Is a UK multicentre trial of intravenous maintenance fluid volumes in critically ill children feasible?

Dear Editor,
Paediatric practice across Europe and the UK uses the Holliday-Segar (HS) formula (Morice et al., 2022) to calculate the volume of intravenous maintenance fluid therapy (IVMFT) required. This formula (Holliday & Segar, 1957) was devised in 1957, but increasing evidence shows that resultant volumes are too high for acutely and critically ill children (Barhight et al., 2021, Black et al., 2021, Anton-Martin et al., 2020). As a result, paediatric intensive care units (PICUs) in the UK and Europe restrict IVMFT to varying degrees (Morice et al., 2022). We conducted a mixed method study to assess whether a randomised trial in UK PICUs of different IVMFT volumes is feasible. This three-phase study consisted of an online cross-sectional survey of PICUs (one response per unit), a focus group with two parents and a former PICU patient and an online consensus webinar with 18 participants from 15 different UK PICUs, all conducted between January and April 2023. University and society ethical approval was obtained (Reference ETH2223-0018REF 3/12/22). Twenty-one of 25 units (84 %) completed the survey. Fluid restriction varied from 50 % to 80 % of the HS formula for intubated and ventilated patients but was more liberalised for children who were extubated. After cardiac surgery, IVMFT was even more restricted and more varied. Items included in fluid balance also varied by unit. The acceptable upper limit for general children reported by 50 % units was 80 % and the lower acceptable limit was 60 %. For cardiac children acceptable lower limit, (46 % units) was 40 % (Graph 1). Future trial outcomes were then rated 1–5 for importance. The highest rated measures were (1) length of invasive mechanical ventilation (mean score 4.5/5), (2) length of all respiratory support (4.2/5), (3) acute kidney injury (4/5), and (4) organ support free days (4/5). Overall, the parents and patients found a trial of IVMFT acceptable and felt they would consent to this. However, the language used ‘around restriction’ one found concerning, giving the impression this was restricting something they should receive. An important omission from the clinician identified outcomes was that of patient thirst. At the consensus meeting most (69 %) professionals thought cardiac surgical children should be included in a future trial. However, most (69 %) felt that fluid intake alone was not sufficient and active fluid removal would also be necessary. All 16 clinicians thought a trial was feasible if including all fluids and active fluid removal. Just over half (62.5 %) said it should be part of a platform trial within the specialty. A trial of IVMFT restriction is feasible if combined with a fluid removal strategy. However, more research is required to gain a better understanding of actual practice surrounding fluid restriction, fluid removal and the included items in the fluid balance. The optimal trial design should include both intake and fluid removal interventions. Finally, the terminology used with parent facing information will need careful preparation and co-designing with parents and families.