Editor—We read with great interest this feasibility study by Parke and colleagues1 to rationalize fluid in patients after cardiac surgery. It is very refreshing to come across a well-designed study that proposes a conservative fluid regimen in the cardiac intensive care population. Working in a major London cardiac centre, we are also keen to adopt such regimens that may improve patient outcome; however, we do have some points for discussion and consideration regarding the study. We found differences in the baseline characteristics between the two groups (e.g. gender), which were not analysed and reported but may well have contributed to the differing outcomes.
We were also interested to see that subject allocation was stratified by the presence or absence, on admission to the intensive care unit, of a pulmonary artery catheter. However, we could not ascertain from the results how many subjects in each group received pulmonary artery catheters. It may be interesting to analyse whether pulmonary artery catheters led to conservative fluid therapy compared with other forms of monitoring.
We acknowledge the discussion of limitations for using stroke volume variation in this context. However, we have concerns regarding the validity of stroke volume variation as a measure once patients are de-sedated; stroke volume variation is validated only in paralysed patients who are ventilated with tidal volumes of 6–8 ml kg−1. Is this a reliable measure in patients once they resume spontaneous ventilation?
Most importantly, we observed a marked difference in the usual care of fluid administration in comparison to our institution. Our median volume of fluid admisitration over 24 h after cardiac surgery during the last 12 month period is 2830 ml (interquartile range 1890–4170 ml), compared with 5080 ml (interquartile range 3930–7320 ml) within 24 h after surgery in the usual care arm of this study. This may suggest that this algorithm would have a much larger impact on their study population than it would do on ours.
We congratulate the authors for presenting a well-designed feasibility study and demonstrating that a conservative fluid approach in clinical practice is both possible and safe. We look forward to the upcoming multicentre Phase IIb trial of this intervention looking at important patient outcomes, such as intensive care unit length of stay and ventilation hours.
Declaration of interest
None declared.
Reference
- 1.Parke RL, McGuinness SP, Gilder E, McCarthy LW, Cowdrey K-AL. A randomised feasibility study to assess a novel strategy to rationalise fluid in patients after cardiac surgery. Br J Anaesth 2015; 115: 45–52 [DOI] [PubMed] [Google Scholar]