Obstructive sleep apnoea

 

Disease:

Pathophysiology

·      Hypotonia

·      Obstruction

·      Apnoea

·      Hypoxaemia

·      SNS +++

·      Partial arousal

·      Restored patency

Complications

Vessels:

·      Systemic hypertension

·      Pulmonary hypertension

Heart:

·      Arrhythmias (AF)

·      Cor pulmonale

·      Coronary artery disease

Blood:

·      Polycythaemia

·      Stroke

 

Assessment:

Hx/Ex

STOPBANG: (3 confers high risk)

·      Snoring

·      Tired

·      Observed apnoea

·      Pressure (hypertension)

·      BMI >35

·      Age >50

·      Neck >40cm

·      Gender (male)

Red flags:

·      Apnoeic period

·      Heroic gasps

·      Daytime somnolence

(true for adults?)

Ix

Blood tests:

·      ↑Hb

·      ↑Hct

Sleep studies:

·      Mild: AHI 5-15

·      Mod: AHI 15-30

·      Sev: AHI >30

TTE:

·      RVSP

·      TAPSE

 

Issues:

Airway

Difficulties:

·      Bag-mask ventilation

·      Intubation (±extubation)

Reasons:

·      If slim: anterior larynx

·      If obese: crowded cavities, difficult positioning

Breathing

Danger:

·      Sedation

·      Respiratory depression

·      Complete airway obstruction

·      Death

Risk factors: = send to HDU

·      Opioids ++

·      Benzodiazepines

·      Severe OSA (AHI >30 or red flags)

·      Morbidly obese

·      Abnormal upper airway

·      Major comorbidities

Circulation

If pulmonary hypertension:

·      Risk of RV ischaemia

·      Risk of RV failure

 

Anaesthesia:

Intra-op

Anaesthesia:

·      Awake > general > sedation

Airway:

·      Expect difficulty, make plan ABC

·      Use VL first line

Post-op

General care:

·      CPAP

·      ±HDU

Analgesia:

·      Use regional

·      Use non-opioids

·      If opioid, use fentanyl PCA

·      Ensure no benzos

 

Obesity hypoventilation syndrome

 

Disease:

Pathophysiology

·      Obesity

·      Impaired mechanics

·      Chronic hypoventilation

·      Chronic hypercapnoea ± hypoxia

Complications

·      Pulmonary hypertension

·      Cor pulmonale

 

Assessment:

Hx/Ex

·      STOPBANG without the apnoeas

·      OSA in 90%

·      PHTN in 66%

·      90% also have OSA

Ix

ABG:

·      ↑PaCO2 >45

·      ↑HCO3

·      ↓PaO2

·      Normal A-a gradient

Sleep studies:

·      Continuous CO2 monitoring required

·      OHS worse during sleep

Cardiac investigations:

·      ECG: signs of RVH

·      TTE: PHTN, RVH, RV failure

 

Issues:

Airway

 

Breathing

 

Circulation

 

 

Anaesthesia:

Intra-op

Anaesthesia:

·      Awake > general > sedation

Airway:

·      Expect difficulty, make plan ABC

·      Use VL first line

Breathing:

·      Aim PaCO2 at patient’s normal

·      ↑HCO3 4mmol/L = ↑PaCO2 10mmHg

Post-op

General care:

·      CPAP

·      HDU if high risk

Analgesia:

·      Use regional

·      Use non-opioids

·      If opioid, use fentanyl PCA

Other medication:

Avoid benzodiazepines

 

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