Does visual turbidity correlate with serum triglyceride levels in babies on total parenteral nutrition?

Intravenous lipid is commonly used as part of total parenteral nutrition (TPN) in premature babies. The gold standard of measuring lipid tolerance involves measuring serum triglyceride levels. Many hospitals in Asia do not have this facility and rely on visual turbidity to titrate the rate of lipid infusion. The aim of this study was to determine if visual turbidity correlates with serum triglyceride levels.

Twenty-seven samples were taken from 8 babies on intravenous (IV) lipid infusion for the analysis of serum triglyceride levels and visual turbidity (assessed by 2 senior neonatologists independently). Serum turbidity was classified either as clear or turbid. Lipid intolerance was defined as triglyceride levels greater than 200 mg/dL (2.25 mmol/L).

Both neonatologists similarly classified 20 out of 27 specimens. Serum triglyceride levels for clear samples (n = 10) were significantly lower than those for turbid samples (n = 10) (P <0.01). The clear specimens all had normal serum triglyceride levels (mean, 1.16 mmol/L; range, 0.43 to 1.96). Not all turbid specimens had unacceptable serum triglyceride levels (mean, 2.37 mmol/L; range, 1.37 to 5.75). In the remaining 7 specimens, there was a difference in opinion regarding serum turbidity. The triglyceride levels for these 7 samples were all normal (mean, 1.17 mmol/L; range, 0.66 to 1.72).

Serum turbidity may be used as a screening tool in assessing lipid tolerance in babies on TPN as all clear samples had acceptable serum triglyceride level if we set the maximum cutoff at 2.25 mmol/L. Patients with turbid samples should ideally have their serum triglyceride taken to confirm lipid intolerance before altering their lipid infusion rate as they may have acceptable triglyceride levels.