Nephro-Fluids and Electro Flashcards
What are the two main things that maintain plasma osmolality?
thirst and ADH
Hyponatremia
serum sodium <136
What are the first tests to order or things to consider when evaluating hyponatremia?
plasma and urine osmolality, urine sodium, and assessment of volume status
What is ADH doing in hyponatremia?
ADH independent (normal): tea and toast, beer pottomania, psychogenic polydipsia, renal failure
ADH Dependent: hypovolemic, hypervolemic, euvolemic
What causes pseudohyponatremia?
high lipids or high proteins
When you have hyponatremia, what do you measure first? How does this send you through the algorithm?
You measure urine osmolality first. A Uosm >100 suggests ADH is playing a role (so consider, hypo/euv/hypervolemic)
If urine osm is <100 then it is the teatoast/beerpoto/psychogenic polydipsia that you have to think about
Causes of hypovolemic hyponatremia with Una <20 and Una >20. What happens to ADH?
pg 11
- ADH is stimulated, or elevated
Una <20: vomiting, diarrhea, burns
Una >20: diuretic therapy, renal salt wasting, adrenal insufficiency, cerebral salt wasting
Causes of euvolemic hyponatremia with Una <20 and Una >20
pg11
Una >40: exclude hypothyroidism, glucocorticoid deficiency, SIADH, define cause o fit
Causes of hypervolemic hyponatermia with Una <20 and Una >20
pg11
*Basically despite high total body water and total body sodium, they are elevated at the same time and kidney senses decreased arterial volume of sodium so ADH given
Una < 20: CHF, cirrhosis, nephrosis
Una >20: acute and chronic kidney failure
What is the most common causes of euvolemic hyponatremia?
SIADH
How fast should you correct hyponatremia? Why?
Brain cells adapt to chronic hypontonicity and so if you correct too fast then you can cause neuronal damage leading to osmotic demyelination
don’t correct more than 8 points in 24 hours
How should acute SYMPTOMATIC hyponatremia be treated?
hypertonic saline with no more than 8 point correction in 24 hours… remember this is only if it is symptomatic!!
Loops diuretics may also help increase free water excretion
How is CHRONIC hyponatremia treated?
Usually hypervolemic hyponatremia and usually involves correcting the underlying disorder (renal failure-dialysis, CHF, cirrhosis), sodium and free water restriction, and diuretic therapy
What is first line therapy for EUVOLEMIC hyponatremia (SIADH)
(1) treatment of underlying cause and free water restriction
(2) loop diuretics, oral salt supplementation, followed by oral demeclocycline
(3) vasopressin antagonists (tolvaptin, conivaptan)
What is hypernatremia
Serum sodium >146
Why do elderly ppl often get hypernatremia?
Decreased thirst and or diminished access to fluids
What are the causes of hypernatremia besides decreased thirst?
Insensible water losses: heat, fever, exercise, severe burns, mechanical ventilation, osmotic diarrhea, secretory diarrheas
Renal water loss: osmotic diuresis due to hyperglycemia, post obstructive diuresis, or drugs (contrast, mannitol), central or nephrogenic DI
What should you ask when evaluating hypernatremia?
thirst, polyuria, diarrhea? document fluid intake and output (strict Is and Os)
How should people with nephrogenic DI be treated?
if desmopressin sensitive–calculate free water deficit and correct over 24-48 hours
you can use 1/2 normal saline
How do you treat hypernatremia?
It’s either caused by sodium gain or water loss
For euvolemic and hypervolemic hypernatremia you use a loop diuretic and 5% dextrose
For hypovolemic hypernatremia, you correct the free water loss
What is hypokalemia?
Serum potassium <3.5
What can occur when potassium goes <2.5?
Rhabdo can occur and ascending paralysis with respiratory failure
What are the top four reasons for hypokalemia?
pg 15
Pseudohypokalemia
Intracellular shift
Inadequate K intake (rare)
Excessive K loss
What are the steps to working up hypokalemia?
pg 15
- serum K if low, then…
- spot urine K
- ->If urine K is <20 (low) then this is because of GI loss
- —> if urine K is >20, then you need to work up the reason for renal loss of sodium - Check blood pressure
- THis, then takes you through the potassium algorithm, based on whether you have high or low blood pressure
low serum sodium, urine sodium >20, HIGH BP
pg 15
Check renin.
Low renin–> check aldosterone
High renin–> RAS, renin secreting tumor, malignant hypertension, scleroderma renal crisis
Low renin, low aldosterone-> apparent mineralocorticoid excess, Liddle syndrome, 11-B-HSD deficiency, congenital adrenal hyperplasia, Cushing syndrome, licorice
Low renin, high aldosterone-> primary hyperaldosteronism, glucocorticoid remediable hyperaldosteronism
low serum sodium, urine sodium >20, LOW/NORMAL BP
pg 15
Check acid-base.
Metabolic acidosis–> RTA, toluene, diabetic ketoacidosis
Metabolic alkalosis–> check urine Cl
Low urine Cl (<20): vomiting, nonreabsorbable anion, NG suction
High urine Cl (>20): Diuretics, Bartter syndrome, Gitelman syndrome, amino glycoside toxicity, MG deficiency
Medications that cause a transient shift of potassium from the extracellular compartment into cells
Epinephrine Decongestants Bronchodilators Theophylline Caffeine Insulin Respiratory/metabolic alkalosis
What is hypokalemic periodic paralysis?
It is a rare familial or acquired disorder characterized by flaccid generalized weakness from a sudden intracellular potassium shift caused by strenuous exercise or a high carb meal
What does urine potassium loss >20 suggest?
suggests excessive urinary losses
What does urine potassium <20 suggest?
It suggests cellular shift, decreased intake, or extra renal losses
What are causes of pseudohypokalemia?
Lab drawing error
What is hyperkalemia
Serum potassium >5
What is the first thing you need to do when working up hyperkalemia?
You get an EKG
What are the EKG changes of hyperkalemia?
Peaked T waves, as hyperkalemia progresses, there is prolongation of the PR interval, loss of P waves, and eventual widening of the QRS with a sine wave pattern that can precede asystole
What are the causes of hyperkalemia?
Pseudohyperkalemia–AML
Extracellular shift
Increased K intake
Decreased K excretion (most common)
Drugs that cause hyperkalemia?
digoxin toxicity, succinylcholine, beta blockers somatostatin
Common causes of hyperkalemia from extracellular shift?
metabolic acidosis insulin deficiciency rhabdomyolysis tumor lysis hemolysis hyperosmolarity hyperkalemic periodic paralysis
Causes of pseudohyperkalemia
Blood malignancies
having a tourniquet on for too long
venipuncture issues
What are the three causes of hyperkalemia due to decreased potassium excretion?
- Impaired aldosterone action
- Decreased urine flow or sodium delivery to distal nephron (volume depletion, heart failure)
- Kidney failure (AKI, CKD, ESRD)
How does aldosterone resistance cause hyperkalemia?
Medications: amiloride, triamterene, spironolactone, eplerenone, pentamidine, trimethoprim
Tubulointerstitial disease
Gordon syndrome
Defective mineralocorticoid receptor
How does aldosterone deficiency cause hyperkalemia?
medications: NSAIDS, COX-2 inhibitors, calcineurin inhibitors, ACEI/ARBS
Diabetes mellitus
HIV
Urinary tract obstruction
Aging
Heparin
Ketoconazole
Adrenal insufficiency
Congenital enzyme defects
How do you manage severe hyperkalemia with EKG changes?
This requires immediate stabilization of the myocardial cell membrane, rapid shifting of potassium intracellularly, and total body potassium elimination.
- -Give IV calcium for membrane stabilization (give multiple times if needed)
- Insulin or high dose beta adrenergic agonists (albuterol)
- sodium bicarb can be given in the setting of a metabolic acidosis UNLESS it is DKA
What is the time of onset for these hyperkalemia drugs:
- IV calcium
- 10 units of insulin
- beta agonists
- IV calcium: 30-60 minutes
- 10 units of insulin: 10-20 minutes (duration is 4-6h)
- beta agonists: 3-5 minutes and lasts 1-4 hours
How is potassium removed from the body?
Loop diuretics+saline infusion
sodium polystyrene sulfonate
hemodialysis
Longterm treatment of hyperK, like with ESRD? What about with Endo disorders?
low K diet, correct underlying cause, diuretics.
If there is an endocrine cause, like hypoaldosteronism… then you need fludrocortisone too?
How does hypophosphatemia occur? What patients have this?
<3
alcoholics, malnutrition, critical illness
What is fanconi syndrome?
it is a hypophosphatemia with a type 2 (proximal) RTA with urine los of bicarb, phosphaturia, glucosuria, aminoaciduria
Management of hypophos?
IV phos, monitor phos and calcium every 6h
What is the most common causes of hyperphos? How is it managed chronically?
CKD and AKI.
Managed by dietary phosphate restriction and phosphate binders
