No neuroprotective effect of therapeutic hypothermia following lipopolysaccharide-sensitized hypoxia-ischemia: a newborn piglet study.

Introduction: Therapeutic hypothermia is the only proven neuroprotective treatment for hypoxic-ischemic encephalopathy. However, studies have questioned whether therapeutic hypothermia may benefit newborns subjected to infection or inflammation before a hypoxic-ischemic insult. We aimed to compare newborn piglets with lipopolysaccharide-sensitized hypoxia-ischemia treated with and without therapeutic hypothermia with regards to measures of neuroprotection. Methods: A total of 32 male and female piglets were included in this randomized experimental study. Lipopolysaccharides from Escherichia coli were infused intravenously before initiation of a standardized global hypoxic-ischemic insult. The piglets were then randomized to either normothermia or therapeutic hypothermia. After 14 h, the piglets were evaluated. Our primary outcome was brain lactate/N-acetylaspartate ratio assessed by magnetic resonance spectroscopy. Secondary outcomes included measures of magnetic resonance imaging, amplitude-integrated electroencephalography, immunohistochemistry, and concentration of blood cells and cytokines. Results: Piglets treated with and without therapeutic hypothermia were subjected to comparable global hypoxic-ischemic insults. We found no difference between the two groups with regards to measures of magnetic resonance spectroscopy and imaging, amplitude-integrated electroencephalography, immunohistochemistry, and concentration of blood cells and cytokines. Conclusion: We found no indication of neuroprotection by therapeutic hypothermia in newborn piglets following lipopolysaccharide-sensitized hypoxia-ischemia. However, interpretation of the results is limited by the short observation period. Further studies are required to determine the potential clinical implications of these findings.

Point-of-care ultrasound in neonatal intensive care.

This review investigates how point-of-care ultrasound (POCUS) allows individualised treatment based on the patient's clinical and physiological state. Serial examinations enable timely adjustments of interventions, potentially fewer side effects, and less need for x-ray examinations. One of the main barriers to POCUS is the lack of systematic training and quality control. The next step toward more widespread use of neonatal POCUS is systematic theoretical and practical training and implementing standardized examination protocols.

Hypothermia and heart rate variability in a healthy newborn piglet model.

Decreased heart rate variability (HRV) may be a biomarker of brain injury severity in neonatal hypoxic-ischemic encephalopathy for which therapeutic hypothermia is standard treatment. While therapeutic hypothermia may influence the degree of brain injury; hypothermia may also affect HRV per se and obscure a potential association between HRV and hypoxic-ischemic encephalopathy. Previous results are conflicting. This study aimed to investigate the effect of hypothermia on HRV in healthy, anaesthetised, newborn piglets. Six healthy newborn piglets were anaesthetised. Three piglets were first kept normothermic (38.5-39.0 °C) for 3 h, then exposed to hypothermia (33.5-34.5 °C) for 3 h. Three piglets were first exposed to hypothermia for 3 h, then rewarmed to normothermia for 3 h. Temperature and ECG were recorded continuously. HRV was calculated from the ECG in 5 min epochs and included time domain and frequency domain variables. The HRV variables were compared between hypothermia and normothermia. All assessed HRV variables were higher during hypothermia compared to normothermia. Heart rate was lower during hypothermia compared to normothermia and all HRV variables correlated with heart rate. Hypothermia was associated with an increase in HRV; this could be mediated by bradycardia during hypothermia.

Remote ischemic postconditioning increased cerebral blood flow and oxygenation assessed by magnetic resonance imaging in newborn piglets after hypoxia-ischemia.

Background: We have previously investigated neurological outcomes following remote ischemic postconditioning (RIPC) in a newborn piglet model of hypoxic-ischemic encephalopathy. The aim of this study was to further investigate potential mechanisms of neuroprotection by comparing newborn piglets subjected to global hypoxia-ischemia (HI) treated with and without RIPC with regards to measures of cerebral blood flow and oxygenation assessed by functional magnetic resonance imaging. Materials and methods: A total of 50 piglets were subjected to 45 min global HI and randomized to either no treatment or RIPC treatment. Magnetic resonance imaging was performed 72 h after the HI insult with perfusion-weighted (arterial spin labeling, ASL) and oxygenation-weighted (blood-oxygen-level-dependent, BOLD) sequences in the whole brain, basal ganglia, thalamus, and cortex. Four sham animals received anesthesia and mechanical ventilation only. Results: Piglets treated with RIPC had higher measures of cerebral blood flow in all regions of interest and the whole brain (mean difference: 2.6 ml/100 g/min, 95% CI: 0.1; 5.2) compared with the untreated controls. They also had higher BOLD values in the basal ganglia and the whole brain (mean difference: 4.2 T2*, 95% CI: 0.4; 7.9). Measures were similar between piglets treated with RIPC and sham animals. Conclusion: Piglets treated with RIPC had higher measures of cerebral blood flow and oxygenation assessed by magnetic resonance imaging in the whole brain and several regions of interest compared with untreated controls 72 h after the HI insult. Whether this reflects a potential neuroprotective mechanism of RIPC requires further study.

Neurofilament Light Chain serum levels after Hypoxia-Ischemia in a newborn piglet model.

Aim: Neurofilament light Chain (NfL) is a promising brain injury biomarker which may assist diagnosis and prognostication in hypoxic-ischemic encephalopathy (HIE). The aim of this study was to investigate serum NfL levels after hypoxia-ischemia (HI) in a newborn piglet model. Second, to characterize the influence of sex, weight, and treatment with remote ischemic postconditioning (RIPC) on NfL and the correlation between NfL, brain imaging and histologic brain injury. Methods: We used serum from 48 newborn piglets of both sexes subjected to 45 min of global HI, and 4 sham piglets. Blood was collected pre-HI, 2 h post-HI and 72 h post-HI. NfL was measured by single-molecule array (Simoa™). We analysed the temporal profile of NfL after HI, and correlations between NfL, magnetic resonance spectroscopy brain Lac/NAA ratios and histologic brain injury 72 h after HI. Results: Median (IQR) NfL levels were: pre-HI: 66 pg/ml (45-87), 2 h post-HI: 105 pg/ml (77-140), and 72 h post-HI: 380 pg/ml (202-552). The increase in NfL after HI was statistically significant (p < 0.0001, mixed-effects ANOVA). Median NfL levels in sham animals were 41.4 pg/ml at baseline and 92.4 pg/ml at 72 h (p = 0.11, paired t-test). Neither sex, nor treatment with RIPC influenced NfL levels. Weight had a small, not biologically important, influence. NfL levels at 72 h were moderately correlated with histologic brain injury and brain Lac/NAA ratios. NfL 72 h post-HI > 330 pg/ml had a sensitivity of 89% (95% CI, 57%-99%) and a specificity of 52% (95% CI, 34%-69%) for predicting basal ganglia Lac/NAA ratio in the highest quartile. NfL 72 h post-HI > 445 pg/ml had a sensitivity of 90% (95% CI, 60%-99%) and a specificity of 74% (95% CI, 58%-86%) for predicting cortical brain histopathology injury in the highest quartile. Conclusion: NfL increased after HI, with the largest values at 72 h post-HI. Early NfL was sensitive but not very specific, whereas NfL at 72 h was both highly sensitive and specific for exposure to moderate-severe HI in this model of HI-induced brain injury. This was supported by a moderate correlation of NfL at 72 h with brain Lac/NAA ratio and histopathology.

Neurological Outcome Following Newborn Encephalopathy With and Without Perinatal Infection: A Systematic Review.

Background: Studies have suggested that neurological outcome may differ in newborns with encephalopathy with and without perinatal infection. We aimed to systematically review this association. Methods: We conducted this systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Studies were obtained from four databases including Pubmed, Embase, Web of Science, and The Cochrane Database. Newborns with encephalopathy with and without markers of perinatal infection were compared with regard to neurodevelopmental assessments, neurological disorders, and early biomarkers of brain damage. Risk of bias and quality of evidence were assessed by the Newcastle-Ottawa scale and Grading of Recommendations Assessment, Development and Evaluation (GRADE). Results: We screened 4,284 studies of which eight cohort studies and one case-control study met inclusion criteria. A narrative synthesis was composed due to heterogeneity between studies. Six studies were classified as having low risk of bias, while three studies were classified as having high risk of bias. Across all outcomes, the quality of evidence was very low. The neurological outcome was similar in newborns with encephalopathy with and without markers of perinatal infection. Conclusions: Further studies of higher quality are needed to clarify whether perinatal infection may affect neurological outcome following newborn encephalopathy. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42020185717.

[Asphyxia and hypoxic-ischaemic encephalopathy].

Hypoxic-ischaemic encephalopathy is a common cause of death and disability in newborns. Brain damage related to a perinatal insult is the result of a dynamic process, and its progressing development over time allows for specific interventions to reduce total damage, as described in this review. Despite therapeutic hypothermia which currently is the only treatment available, a considerable number of newborns still have adverse outcomes. Prognosis is evaluated by clinical examination and paraclinical investigations. There is still a need for novel treatments and better prognostic and diagnostic tools to improve outcome.

Learning Curves for Training in Ultrasonography-Based Examination of Umbilical Catheter Placement: A Piglet Study.

BACKGROUND: The training required for accurate assessment of umbilical catheter placement by ultrasonography (US) is unknown. OBJECTIVE: To describe the learning curve and provide an estimate of the accuracy of physicians' US examinations (US skills) and self-confidence when examining umbilical catheter tip placement. METHODS: Twenty-one physicians with minimal experience in US completed a 1.5-hour eLearning module. Ten piglets with catheters inserted in the umbilical vessels were used as training objects. Following eLearning each physician performed up to twelve 10-min US examinations of the piglets. Expert examinations were reference standards. Sensitivity and specificity of physicians' skills in detecting catheter tip placement by US was used to describe the learning curve. Self-confidence was reported by Likert scale after each examination. RESULTS: Physicians' detection of a correctly placed and misplaced umbilical artery catheter tip increased by an odds ratio of 1.6 (95% CI: 1.1, 2.3) and 3.6 (95% CI: 1.7, 7.8) per examination performed. A sensitivity of 0.97 (95% CI: 0.80, 0.99) and specificity of 0.95 (95% CI: 0.84, 0.99) was reached after 6 examinations. For the venous catheter, US skills in detecting a misplaced catheter tip increased with an odds ratio of 2.4 (95% CI: 1.2, 4.8) per US examination. Overall, performance and self-confidence plateaus were reached after 6 examinations. CONCLUSION: We found steep learning curves for targeted US examination of umbilical catheter placement. eLearning followed by 6 examinations was found to be adequate training to perform with a sufficiently high accuracy and self-confidence to allow for point-of-care use.

Consequence of insertion trauma - effect on early measurements when using intracerebral devices.

There are a variety of devices that quantify biological properties of cerebral tissue. Installing such device will cause a local insertion trauma, which will affect early measurements. Current literature proposes minimum one hour of observation before acquiring first measurements when using microdialysis. It is unknown whether this applies to other intracerebral devices. We therefore aimed to investigate time needed to reach steady state when using microdialysis and two intracerebral probes in a piglet model. Ten newborn piglets less than 24 hours of age were anaesthetized. Two probes (Codman and OxyLite/OxyFlo) and a microdialysis catheter (CMA Microdialysis) were installed 10 mm into the left hemisphere. Probes measured intracranial pressure, cerebral blood flow, and oxygen tension. The microdialysis catheter measured lactate, glucose, glycerol, and pyruvate. Measurements were acquired hourly for 20 hours. Lactate and glycerol peaked immediately after insertion and reached steady state after approximately four hours. Glucose, pyruvate, cerebral blood flow, and intracranial pressure reached steady state immediately. Oxygen tension reached steady state after 12 hours. With time, interindividual variability decreased for the majority of measurements. Consequently, time to stabilization after insertion depends on the choice of device and is crucial to obtain valid baseline values with high degree of precision.

Biomarker Discovery by Mass Spectrometry in Cerebrospinal Fluid and Plasma after Global Hypoxia-Ischemia in Newborn Piglets.

BACKGROUND: Biomarkers may qualify diagnosis, treatment allocation, and prognostication in neonatal encephalopathy. Biomarker development is challenged by competing etiologies, inter-individual genetic variability, and a lack of specific neonatal markers. To address these challenges, we used a standardized neonatal hypoxic-ischemic (HI) encephalopathy model with pre- and post-HI sampling of cerebrospinal fluid (CSF) and plasma. OBJECTIVES: The study aimed to identify novel candidate protein biomarkers of HI encephalopathy in a newborn piglet model in CSF and plasma. METHODS: FiO2 was lowered to 4% in 6 newborn piglets, then adjusted over a 45-min period keeping the amplitude integrated-EEG < 7 µV to induce HI encephalopathy. CSF and plasma was sampled pre-HI and 2 h after HI, protein levels were then analyzed by mass spectrometry. RESULTS: Protein levels after HI changed significantly for 18 CSF proteins and 37 plasma proteins. CSF and plasma data showed distinct information, although peptidyl-prolyl cis-trans isomerase A had elevated levels in both fluids. HI regulation involved functional groups such as the antioxidant system, cell proliferation, cell structure, and apoptosis. S100-A8, which increased the most in CSF (9.5 fold), is known to be involved in inflammatory and immune response and to be highly regulated during injury. In plasma, increased proteins included FABP1 (31.8 fold) and proteins with antioxidant (SOD1, GPX3) and lectin function (REG3A, LGALS3). CONCLUSIONS: In this exploratory study, we have identified candidate biomarkers for HI in CSF and plasma, many not previously associated with HI. Identified proteins are promising candidates for further validation in time series experiments and clinical studies.