Reply from Christopher A. Lear, Robert Galinsky, Guido Wassink, Kyohei Yamaguchi, Joanne O. Davidson, Jenny A. Westgate, Laura Bennet and Alistair J. Gunn

Lear, Christopher A.; Galinsky, Robert; Wassink, Guido; Yamaguchi, Kyohei; Davidson, J.; Westgate, Jenny A.; Gunn, Alistair J.

doi:10.1113/jp274800

Cited by 4 publications

(11 citation statements)

References 16 publications

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“…They theorize that cord occlusion is likely the cause of many variable FHR decelerations in the first stage of active labor, and that head compression is responsible for decelerations in the second stage of labor [ 31 ]. However, Lear et al concluded that fetal head compression was unlikely to be a major contributor to intrapartum decelerations during the majority of labors [ 3 , 33 ]. However, as described by Parer and Lear, vagal reflex is involved in FHR deceleration whatever the etiology (umbilical cord compression or head compression or both) [ 32 , 33 ].…”

Section: Discussionmentioning

confidence: 99%

“…However, Lear et al concluded that fetal head compression was unlikely to be a major contributor to intrapartum decelerations during the majority of labors [ 3 , 33 ]. However, as described by Parer and Lear, vagal reflex is involved in FHR deceleration whatever the etiology (umbilical cord compression or head compression or both) [ 32 , 33 ]. Understanding the nature of the reflexes involved in deceleration may help us understand what causes changes in fetal homeostasis and the response of the fetus.…”

Section: Discussionmentioning

confidence: 99%

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Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep

et al. 2021

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Fetal heart rate (FHR) deceleration is the most common change seen during labor. The role of the autonomic nervous system in regulating the fetal cardiovascular response during multiple uterine contractions has been well-established. However, the mechanism underlying the hemodynamic response remains unclear and the specific reflex that mediates the cardiovascular modifications is still controversial. This study aimed to determine the role of the sympathetic and parasympathetic systems on fetal hemodynamics in complete cord occlusion. Chronically instrumented fetal sheep were randomized to receive an intravenous injection of atropine 2.5 mg (n = 8), propranolol 5 mg (n = 7), atropine and propranolol (n = 7), or a control protocol (n = 9), followed by three episodes of 1-minute umbilical cord occlusion repeated every 5 minutes. Cord compression induces a rapid decrease in the FHR and a rapid increase in MAP. The decrease in FHR is caused by an increase in parasympathetic activity, (atropine and atropine-propranolol abolish the FHR response to the occlusion). The change in FHR during occlusion was not modified by propranolol injection, showing no effect of sympathetic tone. The increase in MAP during occlusion was similar in the four protocols. After releasing occlusion, the FHR was still lower than that at baseline due to a sustained parasympathetic tone. Suppression of the parasympathetic output to the cardiovascular system unmasks an increase in the FHR above baseline values. The lower FHR with the propranolol protocol further supports an increase in myocardial β-adrenoceptor stimulation after cord release. The increase in MAP after cord release was similar in the four protocols, except after the early stage of interocclusion period in atropine protocol. Four minutes after cord release, the FHR returned to baseline irrespective of the drugs that were infused, thereby showing recovery of ANS control. Blood gases (pH, PaCO2, PaO2) and plasma lactate concentrations was similar between the four protocols at the end of three applications of UCO. Complete cord compression-induced deceleration is likely due to acute activation of parasympathetic output. β-adrenoceptor activity is involved in the increase in FHR after cord release. Understanding the reflexes involved in FHR deceleration may help us understand the mechanisms underlying fetal autonomic adaptation during cord occlusion.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep

et al. 2021

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“…This is also supported by many animal experiments showing that the decelerations start to recover only after relief of cord-occlusion [ 18 , 20 ]. Singular select animal experiment showing partial recovery of FHR during prolonged complete cord-occlusion (confirmation bias) [ 21 ] cannot explain the consistent recovery of most decelerations corresponding to the peak of contractions and cannot be extrapolated to human labor. These most common decelerations ( Fig.…”

Section: Etiological Versus Pathophysiological Categorization Of Fhr mentioning

confidence: 99%

Obstetrics at Decisive Crossroads Regarding Pattern-Recognition of Fetal Heart Rate Decelerations: Scientific Principles and Lessons From Memetics

Sholapurkar

2018

J Clin Med Res

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The survival of cardiotocography (CTG) as a tool for intrapartum fetal monitoring seems threatened somewhat unjustifiably and unwittingly despite the absence of better alternatives. Fetal heart rate (FHR) decelerations are center-stage (most important) in the interpretation of CTG with maximum impact on three-tier classification. The pattern-discrimination of FHR decelerations is inexorably linked to their nomenclature. Unscientific or flawed nomenclature of decelerations can explain the dysfunctional CTG interpretation leading to errors in detection of acidemic fetuses. There are three contrasting concepts about categorization of FHR decelerations: 1) all rapid decelerations (the vast majority) should be grouped as “variable” because they are predominantly due to cord-compression, 2) all decelerations are due to chemoreflex from fetal hypoxemia hence their timing is not important, and 3) FHR decelerations should be categorized into “early/late/variable” based primarily on their time relationship to contractions. These theoretical concepts are like memes (ideas/beliefs). Lessons from “memetics” are that the most popular, attractive or established beliefs may not necessarily be true, scientific, beneficial or even without harm. Decelerations coincident with contractions with trough corresponding to the peak of contractions cannot be explained by cord-compression or increasing hypoxia (from compromised uteroplacental perfusion, cord-compression or even cerebral hypoperfusion/anoxia purportedly conceivable from head-compression). Decelerations due to hypoxemia would be associated with delayed recovery of decelerations (lag phase). It is a scientific imperative to cast away disproven/falsified theories. Practices based on unscientific theories lead to patient harm. Clinicians should urgently adopt the categorization of FHR decelerations based primarily of the time relationship to contractions as originally proposed by Hon and Caldeyro-Barcia. This analytical review shows it to be underpinned by most robust physiological and scientific hypotheses unlike the other categorizations associated with untruthful hypotheses, irreconcilable fallacies and contradictions. Without truthful framework and meaningful pattern-recognition of FHR decelerations, the CTG will not fulfil its true potential.

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“…In that case, the use of a solvent that was aqueous in character was found to be positive. The topology of site isolation is important in the patents, [26] and the presence of EO in a fraction of the polymer (i.e., a reduction of the amount of PO) was also claimed to be positive to avoid the formation of high-weight tails. The nature of the tails, either hydrophobic or hydrophilic, also had a role.…”

Section: Routes To Deactivation: Origins Of the Formation Of Highweigmentioning

confidence: 99%

“…The nature of the tails, either hydrophobic or hydrophilic, also had a role. [26] The formation of such tails might have two explanations with a covalent (bonding) origin: 1) presence of multiple active sites and 2) the ramification of the polymer by following the paths described in the previous section. Given the nature of the Zn active sites in the (1 0 0) surface, we have identified two potential routes that can alter the behavior described for normal polymer growth.…”

Section: Routes To Deactivation: Origins Of the Formation Of Highweigmentioning

confidence: 99%

Structure, Activity, and Deactivation Mechanisms in Double Metal Cyanide Catalysts for the Production of Polyols

et al. 2015

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Polyether polyols are used widely in the plastic and coating industries in the form of polyurethanes. The polymerization of epoxides can be catalyzed by double metal cyanides (DMCs), Zn3[Co(CN)6]2. These catalysts were first reported in the 1960s by General Tire Inc. and provide products with excellent technical features, which are better than those that result from traditional alkaline polymerization as side reactions are alleviated. However, DMC‐catalyzed polymerization is not free of drawbacks as high‐molecular‐weight side products (1–3 wt %) can form in the propylene process. These tails are detrimental to the subsequent use of these polymers, in particular to foam stability. Despite the wide industrial interest in DMCs, there are only a few experimental studies and a complete lack of theoretical research of their structure, activity, and performance. The present work is thus the first attempt to describe the nature of the active site, the main polymerization mechanism, and two potential origins for the high‐weight tails from a theoretical standpoint by analyzing three crucial steps in the polymerization process.

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Reply from Christopher A. Lear, Robert Galinsky, Guido Wassink, Kyohei Yamaguchi, Joanne O. Davidson, Jenny A. Westgate, Laura Bennet and Alistair J. Gunn

Cited by 4 publications

References 16 publications

Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep

Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep

Obstetrics at Decisive Crossroads Regarding Pattern-Recognition of Fetal Heart Rate Decelerations: Scientific Principles and Lessons From Memetics

Structure, Activity, and Deactivation Mechanisms in Double Metal Cyanide Catalysts for the Production of Polyols

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