These conditions, which have yet to be the subject of a CRQ, aren't explicitly mentioned in the curriculum but fall under the umbrella of 'major congenital abnormalities'.
Abdominal wall defects (gastroschisis and exomphalos) occur in between 1 in 3,000 - 10,000 live births
They are often diagnosed antenatally on ultrasound, and are obvious from birth
Ideally, delivery should be in a centre where surgery to repair the abdominal wall defect can be performed
The morbidity and mortality has fallen over the years, with an excellent outcome in 90% of cases
Herniation of bowel without a covering protective membrane through an abdominal wall defect lateral to the umbilicus (usually right-sided)
Felt to arise due a vascular incident involving the omphalomesenteric artery
Once identified, early (∽37 weeks) delivery is encouraged to limit bowel damage from exposure to amniotic fluid
Mode of delivery is often elective section, although no evidence this is superior to vaginal delivery
Epidemiology
Incidence 1 in 3,000
Low maternal age, low parity, maternal smoking, maternal aspirin use and maternal decongestants are associated with increased risk of developing gastroschisis
There is a 3:2 male preponderance
Clinical features
The bowel wall may be thickened, with an inflammatory fibrin 'peel' due to exposure to amniotic fluid
Can also involve herniation of stomach, bladder, uterus or rarely even liver
Associated anomalies
60% of infants are of low birth weight, but other abnormalities are rare
Complications are usually gastrointestinal and include malrotation, volvulus, Meckel's diverticulum, reduced gut motility, intestinal atresia (10-15%) or intestinal stenosis (15%)
Management
Cover the bowel with cellophane to reduce evaporative fluid and heat losses
IV fluids, both maintenance and boluses to accommodate extra losses
NG tube
Maintain nutrition e.g. TPN as full enteral feeding unlikely to be possible for a while (weeks)
Maintain warmth
Antibiotics e.g. co-amoxiclav
Urgent surgery - staged surgery is common
Herniation of bowel with a membranous sac covering and protecting the bowel, through a central abdominal wall defect into an extra embryonal part of the umbilical cord
Occurs due to a failure of the embryonic intestine, which usually migrates through the umbilical ring into the cord in the 6th week of development, to return into the abdominal cavity during weeks 7-11 of development
Once identified, further testing (amniocentesis, foetal echocardiography) should take place to exclude associated anomalies
Delivery at term is allowed, although elective caesarean section is encouraged in exomphalos major to prevent damage to the exposed liver
Epidemiology
Incidence 1 in 5,000 - 13,000
Maternal age often >40yrs
Clinical features
Degree of herniation ranges from:
Exomphalos minor: herniation into umbilical cord through a 5-8cm defect
Exomphalos major: large defect including liver, with pulmonary hypoplasia and poorly developed abdominal & thoracic cavities
The bowel wall itself is normal
The herniated sac frequently contains the liver, spleen and ovaries
Associated anomalies
10% are premature
Associated abnormalities are common (72%)
Cardiovascular (30-40%)
Genitourinary
Chromosomal abnormalities e.g. trisomy 13, 18 or 21
Beckwith-Wiedemann syndrome (10%)
Pentalogy of Centrell
Lower midline syndrome
Management
As the bowel is covered by a sac there is less urgency in management
The sac should be inspected for rupture and protected with saline-soaked gauze
Single stage surgery may be possible, although staged surgery often required for exomphalos major
Conservative management is an option, especially in areas poor surgical access (i.e. allowing the sac to epithelialise with application of antiseptic dessicating agents e.g. silver sulfadiazine)
If the sac ruptures then management is as per gastroschisis
A silastic material or Gore-Tex 'silo' lined with sterile plastic sheeting is sutured to the edge of the fascial defect under GA
The bowel contents lie within the silo, which is intermittently 'tucked' (akin to rolling up the end of a toothpaste tube)
This results in reduction of the bowel contents by gravity over 4-7 days
Once bowel contents are reduced definitive abdominal wall closure takes place, again under GA
A newer, silastic spring-loaded silo has been developed for the management of gastroschisis
It can be inserted and manipulated on NICU without the need for sedation or analgesia
It benefits from reducing exposure of the neonate to multiple general anaesthetics and mechanical ventilation on NICU
It is associated with:
Improved fascial closure rates
More rapid return of bowel function
Fewer ventilator days
Fewer complications
Perioperative management of the child undergoing repair of an abdominal wall defect
Perinatal assessment
Gestational age and birth history inc. birth weight, Apgar scores
Current weight
Check whether received vitamin K
Existing antibiotic regimen or administer if not already given
Ensure NBM
Check for coalescing anomalies
Airway/respiratory assessment
Check for airway difficulties e.g. micrognathia, macroglossia (Beckwith-Wiedemann syndrome)
If already I&V check position (tip aligned with T1/2 vertebrae) and size of existing ETT
If history of I&V anticipate risk of subglottic stenosis and have smaller tubes available
Work of breathing and respiratory rate
Saturations, oxygen requirements and tendency to desaturate
Presence of apnoeas
CXR review inc. ETT and NGT position
Current ventilatory settings and level of support
History of surfactant use
History of infant respiratory distress syndrome
Cardiovascular assessment
Clinical assessment of perfusion, capillary refill, warmth, femoral pulses
Fluid status including maintenance/replacement
HR and BP
Blood gases
TTE
Evidence of congenital cardiac disease
Existing IV access
Ongoing vasoactive drug infusions
Investigations
Bloods
FBC - anaemia increases apnoea risk
U&E - hypocalcaemia increases apnoea risk
Blood gas
Group and cross-match; cross-match 1 unit of blood
CXR
TTE
Renal ultrasound
Cranial ultrasound if premature
Optimisation
Nurse semi-upright
Ensure NGT in situ and aspirated
Reduce evaporative heat, salt and fluid loss by wrapping the abdominal contents in clingfilm
IV fluids; maintenance + replacement
Antibiotics to reduce risk of sepsis
Monitoring and access
AAGBI monitoring
Ideally two IV cannulae in upper limbs - abdominal distension may impair lower limb venous return
Arterial lines may be required in the case of large defects or cardiac comorbidities
NG should already be in situ
Temperature and glucose monitoring often required for optimal neonatal care
Anaesthetic technique
Ensure suitable equipment available e.g. T-piece, straight-blade laryngoscope, burette
Ensure atropine drawn up
Suction NG if present
Pre-oxygenate (often 60 seconds enough to get to an ETO2 of 90%)
IV or gas induction suitable; avoid nitrous oxide to prevent bowel distension
NMBA e.g. atracurium (0.5mg/kg) or cisatracurium (0.15mg/kg)
Maintain muscle relaxation with cisatracurium 2mcg/kg/min to allow reduction of herniated contents
Maintenance with volatile e.g. sevoflurane
Airway and ventilatory management
Size 2.5 - 3.5 cuffed ETT
Cuff inflation with care over pressure to prevent tracheal mucosal injury
Avoid hyperoxia as can cause retinopathy and bronchopulmonary dysplasia in pre-term infants; target SpO2 in mid-90's
Manual ventilation during the period of reduction may be preferable as it allows detection of changing lung compliance
Otherwise ventilate aiming to have a consistent tidal volume and minute ventilation with low airway pressures
Extubation at the end of the case may be possible
Temperature control
High theatre temperature e.g. 27°C
Neonate on warming mattress
Overhead heater
Ensure head covered
Heated and humidified gases
Keep exposed viscera covered with warm swabs
Warmed IV fluid
Cardiovascular and fluid management
Use warmed IV fluids
0.9% NaCl + 10% dextrose at maintenance rate
10-20ml/kg boluses of crystalloid/colloid; anticipate 8-10ml/kg/hr of evaporative losses
Consider 4-5ml/kg packed red cells to maintain Hb ∽12g/dL or once ≥10% total blood volume is lost
Other blood products may include:
Platelets 10mg/kg
FFP 10mg/kg
Cryoprecipitate 5ml/kg
Titrate vasoactive drug infusions as necessary
Analgesia
Caudal epidural or block
Paracetamol IV
Age or wt. (kg)
Dose
Frequency
Max. daily dose
Neonate <32 weeks
7.5mg/kg
8hrly
22.5mg/kg
Neonate >32 weeks
10mg/kg
4-6hrly
30mg/kg
≤10kg
10mg/kg
4-6hrly
30mg/kg
10-50kg
15mg/kg
4-6hrly
60mg/kg
>50kg
1g
4-6hrly
4g
Fentanyl 1-2mcg/kg (or up to 5mcg/kg)
Morphine 25-100mcg/kg, or as an NCA, or as an infusion if ongoing mechanical ventilation
Return to NICU
Patient may be I&V to compensate for reduced lung function due to greater intra-abdominal pressure
If to be extubated at the end, ensure adequate reversal with neostigmine (50mcg/kg)
Ongoing sedation and analgesia:
Morphine 10-20mcg/kg/hr
Paracetamol
Cisatracurium infusion at 3mcg/kg/min if ongoing NMBA is required
Ongoing fluid replacement; ommediately post-op restrict maintenance fluid to 60% of regular level (see fluid management page)
Standard neonatal care; temperature maintenance, glucose control
TPN often required due to prolonged ileus
Abdominal compartment syndrome
Abdominal compartment syndrome can occur if the abdominal contents are reduced under excessive pressure, particularly in exomphalos major
This causes:
Impaired ventilation due to cranial shift of the diaphragm
Reduced abdominal organ blood flow potentially causing gut necrosis and intestinal vascular injury
Reduced renal perfusion causing oligo-anuria
Reduced hepatic perfusion and hepatic impairment
Impaired lower limb perfusion
Management involves reducing the pressure in the silo
Other GI complications
Skin necrosis and secondary tension if the abdominal wall is closed under significant tension