Is fetal analgesia necessary during prenatal surgery?

Congenital diaphragmatic hernia treated via fetal endoscopic tracheal occlusion improves outcome in a middle-income country

OBJECTIVES

A recent European randomized trial - Tracheal Occlusion To Accelerate Lung Growth - demonstrated that fetoscopic endoluminal tracheal occlusion (FETO) is associated with increased postnatal survival among infants with severe congenital diaphragmatic hernia (CDH). However, this differs in middle-income countries such as Brazil, where abortion is illegal and neonatal intensive care is inadequate. This study evaluated the effects of FETO on improving the survival of infants with moderate-to-severe CDH in isolated and non-isolated cases.

METHODS

This retrospective cohort study selected 49 fetuses with CDH, a normal karyotype, and a lung-to-head ratio (LHR) of <1 from a single national referral center for fetal surgery in São Paulo, Brazil, between January 2016 and November 2019. FETO was performed between 26 and 29 weeks of gestation. The primary outcomes were infant survival until discharge from the neonatal intensive care unit and survival until six months of age.

RESULTS

Forty-six women with singleton fetuses having severe CDH underwent prenatal intervention with FETO. Infant survival rates until discharge and at six months of age were both 38 %. The observed-to-expected LHR increased by 25 % after FETO in neonates who survived until discharge. Spontaneous intrauterine death occurred in four growth-restricted fetuses after FETO. Preterm birth in <37 weeks and preterm rupture of membranes in <34 weeks occurred in 56.5 % (26) and 26 % (12) cases, respectively.

CONCLUSIONS

FETO may increase neonatal survival in fetuses with severe CDH, particularly in countries with limited neonatal intensive care.

Assessment of Human Fetuses Undergoing Acute Pain: Validation of the Fetal-7 Scale

Improvements in fetal ultrasound have allowed for the diagnosis and treatment of fetal diseases in the uterus, often through surgery. However, little attention has been drawn to the assessment of fetal pain. To address this gap, a fetal pain scoring system, known as the Fetal-7 scale, was developed. The present study is a full validation of the Fetal-7 scale. The validation involved 2 steps: 1) 4 fetuses with the indication of surgery were evaluated in 3 conditions perioperatively: acute pain, rest, and under loud sound stimulation. Facial expressions were assessed by 30 raters using screenshots from 4D high-definition ultrasound films; 2) assessment of sensitivity and specificity of the Fetal-7 scale in 54 healthy fetuses and 2 fetuses undergoing acute pain after preoperative anesthetic intramuscular injection. There was high internal consistency with Cronbach's alpha (α) of .99. Intrarater reliability of the Fetal-7 scale (test-retest) calculated by intraclass correlation coefficient was .95, and inter-rater reliability was .99. The scale accurately differentiated between healthy fetuses at rest and those experiencing acute pain (sensitivity of 100% and specificity of 94.4%). The Fetal-7 scale is a valid tool for assessing acute pain-related behavior in third-trimester fetuses and may be of value in guiding analgesic procedures efficacy in these patients. Further research is warranted to explore the presence of postoperative pain in fetuses and its effects after birth. PERSPECTIVE: Recordings with 3-dimensional ultrasound of human fetuses undergoing preoperative anesthetic injections revealed complex facial expressions during acute pain, similar to those collected in newborns. This study presented the validation process and cut-off value of the Fetal-7 scale, paving the way for the study of pain before birth in humans.

An Evidence-Based Discussion of Fetal Pain and Stress

BACKGROUND

The concept of fetal pain results from procedures conducted without anesthesia in preterm newborns and fetuses, which indicate that it is possible to examine fetal pain based on stress hormone, metabolic, and behavioral changes. Anatomical and physiological data suggest that fetuses become capable of processing nociceptive stimuli around midgestation, although the associated changes in fetal brain development remain unclear. What constitutes fetal pain remains controversial in the light of the definition of pain adopted by the International Association for the Study of Pain (IASP), which posits pain as an "unpleasant sensory and emotional experience."

SUMMARY

Here, we examine the notion that human fetuses cannot "experience" pain and potential implications of this claim. We highlight the key scientific evidence related to fetal pain, including clinical studies on pain in fetuses and preterm newborns. We argue that consistent patterns of stress hormones, metabolic changes, body movements, hemodynamic changes, and pain-related facial expressions in fetuses exposed to invasive procedures overcome the need for subjective proof of pain as articulated in the IASP definition. No study to date has conclusively proven the absence of fetal pain beyond the age of viability.

KEY MESSAGES

Based on the current evidence, we propose that all fetuses receive anesthesia regardless of the invasive procedures being performed to guarantee the least possible pain and physiological, behavioral, or hormonal responses without exposing the mother or her baby to unnecessary complications.

Difficulties in Adaptation of the Mother and Newborn via Cesarean Section versus Natural Birth-A Narrative Review

Birth is a physiological act that is part of the morpho-functional economy of the maternal body. Each stage in the act of birth has a predetermined pathway that is neurohormonally induced and morpho-functionally established through specific and characteristic adaptations. Like maternity, childbirth also has an important impact on the maternal body as a biological structure and psycho-emotional behavior. Cesarean section performed at the request of the mother with no medical underlying conditions besides the prolonged hospitalization risk can also cause breathing problems in children, delayed breastfeeding, and possible complications in a future pregnancy. Vaginal birth remains the path of choice for a physiological evolution pregnancy. Although erroneously considered safe and easy today, cesarean section delivery must remain an emergency procedure or a procedure recommended for pregnancies where birth is a risk to the mother and to the child, as cesarean section itself is a risk factor for negative outcomes for both mother and baby. This review summarizes the impact that both cesarean section and natural birth have on mother and newborn in their attempt to adapt to postpartum events and extrauterine life.

The fetal pain paradox

Controversy exists as to when conscious pain perception in the fetus may begin. According to the hypothesis of cortical necessity, thalamocortical connections, which do not form until after 24-28 weeks gestation, are necessary for conscious pain perception. However, anesthesiologists and neonatologists treat age-matched neonates as both conscious and pain-capable due to observable and measurable behavioral, hormonal, and physiologic indicators of pain. In preterm infants, these multimodal indicators of pain are uncontroversial, and their presence, despite occurring prior to functional thalamocortical connections, has guided the use of analgesics in neonatology and fetal surgery for decades. However, some medical groups state that below 24 weeks gestation, there is no pain capacity. Thus, a paradox exists in the disparate acknowledgment of pain capability in overlapping patient populations. Brain networks vary by age. During the first and second trimesters, the cortical subplate, a unique structure that is present only during fetal and early neonatal development, forms the first cortical network. In the third trimester, the cortical plate assumes this function. According to the subplate modulation hypothesis, a network of connections to the subplate and subcortical structures is sufficient to facilitate conscious pain perception in the fetus and the preterm neonate prior to 24 weeks gestation. Therefore, similar to other fetal and neonatal systems that have a transitional phase (i.e., circulatory system), there is now strong evidence for transitional developmental phases of fetal and neonatal pain circuitry.

Anesthesia for fetal operative procedures: A systematic review

Objective

The anesthetic management of fetal operative procedures (FOP) is a highly debated topic. Literature on fetal pain perception and response to external stimuli is rapidly expanding. Nonetheless, there is no consensus on the fetal consciousness nor on the instruments to measure pain levels. As a result, no guidelines or clinical recommendations on anesthesia modality during FOP are available. This systematic literature review aimed to collect the available knowledge on the most common fetal interventions, and summarize the reported outcomes for each anesthetic approach. Additional aim was to provide an overall evaluation of the most commonly used anesthetic agents.

Methods

Two systematic literature searches were performed in Embase, Medline, Web of Science Core Collection and Cochrane Central Register of Controlled Trials up to December 2021. To best cover the available evidence, one literature search was mostly focused on fetal surgical procedures; while anesthesia during FOP was the main target for the second search. The following fetal procedures were included: fetal transfusion, laser ablation of placental anastomosis, twin-reversed arterial perfusion treatment, fetoscopic endoluminal tracheal occlusion, thoraco-amniotic shunt, vesico-amniotic shunt, myelomeningocele repair, resection of sacrococcygeal teratoma, ligation of amniotic bands, balloon valvuloplasty/septoplasty, ex-utero intrapartum treatment, and ovarian cyst resection/aspiration. Yielded articles were screened against the same inclusion criteria. Studies reporting anesthesia details and procedures’ outcomes were considered. Descriptive statistical analysis was performed and findings were reported in a narrative manner.

Results

The literature searches yielded 1,679 articles, with 429 being selected for full-text evaluation. A total of 168 articles were included. Overall, no significant differences were found among procedures performed under maternal anesthesia or maternal-fetal anesthesia. Procedures requiring invasive fetal manipulation resulted to be more effective when performed under maternal anesthesia only. Based on the available data, a wide range of anesthetic agents are currently deployed and no consistency has been found neither between centers nor procedures.

Conclusions

This systematic review shows great variance in the anesthetic management during FOP. Further studies, systematically reporting intraoperative fetal monitoring and fetal hormonal responses to external stimuli, are necessary to identify the best anesthetic approach. Additional investigations on pain pathways and fetal pain perception are advisable.

Fetal Pain in the First Trimester

Fetal pain perception has important implications for fetal surgery, as well as for abortion. Current neuroscientific evidence indicates the possibility of fetal pain perception during the first trimester (<14 weeks gestation). Evidence for this conclusion is based on the following findings: (1) the neural pathways for pain perception via the cortical subplate are present as early as 12 weeks gestation, and via the thalamus as early as 7–8 weeks gestation; (2) the cortex is not necessary for pain to be experienced; (3) consciousness is mediated by subcortical structures, such as the thalamus and brainstem, which begin to develop during the first trimester; (4) the neurochemicals in utero do not cause fetal unconsciousness; and (5) the use of fetal analgesia suppresses the hormonal, physiologic, and behavioral responses to pain, avoiding the potential for both short- and long-term sequelae. As the medical evidence has shifted in acknowledging fetal pain perception prior to viability, there has been a gradual change in the fetal pain debate, from disputing the existence of fetal pain to debating the significance of fetal pain. The presence of fetal pain creates tension in the practice of medicine with respect to beneficence and nonmaleficence.

Analgesia for fetal pain during prenatal surgery: 10 years of progress

Some doubts on the necessity and safety of providing analgesia to the fetus during prenatal surgery were raised 10 years ago. They were related to four matters: fetal sleep due to neuroinhibitors in fetal blood, the immaturity of the cerebral cortex, safety, and the need for fetal direct analgesia. These objections now seem obsolete. This review shows that neuroinhibitors give fetuses at most some transient sedation, but not a complete analgesia, that the cerebral cortex is not indispensable to feel pain, when subcortical structures for pain perception are present, and that maternal anesthesia seems not sufficient to anesthetize the fetus. Current drugs used for maternal analgesia pass through the placenta only partially so that they cannot guarantee a sufficient analgesia to the fetus. Extraction indices, that is, how much each analgesic drug crosses the placenta, are provided here. We here report safety guidelines for fetal direct analgesia. In conclusion, the human fetus can feel pain when it undergoes surgical interventions and direct analgesia must be provided to it. IMPACT: Fetal pain is evident in the second half of pregnancy. Progress in the physiology of fetal pain, which is reviewed in this report, supports the notion that the fetus reacts to painful interventions during fetal surgery. Evidence here reported shows that it is an error to believe that the fetus is in a continuous and unchanging state of sedation and analgesia. Data are given that disclose that drugs used for maternal analgesia cross the placenta only partially, so that they cannot guarantee a sufficient analgesia to the fetus. Safety guidelines are given for fetal direct analgesia.

Fetal Pain: The Science Behind Why It Is the Medical Standard of Care

Despite pain as the fifth vital sign in adult and pediatric care, many still dismiss the fact that immature human beings (whether a fetus, a preterm, or term baby) are capable of being affected by pain. Studies have demonstrated that avoiding, minimizing, and treating pain in babies, particularly when premature, improves their outcomes. Informed by the evidence, treating neonatal pain has become the medical standard of care for physicians in neonatology and anesthesiology. This article provides a brief overview of relevant publications that explain the clinical evolution that has led to the treatment of neonatal pain. This article also examines three arguments against the existence of fetal pain and presents evidence that refutes them. Informed by the research, a revised definition of pain is offered.

[Feticide procedures in second and third trimesters terminations of pregnancy]

Performing a feticide as part of termination of late pregnancy is recommended in many countries. Feticide avoids a live birth of a severely affected premature newborn and prevents fetal pain. There are limited data on feticide procedures since only a few countries in the world authorize late termination of pregnancy. The objective of this review was to assess the most appropriate feticide procedure based on published data during the last thirty years. Administration of an initial fetal analgesia followed by a lethal lidocaine injection through the umbilical cord, under ultrasound guidance, appears to be the most effective, safe and ethical way to perform feticide. According to the current knowledge regarding the risk of fetal pain and survival of extremely preterm infants, a feticide should be discussed as early as 20-22 weeks of gestation.

New insights into fetal pain

Fetal pain is difficult to assess, because the main feature needed to spot pain, is the subject's capability of declaring it. Nonetheless, much can be affirmed about this issue. In this review we first report the epochs of the development of human nociceptive pathways; then we review since when they are functioning. We also review the latest data about the new topic of analgesia and prenatal surgery and about the scarce effect on fetal pain sentience of the natural sedatives fetuses produce. It appears that pain is a neuroadaptive phenomenon that emerges in the middle of pregnancy, at about 20-22 weeks of gestation, and becomes more and more evident for bystanders and significant for the fetus, throughout the rest of the pregnancy.