Fluid Responsiveness

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Fluid responsiveness in critical care pediatrics:

Fluid responsiveness in critical care pediatrics Dr Isha Deshmukh M.D. Pediatrics

Slide 2:

‘‘will my patient’s cardiac output increase following volume expansion?’’ ‘‘is my patient preload dependent / not?’’

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The ability to identify patients who would respond to fluid administration by increasing stroke volume and hence cardiac output is of vital importance. The recent increase of research interest in this field reflects the evidence that early fluid optimization of critically ill patients improves outcome.

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The current internationally recommended first line therapy for hypotensive critically ill patients is a “fluid challenge ” Hypotension in this setting can be due to various causes like cardiac failure, actual or relative hypovolemia, vasoplegia etc occurring either in isolation or in combination.

Clinical indices of the adequacy of tissue/organ perfusion:

Clinical indices of the adequacy of tissue/organ perfusion • Mean arterial pressure Cerebral and abdominal perfusion pressures • Urine output • Mentation • Capillary refill • Skin perfusion/mottling • Cold extremities (and cold knees) • Blood lactate • Arterial pH, BE, and HCO3 • Mixed venous oxygen saturation SmvO2 (or ScvO2) • Mixed venous pCO2 • Tissue pCO2 • Skeletal muscle tissue oxygenation (StO2)

Concept………………………………:

Concept……………………………… Too little fluid may result in tissue hypoperfusion and worsen organ dysfunction Over-prescription of fluid also appears to impede oxygen delivery and compromise patient outcome.

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If we are giving fluids we should have a cardiovascular response. SV and CO should rise

Clinical studies have, however, demonstrated that only approximately 50% of hemodynamically unstable critically ill patients are volume-responsive:

Clinical studies have, however, demonstrated that only approximately 50% of hemodynamically unstable critically ill patients are volume-responsive Marik PE, Cavallazzi R, Vasu T, Hirani A: Dynamic changes in arterial waveform derived variables and fluid responsiveness in mechanically ventilated patients. A systematic review of the literature . Crit Care Med 2009, 37:2642-2647

Michard F, Teboul JL. Predicting fluid responsiveness in ICU patients. A critical analysis of the evidence. Chest 2002;121:2000e8. :

Michard F, Teboul JL . Predicting fluid responsiveness in ICU patients. A critical analysis of the evidence. Chest 2002;121:2000e8 . Marik PE, Baram M, Vahid B. Does central venous pressure predict fluid responsiveness? A systematic review of the literature and the tale of seven mares. Chest 2008;134:172e8 .

Frank-Starling relationship:

Frank-Starling relationship Describes the intrinsic ability of the heart to adapt to increasing volumes Normal cardiac physiology – ‘the energy of contraction is proportional to the initial length of the cardiac muscle fibre’. .

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Stroke volume Preload Fluid responsiveness Fluid unresponsiveness Fluid responsiveness is related to cardiac responsiveness

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In physiological terms, predicting fluid responsiveness seeks to identify patients who are on the steep part of the Frank Starling curve, who would increase their SV and hence CO in response to a fluid challenge.

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Stroke volume Preload Fluid responsiveness is related to cardiac responsiveness Normal heart Failing heart Fluid responsiveness Fluid unresponsiveness

Frank-Starling relationship:

Frank-Starling relationship Once the ventricle is functioning on the steep part of the Frank-Starling curve, there is a preload reserve. Volume expansion (VE) induces a significant increase in stroke volume. The pulse pressure (PPV) and stroke volume (SVV) variations are marked and the passive leg raising (PLR) and end-expiratory occlusion (EEO) tests are positive. By contrast, once the ventricle is operating near the flat part of the curve, there is no preload reserve and fluid infusion has little effect on the stroke volume. There is a family of Frank-Starling curves depending upon the ventricular contractility

Pressure Parameters Volume Parameters:

Pressure Parameters Volume Parameters Right ventricular filling pressures can be obtained from CVP. Left Ventricular filling pressures – indirectly from PCWP - PAC Left ventricular EDV. Left ventricular End diastolic area using Echocardiography.

Pulse pressure variation:

Pulse pressure variation The dynamic parameters of fluid responsiveness are related to cardiopulmonary interactions in patients under general anesthesia with mechanical ventilation. Far superior to static indicators (such as central venous pressure) Single arterial pressure waveform [systolic pressure variations (SPV), and pulse pressure variations (PPV)]. These new monitoring parameters can more readily predict the need for fluid administration to improve cardiac output and perfusion as compared to more invasive cardiac output monitoring.

FROM KUSSMAUL’S PULSUS PARADOXUS TO RESPIRATORY VARIATIONS IN THE PULSE OXIMETER PLETHYSMOGRAPHIC WAVEFORM AMPLITUDE:

FROM KUSSMAUL’S PULSUS PARADOXUS TO RESPIRATORY VARIATIONS IN THE PULSE OXIMETER PLETHYSMOGRAPHIC WAVEFORM AMPLITUDE Pulsus paradoxus - Spontaneously breathing volunteers presenting with conditions which cause right ventricular dysfunction, impaired right ventricular filling, and raised atrial pressure.

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Inspiration – increase in negative intrathoracic pressure increase in venous return to the right heart Exaggerated ventricular interdependence displacement of the septum into the left ventricle reducing its size & volume Increase pulmonary vascular filling, decrease in left ventricular filling & stroke volume.

Patients with mechanical ventilation and no spontaneous breathing activity:

Patients with mechanical ventilation and no spontaneous breathing activity

Heart-lung interactions Hemodynamic effects of mechanical ventilation. The cyclic changes in left ventricular (LV) stroke volume are mainly related to the expiratory decrease in LV preload due to the inspiratory decrease in right ventricular (RV) filling:

Heart-lung interactions Hemodynamic effects of mechanical ventilation . The cyclic changes in left ventricular (LV) stroke volume are mainly related to the expiratory decrease in LV preload due to the inspiratory decrease in right ventricular (RV) filling

In patients under general anesthesia :

In patients under general anesthesia Intermittent positive-pressure ventilation cyclic changes in the loading conditions of the left and right ventricles. cyclic changes in vena cava blood flow, pulmonary artery flow, and aortic blood flow During inspiration, vena cava blood flow decreases (venous return decreases) according to the Frank-Starling relationship pulmonary artery flow decreases Approximately three beats later,  this decrease in pulmonary artery flow is transmitted to the left ventricle inducing a decrease in aortic stroke volume. Consequently, mechanically ventilated patients under general anesthesia have cyclic changes in left ventricular stroke volume due to changes in intrathoracic pressure.

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The reduction in RV preload and increase in RV afterload both lead to a decrease in RV stroke volume, which is at a minimum at the end of the inspiratory period. The LV preload reduction may induce a decrease in LV stroke volume, which is at its minimum during the expiratory period when conventional mechanical ventilation is used. The cyclic changes in RV and LV stroke volume are greater when the ventricles operate on the steep rather than the flat portion of the Frank-Starling curve.

Fluid responsiveness:

Fluid responsiveness ‘Fluid responsiveness’ is defined as the ability of SV to increase in response to a fluid infusion or a “fluid challenge”. Weil and Henning introduced the concept of a “fluid challenge”. Weil MH, Henning RJ. New concepts in the diagnosis and fluid treatment of circulatory shock. Anesth Analg 1979;58:124e32.

Parameters involved in a fluid challenge. :

Parameters involved in a fluid challenge. Choice of fluid - Colloid (usually) Amount to be infused - 250 ml or 3 ml/kg Duration of infusion - 5-10 min Adequacy of challenge - Change in CVP of 2 cm H2O Target parameter - MAP, SV, CO Assessment time frame - Variable depending on CO monitor used Positive response -Increment of SV/CO by 10-15%

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Advantages of a resuscitation strategy involving fluid challenges include: 1. Testing preload reserve and quantification of the cardiovascular response to fluid administration. 2. Prompt correction of fluid deficit. 3. Minimising the risk of fluid overload and its subsequent complications.

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An ideal method to predict fluid responsiveness would be a cheap, direct, easy to perform, minimally invasive and continuous measurement with a high specificity and sensitivity. The fact that a multitude of methods is used to predict fluid responsiveness is a reflection of the lack of an ideal method. Currently used methods either use static or dynamic measurements.

Static measurements & Limitations:

Static measurements & Limitations CVP PAOP RV end-diastolic volume index (RVEDVI) LV end-diastolic area (LVEDA)

CVP:

CVP Magder’s maxim ‘‘no left-sided success without right-sided success.’’ Only right heart pressures (RAP - as a surrogate for right ventricular end-diastolic pressure [RVEDP]) and, hence, right ventricular preload (RVEDV) are assessed. The basis - effective regulation of CO through the right heart’s determination of venous return, independent of the left heart’s function.

External reference mark:

External reference mark In practice- the midaxillary line intersects a cross-sectional plane through the fourth intercostal space. Magder’s group , is a point 5 cm vertically below the sternal angle (at the junction of the sternum and the second rib costal cartilage). Figg and Nemergut – recent study. The investigators concluded that hospital-wide standardization of appropriate zero-point levels and staff education are required to minimize systematic errors in CVP measurement from interprovider variability.

The Effects of the Respiratory Cycle & Cardiac cycle:

The Effects of the Respiratory Cycle & Cardiac cycle At no point in the respiratory cycle (and definitely not at end-expiration) will the pleural pressure be close to zero. In such instances, which are common in ventilated patients, an accurate measurement of CVP cannot be made. Relationship of ventricular diastole and systole should be considered when interpreting CVP (and Ppao) pressure tracings.

Physiologic and Anatomic Properties of the Heart :

Physiologic and Anatomic Properties of the Heart heart failure or acute myocardial infarction hyperadrenergic states pulmonary hypertension tricuspid insufficiency- ‘‘ventricularize’’ the CVP waveform  resulting in an elevated mean CVP. tricuspid stenosis elevates the mean CVP, resulting in a gradient between the RAP and the RVEDP

STUDY TRIALS:

STUDY TRIALS In a prospective observational study of 83 patients admitted to a medical-surgical ICU, most of whom were nonseptic patients after cardiac surgery and all of whom had a PA catheter inserted, Magder and Bafaqeeh investigated fluid responsiveness over a range of CVP values in an attempt to identify a threshold CVP above which volume expansion was unlikely to increase cardiac output.

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66 pts  40- responders 26- non-responders. No patient responded when the CVP>13 3 of 12 pts with an initial CVP >10 mm Hg responded to fluids on their first trial. Nonresponders, however, were identified at all initial CVP levels. Conclusion- CVP >10 mm Hg (measured with a transducer leveled 5 cm below the sternal angle) indicates a low likelihood of improving CO in response to fluid challenge, with the caveat that nonresponders will still be found at CVPs less than 10 mm Hg..

Conclusion::

Conclusion: Hence, CVP is best viewed as a negative predictor of fluid responsiveness Magder S, Bafaqeeh F. The clinical role of central venous pressure measurements. J Intensive Care Med 2007;22(1):44–51 .

(CHEST 2008; 134:172–178) :

(CHEST 2008; 134:172–178)

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Meta-analysis of 24 studies incorporating 830 medical and surgical patients that examined both CVP and changes in CVP as predictors of intravascular blood volume and fluid responsiveness. In none of the studies was CVP able to predict either blood volume or fluid responsiveness. our results suggest that at any CVP the likelihood that CVP can accurately predict fluid responsiveness is only 56%.

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Fifteen hundred simultaneous measurements of blood volume and CVP in a heterogenous cohort of 188 ICU patients demonstrating no association between these two variables ( r 0.27). The correlation between CVP and change in blood volume was 0.1 ( r2 0.01). This study demonstrates that patients with a low CVP may have volume overload and likewise patients with a high CVP may be volume depleted.

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Summary- CVP should no longer be routinely measured in the ICU, operating room/ER. However, measurement of the CVP may be useful in select circumstances, such as in patients who have undergone heart transplant/in those who have suffered a RV infarction /acute PE. In these cases, CVP may be used as a marker of right ventricular function rather than an indicator of volume status.

Cardiac filling pressures are not appropriate to predict hemodynamic response to volume challenge. Crit CareMed 2007;35:64–8.:

Cardiac filling pressures are not appropriate to predict hemodynamic response to volume challenge. Crit CareMed 2007;35:64–8. Osman and colleagues- retrospectively analyzed prospective data on 150 fluid challenges in 96 patients with severe sepsis. Defining a response as a 15% or greater increase in CI, responders and nonresponders showed increases in Ppao and CVP after fluid challenge, with a baseline (preinfusion) Ppao difference that was slightly but statistically significantly lower in the responder group.

Study methods-:

Study methods- A total of 150 volume challenges in 96 patients were reviewed. In 65 instances, the volume challenge resulted in an increase in cardiac index of >15% (responders). The pre-infusion central venous pressure was similar in responders and nonresponders (8 4 vs. 9 4 mm Hg). The pre-infusion pulmonary artery occlusion pressure was slightly lower in responders (10 4 vs. 11 4 mm Hg, p < .05).

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The significance of pulmonary artery occlusion pressure to predict fluid responsiveness was poor and similar to that of central venous pressure, as indicated by low values of areas under the receiver operating characteristic curves (0.58 and 0.63, respectively). A CVP of <8 mm Hg and a PAOP of <12 mm Hg predicted volume responsiveness with a positive predictive value of only 47% and 54%, respectively. With the knowledge of a low stroke volume index (<30 mL·m2), their PPV were still unsatisfactory: 61% and 69% When the combination of CVP and PAOP was considered instead of either pressure alone, the degree of prediction of volume responsiveness was not improved.

Relationship between central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) before fluid loading in the overall population. Linear correlation: r .547, r .740, p .0001. :

Relationship between central venous pressure ( CVP) and pulmonary artery occlusion pressure ( PAOP) before fluid loading in the overall population. Linear correlation: r .547, r .740, p .0001.

Summary:

Summary Cardiac filling pressures are poor predictors of fluid responsiveness in septic patients. Their use as targets for volume resuscitation must be discouraged, at least after the early phase of sepsis has concluded.

Conclusion :

Conclusion Regardless of GEF, CVP may be useful for predicting fluid responsiveness in patients after coronary & major vascular surgery provided that PEEP is low. When GEF is low (<20%), PAOP is more useful than GEDVI for predicting fluid responsiveness, but when GEF is near-normal (≥20%) GEDVI is more useful than PAOP. This favors predicting & monitoring fluid responsiveness by PAC-derived filling pressures in surgical patients with systolic LV dysfunction & by trans pulmonary thermodilution derived GEDVI when systolic LV function is relatively normal.

Why the difference ??:

Why the difference ?? Patients with similar cardiac filling pressures may be on different parts of the Franke Starling curve as regards to their cardiac function. Hence, those in the steep part of the curve may not demonstrate an increase in filling pressure to a fluid challenge while those on the flat part of the curve may do so.

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It is the transmural pressure and not the intracavitary pressure such as (RAP) and PAOP that is related to EDV via the chamber compliance. Ventricular compliance is frequently altered in critically ill patients. The ventricular diastolic compliance curves are non-linear. In patients with isolated RV dysfunction, a fluid challenge may increase the right heart filling pressure even with low LV preload.

Slide 54:

RAP and PAOP have been shown to overestimate transmural pressures in patients with external or intrinsic positive end expiratory pressure (PEEP). Filling pressures can paradoxically decline after fluid repletion as a result of decreased sympathetic stimulation.

Superior vena cava collapsibility index and inferior vena cava distensibility index :

Superior vena cava collapsibility index and inferior vena cava distensibility index The changes in RAP during positive pressure ventilation are reflected on to the vena cavae. The subsequent change in their diameter can be measured using echocardiography. In mechanically ventilated patients, the SVC collapsibility index is calculated as the max diameter on expiration minus the min diameter on inspiration divided by the max diameter on expiration. Vieillard-Baron et al. have demonstrated that a threshold superior vena cava collapsibility index of 36% can reliably predict responders to fluid challenge with 90% sensitivity and 100% specificity in ventilated septic patients

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The inferior vena cava distensibility index (dIVC) is calculated as follows: maximum diameter (Dmax) minus minimum diameter (Dmin) divided by Dmin. Barbier et al. found that a dIVC threshold of 18% can reliably predict a responder with 90% sensitivity and 90% specificity.

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Because the AUC of the ROC curve for cIVC was 0.77 the present study shows that cIVC cannot reliably predict fluid responsiveness in spontaneously breathing patients with ACF. More precisely, a cIVC value below 40% cannot exclude fluid responsiveness while patients with cIVC above 40% are more likely to respond to fluid challenge. The 40% cutoff value is in agreement with recent studies

Pulse pressure variation Marik PE, Cavallazzi R, Vasu T, Hirani A. Dynamic changes in arterial waveform derived variables and fluid responsiveness in mechanically ventilated patients- a systematic review of the literature. Crit Care Med 2009;37:2642e7. :

Pulse pressure variation Marik PE, Cavallazzi R, Vasu T, Hirani A. Dynamic changes in arterial waveform derived variables and fluid responsiveness in mechanically ventilated patients- a systematic review of the literature. Crit Care Med 2009;37:2642e7.

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PPV is calculated as (PPmax PPmin)/ (Ppmax PPmin)/2, and is expressed as a percentage. The sensitivity & specificity of PPV to predict an increase in CO by 10-15% among patients admitted to intensive care was 89% and 88% . The area under the ROC curve was 0.94. The average threshold value for PPV predicting fluid responsiveness including different groups of patients is 12.5 1.6%.

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Systolic Pressure Variation (SPV) is the difference between maximal and minimal values of systolic blood pressure during one positive pressure mechanical breath. The correlation coefficient of SPV to predict fluid responsiveness in a mixed population of surgical and intensive care patients is 0.72 with an area under the ROC curve of 0.86 .

Pulse oximeter plethysmograph :

Pulse oximeter plethysmograph A 9.5-15% respiratory variation in pulse oximeter plethysmography waveform amplitude (ΔPOP) has been shown to be a modest predictor of fluid responsiveness in mechanically ventilated patients with a sensitivity of 81% and specificity of 78% and an area under ROC 0.88. Plethysmographic variability index (PVI) is an algorithm allowing for automated, non-invasive continuous monitoring of ΔPOP, derived from the perfusion index. PVI has shown a good ability to predict fluid responsiveness both in the intra-operative & intensive care patients with circulatory failure

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Loupec T, Nanadoumgar H, Frasca D, Petitpas F, Laksiri L, Baudouin D, et al. Pleth variability index predicts fluid responsiveness in critically ill patients. Crit Care Med 2011;39:294e9 .

Limitations of Dynamic Measurements:

Limitations of Dynamic Measurements 1.Controlled mechanical ventilation with no spontaneous breathing and no active expiration 2. Tidal volume of 8 ml/kg 3. Sinus rhythm without frequent ventricular or supraventricular ectopics 4. Absence of cor pulmonale 5. HR/RR >3.6 6. No change in autonomic nervous system activity (e.g. due to stimuli like pain, noise, anxiety) during measurements

Passive Leg Raising - PLR:

Passive Leg Raising - PLR PLR induces an ‘autotransfusion’ of blood from the lower limbs & abdominal compartment into the central circulation. The shifted volume is higher if the patient is moved from a recumbent position into a supine position with the legs elevated. Assessment of the haemodynamic response induced by PLR requires a monitor which calculates SV and CO almost real time, i.e., every few seconds.

Study data -:

Study data - A recent meta-analysis by Carvallo et al. showed that PLR induced changes in SV and CO is a good predictor of fluid responsiveness in critically ill patients. A PLR induced increase in SV and/or CO was found to have a sensitivity & specificity of 89% and 91% to predict fluid responsiveness, respectively. The pooled area under the ROC was 0.95.

Ad-disadvantages::

Ad-disadvantages: This manoeuvre, however, cannot be performed in all critically ill patients, especially those with spine, pelvic /limb fractures. Elastic compression stockings and elevated IAP can influence the volume recruited by PLR. One specific advantage that PLR has over other techniques is that PLR is a ‘ reversible self volume challenge’.

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The ability of pulse pressure variation to predict fluid responsiveness was inversely related to compliance of the respiratory system. If compliance of the respiratory system was <30 mL/cmH2O, then PPV became less accurate for predicting fluid responsiveness. However, the passive leg-raising and end-expiratory occlusion tests remained valuable in such cases. (Crit Care Med 2012; 40:000–000)

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Critical Care 2009, 13:R195 (doi:10.1186/cc8195 ) Conclusions PLR-induced changes in SV-Flotrac are able to predict the response to volume expansion in spontaneously breathing patients without vasoactive support.

The End…..:

The End…..

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