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 700-900 live births
  • Risk is closely associated with rising maternal age
  • Median life expectancy 60yrs

  • Patients with Down's syndrome often require surgery owing to multiple congenital abnormalities
  • These anatomical and physiological abnormalities can influence the conduct of anaesthesia

Pathophysiology


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

  • Although the genes on the additional chromosome are normal, as are their products, there is dysregulated gene expression across the whole genome
  • The degree of altered gene expression is affected by other genetic and environmental factors, leading to phenotypic variation amongst patients

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 karyotyping)


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

  • Difficult airway management should be anticipated on account of multiple changes:
    • Micrognathia/retrognathia
    • Small mouth, nasopharynx and oropharynx
    • Macroglossia
    • Midface hypoplasia
    • Short neck
    • Tonsillar and adenoid hypertrophy
    • Laryngomalacia
    • Vocal cord palsy secondary to recurrent laryngeal nerve injury during cardiac surgery (8-16%)

  • Smaller airways
    • Airways are 1.2 - 3.2mm smaller in Trisomy 21 patients than unaffected children
    • Congenital sub-glottic ± tracheal stenosis (1.3%)
    • Acquired sub-glottic stenosis due to repeated intubation for surgeries (4.6%)
    • A smaller-than-anticipated ETT may be required
  • Excessive salivation can obscure the view during laryngoscopy & represents an aspiration risk; may necessitate use of anti-sialagogue pre-medication

C-spine and MSK

  • 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
  • Down syndrome-associated inflamatory arthritis

Respiratory

  • Increased incidence of obesity, which affects FRC

  • Central and/or obstructive sleep apnoea (45%)
    • Adeno-tonsillar hypertrophy and oro-pharyngeal hypotonia may lead to OSA
    • One should 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

  • Cardiovascular disease is a leading cause of morbidity and mortality in patients with Down's syndrome
  • Congenital cardiac disease (approximately 50%)

  • Persistent pulmonary hypertension of the newborn (1.2 - 9.7%)
  • Pulmonary hypertension (6 - 38%)
    • Left-to-right shunt is common, which will lead to pulmonary hypertension
    • Pulmonary hypertension occurs earlier and more severely than in non-Trisomy 21 patients with similar cardiac abnormalitie
  • Biventricular systolic and diastolic dysfunction on TTE is common even in the absence of structural abnormalities, although not necessarily symptomatic

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

Neurological

  • Mild-moderate 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%)
  • Psychiatric diagnosis (18%)
  • Autistic spectrum disorder (up to 7%)
  • Disruptive behaviours
    • ADHD (6.1%)
    • Aggressive behaviour (6.5%)

  • Ocular manifestations such as strabismus, amblyopia, cataracts, glaucoma, optic nerve disease, and retinal disease
  • Hearing loss due to repeated chronic otitis media ± chronic middle ear effusions

Gastrointestinal

  • Increased frequency of a host of GI problems, some of which will increase aspiration risk under GA, such as:
    • GORD
    • Duodenal atresia (3.9%; 300x more common than baseline population)
    • Gastric paresis
    • Tracheo-oesophageal fistula (0.4%)
    • Hirschsprung's disease (0.8%)
    • Pyloric stenosis (0.3%)
    • Meckel's diverticulum
    • Imperforate anus (1%)

  • 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%) and ALL
  • Transient abnormal myelopoiesis (10%) in neonates
  • 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, OSA) 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 or assess 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
  • Involvement of senior (consultant) anaesthetic and surgical personnel
  • 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 so have ultrasound present

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
  • Careful positioning pre-induction and avoidance of excessive head/neck movement to reduce risk of neurological injury
  • Full reversal of NMBA prior to emergence

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