chapter 47 quiz 5 Electrolyte Imbalance

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Questions and Answers

What is the classification for severe hyponatremia?

48 hours or unknown duration

120-130 mEq/L

Less than 120 mEq/L (correct)

130-134 mEq/L

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

Fluid restriction

Angiotensin-converting enzyme (ACE) inhibitors (correct)

Loop diuretics

Thiazides

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

Thiazides (correct)

Fluid restriction

Isotonic saline

Loop diuretics

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

Loop diuretics Signup and view all the answers

Why should Chronic hyponatremia be treated cautiously with gradual correction?

To avoid central pontine myelinolysis Signup and view all the answers

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

Lithium Signup and view all the answers

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

Thiazides impair urinary dilution Signup and view all the answers

What is the appropriate approach to chronic, asymptomatic hyponatremia?

Treatment of the underlying cause Signup and view all the answers

Why should severe hyponatremia be cautiously treated with gradual correction?

To prevent cerebral water loss and osmotic demyelination Signup and view all the answers

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

To reduce ongoing ADH release Signup and view all the answers

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

Fluid restriction and use of ADH antagonists Signup and view all the answers

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

Loop diuretics Signup and view all the answers

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

Fluid restriction Signup and view all the answers

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

Cardiac arrhythmias Signup and view all the answers

which type of hyponatremia associated with significant perioperative morbidity.

moderate-severe hyponatremia Signup and view all the answers

for accurate diagnosis of hyponatremia we should use?

serum osmolality, TBW status, and urinary Na+ Signup and view all the answers

hyponatremia is usually observed in conjunction with ?

reduced osmolality Signup and view all the answers

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

presence of glucose Signup and view all the answers

pseudohyponatremia is accompanied with ?

normal osmolality Signup and view all the answers

Which treatment option is recommended for hypovolemic hyponatremia?

Isotonic saline Signup and view all the answers

mild preoperative hyponatremia is associated with?

major cardiac events Signup and view all the answers

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

Increased pain-related sympathetic activity Signup and view all the answers

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

Premenopausal females Signup and view all the answers

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

120 mEq/L Signup and view all the answers

What percentage of hyponatremic patients may develop encephalopathy postoperatively?

8% Signup and view all the answers

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

Development of permanent neurologic sequelae Signup and view all the answers

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

It increases the risk of encephalopathy Signup and view all the answers

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

limiting free water administration Signup and view all the answers

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

To avoid hypoosmolar hyponatremia Signup and view all the answers

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

70 mm Hg Signup and view all the answers

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

Hypertonic saline Signup and view all the answers

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

To detect early signs of TURP syndrome Signup and view all the answers

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

Administer loop diuretic Signup and view all the answers

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

Hemodialysis Signup and view all the answers

What is the primary cause of TURP syndrome?

Absorption of nonconductive irrigation fluid Signup and view all the answers

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

Short duration of resection Signup and view all the answers

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

Glycerin solution Signup and view all the answers

How can TURP syndrome be prevented during surgery?

Monitoring fluid absorption during the procedure Signup and view all the answers

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

Neurologic status and Na+ levels Signup and view all the answers

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

To reduce fluid absorption during surgery Signup and view all the answers

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

increased capillary filtration Signup and view all the answers

by which mechanism Glycine lead to seizures ?

activating NMDA receptor Signup and view all the answers

side effect due to glycine during TURP?

visual disturbance Signup and view all the answers

what is the treatment for the excitatory effects of glycine?

magnesium Signup and view all the answers

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

1 mL/kg/h Signup and view all the answers

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

1 mEq/L/h Signup and view all the answers

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

Fluid restriction Signup and view all the answers

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 Signup and view all the answers

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

Fluid restriction and ADH antagonists Signup and view all the answers

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

Rapid onset of hyponatremia Signup and view all the answers

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

110 mEq/L Signup and view all the answers

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

To restore ECF volume Signup and view all the answers

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

Gradual correction of sodium levels Signup and view all the answers

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

To prevent cerebral edema Signup and view all the answers

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

Intravascular volume status Signup and view all the answers

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

A bolus of 100 mL of 3% saline Signup and view all the answers

What percentage of critically ill patients may develop hypernatremia?

10% Signup and view all the answers

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

Urine specific gravity less than 1.005 Signup and view all the answers

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

Using 0.45% saline to cover the water deficit Signup and view all the answers

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

Lack of ADH Signup and view all the answers

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

Diabetes insipidus Signup and view all the answers

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

Administering furosemide with 5% dextrose Signup and view all the answers

In which circumstances does central DI typically occur?

Pituitary surgery Signup and view all the answers

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

Desmopressin acetate (DDAVP) Signup and view all the answers

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

Risk of water intoxication Signup and view all the answers

What clinical feature is associated with hypernatremia?

Hyperreflexia Signup and view all the answers

How is the diagnosis of hypernatremia typically established?

Analysis of urinary osmolality Signup and view all the answers

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

Administering desmopressin acetate Signup and view all the answers

In which circumstances does nephrogenic DI typically occur?

renal Disease Signup and view all the answers

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

hypovolemia Signup and view all the answers

how hypernatremia is defined ?

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

severe hypernatremia defined as Na more than

[Na] >160 mEq/L Signup and view all the answers

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. Signup and view all the answers

mortality rate due to severe hypernatremia?

75% Signup and view all the answers

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

Renal sodium and water loss Signup and view all the answers

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

Renal water loss Signup and view all the answers

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

Renal water loss Signup and view all the answers

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

Sodium gains Signup and view all the answers

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

Shift from extracellular to intracellular compartment Signup and view all the answers

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

Lower K+ results Signup and view all the answers

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

Basolateral Na+/K+ATPase dysfunction Signup and view all the answers

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

Delayed processing of samples Signup and view all the answers

what is the key role of potassium on excitable tissue ?

maintain resting membrane potential Signup and view all the answers

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

Life-threatening cardiac arrhythmias Signup and view all the answers

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

Widened QRS Signup and view all the answers

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

Greater than 6.5 mEq/L Signup and view all the answers

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

Shifting K+ from extracellular fluid to intracellular fluid Signup and view all the answers

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

Better tolerance compared to acute increases in K+ concentrations Signup and view all the answers

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

Using GI resin exchange Signup and view all the answers

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 Signup and view all the answers

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

prolonged PR interval Signup and view all the answers

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

increased risk for cardiac arrest Signup and view all the answers

Ratios between intracellular and extracellular K+ concentrations in acute hyperkalemia

abnormal with acute hyperkalemia. Signup and view all the answers

What is the primary cause of TURP syndrome?

Absorption of irrigation fluid Signup and view all the answers

HYPOKALEMIA defined as k level less than ?

K<3.5 mEq/L Signup and view all the answers

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

2-2.5 mEq/L Signup and view all the answers

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

T wave depression Signup and view all the answers

why Hypokalemia should be pragmatically corrected in the perioperative period to

optimize neuromuscular function and reduce cardiac irritability Signup and view all the answers

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

4 to 4.5 mEq/L Signup and view all the answers

during treatment of hypokalemia, speed of the infusion should be

slow enough to allow equilibration throughout the entire ECF Signup and view all the answers

during treatment of hypokalemia, speed of the infusion should be

no faster than 0.4 mEq/ kg/h. Signup and view all the answers

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

more than 40 mEq/L Signup and view all the answers

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 Signup and view all the answers

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

30-60 min Signup and view all the answers

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

K+ >6.0 mEq/L Signup and view all the answers

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

K+ >6.5 mEq/L Signup and view all the answers

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

sustained hyperkalemia Signup and view all the answers

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

Moderate-to-severe hyperkalemia Signup and view all the answers

Which of the following is a symptom characteristic of hypocalcemia?

Trousseau sign Signup and view all the answers

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

Chvostek sign Signup and view all the answers

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

Patients with hepatic impairment Signup and view all the answers

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

$<$ 1.2 mEq/L Signup and view all the answers

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

$<$ 1.8 mEq/L Signup and view all the answers

Which symptom is NOT characteristic of hypocalcemia?

Hypertension Signup and view all the answers

In critical illness, what circumstance warrants Ca2+ supplementation?

Hypoalbuminemia Signup and view all the answers

Which symptom is associated with hypercalcemia?

Shortened QT interval Signup and view all the answers

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

Loop Diuretics Signup and view all the answers

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

Calcitonin Signup and view all the answers

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

Enhance osteoclastic bone deposition Signup and view all the answers

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

Infusion of isotonic saline Signup and view all the answers

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

60 mg Signup and view all the answers

What should be considered before administering Bisphosphonates for hypercalcemia treatment?

Clinical dehydration Signup and view all the answers

When is Calcitonin given in the treatment of hypercalcemia?

To decrease bone resorption Signup and view all the answers

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

Reduced tissue injury upon extravasation Signup and view all the answers

IV calcium gluconate vs CaCl2 for hypocalcemia treatment?

calcium gluconate contains less elemental Ca2+ Signup and view all the answers

The causes of hypocalcemia are related to

increased PTH and/or vitamin D activity Signup and view all the answers

when Glucocorticoids indicated as treatment in hypercalcemia?

hypercalcemia associated with lymphoproliferative disease Signup and view all the answers

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 Signup and view all the answers

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. Signup and view all the answers

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

Primary hyperparathyroidism Signup and view all the answers

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

Large distribution in extracellular compartment Signup and view all the answers

Which group of patients are particularly prevalent to hypomagnesemia?

Postoperative cardiac surgery patients Signup and view all the answers

What are some common symptoms associated with hypomagnesemia?

Trousseau and Chvostek signs, vertigo, seizures Signup and view all the answers

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

Athletic activities Signup and view all the answers

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

They are complex to process but give a better approximation Signup and view all the answers

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

Prolonged PR interval Signup and view all the answers

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 Signup and view all the answers

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

Diffuse vasodilation with hypotension, bradycardia Signup and view all the answers

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

Decrease the dose due to renal excretion Signup and view all the answers

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

Respiratory paralysis Signup and view all the answers

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

To antagonize Mg2+ and avoid diuretic-induced hypocalcemia Signup and view all the answers

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

Consider dialysis Signup and view all the answers

what is the magnesium Therapeutic levels in the treatment of preeclampsia

5 to 7 mg/dL Signup and view all the answers

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 Signup and view all the answers

treatment of Asymptomatic patients with moderate-severe hypomagnesemia ?

oral magnesium Signup and view all the answers

what is the indication to start treatment for hypomagnesemia?

asymptomatic Patients with Mg2+ concentration of less than 1 mg/dL Signup and view all the answers

symptoms of hypomagnesemia often relate to common coexisting ?

hypocalcemia or hypokalemia Signup and view all the answers

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

hypomagnesemia Signup and view all the answers

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

Impaired cardiac conduction Signup and view all the answers

what is the main cause of HYPERMAGNESEMIA

iatrogenic Signup and view all the answers

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

Hyperventilation Signup and view all the answers

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

Increased insulin secretion Signup and view all the answers

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

Carbohydrate metabolism shift Signup and view all the answers

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

Refeeding syndrome Signup and view all the answers

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

leukocyte dysfunction Signup and view all the answers

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

severe hypocalcemia Signup and view all the answers

indications of IV PO43− replacement therapy during hypophosphatemia

moderate-severe hypophosphatemia Signup and view all the answers

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

patient weight and serum PO43-. Signup and view all the answers

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

renal failure Signup and view all the answers

HYPERPHOSPHATEMIA due to renal failure

in more severe kidney disease hyperphosphatemia must be controlled with oral PO43− binders. Signup and view all the answers

The features of hyperphosphatemia may be related to

hypocalcemia Signup and view all the answers

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

decrease serum phosphate and increase serum calcium Signup and view all the answers

Hypocalcemia due to hyperphosphatemia is mediated via

Ca+ deposition in soft tissues Signup and view all the answers

hypophosphatemia cause by?

Respiratory alkalosis Signup and view all the answers

hyperphosphatemia caused by?

Rhabdomyolysis Signup and view all the answers

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

Decreases plasma SID and lowers pH Signup and view all the answers

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 Signup and view all the answers

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

Correcting the dysnatremia Signup and view all the answers

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

Hyperchloremia and hyponatremia Signup and view all the answers

Causes and Mechanisms of Chloride Abnormalities- HYPOCHLOREMIA

Chronic respiratory acidosis Signup and view all the answers

Causes and Mechanisms of Chloride Abnormalities- HYPERCHLOREMIA

Diarrhea Signup and view all the answers

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

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Description

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.