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Paediatric anaesthesia

Created: 1/9/2006
Updated: 12/1/2007
 

Neonatal anaesthesia

  • Neonate
    • Birth to 28 d, more usefully up to 44 w post-conception
  • Anaesthesia
    • Poorer outcomes with anaesthesia by non-experts
    • Increasing numbers coming to theatre as they survive more commonly
  • Physiology
    • CVS
      • Rate dependent CO
      • Transitional circulation
      • Caused by hypoxia, acidosis, hypercapnia, cold
      • Treat with 100% O2, hyperventilate
      • Little sympathetic tone
      • HbF, p50 17 mmHg
      • Higher haematocrit (depends on cord-clamping time)
      • Blood volume 90 ml/kg
      • Inefficient myocardium due to poorly organized myofibrils
      • Preferential blood supply of highest pO2 to coronary, cerebral circulation
    • Respiratory
      • Large head, short neck
      • Small diameter airway
      • Different laryngeal angle, anterior larynx
      • Edentulous, but tooth buds can be damaged on intubation
      • Short trachea
      • Mouth breathing
      • Increased MV
      • Compliant chest wall, horizontal ribs
      • Noncompliant lungs
      • Prone to apnoea, sensitive to sedative drugs
    • Homeostasis
      • Temperature maintenance
        • High SA to volume ratio
        • Thin skin, rapid evaporative loss
        • Little fat
        • No shivering, but non-shivering thermogenesis
        • Poor vasoconstriction
        • Thermoneutral zone
          • Temperature requiring minimal O2 comsumption to maintain
          • Temperture
          • Neonate 28-32°C at term, higher for prems
        • Maintaining temperature in anaesthesia extremely important
    • Fluids
      • Increased body water
      • High evaporative losses
      • Reduced renal function
      • Low GFR, poor concentrating ability
      • Requirements
        • Day 1-2 40-60 ml/kg/24 h (more for prems up to 200 ml/kg/d)
        • 10% dextrose plus Na+ 2mmol/kg/d, K+ 2-3 mmol/kg/d, Ca2+, Mg2+ as required
        • Continue glucose intraop (or glucose component of TPN)
      • Lowered renal threshold for glucose
      • Risk related to Ca2+ administration: burns if extravasates
  • Diseases
    • HMD
      • Lack of surfactant prior to 34w, later in IDM
      • Increased work of breathing, ground glass X-ray
      • Respiratory distress, cyanosis, tracheal tug, grunting
      • Prevention
        • Reduce risk of prematurity, steroids prior to delivery, tocolytics
      • Treatment
        • Oxygen, CPAP, intubation, ventilation: IPPV, HFJV, oscillation, surfactant, PLV
      • Complications
        • Pneumothorax, IVH, ?NEC, chronic lung disease
    • Oxygen toxicity
      • Retinopathy of prematurity
        • High pO2, vasoconstriction, neovascularization, haemorrhage, scarring, retinal detachment
      • Rare after 30w, PaO2<80 mmHg, <4 h
    • Pulmonary O2 toxicity
      • Free radical generation by high FiO2, worse with IPPV, high FiO2, aim for FiO2<60%, endothelial damage
    • IVH
      • Brain lesion associated with prematurity
      • Neonates: fragile vessels around ventricles: haemorrhage with rise in BP, also
      • Periventricular leukomalacia: ischaemia (watershed area in hypotension) with venous haemorrhage
      • High risk at the time of intubation or volume expansion
      • Graded by extent, detected by u/s through fontanelle
      • Good prognosis unless very large
      • Older babies: cortical lesions more common
    • Apnoea
      • More common with prematurity
      • Central, obstructive or mixed
      • Monitoring post-anaesthetic up to 45w post conceptual in term babies here up to 60w in some units or with ex-prems

    • NEC
      • Abdominal distension, tram tracking, acidosis
  • Anaesthesia
    • Assessment
      • Routine plus prematurity, associated abnormalities, recent course (ventilation, glucose)
    • Transfer
      • Do case in neonates if sick, ?transfer to major hospital
    • Induction in theatre
      • Temperature monitoring and maintenance
      • IV usually not too hard: little fat, some veins invariant
      • Intubation different: view and tube manipulation
      • Monitoring: standard plus ECG, T, SpO2 x 2
      • Laryngoscopy: straight or curved blade, pick up epiglottis or not
      • Tube size, need for leak, PCV, taping technique, nasal vs oral
    • Maintenance
      • Ventilation PCV 5-20 cmH2O 20/min, 10 L/min flow
      • Positioning: flexible, need for head support, lying on wires etc., access usually poor, improved with hand up, oximeter lead available, tubing for IV access
      • Fluids: Albumex 4 (no evidence), continue dextrose
      • Maintenance plus losses: e.g. open abdomen 10 ml/kg/h
    • Extubation
      • Awake
    • Recovery location
      • Depends on procedure and institution
    • Regional
      • No long-term studies, morph infusion OK, paracetamol effective, little use of NSAIDs
    • Fasting time
      • Clear fluids 2 h breast 3 h formula 4 h solids 5 h

Burns management

  • First aid
    • Remove burning debris, extinguish flames, remove from area of smoke
    • ABCDE management
    • Transfer to hospital
  • Primary survey
    • ABCDE
    • Location and severity of burns
      • Rule of 9s for area burned, modified for children
      • Special areas
        • Face, mouth, airway
        • Eyes
    • Associated injuries
      • Inhalational injury
        • More likely if facial burns
        • Cause of injury: smoke, toxic fumes, hot steam
      • Smoke inhalation
        • May have high COHb, give supplemental oxygen
        • Lung injury may produce respiratory distress syndrome
      • Airway burn
        • Develop oedema due to injury
        • Intubate early to secure airway
      • Other injuries
        • Electrical burns, chemical burns, blast injury etc.
        • Circumferential burns may require escharotomy
    • Obtain IV access
      • Large bore in non-burned area
        • May need to be CVC or temporary intraosseous cannula
      • Take baseline bloods
      • Start hydration
        • Hartmann’s solution
          • Maintenance (4/2/1 ml/kg formula), plus
          • Fasting time, plus
          • Burn losses 2-4 ml/kg/% burn over 24 hours
            • Half in 8 hours
        • If young, may require glucose
        • Severe burns are often given some colloid
      • Monitor urine output to assess hydration
        • ≥0.75-1 ml/kg/h desired
      • Give IV analgesia
        • Titrated doses of morphine IV
        • Reduced dose requirement due to fluid depletion and centralized circulation
      • Maintain normothermia
        • Warm environment
        • Warmed fluids
      • Involve surgical/burns unit for on-going management
  • Later issues
    • Infection
      • Prophylactic antibiotics vary by institution
      • Silver sulfadiazine dressings
    • Nutrition
      • Commonly require NGT or IV supplementation
        • Particularly Zn, ω3 fatty acids
  • Anaesthesia
    • Surgery
      • Commonly debridement and grafting
      • Multiple procedures over weeks or months
      • Commonly start about 5 days after injury
    • Preoperative
      • Routine, plus
      • Careful airway assessment
      • Investigation
        • U+E to assess renal function
        • FBE, coagulation
        • Crossmatch for all debridements
    • Induction
      • Good IV access required
      • Commonly spontaneous ventilation with LMA
      • Induction with
        • Thiopentone or propofol commonly
        • Ketamine: less fall in cardiac output than other IV agents
        • Halothane: vasodilator, myocardial depressant, decreased platelet function
          • But still commonly used
      • Muscle relaxation
        • Often not required
        • Increased number of post-junctional receptors
          • Decreased sensitivity to non-depolarizing agents
          • Increased K+ rise with suxamethonium
            • Unsafe from around 1 week to 12 weeks (or healed)
            • Lower dose useable (in theory)
    • Analgesia
      • IV narcotic
      • Nerve blocks for donor sites
        • Posterior cutaneous nerve of thigh
          • 1/4 of the way from ischial tuberosity to greater trochanter
          • In gluteal fold, LOR before reaching muscle or on withdrawal
        • Lateral cutaneous nerve of thigh
          • 2 cm inferior to ASIS between internal oblique and ilium
        • Femoral nerve
          • Lateral to femoral artery in the groin
          • 2 pops on insertion of 45° bevel needle
        • Sciatic nerve
          • Intersection of biceps femoris and sciatic nerve in leg
          • Nerve passes from midpoint of ischial tuberosity and greater trochanter to popliteal fossa
          • Muscle passes from ischial tuberosity to head of fibula

Outline airway problems in choanal atresia, Pierre Robin syndrome, laryngomalacia
 

  • Choanal atresia
    • Congenital atresia of the passage from nose into pharynx
    • Unilateral or bilateral
    • Membranous, cartilaginous or bony
    • Presentation
      • Often detected at birth
      • Respiratory difficulty and hypoxia as neonates are obligate nose breathers
      • Tested for by occlusion of each nostril or passage of cannula
    • Immediate management
      • Oral airway
      • Supplemental oxygen
      • Infants are typically pink and well-oxygenation when crying but hypoxic when feeding or asleep
  • Pierre Robin syndrome
    • Congenital anomaly of the jaw, tongue and palate
    • Cause uncertain
    • Micro- or retro-gnathia, glossoptosis, cleft or arched palate (lip intact)
    • Presentation
      • Obvious deformity at birth
      • Commonly respiratory obstruction when supine
      • May lead to cor pulmonale if untreated
    • Anaesthetic problems
      • Usually difficult intubation
      • Difficulty usually reduced with age as mandible grows
      • May require gas induction and fibreoptic intubation
      • Assistant retracting tongue may be helpful
  • Laryngomalacia
    • Infantile larynx
    • Normal variant laryngeal anatomy
    • Unusually soft cartilaginous structures
    • Epiglottis and surrounding structures cause dynamic obstruction
    • Presentation
      • Stridor developing soon after birth
      • Absent with quiet breathing
      • Increasingly noisy with distress
      • Resolves over first 6 months of life
    • Anaesthetic problems
      • Increased risk of difficult intubation
      • Due to floppy laryngeal structures obscuring view
      • Difficulty with stridor after extubation

Outline your approach to paediatric bronchoscopy


Rigid bronchoscopy

  • Surgery
    • Elective for investigation of masses, respiratory symptoms
    • Semi-urgent for removal of foreign bodies
    • Emergency for massive haemoptysis, acute obstruction
    • May be moderate or high risk
    • Shared airway
  • Preoperative
    • Anaesthetic assessment
      • Routine, plus
      • Careful assessment of mouth opening and potential for dental injury
      • Respiratory function testing if adult and compromised
    • Assessment of indication for bronchoscopy
      • Respiratory compromise
      • Complications of disease, e.g. cachexia from tumour
    • Premedication
      • Anxiolytic, amnestic agent, e.g. benzodiazepine
      • Anticholinergic to reduce secretions
  • Induction
    • Preparation of the airway
      • Local anaesthetic
        • Topical spray or nebulized lidocaine
        • Transtracheal lidocaine
        • Nerve blocks: glossopharyngeal and superior laryngeal
      • Dental guard
    • Monitoring
      • Routine: SpO2, ECG, NIBP
      • Plus arterial line if debilitated
      • Secure IV access for TIVA
    • Induction
      • Propofol plus short-acting relaxant (rocuronium or suxamethonium)
      • Fentanyl to blunt haemodynamic response to bronchoscopy
    • Ventilation
      • Jet insufflation through scope
        • Requires special equipment
        • No anaesthetic agent delivered so requires TIVA
        • Permissive hypercapnea limits duration of procedure
          • Increased risk of arrhythmias
        • Risk of barotrauma if scope occluded
      • IPPV through scope
        • T-piece circuit
        • Allows delivery of volatile agent
        • Intermittent ventilation as scope must be occluded
          • So high FiO2 to allow for apnoea
        • Requires good communication with surgeon
      • HFJV
      • Spontaneous ventilation without relaxant
    • Maintenance
      • Intermittent boluses of IV anaesthetic agent and relaxant or infusion
      • Extreme vigilance for ventilatory compromise
    • Emergence
      • May require intubation and suctioning after procedure until awakening and muscle relaxant reversal
      • Lateral position
      • Risk of haemoptysis after resection or biopsy
  • Postoperative
    • Usually little analgesia required
    • Supplemental oxygen and saturation monitoring
  • Particular considerations in paediatric bronchoscopy
    • Patient population
      • Commonly performed for foreign body aspiration
        • Usually fibreoptic scope is not an option
      • Often semi-urgent
      • Higher metabolic rate, low FRC
        • Rapid onset of hypoxia
        • Particularly good communication with surgeon required
    • Airways
      • Smaller calibre and softer tissue
      • Increased risk of perforation or bleeding
      • Increased risk of laryngospasm during emergence

 

Management of anaesthesia for a teenage scoliosis patient

  • Surgery
    • Elective, high risk surgery
    • Usually in teenage females
    • Extensive thoracotomy, potential for massive blood loss, hypothermia
      • Posterior and anterior approaches
    • May have coexisting neuromuscular disease
    • Secondary respiratory or cardiovascular compromise
    • Increased incidence of MH in this patient population
  • Preoperative
    • Assessment
      • Routine history and examination, plus
      • Scoliosis
        • Airway assessment vital
        • Degree, mobility
        • Complications
          • Respiratory function testing, restrictive deficit
          • Exercise tolerance
      • Investigations
        • FBE, XM, RFT, ABG
        • Autologous blood donation or directed donation
    • Consent
      • Discussion of risks
      • Possible need to wake intraoperatively to test neurological function
    • Premedication
      • Oral benzodiazepine with regard to respiratory function
    • Transport
      • Routine
  • Intraoperative
    • Monitoring and access
      • Usual emergency equipment, plus
        • Difficult airway equipment
        • Rapid infusion equipment available
        • Cell saver if indicated
      • Routine monitoring, plus
        • Arterial line, temperature probe, IDC
        • SSEP or MEP monitor
        • Availability of ABG and Hb measurements
    • Induction
      • Intubation required
        • Thoracotomy and commonly prone
      • Prepare for difficult airway if likely
        • Consider spontaneously breathing induction or awake FOB if required
        • Otherwise routine IV induction
      • Short-acting muscle relaxant if MEP required
    • Maintenance
      • Position
        • Pressure care may be difficult if severe scoliosis
        • Often prone, avoid abdominal pressure causing vertebral vein engorgement
      • Ventilation
        • N2O, O2, low isoflurane dose
          • ± propofol for intraoperative awakening
        • Controlled hyperventilation to cause vasoconstriction
        • One lung often retracted for surgical access: OLV
      • Circulation
        • May be large blood loss
        • Maintain normotension for cord perfusion
          • Fluid loading and pressors
      • Analgesia
        • Consider spinal or caudal morphine either by surgeon or pre-incision
        • Fentanyl bolus plus infusion
    • Emergence
      • Awake extubation, lateral position
        • May require ICU ventilation if severe respiratory compromise
      • Aim for early assessment of neurological function
        • Consider propofol “bookend”
      • Supplemental O2
      • Postoperative CXR and FBE
      • Prolonged immobilization in supine position
        • Chest physiotherapy, ?DVT prophylaxis

Outline the management of anaesthesia for tracheo-oesophageal fistula surgery

  • Tracheooesophageal fistula
    • 1/3000 live births
    • Abnormal communication between oesophagus and trachea
    • Usually associated with oesophageal atresia
    • Classified by topology
      • 85% distal TOF with proximal blind oesophagus
      • 10% oesophageal atresia with no TOF
      • 4% patent oesophagus with TOF (often diagnosed late)
    • Diagnosed shortly after birth
      • Associated with polyhydramnios
      • Failure to pass orogastric tube
      • Failure to feed or aspiration with feeding
    • Surgical management
      • IV hydration
      • Laparotomy, feeding gastrostomy, determination of “gap”
      • Thoracotomy, fistula closure, oesophageal repair
  • Surgery
    • Urgent, high risk
  • Preoperative
    • Assessment
      • History
        • Post-conceptual age, gestational problems
        • Family history
        • Diseases of prematurity
        • VATER abnormalities
          • Vascular (cardiac), vertebral, atresia in GI tract, TOF, renal, radial abnormalities
      • Examination
        • Cardiac, respiratory, general
        • 15-25% incidence of cardiac defects
        • Aspiration common
      • Investigation
        • XM, FBE, U&E or gases
        • CXR
        • Contrast studies
        • Echocardiogram
    • Optimization
      • Hydration, antibiotics for pneumonia, treatment of lung disease
    • Premedication
      • Atropine, paracetamol, antibiotics
  • Intraoperative
    • Monitoring
      • Routine: ECG, NIBP, SpO2, gas analysis, IDC
      • Consider arterial line if unstable or blood gases required
      • Temp probe not in oesophagus
    • Induction
      • Aim to avoid mask IPPV which causes gastric distension
        • Bradycardia and diaphragmatic splinting
      • Aspirate gastrostomy and leave open
      • Topical LA to airway
      • Inhalational induction, spontaneously breathing intubation, or
      • Rapid IV induction
      • ETT placement beyond level of TOF, may be at carina
    • Maintenance
      • Position
        • Laparotomy at 45° head-up
        • Thoracotomy in left lateral position unless right aortic arch (5%)
      • Warming to maintain temperature
      • High FiO2 with potent volatile agent
      • Hand ventilation often required
        • ETT may migrate into fistula with positioning
        • Low lung compliance
        • Gas leak through fistula
        • Retraction of right lung for access
        • Retraction on mediastinum may cause tracheal occlusion
      • Analgesia with LA in wound or intercostal blocks
      • Close attention to blood loss and fluid management
    • Emergence
      • Aim for extubation if stable
        • Less stress on tracheal sutures than IPPV
      • Avoid neck extension: stresses anastomosis
  • Postoperative
    • NICU or neonatal unit level of care
    • SpO2 monitoring
    • Morphine infusion for analgesia
    • Complications
      • Pneumonia, anastomotic leak, tracheomalacia, fistula, reflux, stricture

Paediatric respiratory failure

  • Definition
    • PO2 <60 mmHg, PCO2 >55 mmHg, RR >35
      • At BTPS, FiO2 0.21, worse than normal function
    • Type 1 ventilation failure, acidic pH (raised PCO2)
    • Type 2 oxygenation failure, normal pH
  • Diagnosis
    • Very broad range of clinical symptoms, essentially subjective
    • Apnoea
    • Increased work of breathing, other clinical features
    • Tachypnoea, but rate highly variable and not different between well and ill populations
    • Cyanosis
    • ABG criteria
  • Susceptibility of children
    • Less reserve, higher BMR for size
    • Small airways, less adherent mucosa, readily occluded by oedema
    • Narrow subcricoid level, airways cause 20% of resistance
    • Short horizontal ribs, little increase in AP chest diameter
    • Soft chest wall, poor inspiratory pressure generation
    • Type I muscle fibres, easily fatigued
    • Less alveoli, continued budding to age 1y
    • Few pores of Kohn, more variation in time constants
    • Increased susceptibility to infection, poor cellular immunity, no memory IgG response
    • Birth injuries: asphyxia, aspiration, RDS of newborn
  • Differences from adults
    • Adults recover slowly if at all (80% mortality)
    • Children require only brief ventilation (3-4 days), good outcomes (5-6% mortality)
    • Most deaths in neonates
    • Analysis
      • Cost per year independent life saved
        • Neonate $1500, child $170, adult $1950
      • Cost per survivor
        • Neonate $95,500, child $11,500, adult $27,850
      • Cost per patient intubated
        • $28,650, $8600, $9750
  • Causes of respiratory failure in children
    • Epiglottitis
      • Marked decline due to haemophilus influenzae B vaccination
    • Croup
      • Nebulized adrenaline 0.5 ml/kg of 1:1000 or 0.05 ml/kg of racemic (1:88)
      • Steroids
    • Bronchiolitis
    • Asthma
  • Treatment
    • Ventilation
      • HFPPV
        • 60-100 /min 3-4 ml/kg small dead space
        • Pressure generator with "chopper"
      • HFJV
        • Similar to Sanders jet ventilator
        • 3-5 ml/kg intermittent
        • Trial evidence suggests benefit in neonates by intermediate indicators
      • HFOV
        • 3-15 /s alternates between positive and negative pressure
        • Less than dead space ventilation
        • Rescue ventilation
        • Set rate, delta P, mean airway pressure (FiO2 usually 0.9-1.0)
        • CO2 elimination better with high delta P, low frequency
        • Mechanism of ventilation
          • Pendelluft: differing time constants
          • Assymetric velocity profiles: wave interference between in and out flow at joints
          • Taylor dispersion: wave diffusion at joints?
        • Molecular diffusion: simple diffusion
        • Trial (HIFI) showed no benefit, but done in centres inexperienced with HFOV. Increased IVH, PVL rate. Less risk of long term disease, fibrosis, ECMO etc.
        • Surfactant and NO can be delivered
      • Conventional ventilation is usually the first strategy as HFJV and HFOV are not available in obstetric hospitals
  • ECMO
    • Available if failed ventilation, correctable disease, 80% expected mortality
    • Physiological indices also determine entry
    • Anticoagulation problems
    • Femoro-femoral or femoro-atrial
    • Ventilation for lung recruitment

Common sizes and doses

  • Weight
    • Birth 3-4 kg
    • 1 y 10 kg
    • Age x 2 + 9 up to 9 y (APLS formula: (Age+4) x 2)
    • Age x 3 from 9 y
  • ETT size
    • Prem 2.5 mm
    • Term 3-3.5 mm 9 cm at lips
    • Diameter: (Age ÷ 4) + 4 
    • Length (Age ÷ 2) + 12
  • Induction (single agent unpremedicated elective)
    • Thiopentone 7 mg/kg
    • Propofol 4 mg/kg
    • Ketamine 2 mg/kg
    • Suxamethonium 1.5-2 mg/kg
    • Atracurium 0.5 mg/kg
    • Atropine 10-20 µg/kg
    • Morphine 0.1-0.2 mg/kg
    • Fentanyl 1-3 µg/kg
    • β-Lactams 20 mg/kg
    • Metronidazole 15 mg/kg
    • Reversal
      • Neostigmine 50 µg/kg
      • Atropine 24 µg/kg
  • Resuscitation
    • Adrenaline 10 µg/kg up to 100 µg/kg
    • Calcium 0.1-0.15 mmol/kg (0.2 ml/kg CaCl2, 0.5 ml/kg Ca gluconate)
    • DCR 2-4 J/kg (1 J/kg for atrial arrhythmia)
  • Hypotension
    • Nitroprusside 50 mg/500 ml 0-20 ml/h (=0-33 µg/min, 0-10 µg/kg/min)


Kindly provided by Dr James Mitchell from his pharmacodynamics series


ArticleDate:20060901
SiteSection: Article
 
   
    
                                            
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