Intervention levels for the support of blood pressure in extremely preterm infants
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Background The true relationship between different cardiovascular variables are complex. A varied practice exists in the cardiovascular management of extremely preterm infants, including intervention levels for blood pressure (BP). Adverse outcomes may be secondary to low BP, anti-hypotensive treatment, or both. Aim To test the hypothesis that alterations in BP and cardiac output (CO) have an effect on cerebral blood flow (CBF), that these cardiovascular measures effect electroencephalographic (EEG) continuity and that different BP intervention levels will result in different rates of inotrope usage and achieved levels of BP in infants born <29 weeks gestation using patients recruited to a clinical pilot study. Methods Infants had measurements of CO and CBF using ultrasound, EEG recording and BP profiles downloaded for the first postnatal week. Infants were randomised to different levels of mean arterial BP at which they received cardiovascular support: Active(<30mmHg), Moderate(< Gestational age mmHg) or Permissive(signs of poor perfusion or <19mmHg). Once this BP threshold was breached, all infants were managed using the same treatment guideline. Cranial ultrasound scans were reviewed blind to study allocation. The relationship between physiological measurements was explored. The validity and reliability of CBF measurements were examined using flow phantom models. Results Sixty infants were recruited, had detailed measurements performed, and randomly assigned to one of three arms. CO was not related to CBF or BP. Inotrope usage, and invasively measured BP on day 1 were highest in the Active and lowest in the Permissive arm. There were no differences in haemodynamic or EEG parameters, or non-cerebral clinical complications. EEG continuity and CBF were directly related to BP. The validity and reliability of CBF was acceptable. Composite rates of grade 2–4 intraventricular haemorrhage, periventricular leucomalacia or parenchymal cysts were significantly different on post-hoc analysis between the three arms (Active 0/19, Moderate 6/20, Permissive 2/21;p=0.014). Conclusion Alterations in BP and CO did not affect CBF. Different BP intervention levels resulted in different rates of inotrope usage and levels of achieved BP. Although EEG continuity was not different between the three arms, this study found an increasing mean arterial BP was associated with increasing cerebral electrical activity and higher EEG continuity.
AuthorsPEREIRA, SUJITH; Queen Mary University of London
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