FRCA Notes

Down's Syndrome

The curriculum calls for knowledge of 'the implications of paediatric medical and surgical problems including Down’s [syndrome] for anaesthesia'.

Resources

  • Down's syndrome is the commonest chromosomal abnormalities, affecting 1 in 700 live births
  • Risk is closely associated with rising maternal age

  • It's characterised by multiple anatomical and physiological abnormalities that can affect anaesthesia
  • Involvement of a consultant anaesthetist is mandatory

Pathophysiology


Abnormality Incidence
Trisomy 21 95%
Chromosomal translocation 4%
Mosaic trisomy 21 1%

Diagnosis

  • Ante-natal screening is offered routinely during pregnancy, combining:
    • A blood test
    • Ultrasound screening for nuchal translucency
  • Screening occurs between 10 and 20 weeks gestation
  • Those with higher-chance results are offered amniocentesis or chorionic villus sampling

  • Post-natal confirmatory diagnosis involves testing using a patient blood sample (chromosomal karyotype)


Head and neck Face General
Brachycephaly Flat nasal bridge Obesity
Flat occiput Brushfield spots in iris Short stature
Small ears Epicanthic folds Single, transverse palmar (Simian) crease
Short neck Upward slanting, palpable fissures Sandal gap between 1st and 2nd toes
Micrognathia and small mouth
Macroglossia


Airway

  • Atlanto-axial instability (15%)
    • Partly due to ligamentous laxity
    • Can lead to spinal cord compression (2%)
    • Pre-operative assessment should ask for symptoms of spinal cord compression e.g. upper limb paraesthesia
    • Consider flexion/extension views of the C-spine
    • Careful positioning of the head at induction and thereafter

  • Cervical spondylosis
  • Micrognathia, small mouth, obesity, macroglossia and short neck - all contribute to difficult intubation
  • Excessive salivation can obscure the view during laryngoscopy and represents an aspiration risk; may necessitate use of anti-sialagogue pre-medication
  • Sub-glottic and tracheal stenosis can occur (<1%); may indicate a smaller-than-anticipated ETT

Respiratory

  • Increased incidence of obesity may affect FRC

  • Adeno-tonsillar hypertrophy and oro-pharyngeal hypotonia may lead to OSA
  • Elicit features of OSA during pre-operative assessment e.g. STOP-BANG
  • May necessitate post-operative monitoring in a higher-care area e.g. HDU

  • Recurrent respiratory tract infections due to impaired immunity

Cardiovascular

  • Congenital cardiac disease (50%)
  • Left-to-right shunt is common, which will lead to pulmonary hypertension

  • Difficult venous access due to obesity and learning difficulties
  • Reported sensitivity to atropine

Neurological

  • Learning difficulties may lead to a nervous and/or uncooperative patient although, in general, patients with Down's syndrome are 'happy' and compliant
  • Spend time establishing rapport, modifying explanation of anaesthesia due their level of understanding

  • Sympathetic nervous system tends to be relatively immature compared to a child of the same age without Down's syndrome
  • Epilepsy (5 - 10%)

Gastrointestinal

  • Increased frequency of a host of GI problems, some of which will increase aspiration risk under GA, such as:
    • GORD
    • Duodenal atresia (300x more common)
    • Gastric paresis
    • Hirschsprung's disease
    • Pyloric stenosis
    • Meckel's diverticulum
    • Imperforate anus

  • May lower threshold for use of prokinetic or antacid pre-medication, an RSI technique or use of an NG tube

Other

  • Increased incidence of hypothyroidism (50%)
  • Impaired cellular immunity with 12x risk of infection vs. general population
  • Increased incidence of AML (1.5%)
  • Increased incidence of hepatitis B

Perioperative management of the patient with Down's syndrome


History and examination

  • Detailed history to identify congenital problems (e.g. cardiac disease) relevant to anaesthesia
  • Examples include failure to thrive, breathlessness on exertion, 'funny turns', obvious signs of cardiac disease
  • Focussed examination of airway, respiratory and cardiovascular systems

Investigations

  • An ECG, TTE and Cardiology opinion in children with Down's syndrome to exclude congenital cardiac disease
  • Screening ± further investigation for OSA
  • Lateral flexion/extension C-spine XR if signs of atlanto-axial instability e.g. limited neck movement, neck pain, altered gait, abnormal neurology, bladder/bowel dysfunction
    • May demonstrated an increased atlanto-dental distance (>4mm)

Optimisation

  • First on list to minimise distress
  • Consider various pre-medications:
    • Anxiolytic
    • Pro-kinetic
    • Antacid
    • Anti-sialagogue
  • Apply EMLA/ametop to reduce distress associated with cannulation
  • Plan for higher care area post-operatively if required e.g. OSA; severe OSA precludes day-case surgery

Monitoring and access

  • AAGBI
  • May have difficult IV access

Anaesthetic technique

  • Anticipate difficult airway and have difficult airway trolley available
  • Anticipate rapid desaturation due to obesity and OSA
  • Use smaller than predicted ETT (0.5 - 1mm ID lower) owing to potential for sub-glottic stenosis
  • May need RSI technique due to aspiration risk
  • Beware gas induction as delayed sympathetic nervous system development can lead to profound bradycardia at high end-tidal volatile concentrations

Care bundle

  • Ensure normothermia
  • Age-appropriate VTE prophylaxis
  • Consider need for prophylactic antibiotics in patients at risk of infective endocarditis

  • Multi-modal analgesia; caution with opioids in presence of OSA
  • Multi-modal anti-emesis

  • Close monitoring ± parent/carer presence
  • Low threshold for HDU environment

  • May require simple airway manoeuvres, Guedel or lateral positioning to maintain airway due to post-anaesthetic hypotonia prior to regaining full consciousness
  • Reported post-extubation stridor in up to 33%; use humidified oxygen, adrenaline nebuliser and steroids