SM_214a: Hypernatremia

Question 1

____ is a surrogate marker of tonicity

Answer 1

Serum sodium (SNa) is a surrogate marker of tonicity

Question 2

Decrease in total body water leads to _____

Answer 2

Decrease in total body water leads to hypertonic hypernatremia (dehydration)

Question 3

As urine volume increases, plasma osmolarity _____ plasma ADH ______

Answer 3

As urine volume increases, osmolarity decreases and plasma ADH decreases

Question 4

ADH synthesized in the supraoptic and paraventricular nuclei of the hypothalamus is released from the posterior pituitary by signaling of ______ and ______

Answer 4

ADH synthesized in the supraoptic and paraventricular nuclei of the hypothalamus is released from the posterior pituitary by signaling of osmoreceptors in the OVLT responding to changes in plasma tonicity or other neural paths to the brain from non-osmotic stimuli

Question 5

ADH release is more sensitive to _____ than _____ but is exponentially stronger when changes in _____ are greater

Answer 5

ADH release is more sensitive to small increases in plasma tonicity than small decreases in EABV but is exponentially stronger when changes in EABV are greater

Question 6

Sensitivity of ADH release to changes in plasma tonicity _____ as EABV decreases

Answer 6

Sensitivity of ADH release to changes in plasma tonicity increases as EABV decreases

(body protects volume at all costs)

Question 7

Hypertonic hypernatremia is SNa above ____ mEq/L but symptoms arise at SNa above ____ mEq/L

Answer 7

Hypertonic hypernatremia is SNa above 145 mEq/L but symptoms arise at SNa above 160 mEq/L

Question 8

Symptoms of hypertonic hypernatremia are more obvious if hypertonicity develops _____

Answer 8

Symptoms of hypertonic hypernatremia are more obvious if hypertonicity develops quickly

Question 9

Describe the brain response to hypertonic hypernatremia

Answer 9

Brain response to hypertonic hypernatremia

1. Hypertonic state
2. Water loss (high osmolality)
3. Rapid adaptation
4. Accumulation of electrolyes (high osmolality)
5. Slow adaptation
6. Accumulation of organic osmolytes (high osmolality)
7. Proper therapy: slow correction of hypertonic states (< 8 mEq/L/day)

(improper therapy is rapid correction of the hypertonic state)

Question 10

Hypertonicity produces _____, unlike isotonic volume depletion

Answer 10

Hypertonicity produces cellular dehydration, unlike isotonic volume depletion

Question 11

Most dehydration by itself rarely produces recognizable ______

Answer 11

Most dehydration by itself rarely produces recognizable volume depletion

Question 12

Volume depletion or decreased renal solute load impairs _____ in the absence of _____

Answer 12

Volume depletion or decreased renal solute load impairs H₂O diuresis in the absence of ADH

Question 13

Hypertonicity is always associated with _____ in total body water

(apart from exposure to acute hypertonic salt resulting in a dampening shift of total body water from ICF to ECF)

Answer 13

Hypertonicity is always associated with a reduction in total body water

Question 14

Hypertonic hypernatremia (dehydration) is caused by _____ or _____

Answer 14

Hypertonic hypernatremia (dehydration) is caused by receiving hypertonic salt or suffering persistent H₂O losses not replaced by intake

Question 15

Persistent hypertonic hypernatremia indicates _____ or _____ is also a problem

Answer 15

Persistent hypertonic hypernatremia indicates absent thirst or patient access to water is also a problem

Question 16

Hypertonicity is mostly seen in the _____, _____, _____, and _____

Answer 16

Hypertonicity is mostly seen in the elderly, infirm, infants, and those intubated

Question 17

Types of hypertonic hypernatremia include _____, _____, and _____

Answer 17

Types of hypertonic hypernatremia include hypertonic Na gain, polyuric (increased C^efH₂O), and non-polyuric (decreased C^efH₂O)

Question 18

Polyuric hypertonic hypernatremia (increased C^efH₂O) includes _____ and _____

Answer 18

Polyuric hypertonic hypernatremia (increased C^efH₂O) includes solute diuresis and pure H₂O diuresis

Question 19

Pure H₂O diuresis variant of polyuric hypertonic hypernatremia (increased C^efH₂O) includes ______ and ______

Answer 19

Pure H₂O diuresis variant of polyuric hypertonic hypernatremia (increased C^efH₂O) includes central diabetes inspidus and nephrogenic diabetes insipidus

Question 20

Acute exposure to hypertonic Na solutions results in a shift of total body water from ____ to ____, resulting in brain shrinkage, cerebral blood vessel tears, limbic demyelination, elevation of EABV, and acute pulmonary edema

Answer 20

Acute exposure to hypertonic Na solutions results in a shift of total body water from ICF to ECF, resulting in brain shrinkage, cerebral blood vessel tears, limbic demyelination, elevation of EABV, and acute pulmonary edema

Question 21

Describe mechanisms of non-polyuric hypertonic hypernatremia

Answer 21

Mechanisms of non-polyuric hypertonic hypernatremia

• Primary hypodipsia
• Fever and sweating accentuate insensible daily losses
• GI losses from vomiting or osmotic diarrhea are hypotonic
• Failure to replace H₂O and sometimes Na leaves patient dehydrated and/or volume depleted -> increase in ADH -> oliguria (decreased C^efH₂O)

Question 22

Secretory diarrhea produces an _____ that _____

Answer 22

Secretory diarrhea produces an isotonic loss that does NOT result in hypertonicity

Question 23

Polyuria is a caused by _____ or _____

Answer 23

Polyuria is a caused by solute diuresis or pure H₂O diuresis

Question 24

Urine volume is _____

Answer 24

Urine volume is the amount required to excrete a solute load created by diet and metabolism

(no such thing as normal urine volume)

Question 25

Pure water diuresis produces a urine osmolarity of ____ because \_\_\_\_

Answer 25

Pure water diuresis produces a urine osmolarity of 200 mOsm/L because there is less tubular time to remove solutes, such as NaCl, as urine flow rate increases

Question 26

Solute diuresis produces a urine osmolarity of _____ because \_\_\_\_\_

Answer 26

Solute diuresis produces a urine osmolarity of 300-350 mOsm/L because there is less tubular time to remove H₂O

Question 27

Urine losses after pure water diuresis or solute diuresis are relatively ____ rich, leaving the residual total body water \_\_\_\_

Answer 27

Urine losses after pure water diuresis or solute diuresis are relatively H₂O rich, leaving the residual total body water hypertonic (mostly seen in elderly, infants, infirm, intubated)

Question 28

Describe the mechanism of solute diuresis

Answer 28

Mechanism of solute diuresis: glycosuria from diabetes 1. Glucose filtration exceeds proximal tubule reabsorption maximum 2. More H₂O stays in tubular fluid to hydrate residual glucose 3. [Na] decreases 4. Effective transport of Na out of tubule beginning in the ascending limb of loop of Henle through to principal cells expressing ENaCs along the collecting duct decreases 5. Tubular fluid flow rate (polyuria) and solute load increase such that solute washes out interstitial gradient 6. Na uptake by ENaC produces relative electronegativity 7. K loss facilitated, particularly if polyuria persists 8. Hypotonic loss of renal H₂O raises tonicity of residual total body water 9. Thirst ensues 10. Hypernatremia worsens if access to H₂O restricted

Question 29

Central diabetes insipidus involves a ____ effect of reducing ___ on urine osmolality

Answer 29

Central diabetes inspidius involves a dose effect of reducing the number/functionality of ADH-producing neurons on urine osmolality

Question 30

Describe the triphasic pattern of diabetes insipidius after pituitary surgery

Answer 30

Triphasic pattern of diabetes insipidus after pituitary surgery 1. No ADH -\> polyuria 2. All stored ADH release -\> urine volumes return to normal 3. No more space for water to be stored -\> polyuria

Question 31

Describe the mechanism of nephrogenic diabetes insipidus

Answer 31

Question 32

In central diabetes insipidus, the response to desmopressin involves Uosm \_\_\_\_

Answer 32

In central diabetes insipidus, the response to desmopressin involves Uosm rise \> 100%

Question 33

In nephrogenic diabetes insipidus, the response to desmopressin involves _____ in Uosm

Answer 33

In nephrogenic diabetes insipidus, the response to desmopressin involves no increase in Uosm

Question 34

Acute Na intoxication with neurologic symptoms requires administration of water as \_\_\_\_

Answer 34

Acute Na intoxication with neurologic symptoms requires administration of water as D5W

Question 35

If hypertonic hypernatremia results from sweating, GI losses, or solute diuresis, use ___ or \_\_\_\_

Answer 35

If hypertonic hypernatremia results from sweating, GI losses, or solute diuresis, use 0.9% saline or 0.45% saline with potassium (need to replace Na and K in addition to H₂O)

Question 36

Central diabetes insipidus is treated with \_\_\_\_\_\_

Answer 36

Central diabetes insipidus is treated with desmopressin

Question 37

Nephrogenic diabetes insipidus is partially treated with a combination of \_\_\_\_\_, \_\_\_\_\_, and \_\_\_\_\_

Answer 37

Nephrogenic diabetes insipidus is partially treated with a combination of low Na/low protein diet, thiazide diuretics, and NSAIDs

Question 38

While treating hypertonic hypernatremia, you need to add water to compensate for ____ and \_\_\_\_

Answer 38

While treating hypertonic hypernatremia, you need to add water to compensate for insensible water losses and concurrent renal water losses

Question 39

Goal in treatment of hypertonic hypernatremia is to keep the decrease in SNa ____ per day

Answer 39

Goal in treatment of hypertonic hypernatremia is to keep the decrease in SNa ≤ 8 mEq/L per day

Question 40

Describe the complete fluid prescription for hypertonicity

Answer 40

Complete fluid prescription for hypertonicity * Volume: if depleted add 0.9% saline at a safe hourly rate, if overloaded start diuretic * Insensible losses: replace with D5W at safe hourly rate * Tonicity: decrease in SNa from 1 L infusion is [(infused Na + infused K) - SNa] / TBW + 1 L - calculate 24 hour infusion rate to drop SNa 8 mEq/L/day * Urine loss: measure and replace lost UNa + UK and calculate modified C^efH₂O to replace urine water loss * Give H₂O infusion separate from Na