Examining safety and efficacy of a fixed concentration heparin dosing strategy for anticoagulation in neonatal extracorporeal membrane oxygenation.

OBJECTIVES: The paediatric intensive care unit changed heparin infusion dosing from a variable weight-based concentration to a fixed concentration strategy, when smart pump-based drug library was introduced. This change meant significantly lower rates of infusion were needed for the same dose of heparin in the neonatal population. We performed a safety and efficacy assessment of this change. METHODS: We performed a retrospective single-centre evaluation based on data from respiratory VA-extracorporeal membrane oxygenation (ECMO) patients weighing ≤5 kg, pre and post the change to fixed strength heparin infusion. Efficacy was analysed by distribution of activated clotting times (ACT) and heparin dose requirements between the groups. Safety was analysed using thrombotic and haemorrhagic event rates. Continuous variables were reported as median, interquartile ranges, and non-parametric tests were used. Generalised estimating equations (GEE) were used to analyse associations of heparin dosing strategy with ACT and heparin dose requirements in the first 24 h of ECMO. Incidence rate ratios of circuit related thrombotic and haemorrhagic events between groups were analysed using Poisson regression with offset for run hours. RESULTS: 33 infants (20 variable weight-based, 13 fixed concentration) were analysed. Distribution of ACT ranges and heparin dose requirements were similar between the two groups during the ECMO run and this was confirmed by GEE. Incidence rate ratios of thrombotic (fixed v weight-based) (1.9 [0.5-8], p = .37), and haemorrhagic events (0.9 [0.1-4.9], p = .95) did not show statistically significant differences. CONCLUSIONS: Fixed concentration dosing of heparin was at least equally effective and safe compared to a weight-based dosing.

Measurement of Respiratory Chain Enzyme Activity in Human Renal Biopsy Specimens.

Background: Mitochondrial disorders can present as kidney disease in children and be difficult to diagnose. Measurement of mitochondrial function in kidney tissue may help diagnosis. This study was to assess the feasibility of obtaining renal samples and analysing them for respiratory chain enzyme activity. Methods: The subjects were children undergoing a routine diagnostic renal biopsy, in whom a clinical condition of renal inflammation, scarring and primary metabolic disorder was unlikely. A fresh sample of kidney was snap frozen and later assayed for the activities of respiratory chain enzyme complexes I, II/III, and IV using spectrophotometric enzyme assay, and expressed as a ratio of citrate synthase activity. Results: The range of respiratory chain enzyme activity for complex I was 0.161 to 0.866 (mean 0.404, SD 0.2), for complex II/III was 0.021 to 0.318 (mean 0.177, SD 0.095) and for complex IV was 0.001 to 0.025 (mean 0.015, SD 0.006). There were correlations between the different activities but not between them and the age of the children or a measure of the amount of chronic damage in the kidneys. Conclusion: It is feasible to measure respiratory chain enzyme activity in routine renal biopsy specimens.