Parkinson's disease for awake deep brain stimulator insertion71-year-old man, 74 kg, for awake deep brain stimulator insertion

The patient

The examiner asks

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1. Consider

   What are your concerns?

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   • A 71-year-old with advanced Parkinson's, for awake DBS insertion semi-sitting in a head frame. Patient
   • At 71 with Parkinson's he may be frail; I assess frailty, and his delirium risk is high.
   • His morning levodopa is held, so rigidity and tremor will build through the case. Disease
   • Dysphagia and drooling mean aspiration risk, with an airway I can barely reach. Airway
   • Orthostatic hypotension: his systolic drops 34 mmHg when he sits up. Disease
   • He breathes spontaneously, head up, so venous air embolism is possible. Surgery

2. Prepare

   How do you prepare?

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   • Drug plan agreed with the neurosurgeon: which doses are held, and when levodopa restarts. Disease
   • Frame key or spanner taped to the frame; I know how to take it off. Airway
   • LMA and fibrescope ready; the frame can block mask ventilation and laryngoscopy.
   • No metoclopramide, droperidol or prochlorperazine for him; ondansetron is fine. Disease
   • Precordial Doppler and capnography for air; fluids to offset his orthostatic drop. Surgery

3. Plan

   How will you sedate him?

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   • Minimal sedation, so recordings are reliable and he keeps his own breathing. Disease
   • No benzodiazepines; propofol only early, with a long gap before recording.
   • Low-dose dexmedetomidine; remifentanil is reasonable but can mask his tremor, so it's off for testing.
   • Hypertension treated promptly to cut the risk of intracerebral haematoma. Surgery
   • Long case: careful positioning and padding for comfort. Patient
   • Levodopa restarts as soon as testing ends, by mouth or nasogastric tube. After surgery

4. Crisis

   During burr-hole drilling he coughs and says he's breathless; SpO2 falls to 88% and ETCO2 from 36 to 22 mmHg. What do you do?

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   • Venous air embolism through the burr hole until proven otherwise. (Crisis)
   • Surgeon floods the field with saline and waxes the bone edges.
   • I don't ask him to breathe deeply; that pulls more air in.
   • 100% oxygen; fluids and a vasopressor for his pressure.
   • Head lowered, left side down, if the frame allows.
   • If severe: lay him supine, support the circulation, frame off if I need the airway.

5. Crisis

   Two hours in, he is rigid, sweating and distressed; temperature 38.4 °C, HR 118, BP 170/96. What do you do?

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   • Levodopa withdrawal, heading towards parkinsonism-hyperpyrexia syndrome. Crisis
   • Testing stops; I tell the surgeon that his own drug is the treatment.
   • Levodopa by nasogastric tube now; transdermal rotigotine if he can't absorb it.
   • Rigidity can stop him breathing or coughing; airway kit and frame key at hand.
   • Cool him and support his circulation.
   • Untreated, this syndrome kills up to 20%; monitored bed afterwards. After surgery