SM_214a: Hypernatremia Flashcards
____ is a surrogate marker of tonicity
Serum sodium (SNa) is a surrogate marker of tonicity
Decrease in total body water leads to _____
Decrease in total body water leads to hypertonic hypernatremia (dehydration)
As urine volume increases, plasma osmolarity _____ plasma ADH ______
As urine volume increases, osmolarity decreases and plasma ADH decreases
ADH synthesized in the supraoptic and paraventricular nuclei of the hypothalamus is released from the posterior pituitary by signaling of ______ and ______
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
ADH release is more sensitive to _____ than _____ but is exponentially stronger when changes in _____ are greater
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
Sensitivity of ADH release to changes in plasma tonicity _____ as EABV decreases
Sensitivity of ADH release to changes in plasma tonicity increases as EABV decreases
(body protects volume at all costs)
Hypertonic hypernatremia is SNa above ____ mEq/L but symptoms arise at SNa above ____ mEq/L
Hypertonic hypernatremia is SNa above 145 mEq/L but symptoms arise at SNa above 160 mEq/L
Symptoms of hypertonic hypernatremia are more obvious if hypertonicity develops _____
Symptoms of hypertonic hypernatremia are more obvious if hypertonicity develops quickly
Describe the brain response to hypertonic hypernatremia
Brain response to hypertonic hypernatremia
- Hypertonic state
- Water loss (high osmolality)
- Rapid adaptation
- Accumulation of electrolyes (high osmolality)
- Slow adaptation
- Accumulation of organic osmolytes (high osmolality)
- Proper therapy: slow correction of hypertonic states (< 8 mEq/L/day)
(improper therapy is rapid correction of the hypertonic state)
Hypertonicity produces _____, unlike isotonic volume depletion
Hypertonicity produces cellular dehydration, unlike isotonic volume depletion
Most dehydration by itself rarely produces recognizable ______
Most dehydration by itself rarely produces recognizable volume depletion
Volume depletion or decreased renal solute load impairs _____ in the absence of _____
Volume depletion or decreased renal solute load impairs H2O diuresis in the absence of ADH
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)
Hypertonicity is always associated with a reduction in total body water
Hypertonic hypernatremia (dehydration) is caused by _____ or _____
Hypertonic hypernatremia (dehydration) is caused by receiving hypertonic salt or suffering persistent H2O losses not replaced by intake
Persistent hypertonic hypernatremia indicates _____ or _____ is also a problem
Persistent hypertonic hypernatremia indicates absent thirst or patient access to water is also a problem
Hypertonicity is mostly seen in the _____, _____, _____, and _____
Hypertonicity is mostly seen in the elderly, infirm, infants, and those intubated
Pure H2O diuresis variant of polyuric hypertonic hypernatremia (increased CefH2O) includes ______ and ______
Pure H2O diuresis variant of polyuric hypertonic hypernatremia (increased CefH2O) includes central diabetes inspidus and nephrogenic diabetes insipidus
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
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
Describe mechanisms of non-polyuric hypertonic hypernatremia
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 CefH2O)
Polyuria is a caused by _____ or _____
Polyuria is a caused by solute diuresis or pure H2O diuresis
Urine volume is _____
Urine volume is the amount required to excrete a solute load created by diet and metabolism
(no such thing as normal urine volume)
Pure water diuresis produces a urine osmolarity of ____ because ____
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
Solute diuresis produces a urine osmolarity of _____ because _____
Solute diuresis produces a urine osmolarity of 300-350 mOsm/L because there is less tubular time to remove H2O
Urine losses after pure water diuresis or solute diuresis are relatively ____ rich, leaving the residual total body water ____
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)
Describe the mechanism of solute diuresis
Mechanism of solute diuresis: glycosuria from diabetes
- Glucose filtration exceeds proximal tubule reabsorption maximum
- More H2O stays in tubular fluid to hydrate residual glucose
- [Na] decreases
- 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
- Tubular fluid flow rate (polyuria) and solute load increase such that solute washes out interstitial gradient
- Na uptake by ENaC produces relative electronegativity
- K loss facilitated, particularly if polyuria persists
- Hypotonic loss of renal H2O raises tonicity of residual total body water
- Thirst ensues
- Hypernatremia worsens if access to H2O restricted
Central diabetes insipidus involves a ____ effect of reducing ___ on urine osmolality
Central diabetes inspidius involves a dose effect of reducing the number/functionality of ADH-producing neurons on urine osmolality
Describe the triphasic pattern of diabetes insipidius after pituitary surgery
Triphasic pattern of diabetes insipidus after pituitary surgery
- No ADH -> polyuria
- All stored ADH release -> urine volumes return to normal
- No more space for water to be stored -> polyuria
Describe the mechanism of nephrogenic diabetes insipidus
In central diabetes insipidus, the response to desmopressin involves Uosm ____
In central diabetes insipidus, the response to desmopressin involves Uosm rise > 100%
In nephrogenic diabetes insipidus, the response to desmopressin involves _____ in Uosm
In nephrogenic diabetes insipidus, the response to desmopressin involves no increase in Uosm
Acute Na intoxication with neurologic symptoms requires administration of water as ____
Acute Na intoxication with neurologic symptoms requires administration of water as D5W
If hypertonic hypernatremia results from sweating, GI losses, or solute diuresis, use ___ or ____
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)
Central diabetes insipidus is treated with ______
Central diabetes insipidus is treated with desmopressin
Nephrogenic diabetes insipidus is partially treated with a combination of _____, _____, and _____
Nephrogenic diabetes insipidus is partially treated with a combination of low Na/low protein diet, thiazide diuretics, and NSAIDs
While treating hypertonic hypernatremia, you need to add water to compensate for ____ and ____
While treating hypertonic hypernatremia, you need to add water to compensate for insensible water losses and concurrent renal water losses
Goal in treatment of hypertonic hypernatremia is to keep the decrease in SNa ____ per day
Goal in treatment of hypertonic hypernatremia is to keep the decrease in SNa ≤ 8 mEq/L per day
Describe the complete fluid prescription for hypertonicity
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 CefH2O to replace urine water loss
- Give H2O infusion separate from Na
