Reply from the authors

Abstract

Editor'We would like to thank Dr Stricker and colleagues for their constructive feedback and comments regarding our study.1Pereira de Souza Neto E Grousson S Duflo F et al.Predicting fluid responsiveness in mechanically ventilated children under general anaesthesia using dynamic parameters and transthoracic echocardiography.Br J Anaesth. 2011; 106: 856-864Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar We concur that further studies in the setting of clinically significant hypovolaemia are needed in order to assess the accuracy of dynamic parameters of fluid responsiveness in children. While dynamic parameters have been demonstrated to be strong predictors of fluid responsiveness in adults,2Marik 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: 2642-2647Crossref PubMed Scopus (875) Google Scholar their accuracy in children is still debated and recently published papers, including animal ones, have found conflicting results.3Renner J Meybohm P Gruenewald M et al.Global end-diastolic volume during different loading conditions in a pediatric animal model.Anesth Analg. 2007; 105: 1243-1249Crossref PubMed Scopus (23) Google Scholar, 4Renner J Gruenewald M Meybohm P et al.Effect of elevated PEEP on dynamic variables of fluid responsiveness in a pediatric animal model.Paediatric Anaesth. 2008; 18: 1170-1177PubMed Google Scholar, 5Renner J Cavus E Meybohm P et al.Pulse pressure variation and stroke volume variation during different loading conditions in a paediatric animal model.Acta Anaesthesiol Scand. 2008; 52: 374-380Crossref PubMed Scopus (30) Google Scholar, 6Durand P Chevret L Essouri S Haas V Devictor D Respiratory variations in aortic blood flow predict fluid responsiveness in ventilated children.Intensive Care Med. 2008; 34: 888-894Crossref PubMed Scopus (98) Google Scholar In our study, we have shown that dynamic variables such as respiratory variation in arterial pulse pressure (DeltaPP and PPV) or in the plethysmographic waveform amplitude (DeltaPOP and PVI) were not able to predict fluid responsiveness in children undergoing general surgery.1Pereira de Souza Neto E Grousson S Duflo F et al.Predicting fluid responsiveness in mechanically ventilated children under general anaesthesia using dynamic parameters and transthoracic echocardiography.Br J Anaesth. 2011; 106: 856-864Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar Dr Stricker points out that these variables may not be reliable in the setting we studied (neurosurgical patients immediately after induction of anaesthesia) but that they may be accurate during severe hypovolaemia. We personally believe that these indices may detect hypovolaemia and may be predictive of fluid responsiveness during severe haemorrhage. However, the interest of these indices would be limited if they could only detect severe hypovolaemia. Originally, the guiding principle of these variables was to detect hypovolaemia very early.7Perel A Pizov R Cotev S Systolic blood pressure variation is a sensitive indicator of hypovolemia in ventilated dogs subjected to graded hemorrhage.Anesthesiology. 1987; 67: 498-502Crossref PubMed Scopus (312) Google Scholar 8Pizov R Eden A Bystritski D Kalina E Tamir A Gelman S Arterial and plethysmographic waveform analysis in anesthetized patients with hypovolemia.Anesthesiology. 2010; 113: 83-91Crossref PubMed Scopus (49) Google Scholar If DeltaPP/DeltaPOP can only detect a more than 20% decrease in estimated blood volume in children, then their usefulness would be similar to that of central venous pressure or clinical signs such as oliguria, tachycardia, or hypotension. We strongly feel that clinicians definitely need earlier indicators of hypovolaemia. The main point of our study is that in standardized conditions, dynamic parameters of fluid responsiveness based on arterial pressure and on plethysmographic waveform analysis fail to predict fluid responsiveness in children. However, respiratory variation in stroke volume (assessed using respiratory variations in the peak aortic flow velocity obtained with transthoracic echocardiography) is a strong predictor of fluid responsiveness in this setting. If the concepts of haemodynamic optimization based on these variables can be applied to the paediatric population, we believe that variables derived from stroke volume variation analysis would be more appropriate than pulse pressure or plethysmographic waveform variations. Recently, data obtained with PVI in mechanically ventilated children undergoing cardiac surgery found surprisingly good results regarding the ability of PVI to predict fluid responsiveness in this very challenging setting.9Renner J Broch O Gruenewald M et al.Non-invasive prediction of fluid responsiveness in infants using pleth variability index.Anaesthesia. 2011; 66: 582-589Crossref PubMed Scopus (84) Google Scholar Most patients are neonates, some with very complicated physiology, where cardiopulmonary interactions are extremely specific and may not be reflective of preload dependence. This clearly emphasizes that when it comes to the accuracy of dynamic predictors of fluid responsiveness in children, the only thing that we know is that we know nothing. Consequently, as suggested by Stricker and colleagues, further studies are required in this specific and challenging setting. M.C. is a consultant for Masimo Corp. and Edwards Lifesciences. Predicting fluid responsiveness in children: are the studied indicators of value in the setting of loss and replacement?British Journal of AnaesthesiaVol. 107Issue 5PreviewEditor'We read with interest the recent article which aimed to validate, in a paediatric population, various dynamic variables derived from invasive and non-invasive monitors that are of demonstrated utility in adult patients.1 Interestingly, none of the dynamic variables derived from the arterial and plethysmographic waveforms were shown to reliably predict fluid responsiveness in children. Full-Text PDF Open Archive