1.1 Epilepsy and OSA

Question 1

History

You have been asked to review a 36-year-old man who has fallen
against a radiator and sustained a penetrating injury to his right eye.

He has a past medical history of learning difficulties and poorly controlled
epilepsy with one to two fits per week, on average. He has also recently been referred to a sleep studies clinic.

He is conscious in A&E and responding to questions appropriately, despite being clearly distressed. The caregiver who is with him did not witness the fall but says that other than his eye injury, he appears to be otherwise acting normally.

summarise the case.

Answer 1

• 36-year-old man with penetrating eye injury
• Poorly controlled epilepsy and learning difficulties
• Untreated obstructive sleep apnea (OSA)
• Obese with potentially difficult airway
• Potential liver and renal function impairment due to antiepileptic drugs

Question 2

comment on the chest X-ray.

Answer 2

Obvious abnormality is the presence of a vagal nerve stimulator
* Reduced lung volumes
* Lung fields otherwise clear except haziness in left lower border
* Normal heart borders, borderline cardio thoracic ratio

Question 3

How does a vagal nerve
stimulator work?

Answer 3

1 Pulse generator/stimulator that sends regular,
mild electrical stimuli to the vagus nerve

2 Used in drug-resistant epilepsy,
particularly partial seizures and
treatment-resistant depression

3 Often not immediately effective and
rarely prevents seizures entirely

4 Battery-powered so requires changing every 5–10 years

Question 4

What are the anaesthetic implications for patients with epilepsy?

Answer 4

1 * Increased incidence of seizures perioperatively
—multifactorial

2* Continue anti-epileptic drugs (AEDs) with
minimal fasting period
(or use parenteral alternative)

3 * Caution regarding AEDs—hepatic enzyme metabolism
and other drug interactions

Question 5

correlate and comment on the
ABG and sleep studies result

Answer 5

low po2 high pco2 and bicarb with polycythaemia

• Hypoxaemia, hypercapnia, and polycythemia, related to OSA
• Metabolic compensation (chronic disease)
• Apnea/hypopnea index indicates severe OSA

Question 6

What is AHi? How can you
classify the severity of osA?

AHI

Answer 6

1. AHi

AHI is the number of apneas or hypopneas recorded
during the study per hour of sleep.

It is generally expressed as the number of events per hour.

Based on the AHI, the severity of oSA is classified as follows:

1 None: < 5 per hour

2 Mild: 5–14 per hour

3 Moderate: 15–29 per hour

4 Severe: ≥ 30 per hour

Question 7

O2 Desats during polysomnography + Severity

Answer 7

Oxygen Desaturation

Desaturations are recorded during polysomnography.

Although there are no generally accepted classifications

for severity of oxygen desaturation,

reductions to not less than 90% usually are considered mild.

Dips into the 80%–89% range can be considered moderate,

and those below 80% are severe.

Question 8

What symptoms suggest a diagnosis of OSA?

Answer 8

1 Snoring

2 Daytime somnolence

3 Early morning headaches

4 Dry or sore throat upon waking

5 Poor concentration and irritability

Question 9

What scoring systems are used for screening for osA?

Answer 9

STOP BANG

Epworth Sleepiness Scale

Berlin Questionnaire

Question 10

STOP BANG

Answer 10

• Snoring
• Tired—daytime tiredness or fatigue
• Observed apnoea during sleep
• Pressure (blood)—treatment for hypertension
• BMI more than 35 kg/m2
• age over 50 years
• neck circumference greater than 40 cm
• Gender—high prevalence in male gender

<2 = low risk
>5 = High Risk

3-4 = Further invx may be required

Question 11

Epworth Sleepiness Scale

Answer 11

Epworth Sleepiness Scale

• The questionnaire looks at the chance of
  falling asleep on a scale of increasing probability
  from 0 to 3 for eight regular activities during their
  daily lives.
• The scores for the eight questions are
  added together to obtain a single number.
• Normal: 0–9;
  mild to moderate sleep apnea: 11–15;
  severe sleep apnea: 16 and above

Question 12

What are the risk factors for OSA?

Answer 12

1 Obesity

2 Male gender

3 Age > 40 years

4 Neck circumference > 17 inches

5 Family history of OSA

Question 13

What are the complications or associations of OSA?

Answer 13

1. Cardiac
   * Treatment-resistant hypertension
   * Congestive heart failure
   * Ischaemic heart disease
   * Atrial fibrillation
   * Dysrhythmias
2. Respiratory
   * Asthma
   * Pulmonary hypertension
3. Gi
   * Gastro-oesophageal reflux
4. neurological
   * Stroke
5. Metabolic
   * Type II Diabetes Mellitus
   * Hypothyroidism
   * Morbid obesity

Question 14

What are the anaesthetic implications for patients with osA?

Answer 14

1. sedative premedication

• Avoid sedating premedication
• Alpha-2 adrenergic agonist
  (clonidine, dexmedetomidine)
  may reduce intraoperative anaesthetic requirements
  and have an opioid-sparing effect
  __________________________________

2. Difficult airway
   * Ramp from scapula to head as patient is obese

• Adequate preoxygenation
• Associated gastro-oesophageal reflux disease—consider proton pump
  inhibitors, antacids, rapid sequence induction with cricoid pressure

___________________________________

3. Analgesia

• Minimise use of opioids for the fear of respiratory depression
• Use short-acting agents (remifentanil)
• Regional and multimodal analgesia
  (NSAIDs, acetaminophen, tramadol,
  ketamine, gabapentin, pregabalin, dexamethasone)

4. Anaesthetic technique
   * Carry-over sedation effects from
   longer-acting intravenous sedatives and
   inhaled anaesthetic agents

• Use propofol/remifentanil for maintenance of anaesthesia
• Use insoluble potent anaesthetic agents (desflurane, sevoflurane)
• Use regional blocks as a sole anaesthetic technique (not in this case!)

______________________________

4. Monitoring
   * Use intraoperative capnography for monitoring
   of respiration (mandatory anyway!)

• Arterial line if OSA associated with cardiac dysfunction

________________________________

5. Postoperative period

• Verification of full reversal of neuromuscular blockade
• Ensure patient fully conscious and cooperative prior to extubation
• Non-supine posture for extubation and recovery
• Resume use of positive airway pressure device
  with close monitoring post-operatively
• May require HDU/ITU admission

Question 15

What are your concerns of anaesthetising this patient now?

Answer 15

1. • Newly diagnosed hypertension
2. • Urgency of surgery—
     discuss with surgeons but likely
     to be urgent rather than an emergency
3. • Exclude other trauma, especially neck and intracranial
4. • Anaesthetic technique in view of potentially difficult airway
5. • Control of intraocular pressure
6. • Post-operative care—will need HDU/ITU bed

Question 16

What would be your induction technique and airway
management plan for this patient?

Answer 16

• Ideally get help—two anaesthetists present
• Awake fibreoptic intubation unlikely to be suitable
  (coughing, distressed, learning difficulties)
• Allow for adequate starvation time if possible
• Preoxygenate in ramped position
• Modified rapid sequence induction with rocuronium
  (ensuring sugammadex available)
  may be most appropriate
• Use of video laryngoscopy may be ideal

Question 17

The patient is now extubated and in recovery.
You are called to review him because he is agitated.

What are the possible causes and how might you manage them?

Answer 17

1. • Pain: analgesia

2.* Inadequate reversal of muscle relaxant:
check the TOF count and use reversal

3. • Drug-induced,
     e.g. atropine, opioids:
     review anaesthetic chart
4. • Hypercapnia:
     treatment of sedative/opioid toxicity,
     airway manoeuvres,
     and adjuncts if obstructed
5. • Hypoxia: O2, airway manoeuvres,
     and adjuncts if obstructed
6. • CPAP likely to be contra-indicated due to eye injury

Question 18

What is your approach to deep vein thrombosis (DVt) prophylaxis in this patient?

Answer 18

1. • High risk for DVT—obese, polycythaemic
2. • Mechanical prophylaxis
3. • Early mobilisation
4. • Balance risk versus benefit of anticoagulation in eye trauma—
     get specialist help regarding the plan