Obstructive Sleep Apnoea

Question 1

A 43-year-old male patient presents to the preoperative assessment clinic prior to day case inguinal hernia surgery. He is a smoker and has a BMI of 47. You are asked to review this patient as his blood pressure is 174/96.
What are your anaesthetic concerns regarding this patient?

Answer 1

• This patient has a raised BMI. Concerns include: an increased incidence of a difficult airway; the need for additional anaesthetic and surgical equipment, staffing and time perioperatively; and the physiological consequences and comorbidities secondary to his obesity.
• Probable untreated hypertension in a high-risk patient.
• There is a high likelihood of undiagnosed (and hence untreated) obstructive sleep apnoea (OSA).
• The patient is a smoker. The physiological and pathological consequences of smoking cause an increased risk of a difficult airway and challenging ventilation; higher incidence of infection; and poor wound healing postoperatively.
• The need for postoperative high dependency or intensive care should be considered early. This patient may not be a good candidate for day case surgery.

Question 2

What is OSA syndrome?

Answer 2

• OSA is a condition where complete or partial airway obstruction during periods of sleep leads to a decrease in airflow and subsequent desaturation.
• OSA syndrome is defined as a confirmed diagnosis of OSA together with increased daytime somnolence.
• OSA is thought to affect up to 1.5 million adults in the UK, with up to 85% of these being undiagnosed and therefore untreated.

Question 3

What measures are involved in sleep studies?

Answer 3

• Sleep studies (polysomnography) can be used as an objective assessment of the presence and degree of OSA. Measurements include:
• ECG.
• EEG.
• Oxygen saturations.
• Airflow.
• Eye movements.
• Electromyography (EMG).

Question 4

What is hypopnea?

Answer 4

• A hypopnoea is defined as more than 30% reduction in airflow lasting for longer than 10 seconds, with at least a 4% decrease in oxygen saturations.
• Apnoea is complete cessation or flow reduced to 10% for 10 seconds

Question 5

What are the risk factors for the development of OSA?

Answer 5

Anatomical:
* Increased neck circumference (>40 cm).
* Enlarged tonsils/adenoids/tongue.
* Craniofacial abnormalities.

Comorbidities:
* High BMI (>35).
* Hypertension.
* Diabetes mellitus.
* Asthma.
* Neuromuscular disorders.
* Parkinson’s disease

Other:
* Male.
* Age (40–70 years old).
* Family history.
* Smoker.
* Alcohol excess.
* Pregnancy.
* Low physical activity levels.

Question 6

What are the key considerations in your anaesthetic plan for this patient?

Pre-operative:

Answer 6

• This is a complex patient with numerous comorbidities presenting for non-urgent surgery, so the procedure should be delayed until the patient has been reviewed by the relevant teams:
• GP review for a potential new diagnosis of and treatment for
  hypertension.
• Assess for possible OSA (using the STOP-BANG screening tool) and refer for sleep studies. If a diagnosis of OSA is made, the patient should undergo at least 3 months of home CPAP prior to consideration for surgery.
• Smoking cessation advice and encouragement.
• Weight loss advice and encouragement.
• Encourage an increase in physical activity through exercise regimes.
• When surgery is reconsidered for this patient, a complex and thorough preoperative anaesthetic history, examination and appropriate investigations are required once the above have been completed, with a focus on the airway and cardiovascular system. Tis may include an ECG, echo and CPET.

Question 7

What are the key considerations in your anaesthetic plan for this patient?

Intraoperative and postoperative:

Answer 7

Intraoperative:
* Avoid sedative premedication.

• Prepare for a difficult airway/intubation with an airway plan, appropriate equipment and adequate senior support.
• Ensure that there is a plan for failed intubation and/or oxygenation.
• Prioritise non-opioid base analgesia during the perioperative period.
• Use regional anaesthesia where possible (for both analgesia and anaesthesia).

Postoperative:
* If a general anaesthetic is used, consider extubating the patient onto his own CPAP machine with a prolonged stay in recovery, with continuous sats monitoring and supplemental oxygen.
* Consider high dependency care postoperatively.

Question 8

What are the potential complications associated with OSA?

Answer 8

• Cardiovascular: hypertension, arrhythmias, myocardial infarction and right-sided cardiac failure.
• Poor cognitive function and mood disorders.
• Impaired glucose tolerance/type II diabetes mellitus.
• Sexual dysfunction.