Letters to the Editor: Letter to the Editor
To the Editor
I read with interest the debate on the role of goal-directed fluid therapy (GDFT) in the context of enhanced recovery after surgery (ERAS) protocols.1,2 A meta-analysis on this topic has been published in the time between acceptance and publication of these articles in Anesthesia & Analgesia.3 The pooled analysis suggested that ERAS pathways and improved perioperative care of surgical patients have lessened the impact of GDFT on postoperative outcomes. This raised the question of whether GDFT was beneficial in an ERAS setting. However, there was huge variation between clinical trials in the method of deploying GDFT. Notably, esophageal Doppler monitoring was used in 9 of 10 (90%) ERAS pathway trials but in only 3 of 13 (23%) trials conducted in a traditional care setting.
The discussion in this journal highlighted the different technologies used to measure stroke volume and cardiac output and how there is poor agreement between monitors. However, this factor appears to be more important than previously thought. A recent study found that different devices varied widely in their accuracy and sensitivity to detect a statistically significant change in stroke volume.4 The LiDCOrapid (LiDCO, London, UK) was able to detect this change after a 2.5% blood loss, the USCOM 1A (USCOM, Sydney, NSW, Australia) at 7.5%, and the CardioQ esophageal Doppler (Deltex Medical, Chichester, West Sussex, UK) and Vigileo FloTrac at (Edwards Lifesciences, Irvine) 12.5%. Mean stroke volume at baseline also varied from 90.8 to 138.9 mL depending on the device used. This was despite being deployed in young, healthy volunteers without the physiologic derangements of surgery, which may compound device-related inaccuracies.
To date, systematic reviews of perioperative GDFT have all failed to consider the actual method of delivery as a distinct category of analysis. As such, studies using a multitude of different devices have been included in pooled analysis. It is clear that GDFT needs to be considered in relation to the method of delivery and devices are not interchangeable. In addition, it is important to remember that national guidelines in the United Kingdom recommend esophageal Doppler monitoring and not GDFT in general. It would be misleading, as has been done, to challenge this using evidence from non-esophageal Doppler monitoring trials. Device variability is only part of the high degree of heterogeneity, which exists between study groups and within studies. The added nuance that these monitors may not all be equally able to accurately and reliably track changes in stroke volume makes the controversies surrounding perioperative GDFT even harder to untangle. Large-scale randomized controlled trials that tackle these issues would be better placed to clarify uncertainties than systematic reviews that continue to combine highly heterogeneous trials with multiple confounding factors.
Chengyuan Zhang, BSc, MBBSDepartment of Anaesthesia, Critical Care and Pain MedicineUniversity of EdinburghRoyal Infirmary of EdinburghEdinburgh, UKc.firstname.lastname@example.org
1. Cannesson M, Gan TJ. PRO: perioperative goal-directed fluid therapy is an essential element of an enhanced recovery protocol. Anesth Analg. 2016;122:12581260.
2. Joshi GP, Kehlet H. CON: perioperative goal-directed fluid therapy is an essential element of an enhanced recovery protocol? Anesth Analg. 2016;122:12611263.
3. Rollins KE, Lobo DN. Intraoperative goal-directed fluid therapy in elective major abdominal surgery: a meta-analysis of randomized controlled trials. Ann Surg. 2016;263:465476.
4. O’Loughlin E, Ward M, Crossley A, Hughes R, Bremner AP, Corcoran T. Evaluation of the utility of the Vigileo FloTrac(™), LiDCO(™), USCOM and CardioQ(™) to detect hypovolaemia in conscious volunteers: a proof of concept study. Anaesthesia. 2015;70:142149.