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850 > Water and Sodium Disorders > Flashcards

Water and Sodium Disorders Flashcards

1
Q

Usual IV Fluid Needs

A
  • 1-10 kg: 100 mL/kg
  • 11-20 kg: 1000 mL + 50 mL/kg for each kg >10
  • > 20 kg: 1500 mL + 20 mL/kg for each kg > 20
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2
Q

Factors Effecting Fluid Requirements

A
  • Age (more for young, less for old)
  • Environment (humidity/temperature)
  • Increased fluid need conditions (burns, diarrhea, dehydration, fever)
  • Decreased fluid need conditions (CHF, renal failure, fluid overload, mechanical ventilation)
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3
Q

Monitoring Fluid Therapy

A
  • Measure intake and output
  • Intake from food/IVs
  • Output from urine, stool, GI
  • Daily weights are useful for fluid balance
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4
Q

Fluid Therapy Assessment

A
  • In&raquo_space; Outs assessed as positive fluid balance
  • Out > In assessed as negative fluid balance
  • Usually Ins are a little greater than outs due to insensible fluid loss
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5
Q

Fluid Imbalance Goals

A
  • Correction of volume depletion: input&raquo_space; output

- Fluid Overloaded CHF: Output > Input

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6
Q

ECF

A
  • Extracellular Fluid
  • Important to adequately perfuse tissues and organs
  • Volume depletion occurs with decreased ECF
  • Regulated by kidneys, ADH, Renin, prostaglandins
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7
Q

Signs of Mild Volume Depletion (<10%)

A
  • Thirst
  • Decreased urine output
  • Increased hematocrit
  • Increased urine sp. gravity
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8
Q

Signs of Modest Volume Depletion (20%)

A
  • Dry mucous membranes
  • Tachycardia
  • Orthostatic Hypotension
  • Increase BUN/Cr
  • CNS (apathy, drowsy)
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9
Q

Signs of Severe Volume Depletion (30%)

A
  • Hypotension
  • Weak Pulse
  • CNS (stupor, coma)
  • Skin cool, pale, poor turgor
  • Pronounced oliguria
  • Leads into shock
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10
Q

“Effective Osmole”

A
  • Can’t move freely across cell membranes
  • Sodium is the main one
  • Osmolality is maintained between 275-290 mOsm/kg
  • Maintenance results from vasopressin (ADH), thirst, and renal fxn
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11
Q

Calculated Osmolality

A

2 * (Na+) + BUN/2.8 + Glucose/18

About 10 mOsm/kg less than actual since certain solutes are ignored

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12
Q

Distribution of IV Fluids

A
  • D5W: 40% ECF/60% ICF
  • 0.9% NaCl and Lactated Ringers: 100% ECF
  • 0.45% NaCl: 70% ECF/30% ICF
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13
Q

Distribution of D5W

A
  • Iso-osmolar: 278 mOsm/L

- Dextrose taken into cell via insulin and free water is left behind and distributed to all body compartments

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14
Q

Isotonic Crystalloid Solutions

A
  • NS, Lactate Ringers
  • Only distribute into ECF
  • LRs may be preferred for fluid rescusitation (less hyperchloremia and renal dysfxn)
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15
Q

Sodium/Water Regulation

A
  • Sodium is actively removed from ICF to ECF and is a main osmolality determinant in ECF
  • Filtered by glomerulus and 50-90% reabsorbed in proximal tubule
  • Aldosterone increase sodium reabsorption (less fluid excretion)
  • Antidiuretic Hormone increases free water reabsorption
  • [Na+] = 135-145 mEq/L, serum concentration may NOT reflect total body Na+
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16
Q

Classifications of Na/Water Disorders

A

Hyponatremia

  • Hypertonic
  • Isotonic
  • Hypotonic (hyper/iso/hypovolemic)

Hypernatremia

  • Hypervolemic
  • Euvolemic
  • Hypovolemic
17
Q

Hypertonic Hyponatremia

A
  • Na < 135
  • > 295 mOsm/kg
  • Excess non-sodium osmoles in ECF (glucose, mannitol)
  • Increased ECF dilutes ECF and makes serum sodium concentration low (total body is normal)
  • Sodium drops by 1.7 for each 100 mg/dL increase in glucose
18
Q

Hyponatremia Treatment

A
  • Determine symptoms related to hyponatremia and if they are related to tonicity or volume
  • Address accordingly based on tonicity or volume
  • If tonicity: raise [Na+] to normal but avoid increasing too quickly (osmotic demylination syndrome)
  • Treat/remove underlying cause
19
Q

Hypovolemic Hypotonic Hyponatremia

A
  • Na+ deficit > water deficit
  • Signs/symptoms generally associated with ECF depletion
  • Causes: GI/renal/extra-renal losses, latrogenic (replace sodium-rich fluid losses with sodium free fluids
  • Intact thirst mechanism and replacing fluids with hypotonic fluids
  • Determine if renal or extrarenal if sodium concentration is high (>20) or low (<20) respectively
20
Q

Hypo/Hypo/Hypo Treatment

A
  • Restore vital organ perfusion
  • Decrease fluid losses: hold diuretics and administer antiemetics
  • Replace sodium/volume loss with crystalloid (20 mL/kg and infuse rapidly)
  • Monitor for symptom resolutions and [sodium]
21
Q

Hypervolemic Hypotonic Hyponatremia

A
  • Excess total body Na+ and ECF, ECF > Na+
  • Causes: CHF, cirrhosis, less “effective” circulating plasma volume
  • Presentation: acute weight gain, pulmonary congestion, edema,
  • *Usually no severe symptoms from hypo-osmolality**
22
Q

Hyper/Hypo/Hypo Treatment

A
  • Restrict salt and water
  • Fluid restrict to 1-1.2 L/day
  • Sodium restriction to 1-2g/day
  • May use loop diuretics to remove water
23
Q

Euvolemic Hypotonic Hyponatremia

A
  • Excess total body water, minimal change in ECF and normal total body Na
  • Hypotonicity symptoms: cerebral cellular swelling, vomiting, confusion, agitation
  • If Na < 120: seizures, coma, death
  • Symptom severity related to decrease and rate of hyponatremia
  • Causes: SiADH or excessive free water intake
24
Q

SiADH

A
  • Syndrome of Inappropriate ADH
  • Release ADH or ADH-life substance to reabsorb inappropriate free water
  • Appear euvolemic, minimal free water excretion => decreased, concentrated urine
  • Exclude hypocortisolism, renal failure, and hypothyroidism to diagnose
25
Q

Non-Drug SiADH

A
  • CNS/lung tumors
  • Head trauma/cerebral thrombosis or bleed
  • Infectious disease: meningitis, pneumonias, tuberculosis
26
Q

Drug Induced SiADH

A
  • NSAIDs, carbamazepine, vincristine
  • Opioids, phenobarbital, thiazide diuretics
  • TCAs, ecstasy
27
Q

SiADH Labs

A
  • Serum Na < 130
  • Serum Osmolality < 275
  • Urine Osmolality > 100
  • Urine Sodium > 20
28
Q

Managing Acute Symptomatic Euvolemic Hyponatremia

A
  • Reverse CNS symptoms associated with hypo-osmolar state
  • Don’t need to raise sodium to normal, should raise more than 6-12 mEq in 24 hours
  • Monitor serum sodium frequently (Q2-4H)
  • Hypertonic Saline (3* NaCl) to treat severe symptoms
29
Q

Chronic Treatment of SiADH

A
  • Treat underlying cause if possible
  • Fluid restrict (<1 L per day)
  • Sodium chloride and loop diuretics
  • Demeclocycline (600-1200 mg over 3-4 doses per day) or Vaptans to block action of ADH
30
Q

Vaptans

A
  • Vasopressin antagonists (mainly V2 receptors in renal collecting duct)
  • Conivaptan is IV and for short term use in isovolemic hyponatremia
  • Tolvaptan - oral and approved for isovolemic and hypervolemic hyponatremia
  • Increase serum sodium but unclear of when to use in studies
  • Didn’t show to decrease hospitalizations, CV, or all cause mortality
31
Q

Hypernatremia

A
  • Na+ > 145
  • Always associated with hypertonicity and cellular dehydration (>295 mOsm)
  • Classified according to ECF status instead
  • Osmolality Symptoms: lethargy, weakness, and confusion/irritability that progresses to twitching, seizures, and coma (possibly death)
32
Q

Hypervolemic Hypernatremia

A
  • Gain of Sodium water, more sodium than water
  • Can be sodium overload or mineralcorticoid excess
  • Volume Signs: Edematous, pulmonary congestion
33
Q

Isovolemic Hypernatremia

A
  • Loss of water
  • Causes: diabetes insipidus, osmotic diuretics, hyperglycemia, impaired thirst/access to water
  • Volume status appears normal
34
Q

Hypovolemic Hypernatremia

A
  • Loss of water and sodium, loss of water greater than sodium
  • Causes: renal disorders, diuretics, diarrhea, laxative abuse, excess sweating
  • Volume Signs: postural hypotension, tachycardia, delayed capillary refill, poor perfusion signs
35
Q

Severe Hypernatremia Presentation

A
  • Decreases neuronal cell volume

- Rupture of cerebral vein, hemorrhages, and irreversible neurological damage

36
Q

Hypernatremia Treatment

A
  • Treat based on symptoms being volume or osmolality based
  • Hypovolemia => Normal saline
  • Hypervolemia => diuretics or dialysis plus D5W
  • Don’t need to correct sodium to normal (rapid correction can lead to AE)
  • Treat with D5W if symptoms of hyperosmolality (1 mEq/L/h if severe symptoms, decrease to 0.5 as symptoms improve)
  • Prevent recurrence by treating underlying condition
37
Q

Hypo/Hyper Treatment

A
  • ECF loss > Na loss
  • Restore intravascular volume with NS (200-300 mL/h to stabilize)
  • Once volume restored, switch to 1/2 NS or D5W to replace water deficit
38
Q

Central Diabetes Insipidus

A
  • Insufficiency of ADH
  • Treat with ADH analogue, vasopressin
  • DDAVP via nasal route preferred over oral
  • Titrate to achieve appropriate urine volume and serum sodium
39
Q

Nephrogenic Diabetes Insipidus

A
  • Insufficient response of kidneys to ADH
  • Dietary sodium restriction and thiazide diuretic
  • Can decrease urine volume by 50%
  • Increases proximal water absorption and decreases volume of filtrate delivered

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