Anaesthesia for parkinsons disease 10m
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I now have comprehensive content from Morgan & Mikhail. Let me compile the full, detailed 10-mark answer on anaesthesia for Parkinson's disease.
Anaesthesia for Parkinson's Disease
Pathophysiology Relevant to Anaesthesia
Parkinson's disease (PD) is a neurodegenerative disorder affecting individuals aged 50-70 years (prevalence ~3% in North America). It results from progressive loss of dopamine in the nigrostriatal pathway. Loss of dopamine increases GABA activity in basal ganglia nuclei, causing inhibition of thalamic and brainstem nuclei, which in turn suppresses the motor cortex - producing the cardinal features:
- Bradykinesia
- Rigidity (cogwheel/lead-pipe)
- Postural instability
- Resting tremor (pill-rolling)
- Facial masking, hypophonia, dysphagia, gait disturbances
- Progressive course may lead to Lewy body dementia
- Autonomic dysfunction - orthostatic hypotension, cardiac dysrhythmias
Drugs Used in Parkinson's Disease (Anaesthetically Relevant)
| Drug | Class | Anaesthetic Relevance |
|---|---|---|
| Levodopa (+ carbidopa) | Dopamine precursor | Short half-life; must NOT be withheld perioperatively |
| Dopamine agonists (bromocriptine, pramipexole, ropinirole) | DA agonist | Continue perioperatively; side effects include nausea, orthostatic hypotension, hallucinations |
| MAO-B inhibitors (selegiline, rasagiline) | MAO-B inhibitor | Risk of serotonin syndrome with pethidine/meperidine |
| COMT inhibitors (entacapone) | Prevent levodopa decarboxylation | Continue perioperatively |
| Anticholinergics (trihexyphenidyl) | Antimuscarinic | Useful for tremor; may cause postoperative confusion |
| Amantadine | DA releaser/NMDA antagonist | Continue perioperatively |
Preoperative Assessment
1. Neurological evaluation:
- Assess severity and current status of PD
- Document all anti-Parkinson medications and timing
- Assess swallowing function - dysphagia increases aspiration risk
- Assess cognitive function (dementia present?)
2. Cardiovascular:
- Orthostatic hypotension is common (autonomic instability)
- Levodopa causes cardiac irritability and sensitizes to catecholamines
- Baseline ECG
3. Respiratory:
- Aspiration risk from dysphagia and impaired laryngeal reflexes
- Restrictive pattern from rigidity of chest wall musculature
- Assess for obstructive sleep apnea
4. Medications:
- Anti-Parkinson drugs must be continued up to and including the morning of surgery because of the short half-life of levodopa
- Abrupt withdrawal can cause worsening rigidity that may interfere with ventilation, or even precipitate a neuroleptic malignant syndrome-like state
Drugs to AVOID in Parkinson's Disease
These drugs have antidopaminergic activity and can exacerbate PD symptoms:
| Drug | Mechanism/Reason to Avoid |
|---|---|
| Metoclopramide | Dopamine antagonist - worsens rigidity/symptoms |
| Droperidol | Butyrophenone - dopamine antagonist |
| Haloperidol | Butyrophenone - dopamine antagonist |
| Phenothiazines (chlorpromazine, prochlorperazine) | D2 blockade |
| Pethidine (meperidine) | Risk of serotonin syndrome with MAO-B inhibitors (selegiline) |
| Metoclopramide/domperidone | Antiemetic dopamine antagonist |
Safe alternatives for anti-emesis: Ondansetron (5-HT3 antagonist), domperidone does not cross BBB (relatively safer)
Intraoperative Management
Induction
- Induction in patients on long-term levodopa may cause either marked hypotension or hypertension
- Mechanisms: relative hypovolemia, catecholamine depletion, autonomic instability, catecholamine sensitization
- Hypotension - treat with direct-acting vasopressors such as phenylephrine rather than ephedrine (ephedrine releases catecholamines and response is unpredictable with catecholamine depletion)
- Standard induction agents (propofol, thiopentone) are acceptable
Airway
- High aspiration risk - consider rapid sequence induction (avoid succinylcholine if immobility-related hyperkalemia suspected)
- Dysphagia predisposes to silent aspiration
- Difficult bag-mask ventilation possible due to rigidity
- Avoid metoclopramide for aspiration prophylaxis - use ranitidine/PPI instead
Maintenance
- All standard volatile agents (sevoflurane, isoflurane) are acceptable
- TIVA with propofol is often used for DBS surgery
- Neuromuscular blockade: Response is generally normal
- Ketamine - may be useful but catecholamine-releasing properties require caution
- Nitrous oxide - acceptable
- Opioids - most are safe; avoid pethidine if patient on MAO-B inhibitors (risk of serotonin syndrome: hyperthermia, agitation, myoclonus)
Monitoring
- Standard ASA monitoring
- Careful hemodynamic monitoring due to cardiovascular instability
- Temperature monitoring (hyperthermia possible)
Positioning
- Rigidity may make positioning difficult
- Careful padding of pressure points
Deep Brain Stimulation (DBS) Surgery
A major surgical intervention for PD that requires special anaesthetic considerations:
Two approaches:
- Awake craniotomy - patient sedated (dexmedetomidine preferred) but awake for electrode placement; allows real-time neurophysiological testing. General anesthesia alters the threshold for stimulation, making correct electrode placement difficult.
- General anaesthesia approach - TIVA with propofol + remifentanil + LMA; infusions discontinued and LMA removed for electrode placement; reanesthetized once leads are implanted
Dexmedetomidine advantages for DBS:
- Provides sedation without suppressing neurophysiological activity
- Does not suppress microelectrode recordings significantly
- Patient can cooperate during electrode placement
Postoperative Management
1. Restart anti-Parkinson medications as soon as possible
- Resume oral levodopa at the first opportunity
- If oral route not available, nasogastric tube administration
- No IV formulation of levodopa available; this is a critical management issue
2. Respiratory care:
- Extubate when fully awake (high aspiration risk)
- Monitor for respiratory complications - rigidity can impair ventilation
- Physiotherapy for chest
3. Cardiovascular:
- Monitor for orthostatic hypotension
- Maintain adequate hydration
4. Symptom management:
- If acute worsening of tremor/rigidity occurs: anticholinergics (atropine) or antihistamines (diphenhydramine) may be used
- Diphenhydramine may provide intraoperative sedation in patients with tremor
5. Avoid:
- Dopamine antagonist antiemetics (use ondansetron)
- Butyrophenones for agitation/PONV
6. Regional anaesthesia considerations:
- Neuraxial anaesthesia is not contraindicated but autonomic instability increases hypotension risk with spinal/epidural
- Regional techniques may be preferred for peripheral procedures to avoid systemic drug interactions
Summary Table: Key Perioperative Principles
| Phase | Key Points |
|---|---|
| Preop | Continue all PD meds; assess swallowing, cognition, CVS; check for orthostatic hypotension |
| Induction | Anticipate hemodynamic instability; use phenylephrine for hypotension |
| Airway | High aspiration risk; avoid metoclopramide for prophylaxis |
| Maintenance | All volatiles acceptable; avoid pethidine (MAO-B inhibitor interaction); response to NMBs normal |
| Antiemetics | Use ondansetron; AVOID metoclopramide, droperidol, haloperidol |
| Postop | Restart PD meds immediately; monitor respiratory function; avoid dopamine antagonists |
| DBS surgery | Awake (dexmedetomidine) or GA (TIVA) technique; GA alters stimulation threshold |
Based on: Morgan and Mikhail's Clinical Anesthesiology, 7e, Chapter 28 (Anesthesia for Patients with Neurologic Disease)
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