Accelerated acidosis in response to variable fetal heart rate decelerations in chronically hypoxic ovine fetuses

Amaya, Kevin; Matushewski, Brad; Durosier, Lucien Daniel; Frasch, Martin G.; Richardson, Bryan; Ross, Michael G.

doi:10.1016/j.ajog.2015.09.084

Cited by 19 publications

(28 citation statements)

References 24 publications

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“…; Amaya et al . ). There is additional need to better understand the implications of further factors, including antenatal glucocorticoid treatment and gestational age.…”

Section: Introductionmentioning

confidence: 97%

The peripheral chemoreflex: indefatigable guardian of fetal physiological adaptation to labour

Lear

Wassink

Westgate

et al. 2018

The Journal of Physiology

108

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The fetus is consistently exposed to repeated periods of impaired oxygen (hypoxaemia) and nutrient supply in labour. This is balanced by the healthy fetus's remarkable anaerobic tolerance and impressive ability to mount protective adaptations to hypoxaemia. The most important mediator of fetal adaptations to brief repeated hypoxaemia is the peripheral chemoreflex, a rapid reflex response to acute falls in arterial oxygen tension. The overwhelming majority of fetuses are able to respond to repeated uterine contractions without developing hypotension or hypoxic-ischaemic injury. In contrast, fetuses who are either exposed to severe hypoxaemia, for example during uterine hyperstimulation, or enter labour with reduced anaerobic reserve (e.g. as shown by severe fetal growth restriction) are at increased risk of developing intermittent hypotension and cerebral hypoperfusion. It is remarkable to note that when fetuses develop hypotension during such repeated severe hypoxaemia, it is not mediated by impaired reflex adaptation, but by failure to maintain combined ventricular output, likely due to a combination of exhaustion of myocardial glycogen and evolving myocardial injury. The chemoreflex is suppressed by relatively long periods of severe hypoxaemia of 1.5-2 min, longer than the typical contraction. Even in this setting, the peripheral chemoreflex is consistently reactivated between contractions. These findings demonstrate that the peripheral chemoreflex is an indefatigable guardian of fetal adaptation to labour.

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“…; Amaya et al . ). There is additional need to better understand the implications of further factors, including antenatal glucocorticoid treatment and gestational age.…”

Section: Introductionmentioning

confidence: 97%

The peripheral chemoreflex: indefatigable guardian of fetal physiological adaptation to labour

Lear

Wassink

Westgate

et al. 2018

The Journal of Physiology

108

View full text Add to dashboard Cite

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“…The aim of fetal monitoring during labor is to detect fetuses at risk of developing respiratory and metabolic acidosis, which could result in brain lesions or even perpartum death [ 21 , 22 ]. This monitoring is based primarily on the continuous recording of the FHR, which does not, however, allow a perfect evaluation of oxygenation of the fetus and whose limits of interpretation are well known.…”

Section: Discussionmentioning

confidence: 99%

Correlation of a new index reflecting the fluctuation of parasympathetic tone and fetal acidosis in an experimental study in a sheep model

et al. 2018

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The autonomic nervous system plays a leading role in the control of fetal homeostasis. Fetal heart rate variability (HRV) analysis is a reflection of its activity. We developed a new index (the Fetal Stress Index, FSI) reflecting parasympathetic tone. The objective of this study was to evaluate this index as a predictor of fetal acid-base status. This was an experimental study on chronically instrumented fetal lambs (n = 11, surgery at 128 +/- 2 days gestational age, term = 145 days). The model was based on 75% occlusion of the umbilical cord for a maximum of 120 minutes or until an arterial pH ≤ 7.20 was reached. Hemodynamic, gasometric and FSI parameters were recorded throughout the experimentation. We studied the FSI during the 10 minutes prior to pH samplings and compared values for pH>7.20 and pH≤ 7.20. In order to analyze the FSI evolution during the 10 minutes periods, we analyzed the minimum, maximum and mean values of the FSI (respectively FSImin, FSImax and FSImean) over the periods. 11 experimentations were performed. During occlusion, the heart rate dropped with an increase in blood pressure (respectively 160(155–182) vs 106(101–120) bpm and 42(41–45) vs 58(55–62) mmHg after occlusion). The FSImin was 38.6 (35.2–43.3) in the group pH>7.20 and was higher in the group pH less than 7.20 (46.5 (43.3–52.0), p = 0.012). The correlation of FSImin was significant for arterial pH (coefficient of -0.671; p = 0.004) and for base excess (coefficient of -0.632; p = 0.009). The correlations were not significant for the other parameters. In conclusion, our new index seems well correlated with the fetal acid-base status. Other studies must be carried out in a situation close to the physiology of labor by sequential occlusion of the cord.

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“…We noted that in the last hour of labor, compared to AGA, the SGA fetuses were significantly less likely to have accelerations and more likely to have variable decelerations lasting more than 60 seconds. Previous investigators have also noted that SGA newborns are less likely to have accelerations (6,8), purportedly because hypoxia alters the maturation of both the parasympathetic and sympathetic nervous systems (9,10). Variable decelerations were also more common among SGA than AGA fetuses, which may be secondary to oligohydramnios (4).…”

Section: Discussionmentioning

confidence: 99%

“…Despite the acknowledged association between growth restriction and abnormal FHR patterns (3,4,10–12), most SGA fetuses with non-reassuring patterns do not have neonatal acidemia or adverse perinatal outcomes (6,7). The lack of sensitivity for intrapartum monitoring to identify newborns with morbidity may be related to inherent limitations of FHR tracing (13–17).…”

Section: Introductionmentioning

confidence: 99%

Intrapartum Fetal Heart Rate Tracing Among Small-for-Gestational Age Compared With Appropriate-for-Gestational-Age Neonates

Chauhan

Weiner

Saade

et al. 2018

Obstetrics &Amp; Gynecology

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Objective: To compare fetal heart rate (FHR) patterns during the last hour of labor between small- (SGA; birthweight <10th percentile for GA) and appropriate-for-gestational-age (AGA; birthweight at 10–90th percentile) neonates at ≥36 weeks of gestation. We also compared the rate of cesarean delivery and composite neonatal morbidity among SGA and AGA newborns. Methods: This is a secondary analysis of a randomized trial of intrapartum fetal ECG ST-segment analysis. We excluded women with chorioamnionitis, insufficient duration of FHR tracing in the hour before delivery, and anomalous newborns. Fetal heart rate patterns were categorized by computerized pattern recognition software (PeriCALM Patterns). Composite neonatal morbidity was defined as any of the following: intrapartum fetal death, Apgar score ≤3 at 5 minutes, cord artery pH ≤7.05 and base deficit ≥12 mmol/L, neonatal seizure, intubation at delivery, neonatal encephalopathy, neonatal death. Logistic regression was used to evaluate the association between FHR patterns and SGA adjusted for magnesium sulfate exposure and stage of labor. Results: Of the 11,108 women randomized, 85% (n=9,402) met inclusion criteria, of whom 9% were SGA. In the last hour, the likelihood of accelerations was significantly lower among SGA than AGA neonates (72.4% vs. 66.8%; P=0.001). Variable decelerations lasting >60 seconds, with depth >60 bpm or nadir <60 bpm were significantly more common with SGA than AGA (all P<0.001). The rate of late decelerations, prolonged decelerations, or bradycardia were similar between SGA and AGA (all P>0.05). Cesarean delivery for fetal indications was significantly more common with SGA (7.0%) than AGA (4.0%; P<0.001). The composite neonatal morbidity was 1.4% among SGA and 1.0% among AGA (OR 1.40; 95% CI 0.74, 2.64). Conclusions: Although the FHR patterns in the last hour of labor differ among SGA and AGA infants, as does the rate of cesarean delivery, the composite neonatal morbidity was similar.

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Accelerated acidosis in response to variable fetal heart rate decelerations in chronically hypoxic ovine fetuses

Cited by 19 publications

References 24 publications

The peripheral chemoreflex: indefatigable guardian of fetal physiological adaptation to labour

The peripheral chemoreflex: indefatigable guardian of fetal physiological adaptation to labour

Correlation of a new index reflecting the fluctuation of parasympathetic tone and fetal acidosis in an experimental study in a sheep model

Intrapartum Fetal Heart Rate Tracing Among Small-for-Gestational Age Compared With Appropriate-for-Gestational-Age Neonates

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