium may be required for severe acute hypocalcemia refractory to intermittent bolus doses.
Which acid base disorder would be anticipated when there is increased production of endogenous acid or failure to excrete acids? A. Normal anion gap metabolic acidosis B. Normal anion gap metabolic alkalosis C. Increased anion gap metabolic acidosis D. Increased anion gap metabolic alkalosis
C. Increased anion gap metabolic acidosis Increased anion gap metabolic acidosis can result from increased production of endogenous acid, failure to excrete acids and/or ingestion of exogenous acid.
What are the 3 characteristics of respiratory alkalosis? A. Increased pH, increase in PCO2, variable serum HCO3 B. Decreased pH, decrease in PCO2, variable serum HCO3 C. Increased pH, decrease in PCO2, variable serum HCO3 D. Decreased pH, increase in PCO2, increase serum HCO3
C. Increased pH, decrease in PCO2, variable serum HCO3 Respiratory alkalosis is characterized by elevated pH, decrease in PCO2 and variable reduction in serum HCO3 concentration. Respiratory alkalosis occurs when effective alveolar ventilation is increased beyond the level necessary to eliminate metabolically produced CO2
How does hypertonic saline (3% NaCl) impact the fluid compartments? A. Increases osmolality of ECF only B. Increases osmolality of ICF only C. Increases osmolality of ECF and ICF D. Decreases osmolality of ECF and ICF
C. Increases osmolality of ECF and ICF Addition of hypertonic fluid (eg 3% NaCl) to the ECF increases its tonicity, establishing an osmotic gradient that results in the movement of water out of cells and into the ECF until osmotic equilibrium is attained Osmolalities of both compartments increases ECF because of the addition of NaCL. ICF because of water loss. Volume change is proportional to the degree of increase in ECF osmolality.
A patient presents with the following labs Na 138 mmol/L, K 3.0, Magnesium 1.5 and Glucose 120 mg/dL. The MD asks you what electrolyte repletion to order first, what is your recommendation? A. Potassium B. Sodium C. Magnesium D. Phosphorus
C. Magnesium Magnesium deficit should be corrected because hypomagnesemia may result in refractory hypokalemia related to accelerated renal potassium loss or the impairment of Na-K-ATPase pump activity.
What acid base disturbance could be anticipated in a patient with asthma and hyperventilation? A. Metabolic alkalosis B. Metabolic acidosis C. Respiratory alkalosis D. Respiratory acidosis
C. Respiratory alkalosis Asthma and hyperventilation lead to respiratory alkalosis. Additional possible causes include: central stimulation of respiration, anxiety, pain, fever, brain tumors, vascular accidents, head trauma, pregnancy, catecholamines, salicylates, peripheral stimulation, pulmonary embolus, high altitudes, pneumonia, pulmonary edema, severe anemia and hepatic encephalopathy.
An inpatient has been receiving diuretic therapy in addition to continuous NGT suction. What acid base disorder are you most concerned for? A. Saline responsive metabolic acidosis B. Saline resistant metabolic acidosis C. Saline responsive metabolic alkalosis D. Saline responsive metabolic acidosis
C. Saline responsive metabolic alkalosis Saline responsive metabolic alkalosis is the most common type of metabolic alkalosis. Gastrointestinal losses, vomiting, NGT suction, renal losses, diuretic therapy, excessive bicarbonate administration and rapid correction of hypocapnia can all lead to saline responsive metabolic alkalosis. Urine chloride concentration is useful in the differential diagnosis, in saline responsive metabolic alkalosis urine chloride will be < 20 mEq/L. This predicts those patients likely to respond to volume replacement.
What differentiates euvolemic hypotonic hyponatremia from hypovolemic hypotonic hyponatremia? A. Urine osmolality B. Serum osmolality C. Urine sodium D. Serum sodium
C. Urine sodium In euvolemic hypotonic hyponatremia urine sodium is always > 20 mEq/L indicating that the kidneys are inappropriately concentrating urine and volume status is adequate, differentiating this condition from hypovolemic hypotonic hyponatremia.
Calcium must be adjusted for hypoalbuminemia, what is the formula?
Corrected total serum calcium (mg/dL) = measured total serum calcium + [0.8 x (4 - serum albumin(g/dL))] For each 1 g/dL decrease in albumin below 4 g/dL total serum calcium decreases by approximately 0.8 mg/dL
The administration of 1 liter 0.9% sodium chloride (NaCl) to a normonatremic patient will increase the intravascular and interstitial fluid compartments by: A. 1000 mL and 0 mL, respectively B. 0 mL and 1000 mL, respectively C. 750 mL and 250 mL, respectively D. 250 mL and 750 mL, respectively
D. 250 mL and 750 mL, respectively Solution of 0.9% NaCL (154 mEq/L) is isotonic, does not contribute to an osmotic gradient. Isotonic saline enters and remains in the ECF. Administering 1L of 0.9% NaCl expands the ECF by 1 liter. Intravascular volume accounts for 25% of the ECF and will expand by 250 mL. Remaining 750 mL will be distributed to the interstitial fluid compartment.
To prevent osmotic demyelination syndrome (ODS) what is an appropriate target rate for sodium correction in one day? A. 15 mEq/L/d B. 20 mEq/L/d C. < 5 mEq/L/d D. 6-8 mEq/L/d
D. 6-8 mEq/L The targeted rate of sodium correction for hyponatremia should not exceed 10 to 12 mEq/L/d if the condition is acute; 6 to 8 mEq/L/d if the condition is chronic or of unknown duration.
What is the pH compatible with life? A. 7.35-7.45 B. 6 - 7 C. < 8 D. 6.8 - 7.8
D. 6.8 - 7.8 The concentration of H+ in the body fluids must be tightly regulated to maintain a pH compatible with life (6.80 to 7.80)
What is the maximum infusion rate for phosphorus? A. 10 mmol/h B. 16 mmol/h C. 11 mmol/h D. 7 mmol/h
D. 7 mmol/h IV phosphorus infusion rates should not exceed 7 mmol/h because faster infusion rates can often cause thrombophlebitis and soft tissue calcium-phosphate deposition. If potassium phosphate is being used to replete phosphate, the rate of infusion of potassium may also be rate limiting.
What serum level of hypermagnesemia produces physical manifestations? A. > 2.5 mg/dL B. > 3.5 mg/dL C. > 4.0 mg/dL D. > 5 mg/dL
D. > 5 mg/dL Elevated magnesium levels that exceed 4.8 mg/dL can cause neurologic, neuromuscular, and cardiac manifestations.
What laboratory panel should be used to assess a patient's oxygenation and acid-base status? A. Chem 7 B. Basic metabolic panel C. Complete blood count D. Blood gas
D. Blood gas Blood gas measurements include pH, PCO2, partial pressure of oxygen in the blood (PO2), oxygen saturation (SaO2), calculated HCO3, base excess. Arterial blood gases (ABGs) reflect the ability of the lungs to oxygenate blood. Venous blood gases (VBGs) reflect tissue oxygenation.
What are common causes of hypertonic, hyponatremia? A. Hyperglycemia B. Administration hypertonic saline C. Mannitol administration D. Over diuresis E. Both A and C F. Both B and D
D. Both A and C Hypertonic, hyponatremia is caused by the presence of osmotically active substances other than sodium in the ECF. Common causes include hyperglycemia and mannitol administration
Why is edema common during critical illness? A. Aggressive fluid resuscitation B. Use of multiple IV therapies C. The acute phase response D. Capillary leak syndrome (CLS)
D. Capillary leak syndrome (CLS) Phenomenon is common during critical illness capillary permeability increases, resulting in the leakage of albumin from the intravascular to the interstitial space and reduced plasma oncotic pressure favors the movement of fluid from the intravascular to the interstitial space. This results in intravascular hypovolemia, peripheral edema and hemodynamic instability known as capillary leak syndrome.
Which of the following choices would lead to saline resistant metabolic alkalosis? A. Fluid resuscitation B. Prolonged diarrhea C. Excessive gastric losses D. Excessive licorice ingestion
D. Excessive licorice ingestion Saline resistant metabolic alkalosis (urine chloride > 20 mEq/L) can result from excess mineralocorticoids, Cushing's syndrome, hyperaldosteronism, profound hypokalemia (serum potassium < 2 mEq/L), and excessive licorice ingestion (eg from chewing tobacco).
What acid base disorder is characterized by a reduced pH, elevation in the PCO2 and a variable increase in the serum HCO2 concentration? A. Metabolic alkalosis B. Metabolic acidosis C. Respiratory alkalosis D. Respiratory acidosis
D. Respiratory acidosis In a respiratory acidosis the 3 main characteristics include (1) decreased pH, (2) primary disturbance in PCO2 and (3) compensatory response HCO3. Respiratory acidosis is characterized by a reduced pH, an elevation in the PCO2 and a variable increase in the serum HCO3 concentration.
What acid base disorder would be anticipated with parenteral or enteral nutrition overfeeding? A. Metabolic alkalosis B. Metabolic acidosis C. Respiratory alkalosis D. Respiratory acidosis
D. Respiratory acidosis Overfeeding can result in respiratory acidosis. Additional causes can include: central depression of respiration, drugs (opioids, anesthetics, sedatives), stroke, head injury, sleep apnea, perfusion abnormalities, massive pulmonary embolism, cardiac arrest, airway or pulmonary abnormalities, neuromuscular abnormalities, obesity hypoventilation (Pickwickian syndrome) and mechanical ventilator hypoventilation. Respiratory acidosis almost always results from decreased effective alveolar ventilation, not an increase in CO2 production. Hypoventilation can occur when any step in the ventilatory process is compromised
When treating hypernatremia an equation may be used to calculate the free water deficit for the initial replacement volume, what is this equation?
Free water deficit = TBW x [1 - (140/serum Na)] Free water deficit and TBW are measured in liters, serum sodium mEq/L Equation has been shown to underestimate free water losses by 1 to 2.5 liters
If a patient presents with muscle twitching, cramping, weakness, ascending paralysis, EKG changes and arrhythmias would you predict hypokalemia or hyperkalemia?
Hyperkalemia Muscle twitching, cramping, weakness, ascending paralysis, electrocardiogram changes (tall peaked T-waves; prolonged PR- interval; widened QRS complex, shortened QT interval), arrhythmias (bradyarrhythmias, ventricular fibrillation, asystole) are all symptoms of hyperkalemia
Hypotonic/Hypertonic or Isotonic? 3% NaCl (hypertonic saline)?
Hypertonic Sodium 513 mEq/L Chloride 513 mEq/L - 2331 mL/L free water
Hypotonic, Hypertonic or Isotonic? D5W (5% dextrose)?
Hypotonic Dextrose 50 g/L 1000 mL/L free water
Hypotonic/Hypertonic or Isotonic? 0.45% NaCl (½ normal saline)?
Hypotonic Sodium 77 mEq/L Chloride 77 mEq/L 500 mL/L free water
What is the metabolically active form of calcium?
Ionized calcium
Hypotonic/Hypertonic or Isotonic? Lactated Ringers?
Isotonic Sodium 130 mEq/L Chloride 109 mEq/L 0 mL/L free water
Hypotonic/Hypertonic or Isotonic? 0.9% NaCl (normal saline)?
Isotonic Sodium 154 mEq/L Chloride 154 mEq/L 0 mL/L free water
What is the general recommendation for oral potassium replacement?
Oral potassium dosages of 40 to 100 mEq/d divided into 2 to 4 doses are usually sufficient to correct hypokalemia. Slow release potassium tablets are available, however they are associated with risk of GI ulceration/bleeding.
When is IV potassium acetate selected for hypokalemia treatment instead of potassium chloride?
Potassium acetate is used as an alternative to potassium chloride in the presence of a metabolic acidosis because acetate is converted to bicarbonate by a normally functioning liver
What condition is euvolemic hypotonic hyponatremia commonly associated with? A. Cerebral salt wasting B. Subarachnoid hemorrhage SAH C. Syndrome of Inappropriate diuresis SIAD D. Osmotic demyelination syndrome ODS
SIAD Patients with SIAD have stable sodium intake/output but retain additional amounts of water because of excessive levels of antidiuretic hormone ADH (released from the pituitary gland and in small amounts from lung alveoli). ADH increases the synthesis of aquaporins in the collecting duct of the renal tubule causing increased reabsorption of water.
Order the 6 steps for analyzing an acid-base disorder 1. Assess PCO2 2. Assess pH 3. Determine chronicity 4. Assess serum HCO3 (CO2) 5. Determine if appropriate compensation is present 6. Calculate the anion gap
The correct order: 2, 1, 4, 6, 3, 5 1. Assess the pH of blood to determine whether the patient is acidemic (pH < 7.4) or alkalemic (pH > 7.4) If the pH is 7.4 an acid base disorder cannot be ruled out, Mixed acid-base disorder or compensation may be present 2. Assess the PCO2 to determine whether a respiratory process may be contributing. PCO2 is elevated the patient has a respiratory acidosis. PCO2 is low the patient has a respiratory alkalosis 3. Assess the serum HCO3 to determine whether a metabolic process may be contributing If the HCO3 is elevated the patient has a metabolic alkalosis. If the HCO3 is low the patient has a metabolic acidosis 4. Calculate the anion gap to determine whether metabolic acidosis is present. Critical to determine the etiology of the acid base disorder and select the appropriate treatment 5. Determine whether the acid-base disorder is acute or chronic 6. Determine whether the acid-base disorders are appropriately compensated. If compensation is not appropriate the patient has a mixed acid-base disorder
What is the most abundant substance in the body?
Water Water constitutes approximately 50% to 60% of body weight
Which IV fluid is most efficient at expanding the intravascular space? A. Half normal saline B. D5W C. Normal saline D. Lactated ringers
When choosing IV fluids isotonic saline is approximately 3 times more efficient than 5% dextrose in water at expanding the intravascular space
What are the equations for IBW?
Women IBW (lb) = 100 lb for 5 ft in height + 5 lb for each inch over 5 ft Men IBW (lb) = 106 lb for 5 ft in height + 6 lb for each inch over 5 ft
