Sodium and water: New insights

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Sodium and water New insights

• Jennifer Frontera, MD
• Medical Director
• Mount Sinai Neuro Science ICU

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Overview

• Basics of volume management in Neuro
• Assessing volume status
• Hyponatremia

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Basics of Fluids
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Normal Is and Os in 24 hours

• OUTPUT
• Urine- 500 ml
• Skin- 500 ml
• Respiratory 400 ml
• Stool- 200 ml

• INTAKE
• Ingested H2O-500 ml
• Water in food-800 ml
• Water of oxidation-300 ml

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Volume Balance

• Daily Weight- accounts for urine losses, as well
  as respiratory and GI
• Increased fluid loss with
• Fever- 100-150 ml/day with each degree over 37ºC
• Burns
• Tachypnea
• Surgical Drains
• GI losses
• Polyurea- DI, CEREBRAL SALT WASTING

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Effective Circulating Volume

• Nonmeasurable arterial volume that perfuses
  tissue
• ECV related to sodium balance
• 3 Baroreceptors
• Carotid sinus regulated ADH and sympathetic
  activity
• Glomerular afferent arterioles regulate
  renin-angiotensin and GFR
• Atria and ventricles release naturetic peptides
• Urine excretion of H2O regulated by ADH
• Urine excretion of Na regulated by aldosterone
  and atrial natiuretic factor

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Osmolality

• Osmolality regulated by water balance
• Water can freely crosses membranes moving from
  low to high osm to establish equilibrium
• Posm2Na glucose/18 BUN/2.8
• Normal Osm 275-290 mosmol/kg
• Osmolal gap measured serum osm- calculated Osm
  (normal 10-15 mOsm/Kg)
• Elevated Osm Gap
• Hyperproteinemia, hypertriglyceridemia
• Unmeasured Osm (Methanol, Ethylene glycol,
  Mannitol, Isopropyl Alcohol, Ethanol, Sorbitol,
  Glycerol, Acetone, Paraldehyde, Ether
  Trichlorethane)

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Assessing volume status- PA Catheter

• The benefits of PAC guided therapy have never
  been demonstrated
• Use may increase mortality
• Observational study of PAC during 1st 24 h of ICU
  stay (Connors JAMA 1996)
• Increased 30d mortality
• No subgroup benefit
• Not adjusted for pressor use
• Complications or misinterpretation of data
• Meta-analysis of RCT PAC neither increased
  mortality or hospital days nor associated with
  any benefit (Shah JAMA 2005)

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Assessing volume status- PA Catheter
RCT 1994 pts High risk gt60 yrs old Scheduled for
major Surgery No mortality difference LOS
similar More PE in PAC group
RCT of PAC vs CVC in 1000 pts with Acute lung
injury Mortality similar ICU LOS
similar Mechanical ventilation days similar Fluid
balance similar PAC group with 2x as many
catheter related complications
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CVP and volume status

• Meta-analysis of 24 studies and 803 pts
• CVP does NOT correlate with
• Measured blood volume
• Change in Stroke index/cardiac index
• volume responsiveness to fluid challenge
• Authors conclude CVP should not be used to make
  clinical decisions regarding fluid management
• PAOP also fails to predict volume responsiveness
  or SVI (Kumar Crit Care Med 2004)
• Suggestion use Flotrac SVV, SVI, Lidco, PiiCO

Marik Chest 2008
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Assessing volume status

• Non-invasive cardiac output, stroke volume and
  stroke volume variation (to estimate volume
  status)
• Pulse contour analysis, electrical bioimpedance
  (subtle changes in electrical conduction thru
  body over course of cardiac cycle)

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Flotrac
Flotrac cannot Correct for changing SVR/ afterload
Algorithm is dependent On waveform morphology
Unreliable if dampened Arterial waveform
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Flotrac and Stroke Volume Variation

• SVV estimates fluid responsiveness
• Higher SVV (gt13) patient is dry

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PiCCO

• Continuous cardiac output by analysis of arterial
  waveform
• Requires calibration (transpulmonary
  thermodilution) to account for changing SVR
• Recalibrate after change in patient position,
  therapy etc
• Uses central line larger arterial line (femoral
  or axillary)
• Less accurate than PA thermodilution
• Transpulmonary thermodilution gives additional
  info
• cardiac filling volume,
• intrathoracic lung volume,
• extravascular lung water

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LiDCO

• Uses lithium for calibration from peripheral
  artery to peripheral vein
• Does not give info. on cardiac filling volumes or
  extravascular lung water
• Calibration methods cannot be used too frequently
• Calibration errors in context of certain muscle
  relaxants
• Pulse contour algorithm is not dependent on
  waveform morphology

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TTE

• Estimates Ejection fraction
• RV EDV estimates preload, kissing ventricle
• IVC
• collapsability

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Back to the basics

• The exam
• Ins and outs
• Daily weights
• passive leg raise

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IV fluid choices in the Neuro ICU

• Rule 1 DO NOT USE HYPOTONIC FLUID unless you
  have a really really good reason
• Rule 2 Avoid Dextrose containing fluids

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Crystalloid
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Colloid

• Albumin
• May be neuroprotective- ALIAS, ALIASH trials
• Dextran, hespan
• polysaccharide
• Coagulopathy (platelet dysfunction, plasminogen
  activator), can cause cerebral edema, not used
  often in neuro
• Blood products

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Colloid vs. Crystalloid
NEJM 2004
RCT 6997 pts 4 Albumin vs. NS No difference in
LOS, MOF Renal replacement, vent days
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Colloid vs. Crytalloid
28 days
Subgroup of SAFE 460 pts with TBI Significance
driven by those with severe TBI (GCS 3-8) No
difference in ICP between groups No reports on
therapeutic interventions for ICP ICP defined as
gt30 mmHg, 2 episodes 30 min apart
24 months
NEJM 2007
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In our shop

• Flotrac, TTE, I/Os and daily wt to assess volume
  status
• Standard fluid is NS
• Transfuse for Hgb lt7 g/dL unless
• active bleeding,
• active cardiac or neurologic ischemia (target Hct
  30),
• or coagulopathic and bleeding or having a
  procedure

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Hyponatremia
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(No Transcript)
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Specific Etiologies to recognize

• True volume depletion Isotonic saline/volume
  resusitation
• Adrenal Insufficiency glucocorticoids directly
  supress ADH
• Hypothyroidism thyroid hormone
• Drug induced SIADH opiates, SSRIs

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SIADH

• CNS stroke, hemorrhage, infection, trauma,
  psychosis
• Tumors Small cell lung cancer, neuroblastoma,
  duodenal, pancreatic, head and neck
• Surgery
• HIV
• Drugs carbamezepine, oxcarbazepine,
  chlorpropamide, SSRIs, opiates, cyclophosphamide,
  haldol, amiodarone, cipro, ecstasy, pitressin

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Cerebral Salt Wasting

• Impaired sympathetic neural input
• Impaired renin and aldosterone release
• Failure of Na, uric acid and water absorption at
  proximal tubule
• BNP may decrease Na reabsorption and inhibit
  renin release
• SAH!!
• Carcinomatous/infectious meningitis,
  encepahlitis, polio, CNS tumors, post CNS surgery

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CSW vs. SIADH

• Hyponatremia
• High Urine Osm
• Low Serum Osm
• Urine Na gt 40 meq/L
• Low Serum Uric Acid
• HYPOVOLEMIC
• OutgtIn

• Hyponatremia
• High Urine Osm
• Low Serum Osm
• Urine Na gt 40 meq/L
• Low Serum Uric Acid
• EUVOLEMIC
• OutIn

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Acute vs. Chronic

• Acute- lt24 h
• Correct rapidly if severely symptomatic
  (seizures, coma, herniation)
• 1.5-2 meq/L per hour until symptoms resolve
• Hypertonic saline

• Chronic gt24-48 h
• idiogenic osmoles are produced
• Central Pontine Myelinolysis- HA, lethargy, coma,
  seizures, focal signs
• Most common if raise Nagt
  20 meq/d, and if Nalt105 meq/L
• 8-10 meq/d if chronic hyponatremia, lt18 meq/L in
  48 h

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Treatment

• SIADH
• Fluid restriction (really free water restriction)
• Hypertonic saline
• Salt tabs (urine osmolality fixed, so increased
  solute increases urine volume and raises serum
  Na)
• V2 receptor antagonist-
• Pure H20 diuresis

• CSW
• Replace Na and water
• NS, hypertonic, fludrocortisone, salt tabs
• DO NOT VOLUME RESTRICT SAH PATIENTS!
• POTENTIATES INFARCTS FROM VASOSPASM

• Widjicks Clin Neurol Neurosurg 1990, Naval CCM
  2006

• SALT trial of tolvaptan Schrier NEJM 2006

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450 mg/L
650 mg/cup
1160 mg/cup
Chicken Chow Foon 2700-3600 mg/serving
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Vaptans

• Tolvaptan oral, selective V2 antagonist
• Conivaptan- IV, V2 and V1a antagonist
• Both approved for euvolemic hyponatremia, SIADH
• Tolvaptan approved for heart failure and cirrosis
• Concerns that V1a antagonism might
• lower BP
• increase risk of variceal bleeding,
• or worsen renal function

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Efficacy of Vaptans

• Conivaptan RCT of 84 pts with euvolemic or
  hypervolemic hyponatremia (Na 115-130),
  conivaptan x 4 days
• raised Na 6.3 meq (40 mg/d dose) or
• 9.4 meq (80 mg/d dose) (Zeltser Am J Nephrol
  2007)
• Tovaptan RCT SALT1 and SALT2 trials 448 pts
  with SIADH, cirrosis or heart failure (300 per
  tablet)
• Significant increase c/w placebo (135 vs 130
  meq/L at day 4) and (136 vs. 131 at 30d) (Schrier
  NEJM 2006)

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Vaptans in the Neuro ICU

• 19 pts received 25 doses of conivaptan and Na
  ?5.8 meq/L in 12 h, 70 maintained Na x 72 h
  (Murphy Neurocrit Care 2009)
• 22 pts 86 had 6 meq over 13 h, 5 pts had
  infusion site reaction, 1 pt hypotension (Wright
  Neurocrit Care 2009)
• 6 pts with hyponatremia and depressed GCS
  randomized to usual care vs. conivaptan (249
  screened)
• Conivaptan led to higher serum Na at 6, 24, and
  36 h (Naidech Neurocrit Care 2010)

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Conclusions

• CVP/PAC not useful for assessing volume status-
  DONT BOTHER
• Flotrac/PiCCO/LidCo, TTE /- volume challenge, or
  I/Os, daily wts better for volume status
• Avoid hypotonic fluid and dextrose
• Do not volume restrict SAH patients with
  hyponatremia- treat as CSW
• Treatment for hyponatremia in NeuroICU includes
  salt tabs, hypertonic saline, flurinef, high salt
  diet
• Vaptans are an option for euvolemic hyponatremia

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The End
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Total Body Water

• 50-60 of body mass in adults
• Fat has lower water content than muscle (lower
  percentage of body wt in obese)

Intracellular 60-65
Intravascular 25-30
Extracellular 35-40
Interstitial 10
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Indications for insertion
Indications for PAC
In SAH in observational PAC study using
historical control Decreased pulm edema, sepsis
and mortality (Neurocrit care 2005)
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Flotrac
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Transfusion Indicated for

• Active bleeding
• Intra-operative blood loss
• Coagulopathy/ anti-platelet reversal in patients
  with bleeds or going to OR
• ? Phlebotomy associated anemia, idiopathic
  thrombocytopenia?
• ? Acute Ischemia? Cardiac or neurologic
  (vasospasm, acute stroke)

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Colloid- Blood ProductsUps and Downs of
Transfusion
Improved O2 delivery Tissue perfusion
Acute and delayed hemolytic rx Fever Volume
overload Pulmonary Edema (FFP worst) TRALI/ARDS DI
C Post-transfusion purpura (7-10d after
tx) Nosocomial Infection Hypothermia Alkalosis/Cit
rate toxicity Hypocalcemia
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Case

• A 35 yo W is competing in her first long distance
  bike race
• Her physician instructs her to ingest as much
  water as possible, even if she is not thirsty.
• Over the course of 2 hours she imbibes 6 L of H2O
• Her friends notice she has become disoriented.

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Case

• She is taken to the hosptial where she has a
  generalized tonic clonic seizure in the ambulance
• On exam her pupils are sluggish and she is
  extensor posturing bilaterally
• Her admission Na is 103 meq/L

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Admission HCT
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Case

• Do you
• Volume restrict- this is SIADH
• Rapidly correct Na with hypertonic saline as the
  patient is acutely hyponatremic and symptomatic
• Slowly correct the Na lt8 meq/d to avoid central
  pontine myelinolysis

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Case

• A 42 yo W develops the WHOL, nausea, vomiting and
  R sided weakness
• She is admitted to your hospital and intubated
• Admission Na is 142 meq/L

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Admission CT
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Case

• The patient undergoes uncomplicated ACOMM coiling
• On SAH Day 5 the patients Na is 130.
• The I/O are 1200/3000
• Do you
• Fluid restrict to 1 L
• Give salt tabs
• Use hypertonic saline to give back Na and fluid