Neonatal Anaesthesia
Content
Anaesthesia for common conditions in infancy
Kathleen Ann Wilkinson FRCA MRCP John Gibson MA FRCA FRCS
Anaesthesia for infants involves challenges which are different from anaesthesia in older subjects. Overall mortality in the post-neonatal age group (1–12 months) is increased compared with the preschool child. The most common cause of death is congenital abnormality, followed by sudden infant death syndrome (the rate of which is decreasing in the UK in relation to change in sleeping position) and infection. There is also evidence that perioperative morbidity and mortality is greater in the infant compared with the older child. The causes for this are multiple and include the severity of any congenital abnormality together with anatomical, physiological and pathophysiological differences (the latter including the effects of prematurity). An understanding of these differences coupled with a knowledge of altered drug handling may reduce avoidable factors.
General considerations
Infants should be anaesthetised by adequately trained and experienced staff working in a dedicated theatre environment. Occasional practice is inadvisable and there is evidence that the number of UK anaesthetists caring for infants < 6 months has reduced over the last 10 years. A full range of paediatric anaesthesia equipment should be available, including breathing systems, laryngoscopes, tracheal tubes, warming devices and monitoring equipment.
Pre-operative assessment and preparation
Although pre-operative assessment may be performed in the well infant on the day of surgery, adequate time should be allowed to elicit details of the birth and neonatal history and explain the procedures to the parents. Parental anxiety is often high and the possibility of a hitherto undetected congenital abnormality should be
DOI 10.1093/bjacepd/mkg079
born in mind. A history of prematurity is particularly significant. Apnoea (usually defined as cessation of breathing for > 15 sec) and bradycardia are well-recognised consequences of general anaesthesia in ex-preterm infants. Apnoea may be central, obstructive or a combination of both. It has been postulated that postoperative apnoea may be aggravated in part by the reduction in upper airway tone which occurs at even very low MAC concentrations of volatile agents, plus or minus the effects of high circulating levels of endorphins. Important predictors are low gestational and post-conceptional age (PCA) and significant co-morbidity, in particular anaemia. In infants born at 32 weeks’ gestational age who undergo surgery and anaesthesia at 56 weeks’ PCA and do not experience apnoea in the recovery room, it has been calculated that the incidence of apnoea is not < 1% with 95% confidence. In practice, apnoea is very unusual in fit preterm babies > 2 h after surgery but many units stand by a general recommendation that ex-premature infants should not be treated as day cases until they reach 60 weeks’ PCA. Physical examination should focus on the respiratory and cardiovascular systems. If there are symptoms and signs of a respiratory tract infection, elective surgery should generally be rescheduled. Bronchiolitis is a viral lower respiratory infection, particularly important in infants under 6 months, which produces increased airway oedema, secretions and reactivity. Elective surgery should be avoided for a minimum of 6 weeks after the initial infection if at all possible. Congenital cardiac disease affects 0.8% of live births and, of these, approximately 15% have additional abnormalities. Thus, congenital heart disease frequently forms part of a syndrome or association. Whilst heart disease is usually
Key points Anaesthesia for infants has specific requirements given the changes in physiology and ability to handle drugs which occur in the first year of life. Peri-operative morbidity and mortality is increased in infants, the highest risk of problems being in the first 6 months of life. Infants should be anaesthetised by adequately trained and experienced staff. A significant number of infants have congenital abnormalities which should be identified preoperatively. Peri-operative apnoea remains a significant challenge when anaesthetising the preterm and expreterm baby. Clear precipitating causes have been identified.
Kathleen Ann Wilkinson FRCA MRCP Consultant Anaesthetist, Anaesthetic Department, Norfolk and Norwich University NHS Trust, Colney Lane, Norwich NR4 7UZ Tel: 01603 287086 Fax: 01603 287886 E-mail: [email protected] (for correspondence) John Gibson MA FRCA FRCS SpR Anaesthetics, Norfolk and Norwich University Hospital NHS Trust, Colney Lane, Norwich NR4 7UZ
British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003 © The Board of Management and Trustees of the British Journal of Anaesthesia 2003
79
Anaesthesia for common conditions in infancy
identified by 3 months of age, all infants with a heart murmur or unexplained cyanosis need to be investigated by a cardiologist prior to surgery. In the past, it was common for all children undergoing surgery to have a pre-operative haemoglobin determination. Nowadays, it is more usual to withhold this test unless there is a specific indication (e.g. in the ex-premature infant) or when significant blood loss is anticipated. As with fit adults, a haemoglobin concentration > 7.5–8 g dl–1 is adequate and, at approximately 5 months of age, is a normal physiological finding. Premedication is rarely indicated in infants. Those aged <~8 months of age do not experience separation anxiety and many in any case will be accompanied by a parent. Therefore, the use of sedative premedication is generally unnecessary and may delay recovery. Anticholinergics are no longer routinely prescribed for their drying actions or vagolytic effects, as these are less important with modern anaesthetic agents. The use of topical local analgesics prior to venepuncture appears to be effective and generally safe in infants. Pre-operative fasting should be 6 h for formula feeds or cows’ milk, 4 h for breast milk and 2 h for clear fluids.
Induction, airway management and maintenance
Both intravenous (IV) and inhalational induction are appropriate in infants, although success in achieving IV induction may be less certain due to difficulties with cannulation (Table 1). However, IV induction is preferred in the emergency situation where a full stomach may be anticipated and where a cannula should already be in place. Thiopental or propofol may be used, although there is limited data on the latter specific to infants. Thiopental is easier to inject through small cannulae. Neonates require a relatively small dose of thiopental (3–4 mg kg–1) whereas unpremedicated infants require larger doses (up to 6 mg kg–1 in the first 6 months, falling to 5.5 mg kg–1 between 6 months and 1 year). Delayed emergence should not be problem in infants when thiopental is given in appropriate doses. Inhalational induction using sevoflurane is well tolerated and is indicated particularly when venous access is difficult and/or there is a suspected airway problem.
Table 1 Aetiology of difficult venous access in infants • Fat pads on dorsum of hands and feet make veins less visible • Veins are relatively short • Co-morbidity, e.g. prematurity may result in multiple cannulations • Previous venous disruption due to peripheral parenteral nutrition, etc. • Reduced efficacy of topical local anaesthetic (veins may be deep) • Attempts to apply and keep a topical local anaesthetic in place may be difficult (rapid onset agents such as amethocaine gel may be beneficial)
Anaesthesia causes a reduction in tidal volume and functional residual capacity which, in an infant, already falls below closing volume. An anaesthetic technique which relies on prolonged spontaneous breathing in infancy may therefore be associated with an increase in airway closure and atelectasis. Accordingly, tracheal intubation and ventilation with a small amount of positive end-expiratory pressure (PEEP) is the preferred method for most procedures. When intubating infants, a straight bladed laryngoscope is preferred. This is helpful when approaching the slightly higher anterior larynx and for picking up a large floppy epiglottis. Most anaesthetists select a tube which passes easily through the cords but does not provide an excessive leak. This facilitates the use of modern low-flow anaesthetic machines which are economical in the use of anaesthetic gases, reduce heat and moisture loss from the respiratory tract and minimise atmospheric pollution. Secure fixation of the tube at an appropriate length is particularly important, as the trachea is short (~5 cm in a 6-month-old). An appropriately-sized laryngeal mask airway (LMA) with spontaneous ventilation is occasionally appropriate in older infants undergoing elective surgery of short duration. Maintenance of anaesthesia is usually with an inhalational agent with nitrous oxide or air and oxygen. Volatile anaesthetics have a higher MAC value in infants than older children (sevoflurane MAC 3.2%, isoflurane MAC 1.9% and desflurane MAC 9.4% in infants of 1–6 months). Unlike other agents, the MAC of sevoflurane does not appear to rise in the first few months of life. Desflurane has been shown to be a particularly useful agent for maintenance of anaesthesia, especially in ex-premature infants, due to its rapid emergence characteristics.
Anaesthesia for specific conditions
Infant hernia
Hernia repair is the most common surgical procedure in infants. In term babies, the incidence is about 5%; in preterm babies (birth weights < 1 kg), it can be as high as 30%. In both groups, male infants are roughly 6 times more likely to be affected than females. Most surgery is performed electively. However, the risk of incarceration is high when the infant presents with an obstructed hernia (reported as 30% if left untreated). Therefore, if an infant presents with obstruction (which responds to conservative therapy) or a recent history suggestive of it, surgery is relatively urgent and the baby should be scheduled on the next available operating list. If an obstructed hernia fails to respond to sedation/analgesia and traction, urgent surgery is indicated.
80
British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003
Anaesthesia for common conditions in infancy
This may prove to be challenging, even for the most experienced surgeon and team. In preterm babies, the policy in many units is to perform planned herniotomy before the baby leaves hospital. In all age groups, surgery is more commonly required for right-sided hernias and approximately 10% are bilateral. Because of the high incidence of contralateral patent processus, some surgeons routinely explore both groins or first perform hernioscopy via the ipsilateral inguinal canal. Anaesthesia may be general, regional or a combination of both. In children receiving general anaesthesia, the frequency of postoperative apnoea is markedly increased. This appears to be the case even when a modern volatile anaesthetic agent is employed with no additional sedatives or opioids. Despite the higher incidence of apnoea noted after general anaesthesia, at least one author using sevoflurane with caudal analgesia has commented that the events appeared to be of minimal clinical significance. Early studies of spinal anaesthesia in preterm infants appeared to demonstrate a high incidence of peri-operative apnoea and bradycardia. However, many infants in these studies received additional sedation. More recent work on unsupplemented spinal anaesthesia has shown no increase in the incidence of apnoea between the pre- and postoperative periods However, there have been isolated case reports of significant apnoea after spinal anaesthesia which occurred on occasion intra-operatively, despite avoiding additional sedation. Consequently, infants receiving spinal anaesthesia should be monitored closely and remain so for a minimum of 12 h postoperatively. A comparison of the advantages and disadvantages of spinal anaesthesia for infant hernia repair is listed in Table 2. As long-acting spinal anaesthetics are generally unavailable in the UK, many continue to administer general anaesthesia to small infants undergoing herniotomy, employing tracheal intubation and ventilation with a short-acting muscle relaxant.
Table 2 Relative merits of spinal anaesthesia in infants Advantages of spinal anaesthesia • Reduced incidence of postoperative apnoea and bradycardia • May result in reduced need for postoperative ventilation • Less disruption to feeding regimen Disadvantages of spinal anaesthesia • Risk of apnoea and bradycardia not eliminated • Failure rate • Time taken to establish block • Limited duration of block with available agents (~45 min) – may be particularly significant in bilateral repair • May be unsuitable if laparoscopy is performed • Surgeon needs to be gentle!
Analgesia is commonly provided with a caudal epidural block and the addition of rectal paracetamol (60 mg kg–1 day–1 in neonates, 80–90 mg kg–1 day–1 thereafter). Non-steroidal antiinflammatory drugs should generally be avoided in infants under 6 months of age and weighing less than 6 kg. Caffeine 10 mg kg–1 may be used to reduce the incidence of apnoea after general anaesthesia. It should be considered in infants in high risk groups, e.g. when there is a history of apnoea, oxygen dependency and/or the gestational age is < 34 weeks, especially if the infant is still at a low PCA.
Pyloric stenosis
Pyloric stenosis is a common condition requiring surgery in early infancy. Morbidity in most industrialised countries is very low and relates almost entirely to surgical complications (wound dehiscence, duodenal perforation and inadequate pyloromyotomy) all of which should be uncommon (< 1%). A recent article in this journal covers the anaesthetic management (see references).
Talipes, congenital dysplasia of the hip
Talipes (1 in 1000 births) and congenital dysplasia hip (10 in 1000 births) occur sufficiently frequently to provide a relatively constant throughput of orthopaedic surgery in infancy in many centres. In both conditions, the orthopaedic defect is generally isolated, though it can be bilateral and may, on occasion, be associated with other conditions (e.g. congenital myopathy, cerebral palsy, arthrogryposis). These additional problems need to be considered and checked at the pre-operative visit as they will alter markedly the conduct of anaesthesia and may necessitate referral to a specialist centre. Other significant considerations include moderate blood loss and the requirement for more complex analgesic techniques such as epidural or morphine infusions in the postoperative period.
Cleft lip and palate
Many of these infants have no associated problems but all must be rigorously screened for co-morbidity. Anomalies are more common in babies with isolated cleft palate. All may require several trips to theatres in the first year of life, particularly if both lip and palate are affected. A degree of associated micrognathia (e.g. Pierre Robin syndrome) may lead to problems with intubation. Significant blood loss is occasionally seen in surgery involving the hard palate and pre-operative blood grouping is essential. Anaesthesia will include small and judicious amounts of opioids and simple analgesics including non-steroidal antiinflammatory drugs if over 6 months of age. These infants
British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003
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Anaesthesia for common conditions in infancy
may develop partial nasal obstruction in the postoperative period from a combination of blood in the airway and tissue oedema. Accordingly, they should be nursed in a high observation area for a minimum of the first 24 h postoperatively.
Intussusception
Intussusception is the most common cause of intestinal obstruction in infants outside the neonatal period with the largest group of cases presenting under 6 months of age. Most cases in the infant age group are idiopathic. Diagnosis may be difficult even in experienced hands as the classic triad of symptoms (pain, mass and bloody stool) are infrequently present simultaneously. Deaths still occur and seem to be largely as a result of late diagnosis and inadequate resuscitation. Despite its high incidence, intussusception requires operative management relatively infrequently as the vast majority are successfully reduced radiologically (up to 70–80% using air reduction). Those infants who require surgery are often in a state of shock (albeit compensated) and may be cold, perhaps when diagnosis has been delayed and/or after undergoing failed radiological reduction. Venous access is occasionally a problem at presentation when poor perfusion is superimposed upon existing difficulties. Rapid intra-osseous infusion
(e.g. 20–40 ml kg–1 of warm isotonic fluid) and oxygen therapy may be life saving. Urgent laparotomy is required following adequate fluid resuscitation. Some patients will require bowel resection, particularly if a pathological cause (e.g. Meckel’s diverticulum) or irreversibly compromised bowel is discovered. Few will require postoperative intensive care but all require a period of frequent observation of vital signs including urine output. Analgesia is provided by low dose morphine infusion (in combination with simple analgesics) or epidural blockade.
Key references
Cote CJ et al. Postoperative apnoea in former preterm infants after inguinal herniorrhaphy. Anesthesiology 1995; 82: 809–22 Fell D, Chelliah S. Infantile pyloric stenosis. BJA CEPD Rev 2001; 1: 85–8 Guidance on Provision of Paediatric Services, July 2002, <www.rcoa.org> Holzman RS. Morbidity and mortality in pediatric anesthesia, Pediatr Clin North Am 1994; 41: 239–56 Tobias JD. Spinal anaesthesia in infants and children. Paediatr Anaesth 2000; 10: 5–16 Webber SJ, Barker I. Paediatric anaesthetic pharmacology. BJA CEPD Rev 2003; 3: 50–3
See multiple choice questions 56–60.
82
British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003
Kathleen Ann Wilkinson FRCA MRCP John Gibson MA FRCA FRCS
Anaesthesia for infants involves challenges which are different from anaesthesia in older subjects. Overall mortality in the post-neonatal age group (1–12 months) is increased compared with the preschool child. The most common cause of death is congenital abnormality, followed by sudden infant death syndrome (the rate of which is decreasing in the UK in relation to change in sleeping position) and infection. There is also evidence that perioperative morbidity and mortality is greater in the infant compared with the older child. The causes for this are multiple and include the severity of any congenital abnormality together with anatomical, physiological and pathophysiological differences (the latter including the effects of prematurity). An understanding of these differences coupled with a knowledge of altered drug handling may reduce avoidable factors.
General considerations
Infants should be anaesthetised by adequately trained and experienced staff working in a dedicated theatre environment. Occasional practice is inadvisable and there is evidence that the number of UK anaesthetists caring for infants < 6 months has reduced over the last 10 years. A full range of paediatric anaesthesia equipment should be available, including breathing systems, laryngoscopes, tracheal tubes, warming devices and monitoring equipment.
Pre-operative assessment and preparation
Although pre-operative assessment may be performed in the well infant on the day of surgery, adequate time should be allowed to elicit details of the birth and neonatal history and explain the procedures to the parents. Parental anxiety is often high and the possibility of a hitherto undetected congenital abnormality should be
DOI 10.1093/bjacepd/mkg079
born in mind. A history of prematurity is particularly significant. Apnoea (usually defined as cessation of breathing for > 15 sec) and bradycardia are well-recognised consequences of general anaesthesia in ex-preterm infants. Apnoea may be central, obstructive or a combination of both. It has been postulated that postoperative apnoea may be aggravated in part by the reduction in upper airway tone which occurs at even very low MAC concentrations of volatile agents, plus or minus the effects of high circulating levels of endorphins. Important predictors are low gestational and post-conceptional age (PCA) and significant co-morbidity, in particular anaemia. In infants born at 32 weeks’ gestational age who undergo surgery and anaesthesia at 56 weeks’ PCA and do not experience apnoea in the recovery room, it has been calculated that the incidence of apnoea is not < 1% with 95% confidence. In practice, apnoea is very unusual in fit preterm babies > 2 h after surgery but many units stand by a general recommendation that ex-premature infants should not be treated as day cases until they reach 60 weeks’ PCA. Physical examination should focus on the respiratory and cardiovascular systems. If there are symptoms and signs of a respiratory tract infection, elective surgery should generally be rescheduled. Bronchiolitis is a viral lower respiratory infection, particularly important in infants under 6 months, which produces increased airway oedema, secretions and reactivity. Elective surgery should be avoided for a minimum of 6 weeks after the initial infection if at all possible. Congenital cardiac disease affects 0.8% of live births and, of these, approximately 15% have additional abnormalities. Thus, congenital heart disease frequently forms part of a syndrome or association. Whilst heart disease is usually
Key points Anaesthesia for infants has specific requirements given the changes in physiology and ability to handle drugs which occur in the first year of life. Peri-operative morbidity and mortality is increased in infants, the highest risk of problems being in the first 6 months of life. Infants should be anaesthetised by adequately trained and experienced staff. A significant number of infants have congenital abnormalities which should be identified preoperatively. Peri-operative apnoea remains a significant challenge when anaesthetising the preterm and expreterm baby. Clear precipitating causes have been identified.
Kathleen Ann Wilkinson FRCA MRCP Consultant Anaesthetist, Anaesthetic Department, Norfolk and Norwich University NHS Trust, Colney Lane, Norwich NR4 7UZ Tel: 01603 287086 Fax: 01603 287886 E-mail: [email protected] (for correspondence) John Gibson MA FRCA FRCS SpR Anaesthetics, Norfolk and Norwich University Hospital NHS Trust, Colney Lane, Norwich NR4 7UZ
British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003 © The Board of Management and Trustees of the British Journal of Anaesthesia 2003
79
Anaesthesia for common conditions in infancy
identified by 3 months of age, all infants with a heart murmur or unexplained cyanosis need to be investigated by a cardiologist prior to surgery. In the past, it was common for all children undergoing surgery to have a pre-operative haemoglobin determination. Nowadays, it is more usual to withhold this test unless there is a specific indication (e.g. in the ex-premature infant) or when significant blood loss is anticipated. As with fit adults, a haemoglobin concentration > 7.5–8 g dl–1 is adequate and, at approximately 5 months of age, is a normal physiological finding. Premedication is rarely indicated in infants. Those aged <~8 months of age do not experience separation anxiety and many in any case will be accompanied by a parent. Therefore, the use of sedative premedication is generally unnecessary and may delay recovery. Anticholinergics are no longer routinely prescribed for their drying actions or vagolytic effects, as these are less important with modern anaesthetic agents. The use of topical local analgesics prior to venepuncture appears to be effective and generally safe in infants. Pre-operative fasting should be 6 h for formula feeds or cows’ milk, 4 h for breast milk and 2 h for clear fluids.
Induction, airway management and maintenance
Both intravenous (IV) and inhalational induction are appropriate in infants, although success in achieving IV induction may be less certain due to difficulties with cannulation (Table 1). However, IV induction is preferred in the emergency situation where a full stomach may be anticipated and where a cannula should already be in place. Thiopental or propofol may be used, although there is limited data on the latter specific to infants. Thiopental is easier to inject through small cannulae. Neonates require a relatively small dose of thiopental (3–4 mg kg–1) whereas unpremedicated infants require larger doses (up to 6 mg kg–1 in the first 6 months, falling to 5.5 mg kg–1 between 6 months and 1 year). Delayed emergence should not be problem in infants when thiopental is given in appropriate doses. Inhalational induction using sevoflurane is well tolerated and is indicated particularly when venous access is difficult and/or there is a suspected airway problem.
Table 1 Aetiology of difficult venous access in infants • Fat pads on dorsum of hands and feet make veins less visible • Veins are relatively short • Co-morbidity, e.g. prematurity may result in multiple cannulations • Previous venous disruption due to peripheral parenteral nutrition, etc. • Reduced efficacy of topical local anaesthetic (veins may be deep) • Attempts to apply and keep a topical local anaesthetic in place may be difficult (rapid onset agents such as amethocaine gel may be beneficial)
Anaesthesia causes a reduction in tidal volume and functional residual capacity which, in an infant, already falls below closing volume. An anaesthetic technique which relies on prolonged spontaneous breathing in infancy may therefore be associated with an increase in airway closure and atelectasis. Accordingly, tracheal intubation and ventilation with a small amount of positive end-expiratory pressure (PEEP) is the preferred method for most procedures. When intubating infants, a straight bladed laryngoscope is preferred. This is helpful when approaching the slightly higher anterior larynx and for picking up a large floppy epiglottis. Most anaesthetists select a tube which passes easily through the cords but does not provide an excessive leak. This facilitates the use of modern low-flow anaesthetic machines which are economical in the use of anaesthetic gases, reduce heat and moisture loss from the respiratory tract and minimise atmospheric pollution. Secure fixation of the tube at an appropriate length is particularly important, as the trachea is short (~5 cm in a 6-month-old). An appropriately-sized laryngeal mask airway (LMA) with spontaneous ventilation is occasionally appropriate in older infants undergoing elective surgery of short duration. Maintenance of anaesthesia is usually with an inhalational agent with nitrous oxide or air and oxygen. Volatile anaesthetics have a higher MAC value in infants than older children (sevoflurane MAC 3.2%, isoflurane MAC 1.9% and desflurane MAC 9.4% in infants of 1–6 months). Unlike other agents, the MAC of sevoflurane does not appear to rise in the first few months of life. Desflurane has been shown to be a particularly useful agent for maintenance of anaesthesia, especially in ex-premature infants, due to its rapid emergence characteristics.
Anaesthesia for specific conditions
Infant hernia
Hernia repair is the most common surgical procedure in infants. In term babies, the incidence is about 5%; in preterm babies (birth weights < 1 kg), it can be as high as 30%. In both groups, male infants are roughly 6 times more likely to be affected than females. Most surgery is performed electively. However, the risk of incarceration is high when the infant presents with an obstructed hernia (reported as 30% if left untreated). Therefore, if an infant presents with obstruction (which responds to conservative therapy) or a recent history suggestive of it, surgery is relatively urgent and the baby should be scheduled on the next available operating list. If an obstructed hernia fails to respond to sedation/analgesia and traction, urgent surgery is indicated.
80
British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003
Anaesthesia for common conditions in infancy
This may prove to be challenging, even for the most experienced surgeon and team. In preterm babies, the policy in many units is to perform planned herniotomy before the baby leaves hospital. In all age groups, surgery is more commonly required for right-sided hernias and approximately 10% are bilateral. Because of the high incidence of contralateral patent processus, some surgeons routinely explore both groins or first perform hernioscopy via the ipsilateral inguinal canal. Anaesthesia may be general, regional or a combination of both. In children receiving general anaesthesia, the frequency of postoperative apnoea is markedly increased. This appears to be the case even when a modern volatile anaesthetic agent is employed with no additional sedatives or opioids. Despite the higher incidence of apnoea noted after general anaesthesia, at least one author using sevoflurane with caudal analgesia has commented that the events appeared to be of minimal clinical significance. Early studies of spinal anaesthesia in preterm infants appeared to demonstrate a high incidence of peri-operative apnoea and bradycardia. However, many infants in these studies received additional sedation. More recent work on unsupplemented spinal anaesthesia has shown no increase in the incidence of apnoea between the pre- and postoperative periods However, there have been isolated case reports of significant apnoea after spinal anaesthesia which occurred on occasion intra-operatively, despite avoiding additional sedation. Consequently, infants receiving spinal anaesthesia should be monitored closely and remain so for a minimum of 12 h postoperatively. A comparison of the advantages and disadvantages of spinal anaesthesia for infant hernia repair is listed in Table 2. As long-acting spinal anaesthetics are generally unavailable in the UK, many continue to administer general anaesthesia to small infants undergoing herniotomy, employing tracheal intubation and ventilation with a short-acting muscle relaxant.
Table 2 Relative merits of spinal anaesthesia in infants Advantages of spinal anaesthesia • Reduced incidence of postoperative apnoea and bradycardia • May result in reduced need for postoperative ventilation • Less disruption to feeding regimen Disadvantages of spinal anaesthesia • Risk of apnoea and bradycardia not eliminated • Failure rate • Time taken to establish block • Limited duration of block with available agents (~45 min) – may be particularly significant in bilateral repair • May be unsuitable if laparoscopy is performed • Surgeon needs to be gentle!
Analgesia is commonly provided with a caudal epidural block and the addition of rectal paracetamol (60 mg kg–1 day–1 in neonates, 80–90 mg kg–1 day–1 thereafter). Non-steroidal antiinflammatory drugs should generally be avoided in infants under 6 months of age and weighing less than 6 kg. Caffeine 10 mg kg–1 may be used to reduce the incidence of apnoea after general anaesthesia. It should be considered in infants in high risk groups, e.g. when there is a history of apnoea, oxygen dependency and/or the gestational age is < 34 weeks, especially if the infant is still at a low PCA.
Pyloric stenosis
Pyloric stenosis is a common condition requiring surgery in early infancy. Morbidity in most industrialised countries is very low and relates almost entirely to surgical complications (wound dehiscence, duodenal perforation and inadequate pyloromyotomy) all of which should be uncommon (< 1%). A recent article in this journal covers the anaesthetic management (see references).
Talipes, congenital dysplasia of the hip
Talipes (1 in 1000 births) and congenital dysplasia hip (10 in 1000 births) occur sufficiently frequently to provide a relatively constant throughput of orthopaedic surgery in infancy in many centres. In both conditions, the orthopaedic defect is generally isolated, though it can be bilateral and may, on occasion, be associated with other conditions (e.g. congenital myopathy, cerebral palsy, arthrogryposis). These additional problems need to be considered and checked at the pre-operative visit as they will alter markedly the conduct of anaesthesia and may necessitate referral to a specialist centre. Other significant considerations include moderate blood loss and the requirement for more complex analgesic techniques such as epidural or morphine infusions in the postoperative period.
Cleft lip and palate
Many of these infants have no associated problems but all must be rigorously screened for co-morbidity. Anomalies are more common in babies with isolated cleft palate. All may require several trips to theatres in the first year of life, particularly if both lip and palate are affected. A degree of associated micrognathia (e.g. Pierre Robin syndrome) may lead to problems with intubation. Significant blood loss is occasionally seen in surgery involving the hard palate and pre-operative blood grouping is essential. Anaesthesia will include small and judicious amounts of opioids and simple analgesics including non-steroidal antiinflammatory drugs if over 6 months of age. These infants
British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003
81
Anaesthesia for common conditions in infancy
may develop partial nasal obstruction in the postoperative period from a combination of blood in the airway and tissue oedema. Accordingly, they should be nursed in a high observation area for a minimum of the first 24 h postoperatively.
Intussusception
Intussusception is the most common cause of intestinal obstruction in infants outside the neonatal period with the largest group of cases presenting under 6 months of age. Most cases in the infant age group are idiopathic. Diagnosis may be difficult even in experienced hands as the classic triad of symptoms (pain, mass and bloody stool) are infrequently present simultaneously. Deaths still occur and seem to be largely as a result of late diagnosis and inadequate resuscitation. Despite its high incidence, intussusception requires operative management relatively infrequently as the vast majority are successfully reduced radiologically (up to 70–80% using air reduction). Those infants who require surgery are often in a state of shock (albeit compensated) and may be cold, perhaps when diagnosis has been delayed and/or after undergoing failed radiological reduction. Venous access is occasionally a problem at presentation when poor perfusion is superimposed upon existing difficulties. Rapid intra-osseous infusion
(e.g. 20–40 ml kg–1 of warm isotonic fluid) and oxygen therapy may be life saving. Urgent laparotomy is required following adequate fluid resuscitation. Some patients will require bowel resection, particularly if a pathological cause (e.g. Meckel’s diverticulum) or irreversibly compromised bowel is discovered. Few will require postoperative intensive care but all require a period of frequent observation of vital signs including urine output. Analgesia is provided by low dose morphine infusion (in combination with simple analgesics) or epidural blockade.
Key references
Cote CJ et al. Postoperative apnoea in former preterm infants after inguinal herniorrhaphy. Anesthesiology 1995; 82: 809–22 Fell D, Chelliah S. Infantile pyloric stenosis. BJA CEPD Rev 2001; 1: 85–8 Guidance on Provision of Paediatric Services, July 2002, <www.rcoa.org> Holzman RS. Morbidity and mortality in pediatric anesthesia, Pediatr Clin North Am 1994; 41: 239–56 Tobias JD. Spinal anaesthesia in infants and children. Paediatr Anaesth 2000; 10: 5–16 Webber SJ, Barker I. Paediatric anaesthetic pharmacology. BJA CEPD Rev 2003; 3: 50–3
See multiple choice questions 56–60.
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British Journal of Anaesthesia | CEPD Reviews | Volume 3 Number 3 2003
