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Lear CA, Georgieva A, Beacom MJ, Wassink G, Dhillon SK, Lear BA, Mills OJ, Westgate JA, Bennet L, Gunn AJ. Fetal heart rate responses in chronic hypoxaemia with superimposed repeated hypoxaemia consistent with early labour: a controlled study in fetal sheep. BJOG 2023. [PMID: 36808862 DOI: 10.1111/1471-0528.17425] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Revised: 01/30/2023] [Accepted: 02/09/2023] [Indexed: 02/20/2023]
Abstract
OBJECTIVE Deceleration area (DA) and capacity (DC) of the fetal heart rate can help predict risk of intrapartum fetal compromise. However, their predictive value in higher risk pregnancies is unclear. We investigated whether they can predict the onset of hypotension during brief hypoxaemia repeated at a rate consistent with early labour in fetal sheep with pre-existing hypoxaemia. DESIGN Prospective, controlled study. SETTING Laboratory. SAMPLE Chronically instrumented, unanaesthetised near-term fetal sheep. METHODS One-minute complete umbilical cord occlusions (UCOs) were performed every 5 minutes in fetal sheep with baseline pa O2 <17 mmHg (hypoxaemic, n = 8) and >17 mmHg (normoxic, n = 11) for 4 hours or until arterial pressure fell <20 mmHg. MAIN OUTCOME MEASURES DA, DC and arterial pressure. RESULTS Normoxic fetuses showed effective cardiovascular adaptation without hypotension and mild acidaemia (lowest arterial pressure 40.7 ± 2.8 mmHg, pH 7.35 ± 0.03). Hypoxaemic fetuses developed hypotension (lowest arterial pressure 20.8 ± 1.9 mmHg, P < 0.001) and acidaemia (final pH 7.07 ± 0.05). In hypoxaemic fetuses, decelerations showed faster falls in FHR over the first 40 seconds of UCOs but the final deceleration depth was not different to normoxic fetuses. DC was modestly higher in hypoxaemic fetuses during the penultimate (P = 0.04) and final (P = 0.012) 20 minutes of UCOs. DA was not different between groups. CONCLUSION Chronically hypoxaemic fetuses had early onset of cardiovascular compromise during labour-like brief repeated UCOs. DA was unable to identify developing hypotension in this setting, while DC only showed modest differences between groups. These findings highlight that DA and DC thresholds need to be adjusted for antenatal risk factors, potentially limiting their clinical utility.
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Affiliation(s)
- C A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - A Georgieva
- Nuffield Department of Women's and Reproductive Health, The John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - M J Beacom
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - G Wassink
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - S K Dhillon
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - B A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - O J Mills
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - J A Westgate
- Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - L Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - A J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Starship Children's Hospital, Auckland, New Zealand
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Tarvonen MJ, Lear CA, Andersson S, Gunn AJ, Teramo KA. Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies. BJOG 2022; 129:2070-2081. [PMID: 35596699 PMCID: PMC9796294 DOI: 10.1111/1471-0528.17234] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 05/02/2022] [Accepted: 05/16/2022] [Indexed: 01/01/2023]
Abstract
Increased fetal heart rate variability (FHRV) in intrapartum cardiotocographic recording has been variably defined and poorly understood, limiting its clinical utility. Both preclinical (animal) and clinical (human) evidence support that increased FHRV is observed in the early stage of intrapartum fetal hypoxaemia but can also be observed in a subset of fetuses during the preterminal stage of repeated hypoxaemia. This review of available evidence provides data and expert opinion on the pathophysiology of increased FHRV, its clinical significance and a stepwise approach regarding the management of this pattern, and propose recommendations for standardisation of related terminology.
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Affiliation(s)
- Mikko J. Tarvonen
- Department of Obstetrics and GynaecologyUniversity of Helsinki, and Helsinki University HospitalHelsinkiFinland
| | - Christopher A. Lear
- Fetal Physiology and Neuroscience GroupDepartment of PhysiologyUniversity of AucklandAucklandNew Zealand
| | - Sture Andersson
- Children’s Hospital, Paediatric Research CentreUniversity of Helsinki, and Helsinki University HospitalHelsinkiFinland
| | - Alistair J. Gunn
- Fetal Physiology and Neuroscience GroupDepartment of PhysiologyUniversity of AucklandAucklandNew Zealand
| | - Kari A. Teramo
- Department of Obstetrics and GynaecologyUniversity of Helsinki, and Helsinki University HospitalHelsinkiFinland
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Is It Time to Redefine Fetal Decelerations in Cardiotocography? J Pers Med 2022; 12:jpm12101552. [PMID: 36294689 PMCID: PMC9605652 DOI: 10.3390/jpm12101552] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/13/2022] [Accepted: 09/18/2022] [Indexed: 11/17/2022] Open
Abstract
Historically, fetal heart rate (FHR) decelerations were classified into “early”, “late”, and “variable” based on their relationship with uterine contractions. So far, three different putative etiologies were taken for granted. Recently, this belief, passed down through generations of birth attendants, has been questioned by physiologists. This narrative review aimed to assess the evidence on pathophysiology behind intrapartum FHR decelerations. This narrative review is based on information sourced from online peer-reviewed articles databases and recommendations from the major scientific societies in the field of obstetrics. Searches were performed in MEDLINE/PubMed, EMBASE, and Scopus and selection criteria included studies in animals and humans, where the physiology behind FHR decelerations was explored. The greater affinity for oxygen of fetal hemoglobin than the maternal, the unicity of fetal circulation, and the high anaerobic reserve of the myocardium, ensure adequate oxygenation to the fetus, under basal conditions. During acute hypoxic stress the efficiency of these mechanisms are increased because of the peripheral chemoreflex. This reflex, activated at each uterine contraction, is characterized by the simultaneous activation of two neural arms: the parasympathetic arm, which reduces the myocardial consumption of oxygen by decreasing the FHR and the sympathetic component, which promotes an intense peripheric vasoconstriction, thus centralizing the fetal blood volume. This review summarizes the evidence supporting the hypoxic origin of FHR decelerations, therefore archiving the historical belief that FHR decelerations have different etiologies, according to their shape and relationship with uterine contractions. The present review suggests that it is time to welcome the new scientific evidence and to update the CTG classification systems.
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Lear CA, Bennet L, Lear BA, Westgate JA, Gunn AJ. Lack of evidence for impaired preload or Bezold-Jarisch activation during brief umbilical cord occlusions in fetal sheep. Am J Physiol Regul Integr Comp Physiol 2021; 320:R532-R540. [PMID: 33533313 DOI: 10.1152/ajpregu.00357.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Impaired cardiac preload secondary to umbilical cord occlusion (UCO) has been hypothesized to contribute to intrapartum decelerations, brief falls in fetal heart rate (FHR), through activation of the Bezold-Jarisch reflex. This cardioprotective reflex increases parasympathetic and inhibits sympathetic outflows triggering hypotension, bradycardia, and peripheral vasodilation, but its potential to contribute to intrapartum decelerations has never been systematically examined. In this study, we performed bilateral cervical vagotomy to remove the afferent arm and the efferent parasympathetic arm of the Bezold-Jarisch reflex. Twenty-two chronically instrumented fetal sheep at 0.85 of gestation received vagotomy (n = 7) or sham vagotomy (control, n = 15), followed by three 1-min complete UCOs separated by 4-min reperfusion periods. UCOs in control fetuses were associated with a rapid fall in FHR and reduced femoral blood flow mediated by intense femoral vasoconstriction, leading to hypertension. Vagotomy abolished the rapid fall in FHR (P < 0.001) and, despite reduced diastolic filling time, increased both carotid (P < 0.001) and femoral (P < 0.05) blood flow during UCOs, secondary to carotid vasodilation (P < 0.01) and delayed femoral vasoconstriction (P < 0.05). Finally, vagotomy was associated with an attenuated rise in cortical impedance during UCOs (P < 0.05), consistent with improved cerebral substrate supply. In conclusion, increased carotid and femoral blood flows after vagotomy are consistent with increased left and right ventricular output, which is incompatible with the hypothesis that labor-like UCOs impair ventricular filling. Overall, the cardiovascular responses to vagotomy do not support the hypothesis that the Bezold-Jarisch reflex is activated by UCO. The Bezold-Jarisch reflex is therefore mechanistically unable to contribute to intrapartum decelerations.
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Affiliation(s)
- Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Benjamin A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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Georgieva A, Lear CA, Westgate JA, Kasai M, Miyagi E, Ikeda T, Gunn AJ, Bennet L. Deceleration area and capacity during labour-like umbilical cord occlusions identify evolving hypotension: a controlled study in fetal sheep. BJOG 2021; 128:1433-1442. [PMID: 33369871 DOI: 10.1111/1471-0528.16638] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2020] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Cardiotocography is widely used to assess fetal well-being during labour. The positive predictive value of current clinical algorithms to identify hypoxia-ischaemia is poor. In experimental studies, fetal hypotension is the strongest predictor of hypoxic-ischaemic injury. Cohort studies suggest that deceleration area and deceleration capacity of the fetal heart rate trace correlate with fetal acidaemia, but it is not known whether they are indices of fetal arterial hypotension. DESIGN Prospective, controlled study. SETTING Laboratory. SAMPLE Near-term fetal sheep. METHODS One minute of complete umbilical cord occlusions (UCOs) every 5 minutes (1:5 min, n = 6) or every 2.5 minutes (1:2.5 min, n = 12) for 4 hours or until fetal mean arterial blood pressure fell <20 mmHg. MAIN OUTCOME MEASURES Deceleration area and capacity during the UCO series were related to evolving hypotension. RESULTS The 1:5 min group developed only mild metabolic acidaemia, without hypotension. By contrast, 10/12 fetuses in the 1:2.5-min group progressively developed severe metabolic acidaemia and hypotension, reaching 16.8 ± 0.9 mmHg after 71.2 ± 6.7 UCOs. Deceleration area and capacity remained unchanged throughout the UCO series in the 1:5-min group, but progressively increased in the 1:2.5-min group. The severity of hypotension was closely correlated with both deceleration area (P < 0.001, R2 = 0.66, n = 18) and capacity (P < 0.001, R2 = 0.67, n = 18). Deceleration area and capacity predicted development of hypotension at a median of 103 and 123 minutes before the final occlusion, respectively. CONCLUSIONS Both deceleration area and capacity were strongly associated with developing fetal hypotension, supporting their potential to improve identification of fetuses at risk of hypotension leading to hypoxic-ischaemic injury during labour. TWEETABLE ABSTRACT Deceleration area and capacity of fetal heart rate identify developing hypotension during labour-like hypoxia.
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Affiliation(s)
- A Georgieva
- Nuffield Department of Women's and Reproductive Health, The John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - C A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - J A Westgate
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - M Kasai
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,The Department of Obstetrics and Gynecology, Yokohama City University, Yokohama, Japan
| | - E Miyagi
- The Department of Obstetrics and Gynecology, Yokohama City University, Yokohama, Japan
| | - T Ikeda
- Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - A J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - L Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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Eden RD, Evans MI, Britt DW, Evans SM, Schifrin BS. Safely lowering the emergency Cesarean and operative vaginal delivery rates using the Fetal Reserve Index. J Matern Fetal Neonatal Med 2018; 33:1473-1479. [PMID: 30269624 DOI: 10.1080/14767058.2018.1519799] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Objective: The cardiotocograph (CTG) or electronic fetal monitoring (EFM) was developed to prevent fetal asphyxia and subsequent neurological injury. From a public health perspective, it has failed these objectives while increasing emergency operative deliveries (emergency operative deliveries (EODs) - emergency cesarean delivery or operative vaginal delivery) for newborns, who in retrospect, actually did not require the assistance. EODs increase the risks of complications and stress for patients, families, and medical personnel. A safe reduction in the need for EOD will likely reduce both the overall Cesarean section rate as well as the risk of fetal neurological injury during labor to which it is related. We have developed the fetal reserve index (FRI), which is more comprehensive than CTG as a new screening method for early identification of the fetus at-risk of both neurological harm and the need to "rescue" by means of an EOD. Here, we compare prospectively the need for EOD in two groups of parturients undergoing a trial of labor at term. One group was managed conventionally, the other by the principles of the FRI.Study design: We compared the need for EOD of 800 parturients with singleton cases undergoing a trial of labor at term entering with normal CTG patterns (ACOG category 1). Patients were either treated routinely (400 - "early cases") or in a second group seen later actively managed using the principles of the FRI (400 - "late cases"). The FRI includes measurements of five components of the CTG: rate, variability, decelerations, accelerations, and abnormal uterine activity combined with the presence of medical, obstetrical, and fetal risk factors. The 8-point metric categorizes cases as "green", "yellow", and "red" with the latter being at risk.Results: All 800 patients delivered babies, who were discharged in the usual time course with no untoward outcomes noted. The incidence of red zone scores was comparable in the two groups (≈25%), but the use of intrauterine resuscitation (IR) when reaching the red zone in the late group (47%) was more than double the incidence in the early group (20%) (p < .001). Despite (or because of) this, EODs were significantly reduced in the late group, from 17.3 to 4.0% (p < .001). Further, the late group spent less time in the red zone without increasing overall time in labor. Overall, EOD cases averaged >1 h in the red zone versus 0.5 h for non-EODs.Conclusions: The FRI may provide a metric to reduce EODs and by extension also reduce the risks of both cesarean delivery and adverse fetal/neonatal outcomes. The safe avoidance of EOD would seem to be an important metric to assess the quality of intrapartum management. This study represents the first attempt to apply the principles of the FRI "live" for the concurrent management of patients during labor. These promising results, if confirmed, in larger sample sizes, set the stage for our computerization of the FRI for widespread study. Benefits appear to come from identification and early, conservative management of fetal deterioration before the need to "rescue" the fetus by EOD.
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Affiliation(s)
- Robert D Eden
- Fetal Medicine Foundation of America, New York, NY, USA
| | - Mark I Evans
- Fetal Medicine Foundation of America, New York, NY, USA.,Comprehensive Genetics, PLLC, New York, NY, USA.,Department of Obstetrics and Gynecology, Mt. Sinai School of Medicine, New York, NY, USA
| | - David W Britt
- Fetal Medicine Foundation of America, New York, NY, USA
| | - Shara M Evans
- Fetal Medicine Foundation of America, New York, NY, USA
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Sholapurkar SL. International consensus on intrapartum cardiotocography should be underpinned by sound scientific foundation. J Matern Fetal Neonatal Med 2016; 30:2340-2341. [PMID: 27756167 DOI: 10.1080/14767058.2016.1247801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Shashikant L Sholapurkar
- a Department of Obstetrics and Gynaecology , Royal United Hospital Bath NHS Foundation Trust , Bath , UK
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