Tidal volume monitoring during initial resuscitation of extremely prematurely born infants.

Background Airway obstruction can occur during facemask (FM) resuscitation of preterm infants at birth. Intubation bypasses any upper airway obstruction. Thus, it would be expected that the occurrence of low expiratory tidal volumes (VTes) would be less in infants resuscitated via an endotracheal tube (ETT) rather than via an FM. Our aim was to test this hypothesis. Methods Analysis was undertaken of respiratory function monitoring traces made during initial resuscitation in the delivery suite to determine the peak inflating pressure (PIP), positive end expiratory pressure (PEEP), the VTe and maximum exhaled carbon dioxide (ETCO2) levels and the number of inflations with a low VTe (less than 2.2 mL/kg). Results Eighteen infants were resuscitated via an ETT and 11 via an FM, all born at less than 29 weeks of gestation. Similar inflation pressures were used in both groups (17.2 vs. 18.8 cmH2O, P = 0.67). The proportion of infants with a low median VTe (P = 0.6) and the proportion of inflations with a low VTe were similar in the groups (P = 0.10), as was the lung compliance (P = 0.67). Infants with the lowest VTe had the stiffest lungs (P < 0.001). Conclusion Respiratory function monitoring during initial resuscitation can objectively identify infants who may require escalation of inflation pressures.

Prematurely born infants' response to resuscitation via an endotracheal tube or a face mask.

BACKGROUND: Prematurely born infants may be resuscitated in the labour suite via a face mask or an endotracheal tube. AIMS: To assess prematurely born infants' initial responses to resuscitation delivered via an endotracheal tube or a face mask, to determine if the first five inflations via an endotracheal tube produced expired tidal volumes greater than 4.4ml/kg (twice the anatomical dead space) and whether the outcome of initial resuscitation via an endotracheal tube or via a face mask differed according to the first active inflation (the infant's inspiratory effort coinciding with an inflation). STUDY DESIGN: Prospective observational study. SUBJECTS: Thirty-five infants (median gestational age 25, range 23-27weeks) requiring resuscitation via an endotracheal tube (n=20) or a face mask (n=15) were studied. OUTCOME MEASURES: Inflation pressures, inflation times, expiratory tidal volumes, end tidal carbon dioxide (ETCO2) and leak were recorded. RESULTS: Before the first active inflation, only 27% of infants receiving resuscitation via an endotracheal tube had expiratory volumes greater than 4.4ml/kg. During, both endotracheal and face mask initial resuscitations, during the first active inflation the expired tidal volumes (7.7ml/kg, 5.2ml/kg) and ETCO2 levels (4.8kPa, 3.2kPa) were significantly higher than during the inflations before the first active inflation (2.8ml/kg, 1.6ml/kg; 0.36kPa, 0.2kPa respectively) (all p<0.001). CONCLUSIONS: Initial resuscitation via an endotracheal tube using currently recommended pressures, rarely produced adequate tidal volumes. Resuscitation via an endotracheal tube or a face mask was most effective when the infant's inspiratory effort coincided with an inflation.

Evaluation of respiratory function monitoring at the resuscitation of prematurely born infants.

UNLABELLED: Our aim was to determine whether neonatal trainees found respiratory function monitoring (RFM) helpful during the resuscitation of prematurely born infants, what decisions they made on the basis of RFM and whether those decisions were evidence based. Fifty one trainees completed an electronic questionnaire. Eighty-three percent found the tidal volume display useful, 59 % altered the inflation pressure based on the tidal volume: 52 % considered 5 ml/kg adequate; 33 % 4 ml/kg; 13 % 6 ml/kg; and 2 % 7 ml/kg, despite no evidence on which to decide was the optimum tidal volume. If there was no detectable expired carbon dioxide (CO2), 30 trainees said they would reintubate, yet the absence of expired CO2 can indicate inadequate vasodilation of the pulmonary circulation rather than inappropriate placement of the endotracheal tube. If there was no chest wall expansion, but expired CO2, a third of junior trainees would reintubate which is inappropriate. If the oxygen saturation (SaO2) was <85 % at 1 min, no senior trainee, but 50 % of junior trainees would increase the inspired oxygen. The majority of healthy babies have an SaO2 > 85 % by 1 min. CONCLUSIONS: The usefulness of respiratory function monitoring for trainees during neonatal resuscitation is often not evidence based.

End tidal carbon dioxide levels during the resuscitation of prematurely born infants.

BACKGROUND: Successful resuscitation of prematurely born infants is dependent on achieving adequate alveolar ventilation and vasodilation of the pulmonary vascular bed. Elevation of end-tidal carbon dioxide (ETCO(2)) levels may indicate pulmonary vasodilation. AIMS: This research aims to study the temporal changes in ETCO(2) levels and the infant's respiratory efforts during face mask resuscitation in the labour suite, and to determine if the infant's first inspiratory effort was associated with a rise in the ETCO(2) levels, suggesting pulmonary vasodilation had occurred. STUDY DESIGN: This study is an observational one. SUBJECTS: The subjects of the study are forty infants with a median gestational age of 30 weeks (range 23-34). OUTCOME MEASURES: Inflation pressures, expiratory tidal volumes and ETCO(2) levels were measured. RESULTS: The median expiratory tidal volume of inflations prior to the onset of the infant's respiratory efforts (passive inflations) was lower than that of the inflation associated with the first inspiratory effort (active inflation) (1.8 (range 0.1-7.3) versus 6.3 ml/kg (range 1.9-18.4), p<0.001), as were the median ETCO(2) levels (0.3 (range 0.1-2.1) versus 3.4 kPa (0.4-11.5), p<0.001). The median expiratory tidal volume (4.5 ml/kg (range 0.5-18.3)) and ETCO(2) level (2.2 kPa (range 0.3-9.3)) of the two passive inflations following the first active inflation were also higher than the median expiratory tidal volume and ETCO(2) levels of the previous passive inflations (p<0.001, p<0.0001 respectively). CONCLUSION: These results suggest that during face mask resuscitation, improved carbon dioxide elimination, likely due to pulmonary vasodilation, occurred with the onset of the infant's respiratory efforts.

The first five inflations during resuscitation of prematurely born infants.

OBJECTIVE: To study the first five inflations during the resuscitation of prematurely born infants and whether the infant's inspiratory efforts influenced the expired tidal volume. DESIGN: Prospective observational study. SETTING: Two tertiary perinatal centres. PATIENTS: Thirty infants, median gestational age 30 (23-34) weeks. INTERVENTIONS: The first five inflations delivered via a face mask and t-piece device were examined using respiratory function monitoring. MAIN OUTCOME MEASURES: Inflation pressures, inflation times and expiratory volumes were recorded and comparison made of inflations during which the infant made an inspiratory effort (active inflation) or did not (passive inflation). RESULTS: Overall, the median expired tidal volume was 2.5 (0-19.8) ml/kg and was lower for passive (median 2.1 ml/kg, range 0-19.8 ml/kg) compared with active (median 5.6 ml/kg, range 1.2-12.2 ml/kg) inflations (ratio of geometric means 1.85, 95% CI 1.18 to 28%) (p=0.007). Overall, the median face mask leak was 54.5% and was lower for active (34.5%) compared with passive (60.7%) inflations (mean difference in % leak: 12.4%, 95% CI 0.9 to 24%) (p=0.0354). There was a significant positive correlation between the expiratory volumes and the inflation pressures (R2 between subjects 0.19, p=0.04) and a negative correlation between the expiratory tidal volumes and the face mask leaks (R2 between subjects=0.051, p<0.001), but there was no significant correlation between the inflation times and the expiratory tidal volumes. CONCLUSION: The expired tidal volume, inflation pressures and times during the first five inflations during resuscitation were variable. The expired tidal volumes were significantly greater if the infant inspired during the inflation.

Cerebral and splanchnic hemodynamics after duct ligation in very low birth weight infants.

OBJECTIVE: To describe mesenteric and cerebral blood flow velocities after surgical patent ductus arteriosus (PDA) closure in premature infants. STUDY DESIGN: We measured middle cerebral artery (MCA), celiac artery (CA), and superior mesenteric artery (SMA) Doppler ultrasound scanning blood flow velocity (BFV) preoperatively, 3 and 24 hours after ligation. RESULTS: We studied 32 infants, with a mean (+/- SD) birthweight of 762 +/- 170 g and gestational age of 25.6 +/- 1.4 weeks at a mean age of 34 +/- 13 days. Significant changes in end-diastolic (EDV), average velocity (AV), and vascular resistance were measured in all 3 vessels by 3 hours. AV increased significantly in the CA and SMA within 3 hours; however, no significant increase in MCA AV was found until 24 hours after surgery. CONCLUSION: PDA ligation significantly changes BFV in the MCA, CA, and SMA. In the MCA vascular tone is acutely modulated, with no change in AV at 3 hours. In the CA and SMA, AV increases acutely after ligation. These different patterns of change in BFV suggest region-specific adaptation to surgical PDA closure.

Maternal nutrient restriction reduces carotid artery constriction without increasing nitric oxide synthesis in the late gestation rat fetus.

Chronic reduction in substrate delivery to the fetus may induce redistribution of fetal cardiac output to maintain nutrient delivery to vital organs, including the brain. Reduced vasoconstriction, in conjunction with increased local synthesis of nitric oxide may contribute to "brain sparing." The authors hypothesized that maternal undernutrition would reduce vasoconstrictor responses in fetal carotid arteries due to increased nitric oxide. Timed pregnant Sprague-Dawley rats were randomized on day 0 of pregnancy to control (C) or nutrient restricted (NR) diet. Dams were killed on day 20 of pregnancy. Fetal carotid artery responses were assessed using a pressurized myograph system. Fetal body weight was reduced by NR diet. In NR fetuses, liver, lung, kidney, and heart weights were lower, whereas proportional brain weight was greater. Carotid artery constriction to endothelin-1 was similar in both groups; however, phenylephrine-induced constriction was decreased in NR arteries. Arteries from control fetuses constricted in response to increasing concentrations of L-NAME, whereas arteries from NR did not. There was also no effect of L-NAME on constriction to phenylephrine in arteries from NR fetuses. Our study indicates that the reduced carotid artery vasoconstriction to phenylephrine in NR fetuses, which is consistent with the maintenance of fetal brain blood flow, was not mediated by enhanced nitric oxide. Reduced phenylephrine but not endothelin-1-induced constriction suggests specific effects on adrenergic carotid artery function, which may implicate this pathway in the vascular adaptation to fetal undernutrition.

Differential effects of maternal hypoxia or nutrient restriction on carotid and femoral vascular function in neonatal rats.

In response to reduced oxygen or nutrient supply, the fetus may redistribute cardiac output to conserve brain and heart growth, at the expense of the peripheral tissues; however, it is not known whether alterations in vascular function are maintained after birth or whether reduced fetal oxygen versus nutrient supply produces distinct effects. Using a pressure myograph, we examined isolated carotid and femoral artery responses to phenylephrine and endothelin-1 in neonatal rats, after either reduced maternal oxygen or global nutrient restriction during late gestation. Timed-pregnant Sprague-Dawley rats were randomly assigned to control (n = 10), hypoxia (12% O2, n = 9), or nutrient restriction (NR, 40% of control diet, n = 7) protocol and treated from day 15-21 of pregnancy. Pups were collected 3-12 h after birth. Neonatal weights (P < 0.001) and relative liver weights (P < 0.001) were lower in hypoxia and nutrient restriction treatments compared with control, while relative heart weights were greater in the hypoxia than in the control or nutrient restriction groups (P < 0.01). Constriction to phenylephrine was reduced in carotid arteries from the hypoxia and nutrient restriction groups compared with control (P < 0.001), while the femoral artery response was greater in hypoxia-treated neonates compared with control or nutrient-restricted neonates (P < 0.01). Only the hypoxia reduced carotid responses to endothelin-1, while no differences were observed in the endothelin-1 responses in femoral arteries. Maternal hypoxia and maternal nutrient restriction produced distinct effects on heart growth and neonatal vascular function, suggesting that regional changes in cardiovascular function after poor fetal growth are dependent on the nature of the insult in utero.

The harlequin color change and association with prostaglandin E1.

The harlequin color change is an unusual cutaneous phenomenon observed in newborn infants as transient, benign episodes of a sharply demarcated erythema on half of the infant, with simultaneous contralateral blanching. In this report, two newborns with congenital heart anomalies demonstrated the harlequin color change, one whose skin findings showed a course related to the dose of systemic prostaglandin E1, suggesting a possible association. The benign, self-limited nature of the color change mandates that prostaglandin E1 not be discontinued for this reason. The entity is likely more common than the paucity of reports in the world literature suggests, and all physicians should recognize its graphic appearance to avoid unnecessary exposure to agents in an effort to treat it.

Cardiopulmonary resuscitation and epinephrine infusion in extremely low birth weight infants in the neonatal intensive care unit.

BACKGROUND: Survival of extremely low birth weight (ELBW) infants has improved significantly; however, the aggressiveness of treatment in these infants remains controversial. Critical appraisal of the benefits of cardiopulmonary resuscitation (CPR) and intravenous epinephrine infusion (IV EPI) has not been studied in this population. OBJECTIVE: To determine if either CPR or continuous IV EPI in NICU is of benefit for surviving in a selected population of infants weighing 1.0 mcg/kg/hour intravenously died. CONCLUSIONS: In view of the poor survival after either CPR or high-dose IV EPI in infants

Myogenic reactivity is enhanced in rat radial uterine arteries in a model of maternal undernutrition.

OBJECTIVES: The purpose of this study was to determine if maternal undernutrition during pregnancy altered myogenic tone in small radial uterine arteries. STUDY DESIGN: Myogenic tone of radial uterine arteries was studied from late pregnant rats (day 20) that were fed either ad libitum or globally restricted diet (moderately severe dietary restriction) throughout pregnancy. RESULTS: Myogenic tone was enhanced in the radial uterine arteries from the diet-restricted compared with the ad libitum group. Nitric oxide synthase inhibition enhanced myogenic tone in the arteries from the ad libitum group only. Prostaglandin H synthase inhibition had no effect on myogenic tone in either group. CONCLUSION: Diet restriction during pregnancy enhances myogenic tone in the radial uterine arteries partly as a result of impairment of the nitric oxide synthase pathway. Enhanced myogenic tone in turn may reduce uteroplacental blood flow and, thus, contribute to reduced birth weight, and lead to effects of fetal programming in utero that can have long-term consequences into adulthood.