We thank Daniel Chappell and Michael Jacob for their interest in and their appreciative comments1 on the English version of the German S3-guidelines on intravascular volume therapy in adults, published in the European Journal of Anaesthesiology.2 We do agree that the guidelines do, to some extent, show the absence rather than the presence of valid scientific evidence – and obviously, the lack of evidence gives rise to a welcomed debate.
Chappell and Jacob criticise the guidelines’ recommendation 4a-4 that the use of colloids in pregnant or breastfeeding women should be restricted to emergencies. They point out that colloids help to prevent maternal hypotension and thus several associated unwanted effects on both the mother and the unborn child. Maternal hypotension during spinal anaesthesia is usually treated by administration of fluids and/or vasopressors – the latter possibly being inferior, for example, because vasopressors may reduce placental oxygen supply.
The guidelines do not advocate the use of vasopressors instead of fluids, but rather they favour crystalloids over colloids to prevent maternal hypotension. The guidelines’ recommendations are for methodological reasons strictly focussed on the treatment of (isotonic) hypovolaemia in adults – not hypotension or hypoperfusion.2 Thus, the guidelines cannot comment on the usefulness of vasoactive or any other class of drugs, either isolated or in comparison with fluid therapy. This separation may appear artificial, but it is because of the strict S3-methodology.
The references included in the guidelines’ evidence base did not demonstrate a consistent patient-relevant benefit of colloids vs. crystalloids, especially not concerning APGAR scores or umbilical vein blood gases/acid–base status. The guidelines’ authors appraised some inconclusive superiority of colloids over crystalloids in prevention of maternal hypotension of minor importance compared with – to our knowledge – the unknown risks for the unborn and breastfed suckling that could result from the use of colloids.
The disagreement of Chappell and Jacob is substantiated by some very recent references – predominantly published after 14 June 2013, the date of the latest literature research included in the guidelines, which is reported in our manuscript.2 This time course resulted from the comprehensive literature work that preceded the development of the formulation of the recommendations and the formal procedure for discussing and consenting these recommendations first by the guidelines group and second by the boards of all participating scientific medical societies. To include recent evidence, a revised version of the guidelines will be produced in 2017. Nevertheless, as these recent studies contribute to the current knowledge and could influence today's clinical work, we would like to take the opportunity to comment on them.
In the randomized, double-blind, multicentre CAESAR trial,3 Mercier et al. observed a higher incidence of (symptomatic) hypotension in pregnant women preloaded with Ringer's lactate compared with hydroxyethyl starch (HES). Despite this increased incidence, vasopressors were used equally in the two groups. APGAR scores or umbilical blood acid–base values did not differ between the groups. The increased incidence of hypotension may partially result from the comparably sensitive threshold for hypotension (<95% of baseline systolic arterial pressure) compared with other studies (<80% or even <70% baseline systolic arterial pressure). Furthermore, Mercier et al.3 demonstrated in six patients receiving HES, that less than 1% of maternal HES was transferred via the placenta. To our knowledge, this is the first direct evidence that HES is not (or negligibly) transferred via the (healthy?) placenta.
The narrative review of Teoh et al.4 is unquestionably a valuable and educative statement. However, from a scientific viewpoint, narrative reviews do not have a high level of evidence because of their unsystematic literature search and lack of formal quality assessment. Data from narrative reviews were not included in the evidence base of the guidelines.2
Ripollés et al.5 demonstrated that colloids were more effective than crystalloids to prevent hypotension during spinal anaesthesia. The only patient-relevant outcome they reported was maternal nausea and vomiting which did not differ. Thus, this study does not apply to the issue discussed here.
Taken together, we are glad about the comments made by Chappell and Jacob, because they show the needs and give the opportunity to further clarify whether colloids can be useful to prevent hypotension during spinal anaesthesia. However, in pregnant or breastfeeding women, the risk–benefit ratio for the child cannot currently be validly appraised, because data on the harm to the unborn or breastfed suckling are too rare.
Acknowledgements related to this article
Assistance with the reply: none.
Financial support and sponsorship: none.
Conflicts of interest: GM has chaired the development of the German S3-Guidelines on fluid therapy, is a Board Member of the German Society of Anaesthesiology and Intensive Care Medicine, is a Board Member of the German Interdisciplinary Association of Critical Care and Emergency Medicine, and is currently receiving research grants and honoraria for consultancy or lectures from B. Braun Melsungen AG, Adrenomed AG, CLS Behring, Koninklijke Philips N.V., Serumwerke Bernburg AG, Pfizer Inc., Thermo Fisher Scientific, Biotest AG and Novartis AG.
1. Chappell D, Jacob M. Volume therapy in obstetrics. 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. Mercier FJ, Diemunsch P, Ducloy-Bouthors AS, et al. 6% hydroxyethyl starch (130/0.4) vs Ringer's lactate preloading before spinal anaesthesia for Caesarean delivery: the randomized, double-blind, multicentre CAESAR trial. Br J Anaesth
4. Teoh WH, Westphal M, Kampmeier TG. Update on volume therapy in obstetrics. Best Pract Res Clin Anaesthesiol
5. Ripolles J, Espinosa A, Casans R, et al. Colloids versus crystalloids in objective-guided fluid therapy, systematic review and meta-analysis. Too early or too late to draw conclusions. Braz J Anesthesiol