We thank Siegler et al. for their comments on the Guideline ‘Intravascular Volume Therapy in Adults’, published on behalf of the German Association of Scientific Medical Societies by an inter-disciplinary and inter-professional group of authors.1,2 We are glad about the ongoing scientific debate that was and is triggered by this work.
The guideline is strictly focussed on diagnosis and treatment of hypovolaemia. It is based on 248 scientific publications that had to pass a prospectively defined and consented process of literature research, screening for inclusion/exclusion criteria, quality assessment and data extraction before being included into the guideline's evidence base as demanded by the principles of the German Association of Scientific Medical Societies on scientific guideline development.3 About 18 000 articles were screened for inclusion or exclusion. Whenever available, high-grade evidence like systematic reviews, meta-analyses and randomised controlled trials were favoured over low-grade evidence. Narrative reviews, case series or experts opinions and so on were prospectively excluded from the evidence base.
Independent delegates of 14 participating scientific medical societies, further proven experts on methodology and additional clinical experts finally developed six statements and 50 recommendations based on this evidence. During the consensus conferences, the ballots were carried out anonymously with one vote per medical society. Each single statement and 48 of the 50 recommendations obtained agreement by more than 75% of the delegates. The board of each participating society consented to the guideline as a whole. However, the board of one single society disagreed with four specified recommendations. Finally, the board of the German Association of Scientific Medical Societies consented to the content and process of this evidence-based guideline.
The methodologically compelling, strictly evidence-based development of the guideline resulted in a high degree of consensus obtained among both the delegates and the societies’ boards. It also resulted in a guideline that is strictly focussed on diagnosis and treatment of hypovolaemia. In addition, finally it created a sound and robust guideline that both results from and contributes to evidence-based medicine.
Basically, Siegler et al. criticise two strong recommendations (grade of recommendation A, both), namely not to use central venous pressure for diagnosis of hypovolaemia and to use a monitoring method that allows the estimation of volume responsiveness for fluid management, with flow-based or dynamic preload variables being superior to static variables in this regard. The authors are concerned that clinicians may abandon central venous pressure measurement to comply with the guideline's recommendations. They emphasise that central venous pressure measurement is a valuable puzzle stone in haemodynamic monitoring. They argue that there is a general lack of consensus among clinicians regarding central venous pressure measurements.
Again, the validity of the guidelines’ recommendations is restricted to the diagnosis and treatment of hypovolaemia, as they do not apply to other clinical situations. Regarding hypovolaemia and speaking methodologically, the concerns of Siegler et al. are experts’ opinions and thus inferior to the group of systematic reviews, meta-analyses and randomised controlled trials that the guideline is based upon. Furthermore, this opinion is in contrast to the consented appraisal of both delegates and boards of 14 national medical societies.
Finally, we would like to respond to the author's arguments in detail. The authors make several strong statements: first, central venous pressure is ‘… interwoven in this interaction (of cardiac efficiency, blood volume and vascular compliance) and … it becomes clear that alterations of cardiac and venous return function can result in both high or low central venous pressure without any changes in blood volume’; second, ‘isolated central venous pressure measurement should not be used to determine intravascular volume state’; third, ‘in three recently published randomised controlled early goal-directed therapy trials (ARISE, ProMISe, ProCESS) … central venous pressure measurement proved to be neither harmful nor beneficial…’; fourth, ‘…central venous pressure represents an easily accessible, safe, cost-effective and feasible monitoring option…’; and fifth, ‘…central venous pressure values should always be interpreted in view of clinical signs …, laboratory parameters … and ... other monitoring devices reflecting volume state’.
Considering the evidence base of the Guideline of the German Association of Scientific Medical Societies on Intravascular Volume Therapy in Adults, we agree that central venous pressure values and their changes are not reliably associated with changes in blood volumes; isolated central venous pressure measurements should not be used to determine intravascular volume state (this is essentially the guideline's recommendations 1 to 3 which is discussed by Siegler et al.), central venous pressure is easily accessible, cost-effective and feasible; and finally, central venous pressure values should be interpreted in view of information reflecting volume status, as volume status interferes with central venous pressure.
We contradict the notion that the three cited trials proved that central venous pressure measurement is neither harmful nor beneficial. No hypothesis on central venous pressure measurement was tested by these trials, thus they cannot prove anything in this regard. We disagree that central venous pressure is (abundantly) well tolerated. Its risks (arterial puncture, nerve damage, pneumothorax, misinterpretation of values e.g. as an estimate of volume status etc.) have to be weighed against its benefits. We would also like to emphasise that central venous pressure values lack any verifiable use when it comes to the estimation of volume status.
Authors of an evidence-based guideline have to systemically evaluate the evidence and give recommendations on a limited issue. In our view, the authors of these Guidelines successfully achieved this goal. Clearly, the recommendations do not apply to any conceivable clinical setting in which central venous pressure measurement may or may not be helpful. Within the guideline's scope, any clinician can decide whether and when she/he acts in accordance with its recommendations. Obviously, the recommendations break with some established traditions. That may be irritating; however, that is the nature of evidence-based medicine. Any physician who believes in the value of central venous pressure measurements for diagnosis of hypovolaemia or as a guidance for volume therapy is asked to publish respective data.
Acknowledgements related to this article
Assistance with the letter: none.
Financial support and sponsorship: none.
Conflicts of interest: GM has chaired the development of the S3-Guideline discussed in the correspondence. He has received honoraria for consultancy and research grants from B. Braun Melsungen AG (currently) and Edwards Life Sciences (past). For lectures, he received honoraria from B. Braun Melsungen AG (currently) and from Edwards Life Sciences (past).
1. Siegler BH, Rex S, Rossaint R, et al. Is the central venous pressure an obsolescent model or a valuable puzzle stone in haemodynamic monitoring? Eur J Anaesthesiol
2. Marx G, Schindler AW, Mosch C, et al. Intravascular volume therapy in adults: guidelines from the Association of the Scientific Medical Societies in Germany. Eur J Anaesthesiol
3. German Association of the Scientific Medical Societies (AWMF) – Standing Guidelines Commission. AWMF guidance manual and rules for guideline development, 1st edition 2012. English version. Available at: http://www.awmf.org/leitlinien/awmf-regelwerk.html
. [Accessed on 01.07.2014].