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Perioperative FluidManagement

R3

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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 ofresuscitation

the effects of fluid therapy on cerebralhymodynamics

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The kinetics of plasmavolume expansion producedby intravenous fluids

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Prediction of plasma volumeexpansion using static assumption static effect of fluid infusion on PVEPVE = 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 capillarymembrane into the interstitial space Q = kA [(Pc Pi) + (i-c)]Q = fluid filtrationk = the capillary hydrostatic pressure(conductive of water)

A = the area of the capillary membrane

Pc = capillary hydrostatic pressure

Pi = interstitial hydrostatic pressure

= 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 thanprotein

- resulting in preservation of Pc, dilution i ,enhancement of lymphatic flow, preservation of

the oncotic pressure gradient, the most powerfulfactor opposing fluid filtration

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Prediction of plasma volumeexpansion using kinetic analysis Same purposes as pharmacokinetic

analysis of drug concentration

Estimation of the PVE and rates ofclearance of infused fluid

The effects of fluid infusion must be

inferred from changes in theconcentration of other variables

Blood water concentration, serum albuminconcentration, and total Hb

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Prediction of PV expansionusing kinetic analysis Small proportion of crystalloidremaining in the vascular tree afterequilibration

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Fluid requirement in the surgeryand trauma Acute sequestration of interstitial fluid

;trauma, hemorrhage, tissue manipulation.

during the first 10dys after resuscitation frommassive 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 asa goal of fluid resuscitation

Relation among postoperative complication( ARF, hepatic failure, sepsis) and systemicoxygen 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 outputCaO2 ; arterial oxygen content

DO2; regulated through dilatation and constriction ofvascular bed in response to change in regional andsystemic 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 startedbefore op

Boyed et al- 107 high-risk surgical patient ; DO2 > 600mlO2.m.min

treatment

- decrease in the mortality rate

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Systemic oxygen delivery(3) Particular importance ; catecholamin usedinfluence 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 didnot reduce mortality or morbidity rate in sepsis

Some clinician; increase oxygen delivery to specific target may bedetrimental

; therapeutic intervention(dobutamin not dopexamin)disrupt individual organ function

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The effect of fluid therapy oncerebral hemodynamic

After simple hemorrhagic shock;conventional fluid resuscitation increases ICP but

does not consistency restore CBF

The influence of resuscitation fluids on clinicaloutcome of patients with head injury requirescontinued investigation

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The normal BBB highly impermeable to sodium

small changes in serum sodium exert greater

osmotic pressure gradients than do largechanges in serum protein concentrations

enhances the influence on brain water ofchanges in serum sodium

hypotonic solutions are more likely to increasethe brain water content than 0.9% saline orcolloid 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 forprehospital resuscitation

Vassars et al; compared 250ml LRS, 7.5% saline with 6%dextran 70 for prehospital resuscitaion of traumapatient

; 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 forprehospital resuscitation

Simma et al; children with severe head injury to receiveeither hypertonic saline or LRS

; hypertonic saline- fewer intervention to maintain ICP< 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 patientundergoing surgery

Important question; frequency of complication of current fluid therapy

; the comparative advantage of different fluid formulation