Predicting fluid response in ICU

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Predicting fluid responsein the critically ill : 

Predicting fluid responsein the critically ill Dr. Andrew Ferguson Consultant in Anaesthesia & Intensive Care Medicine Craigavon Area Hospital

Approach to shock : 

Approach to shock Fluid challenge central to therapy +/- CVP (and/or PA) monitoring Repeat if CVP/PAWP still low Stop if CVP/PAWP goes high Surrogate markers for CO Lactate SvO2

So what’s the problem? : 

So what’s the problem? ? validity of CVP as end-point ? validity of PAWP as end-point Preload-SV relationship unknown Only 50% of patients fluid-responsive Excess fluid problems Interstitial fluid excess Worsened gas exchange Limitation of oxygen diffusion

Variability of fluid response rates : 

Variability of fluid response rates Michard (Chest 2002; 121: 2000-2008)

Preload does not guarantee response : 

Preload does not guarantee response

To be a fluid responder, bothventricles must be on ascendingportion of Frank-Starling curve : 

To be a fluid responder, bothventricles must be on ascendingportion of Frank-Starling curve Response depends on contractility and diastolic function as well as load

Common measures used to indicate likelihood of response : 

Common measures used to indicate likelihood of response CVP PAWP RVEDV (thermodilution) LVEDA (echo)

Slide 9: 

R2 = 0.2 In spontaneous resp. a fall > 1 mmHg in RAP has positive predictive value of 77-84% and negative predictive value of 81-93% for response

Slide 10: 

R2 = 0.33

Slide 12: 

ROC curve minimal correlation

They don’t work---what next?? : 

They don’t work---what next??

BP change relates to SV change : 

BP change relates to SV change

Cardio-pulmonary interactions : 

Cardio-pulmonary interactions Changes in SV, PP, SBP with positive pressure ventilation

Slide 18: 

Increased pleural pressure RV preload falls LV afterload falls Increased transpulmonary pressure RV afterload increases LV preload increased by alveolar vessel squeeze Decreased RVSV Increased LVSV

Slide 19: 

Inspiratory decrease in RVSV Expiratory decrease in LVSV Expiratory decrease in LV preload Pulmonary transit time

Stroke volume variation and LVEDP : 

Stroke volume variation and LVEDP

Potential tools : 

Potential tools Stroke volume variation Systolic pressure variation Pulse pressure variation Peak aortic blood flow velocity variation

Systolic Pressure Variation : 

Systolic Pressure Variation Ddown is the important one for fluid response

Systolic pressure variation : 

Systolic pressure variation

DSP as indicator of fluid response : 

DSP as indicator of fluid response

Pulse pressure variation : 

Pulse pressure variation

DPP as indicator of fluid response : 

DPP as indicator of fluid response

Measures of response to volume : 

Measures of response to volume

Predictive values : 

Predictive values

Problems with DPP and DSV : 

Problems with DPP and DSV Equipment not universal Need sinus rhythm False positive in severe abdominal distension

Normal values : 

Normal values DPP 13% SPV Ddown 5% DVpeak (aortic blood flow velocity) 12% DSV 10%

Conclusions : 

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