Fluids and Electrolytes

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Fluids and Electrolytes

• Bruce R. Wall, MD, FACP
• Texas Health Dallas Presbyterian
• October 14th, 2010

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RBF1000ml/min RPF600ml/minGFR120ml/min or
172.8L/day
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Key Concepts

• Volume status (EABV) think saline in ECF
• Cannot be measured in the lab
• TBW (Total Body Water) think Na mEq/L
  Laboratory result must examine the patient
• IV FLUID orders Volume - Water - K - Acid/base

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3 Key Concepts in Fluid and Electrolyte Physiology

• Cell membrane permeability
• Osmolality
• Electroneutrality

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Cell Membrane Permeability
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Osmolarity vs Osmolality

• Osmolarity is defined as the concentration of the
  solute per liter of solution
• Osmolality is concentration of the solute/kg
  solvent (usually plasma or urine)
• Sodium accounts for 97-98 of plasma osmolality
  (range 287 ? 7 mOsm/Kg)
• mOsm/kg 2XNa mEq/L (glucose mg/dL)/18
  (BUN mg/dL)/2.8

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Electroneutrality

• Primary extracellular cation is SODIUM
• Primary intracellular cation is POTASSIUM
• Plasma (ECF) is the only compartment readily
  accessible

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Body Fluid Compartments

• Adult humans are 50 - 70 water
• Women and the elderly have higher of body fat
  than young men, and thus less water.
• For all practical purposes, assume that
• TBW 0.60 X WT (kg)

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Body Fluid Compartments

• 70 kg male (TBW0.6 X wt)
• IntraCellFluid 28L (70 kg X 40 28)
• ECF 14L (70 kg X 20 14)
• Extravascular 10.5L (70 kg X 15 10.5)
• Intravascular 6.3L (70 kg X 9 6.3)

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Distribution of Sodium
Extracellular Na
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Intracellular
Plasma

EABV
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Body Fluid Compartments

• The composition of the ECF is roughly the same as
  the interstitial space with the exception of
  proteins which are trapped within the vascular
  lumens.
• The distribution of fluid between these two
  spaces is determined by Starling Forces.

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Volume Homeostasis

• ECF Volume is linked to total body sodium
• Important Total body sodium is not concentration
  
• Concentration depends not only on amount of
  sodium but also the amount of water
• Total body sodium is regulated by the kidneys
• Input minus output equals accumulation

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Volume Depletion (a.k.a
Hypovolemia)

• Decreased ECF volume is always sensed as a
  decrease in the Effective Arterial Blood Volume
  (EABV)
• The EABV signals the kidney whether to reabsorb
  or excrete sodium.
• No direct measure of the EABV, it is determined
  by blood volume, cardiac output, and systemic
  vascular resistance
• Decreased EABV results in Na retention and
  expansion of ECF volume

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Clinical Signs of Hypovolemia

• Orthostatic hypotension
• Tachycardia
• Flat neck veins
• Dry mucous membranes
• Absent axilliary sweat
• Decreased skin turgor
• Decreased CVP

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Common IV Fluids
Solution Glucose Na K Ca Cl- Lactate PO4 Mg
D5W 50 0 0 0 0 0 0 0
NS 0 154 0 0 154 0 0 0
D5NS 50 154 0 0 154 0 0 0
D5½NS 50 77 0 0 77 0 0 0
LR 0 130 4 3 109 28 0 0
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Management of Hypovolemia

• The primary fluid prescribed for hypovolemia is
  Normal Saline
• In the management of hypovolemia, there is no
  place for ½NS or D5W.
• Transfusion
• Albumin
• Hetastarch (Hespan ) or Plasmanate

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IV fluids continued

• Addition of an isotonic fluid (0.9 NaCl)
  expands the ECF but doesnt change the
  IntraCellularFluid
• Addition of a hypotonic fluid (D5W) will cause
  movement of water into the cells.
• Addition of a hypertonic fluid (3 saline) will
  cause movement of water out of the cells.

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Why is Normal Saline the drug of choice?

• If you give 1 Liter of Normal Saline (0.9 NaCl),
  the NaCl is restricted to the ECF, therefore the
  entire liter stays in this space. 75 (750 ml)
  in the interstitial fluid and 25 (250 ml) in the
  intravascular space.

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Body Fluid Compartments

• 70 kg male (TBW0.6 X wt)
• IntraCellFluid 28L (70 kg X 40 28)
• ECF 14L (70 kg X 20 14)
• Extravascular 10.5L (70 kg X 15 10.5)
• Intravascular 6.3L (70 kg X 9 6.3)

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IV Fluids what about 0.45 saline?

• Think of 0.45 NaCl as 500ml of saline and 500 ml
  of water.
• The saline distributes to the ECF compartment
  alone. 75 (375 ml) in the interstitial space
  and 25 (125 ml) in the intravascular space.
• The water distributes 66 (330 ml) to the
  intracellular space 33 (170 ml) to the ECF.
  Of the 170 ml to ECF, only 25 or 42.5 ml stays
  in the intravascular space.

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Fluid Prescriptions

• Thus of our 1L 0.45NaCl, only 125 42.5 167.5
  ml stays in the intravascular space

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When should you use hypotonic solutions?

• If there is a need to administer water to the
  patient (because of a water deficit state)
• Maintenance fluids (not volume replacement)
• D5W, D5¼NS or D5½NS may be used in combination
  with bicarbonate if there is a need to administer
  base.

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Clinical Signs Symptoms of Volume Expansion

• Jugular venous distension /- S3 gallop
• Dyspnea
• Ascites this could be debated
• Pulmonary edema
• Pleural effusions
• Peripheral edema (remember hypoalbuminemia)

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Management of Hypervolemia

• Goal of treatment
• Removal of extracellular fluid
• Loop Diuretics
• Salt restriction (PO and IV)
• Dialysis/CVVHD
• Phlebotomy
• Rotating tourniquets

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Pathways of Water Balance
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Calculate the Water Deficit

• 0.6 x (wt in Kg) X Na/140 1

The water deficit should be fixed in the form of
water (D5W or tap water). Water repletion is
over and above the maintenance fluids which may
be either isotonic or hypotonic.
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How do you write IV Fluid orders?Input output
accumulation

• Volume balance
• Water balance
• Potassium (deficit, CKD, Mg, presence of
  acidosis or alkalosis)
• Acid base (administration of bicarbonate or HCl)

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Case I Mild Hyponatremia

• 65 yo WF smoker _at_ small cell carcinoma
• No evidence of CHF on physical exam
• Na 122 mEq/l K6.1
• Mild respiratory acidosis GFR normal
• No dyrenium, amiloride, or aldactone
• Positive history for Lovenox (DVT) for 2 weeks

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Case I hyponatremia - continued

• PE normal vitals (no tilt) comfortable at
  rest extremities - no edema no
  confusion
• Random U Na elevated at 40 mEq/L
• Uosm 600 TSH is WNL
• 1) Differential Diagnosis
• 2) IV fluid orders (NPO for cardiac evaluation)

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Patient receives saline

• Diagnosis SIADH
• IV saline administered 1 liter 300mosm
• Urine 600 mosm, provides for excretion of 300
  mosm of sodium chloride in 500ml of urine
• Allows patient to keep 500 ml of water
• Sodium falls to 119 mEq/L

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Case II HIV possible sepsis

• 25 yo male with HIV
• Admitted with streptococcal sepsis with
  meningitis
• History of IVDA with baseline CKD
• ARF BUN 80mg creatinine 2.5mg
• Volume depletion on exam
• NPO (unresponsive) Mild metabolic acidosis
• Sodium 133 mEq/L
• IV fluids?

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Case III history of CHF

• 70 yo diabetic, known CHF, mild CKD
• Admitted with acute coronary syndrome
• NPO for cardiac cath
• Recent increase in diuretics caused acute
  deterioration in GFR BUN gt 110 creat
  2.2mg
• Euvolemic on exam (maybe a little dry?)
• Na 125mmole/L
• IV Fluids?

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Case IV DKA

• 45 yo WF IDDM X 20 yrs
• Non-functional glucometer
• NV for 18 hrs indigestion/pain for 2 hrs
• No dyspnea No blood in emesis or stool
• too sick to administer insulin
• PMH - DM HBP Lipids CKD

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DKA continued

• 130/60 tilting to 95/50 P110 R24 Afebrile
  Neck veins impossible to assess Lungs few
  rales, WOB increased Cor I/VI m,
  soft S3, increased HR Abdbenign,
  non-distended Ext 1edema
• WBC 12K Hct 35 2proteinuria 5-10 WBC/HPF
• EKG 2mm ST elevation III and AVF

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DKA continued

• Na 131 K 3.2 Cl- 104
• HCO3 5mEq/l BUN 70 Creat 2.0
• anion gap 22 mEq
• pH 7.18 pCO2 18 pO2 80
• (1.5)(HCO3) 8 /- 2mEq pCO2
• Dx? Volume status? Na? K?
• acid/base issues? IV fluids?

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Case V Rhabdomyolysis

• 24 yo SWAT team member of GPD
• August 1998 106 degrees in the shade
• full gear running drill - collapse in field
• BP 100/60 P 130 T 102.8 rectal
• Skin warm Neck veins nl Lungs clear
• Cor increased HR MS tender back/gluteal
  region, no edema

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Rhabdo continued

• Urine looks red scant volume heme
• U Na lt10 FeNa low Na 149
• K 5.9 Anion gap 22 Bun 15 Creat 2.4
• Ca 6.5 Phos 8.5 CPK 50,000
• As you rapidly cool down the patient
• Diagnosis? Volume status?
• Cause of Hyperkalemia?
• IVF orders?

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Case VI Ascites

• 65 yo retired engineer with known cirrhosis
• ETOH exposure Hx GIB/varices
• Meds Beta blocker Aldactone Furosemide
  (no
  NSAIDs)
• Decreased intake for several days increasing abd
  pain - severe, diffuse, no radiation minimal
  emesis no gross hemorrhage in stool

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Ascites continued

• PE barely awake confabulates barely follows
• tremulous T 101.8 BP 90/60 red palms
  spider angiomata muscle wasting massive
  ascites very tender abdomen guaiac positive
  stool 1 edema 2 ankles
• Lab WBC 20K Hct 34 Bili 4 albumin 2.4
  INR 2.5 AG 12 Na128 K 5.0 FeNalt1
  ascites with 3000 WBC and positive gram stain
• BUN 80 Creat 3mg Decreased U Na lt 15

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Ascites continued

• Differential diagnosis?
• Volume status?
• Acid base status?
• IV fluids? (TPN?)

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Case VII Metabolic acidosis

• Patient with recurrent diarrhea complains of
  muscle weakness
• No carpopedal spam, Trousseaus of Chvosteks
• EKG reveals ST-segment and T-wave changes and
  PVCs compatible with hypokalemia

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Case VII continued

• Plasma Na 140 meq/L
• K 1.3 meq/L
• CL- 117 meq/L
• HCO3 10 meq/L
• albumin 4.1 g/dL (3.5 5 g/dL)
• Ca 6.3 mg/dL (8.8 10.5
  mg/dL)
• arterial pH 7.26
• pCO2 23 mm Hg
• Correction MA effect K? Correct hypo Ca?

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Case VIII Chronic Li

• 40 yo female NPO X 48 hours post complicated
  cholecystectomy
• Admission Na 146 mmoles
• Developes profound hypotension requiring transfer
  to ICU (without myocardial infarction)
• Current Na 175 mmoles
• IV fluid orders?

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Case IX AKI

• 60 yo attorney ANURIC AKI SEPSIS
• MSOF lungs, cardiac, liver, renal, bone marrow,
  nutrition, skin, CNS
• Intermittent HD
• Na 130 K 3.3 BUN 40 mg Creat 5mg
• IVF orders? TPN? Tube feeds?

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Case X acute water intoxication

• 20 yo SMU student brought to ER by fraternity
• Unresponsive hypothermic hypotensive
• Sodium 106 mEq/L Mild azotemia
• Calculated water load gt 8 liters
• IVF?

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Summary

• Most common error in writing IV Fluid orders
• 1) administration of NS in pts with SIADH
• 2) inadequate volume replacement in sepsis or
  pre-renal azotemia
  

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Questions?

• Next month hemodialysis therapy

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Treatment of Hyponatremia
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Symptoms and Signs of Hyponatremia

• Symptoms
• Lethargy
• Headache
• Apathy
• Muscle Cramps and weakness
• Anorexia
• Nausea
• Agitation
• Psychosis

• Signs
• Abnormal sensorium
• Depressed deep tendon reflexes
• Hypothermia
• Pathologic reflexes
• Pseudobulbar palsy
• Seizures
• Tentorial Herniation
• Cheyne-Stokes respiration
• Coma
• Death

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Acute Symptomatic Hyponatremia

• Duration lt48 hrs
• Increase serum Na rapidly by approximately 2
  mM/L/hr until resolution of symptoms.
• Full correction probably safe, but not necessary
• Hypertonic Saline 1-2 ml/kg/hr
• Coadministration of Furosemide

Note The sum of urinary cations (U Na U K )
should be less than the concentration of infused
sodium to ensure excretion of electrolyte free
water.
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Cerebral Adaptation to Hyponatremia
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Chronic Symptomatic Hyponatremia

• Duration gt48 hrs or unknown
• Initial increase in serum Na by 10 or 10 mM/L
• Hypertonic Saline 1-2 ml/kg/hr
• Co-administration of Furosemide
• Perform frequent neurologic evaluations
  correction rate may be reduced with improvements
  in symptoms
• Perform frequent measurement of serum and urine
  electrolytes
• At no time should correction exceed rate of 1.5
  mM/L/hr, or increment of 15 mmol/day
• Change to water restriction upon 10 increase of
  Na, or if symptoms resolve

Note The sum of urinary cations (U Na U K )
should be less than the concentration of infused
sodium to ensure excretion of electrolyte free
water.
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Treatment of Severe Euvolemic Hyponatremia (lt125
mmol/L)
Severe Hyponatremia (lt125 mM/L)
Symptomatic
Asymptomatic
Acute Duration lt 48 hrs
Chronic Duration gt 48 hrs
Chronic Rarely lt 48 hrs

• Some Immediate Correction Needed
• Hypertonic Saline 1-2 ml/kg/hr
• Co-administration of Furosemide
• Change to water restriction upon 10 increase of
  Na, or if symptoms resolve
• Perform frequent measurement of serum and urine
  electrolytes
• Do not exceed 1.5 mM/L/hr, or 20 mM/d

• Emergency Correction Needed
• Hypertonic Saline 1-2 ml/kg/hr
• Coadministration of Furosemide

• Long Term Management
• Identification and Treatment of Reversible
  etiologies
• Water Restriction
• Demeclocycline 300 mg to 600 mg bid
• Urea 15 to 60g qd
• V2 receptor antagonists

No immediate correction needed
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Treatment of Asymptomatic Chronic Hyponatremia

• Fluid Restriction
• Pharmacologic Inhibition of Vasopressin Action
• Lithium
• Demeclocycline
• V-2 receptor antagonist
• Increase solute Excretion
• Furosemide 2-3 g of NaCl/day
• Urea 30 g/d
• Increased dietary protein intake

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Management of Non-Euvolemic Hyponatremia

• Hypovolemic Hyponatremia
• Volume restoration with isotonic saline
• Identify and correct etiology of water and sodium
  losses
• Hypervolemic Hyponatremia
• Water Restriction
• Sodium Restriction
• Substitute loop diuretics instead of thiazide
  diuretics
• Treatment of stimulus for sodium and water
  retention
• V2-receptor antagonist

SM Lauriat, T Berl The Hyponatremic patient
Practical Focus on Therapy. J Am Soc Nephrol,
1997, 8(11)1599-1607.
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The Hypernatremic Patient
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Guidelines for the Treatment of Symptomatic
Hypernatremia

• Correct at a rate of 2 mM/L/hr
• Replace half of the calculated water deficit over
  the first 12-24 hrs.
• Replace the remaining deficit over the next 24-36
  hrs.
• Perform serial neurologic examinations -
  prescribed rate of correction can be decreased
  with improvement in symptoms
• Measure serum and urine electrolytes every 1-2
  hrs.

Note If UNa UK is less than the
concentration of PNa, then there are ongoing
water losses that need to be replaced
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Treatment of Hyponatremia

• Three Key Questions
• Is the patient symptomatic?
• What is the duration of Hyponatremia?
• Are there any risk factors for the development of
  neurologic complications?