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Therapeutics I > Block 4: Na+ and Fluids > Flashcards

Block 4: Na+ and Fluids Flashcards

1
Q

What is osmolality?

A

number of solute particles in 1 kg of solvent

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2
Q

What is the normal osmolality?

A

275-295 mOsm/kg

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3
Q

What is tonicity?

A

Osmotic pressure → determine fluid flow between 2 solution with depend on the relative concentration

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4
Q

What is oncotic pressure?

A

Exerted by the solute in the blood plasm → force that pulls water into vasculature

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5
Q

What is hydrostatic pressure?

A

Pressure generated by the water on the walls of the capillary → forcing water out the vasculature space

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6
Q

What are crystalloids?

A

Small molecules of the solute to expand the volume in the vasculature (electrolytes, NS, LR)

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7
Q

What are colloids?

A

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

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8
Q

What components maintain oncotic pressure?

A
  1. RBC
  2. Albumin
  3. Electrolyte
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9
Q

Why do we use colloidal infusions?

A

increase the intravascular volume and not intracellular or interstitial volume

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10
Q

What are the types of colloidal solutions?

A
  1. Albumin
  2. Dextrans
  3. Etherified starch
  4. Gelatin
  5. Mannitol
  6. Blood transfusion
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11
Q

What happens if you administer hypertonic solution?

A

↑ ECF and ↓ ICF

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12
Q

What happens if you administer isotonic solution?

A
  1. ↑ ECF not affecting ICF
  2. Solution stay in intravascular space
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13
Q

What happens if you administer hypotonic solution?

A
  1. ↑ ECF and ICF
  2. Partial solution in intravascular and partial goes in cells
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14
Q

What is TBW?

A

60% body weight for men; 55% for women

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15
Q

What are the ICF solutes?

A

Potassium, magnesium ions, Proteins, organic phosphates

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16
Q

What is ECF solutes?

A

Sodium, chloride, bicard, plasma proteins

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17
Q

What is the homeostasis?

A

Intra- and extra-cellular osmolarity are equal

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18
Q

How do you calculate daily fluid requirements?

A

First 10 kg = 100 ml/kg, next 10 kg = 50 ml/kg, 20 ml/kg remainder

30-35mL/kg

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19
Q

Describe the what components play into compartment shifting?

A
  1. Solutes create osmotic gradients
  2. Water moves rapidly across cell membranes
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20
Q

What causes dehydration?

A
  1. Increased losses due to fever, sweating, diarrhea)
  2. Reduced intake
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21
Q

What causes volume excess?

A
  1. Reduced losses (CHF, cirrhosis, renal failure)
  2. Excess intake
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22
Q

What is the dehydration assessment?

A
  1. Decreased skin turgor
  2. BUN/sCr >20
  3. UOP <0.5 mL/kg/hr
  4. Dry mucous membranes
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23
Q

How do we treat dehydration?

A
  1. Replace lost fluid and electrolytes
  2. Oral replacement (pedialyte)
  3. Sever needs IV
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24
Q

What is edema?

A

↑ in interstitial fluid volume

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25
What are the causes of edema?
1. Increased capillary hydrostatic pressure 2. Increased capillary permeability 3. Decreased colloid osmotic pressure 4. Obstruction in lymphatic system 5. Excess body water and sodium 6. Combo of mechanisms
26
How do you assess edema?
1. Pulmonary edema 2. Anasarca 3. Wheezing/crackles
27
What is the treatment for edema?
1. Diuretic (if currently on diuretics, ↑ the dose or add different MOA of diuretic) 2. Sodium restriction (1-2 g/day) 3. Treat underlying cause
28
How do loops work?
29
How is loop resistance built?
1. Continuos infusion 2. ↑ frequency 3. Add thiazide - one hr prior to loop
30
What are the clinical uses of loops?
1. Edema 2. Acute renal failure (improve UO and limit kidney damage)
31
What are the ADRs of loops?
Hypoeletrolytes Metabolic alkalosis Hyperuricemia
32
Why are loops considered first line for loop diuretics?
Most potent Ceiling dose Rapid acting, short duration (except torsemide)
33
How do thiazide differ from loops?
Longer half-life vs loops, but weaker Less frequent dosing
34
What are the clinical uses of thiazide?
Mild edema, kidney stones due to hypercalciuria
35
What are the ADR of thiazide?
1. Hypokalemia 2. Hypovolemia 3. Hypercalcemia 4. Hyponatremia 5. Hypomagnesemia 6. Hyperuricemia
36
What thiazide is IV and PO?
Chlorothiazide
37
What is the MOA of K sparing diuretics and how the drugs differ?
Inhibit ENaC channel in DCT and collecting duct 1. Direct inhibition by triamtere and amiloride 2. Aldosterone interference by spironolactone and eplerenone
38
How do K sparing differ from loops and thiazides?
Weaker with gradual fluid loss
39
Clinical uses of K sparing?
1. HTN 2. Adjust in CHF 3. Combine with loops or thiazides to counteract K+ loss
40
ADR of K sparing?
1. Metabolic acidosis 2. Hyperkalemia 3. Synecomastia with spiranolactone
41
Where does Acetazolimide work?
Proximal acting diuretic
42
Indication for Carbonic anhydrase inhibitor?
Acid/base disorders and glaucoma
43
What are the ADRs of CAIs?
Metabolic acidosis, hypokalemia
44
What is the treatment of cirrhosis using diuretics?
45
What is the treatment for nephrotic syndrome?
46
What is the diuretic components of CHF treatment?
47
What is Na+ regulated by?
1. Renal mechanism 2. NP 3. RAAS
48
What is H2O regulated by?
1. ADH/AVP 2. Sodium concentration 3. Effects osmolarity
49
What is the normal Na level?
136-145 mEq/L
50
How do calculate serum osmolality?
Osms = (2 x serum Na) + (serum glucose/18) + (BUN/2.8)
51
Where is AVP/ADH synthesized?
Synthesized in hypothalamus and secreted by posterior pituitary
52
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
53
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
54
What causes AVP release?
CHF, nephrotic syndrome, cirrhosis
55
What are the risk factors of hyponatremia?
Disease related: CHF, cirrhosis, CKD Polydipsia Diet: Tea and toast diet
56
What are the drugs that induce hyponatremia?
Thiazides, hypotonic fluids, SSRIs, carbamazepine, lamotrigine, haloperidol
57
Are the signs and symptoms of hyponatremia?
Stupor/coma Anorexia Lethargy Tendon Reflexes Limp muscles Orthostatic hypotension Seizures/HA Stomach cramping
58
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
59
What hypertonic hyponatremia? Treatment?
Osm >300 due to hyperglycemia, mannitol, glycine Correct Sodium for hyperglycemia
60
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]
61
What is isotonic hyponatremia?
Factitious/Pseudo-hyponatremia: Hyperlipidemia: TG >1000 Hyperproteinemia
62
What is hypotonic hyponatremia?
Osm <280 (true hyponatremia) Evaluate urine studies and volume status for diagnosis
63
What are the causes of SIADH?
1. TUmor 2. CNS disorders 3. Pulmonary disroder
64
What are the drugs that causes SIADH?
1. SSRI 2. TCD 3. MOAI 4. Antiseizure 5. Vasopressin (Desmopressin)
65
How is the algorithm for hyponatremia treatment?
66
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
67
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
68
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
69
How do you administer 3% saline?
Administer 150 mL over 20 min and repeat until Na+ increases by 5 mEq/L
70
What are vaptans used to treat?
Inhibits AVP (ADH) Used in hypervolemic or euvolemic hyponatremia Reserved for symptomatic or sever hyponatremia
71
What are the types of vaptans?
Conlvaptan Tolvaptan
72
What is the difference between the vaptans?
Conivaptan: IV Tolvaptan: PO, therapy should begin inpatient
73
What is the MOA of demeclocycline?
Tetracycline Antibiotic that inhibits tubular AVP activity → free water excretion
74
What is the onset and CI of demeclocycline? Indication?
3-6 days Avoid in children, pregnant women, liver disease Chronic SIADH as last resort
75
What is true hyponatremia?
Hypotonic
76
How do you treat hyponatremia based on tonicity?
77
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
78
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
79
How do you calculate total deficit of Na based the patient?
80
What do you evaluate in hyponatremia treatments?
1. Water restriction (stable: ≥125) 2. VRA (monitor serum Na Q4) 3. Evaluate lung congestion, ascites, peripheral edema daily 4. Signs/Symptoms of hyponatremia 5. Follow up and assess 1 week of discharge
81
What are the signs and sx of hypernatremia?
82
What are the causes of hypernatremia?
1. Diabetes Insipidus 2. Excess losses: GI, renal, insensible 3. Dehydration 4. Diabetes Insipidus 5. Burns 6. Limited water access
83
How do you calculate ECF deficit?
ECF (water) deficit = TBW(current) x [1-140/Nas)
84
Compare the types of hypernatremia?
85
What is the goal of treating DI and hypernatremia?
Goal: Decrease UOP to <2 L/day
86
What the cause of central DI? Tx?
1. decreased AVP secretion 2. Familial Desmopressin 10-20 mcg nasally QD or 10-20 mg PO QD
87
What are drugs that cause nephrogenic DI?
Lithium
88
What are the tx for nephrogenic DI?
1. Correct underlying cause 2. Hypotonic IV fluids 3. Sodium restriction + HCTZ 25 mg PO QD-BID
89
What are the labs associated with DI?
up > 3 L/day Usom < 250 mOsm/kg
90
How do you diagnose DI?
1. Desmopressin test dose 4mcg SQ or IV 2. Measure urine osmolality before and after dose 3. UOsm will increase to ~600 mOsm/kg in central DI
91
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
92
How do you assess euvolemia hypernatremia?
Uvol > 3 L/day, Usom < 250 mOsm/kg → Diabetes Insipidus (DI)
93
How do you assess DI central hypernatremia?
Central DI - CNS insult and no offensive drug Response to desmopressin TX: Desmopressin
94
How do you assess DI nephrogenic hypernatremia?
Not responsive to desmopressin and offensive drugs (lithium) TX: HCTZ, water replacement + Na restriction
95
How do you assess hypervolemia hypernatremia?
Furosemide 20-40 mg IV Q6h if not currently on furosemide
96
What is the infusion rate to correct hypernatremia?
97
What components are you looking at for stable Na levels?
98

Therapeutics I (32 decks)

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