Left ventricle output and mean arterial blood pressure in preterm infants during the 1st day of life

The objective was to assess the contribution of left ventricular output (LV O) in determining low mean arterial blood pressure (MABP) in preterm infant s admitted to the neonatal intensive care unit. Doppler echocardiography wa s prospectively performed on a cohort of 17 consecutive infants with low MA BP (<30 mmHg) and on 17 consecutive control subjects (range: 600-1520 g; 27 -30.7 weeks gestation). The median haematocrit was 42.5% in the low MABP gr oup versus 49.4% in the control group (P < 0.01). The index of resistance t o the LVO (RILV = MABP:LVO ratio) was lower in the low MABP group (98 vs 15 6 mmHg . l(-1) . kg(-1) min(-1); P < 0.05). An analysis of the low MABP gro up regarding LVO revealed that a subgroup of four infants had LVO <10th per centile (185 ml . kg(-1) . min(-1)) with a high RILV (>90th percentile: 226 mmHg . l(-1) . kg(-1) . min(-1)) for three of the infants. The remaining 1 3 infants had LVO >10th percentile and a shortening fraction >25th percenti le. In this subgroup, a high proportion of infants (9/ 13 vs 2/17, P < 0.01 ) had low RILV (<10th percentile: 96 mmHg . l(-1) . kg(-1) . min(-1)) and t he incidence of haemodynamically significant patent ductus arteriosus was h igher than in the control group (10/13 vs 4/17, P < 0.01). Conclusion Left ventricular output, index of resistance to left ventricular output and patent ductus arteriosus status are important to consider in ev aluating mean arterial blood pressure during early postnatal life in preter m infants. Low mean arterial blood pressure is frequently associated with n ormal or high left ventricular output, low index of resistance to left vent ricular output and significant patent ductus arteriosus.