Anaesthesia for foetal surgery

c u r r e n t m e d i c i n e r e s e a r c h a n d p r a c t i c e 5 ( 2 0 1 5 ) 2 2 e2 5

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Review Article

Anaesthesia for foetal surgery Archna Koul*, Raminder Sehgal, Jayashree Sood Department of Anaesthesiology, Pain and Perioperative Medicine, Sir Ganga Ram Hospital, Old Rajinder Nagar, New Delhi 110060, India

article info

abstract

Article history:

Anaesthesia for foetal surgery is one of the most exciting and challenging fields of anaes-

Received 7 December 2014

thesia. The anaesthetist is involved in the well being of two or more patients (mother and

Accepted 20 January 2015

foetus or foetuses). Hysterotomy based procedures, Ex-utero intrapartum therapy (EXIT),

Available online 24 February 2015

minimally invasive foetoscopic procedures and micro-invasive image-guided procedures are done, utilizing placental support for foetal well being; while the mother can receive

Keywords:

general anaesthesia, regional anaesthesia or local anaesthesia. Haemodynamic stability,

Foetal surgery

vigilant monitoring, judicious fluid replacement, adequate maternal tocolysis, good intra-

Anaesthesia

operative and postoperative analgesia are the anaesthetic goals. Ethical considerations for

Exit procedures

foetal surgery are like those involved in organ transplant, and should always be considered

Foetoscopic surgery

before planning such procedures, which involve multidisciplinary team work. Copyright © 2015, Sir Ganga Ram Hospital. Published by Reed Elsevier India Pvt. Ltd. All rights reserved.

With advancement in prenatal diagnostic technologies especially ultrasonography, an increasing number of foetal anomalies are being diagnosed early in gestation. Some of these conditions may benefit from prenatal surgical intervention. Foetal surgery is a reasonable alternative for selected foetal anomalies that cause harm to the foetus before the adequate development of foetal lung maturity necessary for extra uterine survival. Foetal surgery targets those foetal malformations which if allowed proceeding to the normal onset of labour and delivery will result in foetal demise or permanent disability but are potentially correctable in utero. These procedures on the foetus or placenta are designed to alter the natural history of a foetal disease that is diagnosed in utero. During the procedure the foetus continues to be perfused by the placenta and umbilical circulation. Foetal surgery is reasonable only1


If the lesion is diagnosed accurately
The lesion's severity is assessed correctly
Associated congenital anomalies that contraindicate intervention are excluded
Maternal risk is acceptably low and
It is likely to be more successful than surgery performed after preterm or term delivery There are three types of foetal surgical procedures which are usually performed at 18e26 weeks of gestation: a. Open foetal surgery or hysterotomy during which the foetus is exteriorized for the surgical procedure and then placed back in the uterus to mature till term if possible. b. Ex-utero intrapartum therapy (EXIT) previously called as airway management on placental support or operations on placental support are also hysterotomy based procedures

* Corresponding author. Tel.: þ91 11 25735205, þ91 (0) 9958892622 (mobile); fax: þ91 11 25861002. E-mail address: [email protected] (A. Koul). http://dx.doi.org/10.1016/j.cmrp.2015.01.005 2352-0817/Copyright © 2015, Sir Ganga Ram Hospital. Published by Reed Elsevier India Pvt. Ltd. All rights reserved.

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but are performed near term and are followed by delivery of the foetus. It is reserved for foetuses with expected post gestation airway or oxygenation compromise. Surgery is done after hysterotomy but prior to cord clamping. During this time foetal oxygenation is maintained by placental transfer of oxygen. c. Minimally invasive procedures. These are the most frequently performed procedures nowadays. The uterine cavity is accessed percutaneously with the help of needles or sheaths and visualization is aided noninvasively with the help of sonography or foetoscopes. There has been an evolution of approach from open procedures to less invasive approach such as uterine endoscopy and more recently percutaneous procedures using endoscopes with diameter of 3 mm or less. This progression to micro-invasive foetoscopic approaches has been associated with reduction in mortality, less bleeding, less chances of preterm labour and preterm premature rupture of membranes; less incidence of chorio-amnionitis and amniotic leak. These procedures can be done under local anaesthesia with infiltration of abdominal wall or if necessary under regional anaesthesia (Table 2). Foetal surgery is a specialized branch performed only at few centers worldwide. The indications for foetal surgery have increased with time (Table 1). But only two procedures are currently supported by randomized clinical trials. The first one is the open correction of myelomeningocele and second is endoscopic laser therapy for twin-to-twin transfusion syndrome.2,3 The common indications for foetal surgery1,4 are listed in Table 1. Providing anaesthesia for foetal surgery is a unique challenge, because more than one patient needs to be considered. The foetus is treated as a patient in its own right while the parturient has been referred to as an innocent bystander, who is exposed to surgical and postpartum risk but receives no health benefits.5 Therefore the mother should always be protected from undue risks (Table 2).

1. Maternal anaesthetic aspects of foetal surgery While planning anaesthesia for foetal surgical procedures. The broad challenges presented to the anaesthesiologist are6 1. Those related to any anaesthestic in a pregnant women 2. Techniques to prevent preterm labour 3. Maintenance of maternal homeostasis in the face of tocolytic techniques 4. Maintenance of foetal homeostasis 5. Provision of foetal analgesia during surgery

1.1.

Table 1 e Indications for open/hysterotomy, minimally invasive foetal surgery and EXIT procedures.1,4 Type

Foetal lesion/anomaly

Open

Congenital diaphragmatic hernia Congenital cystic adenomatoid malformation Myelomeningocele

Sacrococcygeal teratoma Minimally TwineTwin transfusion invasive syndrome Twin reversed arterial perfusion Obstructive uropathy

EXIT

Cyanotic heart disease Aortic/pulmonary stenosis Congenital diaphragmatic hernia Foetal cervical masses

Foetal lung masses Foetal mediastinal masses EXIT to extra corporeal membrane oxygenation [ECMO]

Reversal of tracheal occlusion after tracheal clip or endoluminal balloon procedures Bridge to separation of conjoint twins

Reasons for treatment Lung hyperplasia Hydrops foetal, lung hypoplasia Amniotic fluid neurotoxicity Hydrops foetalis Laser ablation of vessels Radiofrequency ablation or ligation of cord of non viable twin Shunt insertion and valve ablation Atrial septostomy Valvuoplasty Tracheal ballon occlusion Lymphangioma Teratoma Haemangioma Neuroblastoma Goitre Bronchopulmonary sequestration Teratoma Lymphangioma Severe congenital diaphragmatic hernia with liver herniation into chest cavity Congenital heart disease CDH

increases the risk for caval compression, supine hypotension syndrome and uterine hypoperfusion due to decreased venous return. Left lateral tilted position is important during foetal surgery to avoid this complication especially when the foetus is placed back in the uterus after surgery.7 All these mothers require antibiotic prophylaxis, prophylaxis for bronchoaspiration and thromboembolic venous diseases.8 Minimum alveolar concentration (MAC) values for volatile anaesthetic are decreased by approximately 40% during pregnancy. Therefore while using inhalational agents hypotension at high concentrations should be anticipated. Besides there is increased sensitivity to local anaesthetic agent.

Physiological changes during pregnancy 1.2.

Pregnancy related anatomical and physiological changes affect the anaesthetic management of woman presenting for foetal surgery. Patients presenting for these procedures often have polyhydramnios, where the second trimester uterus becomes as large as near term in a normal pregnancy, this

Uterine relaxation

For open foetal surgery and EXIT procedures, profound uterine relaxation is required for optimal surgical exposure of the foetus, for optimal placental gas exchange and prevention of preterm labour postoperatively.7 This is achieved primarily by

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Table 2 e Anaesthetic management of different types of foetal surgery.20

1. Maternal anaesthesia 2. Desired uterine lone 3. Foetal anaesthesia

Open surgery

Exit

Minimally invasive

GA þ EA for postoperative analgesia Complete relaxation Transplacental inhalational agents, direct (IM or umbilical cord) opioids and muscle relaxants

GA ± EA Complete relaxation Same as open

LA or neuraxial anaesthesia ± IV sedation Minimal relaxation Direct (IM or umbilical cord) opioids and muscle relaxants or transplacental opioids like remifentanil

GA: general anaesthesia, EA: epidural anaesthesia.

administering volatile anaesthetics at concentrations of 2e3 times the MAC value intraoperatively as they are very potent uterine relaxants. If despite the use of volatile agents, uterine relaxation is not adequate, then drugs like intravenous nitroglycerine, magnesium sulphate (MgSO4), b adrenergic agents (ritodrine terbutaline), Calcium antagonists and even non-steroidal anti-inflammatory drugs (indomethacin) are used for tocolysis, in postoperative period also, to prevent preterm labour.6

1.3.

Maintenance of uteroplacental blood flow

It is important to maintain maternal blood pressure within 20% of baseline values as high concentration of volatile anaesthetic agents and tocolytic drugs can cause severe hypotension due to decreased systemic vascular resistance and cardiac depression. Intermittent bolus administration of vasoactive agents such as ephedrine or phenylepherine or phenylepherine infusion is frequently used during the procedure to counteract the decreased systemic vascular resistance that occurs due to high volatile agent concentration.9

1.4.

Volume replacement

Pregnant patients have decreased colloidal oncotic pressure and increased capillary permeability. This increases the risk of pulmonary oedema especially following the use of tocolytics like MgSO4 which causes vasodilation. Activation of renin angiotensin aldosterone system has also been proposed as a cause for pulmonary oedema due to salt and water retention.10 Therefore intravenous fluids have to be administered very judiciously. Total fluids are usually restricted to less than 1 litre unless there is blood loss. Amniotic fluid lost through the hysterotomy is replaced with a continuous infusion of warm lactated Ringer's solution to prevent cord compression.

1.5.

Maternal monitoring

.The key to maternal safety is meticulous perioperative monitoring of physiological parameters which is of prime concern to anaesthesiologist. This includes pulse oximetry, continuous ECG monitoring, capnography, temperature, urinary output. Monitoring of neuromuscular relaxation is important especially when MgSO4 is used for tocolysis because it potentiates nondepolarizing neuromuscular blockade. Additionally these patients need an arterial line for strict blood pressure control and gas analysis (MAC titration). Central venous cannulation is desirable if vasoactive drugs are used.

Nausea, vomiting and maternal hypothermia should be avoided because any straining during and after emergence can cause disruption of the uterine closure leading to amniotic leak.

1.6.

Postoperative analgesia

Adequate postoperative analgesia decreases maternal oxytocin levels and contributes to the prevention of preterm labour. This is usually provided by supplementing general anaesthesia with epidural analgesia. Lumbar epidural catheter is usually placed pre-induction for hysterotomy procedures and is used for providing postoperative analgesia.

2. Foetal anaesthetic aspects of foetal surgery 2.1.

Foetal pain

Clinical and animal research shows that the foetus or neonate is not a little adults and that structures used for pain processing in early development are unique and different from those of adults. Immature pain system uses the neural elements available during each stage of development to carry outs its signaling role. Available scientific evidence show that possibly foetal pain perception occurs well before late gestation, during 2nd trimester. Thalamocortical interactions located in subplate zone, plays an important role in sensory perception. Since there is no objective method for measurement of foetal pain, its estimation depends on evaluation of subjective parameters like stress response and behavioural response. Thus adequate pain relief should be provided to foetus from mid gestation onwards during surgical procedure. Lack of analgesia manifests in later life as altered pain sensitivity and learning disability in later life.11,12 The foetus is at increased risk in foetal surgery due to its immature organ systems, hypothermia, hypovolemia and supsequent hypoperfusion which can lead to foetal hypoxia and death.

2.2.

Foetal anaesthesia and analgesia

Foetal anaesthesia is provided primarily through the transplacental passage of volatile anaesthetics (Table 2). However adequate anaesthetic concentration takes about an hour to reach 70% of the maternal blood levels. Therefore before foetal incision, a cocktail comprising of 10e20 mg/kg fentanyl, 20 mg/ kg atropine and vecuronium 0.2 mg/kg or pancuronium

c u r r e n t m e d i c i n e r e s e a r c h a n d p r a c t i c e 5 ( 2 0 1 5 ) 2 2 e2 5

0.3 mg/kg is injected either intramuscularly or in the umbilical cord to achieve foetal analgesia, immobility and cardiovascular stability.13

2.3.

Foetal monitoring

Before hysterotomy, continuous foetal monitoring can be provided by cardiologist via echocardiography. Once access to a foetal extremity is obtained, a pulse oximeter probe is applied to obtain information regarding heart rate and oxygen saturation. Oxygen saturation value between 60 and 70% is considered normal in a foetus. If foetal thorax is accessible even ECG electrodes can be applied. Foetal arterial and venous blood gas samples may be obtained in prolonged surgical procedures.

2.4.

Effect of pharmacological agents in the foetus

1. Teratogenicity: There is no evidence to show that anaesthetic agents are teratogenic when used in clinical concentrations and doses in pregnant women undergoing surgery.14 2. Neurodevelopmental Consequences: Some animal studies show that exposure of an immature brain to anaesthetic agents can cause neuro-degeneration, decreased spatial recognition, impaired memory and subsequent learning problems.15 However there is only a weak evidence in human studies.16 3. Intravenous induction agents and opioids can decrease foetal heart rate variability but do not lead to foetal morbidity as long as maternal haemodynamic parameters remain stable.17 4. Volatile anaesthetics have direct depressant effects on foetal CVS. Although prolonged or deep maternal inhalation anaesthesia has not been shown to cause foetal hypoxia or acidosis clinically18 higher concentration may result in foetal acidosis.19

3.

Conclusion

Way back in 1543-versalius remarked “Quite pleasing is it, in the management of the foetus, to see how, when he foetus touches the surrounding air and tries to breathe”. In-utero foetal surgery is the site where science fiction becomes real sciences, but maternal safety is of utmost importance and ethical considerations of foetal surgery should be kept in mind.21

Conflicts of interest All authors have none to declare.

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