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J Appl Physiol 97: 790-791, 2004; doi:10.1152/japplphysiol.00021.2004
8750-7587/04 $5.00
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LETTER TO THE EDITOR

Prediction of fluid responsiveness: searching for the Holy Grail

The following is the abstract of the article discussed in the subsequent letter:

The accuracy and clinical utility of preload indexes as bedside indicators of fluid responsiveness in patients after cardiac surgery is controversial. This study evaluates whether respiratory changes ({Delta}) in the preejection period (PEP; {Delta}PEP) predict fluid responsiveness in mechanically ventilated patients. Sixteen postcoronary artery bypass surgery patients, deeply sedated under mechanical ventilation, were enrolled. PEP was defined as the time interval between the beginning of the Q wave on the electrocardiogram and the upstroke of the radial arterial pressure. {Delta}PEP (%) was defined as the difference between expiratory and inspiratory PEP measured over one respiratory cycle. We also measured cardiac output, stroke volume index, right atrial pressure, pulmonary arterial occlusion pressure, respiratory change in pulse pressure, systolic pressure variation, and the {Delta}down component of SPV. Data were measured without positive end-expiratory pressure (PEEP) and after application of a PEEP of 10 cmH2O (PEEP10). When PEEP10 induced a decrease of >15% in mean arterial pressure value, then measurements were re-performed before and after volume expansion. Volume loading was done in eight patients. Right atrial pressure and pulmonary arterial occlusion pressure before volume expansion did not correlate with the change in stroke volume index after the fluid challenge. Systolic pressure variation, {Delta}PEP, {Delta}down, and change in pulse pressure before volume expansion correlated with stroke volume index change after fluid challenge (r2 = 0.52, 0.57, 0.68, and 0.83, respectively). In deeply sedated, mechanically ventilated patients after cardiac surgery, {Delta}PEP, a new method, can be used to predict fluid responsiveness and hemodynamic response to PEEP10.

Prediction of fluid responsiveness: searching for the Holy Grail

To the Editor: We have read with great interest the study by Bendjelid et al. (2) proposing a new tool to answer one of the most common clinical question in patients with shock: Can we improve stroke volume, cardiac output, and hence hemodynamics by giving fluid? Indeed, Bendjelid et al. (2) demonstrated that the respiratory variation in preejection period (the time interval between the Q wave on the ECG and the upstroke of the radial arterial pressure) is directly proportional to the stroke volume increase induced by a fluid challenge.

Fluid responsiveness has become an increasingly popular concept over the past few years (1, 8, 10). To date, 10 clinical studies (2–7, 12–15) have demonstrated the potential value of dynamic parameters in detecting patients who may benefit from volume loading. The arterial systolic pressure variation (SPV) and its expiratory component ({Delta}down) and the arterial pulse pressure variation ({Delta}PP), the Doppler aortic blood velocity variation, the pulse contour stroke volume variation, and the preejection period variation ({Delta}PEP) have successively been shown to be useful tools to predict fluid responsiveness. In contrast, static indicators of cardiac preload (e.g., cardiac filling pressures or dimensions) have been shown to be of minimal value (1, 8). Therefore, the superiority of dynamic over static parameters is now well documented.

However, what is the best dynamic parameter remains to be determined. Indeed, only very few studies have compared the value of dynamic parameters (2, 6, 15). Interestingly, Bendjelid et al. (2) compared the value of SPV, {Delta}down, {Delta}PP, and {Delta}PEP by looking at the r2 correlation coefficients (respectively, 0.52, 0.68, 0.83, and 0.57) between these parameters and the percent increase in stroke volume in response to volume loading. Using the same method, we provide in Fig. 1 a comparison of all dynamic parameters that have been shown to be related to the hemodynamic effects of a fluid challenge. When all studies are taken into account, the mean r2 correlation coefficient is 0.63, suggesting that the dynamic parameters, although much more valuable than static parameters, could still be improved.



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  		Fig. 1. Correlation coefficients (r2) between dynamic parameters (before fluid infusion) and the percent increase in stroke volume or cardiac output as a result of a fluid challenge. Each gray bar represents one study. Each black bar represents the mean r2 value for each parameter. SPV, arterial systolic pressure variation; {Delta}down, expiratory decrease in systolic pressure; {Delta}PP, arterial pulse pressure variation; {Delta}Vpeak, Doppler aortic blood velocity variation; SVV, pulse contour stroke volume variation; {Delta}PEP, preejection period variation.

 
In this regard, some concerns have recently been raised about the influence of tidal volume and lung or chest wall compliance on dynamic parameters. There is no doubt that the magnitude of changes in pleural pressure (which depends on both tidal volume and respiratory mechanics) influences the value of dynamic parameters (11). However, whether the magnitude of changes in pleural pressure may also influence fluid responsiveness remains to be determined (9). Interestingly, in patients with static compliances of the respiratory system ranging from 26 to 69 ml/cmH2O and ventilated with tidal volumes ranging from 5 to 10 ml/kg, Bendjelid et al. (2) have reported a very tight relationship (r2 = 0.83) between {Delta}PP and the percent increase in stroke volume. This finding supports the notion that the predictive value of dynamic parameters is relatively independent of tidal volume and respiratory mechanics. However, further studies are definitely required to clarify this issue.

REFERENCES

  1. Bendjelid K and Romand JA. Fluid responsiveness in mechanically ventilated patients: a review of indices used in intensive care. Intensive Care Med 29: 352–360, 2003.[ISI][Medline]
  2. Bendjelid K, Suter PM, and Romand JA. The respiratory change in preejection period: a new method to predict fluid responsiveness. J Appl Physiol 96: 337–342, 2004.[Abstract/Free Full Text]
  3. Berkenstadt H, Margalit N, Hadani M, Friedman Z, Segal E, Villa Y, and Perel A. Stroke volume variation as a predictor of fluid responsiveness in patients undergoing brain surgery. Anesth Analg 92: 984–989, 2001.[Abstract/Free Full Text]
  4. Coriat P, Vrillon M, Perel A, Baron JF, Le Bret F, Saada M, and Viars P. A comparison of systolic blood pressure variations and echocardiographic estimates of end-diastolic left ventricular size in patients after aortic surgery. Anesth Analg 78: 46–53, 1994.[Abstract/Free Full Text]
  5. Feissel M, Michard F, Mangin I, Ruyer O, Faller JP, and Teboul JL. Respiratory changes in aortic blood velocity as an indicator of fluid responsiveness in ventilated patients with septic shock. Chest 119: 867–873, 2001.[Abstract/Free Full Text]
  6. Michard F, Boussat S, Chemla D, Anguel N, Mercat A, Lecarpentier Y, Richard C, Pinsly MR, and Teboul JL. Relation between respiratory changes in arterial pulse pressure and fluid responsiveness in septic patients with acute circulatory failure. Am J Respir Crit Care Med 162: 134–138, 2000.[Abstract/Free Full Text]
  7. Michard F, Chemla D, Richard C, Wysocki M, Pinsky MR, Lecarpentier Y, and Teboul JL. Clinical use of respiratory changes in arterial pulse pressure to monitor the hemodynamic effects of PEEP. Am J Respir Crit Care Med 159: 935–939, 1999.[Abstract/Free Full Text]
  8. Michard F and Teboul JL. Predicting fluid responsiveness in ICU patients. A critical analysis of the evidence. Chest 121: 2000–2008, 2002.[Abstract/Free Full Text]
  9. Michard F, Teboul JL, and Richard C. Influence of tidal volume on stroke volume variation. Does it really matter? Intensive Care Med 29: 1613, 2003.[CrossRef][ISI][Medline]
  10. Pinsky MR. Functional hemodynamic monitoring. Intensive Care Med 28: 392–398, 2002.[CrossRef][ISI][Medline]
  11. Reuter DA, Bayerlein J, Goepfert MS, Weis FC, Kilger E, Lamm P, and Goetz AE. Influence of tidal volume on left ventricular stroke volume variation measured by pulse contour analysis in mechanically ventilated patients. Intensive Care Med 29: 476–480, 2003.[ISI][Medline]
  12. Reuter DA, Felbinger TW, Kilger E, Schmidt C, Lamm P, and Goetz AE. Optimising fluid therapy in mechanically ventilated patients after cardiac surgery by on-line monitoring of left ventricular stroke volume variations: a comparison to aortic systolic pressure variations. Br J Anesth 88: 124–126, 2002.[Abstract/Free Full Text]
  13. Reuter DA, Felbinger TW, Schmidt C, Kilger E, Goedje O, Lamm P, and Goetz AE. Stroke volume variations for assessment of cardiac responsiveness to volume loading in mechanically ventilated patients after cardiac surgery. Intensive Care Med 28: 392–398, 2002.[CrossRef][ISI][Medline]
  14. Reuter DA, Kirchner A, Felbinger TW, Weis FC, Kilger E, Lamm P, and Goetz AE. Usefulness of left ventricular stroke volume variation to assess fluid responsiveness in patients with reduced cardiac function. Crit Care Med 31: 1399–1404, 2003.[CrossRef][ISI][Medline]
  15. Tavernier B, Makhotine O, Lebuffe G, Dupont J, and Scherpereel P. Systolic pressure variation as a guide to fluid therapy in patients with sepsis-induced hypotension. Anesthesiology 89: 1313–1321, 1998.[CrossRef][ISI][Medline]

Frédéric Michard
Ulrich Schmidt
 Department of Anesthesia and Critical Care
Massachusetts General Hospital-Harvard Medical School
Boston, Massachusetts 02114
E-mail: fmichard@partners.org

 

REPLY

To the Editor: We thank Drs. Michard and Schmidt for their interest in our article (2) and for their additional comments. We take the opportunity to respond to their letter, which puts forward the potential value of dynamic parameters in detecting patients who may benefit from volume loading, in regard to our recent study (2). The comments provided were appreciated and in some measure correct.

Indeed, they have reanalyzed data from 14 studies in an attempt to demonstrate that dynamic parameters have been shown to be related to hemodynamic effects of a fluid challenge (their Fig. 1). However, Michard and Schmidt have omitted to add the study of Wiesenack et al. (4), which suggests, in contrast to other recent studies (1, 3), that stroke volume variation derived from pulse contour analysis could not serve as an indicator of fluid responsiveness in cardiac surgical patients. This work reminds us that critical care pathophysiology is fascinating but not simple.

REFERENCES

  1. Bendjelid K and Romand JA. Fluid responsiveness in mechanically ventilated patients: a review of indices used in intensive care. Intensive Care Med 29: 352–360, 2003.[ISI][Medline]
  2. Bendjelid K, Suter PM, and Romand JA. The respiratory change in preejection period: a new method to predict fluid responsiveness. J Appl Physiol 96: 337–342, 2004.
  3. Michard F and Teboul JL. Predicting fluid responsiveness in ICU patients. A critical analysis of the evidence. Chest 121: 2000–2008, 2002.[Abstract/Free Full Text]
  4. Wiesenack C, Prasser C, Rodig G, and Keyl C. Stroke volume variation as an indicator of fluid responsiveness using pulse contour analysis in mechanically ventilated patients. Anesth Analg 96: 1254–1257, 2003.[Abstract/Free Full Text]

Karim Bendjelid
Jacques-André Romand
 Division of Surgical Intensive Care
Department of Anaesthesiology, Pharmacology, and Surgical Intensive Care
Geneva University Hospitals
CH-1211 Geneva 14, Switzerland
E-mail: karim.bendjelid{at}hcuge.ch





This Article
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Right arrow Articles by Michard, F.
Right arrow Articles by Romand, J.-A.

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