A systematic review of the definitions and prevalence of feeding intolerance in preterm infants

Background & aims Feeding intolerance (FI) is a common phenomenon experienced in preterm infants in neonatal intensive care units, as well as being a focus of many research studies into feeding methods, particularly in relation to comorbidities. There is no widely accepted definition of FI. This systematic review aimed to explore the range of definitions used for FI and provide an estimate of the prevalence amongst preterm infants. Methods Searches were completed on MEDLINE (includes the Cochrane library), Embase, PsycInfo, CINAHL, NHS Evidence and Web of Science. Inclusion criteria; preterm infants in neonatal units, a clear definition of FI, >10 patients and be available in English language. Case reports were excluded. Results One hundred studies were included. Definitions of FI were inconsistent. Studies were grouped according to definition used into: Group A − measuring gastric residual volume (GRV) only; group B − GRV and abdominal distension (AD); group C − GRV, AD and gastrointestinal symptoms (GI) which included any of vomiting, bilious vomiting and blood in stool; group D- GRV and GI; group E − AD and GI; group F − GI only and group G − any other elements used. Meta-analysis demonstrated that prevalence of FI between groups varied from 15 to 30% with an overall prevalence of 27% (95% confidence interval 23–31%). Group A had the highest prevalence. Review of time to full enteral feed was performed (37 studies) which demonstrated a range of 11.3–18.3 days depending on which FI definition used. Discussion Definitions of FI in research are inconsistent, a similar finding to that seen in studies in both paediatric and adult critical care populations. The difficulty of defining FI in the preterm population is the concern regarding necrotising enterocolitis, with some studies using an overlap in their definitions, despite differing pathophysiology and management. Due to the heterogeneity of data obtained in this review regarding definitions used, further robust research is required in order to conclude which elements which should be used to define FI in this population. PROSPERO number CRD42019155596. Registered November 2019.