- The infants will be assessed, as per routine clinical practice, for clinical signs indicating infants at risk of poor perfusion, and will be recruited if they develop haemodynamic insufficiency defined as: either two or more of: (i) Mean blood pressure (MBP) < gestational age (GA)-1 mmHg (invasive/non-invasive, two readings 15 min apart); (ii) SVC flow < 51 ml/kg/min; (iii) capillary refill time (CRT) > 4 sec; (iv) Lactate > 4 mmol/l (v) Base excess <-9 mmol/l or: MBP < GA -5 mmHg (invasive/non-invasive, two readings 15 min apart)