Chronic Maternal Hyperoxygenation and Effect on Cerebral and Placental Vasoregulation and Neurodevelopment in Fetuses with Left Heart Hypoplasia

INTRODUCTION

In a pilot study of chronic maternal hyperoxygenation (CMH) in left heart hypoplasia (LHH), we sought to determine effect estimates of CMH on head size, vascular resistance indices, and neurodevelopment compared to controls.

MATERIAL AND METHODS

Nine gravidae meeting the inclusion criteria (fetal LHH, ≥25.9 weeks' gestation, and ≥10% increase in percent aortic flow after acute hyperoxygenation) were prospectively enrolled. Controls were 9 contemporary gravidae with fetal LHH without CMH. Brain growth and Doppler-derived estimates of fetal cerebrovascular and placental resistance were blindly evaluated and compared using longitudinal regression. Postnatal anthropomorphic and neurodevelopmental assessments were compared.

RESULTS

There was no difference in baseline fetal measures between groups. There was significantly slower biparietal diameter (BPD) growth in the CMH group (z-score change -0.03 ± 0.02 vs. +0.09 ± 0.05 units/week, p = 0.02). At 6 months postnatal age, the mean head circumference z-score in the CMH group was smaller than that of controls (-0.20 ± 0.58 vs. +0.85 ± 1.11, p = 0.048). There were no differences in neurodevelopmental testing at 6 and 12 months.

DISCUSSION

In this pilot study, relatively diminished fetal BPD growth and smaller infant head circumference z-scores at 6 months were noted with in utero CMH exposure.

Hyperoxygenation Treatment Reduces Beta-amyloid Deposition via MeCP2-dependent Upregulation of MMP-2 and MMP-9 in the Hippocampus of Tg-APP/PS1 Mice

Recently we reported that hyperoxygenation treatment reduces amyloid-beta accumulation and rescues cognitive impairment in the Tg-APP/PS1 mouse model of Alzheimer’s disease. In the present study, we continue to investigate the mechanism by which hyperoxygenation reduces amyloid-beta deposition in the brain. Hyperoxygenation treatment induces upregulation of matrix metalloproteinase-2 (MMP-2), MMP-9, and tissue plasminogen activator (tPA), the endopeptidases that can degrade amyloid-beta, in the hippocampus of Tg-APP/PS1 mice. The promoter regions of the three proteinase genes all contain potential binding sites for MeCP2 and Pea3, which are upregulated in the hippocampus after hyperoxygenation. Hyperoxygenation treatment in HT22 neuronal cells increases MeCP2 but not Pea3 expression. In HT22 cells, siRNA-mediated knockdown of Mecp2 decreases Mmp-9 expression and to a lesser extent, Mmp-2 and tPA expression. In mice, siRNA-mediated Mecp2 knockdown in the hippocampus reduces Mmp-9 expression, but not significantly Mmp-2 and tPA expression. The ChIP assay indicates that hyperoxygenation treatment in Tg-APP/PS1 mice increases MeCP2 binding to the promoter regions of Mmp-2, Mmp-9 and tPA genes in the hippocampus. Together, these results suggest that hyperoxygenation increases the expression of MMP-2, MMP-9, and tPA, of which MMP-9 is upregulated via MeCP2 in neuronal cells, and MMP-2 and tPA are upregulated through MeCP2 and other nuclear factors.

The wound environment, microbial virulence and postoperative infection: Practical lessons for the surgeon

For the practicing surgeon, the development of a postoperative wound infection represents a major complication that can be both costly and disabling. As a result, surgeons apply multiple methods of prevention including skin decontamination, use of antibiotics, irrigation with or without antiseptics and meticulous use of technique. In elective surgery, however, most wound infections cannot be predicted. In this review we discuss emerging concepts in wound infection pathogenesis and include a discussion on how the wound environment may directly activate bacteria to express a more harmful or virulent phenotype. Based on these emerging concepts, we provide the practicing surgeon with molecular level evidence to explain why some methods of wound infection protection may be useful while others are not.

Calling into question the future of hyperoxygenation in pregnancy

Maternal hyperoxygenation has been investigated as a potential diagnostic and therapeutic tool since the 1960s. Since then, it has been applied in many obstetric scenarios, both clinically and in the research setting. It is often administered without any determination of pre-hyperoxygenation maternal or fetal oxygen levels. Studies focussing on maternal oxygen therapy for the treatment of fetal growth restriction have been ongoing for over thirty years and there remains no clear evidence of benefit. Studies investigating the potential diagnostic or therapeutic role of maternal oxygen therapy in the setting of fetal congenital cardiac disease have reported varying success rates and some potentially worrying adverse effects. The purpose of this article is to review the effects of maternal hyperoxygenation on fetal and maternal health and to ascertain the safety of undertaking further clinical trials that employ the use of hyperoxygenation in pregnancy.

Prenatal prediction of neonatal haemodynamic adaptation after maternal hyperoxygenation

Abstract

The reactivity of the pulmonary vascular bed to the administration of oxygen is well established in the post-natal circulation. The vasoreactivity demonstrated by the fetal pulmonary artery Doppler waveform in response to maternal hyperoxia has been investigated. We sought to investigate the relationship between the reactivity of the fetal pulmonary arteries to hyperoxia and subsequent neonatal cardiac function in the early newborn period.

Methods

This explorative study with convenience sampling measured pulsatility index (PI), resistance index (RI), acceleration time (AT), and ejection time (ET) from the fetal distal branch pulmonary artery (PA) at baseline and following maternal hyperoxygenation (MH). Oxygen was administered for 10 min at a rate of 12 L/min via a partial non-rebreather mask. A neonatal functional echocardiogram was performed within the first 24 h of life to assess ejection fraction (EF), left ventricular output (LVO), and neonatal pulmonary artery AT (nPAAT). This study was conducted in the Rotunda Hospital, Dublin, Ireland.

Results

Forty-six women with a singleton pregnancy greater than or equal to 31 weeks’ gestational age were prospectively recruited to the study. The median gestational age was 35 weeks. There was a decrease in fetal PAPI and PARI following MH and an increase in fetal PAAT, leading to an increase in PA AT:ET. Fetuses that responded to hyperoxygenation were more likely to have a higher LVO (135 ± 25 mL/kg/min vs 111 ± 21 mL/kg/min, p < 0.01) and EF (54 ± 9% vs 47 ± 7%,p = 0.03) in the early newborn period than those that did not respond to MH prenatally. These findings were not dependent on left ventricular size or mitral valve (MV) annular diameter but were related to an increased MV inflow. There was no difference in nPAAT.

Conclusion

These findings indicate a reduction in fetal pulmonary vascular resistance (PVR) and an increase in pulmonary blood flow and left atrial return following MH. The fetal response to hyperoxia reflected an optimal adaptation to postnatal life with rapid reduction in PVR increasing measured cardiac output.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-020-03403-y.

Effect of Hyperoxygenation During Surgery on Surgical Site Infection in Colorectal Surgery

Purpose

Despite the use of different surgical methods, surgical site infection is still an important cause of mortality and morbidity in patients and imposes a considerable cost on the healthcare system. Administration of supplemental oxygen during surgery has been reported to reduce surgical site infection (SSI); however, that result is still controversial. This study was performed to evaluate the effect of hyperoxygenation during colorectal surgery on the incidence of wound infection.

Methods

This study was a prospective double-blind case-control study. The main aim of the study was to evaluate the effect of hyperoxygenation during colorectal surgery on the incidence of SSI. Also, secondary outcomes, such as atelectasis, pneumonia, respiratory failure, length of hospital stay, and required hospitalization in the intensive care unit were evaluated.

Results

SSI was recorded in 2 patients (2 of 40, 5%) in the hyperoxygenation group (FiO₂ 80%) and 6 patients (6 of 40, 15%) in the control group (FiO₂ 30%) (P < 0.05). Time of hospitalization was 6 ± 6.4 days in the hyperoxygenation group and 9.2 ± 2.4 days in the control group (P < 0.05).

Conclusion

This study showed a positive effect of hyperoxygenation in reducing SSI in colorectal surgery, especially surgery in an emergency setting. When the low risk, low cost, and effectiveness of this method in patients undergoing a laparotomy are considered, it is recommended for all patients undergoing colorectal surgery.

The Influence of Hyperoxygenation on Fetal Brain Vascularity Measured Using 3D Power Doppler Ultrasound and the Index "Fractional Moving Blood Volume"

INTRODUCTION

Maternal hyperoxygenation effects on fetal cerebral hemodynamics are largely unknown. This study aimed to determine efficacy and reliability of a validated power Doppler ultrasound (US) index, fractional moving blood volume (FMBV), at measuring fetal cerebral vasculature changes during maternal hyperoxia.

METHODS

The fetal cerebral effects of 10 min of hyperoxygenation at 2 flow rates (52%/60% FiO2) were evaluated in women in their third trimester of pregnancy. 2D-US and 3D-US in a transverse plane were performed before, during, and following maternal hyperoxygenation with FMBV estimation performed offline.

RESULTS

Forty-five cases provided data for analysis. Mean intraobserver ICCs were 0.89 (3D-FMBV) and 0.84 (2D-FMBV). A significant difference in vascularity before and during and before and after 60% hyperoxia was observed (p < 0.05), whereas no significant differences were found at 52% hyperoxia (p > 0.05). Significant differences in vascularity were found between 2D-FMBV and 3D-FMBV (p < 0.01).

CONCLUSION

Measurement of fetal cerebral vascularity by 3D-FMBV and 2D-FMBV was highly reproducible. The differing cerebral vascular changes seen with 60% but not 52% FiO2 suggest a possible "threshold effect" that may have influenced prior studies. Further studies are needed to assess cerebral effects of maternal hyperoxygenation on compromised fetuses.

Can sonographic assessment of pulmonary vascular reactivity following maternal hyperoxygenation predict neonatal pulmonary hypertension? (HOTPOT study protocol)

Background

Persistent pulmonary hypertension of the newborn (PPHN) is a condition that occurs in 0.5–7 per 1000 live births and can result in significant cardiovascular instability in the newborn. It occurs when there is a failure of the normal circulatory transition in the early newborn period. Recent studies have shown that fetal pulmonary vasculature reacts to maternal hyperoxygenation (MH). The aim of the study is to assess if the in-utero response to MH can predict pulmonary hypertension in the early newborn period.

Methods

We will perform a prospective cohort study. It will evaluate the use of fetal echocardiographic Doppler assessment of the pulmonary vasculature prior to and following MH to predict fetuses that may develop pulmonary hypertension in the neonatal period. The study will be undertaken in the Rotunda Hospital, Dublin, Ireland. A fetal ultrasound and echocardiography will be performed on fetuses in the third trimester. Blood flow velocity waveforms will be recorded during periods of fetal quiescence. Pulsatility index (PI), Resistance index (RI), Peak systolic (PSV) and end diastolic velocity (EDV), time-averaged velocity (TAV), acceleration time (AT), and ejection time (ET) will be measured within the fetal distal pulmonary artery (PA). The acceleration-to-ejection time ratio (AT: ET) will be used to assess pulmonary vascular resistance (PVR). Doppler measurements will be taken at baseline and repeated immediately following MH for 10 min (O2 100% v/v inhalational gas) at a rate of 12L/min via a partial non-rebreather mask. Doppler waveform measurements from the umbilical artery (UAD), middle cerebral artery (MCA) ductus arteriosus (DA), aortic isthmus (AoI) and ductus venosus (DV) will also be obtained. After birth, a comprehensive neonatal functional echocardiogram will be performed within the first 24 hours of life.

Discussion

This study proposes to validate methods described to date in investigating the fetal pulmonary vascular response to MH, with expansion of the study subjects to include fetuses at risk of PPHN. Evaluation of the different at-risk subgroups will be informative in relation to the fetal circulatory adaptation close to term. Prediction of neonatal pulmonary hypertension may help guide the pharmacological and neonatal ICU strategies that optimise postnatal survival.

Hyperoxygenation Ameliorates Stress-induced Neuronal and Behavioral Deficits

Hyperoxygenation therapy remediates neuronal injury and improves cognitive function in various animal models. In the present study, the optimal conditions for hyperoxygenation treatment of stress-induced maladaptive changes were investigated. Mice exposed to chronic restraint stress (CRST) produce persistent adaptive changes in genomic responses and exhibit depressive-like behaviors. Hyperoxygenation treatment with 100% O₂ (HO₂) at 2.0 atmospheres absolute (ATA) for 1 h daily for 14 days in CRST mice produces an antidepressive effect similar to that of the antidepressant imipramine. In contrast, HO₂ treatment at 2.0 ATA for 1 h daily for shorter duration (3, 5, or 7 days), HO₂ treatment at 1.5 ATA for 1 h daily for 14 days, or hyperbaric air treatment at 2.0 ATA (42% O₂) for 1 h daily for 14 days is ineffective or less effective, indicating that repeated sufficient hyperoxygenation conditions are required to reverse stress-induced maladaptive changes. HO₂ treatment at 2.0 ATA for 14 days restores stress-induced reductions in levels of mitochondrial copy number, stress-induced attenuation of synaptophysin-stained density of axon terminals and MAP-2-staining dendritic processes of pyramidal neurons in the hippocampus, and stress-induced reduced hippocampal neurogenesis. These results suggest that HO₂ treatment at 2.0 ATA for 14 days is effective to ameliorate stress-induced neuronal and behavioral deficits.

A positive association of larval therapy and hyperbaric oxygen therapy in veterinary wound care

The treatment of cutaneous wounds is part of the veterinary routine from initial scientific reports due to being regularly present condition. Currently, several types of treatments are available to accelerate the healing process. This report presents the case of a dog with multiple lesions in the thoracic limbs resulting from a car accident, who underwent larval therapy and hyperbaric oxygen therapy (HBOT). The animal was a 2-year-old female mixed breed dog presenting severe skin degloving, fracture in the left thoracic limb (LTL), with abrasion lesions and dislocation in the right thoracic limb (RTL). The animal underwent multiple modality therapies, such as HBOT sessions associated with larval therapy; even after the LTL presented gangrene, this treatment resulted in optimal viability of the non-necrotic tissue adjacent to the gangrene. Due to chronic pain unresponsive to drug control and the presence of a fracture at a location where a possible exoprosthesis was supposed to be fixed, the LTL ended up being amputated. There are several reports of the use of HBOT or larval therapy in traumatized limbs; however, the combination of both therapies has not been previously described in the veterinary literature. Thus, we demonstrate through this report that it was possible to quickly recover the animal with good wound resolution through tissue oxygenation and a healthy granulation bed, both provided by the therapeutic combination.

Insufficient Oxygen Supplementation During Cardiopulmonary Resuscitation Leads to Unfavorable Biological Response While Hyperoxygenation Contributes to Metabolic Compensation

Sudden cardiac arrest (CA) is the third leading cause of death. Immediate reoxygenation with high concentrations of supplemental oxygen (O2) during cardiopulmonary resuscitation (CPR) is recommended according to the current guidelines for adult CA. However, a point in controversy exists because of the known harm of prolonged exposure to 100% O2. Therefore, there have been much debate on an optimal use of supplemental O2, yet little is known about the duration and dosage of O2 administration. To test whether supplying a high concentration of O2 during CPR and post resuscitation is beneficial or harmful, rats subjected to 10-minute asphyxia CA were administered either 100% O2 (n = 8) or 30% O2 (n = 8) for 2 hours after CPR. Two hours after initiating CPR, the brain, lung, and heart tissues were collected to compare mRNA gene expression levels of inflammatory cytokines, apoptotic and oxidative stress-related markers. The 100% O2 group had significantly shorter time to return of spontaneous circulation (ROSC) than the 30% O2 group (62.9 ± 2.2 and 77.5 ± 5.9 seconds, respectively, P < 0.05). Arterial blood gas analysis revealed that the 100% O2 group had significantly higher PaCO2 (49.4 ± 4.9 mmHg and 43.0 ± 3.0 mmHg, P < 0.01), TCO2 (29.8 ± 2.7 and 26.6 ± 1.1 mmol/L, P < 0.05), HCO3- (28.1 ± 2.4 and 25.4 ± 1.2 mmol/L, P < 0.05), and BE (2.6 ± 2.3 and 0.1 ± 1.4 mmol/L, P < 0.05) at 2 hours after initiating CPR, but no changes in pH (7.37 ± 0.03 and 7.38 ± 0.03, ns). Inflammation- (Il6, Tnf) and apoptosis- (Casp3) related mRNA gene expression levels were significantly low in the 100% O2 group in the brain, however, oxidative stress moderator Hmox1 increased in the 100% O2 group. Likewise, mRNA gene expression of Icam1, Casp9, Bcl2, and Bax were low in the 100% O2 group in the lung. Contrarily, mRNA gene expression of Il1b and Icam1 were low in the 30% O2 group in the heart. Supplying 30% O2 during and after CPR significantly delayed the time to ROSC and increased inflammation-/apoptosis- related gene expression in the brain and lung, indicating that insufficient O2 was associated with unfavorable biological responses post CA, while prolonged exposure to high-concentration O2 should be still cautious in general.