Pediatrics anaesthesia

• Paediatric patients are not small adults
• Safe paediatric anaesthesia requires

  • Recognising peculiarities of age group
  • Adequate preparation
  • Appropriate technique and equipment
  • Full intra-operative monitoring
• Paediatric age group


  • Newborn to adolescent
  • Neonates - first 28 days of life
  • Infants - 1 month to 1 year
  • Preschool - 1-5 yrs
  • Schoolage - 5-12 yrs
  • Adolescent - 13-16 yrs
• Neonates further classified as

  • Full term
  • Pre-term < 37 wks
  • Extreme preterm < 28 wks
  • Post-term > 41 wks
  • Low Birth Weight < 2500g
  • Extremely Low Birth Weight < 1000g
• How children differ from adults

  • Anatomical
  • Physiological
  • Psychological
  • Pharmacological
• Airway and respiratory system

  • Large head, short neck and prominent occiput
  • Tongue is relatively large
  • Larynx is high and anterior, at the level of C3 - C4
  • Epiglottis is long, stiff and U-shaped, flops posteriorly
  • Narrow nasal passages easily blocked by secretions, may be damaged by nasogastric tube or nasally placed endotracheal tube
  • Airway is funnel shaped and narrowest at the level of the cricoid cartilage
• Airway and respiratory system

  • Limited respiratory reserve in neonate and infant
  • Horizontal ribs prevent 'bucket handle' action, limit increase in tidal volume
  • Ventilation is primarily diaphragmatic
  • Functional residual capacity (FRC) is relatively low
  • Minute ventilation is rate dependant, little means to increase tidal volume
  • Closing volume is larger than the FRC until 6-8 years, increased tendency for airway closure at end expiration
  • Muscles of ventilation easily subject to fatigue due to low percentage of Type I muscle fibres in the diaphragm
  • Alveoli are thick walled at birth, only 10% of total number in adults, develop over first 8 years
  • Apnoea is common post operatively in premature infants
  • Spontaneous ventilation TV = 6-8 ml/kg; IPPV TV = 7-10ml/kg
  • Physiological dead space = 30% and is increased by anaesthetic equipment
• Cardiovascular system


  • Myocardium is less contractile, ventricles less compliant and less able to generate tension, cardiac output is rate dependent
  • Vagal parasympathetic tone is most dominant, prone to bradycardias
  • Sinus arrhythmia is common, other irregular rhythms are abnormal
  • Patent ductus contracts in first few days, closes in 2-4 weeks
  • Closure of foramen ovale is pressure dependent, may reopen within 5 years
  • Neonatal pulmonary vasculature reacts to changes at birth, may revert to transitional circulation in first few weeks
• Renal system


  • Renal blood flow and glomerular filtration are low in first 2 years, high renal vascular resistance
  • Tubular function is immature until 8 months, unable to excrete large sodium load
  • Dehydration is poorly tolerated, increased insensible losses in premature infants
  • Larger proportion of extra cellular fluid in children (40% body weight vs 20% in adults)
  • Urine output 1-2 ml/kg/hr
• Hepatic system


  • Liver function is initially immature with decreased hepatic enzyme function, longer duration of action for barbiturates and opioids
• Glucose metabolism


  • Hypoglycaemia is common in stressed neonate, glucose levels should be monitored
  • Glycogen stores are in liver and myocardium, neurological damage may result from hypoglycaemia
  • Infants and older children maintain blood glucose better, rarely need glucose infusions
• Haematology


  • At birth, 70-90% of haemoglobin is HbF, which combines more readily with oxygen but released less readily
  • HbF is protective against red cell sickling
  • Vitamin K dependent clotting factors and platelet function are deficient in first few months, vitamin K given at birth
  • Transfusion recommended when 15% of circulating blood volume has been lost
• Temperature control


  • Large surface area to weight ratio, minimal subcutaneous fat
  • Poorly developed shivering, sweating and vasoconstriction mechanisms
  • Brown fat metabolism required for non-shivering thermogenesis, comprises 2-6% of neonatal body weight
  • More oxygen required for metabolism of brown fat stores
• Temperature control


  • Heat lost during anaesthesia mostly via radiation, also conduction, convection and evaporation
  • Low body temperature causes respiratory depression, acidosis, decreased cardiac output, increased drug duration, decreased platelet function, increased infection risk
• Central nervous system


  • Neonates can appreciate pain, associated with increased HR, BP and neuro-endocrine response
  • Narcotics depress ventilation response to rise in PaCO2
  • Blood brain barrier is poorly formed, drugs cross easily causing prolonged, variable duration
  • Cerebral vessels in preterm infant are thin walled, fragile, prone to intraventricular haemorrhages
• General anaesthesia +/- regional technique. Regional as sole anaesthetic technique is contraindicated in paediatric patients.
• Practical considerations


  • Neonatal surgery and anaesthesia should be performed in specialized centres
  • Different equipment required, may be unfamiliar to occasional paediatric anaesthetist
  • Higher metabolic rate & immature respiratory physiology make desaturation and hypoxia more likely
  • Less able to tolerate changes in temperature and glucose homeostasis
• Pre-operative visit


  1. Develop rapport and trust with child and parent

  2. Take medical and anaesthetic history

  3. Any previous problems with anaesthetics including family history

  4. Allergies

  5. Previous medical problems including congenital anomalies

  6. Recent respiratory illness

  7. Current medications

  8. Recent immunisations

  9. Fasting times

  10. Presence of loose teeth
• Investigations


  • Baseline (include sickling) & others
  • Depends on medical diagnosis & extent of operation
• Weight


  Double birth weight by 4 - 6 months
• Optimisation


  1. Correct and treat any abnormality

  2. Need to know the norm for the different age groups
• Preparation & premedication


  1. Allay anxiety in parents/patient

  2. Familiarisation tour of hospital and equipment

  3. Crossmatch blood

  4. EMLA or ametop cream for venepuncture

  5. Preop fasting guidelines
• Premedication


  • Analgesic - paracetamol, ibuprofen
  • Sedative - midazolam 0.05mg/kg, promethazine 1mg/kg
  • Transnasal fentanyl, midazolam
  • Ketamine 3-8mg/kg orally 30-60 minutes pre-operatively
  • Temazepam 0.5-1mg/kg orally for older children 1 hour pre-operatively
• Warm transport especially for neonates
• Preparation for anaesthesia


  1. Warm the theatre and prepare any warming devices

  2. Prepare emergency drugs such as atropine, adrenaline, and suxamethonium in diluted concentration

  3. Have equipment ready and checked

  4. Oropharyngeal airway, face masks, laryngeal mask, endotracheal tube, laryngoscope and blades, breathing circuit (T piece), monitoring
• Monitoring


  • Precordial / oesophageal stethoscope
  • BP, ECG, pulse oximetry, capnography
  • Temperature, blood loss, urine output
  • Constant observation
• Induction


  1. Calculate drug doses, blood volume and fluid requirements before anaesthesia

  2. Anticholinergic - atropine, glycopyrrolate

  3. Inhalational - halothane or sevoflurane

  4. IV induction - propofol, thiopentone or ketamine

  5. IM - ketamine especially for difficult venous access

  6. Adequate vascular access before surgery

  7. Pre-oxygenation
• Airway management


  • Airway complications are common
  • Head tilt, chin-lift, jaw thrust
  • Position - neutral, sniffing
  • Anatomical features make upper airway obstruction common, use of OPA
  • Intubation - curved, straight blade, deep inhalational, relaxant
• Intubation


  • Straight Magill blades useful in neonates and infants, size 0 blade best in babies less than 4 kg, curved blade usually easier once child is 6-10 kg
  • Uncuffed tubes used until 8-10 years, small leak should be present, too large leak compromises ventilation
• Intubation tube size


  • Size = (age/4) + 4
  • Length = age/2 + 12 (or 15)
  • ID x 3 for oral tube
  • Non-cuffed if age < 8 yrs
  • Tube mandatory in newborn - #3, 3.5 #2.5 (prems)
  • LMA up to 5 kg; 1.5 LMA 5-10 kg; 2 LMA 10-20 kg; LMA 2.5 20 - 30 kg; LMA 3 for over 30 kg
• Maintenance


  1. Add regional analgesia where necessary

  2. Beware of intravenous narcotics in infancy especially ex-premature infants and neonates

  3. Use intravenous fluids for cases with expected blood loss, intra-abdominal, or those taking longer than 30 minutes

  4. Extubation - laryngospasm tends to occur less frequently if child is fully awake

  5. May need to be with child in recovery until fully awake if recovery staff are inexperienced with children
• Fluid balance


  • Accurate fluid administration using burettrol (60 drops = 1 ml)
  • Warm all fluids
  • Isotonic fluid preferred - Ringers' Lactate, Hartmanns, N/S
  • 10% dextrose for prolonged procedures premature, malnutrition (with added saline for neonates)
  • Hypotonic fluids may cause hyponatraemia, encephalopathy
• Temperature control


  1. Increase ambient temperature

  2. Wrap especially head, use radiant heater, warming blanket

  3. Warm fluids and blood

  4. Humidify gases

  5. Monitor temperature
• Reversal


  1. Reverse NMB - neostigmine + atropine / glyco

  2. Pharyngeal toileting

  3. Extubate neonates fully awake, normothermic, normoglycaemic, normotensive and breathing spontaneously

  4. Awake / deep extubation
• Regional anaesthesia not used as sole anaesthetic technique in children < 12 yrs
• Regional anaesthesia


  • Spinal/ caudal - pre-terms and ex-prems, decreased incidence of post-op apnoea, bradycardia, less disruptive to feeding regimen
• Caudal block


  1. Confirmation of block - clinical signs, swoosh test, anal sphincter tone, ultrasound

  2. Complications - dural tap, vascular puncture, urinary retention, LA toxicity, delayed respiratory depression
• Postoperative


  1. Positioning - airway patency, prevent aspiration

  2. Supplementary oxygen till fully awake

  3. Keep warm

  4. Monitoring

  5. Fluid therapy

  6. Post-op analgesia

  7. Commence oral feeds as soon as possible
• Postoperative analgesia


  • Opioids - morphine, codeine
  • NSAIDs - only > 6 months
  • Paracetamol - IV, oral, rectal
  • Regional anaesthesia, nerve blocks, local infiltration
  • May require anti-emetics - ondansetron, dexamethasone
• Safe paediatric anaesthesia requires knowledge of peculiarities of the age groups, adequate preparation, anticipation of potential problems which may occur and the skill to handle them