Is fetal analgesia necessary during prenatal surgery?
Fetal pain and fetal anesthesia are still matter of debate: some authors hypothesize that several intrauterine endocrine neuroinhibitors (ENIn) anesthetize the fetus, keeping it in a constant state of sleep, and making pharmacological fetal anesthesia useless for fetal surgery, while others argue fetal pain is possible and shoud be prevented with fetal anesthesy.


OBJECTIVE
To retrieve evidences about fetal pain, fetal arousability and about the level of sedation induced by the ENIn, in order to assess the necessity of direct fetal anesthesia during prenatal fetal surgery.


METHODS
We performed a careful literature review (1990-2016) on fetal arousability, and on the possibility that ENIn at the average fetal blood levels induce actual anesthesia. We retrieved the papers that fulfilled the research criteria, with particular attention to the second half of pregnancy, the period when most fetal surgery is performed.


RESULTS
Fetuses are awake about 10% of the total time in the last gestational weeks, and they can be aroused by external stimuli. ENIn have not an anesthetic effect at normal fetal values, but only when they areartificialy injected at high doses; their blood levels in the last trimester of average pregnancies are not dissimilar either in the fetus or in the mother.


CONCLUSIONS
During the second half of the pregnancy, external stimuli can awake the fetuses, although they spend most of the time in sleeping state; the presence of ENIn is absolutely not enough to guarantee an effective anesthesia during surgery. Thus, direct fetal analgesia/anesthesia is mandatory, though further studies on its possible drawbacks are necessary.
a Neonatal Intensive Care Unit , University Hospital of Siena , Siena , Italy.
Carlo V
CV
Bellieni
b Department of Molecular and Developmental Medicine, Division of Obstetrics and Gynecology , University of Siena , Siena , Italy.
Silvia
S
Vannuccini
b Department of Molecular and Developmental Medicine, Division of Obstetrics and Gynecology , University of Siena , Siena , Italy.
Felice
F
Petraglia
D000241:Adenosine / Q000097:blood / Q000502:physiology; D000698:Analgesia / Q000379:methods; D000758:Anesthesia / Q000379:methods; D001143:Arousal; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005333:Fetus / Q000294:innervation / Q000601:surgery*; D005865:Gestational Age; D006801:Humans; D016239:MEDLINE; D009420:Nervous System / Q000196:embryology; D010146:Pain / Q000196:embryology* / Q000517:prevention & control*; D059408:Pain Management; D011247:Pregnancy; D011280:Pregnanolone / Q000097:blood / Q000502:physiology; D015230:Prostaglandin D2 / Q000097:blood / Q000502:physiology
D011280:Pregnanolone; D000241:Adenosine; D015230:Prostaglandin D2
Pain; adenosine; analgesia; fetal analgesia; fetal pain; fetal surgery; fetus; newborn; pregnenolone; prostaglandins