Preterm neonates exposed to painful NICU procedures exhibit increased pain scores and alterations in oxygenation and heart rate. It is unclear whether these physiologic responses increase the risk of oxidative stress. Using a prospective study design, we examined the relationship between a tissue-damaging procedure (TDP, tape removal during discontinuation of an indwelling central arterial or venous catheter) and oxidative stress in 80 preterm neonates. Oxidative stress was quantified by measuring uric acid (UA) and malondialdehyde (MDA) concentration in plasma before and after neonates experienced a TDP (n=38) compared to those not experiencing any TDP (control group, n=42). Pain was measured before and during the TDP using the Premature Infant Pain Profile(PIPP). We found that pain scores were higher in the TDP group compared to the control group (median scores:11 and 5, respectively, P<0.001). UA significantly decreased over time in control neonates but remained stable in TDP neonates (132.76μM to 123.23μM vs.140.50μM to 138.9μM, P=0.002). MDA levels decreased over time in control neonates but increased in TDP neonates (2.07μM to 1.81μM vs. 2.07μM to 2.21μM, P=0.01). We found significant positive correlations between PIPP scores and MDA. Our data suggest a significant relationship between procedural pain and oxidative stress in preterm neonates.

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Neonatal hypoxia ischemia is characterized by inadequate blood perfusion of a tissue or a systemic lack of oxygen. This condition is thought to cause/exacerbate well documented neonatal disorders including neurological impairment 1-3 . Decreased adenosine triphosphate production occurs due to a lack of oxidative phosphorylation. To compensate for this energy deprived state molecules containing high energy phosphate bonds are degraded 2 . This leads to increased levels of adenosine which is subsequently degraded to inosine, hypoxanthine, xanthine, and finally to uric acid. The final two steps in this degradation process are performed by xanthine oxidoreductase. This enzyme exists in the form of xanthine dehydrogenase under normoxic conditions but is converted to xanthine oxidase (XO) under hypoxia-reperfusion circumstances 4, 5 . Unlike xanthine dehydrogenase, XO generates hydrogen peroxide as a byproduct of purine degradation 4, 6 . This hydrogen peroxide in combination with other reactive oxygen species (ROS) produced during hypoxia, oxidizes uric acid to form allantoin and reacts with lipid membranes to generate malondialdehyde (MDA) [7][8][9] . Most mammals, humans exempted, possess the enzyme uricase, which converts uric acid to allantoin. In humans, however, allantoin can only be formed by ROS-mediated oxidation of uric acid. Because of this, allantoin is considered to be a marker of oxidative stress in humans, but not in the mammals that have uricase.We describe methods employing high pressure liquid chromatography (HPLC) and gas chromatography mass spectrometry (GCMS) to measure biochemical markers of neonatal hypoxia ischemia. Human blood is used for most tests. Animal blood may also be used while recognizing the potential for uricase-generated allantoin. Purine metabolites were linked to hypoxia as early as 1963 and the reliability of hypoxanthine, xanthine, and uric acid as biochemical indicators of neonatal hypoxia was validated by several investigators [10][11][12][13] . The HPLC method used for the quantification of purine compounds is fast, reliable, and reproducible. The GC/MS method used for the quantification of allantoin, a relatively new marker of oxidative stress, was adapted from Gruber et al 7 . This method avoids certain artifacts and requires low volumes of sample. Methods used for synthesis of MMDA were described elsewhere 14,15 . GC/MS based quantification of MDA was adapted from Paroni et al. and Cighetti et al. 16,17 . Xanthine oxidase activity was measured by HPLC by quantifying the conversion of pterin to isoxanthopterin 18 . This approach proved to be sufficiently sensitive and reproducible.

Neonatal hypoxia is a clinical condition with detrimental biochemical and clinical outcomes, including production of reactive oxygen and nitrogen species, ATP depletion, developmental abnormalities and growth retardation. Diagnostic approaches for hypoxia are largely based on nonspecific clinical criteria, such as Apgar score, umbilical cord pH and fetal heart-rate monitoring. Since our understanding of the biochemical processes of hypoxia has improved, several biochemical markers have been developed. This article highlights the use of hypoxanthine, xanthine, uric acid, xanthine oxidase, malondialdehyde, nitrotyrosine and lactate as markers of hypoxia in animal models, preterm neonates and full-term neonates.

Neonates exposed to common neonatal intensive care unit (NICU) procedures show alterations in heart rate, blood pressure, and oxygen saturation. However, it is unclear if these physiologic changes increase adenosine triphosphate (ATP) utilization, thus potentially increasing the risk for tissue hypoxia in medically fragile neonates. Plasma uric acid is a commonly used marker of increased ATP utilization because uric acid levels increase when ATP consumption is enhanced. To examine the effect of a common NICU procedure on plasma uric acid concentration, we developed a model that allows for acute monitoring of this biochemical marker in plasma in 7- to 9-day-old rabbits. In our pilot study, we exposed neonatal rabbits to a single heel lance 2.5 hr after catheter placement. We measured uric acid concentration before and 30 min after the heel lance and compared findings to levels in control animals not exposed to the heel lance. Our pilot data shows a significant difference in uric acid concentration over time between the control and heel lance groups (46.2 ± 7.1 μM vs. 54.7 ± 5.8 μM, respectively, p = .027). Calculation of percentage change from baseline showed uric acid concentration increasing in rabbits exposed to heel lance and decreasing in control rabbits (1.5 ± 4.7% vs. –16.1 ± 4.2%, respectively, p = .03). These data suggest that this animal model can be successfully used to examine the biochemical effect of common NICU procedures, such as heel lance, on markers of ATP breakdown and purine metabolism.

Neonatal hypoxia ischemia is characterized by inadequate blood perfusion of a tissue or a systemic lack of oxygen. This condition is thought to cause/exacerbate well documented neonatal disorders including neurological impairment [1][2][3] . Decreased adenosine triphosphate production occurs due to a lack of oxidative phosphorylation. To compensate for this energy deprived state molecules containing high energy phosphate bonds are degraded 2 . This leads to increased levels of adenosine which is subsequently degraded to inosine, hypoxanthine, xanthine, and finally to uric acid. The final two steps in this degradation process are performed by xanthine oxidoreductase. This enzyme exists in the form of xanthine dehydrogenase under normoxic conditions but is converted to xanthine oxidase (XO) under hypoxia-reperfusion circumstances 4, 5 . Unlike xanthine dehydrogenase, XO generates hydrogen peroxide as a byproduct of purine degradation 4, 6 . This hydrogen peroxide in combination with other reactive oxygen species (ROS) produced during hypoxia, oxidizes uric acid to form allantoin and reacts with lipid membranes to generate malondialdehyde (MDA) [7][8][9] . Most mammals, humans exempted, possess the enzyme uricase, which converts uric acid to allantoin. In humans, however, allantoin can only be formed by ROS-mediated oxidation of uric acid. Because of this, allantoin is considered to be a marker of oxidative stress in humans, but not in the mammals that have uricase.We describe methods employing high pressure liquid chromatography (HPLC) and gas chromatography mass spectrometry (GCMS) to measure biochemical markers of neonatal hypoxia ischemia. Human blood is used for most tests. Animal blood may also be used while recognizing the potential for uricase-generated allantoin. Purine metabolites were linked to hypoxia as early as 1963 and the reliability of hypoxanthine, xanthine, and uric acid as biochemical indicators of neonatal hypoxia was validated by several investigators [10][11][12][13] . The HPLC method used for the quantification of purine compounds is fast, reliable, and reproducible. The GC/MS method used for the quantification of allantoin, a relatively new marker of oxidative stress, was adapted from Gruber et al 7 . This method avoids certain artifacts and requires low volumes of sample. Methods used for synthesis of MMDA were described elsewhere 14,15 . GC/MS based quantification of MDA was adapted from Paroni et al. and Cighetti et al. 16,17 . Xanthine oxidase activity was measured by HPLC by quantifying the conversion of pterin to isoxanthopterin 18 . This approach proved to be sufficiently sensitive and reproducible.

Introduction: The COVID-19 pandemic caused disruptions in the health services delivery, especially among vulnerable populations. We assessed if the pandemic widened disparities in care for cardiometabolic conditions in a LGBTQ+-focused federally qualified health system in Chicago. Hypothesis: Disparities in monitoring cardiometabolic conditions present in 2019 worsened in 2020. Methods: We analyzed electronic health records from Howard Brown Health. We assessed HbA1c re-testing and control (≤9%) in 2019 and 2020 among people with diabetes (DM) and ≥1 HbA1c test in the prior year (2018 for 2019, 2019 for 2020) (n2019=818, n2020=1033). A similar assessment was done for hypertension (HTN) with systolic blood pressure (SBP) (n2019=2813, n2020=3660). Comparisons per demographic group per year were done using logistic regression adjusting for socio-demographic variables. Results: Re-testing rates declined from 2019 to 2020 for both HbA1c and SBP overall and across all groups. Adjusted analysis showed gay people with DM had higher rates of HbA1c re-testing than people of other sexual orientations in 2019 and experienced a significantly lower re-testing rate decline in 2020. Adjusted analysis for SBP showed that white (vs Hispanic) and straight (vs gay) people with HTN had lower SBP re-testing rates in 2019 and 2020. Rates of controlled SBP (<140mmHg), but not HbA1c (≤9%), declined from 2019 to 2020. Adjusted analyses showed that straight (vs gay) patients had lower controlled HbA1c and SBP rates. Cis males (vs trans males) had lower controlled SBP and white (vs Asian/other) had lower controlled HbA1c. These disparities did not worsen in 2020. Conclusion: The pandemic had mixed impacts on cardiometabolic service disparities in a large LGBTQ+-focused health system. Disparities by sexual orientation for HbA1c widened during the pandemic. Similar worsening was not found for systolic blood pressure, nor for other demographic groups.

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