Comparison of hemodynamic effects of chest compression delivered via machine or human in asphyxiated piglets.

BACKGROUND: High-quality chest compressions (CC) are an important factor of neonatal resuscitation. Mechanical CC devices may provide superior CC delivery and improve resuscitation outcomes. We aimed to compare the hemodynamic effects of CC delivered by machine and human using a neonatal piglet model. METHODS: Twelve asphyxiated piglets were randomized to receive CC during resuscitation using an automated mechanical CC device ("machine") or the two-thumb encircling technique ("human"). CC was superimposed with sustained inflations. RESULTS: Twelve newborn piglets (age 0-3 days, weight 2.12 ± 0.17 kg) were included in the study. Machine-delivered CC resulted in an increase in stroke volume, and minimum and maximum rate of left ventricle pressure change (dp/dtmin and dp/dtmax) compared to human-delivered CC. CONCLUSIONS: During machine-delivered CC, stroke volume and left ventricular contractility were significantly improved. Mechanical CC devices may provide improved cardiopulmonary resuscitation outcomes in neonatal cardiac arrest induced by asphyxia. IMPACT: Machine chest compression leads to changes in hemodynamic parameters during resuscitation of asphyxiated neonatal piglets, namely greater stroke volume and left ventricular contractility, compared with standard two-thumb compression technique. Mechanical chest compression devices may provide improved cardiopulmonary resuscitation outcomes in neonatal and pediatric asphyxia-induced cardiac arrest.

Chest compressions superimposed with sustained inflations during cardiopulmonary resuscitation in asphyxiated pediatric piglets.

BACKGROUND: Pediatric resuscitation guidelines recommend continuous chest compression with asynchronized ventilation (CCaV) during cardiopulmonary resuscitation. We recently described that providing a constant high distending pressure, or sustained inflation (SI) while performing continuous chest compressions (CC = CC + SI) reduces time to return of spontaneous circulation (ROSC) in neonatal and pediatric piglets with asphyxia-induced cardiac arrest. METHODS: To determine if CC + SI compared to CCaV will improve frequency of achieving ROSC and reduce time to ROSC in asphyxiated pediatric piglets. Twenty-eight pediatric piglets (21-24 days old) were anesthetized and asphyxiated by clamping the endotracheal tube. Piglets were randomized to CC + SI or CCaV for resuscitation (n = 14/group). Heart rate, arterial blood pressure, carotid blood flow, cerebral oxygenation, and respiratory parameters were continuously recorded throughout the experiment. RESULTS: The mean(SD) duration of resuscitation was significantly reduced with CC + SI compared to CCaV with 208(190) vs. 388(258)s, p = 0.045, respectively. The number of piglets achieving ROSC with CC + SI and CCaV were 12/14 vs. 6/14, p = 0.046. Minute ventilation, end-tidal carbon dioxide, ventilation rate, and positive end expiratory pressures were also significantly improved with CC + SI. CONCLUSIONS: CC + SI improves duration of resuscitation and increases number of piglets achieving ROSC secondary to improved minute ventilation. IMPACT: Chest compressions superimposed with sustained inflation resulted in shorter duration of resuscitation Chest compressions superimposed with sustained inflation resulted in higher number of piglets achieving return of spontaneous circulation Further animal studies are needed to examine chest compressions superimposed with sustained inflation.

Comparison of various vasopressin doses to epinephrine during cardiopulmonary resuscitation in asphyxiated neonatal piglets.

BACKGROUND: Current neonatal resuscitation guidelines recommend epinephrine for cardiac arrest. Vasopressin might be an alternative during asphyxial cardiac arrest. We aimed to compare vasopressin and epinephrine on incidence and time to return of spontaneous circulation (ROSC) in asphyxiated newborn piglets. DESIGN/METHODS: Newborn piglets (n = 8/group) were anesthetized, intubated, instrumented, and exposed to 30 min of normocapnic hypoxia, followed by asphyxia and asystolic cardiac arrest. Piglets were randomized to 0.2, 0.4, or 0.8IU/kg vasopressin, or 0.02 mg/kg epinephrine. Hemodynamic parameters were continuously measured. RESULTS: Median (IQR) time to ROSC was 172(103-418)s, 157(100-413)s, 122(93-289)s, and 276(117-480)s for 0.2, 0.4, 0.8IU/kg vasopressin, and 0.02 mg/kg epinephrine groups, respectively (p = 0.59). The number of piglets that achieved ROSC was 6(75%), 6(75%), 7(88%), and 5(63%) for 0.2, 0.4, 0.8IU/kg vasopressin, and 0.02 mg/kg epinephrine, respectively (p = 0.94). The epinephrine group had a 60% (3/5) rate of post-ROSC survival compared to 83% (5/6), 83% (5/6), and 57% (4/7) in the 0.2, 0.4, and 0.8IU/kg vasopressin groups, respectively (p = 0.61). CONCLUSION: Time to and incidence of ROSC were not different between all vasopressin dosages and epinephrine. However, non-significantly lower time to ROSC and higher post-ROSC survival in vasopressin groups warrant further investigation. IMPACT: Time to and incidence of ROSC were not statistically different between all vasopressin dosages and epinephrine. Non-significantly lower time to ROSC and higher post-ROSC survival in vasopressin-treated piglets. Overall poorer hemodynamic recovery following ROSC in epinephrine piglets compared to vasopressin groups. Human neonatal clinical trials examining the efficacy of vasopressin during asphyxial cardiac arrest will begin recruitment soon.

[The evolution of approach in the resuscitation of neonates born with meconium-stained amniotic fluid: a tale of two countries, China and U.S.A., in the past 60 years]. / 羊水胎粪污染新生儿复苏的前世今生：过去60年中美两国的演变史.

Neonates born through meconium-stained amniotic fluid (MSAF) may develop complications including meconium aspiration syndrome, persistent pulmonary hypertension of newborn and death. The approach to the resuscitation of these neonates has significantly evolved for the past few decades. Initially, under direct visualization technique, neonates with MSAF were commonly suctioned below the vocal cords soon after delivery. Since 2015, Neonatal Resuscitation Program (NRP®) of the American Academy of Pediatrics has recommended against "routine" endotracheal suctioning of non-vigorous neonates with MSAF but favored immediate resuscitation with positive pressure ventilation via face-mask bagging. However, the China neonatal resuscitation 2021 guidelines continue to recommend routine endotracheal suctioning of non-vigorous neonates born with MSAF at birth. This review article discusses the differences and the rationales in the approach in the resuscitation of neonates with MSAF between Chinese and American NRP® guidelines over the past 60 years.

Impact of Lockdown Measures during COVID-19 Pandemic on Pregnancy and Preterm Birth.

OBJECTIVE: The objective of this study is to assess the effect of the lockdown measures during the coronavirus disease 2019 (COVID-19) pandemic on pregnancy outcomes of women who were not affected by severe acute respiratory syndrome coronavirus 2 infection. STUDY DESIGN: We used data from the perinatal health program and neonatal databases to conduct a cohort analysis of pregnancy outcomes during the COVID-19 lockdown in the Calgary region, Canada. Rates of preterm birth were compared between the lockdown period (March 16 to June 15, 2020) and the corresponding pre-COVID period of 2015 to 2019. We also compared maternal and neonatal characteristics of preterm infants admitted to neonatal intensive care units (NICUs) in Calgary between the two periods. FINDINGS: A total of 4,357 and 24,160 live births occurred in the lockdown and corresponding pre-COVID period, respectively. There were 366 (84.0 per 1,000 live births) and 2,240 (92.7 per 1,000 live births) preterm births in the lockdown and corresponding pre-COVID period, respectively (p = 0.07). Rates of very preterm and very-low-birth-weight births were lower in the lockdown period compared with the corresponding pre-COVID period (11.0 vs. 15.6 and 9.0 vs. 14.4 per 1,000 live births, p = 0.02 and p = 0.005, respectively). There was no difference in spontaneous stillbirth between the two periods (3.7 vs. 4.1 per 1,000 live birth, p = 0.71). During the lockdown period, the likelihood of multiple births was lower (risk ratio [RR] 0.73, 95% confidence interval [CI]: 0.60-0.88), while gestational hypertension and clinical chorioamnionitis increased (RR 1.24, 95%CI: 1.10-1.40; RR 1.33, 95%CI 1.10-1.61, respectively). CONCLUSION: Observed rates of very preterm and very-low-birth-weight births decreased during the COVID-19 lockdown. Pregnant women who delivered during the lockdown period were diagnosed with gestational hypertension and chorioamnionitis more frequently than mothers in the corresponding pre-COVID period. KEY POINTS: · Lockdown measures to reduce COVID-19 transmission were associated with a lower rate of preterm birth.. · Mental and physical wellbeing of pregnant women were significantly affected by the lockdown measures.. · A comprehensive public health plan to relieve psychosocial stress during pregnancy is required..

Cerebral oxygen saturation and autoregulation during hypotension in extremely preterm infants.

BACKGROUND: The impact of the permissive hypotension approach in clinically well infants on regional cerebral oxygen saturation (rScO2) and autoregulatory capacity (CAR) remains unknown. METHODS: Prospective cohort study of blinded rScO2 measurements within a randomized controlled trial of management of hypotension (HIP trial) in extremely preterm infants. rScO2, mean arterial blood pressure, duration of cerebral hypoxia, and transfer function (TF) gain inversely proportional to CAR, were compared between hypotensive infants randomized to receive dopamine or placebo and between hypotensive and non-hypotensive infants, and related to early intraventricular hemorrhage or death. RESULTS: In 89 potentially eligible HIP trial patients with rScO2 measurements, the duration of cerebral hypoxia was significantly higher in 36 hypotensive compared to 53 non-hypotensive infants. In 29/36 hypotensive infants (mean GA 25 weeks, 69% males) receiving the study drug, no significant difference in rScO2 was observed after dopamine (n = 13) compared to placebo (n = 16). Duration of cerebral hypoxia was associated with early intraventricular hemorrhage or death.  Calculated TF gain (n = 49/89) was significantly higher reflecting decreased CAR in 16 hypotensive compared to 33 non-hypotensive infants. CONCLUSIONS: Dopamine had no effect on rScO2 compared to placebo in hypotensive infants. Hypotension and cerebral hypoxia are associated with early intraventricular hemorrhage or death. IMPACT: Treatment of hypotension with dopamine in extremely preterm infants increases mean arterial blood pressure, but does not improve cerebral oxygenation. Hypotensive extremely preterm infants have increased duration of cerebral hypoxia and reduced cerebral autoregulatory capacity compared to non-hypotensive infants. Duration of cerebral hypoxia and hypotension are associated with early intraventricular hemorrhage or death in extremely preterm infants. Since systematic treatment of hypotension may not be associated with better outcomes, the diagnosis of cerebral hypoxia in hypotensive extremely preterm infants might guide treatment.

Effects of epinephrine on hemodynamic changes during cardiopulmonary resuscitation in a neonatal piglet model.

BackgroundAsphyxia is the most common reason for newborns to fail to make a successful fetal-to-neonatal transition. There is currently a lack of data evaluating hemodynamic effects of epinephrine during neonatal cardiopulmonary resuscitation.MethodsTwenty-four newborn piglets were exposed to asphyxia. Thereafter, positive pressure ventilation was commenced for 30 s, followed by chest compressions (CC). Piglets were randomized into three experimental groups: 3:1 compression:ventilation ratio; CC during sustained inflation (SI) at a rate of 90 CC per minute, or CC during SI at a rate of 120 CC per minute. Epinephrine (0.01 mg/kg per dose) was administered to a maximum of four doses. Hemodynamic parameters were measured throughout the experiment.ResultsAnimals were divided into survivors and nonsurvivors. End-diastolic and developed pressures declined after epinephrine administration in the survivor group. dp/dt min was significantly higher in the survivor group whereas dp/dt max showed no significant differences. Epinephrine had no effect on either heart rate or cardiac output in both groups. Ejection fraction increased after epinephrine with no significant difference between groups.ConclusionEpinephrine did not affect survival rates or return of spontaneous circulation in our postnatal porcine model of neonatal asphyxia.

Review of Routes to Administer Medication During Prolonged Neonatal Resuscitation.

OBJECTIVE: During neonatal cardiopulmonary resuscitation, early establishment of vascular access is crucial. We aimed to review current evidence regarding different routes for the administration of medications during neonatal resuscitation. DATA SOURCES: We reviewed PubMed, EMBASE, and Google Scholar using MeSH terms "catheterization," "umbilical cord," "delivery room," "catecholamine," "resuscitation," "simulation," "newborn," "infant," "intraosseous," "umbilical vein catheter," "access," "intubation," and "endotracheal." STUDY SELECTION: Articles in all languages were included. Initially, we aimed to identify only neonatal studies and limited the search to randomized controlled trials. DATA EXTRACTION: Due to a lack of available studies, studies in children and adults, as well as animal studies and also nonrandomized studies were included. DATA SYNTHESIS: No randomized controlled trials comparing intraosseous access versus peripheral intravascular access versus umbilical venous catheter versus endotracheal tube versus laryngeal mask airway or any combination of these during neonatal resuscitation in the delivery room were identified. Endotracheal tube: endotracheal tube epinephrine administration should be limited to situations were no vascular access can be established. Laryngeal mask airway: animal studies suggest that a higher dose of epinephrine for endotracheal tube and laryngeal mask airway is required compared with IV administration, potentially increasing side effects. Umbilical venous catheter: European resuscitation guidelines propose the placement of a centrally positioned umbilical venous catheter during neonatal cardiopulmonary resuscitation; intraosseous access: case series reported successful and quick intraosseous access placement in newborn infants. Peripheral intravascular access: median time for peripheral intravascular access insertion was 4-5 minutes in previous studies. CONCLUSIONS: Based on animal studies, endotracheal tube administration of medications requires a higher dose than that by peripheral intravascular access or umbilical venous catheter. Epinephrine via laryngeal mask airway is feasible as a noninvasive alternative approach for drug delivery. Intraosseous access should be considered in situations with difficulty in establishing other access. Randomized controlled clinical trials in neonates are required to compare all access possibilities described above.

Oxygen Saturation and Heart Rate Ranges in Very Preterm Infants Requiring Respiratory Support at Birth.

OBJECTIVE: To evaluate the changes in preductal oxygen saturation (SpO2) and heart rate in preterm infants receiving continuous positive airway pressure (CPAP) and/or positive-pressure ventilation (PPV) at birth. STUDY DESIGN: A prospective observational study at birth of infants aged <32 weeks separated into 2 gestational age (GA) groups: 230/7-276/7 weeks (group 1) and 280/7-316/7 weeks (group 2). Infants received delayed cord clamping (DCC) in accordance with institutional protocol. CPAP and/or PPV was applied at the clinical team's discretion. SpO2 and heart rate were recorded every minute for 10 minutes. Preductal SpO2 was targeted according to published nomograms. For heart rate, the goal was to maintain a stable heart rate >100 bpm. RESULTS: The study cohort comprised 96 group 1 infants (mean GA, 26 ± 1 weeks; mean birth weight, 818 ± 208 g) and 173 group 2 infants (mean GA, 30 ± 1 weeks; mean birth weight, 1438 ± 374 g). In general, infants requiring respiratory support reached target values for heart rate and SpO2 more slowly than the published nomograms for spontaneously breathing preterm infants without respiratory support. Infants receiving CPAP reached SpO2 and heart rate targets faster than infants receiving PPV. In group 1, but not group 2 infants, DCC resulted in higher SpO2 and heart rate. CONCLUSION: SpO2 and heart rate do not quickly and reliably reach the values achieved by spontaneously breathing preterm infants not requiring respiratory support.

Postnatal neonatal myocardial adaptation is associated with loss of tolerance to tachycardia: a simultaneous invasive and noninvasive assessment.

Doppler studies at rest suggest left ventricular (LV) diastolic function rapidly improves from the neonate to infant. Whether this translates to its response to hemodynamic challenges is uncertain. We sought to explore the impact of early LV maturation on its ability to tolerate atrial tachycardia. As tachycardia reduces filling time, we hypothesized that the neonatal LV would be less tolerant of atrial tachycardia. Landrace cross piglets of two age groups (1-3 days; NPs; 14-17 days, YPs; n = 7/group) were instrumented for an atrial pacing protocol (from 200 to 300 beats/min) and assessed by invasive monitoring and echocardiography. NPs maintained their LV output and blood pressure, whereas YPs did not. Although negative dP/dt in NPs at baseline was lower than that of YPs (-1,599 ± 83 vs. -2,470 ± 226 mmHg/s, respectively, P = 0.007), with increasing tachycardia negative dP/dt converged between groups and was not different. Both groups had similar preload reduction during tachycardia; however, NPs maintained shortening fraction while YPs decreased (NPs: 35.4 ± 1.4 vs. 31.8 ± 2.2%, P = 0.35; YPs: 31.4 ± 0.8 vs. 22.9 ± 0.8%, P < 0.001). Contractility measures did not differ between groups. Peak LV twist and untwisting rate also did not differ; however, NPs tended to augment LV twist through increased apical rotation and YPs through increasing basal rotation (P = 0.009). The NPs appear more tolerant of atrial tachycardia than the YPs. They have at least similar diastolic performance, enhanced systolic performance, and different LV twist mechanics, which may contribute to improved tachycardia tolerance of NPs.

Cerebral Oxygen Saturation to Guide Oxygen Delivery in Preterm Neonates for the Immediate Transition after Birth: A 2-Center Randomized Controlled Pilot Feasibility Trial.

OBJECTIVE: To assess if monitoring of cerebral regional tissue oxygen saturation (crSO2) using near-infrared spectroscopy (NIRS) to guide respiratory and supplemental oxygen support reduces burden of cerebral hypoxia and hyperoxia in preterm neonates during resuscitation after birth. STUDY DESIGN: Preterm neonates <34(+0) weeks of gestation were included in a prospective randomized controlled pilot feasibility study at 2 tertiary level neonatal intensive care units. In a NIRS-visible group, crSO2 monitoring in addition to pulse oximetry was used to guide respiratory and supplemental oxygen support during the first 15 minutes after birth. In a NIRS-not-visible group, only pulse oximetry was used. The primary outcomes were burden of cerebral hypoxia (<10th percentile) or hyperoxia (>90th percentile) measured in %minutes crSO2 during the first 15 minutes after birth. Secondary outcomes were all cause of mortality and/or cerebral injury and neurologic outcome at term age. Allocation sequence was 1:1 with block-randomization of 30 preterm neonates at each site. RESULTS: In the NIRS-visible group burden of cerebral hypoxia in %minutes, crSO2 was halved, and the relative reduction was 55.4% (95% CI 37.6-73.2%; P = .028). Cerebral hyperoxia was observed in NIRS-visible group in 3 neonates with supplemental oxygen and in NIRS-not-visible group in 2. Cerebral injury rate and neurologic outcome at term age was similar in both groups. Two neonates died in the NIRS-not-visible group and none in the NIRS-visible group. No severe adverse reactions were observed. CONCLUSIONS: Reduction of burden of cerebral hypoxia during immediate transition and resuscitation after birth is feasible by crSO2 monitoring to guide respiratory and supplemental oxygen support. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02017691.

Exhaled Carbon Dioxide and Neonatal Breathing Patterns in Preterm Infants after Birth.

OBJECTIVES: To examine the amount of exhaled carbon dioxide (ECO2) with different breathing patterns in spontaneously breathing preterm infants after birth. STUDY DESIGN: Preterm infants had a facemask attached to a combined carbon dioxide/flow sensor placed over their mouth and nose to record ECO2 and gas flow. A breath-by-breath analysis of the first 5 minutes of the recording was performed. RESULTS: Thirty spontaneously breathing preterm infants, gestational age (mean ± SD) 30 ± 2 weeks and birth weight 1635 ± 499 g were studied. ECO2 from normal breaths and slow expirations was significantly larger than with other breathing patterns (P < .001). ECO2 per breath also increased with gestational age P < .001. The expiratory hold pattern was the most prevalent breathing pattern both during the first minute of recording and overall. Breathing pattern proportions also varied by gestational age. Finally, ECO2 from the fifth minute of recording was significantly greater than that produced during the first 4 minutes of recording (P ≤ .029). CONCLUSIONS: ECO2 varies with different breathing patterns and increases with gestational age and over time. ECO2 may be an indicator of lung aeration and that postnatal ECO2 monitoring may be useful in preterm infants in the delivery room.

Spontaneously Breathing Preterm Infants Change in Tidal Volume to Improve Lung Aeration Immediately after Birth.

OBJECTIVE: To examine the temporal course of lung aeration at birth in preterm infants <33 weeks gestation. STUDY DESIGN: The research team attended deliveries of preterm infants <33 weeks gestation at the Royal Alexandra Hospital. Infants who received only continuous positive airway pressure were eligible for inclusion. A combined carbon dioxide (CO2) and flow-sensor was placed between the mask and the ventilation device. To analyze lung aeration patterns during spontaneous breathing, tidal volume (VT), and exhaled CO2 (ECO2) were recorded for the first 100 breaths. RESULTS: Thirty preterm infants were included with a total of 1512 breaths with mask leak <30%. Mean (SD) gestational age and birth weight was 30 (1) weeks and 1478 (430) g. Initial VT and ECO2 for the first 30 breaths was 5-6 mL/kg and 15-22 mm Hg, respectively. VT and ECO2 increased over the next 20 breaths to 7-8 mL/kg and 25-32 mm Hg, respectively. For the remaining observation period VT decreased to 4-6 mL/kg and ECO2 continued to increase to 35-37 mm Hg. CONCLUSIONS: Preterm infants begin taking deeper breaths approximately 30 breaths after initiating spontaneous breathing to inflate their lungs. Concurrent CO2 removal rises as alveoli are recruited. Lung aeration occurs in 2 phases: initially, large volume breaths with poor alveolar aeration followed by smaller breaths with elimination of CO2 as a consequence of adequate aeration.

Effect of sodium tanshinone IIA sulfonate treatment in a rat model of preeclampsia.

Preeclampsia is a disorder of pregnancy with a significant impact on maternal and fetal health. The complexity of this multifactorial condition has precluded development of effective therapies and, although many potential pathways have been investigated, the etiology still requires clarification. Our group has investigated the scavenger lectin-like oxidized LDL (LOX-1) receptor, which may respond to factors released from the distressed placenta that contribute to the vascular pathologies observed in preeclampsia. Given the known beneficial effects of sodium tanshinone IIA sulfonate (STS; a component of Salvia miltiorrhiza) on vasodilation, reduction of oxidative stress, and lipid profiles, we have investigated its role as a potential treatment strategy. We hypothesized that STS would improve vascular endothelial function and, combined with a reduction in oxidative stress, would improve pregnancy outcomes in a rat model of preeclampsia (reduced uteroplacental perfusion pressure, RUPP). We further hypothesized this may occur via the action of STS on the LOX-1 and/or platelet-activating factor (PAF) receptor axes. The RUPP model increased maternal blood pressure, vascular oxidative stress, and involvement of the vascular PAF receptor. Treatment with STS during pregnancy decreased both oxidative stress and involvement of the PAF receptor; however, it also increased involvement of the LOX-1 receptor, which is in line with the concept that scavenger receptors, such as LOX-1 and PAF, are upregulated in response to ligand binding and/or under pathological conditions. In this model of preeclampsia, however, the vascular actions of STS did not lead to improvements in pregnancy outcome such as fetal biometrics or maternal blood pressure.

Is renal tissue oxygen desaturation during severe hypoxia underestimated? An observational study in term newborn piglets.

The kidney is an organ highly susceptible to injury by regional tissue oxygen desaturation during hypoxic episodes. Transcutaneous monitoring of renal tissue oxygen saturation is therefore of increasing interest. The aim of the present study was to compare renal tissue oxygen saturation measured by near-infrared spectroscopy (NIRS) during acute hypoxia in neonates directly on the kidney and transcutaneously. We hypothesized that transcutaneous renal tissue oxygen saturation measurements would be influenced by superficial tissue. Five term newborn piglets were anesthetized, instrumented and exposed to normocapnic hypoxia at an inspired oxygen concentration of 0.14. Regional tissue oxygen saturation (rSO2) was simultaneously measured for comparison with the sensor of NIRS (Invos 5100, Somanetics Corp., Troy, MI, USA) applied directly on the left kidney (renaldirect rSO2) and on the skin of right flank above the right kidney (renalskin rSO2). Cerebral regional tissue oxygenation (cerebralskin rSO2), arterial oxygen saturation, heart rate (HR) and mean arterial pressure (MAP) were also monitored. NIRS parameters were analyzed in 5 s intervals during first 2 min of hypoxia. Hypoxia was achieved with an arterial oxygen desaturation from median (range) 95.3% (86.8-98.0) to 23.5% (13.0-41.0) after 2 min. HR and MAP did not change significantly during hypoxia. There were pronounced and lower renaldirect rSO2 readings when compared with those of renalskin rSO2 with significant differences from 25 to 55 s after initiation of hypoxia. Changes of cerebralskin rSO2 and renalskin rSO2 were similar. Transcutaneous monitoring of renal tissue oxygen saturation may underestimate acute oxygen desaturation of the kidney during hypoxia in neonates.

Time needed to achieve changes in oxygen concentration at the T-Piece resuscitator during respiratory support in preterm infants in the delivery room.

OBJECTIVE: To measure the time needed to achieve changes in fraction of inspired oxygen concentration (FiO2) from the oxygen blender to the facemask during simulated neonatal resuscitation. METHOD: Two oxygen analyzers were placed at each end of the T-Piece. During simulated ventilation, the duration to achieve the set oxygen concentration at the facemask was measured. This was repeated at different gas flow rates (5 L/min, 8 L/min or 10 L/min) and different FiO2 changes (0.21 to 1.0 to 0.21, with stepwise increases and decreases in 0.05, 0.1 and 0.2 increments). RESULTS: A total of 1134 measurements (378 measurements for each flow) were recorded. Overall, the mean (± SD) time required to achieve FiO2 changes at 5 L/min, 8 L/min and 10 L/min was 36±15 s, 31±14 s and 28±14 s, respectively. CONCLUSION: There was a lag time of approximately 30 s to achieve the FiO2 at the facemask. This delay needs to be considered when making serial adjustments to FiO2 during neonatal resuscitation.

OBJECTIF: Mesurer le temps nécessaire pour modifier les concentrations de la fraction d'oxygène dans l'air inspiré (FiO2) entre le mélangeur d'oxygène et le masque au cours d'une simulation de réanimation néonatale. MÉTHODOLOGIE: Deux analyseurs d'oxygène ont été installés à chaque bout de l'insufflateur néonatal. Pendant la simulation de ventilation, les chercheurs ont mesuré le temps nécessaire pour parvenir à la concentration d'oxygène voulue au masque. Ils ont repris la mesure à divers débits de gaz (5 L/min, 8 L/min ou 10 L/min) et diverses modifications de la FiO2 (0,21 à 1,0 à 0,21, au moyen d'augmentations et de diminutions incrémentielles de 0,05, 0,1 et 0,2). RÉSULTATS: Au total, les chercheurs ont enregistré 1 134 mesures (378 mesures par débit). Dans l'ensemble, le temps moyen (± ÉT) nécessaire pour parvenir à des modifications de la FiO2 de 5 L/min, 8 L/min et 10 L/min était de 36±15 s, 31±14 s et 28±14 s, respectivement. CONCLUSION: Il y avait un décalage d'environ 30 secondes pour parvenir à une FiO2 au masque. Il faut en tenir compte lorsqu'on fait les rajustements sériels de la FiO2 pendant la réanimation néonatale.

Cardiopulmonary resuscitation with chest compressions during sustained inflations: a new technique of neonatal resuscitation that improves recovery and survival in a neonatal porcine model.

BACKGROUND: Guidelines on neonatal resuscitation recommend 90 chest compressions (CCs) and 30 manual inflations (3:1) per minute in newborns. The study aimed to determine whether CC s during sustained inflations (SIs) improves the recovery of asphyxiated newborn piglets in comparison with coordinated 3:1 resuscitation. METHODS AND RESULTS: Term newborn piglets (n=8/group) were anesthetized, intubated, instrumented, and exposed to 45-minute normocapnic hypoxia followed by asphyxia. Piglets were randomly assigned to receive either 3:1 resuscitation (3:1 group) or CCs during SIs (SI group) when the heart rate decreased to 25% of baseline. Piglets randomly assigned to the SI group received SIs with a pressure of 30 cm H2O for 30 s. During the SI, CCs at a rate of 120/min were provided. SI was interrupted after 30 s for 1 s before a further 30-s SI was provided. CCs were continued throughout SIs. CCs and SI were continued until the return of spontaneous circulation. Continuous respiratory parameters, cardiac output, mean systemic and pulmonary artery pressures, and regional blood flows were measured. Mean (standard deviation) time for return of spontaneous circulation was significantly reduced in SI group versus 3:1 group (32 [11] s versus 205 [113] s, respectively). In the SI group, administration of oxygen and epinephrine was significantly lower, whereas minute ventilation and exhaled CO2 were significantly increased. The SI group had significantly higher mean systemic and pulmonary arterial pressures during resuscitation in comparison with the 3:1 group (51 [10] versus 31 [5] mm Hg; 41[7] versus 31 [7] mm Hg, respectively; all P<0.05), with improved cardiac output and carotid blood flow. CONCLUSIONS: Combining CCs and SIs significantly improved the return of spontaneous circulation with better hemodynamic recovery in asphyxiated newborn piglets in comparison with standard coordinated 3:1 resuscitation.

Postresuscitation administration of doxycycline preserves cardiac contractile function in hypoxia-reoxygenation injury of newborn piglets*.

OBJECTIVE: Cardiac injury is common in asphyxiated neonates and is associated with matrix metalloproteinase-2 activation. Although studies have demonstrated the cardioprotective effects of matrix metalloproteinase inhibition, this has not been tested in clinically translatable models of hypoxia-reoxygenation injury. We aimed to elucidate the effect of doxycycline, a matrix metalloproteinase inhibitor, on cardiac injury and functional recovery in a swine model of neonatal hypoxia-reoxygenation. DESIGN: Thirty-three newborn piglets were acutely instrumented for continuous monitoring of cardiac output and systemic arterial pressure. After stabilization, normocapnic alveolar hypoxia (10-15% oxygen) was instituted for 2 hours followed by 4 hours of normoxic reoxygenation. Piglets were blindly, block randomized to receive IV boluses of normal saline (control) and doxycycline at 5 minutes of reoxygenation (n = 7/group). Sham-operated piglets (n = 5) received no hypoxia-reoxygenation. Markers of myocardial injury (plasma and myocardial tissue troponin I; myocardial lactate) and oxidative stress (lipid hydroperoxides) were measured by enzyme-linked immunosorbent assay and Western blot. Myocardial matrix metalloproteinase-2 activity was quantified by gelatin zymography and immunoprecipitation. SETTING: University animal laboratory. SUBJECTS: Piglets (1-4 d old, weighing 1.4-2.5 kg). INTERVENTIONS: IV doxycycline (3, 10, or 30 mg/kg) given during resuscitation. MEASUREMENTS AND MAIN RESULTS: Hypoxic piglets had cardiogenic shock (cardiac output 58% ± 1% of baseline), hypotension (systemic arterial pressure 31 ± 1 mm Hg), and acidosis (pH 7.02 ± 0.02). Doxycycline improved cardiac and stroke volume index with no chronotropic effect in doxycycline-treated piglets compared with controls. Systemic arterial pressure was higher and the pulmonary artery pressure/systemic arterial pressure ratio was lower in doxycycline groups, with reduced levels of markers of myocardial injury and oxidative stress in doxycycline-treated piglets compared with controls. Negative correlations were found between markers of myocardial injury (plasma troponin I, myocardial lactate) and functional recovery and between myocardial tissue and plasma troponin I. Doxycycline-treated piglets had lower myocardial matrix metalloproteinase-2 activity compared with controls. CONCLUSIONS: Postresuscitation administration of doxycycline attenuates cardiac injury and improves functional recovery in newborn piglets with hypoxia-reoxygenation.

Tidal volumes in spontaneously breathing preterm infants supported with continuous positive airway pressure.

OBJECTIVE: To describe changes in tidal volume (VT) and their correlation to changes in oxygen saturation and heart rate in spontaneously breathing preterm infants immediately after birth. STUDY DESIGN: In this prospective observational, 2-center study, a flow sensor was attached to the facemask of spontaneously breathing infants born at <37 weeks' gestational age who received continuous positive airway pressure (CPAP) immediately after birth. Respiratory function, heart rate, and oxygen saturation were continuously recorded during spontaneous breathing. RESULTS: Fifty-five infants (mean [SD] gestational age 31 [26-36] weeks and birth weight 1647 [500] g) received mask CPAP in the delivery room. CPAP was started at a median (IQR) 90 (60-118) seconds after birth and was delivered for 720 (300-900) seconds. Median VT ranged between 4.2 and 5.8 mL/kg with the individual VT varied between 0.9 and 19.8 mL/kg. Overall, VT increased over the first few minutes after birth and decreased thereafter. The increase in saturation after birth lagged behind the published normal ranges for spontaneously breathing preterm infants without CPAP. CONCLUSIONS: The 50th percentile for spontaneous VT in preterm infants during mask CPAP ranged from 4.2 to 5.8 mL/kg, with wide individual variation observed in the first minutes after birth. Preterm infants requiring CPAP after birth may take longer to achieve so-called "normal" saturation targets.

Cardiac effects of vasopressin.

Vasopressin is an essential hormone involved in the maintenance of cardiovascular homeostasis. It has been in use therapeutically for many decades, with an emphasis on its vasoconstrictive and antidiuretic properties. However, this hormone has a ubiquitous influence and has specific effects on the heart. Although difficult to separate from its powerful vascular effects in the clinical setting, a better understanding of vasopressin's direct cardiac effects could lead to its more effective clinical use for a variety of shock states by maximizing its therapeutic benefit. The cardiac-specific effects of vasopressin are complex and require further elucidation. Complicating our understanding include the various receptors and secondary messengers involved in vasopressin's effects, which may lead to various results based on differing doses and varying environmental conditions. Thus, there have been contradictory reports on vasopressin's action on the coronary vasculature and on its effect on inotropy. However, beneficial results have been found and warrant further study to expand the potential therapeutic role of vasopressin. This review outlines the effect of vasopressin on the coronary vasculature, cardiac contractility, and on hypertrophy and cardioprotection. These cardiac-specific effects of vasopressin represent an interesting area for further study for potentially important therapeutic benefits.