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Fetal surgery and anaesthetic

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Fetal surgery and anaesthetic

Fetal surgery and anaesthetic

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  • 1. Fetal surgery and anaesthetic implications Ritu Gupta MB ChB FCARCSI Mark Kilby MBBS MD MRCOG Griselda Cooper OBE FRCA FRCOG Downloaded from http://ceaccp.oxfordjournals.org at National Institutes of Health Library on July 14, 2010Surgery to the fetus while it is still in utero is fetal transfusions); these are the most Key pointsused to treat an increasing number of lethal and commonly performed procedures.non-lethal conditions. The problems of preterm (ii) Fetoscopic therapy. Fetal surgery is performedlabour and premature rupture of membranes (iii) Open procedure, involving a hysterotomy. in specialist centres and requires multidisciplinaryassociated with open surgery have led to the Intrauterine transfusions for rhesus disease and teamwork.development of minimal access surgical tech- fetal anaemia are performed by ultrasound- In addition to obstetricniques. Although fetal surgery is a new and fast directed fetal vessel puncture under local anaesthetic considerations,moving frontier of medicine, it is not one that anaesthesia. For other, more complex surgery, the anaesthetist needs to beall obstetric anaesthetists will encounter. The the anaesthetist is part of a multidisciplinary conversant with tocolyticfirst successful human fetal operation was per- methods. team which allows understanding of the patho-formed in 1983, but it is still only carried out genesis of the fetal conditions and how the Fetal analgesia is requiredin a limited number of specialist tertiary planned therapy may influence outcome. In this for some procedures.centres. article, it is assumed that the anaesthetist is The use of fetoscopic The broad challenges presented to the familiar with routine obstetric anaesthetic con- procedures is increasing;anaesthetist are: siderations: those relevant to the fetal surgery however, presently, only are highlighted. laser ablation of placental (i) those related to any anaesthetic in a preg- vessels is of proven efficacy. nant woman; (ii) techniques used to prevent preterm labour; Twin– twin transfusion(iii) maintenance of maternal homeostasis in syndrome the face of tocolytic techniques; Twin –twin transfusion syndrome (TTTS) is a(iv) maintenance of fetal homeostasis; serious complication of a twin pregnancy in Ritu Gupta MB ChB FCARCSI (v) provision of fetal analgesia during which there is only one placenta (monochorio- Specialist Registrar surgery; nic twin gestation). It complicates 10 –20% of Department of Anaesthesia Queen Elizabeth Hospital(vi) distance the mother may need to travel monochorionic identical twin pregnancies.1 It Edgbaston from home. is due to unequal blood flow across vascular Birmingham B15 2TH anastomoses between the two fetal circulations UKIt is expected that the indications for fetal with the larger twin being at risk of cardiac Mark Kilby MBBS MD MRCOGtherapy will expand. The most frequently overload and the smaller twin being relatively Dame Hilda Lloyd Professor of Maternaloccurring condition operated on relatively com- hypoperfused. In addition to the severe haemo- and Fetal Medicine Birmingham Women’s Hospitalmonly in the UK is twin-to-twin transfusion dynamic imbalance, there are discordant liquor University of Birminghamsyndrome. Life-threatening conditions that have volumes, the ‘recipient’ twin having severe Metchley Park Roadhad in utero intervention to lessen the severity polyhydramnios, and the ‘donor’ having severe Edgbaston Birmingham B15 2TGof pathology include congenital diaphragmatic oligohydramnios adhering onto the uterine UKhernia, obstructive uropathy, and sacrococcy- wall. Both twins are therefore at risk of severegeal teratoma. There is also a prospective ran- haemodynamic compromise, death, and prema- Griselda Cooper OBE FRCA FRCOGdomized trial ongoing in the USA to determine ture delivery. TTTS is diagnosed by ultrasound. Consultant Anaesthetist Department of Anaesthesiathe role and efficacy of in utero surgery for In addition to the fetal complications, parturi- Queen Elizabeth Hospitalmyelomeningocele. ents with severe TTTS may rarely develop Edgbaston Fetal surgical interventions include the ‘mirror syndrome’2 which is characterized Birmingham B15 2TH UKfollowing. by pulmonary oedema, anasarca (severe Tel: þ44 121 627 2060 generalized oedema), albuminuria, hyperten- Fax: þ44 121 627 2062 (i) Minimally invasive ( percutaneous inser- sion, and a reduction in haemoglobin concen- E-mail: gcooper@rcanae.org.uk (for correspondence) tion of shunts and in utero, intravascular tration due to haemodilution. The maternaldoi:10.1093/bjaceaccp/mkn004Continuing Education in Anaesthesia, Critical Care & Pain | Volume 8 Number 2 2008 71& The Board of Management and Trustees of the British Journal of Anaesthesia [2008].All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
  • 2. Fetal surgery and anaesthetic implicationsmanifestations generally reflect the severity of the fetal placental a reduced risk of long-term neurodevelopmental morbidity in sur-pathology. vivors, see Figure 1. Treatment options include amnioreduction (removing 1– 4 litres Real-time ultrasound allows location of the placenta, umbilicalof amniotic fluid from around the recipient). This is often per- cord, and amniotic membranes. Technically, an anterior placentalformed before 26 weeks gestation and requires serial procedures site may be more surgically demanding. However, modification ofuntil delivery. Although this is a relatively inexpensive simple surgical instruments, positioning of the patient, and the creation oftechnique that can be performed with limited experience and pro- an adequate ‘operating window’ using amnioinfusion all aid ade-vides potential rescue for both fetuses, it does not affect the under- quate visualization of the chorionic plate and inter-twin membrane. Downloaded from http://ceaccp.oxfordjournals.org at National Institutes of Health Library on July 14, 2010lying pathology. There is little improvement in the fetal condition Risks of the procedure include: amniorrhexis ( pre-labour rupturedin advanced disease and a randomized controlled trial has shown amniotic membranes) 5%; subchorionic bleed (,1%); pretermthat pregnancies treated using this method have a greater likelihood delivery; neuromorbidity; and double or single fetal death.of survivors with cerebral palsy. Follow-up is required as there is a 5% recurrence rate. Recently, laser ablation of placental vessels has emerged as a In many centres, maternal spinal, epidural, or combinedpotential treatment for severe TTTS. It involves fetoscopic laser spinal/epidural anaesthesia is used. Alternatively, local infiltrationphotocoagulation of unidirectional arteriovenous vessels on the of the skin and subcutaneous tissues with lidocaine 1% (downsurface of the twin placenta and attenuation of the haemodynamic to the myometrium) and maternal sedation is used. Inconsequences of this pathophysiology. This technique prolongs addition to maternal sedation, pharmacotherapy also causes fetalpregnancy compared with amnioreduction.3 A recent systematic immobilization. In a randomized controlled trial, Missant andreview indicated that fetoscopic laser ablation was associated with colleagues4 demonstrated that remifentanil was a safer optionimproved outcomes for fetal survival of one or both twins and than diazepam.Fig. 1 A systematic review of the RCT and two comparative controlled trials assessing the efficacy of fetoscopic laser ablation in the treatment of severeTTTS72 Continuing Education in Anaesthesia, Critical Care & Pain j Volume 8 Number 2 2008
  • 3. Fetal surgery and anaesthetic implicationsCongenital diaphragmatic hernia are delivered to preserve umbilical blood flow and to prevent eva- porative heat and fluid loss. This allows time to secure the neonatalThe incidence of congenital diaphragmatic hernia is 1:2400 live airway. Continued uteroplacental circulation has been maintainedbirths.1 It causes pulmonary hypoplasia by compression of lung for up to 1 h without fetal compromise.7 A potential complicationtissue from the herniated organs and arguably abnormal develop- is antepartum haemorrhage at the time in which the fetal airway isment of the pulmonary vasculature. Until recently, the possibilities being secured due to the need for uterine relaxation.available to expectant parents of a fetus diagnosed with congenital General anaesthesia is indicated. The mother is prepared for thediaphragmatic hernia were termination of pregnancy or continu- eventuality of major haemorrhage with monitoring instituted Downloaded from http://ceaccp.oxfordjournals.org at National Institutes of Health Library on July 14, 2010ation of the pregnancy until term with postnatal surgical correction. before surgery, i.e. two large bore i.v. cannulae, arterial line,A series of case cohort studies using modern fetoscopic procedures central venous line, and availability of cross-matched blood.have indicated that potentially severe congenital diaphragmatic A rapid sequence induction with left uterine displacement (redu-hernia with a high predicted risk of fatal pulmonary hypoplasia cing aorto-caval compression) is carried out with the adminis-may have improved overall survival with in utero therapy. tration of high concentrations of volatile anaesthetic agent Recent studies have focused on ‘in utero triage’ of the fetus (e.g. isoflurane 2– 3%) to maintain uterine relaxation. Otheremphasizing the exclusion of co-existent structural and chromoso- tocolytics (Table 1) may be needed if there is inadequate uterinemal anomalies which carry a corresponding poor prognosis. In relaxation. Vasopressor agents are required for the consequentaddition, poor lung development can be prospectively identified by maternal hypotension in order to maintain uterine blood flow andultrasound; liver in the fetal chest; and a lung–head ratio of ,1 maternal well-being. Fetal anaesthesia is obtained via placentalare relatively sensitive and specific for identifying fetuses develop- transfer of volatile agents, but occasionally muscular paralysis maying pulmonary hypoplasia. Such triage has allowed the possibility be necessary to ensure fetal immobility.7 Once the fetal airway hasof fetal therapeutic intervention. Animal studies have indicated that been secured, the uterus is made to contract with an infusion oftransient tracheal occlusion may prevent or lessen the structural oxytocin.and physiological effects of pulmonary hypoplasia.5 To date, two Close monitoring of uterine contraction, cardiovascular par-studies have utilized lung –head ratio to establish the prospective ameters, and any haemorrhage is essential after the operation.high risk of pulmonary hypoplasia within groups of fetuses and Thus, mother and baby will both require high dependency care. Incompared outcome after treatment by fetoscopic tracheal occlusion the absence of contraindications (e.g. coagulopathy), epiduralwith conservative management. analgesia can be considered for the mother. In such fetoscopic procedures, combined spinal anaesthesia orlocal anaesthesia is required and immobilization of the fetus isessential.Ex utero intrapartum treatment procedure Table 1 Tocolytic agents Agent Advantages CautionThe ex utero intrapartum treatment (EXIT) procedure is now usedto establish a patent airway in the management of fetuses with b-adrenergic agents, e.g. Maternal tachycardia,potential airway obstruction.6 It allows the continuing placental terbutaline, ritodrine hypotension, myocardial ischaemia, decreased glucoseperfusion of the partially exteriorized fetus until a formal airway tolerance, pulmonary oedemahas been established. Some common indications include: Magnesium sulphate In high concentration fetal side-effects include decreased (i) mass obstructing the upper airway, e.g. cystic hygroma, heart rate variability, reduced thyroid goitre; muscular activity at birth Halogenated volatile Used to provide Prolonged use can cause fetal (ii) congenital high airway obstruction syndrome (CHAOS). This agents, e.g. isoflurane intraoperative acidosis spectrum of anomalies includes laryngeal web, atresia, or relaxation cyst, and tracheal atresia or stenosis. It is characterized by Glyceryl trinitrate Rapid onset of action enlarged lungs, dilated distal airways, everted diaphragm, Non-steroidal Limited to short-term use for ascites, and ultimately non-immune hydrops fetalis; anti-inflammatory 48 h, and before gestational(iii) thoracic abnormalities, e.g. hydrothorax, tumours. drugs, e.g. age of 32 weeks, due to risk of indomethacin premature closure of ductusThe EXIT procedure allows intubation, tracheostomy, or even arteriosus in the fetus, decreased renal functionresection of the lesion while the infant is still on placental support. resulting in oligohydramnios,Management requires obstetricians, anaesthetists, otolaryngolo- increased risks of necrotisinggists, and paediatric surgeons. EXIT procedures are performed enterocolitis and intraventricular haemorrhageduring caesarean section before clamping of the umbilical cord. Calcium antagonists Maternal hypotensionWhen performing a hysterotomy, only the fetal head and shoulders Continuing Education in Anaesthesia, Critical Care & Pain j Volume 8 Number 2 2008 73
  • 4. Fetal surgery and anaesthetic implicationsObstructive uropathy (i) Neural development. Peripheral nerve receptors develop between 7 and 20 weeks gestation, and afferent C fibres beginObstructive uropathy occurs in one in 1000 live births.5 Upper development at 8 weeks and are complete by 30 weeks ges-urinary tract obstruction is associated with less morbidity and mor- tation. Spinothalamic fibres (responsible for transmission oftality than lower obstruction which is usually caused by posterior pain) develop between 16 and 20 weeks gestation, and thala-urethral valves. mocortical fibres between 17 and 24 weeks gestation. The obstruction increases bladder pressure, resulting in changes (ii) Behavioural responses. Movement of the fetus in response toin bladder structure and function, vesicoureteric reflux, hydroureter, external stimuli occurs as early as 8 weeks gestation, and Downloaded from http://ceaccp.oxfordjournals.org at National Institutes of Health Library on July 14, 2010hydronephrosis, and a risk of chronic renal failure later in life.1 there is reaction to sound from 20 weeks gestation. ResponseThe resulting oligohydramnios and pulmonary hypoplasia increases to painful stimuli occurs from 22 weeks gestation.neonatal mortality. Fetal surgery aims to prevent this from (iii) Fetal stress response. Fetal stress in response to painfuloccurring. stimuli is shown by increased cortisol and b-endorphin con- Open surgery (nephrostomy) carries a high mortality, a risk of centrations, and vigorous movements and breathing efforts.7,9amniorrhexis and preterm labour, and a third of those treated still There is no correlation between maternal and fetal norepi-require transplantation at a later stage. It requires maternal hyster- nephrine levels, suggesting a lack of placental transfer of nor-otomy and has largely been abandoned. Fetal vesicoamniotic epinephrine. This independent stress response in the fetusshunting is the placement of a catheter, using a percutaneous occurs from 18 weeks gestation.10 There may be long-termneedle under continuous ultrasound guidance, into the fetal implications of not providing adequate fetal analgesia such asbladder. The distal end of the catheter traverses the fetal anterior hyperalgesia, and possibly increased morbidity and mortality.abdominal wall and drains into the amniotic cavity. This procedureis usually performed under local anaesthesia with lidocaine. Fetal analgesiaMyelomeningocele As with any procedure, the provision of analgesia depends on theThe diagnosis of myelomeningocele is possible in early pregnancy. likely severity of pain associated with the intervention. However,It causes progressive neurological impairment and carries a poor analgesia is recommended for:prognosis. Prenatal diagnosis and treatment may allow prevention (i) endoscopic, intrauterine surgery on placenta, cord, andof the neurological deficit and preserve spinal cord cryoarchitecture. membranes; (ii) late termination of pregnancy; (iii) direct surgical trauma to the fetus.Tocolysis For open surgery, where a general anaesthetic technique (with orTocolysis is essential during fetal surgery and after operation as without an epidural) is used, the fetus obtains anaesthesia via thefetal interventions are associated with preterm labour. Impaired placenta, although direct administration from i.m. injections canuterine blood flow or partial placental separation can occur due to also be used.uterine manipulation or incisions, hence jeopardizing umbilical – For fetoscopic fetal surgery, maternal anaesthesia is mostplacental blood flow. Even minor interventions (e.g. needle usually by local anaesthetic infiltration or a regional block. A com-insertion for intrauterine transfusion) can result in strong uterine bined spinal/epidural minimizes haemodynamic changes.contractions, and hence may cause unintentional puncture of other These techniques can be supplemented with sedation or remi-structures. Tocolysis is also important after operation as preterm fentanil. Local or regional techniques are sometimes difficultuterine contractions can still occur. Table 1 gives examples of the because of maternal anxiety; in addition, they may not adequatelytocolytic agents which can be used and the main points about immobilize the fetus. A mobile fetus can displace the endoscopetheir use. The choice of agent is determined by maternal side- resulting in bleeding, fetal trauma, or compromised umbilical cir-effects.6 Drugs acting on the uterus have been reviewed culation resulting in fetal death. The short-acting opioid remifenta-elsewhere.8 nil is easy to titrate and crosses the placenta readily immobilizing the fetus. Using a continuous infusion rate of remifentanil 0.1 mg kg21 min21, fetal immobilization and maternal sedation areFetal stress achieved.4 Mild respiratory acidosis occurs but maternal apnoeaThere is considerable evidence that the fetus may experience pain. can be avoided and good operating conditions obtained. This tech-Not only is there a moral obligation to provide fetal anaesthesia nique is recommended for TTTS.4and analgesia, but it has also been shown that pain and stress may Fetal anaesthesia, homeostasis, and immobility can be providedaffect fetal survival and neurodevelopment.7 Factors suggesting by direct fetal injections (i.m. or into the umbilical cord) with thethat the fetus experiences pain include the following. use of opioids, atropine, and neuromuscular blocking agents. Fetal74 Continuing Education in Anaesthesia, Critical Care & Pain j Volume 8 Number 2 2008
  • 5. Fetal surgery and anaesthetic implicationsTable 2 Complications of minimal access fetal surgery ReferencesComplication How it can be minimized 1. Danzer E, Sydorak RM, Harrison MR, Albanese CT. Review minimal access fetal surgery. Eur J Obstet Gynaecol Reprod Biol 2003; 108:Bleeding Avoid placenta on entering uterus 3–13Preterm labour Use of tocolytics. Many theories used to describe why this occurs (e.g. rapid changes in uterine volume, 2. Carbillon L, Oury JF, Guerin JM, Azancot A. Clinical biological features infection, hormonal changes, fetomaternal stress, of Ballantyne syndrome and the role of placental hydrops. Obstet Gynecol and membrane rupture) Surv 1997; 52: 310–4Chorioamniotic membrane Surgical technique 3. Senat MV, Deprest J, Boulvain M, Paupe A, Winer N, Ville Y. Endoscopic Downloaded from http://ceaccp.oxfordjournals.org at National Institutes of Health Library on July 14, 2010 separation laser surgery versus serial amnioreduction for severe twin-to-twin trans-Premature rupture of Most common problem associated with fetal surgery. fusion syndrome. New Engl J Med 2004; 351: 182–4 membranes Research is ongoing into sealing ruptured membranes with collagen plugs 4. Missant C, Van Schoubroeck D, Deprest J, Devlieger R, Teunkens A, Van de Velde M. Remifentanil for fetal immobilisation and maternal sedation during endoscopic treatment of twin-to-twin transfusion syn- drome:a preliminary dose-finding study. Acta Anaesthesiol Belg 2004; 55:i.m. opioids reduces the stress response.5 Suitable anaesthetic tech- 239–44niques for fetoscopic surgery on membranes, cord, and the pla- 5. Fisk N, Gitau R, Teixeira J, Giannakoulopoulos X, Cameron A, Glover V.centa are as discussed above. Effect of direct fetal opioid analgesia on fetal hormonal and haemo- dynamic stress response to intrauterine needling. Anesthesiology 2001; 95: 828– 35Complications 6. Hirose S, Farmer DL, Lee H, Nobuhara KK. The ex utero intrapartum treatment procedure: looking back at the EXIT. J Pediatr Surg 2004; 39:The complications of minimal access fetal surgery are summarized 375–80in Table 2. 7. Boris P, Cox PBW, Gogarten W, Strumper D, Marcus MAE. Fetal surgery, anaesthesiological considerations. Curr Opin Anaesthesiol 2004; 17: 235– 40 8. Eagland K, Cooper GM. Drugs acting on the uterus. Bull Royal CollSocial factors Anaesth 2001, 10: 473–6As minimal access fetal surgery is only carried out in specialist 9. Giannakoulopoulos X, Teixeira J, Fisk N. Human fetal and maternal nor-centres, patients frequently have to travel long distances. adrenaline responses to invasive procedures. Pediatr Res 1999; 45: 494–9Organization needs to include social support for the families where 10. Marcus M, Gogarten W, Louwen F. Remifentanil for fetal intrauterinenecessary. This is an important factor when considering discharge microendoscopic procedures. Anesth Analg 1999; 88: S257from hospital. Good communication between the tertiary centreand referring hospital is vital. Please see multiple choice questions 25 –28 Continuing Education in Anaesthesia, Critical Care & Pain j Volume 8 Number 2 2008 75