Abstract
Background: Phosphate is the main intracellular anion essential for numerous biological processes. Symptoms of hypophosphataemia are non-specific, yet potentially life-threatening. This systematic review process was initiated to gain a global insight into hypophosphataemia, associated morbidity and treatments. Methods: A systematic review was conducted (PROSPERO CRD42020163191). Nine clinically relevant questions were generated, seven for adult and two for paediatric critically ill patients, and prevalence of hypophosphataemia was assessed in both of these groups. We identified trials through systematic searches of Medline, EMBASE, Scopus, Cochrane Central Register of Controlled Trials, CINAHL, and Web of Science. Quality assessment was performed using the Cochrane risk of bias tool for randomized controlled trials and the Newcastle-Ottawa Scale for observational studies.Results: For all research questions, we identified 2727 titles in total, assessed 399 full texts, and retained 82 full texts for evidence synthesis, with 20 of them identified for several research questions. Only 3 randomized controlled trials were identified with two of them published only in abstract form, as well as 28 prospective and 31 retrospective studies, and 20 case reports. Relevant risk of bias regarding selection and comparability was identified for most of the studies. No meta-analysis could be performed. The prevalence of hypophosphataemia varied substantially in critically ill adults and children, but no study assessed consecutive admissions to intensive care.In both critically ill adults and children, several studies report that hypophosphataemia is associated with worse outcome (prolonged length of stay and the need for respiratory support, and higher mortality). However, there was insufficient evidence regarding the optimal threshold upon which hypophosphataemia becomes critical and requires treatment. We found no studies regarding the optimal frequency of phosphate measurements, and regarding the time window to correct hypophosphataemia. In adults, nutrient restriction on top of phosphate repletion in patients with refeeding syndrome may improve survival, although evidence is weak. Conclusion: Evidence on the definition, outcome and treatment of clinically relevant hypophosphataemia in critically ill adults and children is scarce and does not allow answering clinically relevant questions. High quality clinical research is crucial for the development of respective guidelines.
The Structure of Research Questions in Randomized Controlled Trials in the Rehabilitation Field
