Renal Clinical Medicine Part 2: Electrolytes (M. Selby) Flashcards
Hyponatremia is defined by?
Serum sodium less than 135 mEq/L
Serum osmolarity is regulated by what 2 main systems?
1) ADH system
2) Thirst mechanism
ADH is released in response to?
Osmotic and non-osmotic stimuli
ADH released from increases in serum osmolarity is detected by what receptors in the anterior hypothalamus?
ADH released from non-osmotic stimuli such as decreases in blood pressure or blood volume is detected by?
1) Osmoreceptors
2) Arterial baroreceptors
Besides baroreceptors, what are additional non-osmotic stimuli for ADH release?
1) Nausea
2) Hypoxia
3) Pain
4) Medications (Opiates and antidepressants)
Hyponatremia results primarily from?
Increases in total body water
Increases in total body water results from either?
1) Excessive intake of water
2) Decreased renal excretion of water
Acute Hyponatremia is classified as?
Chronic?
1) Less than 48 hours
2) More than 48 hours or unknown duration
If the patient has hypotonic hyponatremia, then what needs to be assessed?
How is this done?
If considering SIADH what else should be obtained?
1) Volume status of the patient
2) Measure random urine sodium level and urine osmolarity
3) Serum uric acid (Low levels indicated SIADH)
What is the most common malignancy associated with ectopic ADH production?
Small cell lung cancer
How is hyponatremia treated in symptomatic patients?
Hypertonic saline (3%)
When treating chronic hyponatremia you must be careful of rapid correction of serum sodium as patient is at higher risk for?
Osmotic demyelination syndrome
What are some complications of hyponatremia?
1) Seizures
2) Coma
3) Death from brain (uncal) herniation
4) Osmotic demyelination syndrome
The clinical manifestations of Osmotic demyelination syndrome are typically delayed for how long after rapid Na+ correction?
Demyelination occurs in what neurons?
What symptom which may occur is characterized as the patient being awake but unable to move or talk?
Although it may take up to 4 weeks for abnormalities to be seen, what is the prefered imaging modality?
1) 2-6 days
2) Pontine and extrapontine neurons
3) Locked in syndrome
4) MRI
What is a common underlying disease state predisposing to the occurence of osmotic myelinolysis?
Chronic alcoholism
Hypernatremia is defined by?
Serum sodium greater than 145 mEq/L
Hypernatremia is primarily seen in what populations?
1) Infants
2) Elderly
What are the two ways that hypernatremia can occur?
Which is the most common cause?
1) Dehydration (More common)
2) Sodium overload
What does hypernatremia result in with regards to the osmotic gradient?
Cellular shrinkage
The clinical manifestations of hypernatremia are mainly?
Neurologic symptoms
Acute hypernatremia is classified as?
Chronic?
1) Less than 48 hours
2) More than 48 hours or unknown duration
Intracerebral hemorrhages, Subarachnoid hemorrhages, or Subdural hematomas due to hypernatremia are more common in what populations?
Pediatric and neonate
When treating chronic hypernatremia you must be careful of rapid correction of serum sodium as patient is at higher risk for?
Cerebral edema
The kidneys are the primary regulator of what ion?
Potassium
What is the major extracellular cation?
What is the major intracellular cation?
1) Potassium
2) Sodium
The regulation of potassium homeostasis by the kidneys is done primarily by?
Secretion of K+ in the distal parts of nephron
Hyperkalemia is defined by?
Serum potassium greater 5.0 mEq/L
What cardiac arrhythmias are associated with hyperkalemia complications?
1) Vfib
2) Bradycardia from AV block
3) Asystole
Severe hyperkalemia can lead to respiratory failure from?
Diaphragm weakness
Hyperkalemia decreases ammoniagenesis and thus decreases?
This leads to?
1) Ammonium chloride excretion in the kidneys
2) Metabolic acidosis
What are the 2 main reasons for hyperkalemia?
1) Transcellular shift (increased K+ release from cells)
2) Decreased Renal K+ excretion
In the pathogenesis of hyperkalemia, Pseudohyperkalemia, Metabolic Acidosis, Insulin deficiency, hyperglycemia, hyperosmolality, Increased Tissue Catabolism, Medications, exercise and blood transfusions all lead to?
Transcellular shift (increased K+ release from cells)
Pseudohyperkalemia results from?
What are some causes of this?
1) An artificial increase in serum K+ due to K+ release from cells
2) RBC hemolysis, Clotted blood samples, Leukocytosis
In the pathogenesis of hyperkalemia, decreased renal K+ excretions can be caused by?
1) Low aldosterone secretion
2) Aldosterone resistance
3) AKI or CKD
In the diagnosis of hyperkalemia, how do you determine if it is due to renal or extrarenal etiology?
What indicates renal etiology?
What indicated extrarenal?
1) Fractional excretion of K+
2) Less than 10%
2) Greater than 10%
What ecg findings should lead you to give calcium gluconate in order to treat hyperkalemia?
Peaked T wave
What is the regimen for treating hyperkalemia due to transcellular shift?
1) Insulin
2) Dextrose
3) B2-agonist
In the treatment of hyperkalemia, sodium polystyrene sulfonate works by?
Zirconium cyclosilicate?
Patiromer?
1) Exchanges Na+ ions for potassium primarily in the colon
2) Exchanges Na+ and H+ ions for potassium throughout intestines
3) Exchanges Ca+ for potassium primarily in the colon
Hypokalemia is defined by?
Serum potassium less than 3.5 mEq/L
What are the clinical manifestations of hypokalemia?
1) Cardiac arrhythmia (PAC/PVCs)
2) Skeletal muscle weakness (diaphragmatic weakness)
3) Rhabdomyolysis
4) Metabolic alkalosis
5) Nephrogenic diabetes insipidus
What ECG change in common with hypokalemia?
Prominent U wave
What are the 3 main reasons for hypokalemia?
1) Transcellular shift (Increased K+ uptake by cells)
2) Extrarenal loss
3) Renal loss
In the pathogenesis of hypokalemia, transcellular shift (increased K+ uptake by cells) can be caused by?
1) Insulin
2) B2 agonist
3) Metabolic alkalosis
In the pathogenesis of hypokalemia, extrarenal loss can be caused by?
1) GI loss (Vomiting and Diarrhea)
2) Cutaneous loss (sweating)
In the pathogenesis of hypokalemia, renal loss can be caused by?
1) Diuretics
2) Increased mineralocorticoid activity
3) Hypomagnesemia
What are some examples of increased mineralocorticoid activity?
1) Primary hyperaldosteronism (Conn’s syndrome)
2) Hypercortisolism (Cushing Syndrome)
In the diagnosis of hypokalemia, what is the best method for assessing renal K+ excretion?
24 hour urine potassium
In the treatment of hypokalemia what is given to replace potassium deficit?
Potassium chloride
