Perioperative Fluid Management

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Perioperative Fluid Management

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Several area of research

• The kinetics of plasma volume expansion(PVE)
  produced by intravenous fluid
• The use of systemic oxygen delivery as a goal of
  resuscitation
• the effects of fluid therapy on cerebral
  hymodynamics

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The kinetics of plasma volume expansion produced
by intravenous fluids
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Prediction of plasma volume expansion using
static assumption

• static effect of fluid infusion on PVE
• PVE volume infused x (PV/Vd)
• Ex) 500ml blood loss with LRS or 0.9 saline.
• Vd ECV
• 500 vloume infused x (3/14)
• 2.3l infused volume necessary
• Fluid distribution volume

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The rate fluid filters through capillary membrane
into the interstitial space

• Q kA (Pc Pi) d (?i-?c)
• Q fluid filtration
• k the capillary hydrostatic pressure(conductive
  of water)
• A the area of the capillary membrane
• Pc capillary hydrostatic pressure
• Pi interstitial hydrostatic pressure
• d the reflection coefficient for albumin
• ?i interstitial colloid oncotic pressure
• ?c capillary colloid oncotic pressure

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Fluid filtration

• Ex) Increasing Pc or decreasing ?c
• - water and sodium filtered more rapidly
  than protein
• - resulting in preservation of Pc, dilution ?i
  , enhancement of lymphatic flow, preservation of
  the oncotic pressure gradient, the most powerful
  factor opposing fluid filtration

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Prediction of plasma volume expansion using
kinetic analysis

• Same purposes as pharmacokinetic analysis of drug
  concentration
• Estimation of the PVE and rates of clearance of
  infused fluid
• The effects of fluid infusion must be inferred
  from changes in the concentration of other
  variables
• Blood water concentration, serum albumin
  concentration, and total Hb

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Prediction of PV expansion using kinetic analysis

• Small proportion of crystalloid remaining in the
  vascular tree after equilibration

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Fluid requirement in the surgery and trauma

• Acute sequestration of interstitial fluid
• trauma, hemorrhage, tissue manipulation.
• during the first 10dys after resuscitation from
  massive trauma
• - decrease in ICV, increase in total body
  weight, increase in IFV.
• third postoperative day
• - accumulated fluid mobilize and return to the
  PV
• - Hypervolemia and pulmonary edema
• cardiovascular and renal system cannot
  compensate

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Systemic oxygen delivery as a goal of fluid
resuscitation

• Relation among postoperative complication ( ARF,
  hepatic failure, sepsis) and systemic oxygen
  delivery
• unrecognized, subclinical tissue hypoperfusion

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Systemic oxygen delivery(1)

• DO2 Q x CaO2 x 10
• DO2 systemic oxygen delivery
• Q cardiac output
• CaO2 arterial oxygen content
• DO2
• regulated through dilatation and constriction
  of vascular bed in response to change in regional
  and systemic oxygen consumption

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Systemic oxygen delivery(2)

• Average Q and DO2
• greater in high-risk surgical patient
• Heyland et al
• achieving recommended goal of cardiac index,
  oxygen delivery, oxygen consumption did not
  reduce mortality rate
• but improve outcome in surgical patient if
  treatment started before op
• Boyed et al
• - 107 high-risk surgical patient DO2 gt
  600mlO2.m.min treatment
• - decrease in the mortality rate

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Systemic oxygen delivery(3)

• Particular importance catecholamin used
  influence outcome
• Wilson et al
• inotropic support with dopexamine
• fewer complication and shorter hospital
  stays

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Systemic oxygen delivery(4)

• Aggressive elevation in DO2
• harmful
• Gattinoni et al and Metrangolo et al
• treatment supposed to increase oxygen
  delivery did not reduce mortality or morbidity
  rate in sepsis
• Some clinician
• increase oxygen delivery to specific target
  may be detrimental
• therapeutic intervention(dobutamin not
  dopexamin) disrupt individual organ function

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The effect of fluid therapy on cerebral
hemodynamic

• After simple hemorrhagic shock
• conventional fluid resuscitation increases ICP
  but does not consistency restore CBF
• The influence of resuscitation fluids on clinical
  outcome of patients with head injury requires
  continued investigation

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The normal BBB

• highly impermeable to sodium
• small changes in serum sodium exert greater
  osmotic pressure gradients than do large
  changes in serum protein concentrations
• enhances the influence on brain water of changes
  in serum sodium
• hypotonic solutions are more likely to increase
  the brain water content than 0.9 saline or
  colloid dissolved in 0.9 saline

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After traumatic brain injury

• BBB damaged
• Drummond et al
• after traumatic brain injury
• - clloid osmotic pressure influence brain
  water accumulation
• Hypertonic salt solutions
• acutely reduce brain water and therefore tend
  to reduce ICP
• In animal with intracranial mass lesions and
  hemorrhagic shock
• - also improved regional CBF and cerebral
  oxygen delivery

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Hypertonic solution for prehospital resuscitation

• Vassars et al
• compared 250ml LRS, 7.5 saline with 6
  dextran 70 for prehospital resuscitaion of trauma
  patient
• no overall difference in mortality rate
• in the subset of patient with severe head
  injury
• - 7.5 saline in 6 dextran 70 32
  survival
• - LRS 16 survival

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Hypertonic solution for prehospital resuscitation

• Simma et al
• children with severe head injury to receive
  either hypertonic saline or LRS
• hypertonic saline
• - fewer intervention to maintain ICPlt 15mmHg,
  fewer overall complication
• survival and duration of hospital stay
  similar

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Fluid management

• Current regimens
• sufficient to restore systemic perfusion in
  most patient undergoing surgery
• Important question
• frequency of complication of current fluid
  therapy
• the comparative advantage of different fluid
  formulation