Neonatal hemodynamic responses to extreme ranges of controlled graded hypoxia

Torrance, Shona M.; Wittnich, Carin

doi:10.1097/00003246-199611000-00020

Cited by 3 publications

(3 citation statements)

References 30 publications

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“…One interpretation of these findings is that the reduction in renal blood flow or glomerular filtration rate seen at high-altitude (37,39,43) does not influence the kidneys capacity to filtrate and excrete HCO 3 in the urine as previously hypothesized (39,58). Conversely, this may imply RDO 2 influences the tubular handling of HCO 3 − and H + (18,49). RDO 2 at high-altitude may impact the activity of intracellular carbonic anhydrase (23), proton secretion via the Na + -H + exchanger (NHE3) (2) and/or activity of intercalated cells on the collecting ducts (15).…”

Section: Rdo 2 and Acid-base Acclimatizationmentioning

confidence: 99%

“…The contributions of renal blood flow and CaO 2 on RDO 2 has yet to be characterized at highaltitude, and may have functional consequences on acid-base acclimatization (18,49).…”

Section: Introductionmentioning

confidence: 99%

“…High-altitude driven hyperventilation decreases the partial pressure of arterial carbon dioxide (PaCO 2 ), resulting in respiratory alkalosis (10,47 (49).…”

Section: Introductionmentioning

confidence: 99%

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Global REACH 2018: renal oxygen delivery is maintained during early acclimatization to 4,330 m

Steele

Tymko

Meah

et al. 2020

American Journal of Physiology-Renal Physiology

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Early acclimatization to high-altitude is characterized by various respiratory, hematological, and cardiovascular adaptations that serve to restore oxygen delivery to tissue. However, less is understood about renal function and the role of renal oxygen delivery (RDO2) during high-altitude acclimatization. We hypothesized that: 1) RDO2 would be reduced after 12-hours of high-altitude exposure (high-altitude day1) but restored to sea-level values after one-week (high-altitude day7); and 2) RDO2 would be associated with renal reactivity (RR), an index of acid-base compensation at high-altitude. Twenty-four healthy lowlander participants were tested at sea-level (344m; Kelowna, Canada), on day1 and day7 at high-altitude (4330m; Cerro de Pasco, Peru). Cardiac output, renal blood flow, arterial and venous blood sampling for renin-angiotensin-aldosterone-system hormones and NT pro-B type natriuretic peptides were collected at each time point. RR was calculated as: (Δ arterial bicarbonate)/(Δ partial pressure of arterial carbon dioxide) between sea-level and high-altitude day1, and sea-level and high-altitude day7. The main findings were: 1) RDO2 was initially decreased at high-altitude compared to sea-level (ΔRDO2: -22±17%, P<0.001), but was restored to sea-level values on high-altitude day7 (ΔRDO2: -6±14%, P=0.36). The observed improvements in RDO2 resulted from both changes in renal blood flow (Δ from high-altitude day1: +12±11%; P=0.008), and arterial oxygen content (Δ from high-altitude day1 +44.8±17.7%; P=0.006); and 2) RR was positively correlated with RDO2 on high-altitude day7 (r=0.70; P<0.001), but not high-altitude day1 (r=0.26; P=0.29). These findings characterize the temporal responses of renal function during early high-altitude acclimatization, and the influence of RDO2 in the regulation of acid-base.

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Section: Rdo 2 and Acid-base Acclimatizationmentioning

confidence: 99%

“…The contributions of renal blood flow and CaO 2 on RDO 2 has yet to be characterized at highaltitude, and may have functional consequences on acid-base acclimatization (18,49).…”

Section: Introductionmentioning

confidence: 99%

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Global REACH 2018: renal oxygen delivery is maintained during early acclimatization to 4,330 m

Steele

Tymko

Meah

et al. 2020

American Journal of Physiology-Renal Physiology

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What factors contribute to the elevation of serum free fatty acid levels in newborns in the cardiac surgical setting?

Wittnich

Belanger

2017

Can. J. Physiol. Pharmacol.

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Elevations in serum free fatty acid (FFA) levels during heart surgery have been reported in humans and experimental animals, causing increased arrhythmias, decreased heart function, and contributing to mortality. Factors such as heparin administration, age, cardiopulmonary bypass (CPB), and cyanosis or hypoxia have been implicated but not proven. This study was designed to clarify the contribution of these factors using an experimental pig model as follows: (i) adult (n = 10) versus 3-day-old piglets (n = 18) had FFA levels assessed before and after heparin administration; (ii) 3-day-old piglets, the additional effect of CPB (n = 8) or just severe hypoxia (PaO = 20-25 mm Hg; n = 6) exposure on FFA levels. This work demonstrated that significant elevations in serum FFA were mainly due to heparin administration, with modest contributions by young age, CPB, and hypoxia. Our preliminary clinical investigations also suggest that children undergoing CPB are at risk of being exposed to high FFA levels and that these patients only suffered a decrease in heart function when these elevations were present in conjunction with cyanosis and (or) prolonged ischemic time. These initial findings require further confirmation. Given these findings, pharmacotherapeutics geared towards limiting FFA elevations should be considered, especially in young children undergoing pediatric cardiac surgery.

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Organ Blood Flow Redistribution in Response to Hypoxemia in Neonatal Piglets

Dyess

Christenberry

Peeples

et al. 1998

Journal of Investigative Surgery

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This study was designed to determine the effects of severe hypoxemia on newborn piglet visceral blood flow. While the hemodynamic effects of a severe hypoxemic insult are well characterized in newborn animals, its impact on organ perfusion in premature infants is not well characterized. Cannulas were placed in the femoral vessels and left atrium of term (1-14 days old) and prematurely delivered (cesarean section at 90% of term gestation) piglets. After stabilization, some animals were subjected to 1 h of ventilator-controlled hypoxia (yielding PaO2 approximately = 30-40 torr) followed by 30 min of reoxygenation; the remaining animals served as unchallenged controls. Radiolabeled microspheres were injected in all animals at times 0 min (baseline), 5 and 60 min (hypoxia), and 90 min (reoxygenation). Blood flows (mL/min/g tissue) to organs were determined using reference organ techniques. Control animals displayed no alterations in any of the variables monitored. Throughout the experimental period, organ blood flows were almost uniformly lower (p<.05, ANOVA) in premature versus term animals. The trend toward increased cerebral and cardiac blood flows during hypoxia observed in the premature piglets was similar to that of term animals, but of lower magnitude. In term piglets, hypoxia produced an immediate and significant (*p<.05) decline in small-intestinal blood flow followed by autoregulatory escape (2.02+/-0.17 mL/min/g at time 0, 1.56+/-0.15 mL/min/g at 5 min hypoxia, 1.88+/-0.18 mL/min/g at 60 min hypoxia, 2.26+/-0.19 mL/min/g at 30 min reoxygenation), an effect not readily observed in the premature piglets (0.48+/-0.10 mL/min/g at time 0, 0.44+/-0.07 mL/min/g at 5 min hypoxia, 0.46+/-0.10 mL/min/g at 60 min hypoxia, 0.42+/-0.08 mL/min/g at 30 min reoxygenation). However, mucosal blood flows measured in these younger animals declined throughout the experimental period to almost 50% of baseline, compared to a complete restoration to baseline blood flow observed following reoxygenation of term piglets. Intestinal blood flow in premature infants is small when compared to term animals, and alterations in small intestinal blood mucosal flow induced by hypoxia appear less well tolerated by the premature animals. Taken together, this may in part account for the increased risk of developing intestinal ischemic diseases in premature infants who are even temporarily exposed to a severe hypoxic challenge.

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Neonatal hemodynamic responses to extreme ranges of controlled graded hypoxia

Cited by 3 publications

References 30 publications

Global REACH 2018: renal oxygen delivery is maintained during early acclimatization to 4,330 m

Global REACH 2018: renal oxygen delivery is maintained during early acclimatization to 4,330 m

What factors contribute to the elevation of serum free fatty acid levels in newborns in the cardiac surgical setting?

Organ Blood Flow Redistribution in Response to Hypoxemia in Neonatal Piglets

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