FLUIDS AND SOLUTIONS IN THE CRITICALLY ILL. Daniel De Backer Department of Intensive Care Erasme University Hospital Brussels, Belgium

Transcription

1 FLUIDS AND SOLUTIONS IN THE CRITICALLY ILL Daniel De Backer Department of Intensive Care Erasme University Hospital Brussels, Belgium

2 Why do we want to administer fluids? To correct hypovolemia? To increase cardiac output? To improve tissue perfusion? Fluids are indicated because we face a problem for which fluids may be the solution

3 How can we prescribe fluids? Just give x ml of fluids Up to a given value of CVP Perform a fluid challenge

4 Why do we want to perform a fluid challenge?

5 STARLING RELATIONSHIP Stroke volume Preload DDB USI

6 STARLING RELATIONSHIP Stroke volume Preload DDB USI

7 The problem with CVP targets CVP 8 mmhg DDB USI

8 Central venous pressure Osman et al ICM 35:64; mmhg 96 pts 150 fluid challenges DDB USI

9 STARLING RELATIONSHIP Stroke volume Preload All indices of preload poorly predict fluid responsiveness! DDB USI

10 Respiratory variations in stroke volume Stroke volume Preload DDB USI

11 Respiratory variations in pulse pressure Michard F et al Anesthesiology 103:419;2005

12 SEPSIS Michard et al AJRCCM 162:134;2000 N= 40 Cut-off value: 13% DDB

13 Passive leg raising test Stroke volume Preload DDB USI

14 Why do we want to perform a fluid challenge? Not all patients respond to fluids Not all patients tolerate fluids A positive fluid balance is associated with poor outcome It is relevant to identify the patients who are likely to respond to fluid or not It is relevant to evaluate the response (and tolerance) to fluids when these are deemed indicated.

15 Whatever the method used to predict the response to fluids, it is important to evaluate if the response to fluids fits with our predictions. Measure cardiac output! (whatever the technique)

16 How can we assess the response to fluid challenge?

17 Changes in PP poorly track changes in stroke volume Monnet X et al CCM 2011 Fluids Fluids N=228 N=228 -X

18 The increase in arterial pressure depends on vascular tone and the impact on cardiac output Cardiac output Arterial pressure Preload Cardiac output In sepsis, the low vascular tone limits the usefulness of arterial pressure to detect significant changes in CO in response to fluids.

19 How can we estimate the changes in cardiac output induced by fluids? Arterial pressure and pulse pressure => neither sensitive nor specific Increase in urine output => not sensitive Decrease in lactate levels => delayed clearance Increase in CVP?

20 The increase in CVP does not reflect the change in cardiac output, it reflects the change in preload Cardiac output Cardiac output CVP CVP The increase in CVP is the price to pay, not a goal in itself.

21 How can we estimate the changes in cardiac output induced by fluids? Cardiac output monitoring thermodilution arterial pressure waveform analysis esophageal Doppler echocardiography bioreactance..

22 Response to fluids The absence of response to fluids may be due that the patient is not preload dependent (useless fluid challenge - false positive) or to an insufficient fluid load in a preload dependent patient (preload unaltered due to capillary leak - bleeding ) Measuring cardiac output alone will not help to discriminate between these two possibilities! => A preload assessment will help

23 FLUID CHALLENGE Pressure measurements can better evaluate the response to fluid challenge than volume measurements!

24 Pressure measurements can better evaluate the response to fluid challenge than volume measurements! Cardiac output Cardiac output Pressure Volume

25 How can we assess that fluids are tolerated?

26 THE MEANING OF INTRAVASCULAR PRESSURES Pressure measurements Central venous pressure (CVP) => limitation to venous return => peripheral edema Pulmonary artery occluded pressure (PAOP) => risk for hydrostatic pulmonary edema

27 Preload: pressure or volume? Pressure Whatever is measured, pressure and volume are linked! Stroke volume Stroke volume Volume Pressure Volume

28 EFFET OF A DECREASE IN VENTRICULAR COMPLIANCE LVDEP Decreased compliance normal It is in conditions where PAOP is less predictive of fluid responsiveness (altered LV compliance) that it is the most useful to assess fluid tolerance. LVEDV DDB USI

29 LVEDP Role of PAOP in the evaluation of tolerance to fluids (Impact of diastolic dysfunction) Decreased compliance normal LVEDV Stroke volume Stroke volume LVEDP LVEDV

30 Implications: Pression An increase in pressure or volume indicates an increase in preload A lack of change in LV volume may mask an increase in preload Patients with diastolic dysfunction have a narrow therapeutic window between fluid responsiveness and risk for pulmonary edema Débit Débit Volume Pressure Volume

31 FLUID CHALLENGE 500 ml of colloid or 1000 ml of crystalloid solution over 30 min in 100 or 250 ml aliquots Hemodynamic measurements before and during FC Safety rules for stopping FC (increase in PAOP, CVP ) Evaluation of effectiveness Positive test: increase in CO of at least 10-15% Negative test: absence of change in CO despite increase in PAOP/CVP Non definite: no change in CO and in PAOP/CVP

32 FLUID CHALLENGE 500 ml of colloid or 1000 ml of crystalloid solution over 30 min in 100 or 250 ml aliquots Hemodynamic measurements before and during FC During the fluid challenge: Safety rules for No stopping change in FC vasoactive (increase drugs in PAOP, CVP ) No nursing procedures No physiotherapy Evaluation of effectiveness No stimulation Positive test: increase in CO of at least 10-15% Negative test: absence of change in CO despite increase in PAOP/CVP Non definite: no change in CO and in PAOP/CVP

33 Why do I perform a fluid challenge? When my preferred tool predicted that my patient would respond to fluids: To monitor the effects of fluids To evaluate whether fluids are tolerated When prediction of fluid responsiveness is difficult: Prediction is unreliable or unfeasible The grey zone concept

34 Pulse pressure/stroke volume variations: The limitations? Mechanical ventilation Tidal volume 8 ml/kg Deep sedation No respiratory movements Arrhythmias Increased abdominal pressure

35 Prediction of fluid responsiveness in patients with respiratory movements Heenen et al Crit Care 2006

36 Passive leg raising test: The limitations? Insufficient modification of preload compressive stockings severe vasoconstriction Increased abdominal pressure Risk of vomiting/aspiration (bowel occlusion!) Pain / stress

37 The dichotomic world of a perfect variable Variations in Stroke Volume (%) No Yes Likelihood of response to fluids

38 But fluid responsiveness is a continuum, not an on/off phenomenon! Variations in Stroke Volume (%) Yes No Likelihood of response to fluids

39 The grey zone concept Cannesson M et al Anesthesiology 115:231; 2011 N = 413 (surgery)

40 The cut off value is context dependant Cut off value What do you really want? Best compromise between Se and Sp? Highest sensitivity? Highest specificity? Se The cut off should not be the same for all (risk / benefits of fluids are not identical) 1-Sp DDB

41 The classical fluid challenge Conclusions The fluid challenge is not a way to predict the response to fluids. The fluid challenge is indicated to monitor the effects of fluids and to evaluate whether these are tolerated. The fluid challenge is thus the safest way to administer fluids when these are judged to be indicated.

42 CRYSTALLOIDS VS COLLOIDS? Restore/increase rapidly intravascular blood volume H2O / glucose Saline /Ringer's Intracellular volume Colloids Extracellular volume Intravascular DDB USI

43 SAFE Study 6997 pts Finfer et al NEJM 350:2247;2004

44 Crystalloids vs colloids? The SAFE Study Investigators, N Engl J Med 2004;350:

45 Finfer S ICM 37:86;2011

46 Albumin in septic patients (SAFE study) Multivariate analysis Finfer S ICM 37:86;2011 N = 1203

47 Albumin in septic patients (SAFE study) Finfer S ICM 37:86;2011 *$ *$ OR death 0.71 ( ) N = 1203

48 Type of fluids? Crystalloids? Colloids? Albumin? Starches? => still controversial (several trials ongoing)