Anaesthesia for patients with pshiatric disorders for MD Anaesthesia exam

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Anaesthesia for Patients with Psychiatric Disorders

MD Anaesthesia Comprehensive Notes

1. GENERAL PRINCIPLES

The perioperative management of patients with psychiatric disorders is guided by three core concerns:

Drug interactions between psychotropic medications and anaesthetic agents
Withdrawal risk if medications are abruptly stopped
Psychiatric relapse which can worsen perioperative outcomes

Key rule: Most psychotropic medications (antidepressants, antipsychotics, benzodiazepines, anticonvulsant mood stabilisers) should be continued through the perioperative period to prevent symptom exacerbation and relapse. The exception is lithium and irreversible MAOIs (with caveats below).

Miller's Anesthesia, 10e, p. 4036

2. MONOAMINE OXIDASE INHIBITORS (MAOIs)

Classification

Type	Agent	Reversibility	Duration of effect
Non-selective irreversible	Phenelzine, Tranylcypromine, Isocarboxazid	Irreversible	2-3 weeks
Selective MAO-B irreversible	Selegiline (low dose)	Irreversible	~2 weeks
Reversible inhibitor of MAO-A (RIMA)	Moclobemide	Reversible	<24 hours

Perioperative Management

Traditional advice: Stop irreversible MAOIs 2-3 weeks before elective surgery
Modern advice (preferred): Continue MAOIs and adapt the anaesthetic plan accordingly. Discontinuation risks include severe depression relapse and documented cases of suicide
Reversible MAOIs (moclobemide): Can be stopped 24 hours before surgery
Miller's Anesthesia, 10e, p. 4036

Critical Drug Interactions

1. Serotonin Syndrome - the most dangerous interaction

Caused by excess serotonin at the 5-HT1A receptor. MAOIs block serotonin breakdown; serotonergic drugs flood the synapse.

Clinical features	Autonomic	Neuromuscular
Confusion, agitation	Hyperthermia	Hyperreflexia
Diaphoresis	Tachycardia, BP instability	Myoclonus
Diarrhoea		Tremor, ataxia

Drugs CONTRAINDICATED with MAOIs (serotonin syndrome risk):

Meperidine (pethidine) - the classic lethal combination; absolutely contraindicated
Tramadol, methadone (phenylpiperidine opioids - weak SRI activity)
Dextromethorphan
SSRIs, SNRIs, TCAs
Methylene blue (potent reversible MAOI itself - can cause SS even alone)
Linezolid (antimicrobial with MAOI properties)

Safe opioids with MAOIs:

Morphine, codeine, oxycodone, buprenorphine (not serotonin reuptake inhibitors)
Alfentanil and remifentanil - safe without complications
Miller's Anesthesia, 10e, p. 2896

2. Excitatory (hypertensive) reaction

Indirect-acting vasopressors (ephedrine, dopamine) can cause severe hypertension due to accumulated catecholamines. Use only direct-acting agents (phenylephrine, noradrenaline)
Miller's Anesthesia, 10e, p. 4036

The "MAOI-Safe" Anaesthetic Technique

When MAOIs cannot be stopped (e.g., emergency surgery):

Avoid meperidine and dextromethorphan
Avoid indirect vasopressors (ephedrine) - use direct-acting (phenylephrine, noradrenaline)
Avoid fentanyl + droperidol combinations
Ketamine is relatively contraindicated (sympathomimetic)
Regional anaesthesia preferred where feasible
TIVA with propofol + remifentanil is generally safe

3. TRICYCLIC ANTIDEPRESSANTS (TCAs)

Examples: Amitriptyline, Imipramine, Nortriptyline, Clomipramine

Mechanism

Block reuptake of noradrenaline and serotonin
Anticholinergic, antihistaminic, alpha-1 blocking effects
Sodium channel blockade at high doses

Continue perioperatively (abrupt discontinuation causes cholinergic rebound, relapse)

Anaesthetic Implications

Concern	Clinical implication
Prolonged QTc (sodium channel block)	Preoperative ECG mandatory
Augmented response to vasopressors	High doses + NE/adrenaline → severe hypertension/arrhythmias
Enhanced sedation	Potentiates barbiturates, opioids
Anticholinergic effects	Urinary retention, ileus, tachycardia; avoid atropine if possible
Lowered seizure threshold	Caution with enflurane, ketamine

Miller's Anesthesia, 10e, p. 4036-4037

Drug Interactions

Atropine: Additive anticholinergic - can cause severe tachycardia/confusion
Halothane: Risk of arrhythmias (TCAs sensitise myocardium to catecholamines)
Vasopressors: Exaggerated haemodynamic response with noradrenaline, adrenaline
MAOIs + TCAs: Serotonin syndrome

4. SSRIs / SNRIs

Examples: Fluoxetine, Sertraline, Citalopram, Escitalopram (SSRIs); Venlafaxine, Duloxetine (SNRIs)

General Rule: Continue perioperatively in most patients

Key Concerns

Bleeding risk:

Perioperative use of SSRIs is associated with increased surgical bleeding (platelet serotonin depletion)
Consider stopping 2 weeks before surgery with high bleeding risk (neurosurgery, cardiac surgery) after consulting psychiatrist
Miller's Anesthesia, 10e, p. 4037

Discontinuation syndrome (abrupt stopping):

Dizziness, chills, muscle aches, anxiety, sensory disturbances ("brain zaps"), depression relapse
Fluoxetine: long half-life (weeks), less withdrawal; Paroxetine: shortest half-life, worst withdrawal

Serotonin syndrome risk:

Combining SSRIs + MAOIs: absolutely contraindicated
Combining SSRIs + tramadol, linezolid, methylene blue, pethidine: risk of SS

QTc prolongation:

Citalopram and escitalopram have dose-dependent QTc prolongation - ECG recommended preoperatively at high doses

5. LITHIUM

Indication: Bipolar disorder (gold standard mood stabiliser)

Pharmacokinetics

Narrow therapeutic index: therapeutic range 0.6-1.2 mmol/L; toxicity >1.5 mmol/L
Renal excretion only (no hepatic metabolism)
Half-life: 24-37 hours

Perioperative Management

Minor surgery / local anaesthesia: Can continue lithium
Major surgery: Discontinue 72 hours before surgery (to allow 2 half-lives of clearance before potential renal compromise)
Restart: 24 hours postoperatively once renal function is established and oral intake resumed
Note: Abrupt discontinuation itself is associated with psychiatric relapse - so ensure planned restart

Drug Interactions (that precipitate lithium toxicity)

Drug class	Mechanism	Effect
Thiazide diuretics	Reduce renal Li clearance	Lithium toxicity (strongest effect)
Loop diuretics	Weaker effect on renal clearance	Mild toxicity risk
NSAIDs	Alter fluid balance, reduce Li excretion	Increase Li levels up to 40%
ACE inhibitors / ARBs	Reduce Li excretion + risk renal failure	Significant toxicity risk
Dehydration / fluid shifts	Reduced GFR → reduced Li excretion	Toxicity

Anaesthetic Implications of Lithium

Effect	Clinical significance
Prolongs NMJ blockade (both depolarising and non-depolarising)	Use nerve stimulator (train-of-four) monitoring
Blocks brainstem release of noradrenaline, epinephrine, dopamine	Reduced MAC requirements
ECG changes with toxicity	Sinus node dysfunction, AV block, T-wave changes, ventricular irritability
Nephrogenic diabetes insipidus (chronic use)	Fluid and electrolyte imbalance
Thyroid effects (chronic use)	Check TFTs preoperatively

Preoperative workup for lithium patients

Serum lithium level
Serum electrolytes and creatinine
TFTs (chronic use causes hypothyroidism in ~30%)
ECG
ATOTW 175; PMC8708655

6. ANTIPSYCHOTICS (Neuroleptics)

Classes

Generation	Examples	Mechanism
First-gen (typical)	Haloperidol, Chlorpromazine, Droperidol	D2 blockade predominantly
Second-gen (atypical)	Clozapine, Olanzapine, Risperidone, Quetiapine	D2 + 5-HT2A blockade

General Rule: Continue perioperatively

Abrupt withdrawal → acute psychosis relapse, postoperative confusion (already high in schizophrenia)

Anaesthetic Implications

Feature	Effect
Potentiate hypotensive effects of anaesthetics	Careful induction; reduced induction agent doses
Potentiate sedative effects	Enhanced CNS depression
Alpha-1 blockade (esp. chlorpromazine)	Hypotension; vasopressors required
Dopamine blockade on hypothalamus	Impaired thermoregulation - temperature monitoring essential
Reduced pain sensitivity (schizophrenia)	Patients may under-report postoperative pain
Increased risk of paralytic ileus	High incidence postop (sympathetic hyperactivity)
QTc prolongation (esp. haloperidol, ziprasidone, droperidol)	ECG required; avoid other QT-prolonging agents
Neuroleptic malignant syndrome (NMS) risk	Distinguish from malignant hyperthermia

Increased Cardiac Risk

Long-term antipsychotic patients have higher cardiovascular risk due to metabolic syndrome (weight gain, dyslipidaemia, hyperglycaemia) and high smoking rates
Full cardiac workup recommended for patients on long-term antipsychotics undergoing intermediate-high risk surgery

Neuroleptic Malignant Syndrome (NMS)

Rare but life-threatening complication of antipsychotic therapy:

Features: Hyperthermia, muscular rigidity ("lead pipe"), altered consciousness, autonomic instability, elevated CK
Triggers: Starting or increasing antipsychotic, withdrawal of dopaminergic agents
Anaesthetic concern: Can be confused with Malignant Hyperthermia (MH)
Distinction: NMS is slower onset (hours-days), responds to bromocriptine + dantrolene; MH is rapid (intraoperative), triggered by volatile agents/succinylcholine

Clozapine (special considerations)

Agranulocytosis risk - check WBC/ANC preoperatively
Strong anticholinergic and alpha-blocking effects
Lowers seizure threshold
Significant cardiac risk

7. BENZODIAZEPINES

Continue perioperatively (abrupt withdrawal → seizures, anxiety, autonomic instability)
Synergistic sedation with anaesthetic agents - reduce induction agent doses
Tolerance means standard anxiolytic doses may be inadequate
Avoid abrupt preoperative withdrawal; if discontinuation planned, taper gradually

8. OTHER MOOD STABILISERS (Anticonvulsants)

Drug	Perioperative advice	Key concern
Valproate	Continue	Inhibits CYP450; inhibits platelet function - check coagulation; hepatotoxicity
Carbamazepine	Continue	CYP induction - reduces efficacy of many drugs; can cause SIADH; monitor electrolytes
Lamotrigine	Continue	No major interactions
Oxcarbazepine	Continue	Hyponatraemia (SIADH)

9. ANAESTHESIA FOR ELECTROCONVULSIVE THERAPY (ECT)

ECT is the most common procedure requiring anaesthesia in psychiatric practice.

Physiological Effects of ECT-Induced Seizures

A therapeutic seizure lasts 30-60 seconds. Electrical stimuli are repeated until this is achieved; a good therapeutic effect requires 400-700 total seizure seconds.

Biphasic autonomic response:

Initial parasympathetic phase: Bradycardia (may be severe, <30 bpm or asystole), increased secretions
Sustained sympathetic phase: Hypertension, tachycardia (lasts several minutes), arrhythmias, T-wave changes

Other physiological effects:

Increased cerebral blood flow and ICP
Increased intragastric pressure (aspiration risk)
Increased intraocular pressure

Contraindications to ECT

Absolute (relative):

Recent MI (<3 months)
Recent stroke (<1 month)
Intracranial mass or aneurysm
Raised ICP

Relative:

Angina, poorly controlled CCF
Significant pulmonary disease
Bone fractures, severe osteoporosis
Pregnancy, glaucoma, retinal detachment

Why Anaesthesia is Necessary

Amnesia: for the period from NMB administration until after the seizure
Neuromuscular blockade: to prevent musculoskeletal injury from tonic-clonic convulsions
Airway management: mask ventilation required during paralysis
Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 1172

Anaesthetic Agent Selection for ECT

Goals:

Short-acting induction (amnesia needed for only 1-5 minutes)
Minimal anticonvulsant activity (to allow adequate seizure duration)
Rapid recovery

Agent	Dose	Comments
Methohexital (agent of choice)	0.5-1 mg/kg	Gold standard; may enhance seizure at small doses; rapid recovery
Propofol	1-1.5 mg/kg	Higher doses reduce seizure duration; good antiemetic profile
Thiopentone	1.5-2 mg/kg	Used historically; anticonvulsant properties
Etomidate	0.2-0.3 mg/kg	Prolongs recovery; increases seizure duration - useful for poor seizures
Ketamine	1-2 mg/kg	Increases seizure duration; NOT routinely used - hallucinations, delayed awakening, nausea
Esketamine	Lower dose	Emerging evidence; adjunct in refractory depression

Important: All induction agents raise the seizure threshold - use minimum effective doses. Benzodiazepines significantly raise seizure threshold and shorten seizure duration - avoid preoperatively for ECT.

Neuromuscular blockade:

Succinylcholine 0.25-0.5 mg/kg is standard (short duration; seizure activity easily monitored)
Mivacurium (short-acting non-depolariser) is an alternative if succinylcholine is contraindicated
Controlled mask ventilation with 100% O2 maintained throughout

Monitoring seizure duration:

"Cuff technique": inflate BP cuff above systolic on one limb before succinylcholine; observe isolated tonic-clonic activity in that limb
EEG monitoring (gold standard)

Cardiovascular management:

Glycopyrrolate or atropine IV before ECT to treat parasympathetic bradycardia
Short-acting beta-blockers (esmolol, labetalol) or nitroglycerine to control sympathetic hypertension/tachycardia
Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 1173

Recovery from ECT

Patient may be confused, disoriented for 10-30 minutes post-ictal
Monitor airway; lateral position until consciousness returns
Headache, muscle aches, nausea common
Progressive memory loss with multiple treatments (especially bilateral electrode placement)

10. PREOPERATIVE ASSESSMENT CHECKLIST

For any patient with a psychiatric disorder presenting for surgery:

Assessment	Why
Full drug history including psychotropic doses	Drug interactions, continuation vs. discontinuation decision
ECG	QTc prolongation (TCAs, antipsychotics, SSRIs), TCA-induced changes
Serum electrolytes + creatinine	Lithium, carbamazepine, valproate effects
Serum lithium level (if on lithium)	Narrow therapeutic window
TFTs (if on lithium or amiodarone)	Lithium causes hypothyroidism
FBC + coagulation (if on valproate/SSRIs)	Platelet dysfunction
Liver function (if on valproate)	Hepatotoxicity
WBC/ANC (if on clozapine)	Agranulocytosis
Blood glucose (if on atypical antipsychotics)	Metabolic syndrome
Consult psychiatrist before stopping any medication	Collaborative decision-making

11. SUMMARY TABLE: PERIOPERATIVE MEDICATION DECISIONS

Drug Class	Recommendation	Key Concern if Stopped	Key Concern if Continued
SSRIs/SNRIs	Continue (most cases)	Withdrawal syndrome, relapse	Bleeding risk, serotonin syndrome
TCAs	Continue	Cholinergic rebound, relapse	QTc, vasopressor interactions
Irreversible MAOIs	Continue + adapt plan OR stop 2-3 weeks before	Suicide risk, rebound depression	Serotonin syndrome with pethidine/tramadol; hypertensive crisis with indirect vasopressors
Reversible MAOIs (moclobemide)	Stop 24 h before	Minimal	As above but less severe
Lithium	Stop 72 h before major surgery	None (no withdrawal)	Prolonged NMJ block, toxicity, reduced MAC
Antipsychotics	Continue	Psychosis relapse, confusion	Hypotension, temperature dysregulation, NMS, QTc
Benzodiazepines	Continue	Seizures, withdrawal	Enhanced sedation
Valproate/Carbamazepine	Continue	Seizure risk, mood relapse	Platelet dysfunction (VPA), CYP induction (CBZ)

12. HIGH-YIELD EXAM POINTS

Pethidine + MAOI = absolute contraindication (serotonin syndrome; potentially fatal)
Indirect vasopressors (ephedrine) + MAOIs = hypertensive crisis - use phenylephrine/noradrenaline
Safe opioids with MAOIs: morphine, fentanyl (at low doses with monitoring), alfentanil, remifentanil; NOT tramadol, pethidine, methadone
Lithium: stop 72 h before major surgery; prolongs both depolarising and non-depolarising NMJ block; reduces MAC; narrow therapeutic index; check lithium levels, electrolytes, TFTs, ECG
ECT anaesthesia: methohexital is agent of choice; succinylcholine 0.25-0.5 mg/kg; avoid benzodiazepines preoperatively; atropine/glycopyrrolate to prevent bradycardia
Antipsychotics: impair thermoregulation (monitor temperature); reduce analgesic requirements; postoperative paralytic ileus; QTc prolongation
NMS vs MH: NMS - slow onset, antipsychotic-related, treat with bromocriptine + dantrolene; MH - rapid intraoperative, volatile agent/succinylcholine triggered, treat with dantrolene
SSRIs + surgery with high bleeding risk (neurosurgery): consider stopping 2 weeks before after psychiatric input
Methylene blue is a potent MAOI - serotonin syndrome with any serotonergic drug
Clozapine: check WBC before surgery (agranulocytosis); lowers seizure threshold

Sources: Miller's Anesthesia 10e (p. 4035-4037, 2896); Morgan & Mikhail's Clinical Anesthesiology 7e (p. 1172-1173); Barash Clinical Anesthesia 9e; ATOTW 175 (e-safe-anaesthesia.org); Anesthetic considerations for psychotropic drugs - PMC; UpToDate Perioperative Medication Management

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