lecture 50 - Hypernatremia Flashcards
What is the most influential drier behind ADH secretion?
Hypovolemia»_space; Hyperosmolarity
defense of ECF Volume
how is volume sensed?
3 Players involved
Baro-receptors of the atrium and carotid sinus
Catecholamines – increase Na reabsorption
RAS –
ADH
defense of Osmolality
how is osmolality detected?
2 Players in the defense of osmolality
anterior hypothalamus (SON)
Central Axis – thirst
ADH -
where is ADH made?
where is it stored ?
Synthesis: made in the SON and PVN
Stored: Posterior Pituitary
Non osmotic regulators of ADH
Nausea, Post operative pain, pregnancy
Hypovolemic Hypernatremia -
describe the scenario-
How do you differentiate between renal vs non renal losses of H2O?
scenario: Patient has lost Na, but has lost even more Water;
The patient is dehydrated and Intravascular volume depleted
UNa –
If the kidney is working appropriately, in the setting of hypovolemia, it should be reabsorbing Na and H2O
Renal Losses: UNa > 20
Non Renal: UNa < 20
Causes of Non Renal Losses leading to Hypovolemic Hypernatremia
® Excessive sweating, burns, fevers, diarrhea, fistulas
Causes of Renal Losses leading to Hypovolemic Hypernatremia
Diurectics, Intrinsic renal disease
○ Euvolemic Hypernatremia
describe the scenario:
what will be the Una
Loss of water with normal Body Sodium;
U NA will be variable
○ Euvolemic Hypernatremia
- renal losses
- extra renal losses
Renal Losses: Nephrogenic DI (kidney unable to respond to ADH)
Extra renal losses: Insensible losses (water vapor loss through skin and breath)
Hypodipsia
Central DI
HyperVolemic Hypernatremia
describe the scenario
causes:
Excess Na in the setting of normal or only slight gain of water
Hypertonic Infusion – Normal Saline or Na Bicarb
Hypertonic Dialysis
Patient is eating a lot of salt tablets
Patients at risk for developing hypernatremia
Inability to respond to sense of thirst — CNS Lesions (CVA or Tumor)
Physically unable to respond and get water – Obtunded, Intubated, Infant
Clinical manifestations of Hypernatremia
Change in mentation – slight confusion to an overt coma
§ Metabolic encephalopathy —
(pt should have an absence of a new focal or lateralizing neurologic sign)
• Treatment of Hypernatremia –
—- acute setting
time frame?
what is the body doing?
- what is the treatment?
acute setting (<24 hours)
body attempts to even out the tonicity of the environments of the intra and extra cellular spaces by pumping the cells full of electrolytes; but this is perturbing to the CNS
Treatment: Rehydrate the patient
• Treatment of Hypernatremia –
—- acute setting
time frame?
what is the body doing?
- what is the treatment?
> 24 hours
the body extrudes perturbing electrolytes and replaces them with Idiogenic Osmoles (Betaine, phosphorycholine, sorbitol, myoinositol)
Treatment: slow hydration so as not to induce cerebral edema
what are the idiogenic Osmoles
(Betaine, phosphorycholine, sorbitol, myoinositol)
how do you calculate the amount of water to rehydrate with in the setting of acute hypernatremia ?
Calculate the electrolyte free water deficit
.6 x Weight in Kg) x ((Plasma Na - 140)/140
