Indexing haemodynamic variables in young children

BACKGROUND: Haemodynamic studies in children are rare and most studies have included few subjects in the youngest age group. Haemodynamic variables need to be indexed to establish a reference of normality that is valid in all populations. The traditional way to index haemodynamic variables with body surface area (BSA) is complicated in young children due to its non‐linear relationship with body weight (BW). We examined several haemodynamic variables in children by indexing them with BSA and BW. METHODS: A single‐centre, observational cohort study comparing non‐indexed and indexed haemodynamic variables in children undergoing heart surgery (divided into three weight groups: 1‐5 kg, >5‐10 kg and >10‐15 kg). RESULTS: A total of 68 children were included in this study, mean age 11.1 months ± 11.1 month (range 0 to 43 months). All haemodynamic variables, cardiac output (CO), stroke volume (SV), total end‐diastolic volume (TEDV), central blood volume (CBV) and active circulation volume (ACV), increased with weight without indexing (P < .05). Indexing variables with BW produced a more linear relationship for all haemodynamic variables between weight groups than BSA. The mean BSA‐indexed haemodynamic values were CI(BSA) 3.5 ± 1.1 L/min/m(2) and SVI(BSA) 27.3 ± 8.9 ml/min/m(2). The mean BW‐indexed haemodynamic values were CI(BW) 180 ± 50 ml/min/kg and SVI(BW) 1.34 ± 0.38 ml/kg. Blood volume variables indexed with BW were TEDV(BW) 12.0 ± 2.8 ml/kg, CBV(BW) 21.3 ± 6.6 ml/kg and ACV(BW) 70.3 ± 15.2 ml/kg. CONCLUSIONS: Indexing haemodynamic variables with BW produces a more appropriate body size‐independent scale in young children than BSA. SUMMARY STATEMENT: In this study, we studied indexing of haemodynamic variables and estimation of blood volumes in young children undergoing corrective heart surgery using an indicator dilution technology.