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chapter 47 quiz 5 Electrolyte Imbalance

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171 Questions

What is the classification for severe hyponatremia?

Less than 120 mEq/L

In chronic hypervolemic hyponatremia, what is a recommended way to reduce the neurohumoral influence on water retention?

Angiotensin-converting enzyme (ACE) inhibitors

What should be avoided in hypervolemic hyponatremia as it impairs urinary dilution?


For chronic, asymptomatic hyponatremia, what is recommended to use once the underlying cause is treated?

Loop diuretics

Why should Chronic hyponatremia be treated cautiously with gradual correction?

To avoid central pontine myelinolysis

Which medication can be used as an ADH antagonist in the treatment of hyponatremia?


Why should loop diuretics be preferred over thiazides in hypervolemic hyponatremia?

Thiazides impair urinary dilution

What is the appropriate approach to chronic, asymptomatic hyponatremia?

Treatment of the underlying cause

Why should severe hyponatremia be cautiously treated with gradual correction?

To prevent cerebral water loss and osmotic demyelination

In hypovolemic hyponatremia, what is the purpose of restoring ECF volume with isotonic saline?

To reduce ongoing ADH release

What is the recommended approach for chronic, asymptomatic hyponatremia after treating the underlying cause?

Fluid restriction and use of ADH antagonists

What should be used to excrete free water in hypervolemic hyponatremia once a negative Na+ balance has been achieved?

Loop diuretics

In chronic hypervolemic hyponatremia, what is the first treatment that should be focused on?

Fluid restriction

What is a possible consequence of severe hyponatremia during the perioperative period?

Cardiac arrhythmias

which type of hyponatremia associated with significant perioperative morbidity.

moderate-severe hyponatremia

for accurate diagnosis of hyponatremia we should use?

serum osmolality, TBW status, and urinary Na+

hyponatremia is usually observed in conjunction with ?

reduced osmolality

in which situations, osmolality is normal or raised in hyponatremia?

presence of glucose

pseudohyponatremia is accompanied with ?

normal osmolality

Which treatment option is recommended for hypovolemic hyponatremia?

Isotonic saline

mild preoperative hyponatremia is associated with?

major cardiac events

What is the main physiological mechanism that can lead to postoperative hyponatremia?

Increased pain-related sympathetic activity

Which group is particularly at high risk for neurologic symptoms due to postoperative hyponatremia?

Premenopausal females

What is the typical Na+ level at which elderly women become symptomatic from hyponatremia?

120 mEq/L

What percentage of hyponatremic patients may develop encephalopathy postoperatively?


What is a potential consequence of failure to recognize hyponatremia as a cause of postoperative symptoms?

Development of permanent neurologic sequelae

Why might inadequate treatment of hyponatremia based on fears of causing osmotic demyelination contribute to poor outcomes?

It increases the risk of encephalopathy

Prevention of postoperative hyponatremia should be a key goal of postoperative fluid therapy, based on ?

limiting free water administration

What is the primary reason for terminating surgery if 1000 to 1500 mL of fluid has been absorbed in females?

To avoid hypoosmolar hyponatremia

What is the recommended intravesical pressure limit for endometrial procedures to prevent TURP complications?

70 mm Hg

In severe hypoosmolar hyponatremia with neurologic symptoms, what is the treatment of choice?

Hypertonic saline

What is the purpose of monitoring the patient's neurologic status using regional anesthetic techniques during surgery?

To detect early signs of TURP syndrome

What treatment should be considered if intravascular volume overload is present in a patient?

Administer loop diuretic

What is the preferred treatment when osmolality is normal or slightly decreased in a patient with hyponatremia?


What is the primary cause of TURP syndrome?

Absorption of nonconductive irrigation fluid

Which factor is NOT listed as a risk factor for developing TURP syndrome?

Short duration of resection

What is the recommended replacement for distilled water as an irrigant to prevent TURP syndrome?

Glycerin solution

How can TURP syndrome be prevented during surgery?

Monitoring fluid absorption during the procedure

What should be assessed if a significant amount of irrigation fluid has been absorbed during a TURP procedure?

Neurologic status and Na+ levels

Why is the use of conducting irrigant with bipolar diathermy recommended to prevent TURP syndrome?

To reduce fluid absorption during surgery

during TURP . Early hypervolemia-related hypertension may be followed by profound hypotension as a result of?

increased capillary filtration

by which mechanism Glycine lead to seizures ?

activating NMDA receptor

side effect due to glycine during TURP?

visual disturbance

what is the treatment for the excitatory effects of glycine?


What is the recommended initial rate of hypertonic 3% saline infusion for patients with symptomatic hyponatremia?

1 mL/kg/h

What is the recommended goal of increasing [Na+] when using hypertonic 3% saline for symptomatic hyponatremia treatment?

1 mEq/L/h

What should be primarily focused on in treating chronic, asymptomatic hyponatremia once the underlying cause is addressed?

Fluid restriction

For patients with moderate symptoms of symptomatic hyponatremia, what treatment may be used to increase [Na+] by 1 mEq/L/h for 3 to 4 hours?

Hypertonic 3% saline

What is the primary approach for optimally treating chronic hypervolemic hyponatremia?

Fluid restriction and ADH antagonists

What is a key factor in determining the symptoms of hyponatremia?

Rapid onset of hyponatremia

At what Na+ concentration do symptoms of seizures and coma typically occur?

110 mEq/L

In hypovolemic hyponatremia, why is isotonic saline used for treatment?

To restore ECF volume

What should be considered when treating chronic hyponatremia (>48 hours) due to cerebral compensation?

Gradual correction of sodium levels

Why are sudden increases in osmolality discouraged in the treatment of chronic hyponatremia?

To prevent cerebral edema

What should be tailored when deciding on the treatment for hyponatremia?

Intravascular volume status

what is the initial treatment of Severely symptomatic hyponatremia (coma, seizures, ) of acute onset?

A bolus of 100 mL of 3% saline

What percentage of critically ill patients may develop hypernatremia?


What is the rapid guide to urine osmolality in cases where urgent treatment is being considered?

Urine specific gravity less than 1.005

What is the treatment approach for hypovolemic hypernatremia after correcting the intravascular volume deficit?

Using 0.45% saline to cover the water deficit

What is the major mechanism leading to hypernatremia due to excessive water loss?

Lack of ADH

Which condition is characterized by the excretion of large quantities of inappropriately dilute urine?

Diabetes insipidus

What is the recommended treatment for hypervolemic hypernatremia after stopping exogenous Na+ administration?

Administering furosemide with 5% dextrose

In which circumstances does central DI typically occur?

Pituitary surgery

In central diabetes insipidus with a urine output greater than 250 mL/h, what medication is indicated to reduce urine output?

Desmopressin acetate (DDAVP)

What is the risk associated with administering higher acute doses of desmopressin acetate in central diabetes insipidus?

Risk of water intoxication

What clinical feature is associated with hypernatremia?


How is the diagnosis of hypernatremia typically established?

Analysis of urinary osmolality

What is the appropriate treatment for euvolemic hypernatremia after replacing deficit and ongoing losses?

Administering desmopressin acetate

In which circumstances does nephrogenic DI typically occur?

renal Disease

what is the complication hypernatremia due DI If the patient is unable to accept compensatory fluid orally ?


how hypernatremia is defined ?

[Na] >145 mEq/L, is less common than hyponatremia but may affect up to 10% of critically ill patients.

severe hypernatremia defined as Na more than

[Na] >160 mEq/L

Appropriate hypernatremia Treatment should be

tailored to the intravascular volume status, correction of the Na+ should be no more rapid than 10 mEq/L/day unless the onset has been very acute.

mortality rate due to severe hypernatremia?


what is the diagnosis for : Hypovolemia, TBW ↓↓ TBNa+ ↓. U[Na+] >20 ?

Renal sodium and water loss

what is the diagnosis for : Hypovolemia, TBW ↓↓ TBNa+ ↓. U[Na+] <20 ?

Renal water loss

what is the diagnosis for : Euvolemia, TBW ↓, TBNa+ normal,U[Na+]Variable.

Renal water loss

what is the diagnosis for : Hypervolemia, TBW ↑, TBNa+ ↑↑,U[Na+]>20?

Sodium gains

What is a possible cause of hypokalemia according to the text?

Shift from extracellular to intracellular compartment

What is a potential consequence of using anticoagulated samples for K+ tests?

Lower K+ results

What is the primary mechanism of failure of renal secretion leading to hyperkalemia?

Basolateral Na+/K+ATPase dysfunction

What is a common cause of elevated plasma K+ levels due to sampling artifacts?

Delayed processing of samples

what is the key role of potassium on excitable tissue ?

maintain resting membrane potential

What is a potential consequence of dyskalemia during the perioperative period?

Life-threatening cardiac arrhythmias

What ECG changes are seen with hyperkalemia at K+ levels greater than 7.5 mEq/L?

Widened QRS

In the context of anuric renal failure, what level of hyperkalemia is an indication for acute dialysis?

Greater than 6.5 mEq/L

What is the primary goal of the acute treatment of hyperkalemia?

Shifting K+ from extracellular fluid to intracellular fluid

What is a characteristic feature of chronically induced hyperkalemia, such as in chronic renal failure?

Better tolerance compared to acute increases in K+ concentrations

What is the mechanism of action for eliminating potassium in more chronic cases of hyperkalemia?

Using GI resin exchange

What are the initial ECG changes seen with hyperkalemia when K+ levels are between 5.5 and 6.5 mEq/L?

Tall, peaked T-waves

What are the initial ECG changes seen with hyperkalemia when K+ levels are between 6.5 and 7.5 mEq/L?

prolonged PR interval

What are the initial ECG changes seen with hyperkalemia when K+ levels Greater than 9.0 mEq/L

increased risk for cardiac arrest

Ratios between intracellular and extracellular K+ concentrations in acute hyperkalemia

abnormal with acute hyperkalemia.

What is the primary cause of TURP syndrome?

Absorption of irrigation fluid

HYPOKALEMIA defined as k level less than ?

K<3.5 mEq/L

Moderate-to-severe hypokalemia defined as k Level between ?

2-2.5 mEq/L

Moderate-to-severe hypokalemia (2-2.5 mEq/L) leads to

T wave depression

why Hypokalemia should be pragmatically corrected in the perioperative period to

optimize neuromuscular function and reduce cardiac irritability

treatment is of prime importance when acute arrhythmias exist, and K+ should be maintained at greater than ?

4 to 4.5 mEq/L

during treatment of hypokalemia, speed of the infusion should be

slow enough to allow equilibration throughout the entire ECF

during treatment of hypokalemia, speed of the infusion should be

no faster than 0.4 mEq/ kg/h.

at which concentration the K solution should be given via central venous catheter

more than 40 mEq/L

Treatments for Hyperkalemia: what is the indication for using CaCl2 10% (10 mL) or Calcium gluconate

K+ >6.5 mEq/L, particularly with ECG changes

Treatments for Hyperkalemia: duration of action of CaCl2 10% (10 mL) or Calcium gluconate (Antagonize cardiac toxicity)

30-60 min

Treatments for Hyperkalemia: what is the indication for using “Intracellular potassium shift” insulin

K+ >6.0 mEq/L

Treatments for Hyperkalemia: what is the indication for using “Intracellular potassium shift” NaHCO3 1 mEq/kg

K+ >6.5 mEq/L

Treatments for Hyperkalemia: what is the indication for using “K+ elimination” Kayexalate

sustained hyperkalemia

Treatments for Hyperkalemia: what is the indication for using "Increase renal excretion” Furosemide

Moderate-to-severe hyperkalemia

Which of the following is a symptom characteristic of hypocalcemia?

Trousseau sign

What is a sign of hypocalcemia that involves facial twitching induced by tapping on the facial nerve?

Chvostek sign

In which patient population may ionized hypocalcemia from citrate chelation be particularly severe and prolonged?

Patients with hepatic impairment

What ionized calcium concentration is considered the threshold for specific coagulopathy due to hypocalcemia?

$<$ 1.2 mEq/L

What is the recommended ionized calcium level that should be aimed for in situations requiring supplemental calcium due to hypocalcemia?

$<$ 1.8 mEq/L

Which symptom is NOT characteristic of hypocalcemia?


In critical illness, what circumstance warrants Ca2+ supplementation?


Which symptom is associated with hypercalcemia?

Shortened QT interval

What treatment is recommended for symptomatic hypercalcemia to increase renal Ca2+ excretion?

Loop Diuretics

Which medication could contribute to a mild reduction in Ca2+ levels during the rehydration phase?


What is the purpose of Bisphosphonates in the treatment of severe hypercalcemia?

Enhance osteoclastic bone deposition

Which condition may lead to low Mg2+ levels during hypocalcemia?

Infusion of isotonic saline

What is the recommended IV dose of pamidronate for moderate hypercalcemia?

60 mg

What should be considered before administering Bisphosphonates for hypercalcemia treatment?

Clinical dehydration

When is Calcitonin given in the treatment of hypercalcemia?

To decrease bone resorption

Why might calcium gluconate be preferred for peripheral administration over CaCl2 for hypocalcemia treatment?

Reduced tissue injury upon extravasation

IV calcium gluconate vs CaCl2 for hypocalcemia treatment?

calcium gluconate contains less elemental Ca2+

The causes of hypocalcemia are related to

increased PTH and/or vitamin D activity

when Glucocorticoids indicated as treatment in hypercalcemia?

hypercalcemia associated with lymphoproliferative disease

combination of volume expansion with isotonic saline and loop diuretics. how much It can reduce Calcium level?

1 to 3 mg/dL in 2 to 5 days

in how long time the IV dose of pamidronate 60 mg cam bring claim level to normal?

7 days, and the effect may persist for up to 1 month.

what is the most common cause typically manifests with mild hypercalcemia ?

Primary hyperparathyroidism

What is one of the reasons why serum Mg2+ concentration may be a poor indicator of total body content?

Large distribution in extracellular compartment

Which group of patients are particularly prevalent to hypomagnesemia?

Postoperative cardiac surgery patients

What are some common symptoms associated with hypomagnesemia?

Trousseau and Chvostek signs, vertigo, seizures

What can lead to relative depletion of magnesium in the body?

Athletic activities

How are intraerythrocyte or intralymphocyte Mg2+ levels related to total body and tissue stores?

They are complex to process but give a better approximation

What is one of the cardiovascular manifestations associated with acute hypomagnesemia?

Prolonged PR interval

What is the recommended initial dose of IV Mg2+ in the presence of seizures or acute arrhythmias?

1-2 gm over 5 to 10 minutes

What are the symptoms associated with Mg2+ concentration between 24 to 48 mg/dL?

Diffuse vasodilation with hypotension, bradycardia

What is a key consideration when administering Mg2+ to patients with kidney disease?

Decrease the dose due to renal excretion

Which complication may arise if Mg2+ is used without caution in patients with a background impairment of neuromuscular transmission?

Respiratory paralysis

What is the primary purpose of administering IV Ca2+ during treatment of acute hypermagnesemia?

To antagonize Mg2+ and avoid diuretic-induced hypocalcemia

What is the definitive treatment for hypermagnesemia, especially in the presence of renal disease?

Consider dialysis

what is the magnesium Therapeutic levels in the treatment of preeclampsia

5 to 7 mg/dL

hypomagnesemia are associated with cardiovascular morbidity and are particularly prevalent in diverse hospitalized patients, which patients has the highest risk for hypomagnesemia?

critical care patients

treatment of Asymptomatic patients with moderate-severe hypomagnesemia ?

oral magnesium

what is the indication to start treatment for hypomagnesemia?

asymptomatic Patients with Mg2+ concentration of less than 1 mg/dL

symptoms of hypomagnesemia often relate to common coexisting ?

hypocalcemia or hypokalemia

hypomagnesemia usually present with hypocalcemia, hypokalemia, or both which also should also be treated? which one should be treated first ?


What are the symptoms associated with Mg2+ concentration between 5 to 10 mg/dL?

Impaired cardiac conduction

what is the main cause of HYPERMAGNESEMIA


What may precipitate symptoms of hypophosphatemia in patients with chronic depletion?


What metabolic change leads to intracellular electrolyte depletion particularly phosphate despite normal plasma levels during starvation?

Increased insulin secretion

What phenomenon leads to profound hypophosphatemia as a result of refeeding after a period of prolonged starvation?

Carbohydrate metabolism shift

Which disorder may be observed on commencement of nutrition after prolonged starvation and could manifest postoperatively?

Refeeding syndrome

symptoms of severe hypophosphatemia (<1.5 mg/dL), may include

leukocyte dysfunction

during hypophosphatemia , IV PO43− replacement carries a risk for precipitating

severe hypocalcemia

indications of IV PO43− replacement therapy during hypophosphatemia

moderate-severe hypophosphatemia

IV PO43− replacement for hypophosphatemia. protocols should be based on ?

patient weight and serum PO43-.

what is the most common cause in clinical practice for HYPERPHOSPHATEMIA?

renal failure

HYPERPHOSPHATEMIA due to renal failure

in more severe kidney disease hyperphosphatemia must be controlled with oral PO43− binders.

The features of hyperphosphatemia may be related to


what is the effect on phosphate and calcium due to increased PTH secretion

decrease serum phosphate and increase serum calcium

Hypocalcemia due to hyperphosphatemia is mediated via

Ca+ deposition in soft tissues

hypophosphatemia cause by?

Respiratory alkalosis

hyperphosphatemia caused by?


How does exogenous Cl− administration from isotonic saline affect the plasma SID and therefore pH?

Decreases plasma SID and lowers pH

In disease states with hyperchloremia and hypernatremia, what impact do they have on the plasma SID and pH?

Do not affect plasma SID or pH

What should initial investigation and treatment of 'matched' electrolyte imbalances target?

Correcting the dysnatremia

Which electrolyte imbalances can affect acid-base balance according to the text?

Hyperchloremia and hyponatremia

Causes and Mechanisms of Chloride Abnormalities- HYPOCHLOREMIA

Chronic respiratory acidosis

Causes and Mechanisms of Chloride Abnormalities- HYPERCHLOREMIA


Study Notes

Chloride Disorders

  • Hypernatremia: [Na+] >145 mEq/L, less common than hyponatremia, affecting up to 10% of critically ill patients
    • Causes: excessive water loss, inadequate compensatory intake, lack of ADH, administration of exogenous sodium
    • Symptoms: altered mental status, lethargy, irritability, seizures, hyperreflexia, spasticity
    • Diagnosis: assessment of intravascular volume status, urinary osmolality, and Na+ concentration
    • Treatment: tailored to intravascular volume status, correction of Na+ concentration no more rapid than 10 mEq/L/day
  • Hypochloremia and hyponatremia do not affect SID or pH
  • Causes of Cl– abnormalities: matched electrolyte imbalances, targeting dysnatremia first

Magnesium Disorders

  • Hypomagnesemia: associated with cardiovascular morbidity, prevalent in hospitalized patients (12% of general inpatients, 19% of preoperative cardiac surgery patients, 65% of critical care patients)
    • Causes: reduced Mg intake, increased renal losses, relative depletion in times of increased cell turnover and protein production
    • Symptoms: nonspecific; relate to coexisting hypocalcemia or hypokalemia
    • Treatment: tailored to severity of symptoms and degree of hypomagnesemia, asymptomatic patients receive oral supplementation, IV Mg2+ for symptoms or Mg2+ <1 mg/dL
  • Hypermagnesemia: typically iatrogenic, caused by excessive Mg2+ administration
    • Symptoms: reflect effect on neurologic and cardiac function, relate to serum Mg2+ levels
    • Treatment: promote renal excretion, IV Ca2+ to antagonize Mg2+, definitive treatment may require dialysis

Potassium Disorders

  • Hyperkalemia: may result from excess intake, failed excretion, or shift from ICF to ECF
    • Symptoms: muscle weakness, paralysis, altered cardiac conduction, ECG changes
    • Treatment: shifting K+ from ECF to ICF, antagonizing cardiac toxicity with Ca2+, increasing renal excretion, GI resin exchange
  • Hypokalemia: may result from excess intake, failed secretion, or shift from ECF to ICF
    • Causes: impaired principal cell function in the cortical collecting duct, hypomagnesemia, refeeding syndrome
    • Symptoms: muscle weakness, paralysis, altered cardiac conduction
    • Treatment: correction of underlying cause, potassium supplementation

Calcium Disorders

  • Hypocalcemia: related to reduced PTH and/or vitamin D activity, increased bone deposition, Ca2+ chelation, or changes in binding protein concentration or ionized fraction
    • Symptoms: neuromuscular irritability, circumoral and peripheral paresthesia, Chvostek sign, Trousseau sign, muscle cramps, laryngospasm, tetany, seizures
    • Treatment: addressing underlying cause, correcting ionized Ca2+, supporting cardiac inotropy and neuromuscular function
  • Hypercalcemia: occurs when ECF Ca2+ influx from GI tract and/or bone outweighs efflux to bone or excretion via kidneys
    • Symptoms: neurologic symptoms, GI symptoms, renal manifestations, ECG abnormalities, potentiation of digoxin toxicity
    • Treatment: addressing underlying cause, increasing renal Ca2+ excretion with isotonic saline and loop diuretics, bisphosphonates, glucocorticoids, calcitonin

Phosphate Disorders

  • Hypophosphatemia: related to impaired enteral uptake, increased renal excretion, or shifts to the cellular compartment or bone
    • Symptoms: precipitated by hyperventilation in patients with chronic depletion
    • Treatment: addressing underlying cause, correcting phosphate levels
  • Hypermagnesemia: not mentioned

Sodium Disorders

  • Hyponatremia: may be present preoperatively, develop as a consequence of perioperative events, or both

    • Classification: mild (130-134 mEq/L), moderate (120-130 mEq/L), severe (<120 mEq/L)
    • Symptoms: unusual due to cerebral compensation for hypoosmolar state
    • Treatment: depends on underlying cause, hypovolemic hyponatremia requires ECF volume restoration, hypervolemic hyponatremia requires fluid restriction and optimization of underlying disease state### Hyponatremia
  • Classified as mild (130-134 mEq/L), moderate (120-130 mEq/L), or severe (<120 mEq/L or 48 hours or of unknown duration)

  • Treatment of chronic hyponatremia (>48 hours or of unknown duration) should be cautious to avoid cerebral compensation for the hypoosmolar state, leading to cerebral water loss and osmotic demyelination

Hypovolemic Hyponatremia

  • Symptoms are unusual due to osmotic shifts in the brain being limited by the loss of both Na+ and water
  • ECF volume should be restored with isotonic saline, which will also reduce ongoing ADH release

Hypervolemic Hyponatremia

  • In chronic cases, focus on restricting water intake and optimizing the underlying disease state, such as improving cardiac output with ACE inhibitors to reduce neurohumoral influence on water retention in cardiac failure
  • Loop diuretics can be used to excrete free water once a negative Na+ balance has been achieved

Chronic, Asymptomatic Hyponatremia

  • No immediate correction of hyponatremia is required, and the underlying cause should be treated
  • Fluid restriction, ADH antagonists (lithium, demeclocycline), and loop diuretics may be used

Postoperative Hyponatremia

  • The surgical stress response, aggravated by hypotension and pain-related or physiologic stress-related sympathetic activity, can lead to a state of Na+ and water retention similar to SIADH
  • Incidence of postoperative hyponatremia is 1% to 5%, with children and premenopausal females at high risk for neurologic symptoms
  • Symptoms and neurologic sequelae may occur at Na+ levels as high as 128 mEq/L in these groups

Symptomatic Hyponatremia

  • Typically euvolemic or hypervolemic
  • In patients with moderate symptoms (confusion, lethargy, nausea, and vomiting), hypertonic 3% saline may be used at an initial rate of 1 mL/kg/h to increase [Na+] by 1 mEq/L/h for 3 to 4 hours
  • Infusion rate should be modified to ensure that [Na+] is increased by no more than 10 mEq/L in the first 24 hours of treatment

Explore the diagnosis, classification, and treatment of hyponatremia disorders in the perioperative setting. Learn about the risks of sudden increases in osmolality and potential complications such as osmotic demyelination.

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