Electrolytes/Acid-Base Flashcards
How does acid base affect iCa level?
Acidic pH facilitate dissociation of calcium from protein and increases the amount of iCa in the sample.
Alkaline pH favors calcium binding to protein, thus decreasing the amount of iCa
Which ion is the main intracellular anion?
Phosphate
Where is the central osmocenter?
Hypothalamus
What are the two stimuli for ADH release?
1) Increased plasma osmolarity
2) Decreased effective circulating volume (signals sent by baroreceptors)
- maintenance of effective circulating volume is always prioritized over maintenance of normal plasma osmolality
What is ADH also called?
Arginine vasopressin
Explain how ADH increased renal distal tubules and collection duct water resorption.
ADH binds to V2 receptors, which are coupled with stimulatory G proteins (Gs) → activates adenylate cyclase (AC) → stimulates formation of cyclic adenosine monophosphate (cAMP) from ATP → activates protein kinase A and phosphorylation of intracellular proteins → moving aquaporin-2 (AQP-2) to the luminal side of the cell membrane.
On the basolateral side of the cell membrane are other aquaporins, AQP-3 and AQP-4, that permit water to flow out of the cell, although these aquaporins do not appear to be regulated by AVP.
Where do most and second most Na absorption happen in the nephron? What channels do they use?
1) Proximal renal tubule (about 67%)
- Co-transport with glucose, AA, phosphate, Na-H antitransporter
2) Ascending loop of Henles (about 25%)
- Na-K-2Cl cotransporter, Na-H antitransporter
3) Distal convoluted tubule (about 5%)
- Na-Cl cotransporter
4) Collecting duct (about 3%)
- Na channel
What stimulate aldosterone and what inhibit it?
Stimulation: Angiotensin II, Hyperkalemia, ACTH
Inhibition: Dopamine, ANP
True or False: catecholamine can stimulate proximal renal tubule Na reabsorption through 𝜶1 receptor.
True
True or False: catecholamine can stimulate renin release through 𝜶1 receptor.
False
𝜷1
True or False: Angiotensin II can stimulate Na-H antiporter in the proximal tubules and facilitate Na reabsorption.
True
List 5 drugs that can stimulate ADH release.
1) Barbiturates
2) Angiotensin II
3) Beta adrenergic drugs
4) Narcotics
5) Vincristine
6) Tricyclic antidepressant
7) Cholinergic drugs
8) Carbamazepine
What are the three big categories of causes for hypernatremia. List 3 examples for each categories.
1) Pure water deficit
- Diabetes insipidus (central/nephrogenic)
- Primary hypodipsia
- No access to water
- High environmental temperature
2) Hypotonic fluid loss
- Extra-renal: GI loss (V/D), third-space loss, burn
- Renal: AKI, CKD, post-obstructive diuresis, diuretic administration
3) Impermanent solute gain
- Salt toxicity
- Hyperaldosteronism
- Hypertonic saline infusion
What is the cause of central diabetes insipidus?
Partial or lack of production of ADH (congenital, trauma, neoplasia, idiopathic)
For dogs with central DI, administration of DDAVP can improve the USG and/or osmolarity, but the initial effect may not be very significant. Why?
Because of renal medullary wash out → no concentration gradient for water to move
What is the MOA of glucocorticoid, E. coli endotoxemia, hypokalemia, hypercalcemia causing NDI?
Inhibit adenyl cyclase on the basal membrane → inhibit aquaporin 2 movement to the luminal membrane → decrease water reabsorption
- Other causes of NDI: hepatic insufficiency, hyperthyroidism, medullary interstitial amyloidosis (e.g. cats, Sharpei), pyelonephritis, polycystic kidney disease
How does thiazide help with DI management?
Thiazide cause mild volume depletion → increase water and Na reabsorption at the proximal renal tubule and decrease the flow to the distal collecting tubule where water is impermeable → decrease urine volume
How does paintballs cause hypernatremia?
They usually contain polyethylene glycol, glycerol and sorbitol, which can cause severe osmotic diarrhea
When we correct the chronic hypernatremia or hyponatremia, what is the rate that we shouldn’t exceed?
not exceed 10-12 mEq/L per 24 hours
What can cause hyponatremia with high osmolarity?
Hyperglycemia, mannitol infusion
What can cause hyponatremia with normal osmolarity (pseudohyponatremia)?
Hyperlipidemia
Severe hyperproteinemia
How to calculate osmol gap?
Osmol gap = Measured osmolarity - Calculated osmolarity
What is normal osmol gap in dogs and cats?
< 10 mOsm/L
What are the common cause of increased osmol gap?
Ethylene glycol intoxication, ethanol intoxication