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
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)
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
4
Q
Fluid Therapy Assessment
A
- In»_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
5
Q
Fluid Imbalance Goals
A
- Correction of volume depletion: input»_space; output
- Fluid Overloaded CHF: Output > Input
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
7
Q
Signs of Mild Volume Depletion (<10%)
A
- Thirst
- Decreased urine output
- Increased hematocrit
- Increased urine sp. gravity
8
Q
Signs of Modest Volume Depletion (20%)
A
- Dry mucous membranes
- Tachycardia
- Orthostatic Hypotension
- Increase BUN/Cr
- CNS (apathy, drowsy)
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
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
11
Q
Calculated Osmolality
A
2 * (Na+) + BUN/2.8 + Glucose/18
About 10 mOsm/kg less than actual since certain solutes are ignored
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
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
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)
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+
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
