Drs. Bahlmann and Hahn mention the existence of some published studies supporting a restrictive approach to perioperative IV fluid therapy, but do not mention others (aside from the RELIEF [Restrictive Versus Liberal Fluid Therapy in Major Abdominal Surgery] trial1 ) that identified possible harms or at least no measurable benefit.2–4 The RELIEF trial clearly identified an increased risk of acute kidney injury when a more restrictive zero-balance approach was used.
We agree with Drs. Bahlmann and Hahn that any unnecessary preoperative fasting should be avoided, and that clinicians should encourage unrestricted intake of fluids until 2 h before elective surgery as a standard of care. This was one of our recommendations.5 Although unnecessarily lengthy preoperative fasting times will create a state of relative dehydration, it is quite usual for most people to not drink between the late evening hours and morning (8 to 10 h period of fasting), so this duration is very unlikely to induce dehydration. More importantly, the RELIEF trial investigators analyzed and reported their results for acute kidney injury according to fasting times and the adverse effect of the restrictive zero-balance approach remained. That is, the risk of acute kidney injury occurred in those with short, intermediate, and longer fasting times (P value for interaction equals 0.47; see fig. S8 in the supplementary material of Myles et al.1 ). A similarly consistent finding was observed in those who did or did not receive bowel preparation (P value for interaction equals 0.55).
Recent guidelines from others had recommended a zero-balance approach to perioperative IV fluid therapy.6–8 This implies that fluid balance should be zero at the end of surgery and over the ensuing 24 h. This is what was tested in the RELIEF trial and the results not only failed to identify any meaningful reduction in complications or hospital length of stay, but there was a higher incidence of acute kidney injury and surgical site infections. It is for this reason that we recommended a moderately liberal IV fluid strategy for major surgery. That is what the evidence is telling us.
The RELIEF (Restrictive Versus Liberal Fluid Therapy in Major Abdominal Surgery) trial was supported by grants from the Australian National Health and Medical Research Council (NHMRC, ID1043755, Canberra, Australia); the Australian and New Zealand College of Anaesthetists (Melbourne, Australia); Monash University (Melbourne, Australia); the Health Research Council of New Zealand (ID 14/222), and the UK National Institute of Health Research. Paul Myles is supported by an Australian NHMRC Practitioner Fellowship.
Dr. Myles was the principal investigator of the RELIEF (Restrictive Versus Liberal Fluid Therapy in Major Abdominal Surgery) trial. Dr. Miller declares no competing interests.