Fetal pain a systematic multidisciplinary review


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Fetal pain a systematic multidisciplinary review

  1. 1. Fetal Pain: A Systematic Multidisciplinary Review of the Evidence Susan J. Lee; Henry J. Peter Ralston; Eleanor A. Drey; et al.Online article and related contentcurrent as of February 20, 2010. JAMA. 2005;294(8):947-954 (doi:10.1001/jama.294.8.947) http://jama.ama-assn.org/cgi/content/full/294/8/947 Correction Contact me if this article is corrected. Citations This article has been cited 28 times. Contact me when this article is cited. Topic collections Medical Practice; Health Policy; Law and Medicine; Anesthesia; Pain; Patient-Physician Relationship/ Care; Patient-Physician Communication; Womens Health; Pregnancy and Breast Feeding Contact me when new articles are published in these topic areas. Related Letters Fetal Pain Laura B. Myers et al. JAMA. 2006;295(2):159. Bobbi J. Lyman. JAMA. 2006;295(2):159. Brian D. Sites. JAMA. 2006;295(2):160. In Reply: Susan J. Lee et al. JAMA. 2006;295(2):160. Subscribe Email Alerts http://jama.com/subscribe http://jamaarchives.com/alerts Permissions Reprints/E-prints permissions@ama-assn.org reprints@ama-assn.org http://pubs.ama-assn.org/misc/permissions.dtl Downloaded from www.jama.com by guest on February 20, 2010
  2. 2. CLINICAL REVIEW CLINICIAN’S CORNERFetal PainA Systematic Multidisciplinary Review of the EvidenceSusan J. Lee, JD Context Proposed federal legislation would require physicians to inform womenHenry J. Peter Ralston, MD seeking abortions at 20 or more weeks after fertilization that the fetus feels pain and to offer anesthesia administered directly to the fetus. This article examinesEleanor A. Drey, MD, EdM whether a fetus feels pain and if so, whether safe and effective techniques exist forJohn Colin Partridge, MD, MPH providing direct fetal anesthesia or analgesia in the context of therapeutic proce-Mark A. Rosen, MD dures or abortion. Evidence Acquisition Systematic search of PubMed for English-language articlesO VER THE LAST SEVERAL focusing on human studies related to fetal pain, anesthesia, and analgesia. Included years, many states, includ- articles studied fetuses of less than 30 weeks’ gestational age or specifically addressed ing California, Kentucky, fetal pain perception or nociception. Articles were reviewed for additional references. Minnesota, Montana, New The search was performed without date limitations and was current as of June 6,York, Oregon, and Virginia, have con- 2005.sidered legislation requiring physi- Evidence Synthesis Pain perception requires conscious recognition or awarenesscians to inform women seeking abor- of a noxious stimulus. Neither withdrawal reflexes nor hormonal stress responses totions that the fetus feels pain and to offer invasive procedures prove the existence of fetal pain, because they can be elicited byfetal anesthesia. This year, Arkansas and nonpainful stimuli and occur without conscious cortical processing. Fetal awarenessGeorgia enacted such statutes.1,2 Cur- of noxious stimuli requires functional thalamocortical connections. Thalamocortical fi-rently, Congress is considering legisla- bers begin appearing between 23 to 30 weeks’ gestational age, while electroencepha-tion requiring physicians to inform lography suggests the capacity for functional pain perception in preterm neonates prob- ably does not exist before 29 or 30 weeks. For fetal surgery, women may receive generalwomen seeking abortions 20 or more anesthesia and/or analgesics intended for placental transfer, and parenteral opioidsweeks after fertilization (ie, 22 weeks’ may be administered to the fetus under direct or sonographic visualization. In thesegestational age) that the fetus has “physi- circumstances, administration of anesthesia and analgesia serves purposes unrelatedcal structures necessary to experience to reduction of fetal pain, including inhibition of fetal movement, prevention of fetalpain,” as evidenced by “draw[ing] away hormonal stress responses, and induction of uterine atony.from surgical instruments.” The physi- Conclusions Evidence regarding the capacity for fetal pain is limited but indicatescian must also offer anesthesia or anal- that fetal perception of pain is unlikely before the third trimester. Little or no evidencegesia “administered directly” to the fe- addresses the effectiveness of direct fetal anesthetic or analgesic techniques. Simi-tus. Physicians who do not comply may larly, limited or no data exist on the safety of such techniques for pregnant women inbe subject to substantial fines, license re- the context of abortion. Anesthetic techniques currently used during fetal surgery arevocation, and civil suits for punitive not directly applicable to abortion procedures.damages.3 JAMA. 2005;294:947-954 www.jama.com Although this legislation would notaffect most US abortions because only step in answering these questions, we Author Affiliations: School of Medicine (Ms Lee),1.4% are performed at or after 21 weeks’ Department of Anatomy and W. M. Keck Founda- reviewed the literature on fetal pain andgestational age,4 this legislation raises tion for Integrative Neuroscience (Dr Ralston), and fetal anesthesia and analgesia. Departments of Obstetrics, Gynecology and Repro-important scientific, clinical, ethical, ductive Sciences (Drs Drey and Rosen), Pediatricsand policy issues. When does a fetus EVIDENCE ACQUISITION (Dr Partridge), and Anesthesia and Perioperative Care (Dr Rosen), University of California, San Fran-have the functional capacity to feel English-language articles involving hu- cisco.pain? If that capacity exists, what forms man participants were searched using Corresponding Author: Mark A. Rosen, MD, Depart- ment of Anesthesia and Perioperative Care, Univer-of anesthesia or analgesia are safe and PubMed for (1) fetal pain (16 articles), sity of California, San Francisco, 513 Parnassus Ave,effective for treating fetal pain? As a first fetal anesthesia (6 articles), and fetal an- San Francisco, CA 94143-0648 (rosenm@anesthesia .ucsf.edu). algesia (3 articles); (2) fetus and (anes- Clinical Review Section Editor: Michael S. Lauer, MD.CME available online at thesia or analgesia) (1239 articles); (3) We encourage authors to submit papers for consider-www.jama.com ation as a “Clinical Review.” Please contact Michael S. Medical Subject Headings (MeSH) an- Lauer, MD, at lauerm@ccf.org.©2005 American Medical Association. All rights reserved. (Reprinted) JAMA, August 24/31, 2005—Vol 294, No. 8 947 Downloaded from www.jama.com by guest on February 20, 2010
  3. 3. FETAL PAIN algesics/administration and dosage and fe-Figure. Spinal Reflex and Pain Perception Pathways tus (44 articles); (4) MeSH anesthesia/ administration and dosage and fetus (0 A Spinal Reflex articles); (5) (neurodevelopment or devel- opment or anatomy) and (fetus or fetal) Dorsal Root Ganglion SPINAL CORD and (pain or nociception or noxious) (306 articles); (6) (thalamocortical or thala- 2 Peripheral 3 Dorsal Horn mus or cortex) and (fetus or fetal) and Sensory Neuron Interneuron (pain or nociception or noxious) (13 ar- ticles); (7) (electroencephalog* or EEG or 1 Noxious evoked potential) and (fetus or fetal or pre- Stimulus mature neonate or premature infant or pre- 4 Ventral Horn term neonate or preterm infant) and (pain L E Motor Neuron or nociception or noxious or conscious*) SC MU (7 articles); (8) fetal and pain and (re- 5 Contraction sponse or assessment or facial expres- sion) (112 articles); and (9) facial expres- sion and (fetus or fetal) or ([neonate or neonatal or infant] and [premature or pre- B Pain Perception via the Spinothalamic Tract term]) and (pain or nociception or nox- ious) (360 articles). The search was per- C BRAIN formed without date limitations and was O R current as of June 6, 2005. From these TE X 6 Thalamocortical Axon 7 Perception search results, we excluded articles that did not study fetuses of less than 30 weeks’ gestational age or that did not spe- 5 Thalamus cifically address fetal pain perception or nociception. With a focus on topics ad- dressed by earlier review articles on fe- tal pain, anesthesia, and analgesia, ar- ticles were reviewed for additional references. EVIDENCE SYNTHESIS 4 Spinothalamic What Is Pain? 3 Spinothalamic Tract Pain is a subjective sensory and emo- Neuron tional experience that requires the pres- Dorsal Root Ganglion ence of consciousness to permit recog- nition of a stimulus as unpleasant.5-7 2 Peripheral Sensory Neuron Although pain is commonly associated with physical noxious stimuli, such as when one suffers a wound, pain is fun- damentally a psychological construct that 1 Noxious Stimulus may exist even in the absence of physi- cal stimuli, as seen in phantom limb SPINAL CORD pain.5,7 The psychological nature of pain also distinguishes it from nociception, which involves physical activation of no- ciceptive pathways without the subjec-A, Reflex responses to noxious stimuli occur early in development, before thalamocortical circuits are func-tional; noxious stimuli trigger reflex movement without cortical involvement. Activated by a noxious stimulus tive emotional experience of pain.5,8 For(1), a peripheral sensory neuron (2) synapses on a dorsal horn interneuron (3) that in turn synapses on a ven- example, nociception without pain ex-tral horn motor neuron (4), leading to reflex muscle contraction and limb withdrawal (5). B, Later in develop- ists below the level of a spinal cord le-ment, noxious stimuli (1) activate peripheral sensory neurons (2) that synapse on spinothalamic tract neurons(3), the axons of which extend up the spinal cord as the spinothalamic tract (4) to synapse on neurons of the sion, where reflex withdrawal from athalamus (5). From here, thalamocortical axons synapse on cortical neurons, resulting in the conscious per- noxious stimulus occurs without con-ception of pain. scious perception of pain (FIGURE, A).5948 JAMA, August 24/31, 2005—Vol 294, No. 8 (Reprinted) ©2005 American Medical Association. All rights reserved. Downloaded from www.jama.com by guest on February 20, 2010
  4. 4. FETAL PAINTable. Anatomical and Functional Development of Nociception and Pain Perception Pathways Anatomical/ Gestational Functional Characteristic Description Age, wk SourcePeripheral cutaneous sensory receptors Perioral cutaneous sensory receptors 7.5 Palmar cutaneous sensory receptors 10-10.5 Humphrey,13 1964 Abdominal cutaneous sensory receptors 15Spinal cord Spinal reflex arc in response to nonnoxious stimuli 8 Okado and Kojima,14 1984 Neurons for nociception in dorsal root ganglion 19 Konstantinidou et al,15 1995Thalamic afferents Thalamic afferents reach subplate zone 20-22 Kostovic and Rakic,16 1990 Hevner,17 2000 Thalamic afferents reach cortical plate 23-24 Kostovic and Rakic,18 1984 Kostovic and Goldman-Rakic,19 1983Cortical function* Somatosensory evoked potentials with distinct, 29 Klimach and Cooke,20 1988 constant components Hrbek et al,21 1973 First electrocardiographic pattern denoting both 30 Clancy et al,22 2003 wakefulness and active sleep Torres and Anderson,23 1985*Earliest evidence of functional thalamocortical connections required for conscious perception of pain. Because pain is a psychological con- cortical pathways required for con- showing initial cortical plate penetra-struct with emotional content, the ex- scious perception of pain (TABLE). tion at 22 weeks’ developmental age (24perience of pain is modulated by chang- No human studies have directly ex- weeks’ gestational age).24ing emotional input and may need to be amined the development of thalamo- In a study of 8 human fetuses, me-learned through life experience.7,9,10 Re- cortical circuits associated with pain diodorsal thalamic afferents were firstgardless of whether the emotional con- perception. The developmental age at observed in the cortical plate at 22tent of pain is acquired, the psychologi- which thalamic pain fibers reach the weeks’ developmental age (24 weeks’cal nature of pain presupposes the cortex has been inferred from studies gestational age).19 While connectionspresence of functional thalamocortical of other thalamocortical circuits, which between mediodorsal afferents and thecircuitry required for conscious percep- may or may not develop at the same anterior cingulate cortex25 may be rel-tion, as discussed below. time as thalamic fibers mediating cor- evant to pain perception,12,26 this study tical perception of pain. examined mediodorsal afferents to un-Fetal Capacity for Pain These histological neurodevelop- specified regions of the frontal cor-Neuroanatomy and Development. No- ment studies typically describe fetal ma- tex,19 which serves numerous func-ciception may be characterized by re- turity in terms of developmental age, tions unrelated to pain perception.19,27flex movement in response to a nox- representing the number of weeks post- Another histological study of 12 speci-ious stimulus, without cortical ovulation or postfertilization. Clini- mens found that afferents from unspeci-involvement or conscious pain percep- cians regularly use gestational age, rep- fied thalamic regions reached the devel-tion. Nociception involves peripheral resenting weeks from the first day of the oping prefrontal cortex in 1 pretermsensory receptors whose afferent fi- woman’s last menstrual period. When neonate of 27 weeks’ developmental age,bers synapse in the spinal cord on in- referring to a fetus at the same point in concluding that thalamic fibers beginterneurons, which synapse on motor development, the gestational age is ap- entering the cortex between 26 and 28neurons that also reside in the spinal proximately 2 weeks greater than the weeks’ developmental age (28 and 30cord. These motor neurons trigger developmental age. weeks’ gestational age).28 A different studymuscle contraction, causing limb flex- A histological study of the visual found that thalamic afferents had notion away from a stimulus (Figure, A).11 pathway in 8 human fetuses, each at a reached the somatosensory cortical plate In contrast, pain perception re- different developmental age, con- by 22 weeks’ developmental age (24quires cortical recognition of the stimu- cluded that thalamic projections reach weeks’ gestational age). By 24 weeks’lus as unpleasant. Peripheral sensory re- the visual cortex at 21 to 25 weeks’ de- developmental age (26 weeks’ gesta-ceptor afferents synapse on spinal cord velopmental age (approximately 23-27 tional age), the density of cortical plateneurons, the axons of which project to weeks’ gestational age), based on re- synapses increased, although these werethe thalamus, which sends afferents to sults from a fetus of 24 weeks’ devel- not necessarily from thalamic affer-the cerebral cortex (Figure, B),11 acti- opmental age (26 weeks’ gestational ents.16 Based on these studies, direct thala-vating any number of cortical re- age).18 A similar 7-fetus study found mocortical fibers that are not specific forgions.12 Sensory receptors and spinal thalamic afferents reached the audi- pain begin to emerge between 21 and 28cord synapses required for nocicep- tory cortical plate at 24 to 26 weeks’ de- weeks’ developmental age (23 and 30tion develop earlier than the thalamo- velopmental age, with 1 specimen weeks’ gestational age).©2005 American Medical Association. All rights reserved. (Reprinted) JAMA, August 24/31, 2005—Vol 294, No. 8 949 Downloaded from www.jama.com by guest on February 20, 2010
  5. 5. FETAL PAIN However, others have proposed that 24 weeks’ postconceptional age (PCA) PCA, suggesting that the capacity of thethalamocortical connections could also (ie, the gestational age plus number of neonate to distinguish between nox-be established indirectly if thalamic af- weeks postpartum).22 Electroencepha- ious and nonnoxious stimuli is matur-ferents were to synapse on subplate neu- lographic activity is normally asynchro- ing. 37 Furthermore, flexion with-rons, which could synapse on cortical nous between the hemispheres and drawal from tactile stimuli is aplate neurons.29 The subplate is a tran- mostly discontinuous at less than 27 noncortical spinal reflex exhibited bysient fetal structure 1 layer deep to the weeks’ PCA,23,33,34 becoming mostly infants with anencephaly38 and by in-cortical plate and serves as a “waiting continuous around 34 weeks’ PCA.23,34 dividuals in a persistent vegetativecompartment” for various afferents, in- Interhemispheric synchrony increases state39 who lack cortical function.cluding thalamic afferents, en route to around 29 to 30 weeks’ PCA, then de- Behavioral studies have also identi-the cortical plate.16,29,30 The subplate re- clines, then increases again, reaching al- fied a distinct set of neonatal facialcedes after 30 weeks’ developmental most complete synchrony by term.22,33 movements present during invasiveage,16,29 while the cortical plate ma- Given these baseline differences be- procedures such as heel lancing buttures into the 6 layers of the cerebral tween neonatal and adult EEGs, pat- absent during noninvasive proce-cortex.28 In contrast to direct thalamo- terns associated with impaired con- dures.40-46 These facial movements,cortical fibers, which are not visible un- sciousness in adults33,35 are inapplicable which are similar to those of adults ex-til almost the third trimester, thalamic to the analysis of neonatal EEGs. periencing pain,47,48 were evident in neo-afferents begin to reach the somatosen- Some investigators contend that EEG nates at 28 to 30 weeks’ PCA but notsory subplate at 18 weeks’ developmen- patterns denoting wakefulness indi- at 25 to 27 weeks’ PCA.40 Facial move-tal age (20 weeks’ gestational age)16 and cate when consciousness is first pos- ments may not necessarily be corti-the visual subplate at 20 to 22 weeks’ sible.5,36 Wakefulness is a state of arousal cally controlled.49 One study found nogestational age.17 These afferents ap- mediated by the brainstem and thala- difference in facial activity during heelpear morphologically mature enough to mus in communication with the lancing of neonates with and withoutsynapse with subplate neurons,31 al- cortex.5,22 In preterm neonates, the ear- significant cortical injury, suggestingthough no human study has shown that liest EEG pattern representing wake- that facial activity even around 32functional synapses exist between tha- fulness appears around 30 weeks’ weeks’ PCA may not represent con-lamic afferents and subplate neurons. PCA.22,23 However, wakefulness alone scious perception of pain.50Subplate neurons may synapse with cor- is insufficient to establish conscious- Stress Responses. Hemodynamictical plate neurons and direct the growth ness, as unconscious patients in a per- and neuroendocrine changes in fe-of thalamic afferents to their final syn- sistent vegetative state may also have tuses undergoing stressful proceduresaptic targets in the cortical plate.29 De- wakeful EEGs.5,36 have also been used to infer pain per-spite this developmental role, no hu- Somatosensory evoked potentials ception.51 As early as 16 weeks’ gesta-man study has shown that synapses (SEPs) may also provide evidence of tional age, fetal cerebral blood flow in-between subplate and cortical plate neu- pain processing in the somatosensory creases during venipuncture androns convey information about pain per- cortex, although they are not used clini- transfusions that access the fetal he-ception from the thalamus to the de- cally to test pain pathways. SEPs test the patic vein through the innervated fe-veloping cortex. dorsal column tract of the spinal cord, tal abdominal wall but not during ve- Electroencephalography. The his- which transmits visceral pain sensa- nipuncture and transfusions involvingtological presence of thalamocortical tion to the somatosensory cortex via the the noninnervated umbilical cord.52 In-fibers is insufficient to establish capac- thalamus.12 SEPs with distinct and con- creased cerebral blood flow is not nec-ity for pain perception. These anatomi- stant N1 components of normal peak essarily indicative of pain, as this re-cal structures must also be functional. latency are present at 29 weeks’ PCA, sponse is thought to constitute a “brainAlthough no electroencephalographic indicating that thalamic connections sparing” mechanism associated with“pain pattern” exists, electroencepha- with the somatosensory cortex are func- hypoxia 53 and intrauterine growthlography may be one way of assessing tional at that time.20,21 restriction.54general cortical function because elec- Behavioral Studies. Although widely Other investigators measured in-troencephalograms (EEGs) measure used to assess pain in neonates, with- creases in fetal plasma concentrations ofsummated synaptic potentials from cor- drawal reflexes and facial movements cortisol, -endorphin, and noradrena-tical neurons. However, EEG activity do not necessarily represent con- line associated with intrauterine nee-alone does not prove functionality, be- scious perception of pain. Full-term dling procedures, finding that increasescause neonates with anencephaly who neonates exhibit a “cutaneous with- during blood sampling from the hepaticlack functional neural tissue above the drawal reflex” that is activated at a vein were greater than those during sam-brainstem may still have EEG activity.32 threshold much lower than that which pling from the umbilical cord.55,56 How- Normal EEG patterns have been would produce discomfort in a child or ever, these neuroendocrine responses docharacterized for neonates as young as adult.37 This threshold increases with not constitute evidence of fetal pain,950 JAMA, August 24/31, 2005—Vol 294, No. 8 (Reprinted) ©2005 American Medical Association. All rights reserved. Downloaded from www.jama.com by guest on February 20, 2010
  6. 6. FETAL PAINbecause the autonomic nervous system ward the fetus represents the chief jus- general anesthesia are unjustified forand hypothalamic-pituitary-adrenal axis tification for using fetal anesthesia or these procedures; adults typically un-mediate them without conscious corti- analgesia during abortion—to relieve dergo similar procedures with no an-cal processing.57 Additionally, these suffering if fetal pain exists. As with any algesia or only local analgesia.67 No es-responses are not specific for painful clinical decision, thorough safety and tablished fetal analgesia protocol existsstimuli. Plasma noradrenaline concen- risk-benefit analyses should be under- for these procedures, although 3 tech-trations may increase after umbilical cord taken before performing an interven- niques have been proposed, namely, di-transfusion,56 and plasma -endorphin tion. Because the principle of benefi- rect delivery of medications to the fe-concentrations may increase after cence also requires the woman’s tus, delivery of medications to the fetusrepeated cordocenteses.58 Plasma corti- physician to act in her best interests, po- via maternal intravenous infusion, andsol and -endorphin concentrations tential fetal benefit must be weighed intra-amniotic delivery of medications.increase during innocuous activities such against real risks to the woman’s health. Direct Delivery. One group has ex-as exercise.59 Moreover, in adults, neu- The safety and effectiveness of pro- amined the effects of analgesics deliv-roendocrine stress responses may per- posed fetal anesthesia and analgesia ered directly to human fetuses duringsist despite well-controlled postopera- techniques are discussed below. minimally invasive procedures. 8 7tive pain.60 General Anesthesia for Fetal Surgery. Twenty-eight fetuses that received in- Vital signs also have been used to as- Fetal surgery involving laparotomy, hys- travenous fentanyl before hepatic veinsess neonatal pain.42,43,45,51,61 However, terotomy, or both requires general or blood transfusions had diminishedheart rate, respiratory rate, and trans- regional anesthesia.68,76 Regional anes- changes in plasma -endorphin con-cutaneous oxygen and carbon dioxide thesia, such as epidural anesthesia, does centration and cerebral blood flow, com-levels do not necessarily differ signifi- not anesthetize the fetus.76 General anes- pared with fetuses not receiving fen-cantly between alcohol-swabbing and thesia is more commonly used because tanyl. The cortisol response was notlancing the heels of preterm neo- it induces uterine atony and fetal immo- significantly decreased with fentanyl.nates.40 Another group found that a simi- bilization.65,77 Studies of inhalational The investigators did not examine riskslar proportion of neonates became hy- agents in pregnant ewes determined that for the woman, such as infection or un-poxic during tracheal suction, as well as a dose capable of anesthetizing the ewe controlled bleeding.76 Furthermore, re-during nonnoxious routine care such as also anesthetized the fetus.78 Admin- ducing the stress response is distinctwashing and weighing.62 istering fentanyl, pancuronium, or from reducing pain. For example, vecuronium to the fetus intramuscu- plasma glucose and cortisol concentra-Fetal Anesthesia and Analgesia larly may supplement analgesia or tions may not differ significantly be-Anesthetics and analgesics are com- immobilization.64,65,77,79 tween adults with and without postop-monly used to alleviate pain and dis- For pregnant women, general anes- erative pain.60comfort. Despite ongoing debate re- thesia is associated with increased mor- Delivery via Maternal Intravenousgarding fetal capacity for pain, fetal bidity and mortality, particularly because Infusion. To achieve presumably effec-anesthesia and analgesia are still war- of airway-related complications80-82 and tive fetal plasma concentrations of fen-ranted for surgical procedures under- increased risk of hemorrhage from uter- tanyl by placental transfer, potentiallytaken to promote fetal health. When ine atony.70 Historically, general anes- unsafe doses would need to be admin-long-term fetal well-being is a central thesia was used in abortions, even in the istered to the woman.88 Although stan-consideration, evidence of fetal pain is first trimester, until studies found that dard doses of fentanyl are generally safeunnecessary to justify fetal anesthesia general anesthesia was a leading cause for maternal analgesia during labor,89and analgesia because they serve other of abortion-related mortality.83-85 In addi- fentanyl can pose serious risks such aspurposes unrelated to pain reduction, tion to safety concerns, general anes- hypoventilation if maternal doses areincluding (1) inhibiting fetal move- thesia increases the cost of abortion, significantly increased to achieve morement during a procedure 63-65 ; (2) making it prohibitively expensive for the extensive placental transfer.67,68 Se-achieving uterine atony to improve sur- majority of patients who pay out of vere maternal hypoventilation may re-gical access to the fetus and to prevent pocket.86 quire endotracheal intubation, whichcontractions and placental separa- Anesthesia and Analgesia in Mini- increases risks and costs for the woman,tion66-70; (3) preventing hormonal stress mally Invasive Fetal Procedures. In as described above.responses associated with poor surgi- contrast to fetal surgery requiring re- No data exist on the dosing or effi-cal outcomes in neonates71,72; and (4) gional or general anesthesia, mini- cacy of using medications such as di-preventing possible adverse effects on mally invasive fetal procedures do not azepam and morphine for fetal analge-long-term neurodevelopment and be- involve maternal laparotomy or hys- sia via maternal intravenous infusion,havioral responses to pain.73-75 terotomy and instead use needles or en- although studies have characterized the These objectives are not applicable doscopy to access the fetus. For the sake placental transfer of these medica-to abortions. Instead, beneficence to- of reducing pain, the increased risks of tions.90-92 Two related studies found that©2005 American Medical Association. All rights reserved. (Reprinted) JAMA, August 24/31, 2005—Vol 294, No. 8 951 Downloaded from www.jama.com by guest on February 20, 2010
  7. 7. FETAL PAINlow-dose remifentanil via maternal in- these tests of cortical function suggest Because pain perception probablytravenous infusion achieved fetal im- that conscious perception of pain does does not function before the third tri-mobilization during laser coagulation not begin before the third trimester. mester, discussions of fetal pain forof placental vessels.93,94 However, im- Cutaneous withdrawal reflexes and abortions performed before the end ofmobilization is not the equivalent of hormonal stress responses present ear- the second trimester should be non-pain reduction, and these procedures lier in development are not explicit or compulsory. Fetal anesthesia or anal-did not involve surgery on the fetus. sufficient evidence of pain perception gesia should not be recommended or Intra-amniotic Delivery. Intra- because they are not specific to nox- routinely offered for abortion becauseamniotic injection would be techni- ious stimuli and are not cortically current experimental techniques pro-cally simpler than direct fetal injec- mediated. vide unknown fetal benefit and may in-tion, although the drug must be A variety of anesthetic and analge- crease risks for the woman. Instead, fur-absorbed through fetal membranes and sic techniques have been used for fetal ther research should focus on whenskin. Intra-amniotic sufentanil injec- surgery, including maternal general an- pain-related thalamocortical path-tion in 10 pregnant ewes resulted in fe- esthesia, regional anesthesia, and ad- ways become functional in humans. Iftal plasma concentrations that would ministration of medications for placen- the fetus can feel pain, additional re-control postoperative pain in human tal transfer to the fetus. However, these search may lead to effective fetal anes-adults.95,96 Sufentanil concentrations in techniques are not necessarily appli- thesia or analgesia techniques that arethe ewes also reached adult human cable to abortions. Surgical proce- also safe for women.therapeutic concentrations without dures undertaken for fetal benefit use Financial Disclosures: None reported.causing significant hemodynamic anesthesia to achieve objectives unre-changes.96 However, the study did not lated to pain control, such as uterine REFERENCESevaluate fetal response to noxious relaxation, fetal immobilization, and 1. Unborn Child Pain Awareness and Prevention Actstimuli, and no data exist regarding possible prevention of neuroendo- of 2005. To be codified at Ark Code Ann §§20-16- 1101 to 1111.safety or effectiveness in humans. crine stress responses associated with 2. Woman’s Right to Know Act. To be codified at Ga poor surgical outcomes. 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