Anaesthesia for Fetal Surgeries.pdf

Indian Journal of Anaesthesia, October PG Issue 2009

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Anaesthesia for Fetal SurgeriesKirti N Saxena

Summary

The concept of the fetus as a patient has evolved from prenatal diagnosis and serial observation of fetuses withanatomical abnormalities. . Surgical intervention is considered when a fetus presents with a congenital lesion that cancompromise or disturb vital function or cause severe postnatal morbidity. Hydronephrosis, saccrococcygeal ter-atoma, hydrocephalus, meningomyelocoele and diaphragmatic hernia are some of the defects that can be diagnosedby imaging and are amenable to intervention.

The combination of underdeveloped organ function and usually life-threatening congenital malformation placesthe fetus at a considerable risk. Fetal surgery also leads to enhanced surgical and anaesthetic risk in the motherincluding haemorrhage, infection, airway difficulties and amniotic fluid embolism.

There are 3 basic types of surgical interventions: 1.Ex utero intrapartum treatment(EXIT), 2.Midgestation openprocedures, 3.Minimally invasive midgestation procedures. These procedures require many manipulations and moni-toring in both the mother and the unborn fetus

Keywords Fetal surgery, Fetal interventions

Professor, Department of Anesthesiology & Intensive care, Maulana Azad Medical college, New Delhi, Correspondence to: KirtiN Saxena, B-302, Geetanjali Apartments, Vikas Marg Extension, New Delhi- 110092, Email: [email protected]

Indian Journal of Anaesthesia 2009; 53 (5):554-559

Introduction

The concept of the fetus as a patient has evolvedfrom prenatal diagnosis and serial observation of fe-tuses with anatomical abnormalities. Rh isoimmunisationprovided the first successful example of fetal interven-tion wherein intravenous blood transfusion was under-taken in a hydropic fetus. Since then several fetal medi-cal interventions like prenatal bone marrow transplan-tation and prenatal induction of lung maturity have beendone1.The use of prenatal means of diagnosing ana-tomical defects is increasing with ultrasound and fetalmagnetic resonance imaging. Surgical intervention isconsidered when a fetus presents with a congenital le-sion that can compromise or disturb vital function orcause severe postnatal morbidity. Hydronephrosis,saccrococcygeal teratoma, hydrocephalus,meningomyelocoele and diaphragmatic hernia are someof the defects that can be diagnosed by imaging andare amenable to intervention2.

Correcting an anatomical malformation in utero

with open fetal surgery jeopardizes the pregnancy andentails potential surgical and anaesthetic risks to themother as well as the fetus. For this reason fetal sur-gery remains limited to conditions which if allowed tocontinue , would irreversibly interfere with fetal organdevelopment but which if alleviated, would allow nor-mal development to proceed. Malformations that qualifyfor consideration of fetal surgery should satisfy the fol-lowing prerequisites:

1. Prenatal diagnostic techniques should identify themalformation and exclude other lethal malformationswith a high degree of certainty.

2. The defect should have a defined natural historyand cause progressive injury to the fetus that is irre-versible after delivery.

3. Repair of the defect should be feasible and shouldreverse or prevent the injury process.

4. Surgical repair must not entail excessive risk to themother or her future fertility

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If new surgical techniques, physiological supportsystems and tocolytic therapy can reduce fetal and ma-ternal risk to that of elective postnatal surgery, indica-tions for fetal surgery may be liberalized.

Risks

The combination of underdeveloped organ func-tion and usually life-threatening congenital malforma-tion places the fetus at a considerable risk. Surgery andanaesthesia lead to significant risks to the fetus and canresult in fetal death and morbidity .Altered coagulationfactors predispose the fetus to bleeding and cause dif-ficulty in achieving surgical haemostasis during fetalsurgery. This problem is compounded by the small bloodvolume of the fetus . Fetal surgery can result in prema-ture labor and birth. Initially surgeries were only per-formed in cases of impending fetal death.With the ad-vancements in anaesthetic and surgical techniques, therisks have decreased and the indications broadened.

Fetal surgery also leads to enhanced surgical andanaesthetic risk in the mother including haemorrhage,infection, airway difficulties and amniotic fluid embo-lism. Only ASA class I and II mothers with very sickfetuses are taken up for fetal surgery .Fetalsaccrococcygeal tumour leads to the ‘maternal mirrorsyndrome’, wherein the mother experiences progres-sive symptoms of preecclampsia due to release of toxinsfrom the placenta .This syndrome is terminated by de-livery of the fetus and placenta but not by the excisionof the tumour.

Fetal surgery

There are 3 basic types of surgical interventions:

1.Ex utero intrapartum treatment(EXIT)3

These are also known as OOPS i.e, operationon placental support. These interventions are performedon vaginal delivery or caesarean section. Only a por-tion of the fetus is delivered and brief procedures suchas endotracheal intubation or examination of neck massdone while the fetus is still connected to the placenta

through the umbilical cord .Only brief procedures werepossible as placental support rarely lasts for more than10 minutes during routine births. Techniques are beingevolved to allow placental support to continue for anhour or longer. It is possible to secure airway in casesranging from cystic hygroma to complete high airwayobstruction syndrome.The following procedures arebeing done as EXIT procedures:

Disease Procedure Congenital Removal of tracheal bal loon insertedDiaphragmatic at 22-27 weeks with midgestation Hernia procedure.ECMO cannulation for se

vere pulmonary hypoplasiaCongenital Perform tracheostomy high airway obstruction Syndrome(CHAOS)Giant cervical Resection of mass neck massAnticipated Laryngoscopy, bronchoscopy, difficult tracheostomy intubation

2.Midgestation open procedures

Recognition of foetal defect in early pregnancyallows intervention in midgestation to prevent irrevers-ible damage or development of secondarydisease.Hysterotomy is required to access the foetuswho is returned to the uterus after completion of sur-gery for the rest of the gestation. Fetal surgery is per-formed through a low transverse abdominal incision.Placental location is determined by ultrasonography anda wide uterine incision is given by a specially designedabsorbable stapler for performing bloodless hystero-tomy. The fetal part is exteriorized for surgery and aftercompletion of the surgery the fetus is placed back intothe uterus which is closed.

The fetus continues to grow for the rest of thegestation with reversal of the disease process thatprompted the fetal intervention. Example is repair ofmeningomyelocoele at 22 weeks of gestation to pre-vent damage to central nervous system tissues due to

Saxena Kirti N. Anaesthesia for fetal surgeries


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prolonged exposure to amniotic fluid. The sequelae ofbladder and bowel dysfunction and clubfeet may beprevented. The indications for open midgestation fetalsurgery are :

Disease ProcedureMeningomyelocoele Surgical repair of

meningomyelocoeleSaccrococcygeal Surgical resection of teratoma teratomaIntrathoracic masses Resection of massCongenital Temporary tracheal occlusion DiaphragmaticHernia with intrathoracic liverCongenital Cystic Lobectomy, pneumonectomy Adenoid Malformation

3.Minimally invasive midgestation procedures4

Because the uterus is a fluid filled organ, smallendoscopes allow excellent visualization of fetal andplacental structures as long as uterine distention is main-tained with irrigating fluid .These are basically of 2 types:

1.Fetendo procedures - Aberrant placental ves-sels providing imbalance of blood flow to twins can beidentified and ligated in this way to prevent fetal deathdue to twin-twin transfusion syndrome.Other surgeriespossible with this technique are radiofrequency abla-tion or coagulation of non viable twin’s umbilical cordin twin reversed arterial perfusion and division of amni-otic bands in amniotic band syndrome. Using fetoscopy,these aberrant vessels and bands can be identified andcoagulated . Fetal procedures , such as fetal cystoscopywith laser ablation of posterior urethral valves, are alsonow technically possible and are being undertaken.

2. FIGS-IT- This is a term used for fetal image-guided surgery for intervention or therapy, and describesthe method of manipulating the fetus without either anincision in the uterus or an endoscopic view inside theuterus. The manipulation is done entirely under real-time cross-sectional view provided by the sonogram.This is the same sonogram as is used for diagnosticpurposes, but in this case is used to guide instruments.

Like Fetendo, it can be done either through the mother’sskin or, in some cases, with a small opening in themother’s abdomen. It can often be done under a re-gional anaesthesia like an epidural or a spinal, or evenunder local anaesthesia. This is the least invasive of thefetal access techniques and, thus, causes the least prob-lem for mother in terms of hospitalization and discom-fort.

Anaesthetic goals of fetal surgery

Maternal anaesthetic considerations

Anaesthetic plan must accommodate all the physi-ological changes of pregnancy. Pregnancy affects ma-ternal pulmonary and cardiovascular function. There isincreased demand of oxygen so adequate precautionsshould be taken to prevent hypoxaemia and aspiration .Decreases in capillary oncotic pressure and increasesin capillary permeability increase the risk of pulmonaryedema specially when magnesium sulphate is used fortocolysis.Left uterine displacement to preventaortocaval compression must be done.Doses of an-aesthetic agents should take the increased sensitivity ofthe parturient into consideration.

Fetal anaesthetic considerations

Fisk et al5 demonstrated increased cortisol, beta-endorphins, and the “central sparing response” in a 23week old human fetus needled in the hepatic (inner-vated) vein. 10mcg.kg-1 fentanyl suppressed the beta-endorphin and cortisol responses but not the centralsparing response to this noxious stimulus. For the firsttime it was demonstrated that the human fetal stressresponse was attenuated by the administration of a nar-cotic. Long- term effects of fetal stress have also beendescribed. Independent groups have implicated fetalstress to exaggerated pain responses in eight week-oldinfants and have also implicated the fetal stress responseas a contributor to pre-term labor.

There is need for fetal anaesthesia in contrast tocaesarean section where a vigorous baby is desirableon delivery. Placental transfer of of anaesthetic agents

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to the fetus is a desirable effect of maternal anaesthe-sia. The fetus requires less muscle relaxant and anaes-thetic agent.Although inhaled anaesthetics, rapidly crossthe placenta ,fetal levels remain below maternal levelsfor a prolonged period of time.

Less cardiac contractile tissue leads to depres-sion from volatile anaesthetic.6 Anaesthetic-induceddecreases in contractility combined with fetal surgicalmanipulations can result in hypotension,bradycardia,and eventual cardiac collapse. Becauseof low circulating blood volume and rate dependentcardiac output, surgical blood loss is poorly toleratedso trigger for transfusion is low.Thin fetal skin predis-poses fetus to hypothermia so active warming is re-quired during exposure from uterus. Hypothermia canbe minimized by limiting fetal surgical time and use ofwarm irrigating fluids.

Maintenance of uteroplacental circulation is vitalfor successful outcome of the procedure. Fetal oxy-genation is dependent on both blood oxygenation andplacental bloodflow. Uterine tone increases duringcontractions and this increases vascular resistance.Since uteroplacental flow is influenced by vascular re-sistance therefore uterus must remain relaxed. Kinkingof umbilical cord must be avoided and corrected if thishas occurred during changing position of the fetus tofacilitate blood flow. Increase of maternal pH and hy-pocapnia result in reduced umbilical blood flow andfetal hypoxia.

Preoperative preparation3

Preanaesthetic checkup is done to evaluate themother with special emphasis on maternal and familyhistory of anaesthetic problems, airway evaluation andconcurrent medical problems.The placental location andfetal cardiovascular function are evaluated by ultra-sonography, echocardiography, magnetic resonanceimaging .

The patient is admitted on the day of surgery afterbeing nil orally. The operating room is warmed to 80°Fand type specific packed red cells for the mother and

O-negative packed red cells for the fetus are madeavailable. Monitors include two pulse oximeters ,anarterial pressure transducer and cardiac monitor for themother sodium bicitrate is given orally andmetoclopramide given intravenously as prophylaxis foraspiration.An indomethacin suppository is administeredfor postoperative tocolysis in midgestation procedures.

The fetal care team consists of obstetricians , pe-diatricians, surgeons specializing in fetal surgery andanaesthesiologists. Intensive care facilities for bothmother and neonate are available.

Fetal monitoring6

For procedures where the fetal extremity is ac-cessible, a pulse oximeter probe is placed on the limband wrapped with foil to decrease interference withambient light. Normal fetal arterial saturation is 60-70%and values above 40% during surgery represent ad-equate saturation.

Echocardiography is used to monitor fetal heartrate and stroke volume. Fetal arterial or venous bloodgas samples may be obtained by the surgeons percuta-neously or through umbilical or central vessel puncture.Warmed, fresh O-negative blood can be administeredto the fetus to correct anaemia.

Anaesthetic plan for Fetal Surgery Procedures

Ex Utero Intrapartum Treatment Procedures

EXIT procedures require maternal laparotomyand hysterotomy while maintaining uteroplacental cir-culation. General anaesthesia is preferable as it accom-plishes both maternal and fetal anaesthesia.7

Adequate preoxygenation is followed by rapidsequence induction. Desirable uterine atony can bemaintained with high concentrations of volatileanaesthetics .However, this leads to maternal hypoten-sion which is treated by intravenous fluids and sym-pathomimetics to maintain mean arterial pressure towithin 20% of the baseline to preserve uteroplacentalblood flow.



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Following uterine incision, the operative site of thefetus is delivered through the hysterotomy. Care is takento prevent kinking of the umbilical cord.Fetal monitor-ing with pulse oximetry and echocardiography are un-dertaken. Before start of the intervention, fetal anaes-thesia is supplemented by intramuscular or intravenousinjection of vecuronium and fentanyl. If blood loss ishigh then the surgeon can perform intravenous cannu-lation of the fetus to give drugs and fluids.Good fetalanaesthesia relieves fetal stress and ensures good op-erating conditions.

Endotracheal intubation may be undertaken in thefetus with severe cardiac defects to prevent hypoxaemiaat birth. Placement of an LMA can be done if the fetushas an airway problem and tracheostomy performedfollowing delivery.

After completion of the procedure the infant isdelivered , the umbilical cord divided and the babyplaced in the care of a neonatologist. Following this theuterine atony is reversed by reducing the concentrationof volatile anaesthetic and giving methergin .Adequatereplacement of fluids must be done since EXIT proce-dures are more prone to blood loss than caesarean sec-tion. An epidural catheter may be placed for postop-erative analgesia in the mother.

After surgery there are two patients to be caredfor, and a second operating room should be availablein case further surgery is needed in the neonate.

Midgestation Open fetal Surgery

This is similar to the EXIT procedures as far asthe exposure of the fetus is concerned but is done inthe second trimester .Since the fetus is returned to theuterus after completion of the intervention, the parturi-ent requires tocolysis and fluid restriction.

The mother is induced by rapid sequence tech-nique . An arterial catheter is placed before increasingthe concentration of volatile anaesthetic upto two anda half MACs. Fetal monitoring is done with pulse oxim-etry and echocardiography. Fetal analgesia may besupplemented with intravenous or intramuscular medi-

cation. After completion of the intervention the fetus isreturned to the uterus The amniotic fluid is replaced bywarmed Ringer’s solution containing antibiotics and theuterus closed .

Aggressive tocolysis is initiated after conclusionof the fetal procedure with an intravenous infusion ofmagnesium sulphate to prevent reflex uterine contrac-tions. These can result in reduced uteroplacental bloodflow and result in premature labor. Magnesium sulphatecan increase the risk of pulmonary edema which canbe managed by the use of adrenergic agents .Magne-sium sulphate also increases sensitivity to muscle relax-ants hence neuromuscular monitoring should be done.

In the postoperative period , the mother is mater-nal-fetal intensive care unit . Uterine activity and fetalheart rate are continuously monitored bytocodynamometry. Use of an epidural catheter reducesthe maternal stress response and incidence of earlypreterm labor8.

Minimally Invasive Surgery

Most procedures can be done with large boreneedle under ultrasound imaging or a 5-mm trocar. Thefetal surgery trocar has a camera and a port for a laserfibre to coagulate placental vessels in twin-twin trans-fusion syndrome .In fetoscopy, normal saline irrigationis used inside the uterus. The maternal incision is smalland such procedures can be performed under localanaesthesia with infiltration of both skin and peritoneum.Epidural, spinal or combined spinal-epidural anaesthe-sia can be used9

Intravenous sedation should be given for mater-nal anxiolysis for fetoscopy because of the emotionalnature of surgery and the awkward position of themother. Midazolam, fentanyl, remifentanil or propofolinfusion may be used but deep sedation should beavoided to prevent aspiration. The uterus is irrigatedwith normal saline in this procedure and this can beabsorbed. This fluid can also enter the peritoneal cav-ity through the fallopian tubes from where it can beabsorbed. This can lead to pulmonary edema as the

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patient is also receiving tocolytics. This can be treatedwith diuretics and may be anticipated when the volumeof irrigating fluid is much higher than the returning fluid.Most fetoscopy procedures involve manipulation ofplacenta and umbilical cord and there is no fetal inci-sion therefore fetal anesthesia is not required.10

The Future

Fetal surgery is a new field that is expanding rap-idly .Currently it is being done only in few centers in theworld . Anaesthetists are an important part of the teamand specialized training is required for fetal anaesthe-sia. This is a rapidly evolving field and some controver-sies still need to be resolved. Standardised assessmenttools and blood microsampling techniques for the fetusneed to be developed to allow further development ofclinical protocols. Questions regarding fetal stress andoptimal drug dosing in the fetus remain open to specu-lation until these techniques evolve to answer our ques-tions. In line with the trend in the adult, neonatal mini-mally invasive congenital heart surgery has become animportant area of interest.11

References

1. Liley AW.Intrauterine transfusion of foetus inhaemolytic disease.BMJ 1963;5365:1107-1109.

2. Flake AW. Fetal therapy. In Maternal-Fetal medicine.2004.Published by Saunders 5th Edition:1244.

3. Robinson MB.Frontiers in fetal surgery anesthesia .InInternational Anaesthesiology Clinics.2006.Publishedby Lippincott,Williams and Wilkins .Volume44;No.1:1-15.

4. ht tp: / / fetus.ucsfmedicalcenter.org/our_team/fetal_intervention.asp.

5. Fisk N, Gitau R, Tiexeira J, et al. Effect of direct opioidanalgesia on fetal hormonal and hemodynamic stressresponse to intrauterine needling. Anesthesiology 2001;95:828-35.

6. Galinkin JL, Schwarz U, Motoyama EK. Anesthesia forfetal surgery. In Smith’s anesthesia for infants and chil-dren.2006 Published by Mosby.7th Edition:509-20

7. Rosen M. Anesthesia for fetal procedures and surgery.In: Schnider SM, Levinson G, eds. Anesthesia for Ob-stetrics, 3rd Ed. Baltimore: Williams & Wilkins, 1993:281-295.

8. Gaiser RR, Kurth CD. Anesthetic considerations for fetalsurgery. Semin Perinatol 1999; 23: 507-514.

9. Bulich LA, Jennings RW.Intrauterine fetal manipulation.In Anaesthetic and obstetric management of high riskpregnancy2004. Published by Springer.3rd Edition:33-44.

10. Cromblehoholme TM.Surgical treatment of thefetus.Fanaroff and Martin’s: Neonatal perinatalmedicine.2006.Published by Mosby ;8th Ed:231-254.

11. Wittkope MM. Interventional fetal cardiac therapy-pos-sible perspectives and current shortcomings. UltrasoundObstet Gynecol 2002; 20: 527-531.


OBITUARYWith profound grief, Jhansi City Branch of U.P., Chapter, ISA informs the sad demise

of Dr.K.K.Gupta(M.D) on 9.7.09 at the age of 60 yrs. An ISA life member. Dr.Guptahad served as Secretary ISA, UP Chapter(98-01) and was an active member of ISA,UP state. He was born on 05.04.1949 and is survived by wife one daughter and a son.

Dr. Roopesh KumarAsstt. Prof.,M.L.B. Medical College, Jhansi (UP)

Dr.K.K.Gupta(05.04.1949-09.07.2009)

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Anaesthesia for Fetal Surgeries.pdf