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Anaesthesia for surgery in infancy
NEONATAL ANAESTHESIA
Anaesthesia for surgery in infancy
Learning objectives After reading this article, you should be able to: C describe general surgical conditions encountered in infancy and their surgical approach C understand the anaesthetic and physiological implications of these conditions C describe anaesthetic principles and techniques of general surgical conditions in infants C understand the physiological changes and anaesthetic implications observed during minimally invasive surgery in infancy
Graham Knottenbelt Amanda Dalton
Abstract Specialist surgery in infancy provides challenges for paediatric anaesthetists. There is growing appreciation that the relatively higher rate of severe critical events in infants during the perioperative period requires appropriate competence, experience and resources for the safe conduct of anaesthesia. Both common (inguinal hernias and hypertrophic pyloric stenosis) and less common conditions (tracheo-oesophageal fistula, congenital diaphragmatic hernia, exomphalos, gastroschisis, and congenital lobar emphysema) require a sound understanding of the relevant pathology and the particular issues that may be encountered in these infants. In the last decade there has been a rise in the number of procedures in infancy being performed with a minimally invasive technique and this has a wide range of implications for anaesthesia.
approach will mandate a general anaesthetic rather than a regional technique. Anaesthetic technique The conduct of anaesthesia and choice of analgesia is patientdependent. A summary of the available options is included in Table 1. Some practitioners consider it is reasonable to use regional technique in ex-premature infants because of the lower incidence of apnoea in PACU compared with general anaesthesia. Babies with a history of extreme prematurity (<26 weeks) and those with significant comorbidities (e.g. neurological abnormalities) may benefit more from a regional technique than otherwise healthy babies.
Keywords Congenital diaphragmatic hernia; duodenal atresia; exomphalos; gastroschisis; infantile inguinal hernia; laparoscopy; necrotizing enterocolitis; pyloric stenosis; thoracoscopy; tracheooesophageal fistula
Postoperative apnoea in the neonate Neonatal apnoea is defined as a pause in breathing for more than 15 seconds, or more than 10 seconds if associated with desaturation or bradycardia. The clinical significance of brief selflimiting apnoea is unclear. Increasing prematurity is the biggest risk factor for apnoea. The risk is further compounded by anaesthesia and sedation, even in neonates without a history of apnoea (Box 1). Recent analysis of data from the GAS study, a large randomized controlled trial comparing awake regional anaesthesia with general anaesthesia in infants having inguinal hernia repair,2 reported an incidence of apnoea of 6.1% in preterm infants compared with 0.3% in term infants. Most apnoea occurred early (in the first 30e60 minutes after surgery) but they were also reported in the first 12 postoperative hours. While early apnoea was less frequent after regional anaesthesia, there was a similar incidence of late apnoea in both groups. Furthermore, there was occasional life-threatening apnoea in all babies irrespective of the method of anaesthesia. These findings reinforce the importance of postoperative apnoea monitoring in this cohort. A safe approach is to admit all ex-premature babies of less than 60 weeks postmenstrual age overnight for apnoea
Royal College of Anaesthetists CPD Matrix: 2D02, 3D00
Inguinal hernia in infancy Repair of inguinal hernia is one of the most common operations in paediatric surgery. Hernias can occur in term infants, however the incidence increases in babies of increasing prematurity. It is preferable that the surgery be performed electively, with the risk of incarceration increasing if the hernia is left untreated. Surgery The open procedure is relatively quick (approximately 30 min per side), and involves ligating a patent processus vaginalis into which herniation has occurred. The procedure can also be performed laparoscopically, even in small or premature infants or when the hernia is incarcerated.1 Unilateral hernia repair is likely to be faster when performed as an open procedure, but the main proposed benefit of a laparoscopic approach is that it allows exploration of the contralateral side, and ligation of a second patent processus vaginalis if present. This prevents later presentation with a hernia on the contralateral side. A laparoscopic
Risk factors for postoperative apnoea in the neonate C C
Graham Knottenbelt MB BCh FRCA FANZCA FHEA is a Consultant Paediatric Anaesthetist at Starship Children’s Hospital, Auckland, New Zealand. Conflicts of interest: none declared.
C C
Amanda Dalton MB ChB FANZCA MBioethics is a Consultant Paediatric Anaesthetist at Starship Children’s Hospital, Auckland, New Zealand. Conflicts of interest: none declared.
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C
Reduced age Lower gestational age at birth (incidence 7% at 34e35 weeks, 13% in those born <32 weeks’ gestation, 80% in <30 weeks) Lower weight (incidence 30% in those with birth weight <1000 g) Comorbidities (neurological, respiratory) History of apnoea
Box 1
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Anaesthesia options for inguinal hernia surgery in infancy Type of anaesthetic Doses/Techniques
Advantages
GA
Familiarity Increased risk of early apnoea (first 30 min Good surgical conditions postoperatively) (no crying/agitation from baby)
Awake spinal
Caudal
Inhalational induction with sevoflurane ETT or LMA can be used Best accompanied by caudal for analgesia which will reduce anaesthetic requirements Secure IV access prior to spinal insertion Perform awake in left lateral position with assistant Strict asepsis Use short 25 g needle, e.g. 0.1 ml/kg of 0.5% bupivacaine Oral sucrose may be useful to help settle infant Good analgesic supplement, aim to block to T10, 1 ml/kg of 0.2% ropivacaine or levo-bupivacaine Can be used as sole anaesthetic in awake patient
Disadvantages
Lower rate of early apnoea No airway manipulation Early feeding
High failure rate (20%) Potential for distressed or crying baby. Requires technical expertise Less surgical time allowable e 45 min Upper body movement may be problematic for surgeon, especially if infant >5 kg
Generally well tolerated Technically easier than spinal
Slower onset (15e20 min) Motor block less reliable than with spinal (if sole anaesthetic) Higher LA dose and risk of toxicity
GA, general anaesthetic; LA, local anaesthetic; LMA, laryngeal mask airway.
Table 1
starting fluid maintenance (10e20 ml/kg boluses of saline balanced salt solution). Depending on the initial electrolyte results, potassium may be required as well. Maintenance fluid consisting of normal saline with 5% or 10% glucose and 10 mmol/L of KCl should be commenced at a rate of 100 ml/kg per day. A solution containing chloride is required as this provides the kidney with the means to excrete bicarbonate thus correcting the alkalosis. Oral feeds should be ceased once diagnosed and a nasogastric tube inserted. Nasogastric losses should be recorded and replaced with intravenous normal saline.3 The criteria determining suitability for surgery are summarized in Box 2. It is generally recommended to aim for correction of alkalaemia due to concerns around postoperative apnoea in babies with a high bicarbonate concentration.
monitoring irrespective of the anaesthetic technique. Term infants should be admitted overnight if <44 weeks post-conception age but will otherwise be suitable for day surgery. It is good practice to observe a period of 12 hours without an apnoea prior to discharge.
Hypertrophic pyloric stenosis Pyloric stenosis occurs in 1e5:1000 live births and is characterized by thickened muscle at the level of the pylorus leading to gastric outlet obstruction. It is five times more likely in males, and usually presents at 2e8 weeks of life in otherwise healthy term infants. The baby will present with progressive non-bilious vomiting which may become projectile, and eventually leads to severe dehydration if prolonged. There may be an ‘olive’ palpated in the epigastrium and the diagnosis is usually confirmed with an ultrasound (95% sensitivity) to assess pyloric thickening. The characteristic biochemical profile is due to the loss of acidic gastric secretions and dehydration resulting in a hypochloraemic hypokalaemic metabolic alkalosis. Perioperative morbidity and mortality is now very low due to a good understanding of the pathophysiology, appropriate preoperative optimization and a refined surgical approach.
Surgery Surgical correction is brief (generally less than 30 minutes) and involves either open or laparoscopic incision of the pylorus down to the mucosa to relieve the obstruction. The open procedure,
Guidelines before pyloromyotomy C
Preoperative optimization Pyloromyotomy is never an emergency procedure and should only be performed once the baby has been fully resuscitated and electrolytes correction is underway. Babies with moderate to severe dehydration will initially need to be resuscitated before
C C
Adequate fluid resuscitation with no clinical signs of dehydration. Serum chloride >100 mmol/l Serum HCO3 <30 mmol/l Na >130 mmol/l K >3 mmol/l
Box 2
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are usually detected before birth, which facilitates management by a multidisciplinary team in a specialist centre. Gastroschisis is usually a small (2e3 cm) para-umbilical defect located to the right of the umbilicus through which the small bowel herniates. There is no sac or covering over the bowel, which is exposed to the amniotic fluid in utero and may be in inflamed, oedematous and functionally abnormal as a result. Associated anomalies are rare, except for intestinal atresia which may be seen in up to 10% of children. By contrast, exomphalos (omphalocoele) is often a larger central defect with a herniation of bowel and abdominal organs into a membranous sac originating from the umbilical cord. The defect may contain small bowel, liver, spleen, colon and occasionally gonads. This covering may rupture during delivery. There is a high rate of associated anomalies with fewer than 20% of neonates having an isolated lesion. Common associations include trisomies (13, 18, 21), and syndromes such as BeckwithWiedemann syndrome (macroglossia, visceromegaly, hypoglycaemia) and pentalogy of Cantrell. Cardiac defects are common (atrial and ventricular septal defects, tetralogy of Fallot, transposition of the great vessels) as are renal defects. All babies with exomphalos should have an echocardiogram and renal ultrasound after birth.
also known as the Ramstedt pyloromyotomy, involves a right upper quadrant transverse incision or a peri-umbilical incision. The laparoscopic procedure has been advanced in the last two decades with proponents citing reduced hospital stay and better cosmesis. Which approach is better remains controversial as there are some reports that the laparoscopic approach may have a higher rate of perforation and incomplete division of the stenosis. A meta-analysis found no significant difference in the rate of incomplete incision, mucosal perforation and reoperation between open and laparoscopic groups.4 Anaesthetic technique It is important to ensure the stomach is as empty as possible by inserting a large-bore (e.g. 14 Fr) nasogastric/orogastric catheter and suctioning out any remaining gastric contents. Traditionally, gastric contents were aspirated with the baby supine, prone and lying on each side to ensure as much volume as possible is removed. An intravenous induction with a modified rapid sequence induction (RSI) and intubation is usual, though many accept gas induction with sevoflurane. The baby should be preoxygenated wherever possible prior to induction. The nasogastric tube may need to be re-inserted after induction as the surgeon will often check the integrity of their anastomosis by asking for an injection of air into the stomach to put the repair under tension. Pyloromyotomy is not a particularly painful procedure and can comfortably be managed with paracetamol and local anaesthetic around the incision or at the port sites.5 The infant should be extubated awake and breathing monitored postoperatively as they may be slow to resume spontaneous ventilation due to the raised bicarbonate concentrations in the CSF that may be slow to return to normal.
Surgery The ultimate surgical goal for these abdominal wall defects is to reduce the evisceration and achieve abdominal closure. Survival from uncomplicated gastroschisis is around 95% if managed appropriately in a specialist paediatric centre; however, the high rate of associated comorbidities with exomphalos means survival is not as favourable. Neonates with gastroschisis have longer duration of parenteral nutrition, longer hospital stay and a higher rate of sepsis, but there is still a higher mortality in babies with exomphalos.6 Initial management of gastroschisis should include immediate protection of exposed bowel with clear plastic to reduce heat and fluid loss, and a sterile occlusive dressing in the case of exomphalos. There will need to be on-going assessment for bowel ischaemia. Some centres advocate nursing in the right lateral position to prevent vascular injury from mesenteric kinking, and it is also possible to develop a volvulus. A nasogastric tube is inserted soon after birth to decompress the bowel. More definitive bowel covering, be it primary closure or application of a silo, should occur within 8 hours, and should be expedited where there is obvious bowel ischaemia. In the case of silo application, bowel is placed in a suspended plastic tube that is gradually reduced in size so as to allow the intestines to slowly return to the abdominal cavity over 7e10 days (usually once or twice daily reductions) (Figure 1). This can be done in NICU without general anaesthesia.
Duodenal atresia Congenital duodenal atresia occurs in 1:6000 infants, presenting with bilious vomiting in the first day or two of life. Duodenal atresia is associated with multiple congenital abnormalities (up to 50e70%) including trisomy 21, cardiac anomalies and VACTERL. Diagnosis can be made antenatally or postnatally with ultrasound and X-ray may show a typical ‘double-bubble sign’. Surgery Laparotomy or laparoscopy is performed and a duodenoduodenostomy bypass anastomosis procedure done. Prognosis after successful surgical treatment of duodenal atresia is excellent with morbidity primarily related to associated abnormalities. Anaesthetic technique Priority should be given to fluid and electrolyte imbalance correction prior to anaesthesia. The neonate should be fluid resuscitated prior to surgery and nasogastric tube aspirated. An intravenous induction with a modified rapid sequence induction (RSI) and intubation is usual. Analgesia can be provided with subcostal block, epidural or morphine infusion.
Anaesthetic technique The nasogastric tube should be aspirated prior to induction. General anaesthesia with neuromuscular blockade (often modified RSI), intubation and positive pressure ventilation is usual. There is often large volume fluid losses intraoperatively and continual assessment of fluid loss is necessary. Abdominal closure can be complicated by markedly higher intra-abdominal pressure; high ventilation pressures >30 cmH2O, haemodynamic compromise (dropping MAP despite fluid boluses), oliguria,
Gastroschisis and exomphalos Exomphalos and gastroschisis are the two most common congenital abdominal wall defects, both having an incidence of 1e5:10,000 live births. With the advent of advanced antenatal scanning these defects
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Anaesthetic technique These babies are some of the sickest a paediatric anaesthetist may encounter. The neonate will require intubation, paralysis and ventilation. Haemodynamic instability is common with large volume replacement (including blood, platelet and factor transfusion) and inotropic support often required. Close attention should be given to the temperature of the baby as heat loss may be significant. Frequent blood gases should be obtained if possible, with particular attention to acid-base status, haemoglobin, coagulation, calcium and glucose.
Tracheo-oesophageal fistula and oesophageal atresia Tracheo-oesophageal fistula (TOF) is a congenital defect that occurs in 1:4000 live births. It consists of a variable combination of oesophageal atresia and an abnormal fistula between the oesophagus and the trachea. The most common variant is an oesophageal atresia with a blind upper pouch and a distal fistula connecting the trachea to the distal portion of the oesophagus (Figure 2). The diagnosis may be made antenatally, or will present soon after birth with excessive oral secretions due to saliva pooling in the blind pouch, choking episodes on feeding and an inability to pass a nasogastric tube. The nasogastric tube will characteristically appear coiled in the upper pouch on a chest Xray and air in the stomach will confirm the presence of a fistula. There is a higher rate of prematurity and at least 50% of babies with a TOF will have another anomaly including cardiac defects, VACTERL (vertebral defects, anal defects, tracheo-oesophageal, renal and limb malformations), other gastrointestinal anomalies (imperforate anus, duodenal atresia) and urogenital defects. The most common cardiac defects are ventriculoseptal defects and tetralogy of Fallot. Cardiac defects, low birth weight and prematurity are associated with higher mortality; however, survival is now greater than 90%.
Figure 1 Silo bag containing gastroschisis.
metabolic acidosis, or intra-abdominal pressures >15 mmHg are considered abnormal and will necessitate a change of surgical approach if this occurs. Postoperative neonates are usually returned to an ICU intubated with mechanical ventilation. Extubation can be considered after surgery if the defect is small, there is adequate intraoperative analgesia, no signs of raised intra-abdominal pressures, and ventilation is stable with minimal support. Central venous access is usually required within the first few days as infants are likely to require a period of parenteral nutrition. Postoperative complications include necrotizing enterocolitis, intra-abdominal sepsis and ileus.
Surgery The neonate is kept nil by mouth and a Replogle tube is inserted into the upper oesophageal pouch in order to continuously suction pooling saliva. The prone position is commonly adopted. Surgery is ideally performed within 24 hours of diagnosis to prevent soiling of the lungs by saliva or stomach acid. The procedure is usually performed via a right thoracotomy but can also be performed thoracoscopically. The first step is to identify and ligate the fistula, and then the two ends of the oesophagus are anastomosed. This may not be immediately possible if there is a long gap between the proximal and distal oesophagus in which case a gastrostomy will be required so that enteral feeding can commence. Thoracoscopic repair of TOF was first performed in 1999 and has had widespread uptake since. There is conflicting evidence as to whether hospital stay, pain scores, time to full feeds and complication rates are better with a thoracoscopic approach. The thoracoscopic approach is associated with an improved cosmetic outcome and possibly lower rates of late scoliosis.
Necrotizing enterocolitis Necrotizing enterocolitis (NEC) is a condition seen in premature neonates in whom there is inflammation, necrosis and sometimes perforation of the bowel wall. There is a wide variation in severity, from relatively mild localized disease that can be managed conservatively to severe widespread disease with shock and an associated high mortality. Presenting features include signs of sepsis, progressive abdominal distension, bilious vomiting or nasogastric aspirates, bloody stools, and a characteristic finding of intramural gas on an abdominal X-ray. Surgery Non-operative management involves ceasing enteral feeding, broad-spectrum antibiotics and general supportive measures such as inotropes and ventilator support. Operative surgery involves either peritoneal drainage or laparotomy with bowel resection and possibly stoma formation.7 Surgery is required when there is clinical deterioration despite maximal medical therapy, or when there is evidence of free air in the abdomen.
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Anaesthetic technique Table 2 summarizes problems that can occur during anaesthesia for TOF. It is generally considered safe to use an inhalational induction with oxygen and sevoflurane. This allows the infant to
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morbidity and mortality in this condition. The pulmonary arteries have thickened walls and a reduced cross-sectional area leading to increased pulmonary vascular resistance and a high risk of developing pulmonary hypertension. Survival improves where treatment is directed towards managing the pulmonary hypoplasia and the associated pulmonary hypertension. Secondary injury from aggressive mechanical ventilation is also a cause of morbidity and mortality. Approximately 50% of babies will have associated anomalies including congenital heart defects (very common), spinal abnormalities and chromosomal anomalies. Prognosis is worse with left-sided or bilateral hernias, where there are associated anomalies, where there is liver herniation and where there is an observed:expected lung head ratio (O/E LHR) of <28%. There is a high rate of chronic lung disease and gastrointestinal problems in survivors (up to 50%).
Gross classification and incidence of tracheo-oesophageal fistula
b
a
d d
c c
Preoperative management A period of stabilization prior to repair is preferable and conveys a mortality benefit. Investigation should include echocardiogram to exclude congenital heart defects and assessment of the right ventricle. Management involves early intubation, avoiding stomach or bowel in the chest being distended with gas, and ventilation with airway pressures below 25 cmH2O. Central and arterial access will facilitate fluid resuscitation, inotropes and parenteral feeding. If higher airway pressures are required, high-frequency oscillatory ventilation (HFOV) is considered with permissive hypercapnoea (PaCO2 45e55 mmHg), although support for this technique is weak. Extracorporeal membrane oxygenation (ECMO) has been used in the past to manage resistant respiratory failure and pulmonary hypertension, however a survival benefit is not proven and the use of ECMO continues to be debated. Sildenafil and inhaled nitric oxide (NO) can be useful for treating pulmonary hypertension.
e e
(a) Oesophageal atresia (OA) (Gross classification: A. Vogt classification: 1. Approximate frequency 10%). (b) Proximal tracheo-oesophageal fistula (TOF) with distal OA (Gross: B. Vogt: 3A. Approximate frequency 1%). (c) Distal TOF with proximal OA (Gross: C. Vogt: 3B. Approximate frequency 85%). (d) Proximal TOF and distal TOF (Gross: D. Vogt: 3C. Approximate frequency 1%). (e) TOF without OA or ‘H’-type TOF (Gross: E. Vogt: 2. Approximate frequency 3%)
Figure 2
continue to breathe spontaneously and if problems with positive pressure ventilation become apparent there is more control, as well as the opportunity to revert back to spontaneous ventilation. A bronchoscopy may be performed to assess the location and size of the fistula, as well as the presence of multiple fistulas (Figure 3). If the fistula is distal or particularly large then an attempt can be made to occlude the fistula by way of a balloon catheter (e.g. Fogarty); this may be done with the help of a fibreoptic scope through a laryngeal mask.8,9 Alternatively an ETT could be inserted, positioning the tip below the fistula with the aid of a fibreoptic bronchoscope, after which positive pressure ventilation can be initiated at low pressures. It is impractical to attempt to maintain spontaneous ventilation throughout the whole operation, particularly if performed thoracoscopically. The baby is routinely returned to intensive care intubated, paralyzed and ventilated, although the use of an epidural has been used to facilitate early extubation. Oesophageal strictures requiring recurrent oesophageal dilatation. Gastro-oesophageal reflux and tracheomalacia are common long-term complications.
Surgery The procedure can be performed either open or thoracoscopically.10 Open procedure involves a subcostal incision in order to return the herniated organs to the abdomen with either a primary or patch repair of the defect in the diaphragm. The recurrence rate is higher after a minimally invasive thoracoscopic approach.11 The frequently prolonged nature of the thoracoscopic procedure means that extreme hypercapnia and severe respiratory acidosis have been reported,12 worsening a pre-existing pulmonary hypertension disposition. Anaesthetic technique The most appropriate location for surgery will depend on the stability of the baby and any advanced therapies in place (e.g. ECMO and HFOV). A nasogastric tube is essential to keep the stomach and bowel deflated. An arterial line (ideally pre-ductal) and central venous line is extremely helpful. There are two main intraoperative aims: avoidance of pulmonary hypertension and reduction of barotrauma. Neuromuscular blocking drugs should be used and ventilation with airway pressures as low as possible, allowing permissive hypercapnia and increasing respiratory rate rather than increasing pressures.
Congenital diaphragmatic hernia Congenital diaphragmatic hernia (CDH) is a birth defect occurring in 1:3000 live births. It consists of a herniation of abdominal viscera into the thorax through a defect in the diaphragm, often in combination with abnormally developed lungs (Figure 4). A left-sided hernia is present in 80% of cases, but can be bilateral or right-sided. Herniated organs can include small and large bowel, stomach, liver and spleen. The mass effect in the thorax prevents normal lung development and it is the resulting pulmonary hypoplasia and abnormal vasculature that lead to
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Critical problems that can occur in anaesthesia in TOF/OA repair Issue
Implications
Management
Risk of anomalies, most importantly cardiac
May have right sided aortic arch / necessitates left thoracotomy instead of usual right sided approach May be prone to significant intraoperative instability. Cardiac problems may be compounded by acid-base changes and intraoperative fluid shifts/blood loss Gas can enter the stomach with positive pressure ventilation causing gastric distension and restriction of ventilation. Higher risk in those with poorly compliant lungs and with carinal, large or multiple fistulas Intubation of fistula and ventilation of stomach is possible
Preoperative ECHO is routine Arterial line is extremely useful and central venous access optimal if there are known cardiac issues
Inadequate pulmonary ventilation and ventilation through TOF
Intraoperative compression of trachea and great vessels
May have transient difficulties with ventilation Sudden blood pressure swings are common
Attempt can be made to maintain spontaneously ventilation until the position of the fistula is identified and ligated Ventilate with as low a pressure, accepting hypercapnoea if necessary Bronchoscopy will identify size and site of fistula. Position ETT distal to fistula if possible or occlude fistula with Fogarty catheter Can perform deliberate endobronchial intubation to bypass the fistula In extremis, the surgeon can perform a gastrostomy to decompress the stomach Close communication with the surgeon is essential Hand ventilation may be easiest at some critical stages Arterial line and central line helpful especially if inotropes are required
Table 2
The neonate commonly needs at least 24 hours of ventilation postoperatively. There will be a pneumothorax as the hypoplastic lung will only partially fill the vacated thoracic cavity and this will slowly resolve over several weeks as the lung expands and fluid fills the cavity. It is possible to have a postoperative pulmonary hypertensive crisis during which hypoxia and acidaemia can worsen ventilation considerably.
insufflation leading to an increase in intra-abdominal pressure (generally <10 mmHg). Physiological effects: Ephalad displacement of the diaphragm restricts lung excursion, leading to a reduced functional residual capacity (FRC), reduced lung compliance and increased airway resistance. Infants have a high closing capacity relative to FRC, which makes them more prone to collapse of dependent airways and atelectasis. In addition, oxygen saturations may be compromised due to impaired ventilation-perfusion matching. Hypercarbia may be pronounced in infants due to more rapid absorption of CO2 into the blood; this in turn requires a higher
Minimally invasive surgery in infancy In recent years there has been considerable growth in the number of surgical procedures in infancy being performed using laparoscopic or thoracoscopic minimally invasive techniques. Benefits may include improved cosmetic outcomes, reduced postoperative pain, reduced musculoskeletal damage and quicker recovery, but there are particular challenges for the anaesthetist and thus a good understanding of the accompanying physiology and its anaesthetic implications is important. Laparoscopy Procedures suitable for a laparoscopic approach include orchidopexy, pyloromyotomy, inguinal hernia repair, laparoscopicassisted pull-through for Hirschsprung’s disease, duodenal atresia repair/stoma formation and exploratory laparoscopy for acute abdomen. A pneumoperitoneum is achieved using CO2
Figure 3 Bronchoscopic view of TOF.
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should be notified if there are problems not improved by adjusting the ventilation. Effective neuromuscular blockade will improve ventilation and will allow lower insufflation pressures. The anaesthetist should be wary of the ETT migrating caudad due to the increased intra-abdominal pressure. Thoracoscopy Thoracic surgery in infants may be through an open thoracotomy or using video-assisted thoracoscope (VATS). In open procedures the surgeon generally retracts and collapses the lung, and no formal lung isolation is undertaken by the anaesthetist. Unlike in adults, this is possible and well-tolerated in infants due to more elastic and generally healthier lung tissue. Thoracoscopic surgery is now being used even in very small babies (Figure 5). Procedures that can be performed thoracoscopically include TOF/ oesophageal atresia repair, lung resection for congenital anomalies, congenital diaphragmatic hernia repair and ligation of patent ductus arteriosus. The proposed benefits of a thoracoscopic approach over open surgery are broadly the same as those for laparoscopic surgery and include reduced pain, better cosmesis and shorter hospital stay. There is also some evidence that there is a lower incidence of late musculoskeletal complications in thoracoscopic surgery, as demonstrated by a higher rate of chest wall deformity and late scoliosis in infants who have had open thoracotomy.14 To perform a procedure thoracoscopically, CO2 is insufflated into the pleural space to achieve good surgical access and visualization. Although this is easier when one-lung ventilation is achieved, that can be challenging in babies due to their small size and limitations on the equipment available. For this reason, lung isolation should always be attempted with the caveat that a perfect result may not always be achievable.
Figure 4 X-ray showing congenital diaphragmatic hernia. Note presence of ETT and umbilical venous and arterial lines.
minute ventilation by way of higher inflation pressures and respiratory rate using positive pressure ventilation. Cardiovascular responses are variable, but derangements are unusual with insufflation pressures less than 10 mmHg. If higher pressures are needed (>15 mmHg) and the patient is unwell or hypovolaemic, the reduced venous return from inferior vena cava compression may cause a reduction in cardiac output and hypotension. Rarely, cardiovascular collapse has been described that has been attributed to gas embolism with initiation of the pneumoperitoneum.13 Particularly small or premature babies may not be suitable for laparoscopic surgery as they may tolerate the physiological effects of a pneumoperitoneum poorly.
Physiological effects: The degree of hypercapnia and hypoxia observed in thoracoscopic surgery is likely to be greater than it is during open surgery.12 Some infants will have healthy lungs and will therefore tolerate one-lung ventilation better than adults; however, hypoxia can still be marked due to their increased oxygen consumption and hypoxic pulmonary vasoconstriction. Both of these factors magnify ventilation/perfusion mismatching and a high FiO2 will sometimes be required to overcome this. Other physiological derangements include hypercapnia, hypotension and respiratory acidosis. It is rare for thoracoscopic procedures to cause hypotension from compression of the great
Anaesthetic technique: The use of cuffed endotracheal tubes will prevent problems arising from a leak around the endotracheal tube. PEEP of 3e8 cmH2O is likely to be useful to offset any hypoxia and the occasional manual recruitment breath will help to re-expand collapsed dependent lung units and improve oxygen saturations. Release of the pneumoperitoneum will usually reverse any refractory respiratory compromise, and the surgeon
Figure 5 (a) Thoracoscopic positioning and (b) thoracoscopic ports.
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vessels or mediastinal shift in babies, mainly because low insufflation pressures (<10 mmHg) are usually adequate to provide good surgical conditions.
3 Kamata M, Cartabuke RS, Tobias JD. Perioperative care of infants with pyloric stenosis. Pediatr Anesth 2015; 25: 1193e206. 4 Costanzo CM, Vinocur C, Berman L. Postoperative outcomes of open versus laparoscopic pyloromyotomy for hypertrophic pyloric stenosis. J Surg Res 2018; 224: 240e4. 5 McLaughlin C, Squillaro AI, Oushaliman S, et al. The association between opioid use and outcomes in infants undergoing pyloromyotomy. Clin Ther 2019; 10: 1690e700. 6 Kong JY, Yeo KT, Abdel-Latif ME, et al. Outcomes of infants with abdominal wall defects over 18 years. J Pediatr Surg 2016; 51: 1644e9. 7 Alganabi M, Lee C, Bindi E, Li B, Pierro A. Recent advances in understanding necrotizing enterocolitis. F1000Res 2019; 25: 8. https://doi.org/10.12688/f1000research.17228.1. 8 Ahmad NS, Dobby N, Walker E, et al. A multicenter audit of the use of bronchoscopy during open and thoracoscopic repair of esophageal atresia with tracheoesophageal fistula. Pediatr Anesth 2019; 29: 640e7. 9 Knottenbelt G, Costi D, Stephens P, Beringer R, Davidson A. An audit of anesthetic management and complications of tracheoesophageal fistula and esophageal atresia repair. Pediatr Anesth 2012; 22: 268e74. 10 Qin J, Ren Y, Ma D. A comparative study of thoracoscopic and open surgery of congenital diaphragmatic hernia in neonates. J Cardiothorac Surg 2019; 26: 118. https://doi.org/10.1186/ s13019-019-0938-3. 11 Tsao K, Lally PA, Lally KP. Minimally invasive repair of congenital diaphragmatic hernia. J Pediatr Surg 2011; 46: 1158e64. 12 Zani A, Lamas-Pinheiro R, Paraboschi I, et al. Intraoperative acidosis and hypercapnia during thoracoscopic repair of congenital diaphragmatic hernia and esophageal atresia/tracheoesophageal fistula. Pediatr Anesth 2017; 27: 841e8. 13 Olsen M, Avery N, Khurana S, Laing R. Pneumoperitoneum for neonatal laparoscopy: how safe is it? Pediatr Anesth 2013; 23: 457e9. 14 Lawal TA, Gosemann JH, Kuebler JF, Gluer S, Ure BM. Thoracoscopy versus thoracotomy improves midterm musculoskeletal status and cosmesis in infants and children. Ann Cardiothorac Surg 2009; 87: 224e8.
Anaesthetic technique: Effective communication between the surgeon and the anaesthetist is essential. An IV or gas induction can be used followed by neuromuscular blockade and intubation. The use of intra-arterial monitoring will depend on the type of the surgery but can be helpful assessing oxygen and carbon dioxide tensions (especially as end-tidal CO2 can be unreliable) and to monitor haemoglobin, glucose and electrolyte concentrations throughout surgery. Hypotension can be managed with IV fluid, blood and vasopressors. Remifentanil infusion in combination with volatile anaesthetic is an effective technique. If hypoxia is refractory or hypercapnia becomes extreme then intermittent reinflation of the collapsed lung will be helpful. Regional analgesia in the form of paravertebral or intrapleural blocks are helpful for managing postoperative pain, although a morphine infusion is a simple and effective technique. Lung isolation in infants is best achieved by use of a bronchial blocker, which may consist of a Fogarty catheter or a Foley urinary catheter inserted alongside or through the endotracheal tube. Double lumen tubes are not available in sizes appropriate for infants. The aim is to get the blocker into the mainstem bronchus of the operative lung, and inflate a balloon to occlude ventilation of that lung. The lung may take some time to collapse as it is not possible to use suction through any of these catheters. A practical technique is to insert the blocker (usually a 3 Fr in neonates <5 kg) through the cords prior to intubation, inserting blindly to a depth of about 20 cm after which intubation is performed using a standard cuffed endotracheal tube (ETT). The tip of the catheter can be visualized by use of a fibreoptic scope passed through the ETT, and the balloon can be positioned and inflated under vision. The blocker position should always be rechecked by way of a fibreoptic scope when the patient is moved into the lateral position. A REFERENCES 1 Disma N, Withington D, McMann ME, et al. Surgical practice and outcome in 711 neonates and infants undergoing hernia repair in a large multicenter RCT: secondary results from the GAS Study. J Pediatr Surg 2018; 53: 1643e50. 2 Davidson AJ, Morton NS, Arnup SJ, et al. Apnea after awake regional and general anesthesia in infants: the general anesthesia compared to spinal anesthesia studyecomparing apnea and neurodevelopmental outcomes, a randomized controlled trial. Anesthesiology 2015; 123: 38e54.
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FURTHER READING Christensen RE, Lee AC, Gowen MS, et al. Pediatric perioperative cardiac arrest, death in the off hours: a report from wake up safe, the pediatric quality improvement initiative. Anesth Analg 2018; 127: 472e7. Habre W, Disma N, Virag K, et al. Incidence of severe critical events in paediatric anaesthesia (APRICOT): a prospective multicentre observational study in 261 hospitals in Europe. Lancet Respir Med 2017 May; 5: 412e25.
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Anaesthesia for surgery in infancy
Learning objectives After reading this article, you should be able to: C describe general surgical conditions encountered in infancy and their surgical approach C understand the anaesthetic and physiological implications of these conditions C describe anaesthetic principles and techniques of general surgical conditions in infants C understand the physiological changes and anaesthetic implications observed during minimally invasive surgery in infancy
Graham Knottenbelt Amanda Dalton
Abstract Specialist surgery in infancy provides challenges for paediatric anaesthetists. There is growing appreciation that the relatively higher rate of severe critical events in infants during the perioperative period requires appropriate competence, experience and resources for the safe conduct of anaesthesia. Both common (inguinal hernias and hypertrophic pyloric stenosis) and less common conditions (tracheo-oesophageal fistula, congenital diaphragmatic hernia, exomphalos, gastroschisis, and congenital lobar emphysema) require a sound understanding of the relevant pathology and the particular issues that may be encountered in these infants. In the last decade there has been a rise in the number of procedures in infancy being performed with a minimally invasive technique and this has a wide range of implications for anaesthesia.
approach will mandate a general anaesthetic rather than a regional technique. Anaesthetic technique The conduct of anaesthesia and choice of analgesia is patientdependent. A summary of the available options is included in Table 1. Some practitioners consider it is reasonable to use regional technique in ex-premature infants because of the lower incidence of apnoea in PACU compared with general anaesthesia. Babies with a history of extreme prematurity (<26 weeks) and those with significant comorbidities (e.g. neurological abnormalities) may benefit more from a regional technique than otherwise healthy babies.
Keywords Congenital diaphragmatic hernia; duodenal atresia; exomphalos; gastroschisis; infantile inguinal hernia; laparoscopy; necrotizing enterocolitis; pyloric stenosis; thoracoscopy; tracheooesophageal fistula
Postoperative apnoea in the neonate Neonatal apnoea is defined as a pause in breathing for more than 15 seconds, or more than 10 seconds if associated with desaturation or bradycardia. The clinical significance of brief selflimiting apnoea is unclear. Increasing prematurity is the biggest risk factor for apnoea. The risk is further compounded by anaesthesia and sedation, even in neonates without a history of apnoea (Box 1). Recent analysis of data from the GAS study, a large randomized controlled trial comparing awake regional anaesthesia with general anaesthesia in infants having inguinal hernia repair,2 reported an incidence of apnoea of 6.1% in preterm infants compared with 0.3% in term infants. Most apnoea occurred early (in the first 30e60 minutes after surgery) but they were also reported in the first 12 postoperative hours. While early apnoea was less frequent after regional anaesthesia, there was a similar incidence of late apnoea in both groups. Furthermore, there was occasional life-threatening apnoea in all babies irrespective of the method of anaesthesia. These findings reinforce the importance of postoperative apnoea monitoring in this cohort. A safe approach is to admit all ex-premature babies of less than 60 weeks postmenstrual age overnight for apnoea
Royal College of Anaesthetists CPD Matrix: 2D02, 3D00
Inguinal hernia in infancy Repair of inguinal hernia is one of the most common operations in paediatric surgery. Hernias can occur in term infants, however the incidence increases in babies of increasing prematurity. It is preferable that the surgery be performed electively, with the risk of incarceration increasing if the hernia is left untreated. Surgery The open procedure is relatively quick (approximately 30 min per side), and involves ligating a patent processus vaginalis into which herniation has occurred. The procedure can also be performed laparoscopically, even in small or premature infants or when the hernia is incarcerated.1 Unilateral hernia repair is likely to be faster when performed as an open procedure, but the main proposed benefit of a laparoscopic approach is that it allows exploration of the contralateral side, and ligation of a second patent processus vaginalis if present. This prevents later presentation with a hernia on the contralateral side. A laparoscopic
Risk factors for postoperative apnoea in the neonate C C
Graham Knottenbelt MB BCh FRCA FANZCA FHEA is a Consultant Paediatric Anaesthetist at Starship Children’s Hospital, Auckland, New Zealand. Conflicts of interest: none declared.
C C
Amanda Dalton MB ChB FANZCA MBioethics is a Consultant Paediatric Anaesthetist at Starship Children’s Hospital, Auckland, New Zealand. Conflicts of interest: none declared.
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C
Reduced age Lower gestational age at birth (incidence 7% at 34e35 weeks, 13% in those born <32 weeks’ gestation, 80% in <30 weeks) Lower weight (incidence 30% in those with birth weight <1000 g) Comorbidities (neurological, respiratory) History of apnoea
Box 1
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Anaesthesia options for inguinal hernia surgery in infancy Type of anaesthetic Doses/Techniques
Advantages
GA
Familiarity Increased risk of early apnoea (first 30 min Good surgical conditions postoperatively) (no crying/agitation from baby)
Awake spinal
Caudal
Inhalational induction with sevoflurane ETT or LMA can be used Best accompanied by caudal for analgesia which will reduce anaesthetic requirements Secure IV access prior to spinal insertion Perform awake in left lateral position with assistant Strict asepsis Use short 25 g needle, e.g. 0.1 ml/kg of 0.5% bupivacaine Oral sucrose may be useful to help settle infant Good analgesic supplement, aim to block to T10, 1 ml/kg of 0.2% ropivacaine or levo-bupivacaine Can be used as sole anaesthetic in awake patient
Disadvantages
Lower rate of early apnoea No airway manipulation Early feeding
High failure rate (20%) Potential for distressed or crying baby. Requires technical expertise Less surgical time allowable e 45 min Upper body movement may be problematic for surgeon, especially if infant >5 kg
Generally well tolerated Technically easier than spinal
Slower onset (15e20 min) Motor block less reliable than with spinal (if sole anaesthetic) Higher LA dose and risk of toxicity
GA, general anaesthetic; LA, local anaesthetic; LMA, laryngeal mask airway.
Table 1
starting fluid maintenance (10e20 ml/kg boluses of saline balanced salt solution). Depending on the initial electrolyte results, potassium may be required as well. Maintenance fluid consisting of normal saline with 5% or 10% glucose and 10 mmol/L of KCl should be commenced at a rate of 100 ml/kg per day. A solution containing chloride is required as this provides the kidney with the means to excrete bicarbonate thus correcting the alkalosis. Oral feeds should be ceased once diagnosed and a nasogastric tube inserted. Nasogastric losses should be recorded and replaced with intravenous normal saline.3 The criteria determining suitability for surgery are summarized in Box 2. It is generally recommended to aim for correction of alkalaemia due to concerns around postoperative apnoea in babies with a high bicarbonate concentration.
monitoring irrespective of the anaesthetic technique. Term infants should be admitted overnight if <44 weeks post-conception age but will otherwise be suitable for day surgery. It is good practice to observe a period of 12 hours without an apnoea prior to discharge.
Hypertrophic pyloric stenosis Pyloric stenosis occurs in 1e5:1000 live births and is characterized by thickened muscle at the level of the pylorus leading to gastric outlet obstruction. It is five times more likely in males, and usually presents at 2e8 weeks of life in otherwise healthy term infants. The baby will present with progressive non-bilious vomiting which may become projectile, and eventually leads to severe dehydration if prolonged. There may be an ‘olive’ palpated in the epigastrium and the diagnosis is usually confirmed with an ultrasound (95% sensitivity) to assess pyloric thickening. The characteristic biochemical profile is due to the loss of acidic gastric secretions and dehydration resulting in a hypochloraemic hypokalaemic metabolic alkalosis. Perioperative morbidity and mortality is now very low due to a good understanding of the pathophysiology, appropriate preoperative optimization and a refined surgical approach.
Surgery Surgical correction is brief (generally less than 30 minutes) and involves either open or laparoscopic incision of the pylorus down to the mucosa to relieve the obstruction. The open procedure,
Guidelines before pyloromyotomy C
Preoperative optimization Pyloromyotomy is never an emergency procedure and should only be performed once the baby has been fully resuscitated and electrolytes correction is underway. Babies with moderate to severe dehydration will initially need to be resuscitated before
C C
Adequate fluid resuscitation with no clinical signs of dehydration. Serum chloride >100 mmol/l Serum HCO3 <30 mmol/l Na >130 mmol/l K >3 mmol/l
Box 2
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are usually detected before birth, which facilitates management by a multidisciplinary team in a specialist centre. Gastroschisis is usually a small (2e3 cm) para-umbilical defect located to the right of the umbilicus through which the small bowel herniates. There is no sac or covering over the bowel, which is exposed to the amniotic fluid in utero and may be in inflamed, oedematous and functionally abnormal as a result. Associated anomalies are rare, except for intestinal atresia which may be seen in up to 10% of children. By contrast, exomphalos (omphalocoele) is often a larger central defect with a herniation of bowel and abdominal organs into a membranous sac originating from the umbilical cord. The defect may contain small bowel, liver, spleen, colon and occasionally gonads. This covering may rupture during delivery. There is a high rate of associated anomalies with fewer than 20% of neonates having an isolated lesion. Common associations include trisomies (13, 18, 21), and syndromes such as BeckwithWiedemann syndrome (macroglossia, visceromegaly, hypoglycaemia) and pentalogy of Cantrell. Cardiac defects are common (atrial and ventricular septal defects, tetralogy of Fallot, transposition of the great vessels) as are renal defects. All babies with exomphalos should have an echocardiogram and renal ultrasound after birth.
also known as the Ramstedt pyloromyotomy, involves a right upper quadrant transverse incision or a peri-umbilical incision. The laparoscopic procedure has been advanced in the last two decades with proponents citing reduced hospital stay and better cosmesis. Which approach is better remains controversial as there are some reports that the laparoscopic approach may have a higher rate of perforation and incomplete division of the stenosis. A meta-analysis found no significant difference in the rate of incomplete incision, mucosal perforation and reoperation between open and laparoscopic groups.4 Anaesthetic technique It is important to ensure the stomach is as empty as possible by inserting a large-bore (e.g. 14 Fr) nasogastric/orogastric catheter and suctioning out any remaining gastric contents. Traditionally, gastric contents were aspirated with the baby supine, prone and lying on each side to ensure as much volume as possible is removed. An intravenous induction with a modified rapid sequence induction (RSI) and intubation is usual, though many accept gas induction with sevoflurane. The baby should be preoxygenated wherever possible prior to induction. The nasogastric tube may need to be re-inserted after induction as the surgeon will often check the integrity of their anastomosis by asking for an injection of air into the stomach to put the repair under tension. Pyloromyotomy is not a particularly painful procedure and can comfortably be managed with paracetamol and local anaesthetic around the incision or at the port sites.5 The infant should be extubated awake and breathing monitored postoperatively as they may be slow to resume spontaneous ventilation due to the raised bicarbonate concentrations in the CSF that may be slow to return to normal.
Surgery The ultimate surgical goal for these abdominal wall defects is to reduce the evisceration and achieve abdominal closure. Survival from uncomplicated gastroschisis is around 95% if managed appropriately in a specialist paediatric centre; however, the high rate of associated comorbidities with exomphalos means survival is not as favourable. Neonates with gastroschisis have longer duration of parenteral nutrition, longer hospital stay and a higher rate of sepsis, but there is still a higher mortality in babies with exomphalos.6 Initial management of gastroschisis should include immediate protection of exposed bowel with clear plastic to reduce heat and fluid loss, and a sterile occlusive dressing in the case of exomphalos. There will need to be on-going assessment for bowel ischaemia. Some centres advocate nursing in the right lateral position to prevent vascular injury from mesenteric kinking, and it is also possible to develop a volvulus. A nasogastric tube is inserted soon after birth to decompress the bowel. More definitive bowel covering, be it primary closure or application of a silo, should occur within 8 hours, and should be expedited where there is obvious bowel ischaemia. In the case of silo application, bowel is placed in a suspended plastic tube that is gradually reduced in size so as to allow the intestines to slowly return to the abdominal cavity over 7e10 days (usually once or twice daily reductions) (Figure 1). This can be done in NICU without general anaesthesia.
Duodenal atresia Congenital duodenal atresia occurs in 1:6000 infants, presenting with bilious vomiting in the first day or two of life. Duodenal atresia is associated with multiple congenital abnormalities (up to 50e70%) including trisomy 21, cardiac anomalies and VACTERL. Diagnosis can be made antenatally or postnatally with ultrasound and X-ray may show a typical ‘double-bubble sign’. Surgery Laparotomy or laparoscopy is performed and a duodenoduodenostomy bypass anastomosis procedure done. Prognosis after successful surgical treatment of duodenal atresia is excellent with morbidity primarily related to associated abnormalities. Anaesthetic technique Priority should be given to fluid and electrolyte imbalance correction prior to anaesthesia. The neonate should be fluid resuscitated prior to surgery and nasogastric tube aspirated. An intravenous induction with a modified rapid sequence induction (RSI) and intubation is usual. Analgesia can be provided with subcostal block, epidural or morphine infusion.
Anaesthetic technique The nasogastric tube should be aspirated prior to induction. General anaesthesia with neuromuscular blockade (often modified RSI), intubation and positive pressure ventilation is usual. There is often large volume fluid losses intraoperatively and continual assessment of fluid loss is necessary. Abdominal closure can be complicated by markedly higher intra-abdominal pressure; high ventilation pressures >30 cmH2O, haemodynamic compromise (dropping MAP despite fluid boluses), oliguria,
Gastroschisis and exomphalos Exomphalos and gastroschisis are the two most common congenital abdominal wall defects, both having an incidence of 1e5:10,000 live births. With the advent of advanced antenatal scanning these defects
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Anaesthetic technique These babies are some of the sickest a paediatric anaesthetist may encounter. The neonate will require intubation, paralysis and ventilation. Haemodynamic instability is common with large volume replacement (including blood, platelet and factor transfusion) and inotropic support often required. Close attention should be given to the temperature of the baby as heat loss may be significant. Frequent blood gases should be obtained if possible, with particular attention to acid-base status, haemoglobin, coagulation, calcium and glucose.
Tracheo-oesophageal fistula and oesophageal atresia Tracheo-oesophageal fistula (TOF) is a congenital defect that occurs in 1:4000 live births. It consists of a variable combination of oesophageal atresia and an abnormal fistula between the oesophagus and the trachea. The most common variant is an oesophageal atresia with a blind upper pouch and a distal fistula connecting the trachea to the distal portion of the oesophagus (Figure 2). The diagnosis may be made antenatally, or will present soon after birth with excessive oral secretions due to saliva pooling in the blind pouch, choking episodes on feeding and an inability to pass a nasogastric tube. The nasogastric tube will characteristically appear coiled in the upper pouch on a chest Xray and air in the stomach will confirm the presence of a fistula. There is a higher rate of prematurity and at least 50% of babies with a TOF will have another anomaly including cardiac defects, VACTERL (vertebral defects, anal defects, tracheo-oesophageal, renal and limb malformations), other gastrointestinal anomalies (imperforate anus, duodenal atresia) and urogenital defects. The most common cardiac defects are ventriculoseptal defects and tetralogy of Fallot. Cardiac defects, low birth weight and prematurity are associated with higher mortality; however, survival is now greater than 90%.
Figure 1 Silo bag containing gastroschisis.
metabolic acidosis, or intra-abdominal pressures >15 mmHg are considered abnormal and will necessitate a change of surgical approach if this occurs. Postoperative neonates are usually returned to an ICU intubated with mechanical ventilation. Extubation can be considered after surgery if the defect is small, there is adequate intraoperative analgesia, no signs of raised intra-abdominal pressures, and ventilation is stable with minimal support. Central venous access is usually required within the first few days as infants are likely to require a period of parenteral nutrition. Postoperative complications include necrotizing enterocolitis, intra-abdominal sepsis and ileus.
Surgery The neonate is kept nil by mouth and a Replogle tube is inserted into the upper oesophageal pouch in order to continuously suction pooling saliva. The prone position is commonly adopted. Surgery is ideally performed within 24 hours of diagnosis to prevent soiling of the lungs by saliva or stomach acid. The procedure is usually performed via a right thoracotomy but can also be performed thoracoscopically. The first step is to identify and ligate the fistula, and then the two ends of the oesophagus are anastomosed. This may not be immediately possible if there is a long gap between the proximal and distal oesophagus in which case a gastrostomy will be required so that enteral feeding can commence. Thoracoscopic repair of TOF was first performed in 1999 and has had widespread uptake since. There is conflicting evidence as to whether hospital stay, pain scores, time to full feeds and complication rates are better with a thoracoscopic approach. The thoracoscopic approach is associated with an improved cosmetic outcome and possibly lower rates of late scoliosis.
Necrotizing enterocolitis Necrotizing enterocolitis (NEC) is a condition seen in premature neonates in whom there is inflammation, necrosis and sometimes perforation of the bowel wall. There is a wide variation in severity, from relatively mild localized disease that can be managed conservatively to severe widespread disease with shock and an associated high mortality. Presenting features include signs of sepsis, progressive abdominal distension, bilious vomiting or nasogastric aspirates, bloody stools, and a characteristic finding of intramural gas on an abdominal X-ray. Surgery Non-operative management involves ceasing enteral feeding, broad-spectrum antibiotics and general supportive measures such as inotropes and ventilator support. Operative surgery involves either peritoneal drainage or laparotomy with bowel resection and possibly stoma formation.7 Surgery is required when there is clinical deterioration despite maximal medical therapy, or when there is evidence of free air in the abdomen.
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Anaesthetic technique Table 2 summarizes problems that can occur during anaesthesia for TOF. It is generally considered safe to use an inhalational induction with oxygen and sevoflurane. This allows the infant to
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morbidity and mortality in this condition. The pulmonary arteries have thickened walls and a reduced cross-sectional area leading to increased pulmonary vascular resistance and a high risk of developing pulmonary hypertension. Survival improves where treatment is directed towards managing the pulmonary hypoplasia and the associated pulmonary hypertension. Secondary injury from aggressive mechanical ventilation is also a cause of morbidity and mortality. Approximately 50% of babies will have associated anomalies including congenital heart defects (very common), spinal abnormalities and chromosomal anomalies. Prognosis is worse with left-sided or bilateral hernias, where there are associated anomalies, where there is liver herniation and where there is an observed:expected lung head ratio (O/E LHR) of <28%. There is a high rate of chronic lung disease and gastrointestinal problems in survivors (up to 50%).
Gross classification and incidence of tracheo-oesophageal fistula
b
a
d d
c c
Preoperative management A period of stabilization prior to repair is preferable and conveys a mortality benefit. Investigation should include echocardiogram to exclude congenital heart defects and assessment of the right ventricle. Management involves early intubation, avoiding stomach or bowel in the chest being distended with gas, and ventilation with airway pressures below 25 cmH2O. Central and arterial access will facilitate fluid resuscitation, inotropes and parenteral feeding. If higher airway pressures are required, high-frequency oscillatory ventilation (HFOV) is considered with permissive hypercapnoea (PaCO2 45e55 mmHg), although support for this technique is weak. Extracorporeal membrane oxygenation (ECMO) has been used in the past to manage resistant respiratory failure and pulmonary hypertension, however a survival benefit is not proven and the use of ECMO continues to be debated. Sildenafil and inhaled nitric oxide (NO) can be useful for treating pulmonary hypertension.
e e
(a) Oesophageal atresia (OA) (Gross classification: A. Vogt classification: 1. Approximate frequency 10%). (b) Proximal tracheo-oesophageal fistula (TOF) with distal OA (Gross: B. Vogt: 3A. Approximate frequency 1%). (c) Distal TOF with proximal OA (Gross: C. Vogt: 3B. Approximate frequency 85%). (d) Proximal TOF and distal TOF (Gross: D. Vogt: 3C. Approximate frequency 1%). (e) TOF without OA or ‘H’-type TOF (Gross: E. Vogt: 2. Approximate frequency 3%)
Figure 2
continue to breathe spontaneously and if problems with positive pressure ventilation become apparent there is more control, as well as the opportunity to revert back to spontaneous ventilation. A bronchoscopy may be performed to assess the location and size of the fistula, as well as the presence of multiple fistulas (Figure 3). If the fistula is distal or particularly large then an attempt can be made to occlude the fistula by way of a balloon catheter (e.g. Fogarty); this may be done with the help of a fibreoptic scope through a laryngeal mask.8,9 Alternatively an ETT could be inserted, positioning the tip below the fistula with the aid of a fibreoptic bronchoscope, after which positive pressure ventilation can be initiated at low pressures. It is impractical to attempt to maintain spontaneous ventilation throughout the whole operation, particularly if performed thoracoscopically. The baby is routinely returned to intensive care intubated, paralyzed and ventilated, although the use of an epidural has been used to facilitate early extubation. Oesophageal strictures requiring recurrent oesophageal dilatation. Gastro-oesophageal reflux and tracheomalacia are common long-term complications.
Surgery The procedure can be performed either open or thoracoscopically.10 Open procedure involves a subcostal incision in order to return the herniated organs to the abdomen with either a primary or patch repair of the defect in the diaphragm. The recurrence rate is higher after a minimally invasive thoracoscopic approach.11 The frequently prolonged nature of the thoracoscopic procedure means that extreme hypercapnia and severe respiratory acidosis have been reported,12 worsening a pre-existing pulmonary hypertension disposition. Anaesthetic technique The most appropriate location for surgery will depend on the stability of the baby and any advanced therapies in place (e.g. ECMO and HFOV). A nasogastric tube is essential to keep the stomach and bowel deflated. An arterial line (ideally pre-ductal) and central venous line is extremely helpful. There are two main intraoperative aims: avoidance of pulmonary hypertension and reduction of barotrauma. Neuromuscular blocking drugs should be used and ventilation with airway pressures as low as possible, allowing permissive hypercapnia and increasing respiratory rate rather than increasing pressures.
Congenital diaphragmatic hernia Congenital diaphragmatic hernia (CDH) is a birth defect occurring in 1:3000 live births. It consists of a herniation of abdominal viscera into the thorax through a defect in the diaphragm, often in combination with abnormally developed lungs (Figure 4). A left-sided hernia is present in 80% of cases, but can be bilateral or right-sided. Herniated organs can include small and large bowel, stomach, liver and spleen. The mass effect in the thorax prevents normal lung development and it is the resulting pulmonary hypoplasia and abnormal vasculature that lead to
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Critical problems that can occur in anaesthesia in TOF/OA repair Issue
Implications
Management
Risk of anomalies, most importantly cardiac
May have right sided aortic arch / necessitates left thoracotomy instead of usual right sided approach May be prone to significant intraoperative instability. Cardiac problems may be compounded by acid-base changes and intraoperative fluid shifts/blood loss Gas can enter the stomach with positive pressure ventilation causing gastric distension and restriction of ventilation. Higher risk in those with poorly compliant lungs and with carinal, large or multiple fistulas Intubation of fistula and ventilation of stomach is possible
Preoperative ECHO is routine Arterial line is extremely useful and central venous access optimal if there are known cardiac issues
Inadequate pulmonary ventilation and ventilation through TOF
Intraoperative compression of trachea and great vessels
May have transient difficulties with ventilation Sudden blood pressure swings are common
Attempt can be made to maintain spontaneously ventilation until the position of the fistula is identified and ligated Ventilate with as low a pressure, accepting hypercapnoea if necessary Bronchoscopy will identify size and site of fistula. Position ETT distal to fistula if possible or occlude fistula with Fogarty catheter Can perform deliberate endobronchial intubation to bypass the fistula In extremis, the surgeon can perform a gastrostomy to decompress the stomach Close communication with the surgeon is essential Hand ventilation may be easiest at some critical stages Arterial line and central line helpful especially if inotropes are required
Table 2
The neonate commonly needs at least 24 hours of ventilation postoperatively. There will be a pneumothorax as the hypoplastic lung will only partially fill the vacated thoracic cavity and this will slowly resolve over several weeks as the lung expands and fluid fills the cavity. It is possible to have a postoperative pulmonary hypertensive crisis during which hypoxia and acidaemia can worsen ventilation considerably.
insufflation leading to an increase in intra-abdominal pressure (generally <10 mmHg). Physiological effects: Ephalad displacement of the diaphragm restricts lung excursion, leading to a reduced functional residual capacity (FRC), reduced lung compliance and increased airway resistance. Infants have a high closing capacity relative to FRC, which makes them more prone to collapse of dependent airways and atelectasis. In addition, oxygen saturations may be compromised due to impaired ventilation-perfusion matching. Hypercarbia may be pronounced in infants due to more rapid absorption of CO2 into the blood; this in turn requires a higher
Minimally invasive surgery in infancy In recent years there has been considerable growth in the number of surgical procedures in infancy being performed using laparoscopic or thoracoscopic minimally invasive techniques. Benefits may include improved cosmetic outcomes, reduced postoperative pain, reduced musculoskeletal damage and quicker recovery, but there are particular challenges for the anaesthetist and thus a good understanding of the accompanying physiology and its anaesthetic implications is important. Laparoscopy Procedures suitable for a laparoscopic approach include orchidopexy, pyloromyotomy, inguinal hernia repair, laparoscopicassisted pull-through for Hirschsprung’s disease, duodenal atresia repair/stoma formation and exploratory laparoscopy for acute abdomen. A pneumoperitoneum is achieved using CO2
Figure 3 Bronchoscopic view of TOF.
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should be notified if there are problems not improved by adjusting the ventilation. Effective neuromuscular blockade will improve ventilation and will allow lower insufflation pressures. The anaesthetist should be wary of the ETT migrating caudad due to the increased intra-abdominal pressure. Thoracoscopy Thoracic surgery in infants may be through an open thoracotomy or using video-assisted thoracoscope (VATS). In open procedures the surgeon generally retracts and collapses the lung, and no formal lung isolation is undertaken by the anaesthetist. Unlike in adults, this is possible and well-tolerated in infants due to more elastic and generally healthier lung tissue. Thoracoscopic surgery is now being used even in very small babies (Figure 5). Procedures that can be performed thoracoscopically include TOF/ oesophageal atresia repair, lung resection for congenital anomalies, congenital diaphragmatic hernia repair and ligation of patent ductus arteriosus. The proposed benefits of a thoracoscopic approach over open surgery are broadly the same as those for laparoscopic surgery and include reduced pain, better cosmesis and shorter hospital stay. There is also some evidence that there is a lower incidence of late musculoskeletal complications in thoracoscopic surgery, as demonstrated by a higher rate of chest wall deformity and late scoliosis in infants who have had open thoracotomy.14 To perform a procedure thoracoscopically, CO2 is insufflated into the pleural space to achieve good surgical access and visualization. Although this is easier when one-lung ventilation is achieved, that can be challenging in babies due to their small size and limitations on the equipment available. For this reason, lung isolation should always be attempted with the caveat that a perfect result may not always be achievable.
Figure 4 X-ray showing congenital diaphragmatic hernia. Note presence of ETT and umbilical venous and arterial lines.
minute ventilation by way of higher inflation pressures and respiratory rate using positive pressure ventilation. Cardiovascular responses are variable, but derangements are unusual with insufflation pressures less than 10 mmHg. If higher pressures are needed (>15 mmHg) and the patient is unwell or hypovolaemic, the reduced venous return from inferior vena cava compression may cause a reduction in cardiac output and hypotension. Rarely, cardiovascular collapse has been described that has been attributed to gas embolism with initiation of the pneumoperitoneum.13 Particularly small or premature babies may not be suitable for laparoscopic surgery as they may tolerate the physiological effects of a pneumoperitoneum poorly.
Physiological effects: The degree of hypercapnia and hypoxia observed in thoracoscopic surgery is likely to be greater than it is during open surgery.12 Some infants will have healthy lungs and will therefore tolerate one-lung ventilation better than adults; however, hypoxia can still be marked due to their increased oxygen consumption and hypoxic pulmonary vasoconstriction. Both of these factors magnify ventilation/perfusion mismatching and a high FiO2 will sometimes be required to overcome this. Other physiological derangements include hypercapnia, hypotension and respiratory acidosis. It is rare for thoracoscopic procedures to cause hypotension from compression of the great
Anaesthetic technique: The use of cuffed endotracheal tubes will prevent problems arising from a leak around the endotracheal tube. PEEP of 3e8 cmH2O is likely to be useful to offset any hypoxia and the occasional manual recruitment breath will help to re-expand collapsed dependent lung units and improve oxygen saturations. Release of the pneumoperitoneum will usually reverse any refractory respiratory compromise, and the surgeon
Figure 5 (a) Thoracoscopic positioning and (b) thoracoscopic ports.
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vessels or mediastinal shift in babies, mainly because low insufflation pressures (<10 mmHg) are usually adequate to provide good surgical conditions.
3 Kamata M, Cartabuke RS, Tobias JD. Perioperative care of infants with pyloric stenosis. Pediatr Anesth 2015; 25: 1193e206. 4 Costanzo CM, Vinocur C, Berman L. Postoperative outcomes of open versus laparoscopic pyloromyotomy for hypertrophic pyloric stenosis. J Surg Res 2018; 224: 240e4. 5 McLaughlin C, Squillaro AI, Oushaliman S, et al. The association between opioid use and outcomes in infants undergoing pyloromyotomy. Clin Ther 2019; 10: 1690e700. 6 Kong JY, Yeo KT, Abdel-Latif ME, et al. Outcomes of infants with abdominal wall defects over 18 years. J Pediatr Surg 2016; 51: 1644e9. 7 Alganabi M, Lee C, Bindi E, Li B, Pierro A. Recent advances in understanding necrotizing enterocolitis. F1000Res 2019; 25: 8. https://doi.org/10.12688/f1000research.17228.1. 8 Ahmad NS, Dobby N, Walker E, et al. A multicenter audit of the use of bronchoscopy during open and thoracoscopic repair of esophageal atresia with tracheoesophageal fistula. Pediatr Anesth 2019; 29: 640e7. 9 Knottenbelt G, Costi D, Stephens P, Beringer R, Davidson A. An audit of anesthetic management and complications of tracheoesophageal fistula and esophageal atresia repair. Pediatr Anesth 2012; 22: 268e74. 10 Qin J, Ren Y, Ma D. A comparative study of thoracoscopic and open surgery of congenital diaphragmatic hernia in neonates. J Cardiothorac Surg 2019; 26: 118. https://doi.org/10.1186/ s13019-019-0938-3. 11 Tsao K, Lally PA, Lally KP. Minimally invasive repair of congenital diaphragmatic hernia. J Pediatr Surg 2011; 46: 1158e64. 12 Zani A, Lamas-Pinheiro R, Paraboschi I, et al. Intraoperative acidosis and hypercapnia during thoracoscopic repair of congenital diaphragmatic hernia and esophageal atresia/tracheoesophageal fistula. Pediatr Anesth 2017; 27: 841e8. 13 Olsen M, Avery N, Khurana S, Laing R. Pneumoperitoneum for neonatal laparoscopy: how safe is it? Pediatr Anesth 2013; 23: 457e9. 14 Lawal TA, Gosemann JH, Kuebler JF, Gluer S, Ure BM. Thoracoscopy versus thoracotomy improves midterm musculoskeletal status and cosmesis in infants and children. Ann Cardiothorac Surg 2009; 87: 224e8.
Anaesthetic technique: Effective communication between the surgeon and the anaesthetist is essential. An IV or gas induction can be used followed by neuromuscular blockade and intubation. The use of intra-arterial monitoring will depend on the type of the surgery but can be helpful assessing oxygen and carbon dioxide tensions (especially as end-tidal CO2 can be unreliable) and to monitor haemoglobin, glucose and electrolyte concentrations throughout surgery. Hypotension can be managed with IV fluid, blood and vasopressors. Remifentanil infusion in combination with volatile anaesthetic is an effective technique. If hypoxia is refractory or hypercapnia becomes extreme then intermittent reinflation of the collapsed lung will be helpful. Regional analgesia in the form of paravertebral or intrapleural blocks are helpful for managing postoperative pain, although a morphine infusion is a simple and effective technique. Lung isolation in infants is best achieved by use of a bronchial blocker, which may consist of a Fogarty catheter or a Foley urinary catheter inserted alongside or through the endotracheal tube. Double lumen tubes are not available in sizes appropriate for infants. The aim is to get the blocker into the mainstem bronchus of the operative lung, and inflate a balloon to occlude ventilation of that lung. The lung may take some time to collapse as it is not possible to use suction through any of these catheters. A practical technique is to insert the blocker (usually a 3 Fr in neonates <5 kg) through the cords prior to intubation, inserting blindly to a depth of about 20 cm after which intubation is performed using a standard cuffed endotracheal tube (ETT). The tip of the catheter can be visualized by use of a fibreoptic scope passed through the ETT, and the balloon can be positioned and inflated under vision. The blocker position should always be rechecked by way of a fibreoptic scope when the patient is moved into the lateral position. A REFERENCES 1 Disma N, Withington D, McMann ME, et al. Surgical practice and outcome in 711 neonates and infants undergoing hernia repair in a large multicenter RCT: secondary results from the GAS Study. J Pediatr Surg 2018; 53: 1643e50. 2 Davidson AJ, Morton NS, Arnup SJ, et al. Apnea after awake regional and general anesthesia in infants: the general anesthesia compared to spinal anesthesia studyecomparing apnea and neurodevelopmental outcomes, a randomized controlled trial. Anesthesiology 2015; 123: 38e54.
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FURTHER READING Christensen RE, Lee AC, Gowen MS, et al. Pediatric perioperative cardiac arrest, death in the off hours: a report from wake up safe, the pediatric quality improvement initiative. Anesth Analg 2018; 127: 472e7. Habre W, Disma N, Virag K, et al. Incidence of severe critical events in paediatric anaesthesia (APRICOT): a prospective multicentre observational study in 261 hospitals in Europe. Lancet Respir Med 2017 May; 5: 412e25.
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