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Abstract
SUMMARY
Respiratory distress syndrome (RDS), formerly known as hyaline membrane disease, is a common problem in preterm infants. This disorder is caused primarily by deficiency of pulmonary surfactant in an immature lung. RDS is a major cause of morbidity and mortality in preterm infants (Saker &Martin, 2014).
The introduction of modern mechanical ventilation in neonatal medicine in the 1960s was followed shortly by its use in premature infants with hyaline membrane disease (John and Carlo, 2003).
Progress in neonatal medicine has resulted in decrease of neonatal mortality, particularly in preterm infants. However, there are concerns about the adverse neurodevelopmental outcome of the survivors (Fawke, 2007).
This work was designed to evaluate the influence of different modes of ventilation (either non-invasive or invasive) on cerebral blood flow measurements of the intra- and extra-cranial arteries, using Doppler Ultrasonography, in preterm infants ventilated for neonatal respiratory distress syndrome.
This Case-Control study was conducted from January 2013 till January 2015 in the neonatal intensive care unit (NICU) of the Maternity Hospital of Ain Shams University, Cairo, Egypt.
The study was conducted on total 80 preterm neonates.60 preterm neonates were included of gestational age ranging from 28-36 weeks with respiratory distress syndrome evident clinically and radiologically required respiratory support according to Down’s score , Preterms with major congenital anomalies, intrauterine growth restriction (IUGR),hypoxic-ischemic encephalopathy (HIE), intraventricular hemorrhage (IVH) grade 3 or 4, major cardiac anomalies, Carotid occlusion were excluded.60 preterm neonates with respiratory distress syndrome requiring respiratory support were included. The other 20 preterm neonates were in stable general condition, with no respiratory distress, not requiring respiratory support, of matched gestational, postnatal age and sex was included as a control group.
According to the need of respiratory support and the mode of ventilation which was selected by the treating neonatologist, neonates were divided into four groups for a minimum duration of 24 hours with postnatal ages from 1 to 13 days: Group 1 included 20 preterm neonates with respiratory distress syndrome requiring Synchronized intermittent mandatory ventilation (SIMV), with mean gestational age 32 ± 3 weeks, mean postnatal age 7 ± 3 days, neonatal gender M/F:16/4,mode of delivery: caesarean section (CS)/ normal vaginal delivery (NVD):19/1. Group 2 included 20 preterm neonates with respiratory distress syndrome requiring high-frequency ventilation (HFV), with mean gestational age 32 ± 2 weeks, mean postnatal age 8 ± 4 days, gender M/F:13/7,all of them were delivered by CS. Group 3 included 20 preterm neonates with respiratory distress syndrome requiring non-invasive nasal continuous positive airway pressure (N-CPAP) with mean gestational age 32± 3 weeks, mean postnatal age 6 ± 4 days, gender M/F:11/9, mode of delivery CS/NVD:17/3.Group 4 included 20 preterm neonates with stable general condition, with no respiratory distress, not requiring respiratory support, of matched sex, gestational and post natal age as a control group with mean gestational age 33 ± 2 weeks, postnatal age 5 ± 4 days, gender M/F:11/9, mode of delivery CS/NVD:19/1.
Doppler ultrasound was done measuring resistive index (RI), pulsatility index (PI) and timed average velocity (TAmax) for the anterior cerebral artery (ACA), middle cerebral artery (MCA), and internal carotid artery (ICA) after being on mechanical ventilation for a minimum duration of 24 hours with postnatal ages from 1 to 13 days.
ACA Doppler indices showed no significant differences among the 4 groups.
RI of both MCA and ICA together with ICA PI were significantly increased HFV group in comparison to the control group. Moreover, ICA RI was higher in SIMV group compared to control group. However all RI values were within the physiological range. Other parameters showed no difference among the 4 groups.
MCA and ICA RI were significantly higher in patients with high CRP.
There was positive correlation between ICA TAmax, MBP and hemoglobin.
There was statistical significant increase in frequency of using dopamine and dobutamine in SIMV and HFV groups than the CPAP and control groups.
Hemoglobin was significantly lower in SIMV and HFV groups than other 2 groups. Hematocrit was significantly lower in HFV than CPAP group, platelet count was significantly lower in SIMV and HFV groups than control group. CRP and BUN were significantly higher in HFV group than other 3 groups.
Spo2 was significantly lower in SIMV group than control group. There was no statistical difference among the 4 groups regarding MABP , UOP,PH value, PaCO2 and HCO3 Apgar score at 5 minutes was significantly lower among SIMV, HFV and CPAP groups compared to control group.
By the end of our study, we concluded that if cerebrovascular hemodynamic autoregulation and mean arterial blood pressure were adequately maintained, ventilation alone as HFV and SIMV could influence brain circulation. However, the use of CPAP didn’t significantly affect cerebral blood flow indices neither in intra- nor extra-cranial vessels among our studied neonates.
Wide spread use of HFV among Preterm neonates whenever indicated is recommended, since its effect on cerebral blood flow indices has been within the physiological range. Cerebral blood flow and its autoregulation seem to fluctuate in preterm infants, so it would be useful to assess cerebrovascular autoregulation by using Doppler ultrasound and introducing of other devices as near infrared spectroscopy (NIRS).