Predicting fluid responsePredicting fluid responsein the critically illin the critically ill

Dr. Andrew FergusonDr. Andrew Ferguson

Consultant in Anaesthesia & Intensive Care MedicineConsultant in Anaesthesia & Intensive Care Medicine

Craigavon Area HospitalCraigavon Area Hospital

Approach to shockApproach to shock

Fluid challenge central to therapyFluid challenge central to therapy +/- CVP (and/or PA) monitoring+/- CVP (and/or PA) monitoring Repeat if CVP/PAWP still lowRepeat if CVP/PAWP still low Stop if CVP/PAWP goes highStop if CVP/PAWP goes high Surrogate markers for COSurrogate markers for CO

– LactateLactate

– SvOSvO22

So what’s the problem?So what’s the problem?

? validity of CVP as end-point? validity of CVP as end-point ? validity of PAWP as end-point? validity of PAWP as end-point Preload-SV relationship unknownPreload-SV relationship unknown Only 50% of patients fluid-responsiveOnly 50% of patients fluid-responsive Excess fluid problemsExcess fluid problems

– Interstitial fluid excessInterstitial fluid excess– Worsened gas exchangeWorsened gas exchange– Limitation of oxygen diffusionLimitation of oxygen diffusion

Variability of fluid response ratesVariability of fluid response rates

Michard (Chest 2002; 121: 2000-2008)

Preload does Preload does notnot guarantee response guarantee response

To be a fluid responder, To be a fluid responder, bothbothventricles must be on ascendingventricles must be on ascendingportion of Frank-Starling curveportion of Frank-Starling curve

Response depends on contractility and diastolic function as well as load

Common measures used to indicate Common measures used to indicate likelihood of responselikelihood of response

CVPCVP PAWPPAWP RVEDV (thermodilution)RVEDV (thermodilution) LVEDA (echo)LVEDA (echo)

R2 = 0.2

In spontaneous resp. a fall > 1 mmHg in RAP has positive predictivevalue of 77-84% and negative predictive value of 81-93% for response

R2 = 0.33

ROC curve minimal correlation

They don’t workThey don’t work------

what next??what next??

BP change relates to SV changeBP change relates to SV change

Cardio-pulmonary interactionsCardio-pulmonary interactions

Changes in SV, PP, SBP with positive pressure ventilation

Increased pleural pressureIncreased pleural pressure

RV preload fallsRV preload falls LV afterload fallsLV afterload falls

Increased transpulmonary pressureIncreased transpulmonary pressure

RV afterload increasesRV afterload increases LV preload increased byalveolar vessel squeeze

LV preload increased byalveolar vessel squeeze

Decreased RVSV Increased LVSV

Inspiratory decrease in RVSV

Expiratory decrease in LVSV

Expiratory decrease in LV preload

Pulmonary transit time

Stroke volume variation and LVEDPStroke volume variation and LVEDP

Potential toolsPotential tools

Stroke volume variationStroke volume variation Systolic pressure variationSystolic pressure variation Pulse pressure variationPulse pressure variation Peak aortic blood flow velocity variationPeak aortic blood flow velocity variation

Systolic Pressure VariationSystolic Pressure Variation

down is theimportant one forfluid response

Systolic pressure variationSystolic pressure variation

SP as indicator of fluid responseSP as indicator of fluid response

Pulse pressure variationPulse pressure variation

PP as indicator of fluid responsePP as indicator of fluid response

Measures of Measures of response toresponse to

volume volume

Predictive valuesPredictive valuesStudyStudy No. of No. of

patientspatientsMeasureMeasure ThresholdThreshold Positive Positive

pred. val.pred. val.Negative Negative pred. val.pred. val.

MagderMagder 3333 RAPRAP

(SPONT)(SPONT)

1 mmHg1 mmHg 8484 9393

TavernierTavernier 3535 DownDown 5 mmHg5 mmHg 9595 9393

Magder & Magder & LagonidisLagonidis

2929 RAPRAP

(SPONT)(SPONT)

1 mmHg1 mmHg 7777 8181

MichardMichard 4040 PPPP 13%13% 9494 9696

FeisselFeissel 1919 VPeakVPeak 12%12% 9191 100100

Problems withProblems with PP and PP and SVSV

Equipment not universalEquipment not universal Need sinus rhythmNeed sinus rhythm False positive in severe abdominal False positive in severe abdominal

distensiondistension

Normal valuesNormal values

PPPP 13%13% SPV SPV downdown 5%5% Vpeak Vpeak (aortic blood flow velocity)(aortic blood flow velocity) 12%12% SVSV 10%10%

ConclusionsConclusions

Conventional measures often not validConventional measures often not valid New and accurate measures availableNew and accurate measures available Consider passive leg raising!Consider passive leg raising! Know cardio-pulmonary interactionsKnow cardio-pulmonary interactions