Block 4: Na+ and Fluids Flashcards
What is osmolality?
number of solute particles in 1 kg of solvent
What is the normal osmolality?
275-295 mOsm/kg
What is tonicity?
Osmotic pressure → determine fluid flow between 2 solution with depend on the relative concentration
What is oncotic pressure?
Exerted by the solute in the blood plasm → force that pulls water into vasculature
What is hydrostatic pressure?
Pressure generated by the water on the walls of the capillary → forcing water out the vasculature space
What are crystalloids?
Small molecules of the solute to expand the volume in the vasculature (electrolytes, NS, LR)
What are colloids?
Large molecules of the solute to expand the volume in the vasculature (proteins, RBC)
Big molecules can not cross the membrane into 3rd space, but water can
What components maintain oncotic pressure?
- RBC
- Albumin
- Electrolyte
Why do we use colloidal infusions?
increase the intravascular volume and not intracellular or interstitial volume
What are the types of colloidal solutions?
- Albumin
- Dextrans
- Etherified starch
- Gelatin
- Mannitol
- Blood transfusion
What happens if you administer hypertonic solution?
↑ ECF and ↓ ICF
What happens if you administer isotonic solution?
- ↑ ECF not affecting ICF
- Solution stay in intravascular space
What happens if you administer hypotonic solution?
- ↑ ECF and ICF
- Partial solution in intravascular and partial goes in cells
What is TBW?
60% body weight for men; 55% for women
What are the ICF solutes?
Potassium, magnesium ions, Proteins, organic phosphates
What is ECF solutes?
Sodium, chloride, bicard, plasma proteins
What is the homeostasis?
Intra- and extra-cellular osmolarity are equal
How do you calculate daily fluid requirements?
First 10 kg = 100 ml/kg, next 10 kg = 50 ml/kg, 20 ml/kg remainder
30-35mL/kg
Describe the what components play into compartment shifting?
- Solutes create osmotic gradients
- Water moves rapidly across cell membranes
What causes dehydration?
- Increased losses due to fever, sweating, diarrhea)
- Reduced intake
What causes volume excess?
- Reduced losses (CHF, cirrhosis, renal failure)
- Excess intake
What is the dehydration assessment?
- Decreased skin turgor
- BUN/sCr >20
- UOP <0.5 mL/kg/hr
- Dry mucous membranes
How do we treat dehydration?
- Replace lost fluid and electrolytes
- Oral replacement (pedialyte)
- Sever needs IV
What is edema?
↑ in interstitial fluid volume
What are the causes of edema?
- Increased capillary hydrostatic pressure
- Increased capillary permeability
- Decreased colloid osmotic pressure
- Obstruction in lymphatic system
- Excess body water and sodium
- Combo of mechanisms
How do you assess edema?
- Pulmonary edema
- Anasarca
- Wheezing/crackles
What is the treatment for edema?
- Diuretic (if currently on diuretics, ↑ the dose or add different MOA of diuretic)
- Sodium restriction (1-2 g/day)
- Treat underlying cause
How do loops work?
How is loop resistance built?
- Continuos infusion
- ↑ frequency
- Add thiazide - one hr prior to loop
What are the clinical uses of loops?
- Edema
- Acute renal failure (improve UO and limit kidney damage)
What are the ADRs of loops?
Hypoeletrolytes
Metabolic alkalosis
Hyperuricemia
Why are loops considered first line for loop diuretics?
Most potent
Ceiling dose
Rapid acting, short duration (except torsemide)
How do thiazide differ from loops?
Longer half-life vs loops, but weaker
Less frequent dosing
What are the clinical uses of thiazide?
Mild edema, kidney stones due to hypercalciuria
What are the ADR of thiazide?
- Hypokalemia
- Hypovolemia
- Hypercalcemia
- Hyponatremia
- Hypomagnesemia
- Hyperuricemia
What thiazide is IV and PO?
Chlorothiazide
What is the MOA of K sparing diuretics and how the drugs differ?
Inhibit ENaC channel in DCT and collecting duct
- Direct inhibition by triamtere and amiloride
- Aldosterone interference by spironolactone and eplerenone
How do K sparing differ from loops and thiazides?
Weaker with gradual fluid loss
Clinical uses of K sparing?
- HTN
- Adjust in CHF
- Combine with loops or thiazides to counteract K+ loss
ADR of K sparing?
- Metabolic acidosis
- Hyperkalemia
- Synecomastia with spiranolactone
Where does Acetazolimide work?
Proximal acting diuretic
Indication for Carbonic anhydrase inhibitor?
Acid/base disorders and glaucoma
What are the ADRs of CAIs?
Metabolic acidosis, hypokalemia
What is the treatment of cirrhosis using diuretics?
What is the treatment for nephrotic syndrome?
What is the diuretic components of CHF treatment?
What is Na+ regulated by?
- Renal mechanism
- NP
- RAAS
What is H2O regulated by?
- ADH/AVP
- Sodium concentration
- Effects osmolarity
What is the normal Na level?
136-145 mEq/L
How do calculate serum osmolality?
Osms = (2 x serum Na) + (serum glucose/18) + (BUN/2.8)
Where is AVP/ADH synthesized?
Synthesized in hypothalamus and secreted by posterior pituitary
What is the difference between dehydration and hypovolemia?
Dehydration: loss of total body water leads to increased serum osmolarity
Hypovolemia: symptomatic deficit in ECF volume not referred to osmolarity or tonicity
What is hyponatremia?
serum Na < 135 mEq/L
An excess of extracellular water due to impaired water secretion
1. AVP release
2. SIADH from cancer, injury
What causes AVP release?
CHF, nephrotic syndrome, cirrhosis
What are the risk factors of hyponatremia?
Disease related: CHF, cirrhosis, CKD
Polydipsia
Diet: Tea and toast diet
What are the drugs that induce hyponatremia?
Thiazides, hypotonic fluids, SSRIs, carbamazepine, lamotrigine, haloperidol
Are the signs and symptoms of hyponatremia?
Stupor/coma
Anorexia
Lethargy
Tendon Reflexes
Limp muscles
Orthostatic hypotension
Seizures/HA
Stomach cramping
What is the difference between acute and chronic hyponatremia?
Acute: onset within 48 hours; risk of cerebral edema
Chronic: onset >48 hours; risk of osmotic demyelination
What hypertonic hyponatremia? Treatment?
Osm >300 due to hyperglycemia, mannitol, glycine
Correct Sodium for hyperglycemia
How do you correct sodium?
Sodium decreases by 2.4 mEq/L for every 100 mg/dL increase in glucose >100
Corrected Na = measured Na + [2.4(glucose-100)/100]
What is isotonic hyponatremia?
Factitious/Pseudo-hyponatremia:
Hyperlipidemia: TG >1000
Hyperproteinemia
What is hypotonic hyponatremia?
Osm <280 (true hyponatremia)
Evaluate urine studies and volume status for diagnosis
What are the causes of SIADH?
- TUmor
- CNS disorders
- Pulmonary disroder
What are the drugs that causes SIADH?
- SSRI
- TCD
- MOAI
- Antiseizure
- Vasopressin (Desmopressin)
How is the algorithm for hyponatremia treatment?
How do you treat hypotonic hypervolemic hyponatremia?
1st line: Fluid and sodium restriction (1-1.5 L fluid per day, <2 g Na per day)
2nd: loop diuretics
3rd: Vaptans
Last: Demeclocycline
Severe sx: 3% NaCl
How do you treat hypotonic hypovolemic hyponatremia?
1st line: isotonic fluid administration
Need to replace sodium AND water
Preferred: Oral fluids/electrolytes
0.9% NaCl IV or LR IV
Severe sx: 3% NaCl
How do you treat hypotonic euvolemic hyponatremia?
1st: Address underlying cause (d/c drugs inducing)
2nd: Fluid restriction (1-1.5 L/day)
3rd line: Isotonic saline + loop
4th line: Vaptans
Last: Demeclocycline
Severe sx: 3% NaCl
How do you administer 3% saline?
Administer 150 mL over 20 min and repeat until Na+ increases by 5 mEq/L
What are vaptans used to treat?
Inhibits AVP (ADH)
Used in hypervolemic or euvolemic hyponatremia
Reserved for symptomatic or sever hyponatremia
What are the types of vaptans?
Conlvaptan
Tolvaptan
What is the difference between the vaptans?
Conivaptan: IV
Tolvaptan: PO, therapy should begin inpatient
What is the MOA of demeclocycline?
Tetracycline Antibiotic that inhibits tubular AVP activity → free water excretion
What is the onset and CI of demeclocycline? Indication?
3-6 days
Avoid in children, pregnant women, liver disease
Chronic SIADH as last resort
What is true hyponatremia?
Hypotonic
How do you treat hyponatremia based on tonicity?
What is the General Rules to Prevent Overcorrecting of Sodium?
Acute onset or severe symptoms require more aggressive therapy: 3% NS
Chronic should be corrected more slowly
What is the max Na+ that prevents overcorrection?
Acute: 12mEq/L/day
Chronic: 6-8 mEq/L/day
Results in cerebral edema, seizure, osmotic demyelination, death
How do you calculate total deficit of Na based the patient?
What do you evaluate in hyponatremia treatments?
- Water restriction (stable: ≥125)
- VRA (monitor serum Na Q4)
- Evaluate lung congestion, ascites, peripheral edema daily
- Signs/Symptoms of hyponatremia
- Follow up and assess 1 week of discharge
What are the signs and sx of hypernatremia?
What are the causes of hypernatremia?
- Diabetes Insipidus
- Excess losses: GI, renal, insensible
- Dehydration
- Diabetes Insipidus
- Burns
- Limited water access
How do you calculate ECF deficit?
ECF (water) deficit = TBW(current) x [1-140/Nas)
Compare the types of hypernatremia?
What is the goal of treating DI and hypernatremia?
Goal: Decrease UOP to <2 L/day
What the cause of central DI? Tx?
- decreased AVP secretion
- Familial
Desmopressin 10-20 mcg nasally QD or 10-20 mg PO QD
What are drugs that cause nephrogenic DI?
Lithium
What are the tx for nephrogenic DI?
- Correct underlying cause
- Hypotonic IV fluids
- Sodium restriction + HCTZ 25 mg PO QD-BID
What are the labs associated with DI?
up > 3 L/day
Usom < 250 mOsm/kg
How do you diagnose DI?
- Desmopressin test dose 4mcg SQ or IV
- Measure urine osmolality before and after dose
- UOsm will increase to ~600 mOsm/kg in central DI
How do you assess hypovolemia hypernatremia?
Uvol < 3 L/day, Uosm > 450 mOsm/kg
TX : 200-300 ml/hr NS -> intravascular volume restore -> _ NS or D5W
How do you assess euvolemia hypernatremia?
Uvol > 3 L/day, Usom < 250 mOsm/kg
→ Diabetes Insipidus (DI)
How do you assess DI central hypernatremia?
Central DI - CNS insult and no offensive drug
Response to desmopressin
TX: Desmopressin
How do you assess DI nephrogenic hypernatremia?
Not responsive to desmopressin and offensive drugs (lithium)
TX: HCTZ, water replacement + Na restriction
How do you assess hypervolemia hypernatremia?
Furosemide 20-40 mg IV Q6h if not currently on furosemide
What is the infusion rate to correct hypernatremia?
What components are you looking at for stable Na levels?
