Neonatal anaesthesia: Difference between revisions

 

It is important to prepare and check all equipment that may be required, prior to the start of anaesthesia (see Figure 1).

environment where the facilities and expertise are available for definitive treatment and on-going care. In certain situations, if the baby is unstable and not suitable for transfer to theatre, it may be necessary to undertake surgery on the NICU itself. In certain situations the baby may need to be transferred to a specialist centre. In low-income countries this may not be an option and treatment may not always be possible. Prior to transfer the appropriate personnel, equipment, drugs and fluids should be prepared and checked using a transfer checklist (Table 6). The neonate should be carefully assessed for stability for transfer or if necessary transfer may need to be delayed for further resuscitation and optimisation. Check that the monitoring is functional and the patient is adequately fluid resuscitated. Take time to ensure that the neonate is stable prior to transfer on the current drug infusions and mode of ventilation. Careful monitoring during transfer is extremely important and will highlight clinical trends. A detailed handover is essential for good continuity of care.

 

 

=== inguinal hernia repair ===

Inguinal hernia is common in premature neonates. The timing of surgery depends on the risk of incarceration, bowel strangulation or testicular atrophy versus the risk of postoperative apnoea and the potential harm to neurodevelopment. The major anaesthetic risk is post- operative apnoea, which has been shown to vary from 4.7% to 49% of patients.10,14 Some units prefer spinal anaesthesia for inguinal hernia repair, others use a balanced anaesthetic technique using general anaesthesia with intubation, supplemented with a regional technique. There is currently not enough evidence to show whether the incidence of apnoea is lower using spinal anaesthesia, and the choice is usually determined by local preference of the surgeon and anaesthetist.15

 

 

Caudal anaesthesia using 0.25% bupivacaine 0.75ml.kg-1 provides excellent supplementary analgesia for inguinal hernia repair under general anaesthesia. Alternatively, an ilioinguinal block can be performed with 0.5-1.0ml.kg-1 0.25% bupivacaine. These patients may require post-operative apnoea monitoring dependent on their PCA, as discussed earlier, and some premature infants will require post-operative ventilation or CPAP for treatment of apnoea. Paracetamol (7.5mg.kg-1 IV or 20mg.kg-1 rectal suppository) provides adequate post- operative analgesia

=== Anorectal malformations ===

Anorectal malformations (ARM) occur in approximately 1:5000 live births. They represent a wide spectrum of disease, from a simple membrane involving the distal rectum and anus to more complex anomalies involving the genital and urinary tract. Spinal anomalies are frequently found in these patients. These include spinal dysraphism, low lying cord (LLC) and tethered cord.16 Plain spinal Xrays and spinal ultrasound are used to screen for these abnormalities although they may be normal in occult dysraphism. Caudal anaesthesia may be beneficial and can be used in ARM if there is certainty that anomalies of the spine and spinal cord have been excluded.17 ARM may be associated with other anomalies including Vertebral, Anorectal, Cardiac, Tracheoesophageal, Renal and Limb abnormalities, collectively known as the VACTERL association.

Primary surgical repair can be undertaken in the neonatal period although more commonly a colostomy is performed and a definitive repair is carried out at a later date. If caudal anaesthesia is contraindicated an opioid-based technique is used (fentanyl 1-2mcg.kg-1 or morphine 20-50mcg.kg-1 [0.02-0.05mg.kg-1], with infiltration with local anaesthetic. Rectal suppositories cannot be used but intravenous paracetamol is a useful adjunct if available. Standard monitoring is usually all that is required. Opioids should be carefully titrated as the usual aim is to extubate at the end of surgery. The patient may be positioned supine or prone depending on the surgical technique. Prone positioning is associated with increased risk to pressure areas, abdominal compression resulting in difficulty with ventilation, endobronchial intubation or tracheal tube displacement. Long-term outcome is variable depending on the complexity of the anorectal malformation. These patients usually require serial anal dilatations following repair.

=== Intestinal malrotation ===

Malrotation occurs in approximately 1:500 live births. Normal intestinal rotation around the superior mesenteric artery (SMA) and fixation during foetal development is interrupted. It may also be associated with congenital diaphragmatic hernia, exomphalos and gastroschisis. Nearly 50% of cases will present in the first week of life most commonly with bilious vomiting secondary to duodenal obstruction.18 This may be due to a midgut volvulus, or physical compression secondary to peritoneal tissue bands or abnormal locations of the duodenum and its surrounding structures. If the condition is diagnosed early the neonate  

secondary to perforated or necrotic bowel. The gold standard radiological investigation is an upper GI contrast series. Plain X-rays are useful if there is concern of another diagnosis or to exclude visceral perforation. These patients require adequate volume resuscitation and electrolyte replacement for ongoing fluid losses and should be taken to theatre as soon as is feasible. A nasogastric tube is inserted to suction the stomach. Prophylactic antibiotics such as co-amoxiclav or benzylpenicllin, gentamicin and metronidazole are required. Ideally invasive monitoring is inserted although it should not delay surgery in the sick neonate. If the gut has been compromised, inotropes may be needed and any coagulopathy will require correction. A central venous line may be required for ongoing total parenteral nutrition in the septic neonate. An opioid based technique can be used although a caudal may be considered if the patient is haemodynamically stable, there are no other contra-indications and extubation is anticipated. Post-operative NICU care and ventilation is often necessary. Long-term outcomes depend on the extent of the necrotic bowel. Some patients will develop short bowel syndrome and if there is extensive bowel necrosis the mortality is 100%.

=== Necrotising enterocolitis (NEC) ===

Necrotising enterocolitis occurs in approximately 0.5 – 5:1000 live births. More than 90% of infants diagnosed with NEC are preterm.19 Morbidity and mortality are inversely proportional to the infant’s post-conceptual age (PCA) and birth weight. The aetiology of NEC is multifactorial. Risk factors include vascular compromise of the gastrointestinal tract, commencement of enteral feeding, immature gastrointestinal immunity and sepsis. Hypoxia or ischaemia combined with reduced splanchnic blood flow can occur with patent ductus arteriosus (PDA), cyanotic heart disease, respiratory distress syndrome, shock, asphyxia and with the use of umbilical catheters. NEC may present with subtle gastrointestinal signs including abdominal distension, intolerance of feeds, abdominal tenderness, blood in the stool and bilious vomiting or may present with perforation and peritonitis with systemic signs including shock, temperature instability, acidosis and disseminated intravascular coagulopathy. Supine and decubitus plain Xrays may show the presence of hepatic venous gas, free intraperitoneal air, dilated bowel loops, ascites and asymmetric bowel gas patterns along with pneumatosis intestinalis. Initial management includes discontinuation of enteral feeds, insertion of a nasogastric tube and commencement of broad-spectrum antibiotics such as benzylpenicillin, gentamicin and metronidazole. Ongoing fluid and electrolyte management with parenteral nutrition will be required. Frequent clinical monitoring of systemic and abdominal signs together with radiographic examination, monitoring of laboratory values and acid-base status guides further management. The only absolute indication for surgery is bowel perforation although the decision to proceed to surgery may be made if there is a clinical deterioration. The preoperative assessment should evaluate and optimise any cardiovascular instability, metabolic acidosis, coagulopathy and respiratory compromise. If the patient is too unstable it may be necessary to carry out surgery on the NICU. These patients are often already intubated and ventilated. A high dose fentanyl technique (10-20mcg.kg-1) may be used to promote cardiovascular stability and reduce the systemic stress response.20 Nitrous oxide should be avoided because of the risk of bowel distension. Low cardiac output state, organ hypoperfusion and acidosis secondary to large fluid shifts is common, and large volumes of intravenous fluids are frequently required. Invasive monitoring is useful to guide fluid management and allow frequent arterial blood gas sampling although this must be balanced against the risk of limb ischaemia in the preterm neonate. Insertion of an arterial or a central line should not delay the start of surgery in the sick infant. There is a significant risk of coagulopathy and significant blood loss, and inotropes are often required. Packed red cells should be available and fresh frozen plasma and platelets are often indicated based on laboratory results or clinical evidence of bleeding. Hypothermia and glucose instability are common and should be managed appropriately. Mortality remains significant and long term complications include short bowel syndrome and neurodevelopmental delay.

=== Oesophageal atresia and tracheoesophageal fistula ===