Advances in Foetal Anaesthesia

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Metadata

Author: sciencedirect.com
Full Title: Advances in Foetal Anaesthesia
Category: #articles
Document Tags: obstetrics paed
Summary: Research on foetal anaesthesia explores the use of different techniques during surgery to ensure the well-being of both the mother and the unborn child. Administration of anaesthesia aims to prevent pain, provide immobilization, and optimize surgical conditions. However, the impact of prenatal anaesthesia exposure on foetal brain development still requires further investigation.
URL: https://www.sciencedirect.com/science/article/pii/S1521689624000260

Highlights

The first category involves needle-based interventions such as the commonly practiced intra-uterine transfusion, used for treating anaemic foetuses (View Highlight)
The second category includes foetoscopic procedures using trocars for direct surgical visualization (View Highlight)

New highlights added June 16, 2024 at 2:11 PM

Historically, this approach was only used for the treatment of congenital pulmonary airway malformations (e.g., in cases of a tracheal web to safeguard the airway) around the time of delivery. This is usually referred to as an Ex Utero Intrapartum Treatment (EXIT) procedure, a modified caesarean delivery technique that allows surgical interventions to be performed while the neonate remains on placental circulation (View Highlight)
The Management of Myelomeningocele Study (MOMS trial) compared prenatal open foetal spina bifida repair with standard postnatal neurosurgical repair (View Highlight)
This involves not only alleviating pain in the mother and/or the foetus but also optimizing surgical conditions by ensuring effective uterine relaxation (View Highlight)
Anaesthesia aims to avoid maternal and foetal pain, to provide immobilization and/or to optimize surgical conditions by ensuring uterine relaxation. (View Highlight)
Open mid-gestational interventions, (e.g. meningo-myelocoele or resection of lung masses/teratomas) necessitate a laparotomy under maternal general anaesthesia, and require careful intra-operative management alongside optimal uterine relaxation (View Highlight)
From the gestational age of 15–18 weeks, it is advised to administer aspiration prophylaxis, to perform a correct preoxygenation and conduct a rapid sequence induction using cricoid pressure, inserting a cuffed endotracheal tube without an episode of mask ventilation (View Highlight)
several studies consistently found that gastric emptying remains nearly normal throughout pregnancy until the onset of labour (View Highlight)
the use of gastric ultrasound has, also during pregnancy [30], proven to be a feasible and reliable method for assessing the intragastric content and the consequent risk of aspiration (View Highlight)
pregnant women experience earlier desaturation during apnea compared to non-pregnant women [23], underscoring the necessity for adequate pre-oxygenation, ideally for at least 2 min and until an expiratory oxygen concentration of 80% is achieved. (View Highlight)
The inspired oxygen concentration should not surpass 35%, as higher values might elevate the presence of free oxygen radicals and the target maternal paCO2 should be maintained around 30 mmHg, a level considered as physiologic in pregnant women. (View Highlight)
human uterus lacks autoregulation (View Highlight)
To prevent uterine (and placental) hypoperfusion, it is advised to maintain maternal blood pressure at physiological levels (around 70–90% of baseline, or a mean arterial pressure >65 mmHg). This can be achieved by administering vaso-active drugs like phenylephrine or noradrenaline (ephedrine is used in cases of maternal bradycardia), providing intravenous fluids, avoiding excessively deep levels of general anaesthesia, and positioning the patient avoiding caval compression (preferably in left lateral tilt position of ≥30° [51,52]) from 10 to 18 weeks of gestation (View Highlight)
there is a notable decrease of 30–40% in the minimum alveolar concentration (MAC) of volatile anaesthetic agents from around 8 weeks [23]. Nevertheless, instances of awareness are more prevalent in the pregnant population (1 in 670 during general anaesthesia for caesarean section) compared to the general population (1 in 19,600) (View Highlight)
While neostigmine has been used for many years, it can lead to foetal bradycardia, necessitating the co-administration of atropine (View Highlight)
glycopyrrolate, unlike neostigmine, does not cross the placenta and therefore cannot prevent foetal bradycardia (View Highlight)
Cefazolin [57], ondansetron [58,59], and metoclopramide [58,59] are considered safe for use during pregnancy (View Highlight)
Postoperative analgesia is of utmost importance, as pain diminishes uterine blood flow and triggers premature contractions (View Highlight)
The use of non-steroidal anti-inflammatory drugs during pregnancy is to be avoided (View Highlight)
Pregnancy and surgical procedures both contribute to an increased susceptibility to thromboembolic complications (View Highlight)
Sustaining an adequate intrauterine volume by continuously replenishing lost amniotic fluid is also imperative during the perioperative period to avert severe uterine contractions (View Highlight)
In the 1980s, the medical consensus leaned towards the belief that foetuses and even newborns lacked the capacity to experience pain due to the underdeveloped cerebral cortex (View Highlight)
In the 1990s, it was noted that nociceptive stimuli in the foetus triggered the hypothalamo-pituitary-adrenal axis and the sympathetic nervous system [60,68,69]. However, using this stress response as a sole indicator for foetal pain had limitations: it did not involve the cortex, and responses like exercise, hypoxia, or haemorrhage could elicit similar reactions (View Highlight)
Later it was suggested that foetal pain perception required the transmission of pain stimuli from peripheral nociceptors to the somatosensory cortex [70,71]. This pathway, functional only from 24 weeks of gestation, implied that pain perception might only begin at this stage (View Highlight)
Responses before 24 weeks were viewed as reflexes rather than indicative of pain perception (View Highlight)
the latest evidence suggests that thalamic connections to the subplate, forming as early as 12 weeks of gestation, might be functionally equivalent to thalamocortical connections [68,70,71]. The subplate, a transient layer in the developing cerebral cortex, acts as an active precursor to the cortex [68,70]. Consequently, the emerging view is that foetal pain perception might occur as early as 12 weeks of gestation (View Highlight)
The exposure of foetuses to early pain and stress may impact their neurodevelopment, leading to both short- and long-term consequences (View Highlight)
Direct administration of fentanyl to the foetus has been observed to blunt the foetal stress response (View Highlight)
While volatile anaesthetics and propofol, critical components of foetal anaesthesia, cross the placenta, their foetal concentrations, even after prolonged administration, reach only around 70% and 50% of maternal concentrations, respectively [70,72]. This level may not suffice for foetal surgery (View Highlight)
in procedures involving innervated tissue or necessitating foetal immobilization, a combination of opioids (e.g., 10-20-50 μg/kg fentanyl), a neuromuscular blocker (e.g., 1.2 mg/kg rocuronium, 0.4 mg/kg cisatracurium, or 0.2 mg/kg vecuronium), and an anticholinergic drug (e.g., 10–20 μg/kg atropine) is administered (View Highlight)
Administering remifentanil to the mother (at 0.1 μg/kg/min) can offer maternal sedation, foetal immobilization, and foetal analgesia, thereby improving operating conditions (View Highlight)
Intravascular administration offers a rapid onset of action and can be achieved through the umbilical vein, large foetal veins, or intracardiacally, depending on the procedure [72]. However, this method presents potential disadvantages such as vessel thrombosis, vascular spasm, bleeding, and a possible compromise of the surgical view [72]. Accessing these routes can also be more challenging compared to other methods (View Highlight)
the intramuscular route is commonly employed during open surgery and some minimally invasive procedures, particularly those guided by ultrasound [72]. It offers easier administration with a lower risk of bleeding compared to intravenous methods [72]. However, drug absorption can be variable, making it more challenging to predict the time course of drug action accurately (View Highlight)
The groundbreaking work by Ikonomidou et al., in 1999 demonstrated the widespread neuronal apoptosis in foetal and neonatal rats by blocking NMDA receptors using dizocilpine [73]. This study laid the foundation for the hypothesis that exposure to general anaesthesia during brain development might significantly impact neurodevelopmental outcomes (View Highlight)
In 2003, Jevtovic-Todorovic et al. confirmed this hypothesis using anaesthetics commonly used in clinical practice [74]. They exposed early neonatal rats to midazolam, nitrous oxide, and isoflurane for 6 h, resulting in extensive neuronal apoptosis and subsequent learning and memory impairments (View Highlight)
In response to this growing body of evidence, in 2016, the Food and Drug Administration (FDA) issued a warning emphasizing that repeated or prolonged exposure to general anaesthesia during the third trimester of pregnancy might have adverse effects on neurodevelopment (View Highlight)
One notable limitation lies in the discrepancies between the duration, frequency, and doses of anaesthesia used in animal studies compared to typical clinical scenarios (View Highlight)
Neurological impairments were observed with repeated exposures, doses surpassing one MAC (minimum alveolar concentration), or durations extending beyond 3 h. A single exposure at or below 1 MAC for up to 3 h did not yield significant impairments. It is crucial to contextualize the duration of exposure concerning the animal's pregnancy duration: for instance, exposure to 3 h of anaesthesia in rats, mice, non-human primates, sheep, rabbits, and guinea pigs would roughly equate to 37, 43, 5, 6, 27, and 12 h of anaesthesia in humans, respectively (View Highlight)
Another limitation was the absence of surgical stimulation during most animal exposures to anaesthesia, which does not mirror clinical procedures where anaesthesia is often coupled with surgical interventions (View Highlight)
the animal studies generally fell short in terms of monitoring and maintaining physiological stability, not reaching the clinical standards expected in human settings. (View Highlight)
Clinical data on the effects of prenatal anaesthesia exposure and surgery are available only for maternal non-obstetric surgery (but not for foetal surgery) (View Highlight)
notable impairments were identified in specific subgroups of children whose mothers underwent general anaesthesia, intra-abdominal surgery, prolonged anaesthesia (>1 h), and laparoscopic surgery [86]. The impact of general anaesthesia and foetal surgery on foetal brain development remains a topic for prospective investigations. (View Highlight)
The key goals of anaesthesia in these scenarios are to prevent both maternal and foetal pain, ensure foetal immobilization, and optimize surgical conditions through uterine relaxation (View Highlight)
A critical consideration is the potential for the foetus to experience pain, which might occur as early as 12 weeks' gestation (View Highlight)