Early microvascular changes in the preterm neonate: a comparative study of the human and guinea pig

Dysfunction of the transition from fetal to neonatal circulatory systems may be a major contributor to poor outcome following preterm birth. Evidence exists in the human for both a period of low flow between 5 and 11 h and a later period of increased flow, suggesting a hypoperfusion-reperfusion cycle over the first 24 h following birth. Little is known about the regulation of peripheral blood flow during this time. The aim of this study was to conduct a comparative study between the human and guinea pig to characterize peripheral microvascular behavior during circulatory transition. Very preterm (≤28 weeks GA), preterm (29-36 weeks GA), and term (≥37 weeks GA) human neonates underwent laser Doppler analysis of skin microvascular blood flow at 6 and 24 h from birth. Guinea pig neonates were delivered prematurely (62 day GA) or at term (68-71 day GA) and laser Doppler analysis of skin microvascular blood flow was assessed every 2 h from birth. In human preterm neonates, there is a period of high microvascular flow at 24 h after birth. No period of low flow was observed at 6 h. In preterm animals, microvascular flow increased after birth, reaching a peak at 10 h postnatal age. Blood flow then steadily decreased, returning to delivery levels by 24 h. Preterm birth was associated with higher baseline microvascular flow throughout the study period in both human and guinea pig neonates. The findings do not support a hypoperfusion-reperfusion cycle in the microcirculation during circulatory transition. The guinea pig model of preterm birth will allow further investigation of the mechanisms underlying microvascular function and dysfunction during the initial extrauterine period

Transitional hemodynamics in preterm infants with a respiratory management strategy directed at avoidance of mechanical ventilation

Background: Early respiratory management of very low birth weight infants has changed over recent years to a practice of early use of CPAP with early selective surfactant administration, and decreased use of mechanical ventilation. One strategy is to use the combination of surfactant and prompt extubation to nasal continuous positive airway pressure (INtubate, SURfactant, Extubate, or INSURE). The aim of this study is to describe blood flow and ductal flow in a prospective cohort during the transitional period when this respiratory management strategy is used. Methods: Inborn infants < 29. week gestation underwent INSURE within 30. min of birth using 200. mg/kg Curosurf. Blood pressure and blood flow parameters (RVO, LVO, SVC flow, ductus arteriosus) were measured at 6, 24 and 72. h of age and information on morbidity was collected. Results: Sixty-eight infants with a median (range) weight of 940 (450-1380) g were studied. 13 (19%) patients needed mechanical ventilation within 72. h of life (INSURE failure). Blood flows and blood pressure were within reported ranges. Eleven (16%) patients had a blood pressure < gestational age and 9 (13%) patients had low blood flow. Conclusion: These data show a low prevalence of low blood pressure and low blood flow in the first 3. days after INSURE as compared to cohorts where mechanical ventilation was preferred during transition. We speculate that altered ventilation strategies have helped decrease the incidence of low blood flow and low blood pressure

Speckle tracking echocardiography in very preterm infants: feasibility and reference values

Background: Speckle tracking echocardiography (STE) applies computer software analysis on images generated by conventional ultrasound to define and follow a cluster of speckles from frame to frame and calculates parameters of motion (velocity, displacement) and deformation (strain, strain rate). We explored STE of the left ventricle in stable very preterm infants. Methods: Apical 4 chamber clips (4CH) and short axis clips (SAX) at the level of the papillary muscle were analyzed using TomTec software with manual tracing of cardiac borders. The software automatically segmented the ventricle into 6 equidistant segments and provided segmental and global analysis of deformation parameters. Tracking accuracy was scored visually. Results: Seventy-four clips from 51 infants with a median gestational age of 28 weeks were analyzed. Feasibility of 4CH was 95.5% for longitudinal and 96.2% for radial parameters. The reliability of longitudinal and circumferential deformation parameters was good, but radial parameters were less reliable. 4CH mean (SD) global peak systolic longitudinal and radial strain (%) and strain rate (s⁻¹) were - 18.7(2.6), - 1.73(0.28), 23.6(9.1) and 1.94(0.65), and SAX circumferential and radial strain and strain rate were - 19.5(3.7), - 1.97(0.46), 32.1(14.4) and 2.37(0.80). Conclusion: STE is feasible in preterm infants. Optimal image acquisition is paramount. Longitudinal parameters in 4CH and circumferential in SAX were most robust

Regional (spinal, epidural, caudal) versus general anaesthesia in preterm infants undergoing inguinal herniorrhaphy in early infancy

Review question: In preterm infants undergoing inguinal hernia repair, does the use of regional anaesthesia compared to general anaesthesia reduce postoperative complications including apnoea, bradycardia and the use of assisted ventilation? Background: babies born preterm (before 37 weeks) often have serious health problems and sometimes need surgery. Inguinal hernia (IH) (where the intestine protrudes through the abdominal wall) is the commonest condition where surgery is needed. General anaesthetics for surgery can disrupt breathing and cause other complications in preterm babies. Regional anaesthetics including spinal block (injection) might avoid complications such as pauses in breathing in the first 24 hours after surgery. Whether this improves outcomes for preterm babies having surgery is unclear because no trials have looked at the effects of anaesthetics on brain function in older children. Study characteristics: seven small trials comparing spinal with general anaesthesia in the repair of IH were identified. Results: there was no statistically significant difference in the risk of postoperative apnoea/bradycardia, postoperative oxygen desaturations, the use of postoperative analgesics, or postoperative respiratory support between infants receiving spinal or general anaesthesia. When infants who had received preoperative sedatives were excluded, the meta-analysis supported a reduction in the risk of postoperative apnoea in the spinal anaesthesia group. Infants with no history of apnoea in the preoperative period and receiving spinal anaesthesia (including a subset of infants who received sedatives) had a reduced risk of postoperative apnoea. Infants receiving spinal rather than general anaesthesia had a statistically significant increased risk of anaesthetic agent failure. Infants randomised to receive spinal anaesthesia had an increased risk of anaesthetic placement failure of borderline statistical significance. Conclusions: there is some evidence to suggest that spinal anaesthesia without the addition of sedative drugs to assist in keeping the baby still and provide additional pain relief during the procedure may be safer than general anaesthesia for a former preterm baby having surgery for inguinal hernia. A recently completed but as yet unpublished large multicentre trial comparing general anaesthesia or awake spinal anaesthesia may help give more precise answers to this question

Early microvascular changes in the preterm neonate: a comparative study of the human and guinea pig.

Dysfunction of the transition from fetal to neonatal circulatory systems may be a major contributor to poor outcome following preterm birth. Evidence exists in the human for both a period of low flow between 5 and 11 h and a later period of increased flow, suggesting a hypoperfusion-reperfusion cycle over the first 24 h following birth. Little is known about the regulation of peripheral blood flow during this time. The aim of this study was to conduct a comparative study between the human and guinea pig to characterize peripheral microvascular behavior during circulatory transition. Very preterm (≤28 weeks GA), preterm (29-36 weeks GA), and term (≥37 weeks GA) human neonates underwent laser Doppler analysis of skin microvascular blood flow at 6 and 24 h from birth. Guinea pig neonates were delivered prematurely (62 day GA) or at term (68-71 day GA) and laser Doppler analysis of skin microvascular blood flow was assessed every 2 h from birth. In human preterm neonates, there is a period of high microvascular flow at 24 h after birth. No period of low flow was observed at 6 h. In preterm animals, microvascular flow increased after birth, reaching a peak at 10 h postnatal age. Blood flow then steadily decreased, returning to delivery levels by 24 h. Preterm birth was associated with higher baseline microvascular flow throughout the study period in both human and guinea pig neonates. The findings do not support a hypoperfusion-reperfusion cycle in the microcirculation during circulatory transition. The guinea pig model of preterm birth will allow further investigation of the mechanisms underlying microvascular function and dysfunction during the initial extrauterine period