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Relationship between Carotid Blood Flow, Cardiac Output and Blood Pressure in Extremely Preterm Infants

Presented at the Neonatal Society 2013 Autumn Meeting.

Pereira SS, Sinha AK, Shah DK, Kempley ST

Neonatal Intensive Care Unit, The Royal London Hospital, Barts Health NHS Trust, UK

Background: Cardiovascular problems, including low flow and hypotension are common in extremely preterm infants. Low cerebral blood flow is associated with poor long-term outcome (1). Common carotid artery flow (CCAF) provides a reproducible non-invasive measure of blood flow to the brain, but there are no studies of CCAF in extremely preterm infants. We wanted to investigate the relationship between CCAF, cardiac output and blood pressure, in a group of babies being studied in a randomised trial of blood pressure intervention levels.

Methods: We studied 16 infants born <29 weeks gestation. Right common carotid artery (RCCA) blood flow and left ventricular output (LVO) using Doppler ultrasound was measured on day 1 and 3 of life. Right common blood flow was calculated by using time averaged mean velocity and RCCA diameter. LVO was measured using velocity time integral and diameter across the aortic valve. Mean arterial blood pressure was measured at the time of recording the carotid blood flow. Non-parametric statistics were used for analysis (SPSS v21). Research ethics committee approval was granted (Reference 12/LO/1553) and written parental consent obtained.

Results: Median (range) gestation and birth weight was 25.8 (23.4-28.9) weeks and 735 (515-1470) grams respectively. 16 (100%) babies were ventilated on day 1 compared to 12 (75%) babies ventilated on day 3. PDA was present in 14 (87%) babies on day 1 and 11 (68%) babies on day 3. The following parameters were measured on day 1 and day 3. Median (range) RCCA flow of 11.7 (8.5-12.4) ml/kg/min on day 1 and 15.1 (11.8-19.5) ml/kg/min on day 3 (p = 0.017). Median LVO (range) of 163 (140-189) ml/kg/min on day 1 and 215 (163-254) ml/kg/min on day 3 (p = 0.005). Median BP (range) of 33 (21-59) mmHg on day 1 and 34 (27-64) mmHg on day 3 (p =0.088). There were no statistically significant correlations between RCCA flow and blood pressure, LVO, CO2 or serum lactate in this cohort on day 1 or day 3 of life.

Conclusion: RCCA blood flow increased between day 1 and day 3 of life in extremely preterm infants, which reflects, improved cardiac output. We found no significant relationship between RCCA flow, blood pressure and LVO in our babies. Values in this cohort were lower than previously reported in more stable and more preterm infants, particularly on day 1.

Corresponding author: sujithpereira@nhs.net

1. Hunt R. Low superior vena cava flow and neurodevelopment at 3 years in very preterm infants. J Pediatr 2004

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