GU Block 1 Cram Flashcards
Define Osmolality
Define Osmolarity
Concentration of particles/kg
Concentration of particles/L
Define Tonicity
This is related to its ?
ECF ability to move water in/out of cell via osmosis;
Osmolytes impermeable to cell membrane
Osmolarity
Define Hypotonic
Define Isotonic
Define Hypertonic
ECF has lower osmolarity than ICF, water moves into cell
ECF=ICF
ECF has higher osmolarity than ICF, water moves out of cell
What does a low FEx mean?
What does a high FEx mean?
Why is the FEx a useful tool?
Low: high renal absorption
<1%= prerenal dz- low output HF
High: low avidity, renal wasting
>2%= postrenal dz- tubular necrosis, kidney damage
Indicates if kidney’s response is appropriate to the E+ d/o
Define Ineffective Osmoles
To maintain steady state, how much mosmols/urine needs to be excreted per day?
Substances easily permeate membranes, no tonicity contribution or shifts between compartments
60 mosmols/day
Max urine osmolality= 1200
Min of 500mL/day
What stimulates the sensation of thirst
What stimulates osmoreceptors
Inc osmolality
Dec of ECF volume
Inc tonicity
Average threshold for sensation of thirst to arise is ?
What is the major stimulus for AHD release?
Osmolality is primarily determined by ?
295 mosmol/kg
Hypertonicity
Na concentration
What is the MC cause of hyponatremia in hospitalized PTs
Hyponatremia reflects excess ? to ? ratio
Hypotonic fluid administration
Excess water to Na ratio
Hyponatremia criteria starts at ? and is divided into severity at ? amounts
Isotonic hyponatremia is AKA and can be seen?
<135
Mild: 130-134
Sev: <125
Pseudohyponatremia:
Hyperlipidemia
Hyperprotieniemia
How do PTs get hypovolemic hypotonic hyponatremia
What differentiates if this is caused by renal or extra renal causes?
Volume loss replaced w/ hypotonic fluids
ADH released, retains free water
Dec osmolality to inc vascular volume
Urine Na >20= renal
Urine Na <10= extra renal
What causes Euvolemic Hypotonic Hyponatremia- SIADH
What can cause this?
ADH released d/t hyperosmolarity/dec arterial volume
Inappropriate water retention= concntrated urine >300
CNS Pulm d/o Malignancy
When is Low Solute Diet induced Euvolemic Hypotonic Hyponatremia seen?
When can Exercise Associated Hyponatremia be seen?
Pregnancy
Forced hydration in basic
What are the 4 criteria needed for SIADH Dx
What two findings my also be present
Hypotonic Hyponatremia
No HLK Dz
Normal thyroid/adrenal
Urine Na >20
Dec BUN
Hypouricemia
How is chronic hypotonic hyponatremia Tx
What is the adverse outcome of rapid Txs
4-6mEq/L/24hrs, max 6-8/24hrs
Osmotic demyelination syndrome: flaccid paralysis dysarthria dysphagia
Central Pontine Myelitis
How is hypovolemic hyponatremia Tx
How is hypotonic hypervolemic hyponatremia Tx
Isotonic fluids- corrects fluid loss, suppresses ADH
Loop diuretics
A/CKDz= dialysis
How is hypotonic euvolemic hyponatremia secondary to SIADH Tx
What is added to Tx if case is refractory?
What is used if Na <125 or mild hyponatremia w/ Sx and resistant to fluid restriction?
Fluid/offender restriction
Tx pain/nausea
Loop diuretic- Furosemide
Inc solute intake
Vasopressin 2, not w/ fluid restriction
How are PTs w/ Sx/Sev hyponatremia Tx
Since this Tx is done slowly, what is the goal of Tx?
Admit, d/c offender
100mL 3%NS over 10min
Max correction: 4-6mEq/24hr
Sx relief
When Tx hyponatremia, what finding indicates ADH secretion has stopped?
What is added to hyponatremia Tx if PT has CHF?
High urine output/hr
Vasopressin 2
How is hyponatremia Tx when seizure/coma is present
100ML 3%NS over 10-15min
Measure serum Na after each infusion, max of 3
Stop when 5mEq inc reached
KLO w/ 0.9%NS, max 8mEq in first 24hrs
Causes of HypoNa, normal osmolality
Causes of HypoNa, high osmolality
Hyperprotein
Hyperlipid
Hyperglycemia
Mannitol
Contrast agents
Causes of HypoNa, HypoVol
<10= external: GI Skin, 3rd space
> 20= renal: diuretic nephropathy mineralcorticoid deficient CSWS
Causes of HypoNa, HyperVol
Causes of HypoNa, Euvol
Cirrhosis HF AKDz NephSynd
<100: psych, low solute diet
>100: SIADH Hypothyroid glucocorticoid deficient
Variable: osmostat reset
What are the two main defenses against hypernatremia?
How to differentiate non/renal causes
Thirst, Water intake
Urine osmolality
All PTs w/ hypernatremia will have ?
These PTs are usually hypovolemic due to ? loss such a ?
Hyperosmolality
Hypotonic loss:
Renal- DI
Nonrenal: GI, Burns