What is the recommended dose and usage of thiopentone (barbiturate) as an anesthetic agent for electroconvulsive therapy (ECT)?

Thiopentone in ECT: Dosing and Usage

Thiopentone (thiopental sodium) is an acceptable alternative anesthetic agent for ECT at a standard dose of approximately 3-5 mg/kg IV, though methohexital remains the preferred first-line agent according to current guidelines. 1

Primary Anesthetic Selection for ECT

• Methohexital is the preferred anesthetic agent for ECT at a standard dose of 1.0 mg/kg IV, unless specific contraindications exist. 1

• Thiopental sodium (thiopentone) is listed as an acceptable alternative to methohexital, along with etomidate, ketamine, and propofol. 1, 2

Evidence Supporting Thiopentone Use

Seizure Quality and Duration

• Thiopentone demonstrates superior seizure characteristics compared to propofol, with significantly longer motor seizure duration (mean 40 seconds vs 21 seconds, P=0.018) and EEG seizure duration (mean 57 seconds vs 45 seconds, P=0.038). 3

• Patients anesthetized with thiopentone required lower electrical treatment doses (mean 459 mC) compared to propofol (807 mC) and etomidate (701 mC), while maintaining adequate seizure duration (P<0.001). 3

• Thiopentone produces longer seizure duration than propofol but with milder tonus and clonus during the seizure itself. 4

Hemodynamic Profile

• Thiopentone is associated with greater increases in systolic and diastolic blood pressure and heart rate post-treatment compared to propofol, which may be clinically relevant in patients with cardiovascular disease. 4

• The hemodynamic stimulation with thiopentone requires careful monitoring but can be managed with appropriate anticholinergic premedication. 2

Recovery Characteristics

• Recovery times (sitting up unaided, opening eyes on command) are similar between thiopentone and propofol. 4

• Propofol demonstrates superior early ambulation ability at 20 minutes post-procedure compared to thiopentone (P<0.0001). 4

• Thiopentone causes significantly less pain on injection (1.6% of cases) compared to propofol (51.6% of cases). 4

Complete ECT Anesthetic Protocol

Mandatory Components

• Muscle relaxant: Succinylcholine 0.9 mg/kg IV is the standard agent, with atracurium and mivacurium as alternatives. 1, 2

• Anticholinergic medication: Atropine or glycopyrrolate must be administered immediately before ECT to prevent bradycardia, arrhythmia, or cardiac asystole. 1, 2

• Ventilation: 100% oxygen ventilation before electrical stimulus is mandatory. 1, 2

Critical Timing for Anticholinergics

• Anticholinergic premedication is required before seizure threshold determination and before the first treatment with right unilateral electrode placement. 2

• This prevents vagally-induced cardiac complications from the electrical stimulus. 2

Clinical Decision Algorithm

When to Choose Thiopentone:

1. First consideration: If methohexital is unavailable or contraindicated. 1

2. Inadequate seizure duration: When patients demonstrate insufficient seizure duration with propofol, thiopentone should be considered as it requires lower electrical doses while maintaining adequate seizure duration. 3

3. Pain on injection concerns: Thiopentone causes significantly less injection pain than propofol. 4

When to Avoid Thiopentone:

1. Cardiovascular instability: The greater hemodynamic stimulation may be problematic in patients with uncontrolled hypertension or cardiac disease. 4

2. Rapid ambulation required: If immediate post-procedure mobility is prioritized, propofol demonstrates superior early ambulation. 4

3. Availability: Thiopentone may have limited availability in some regions compared to more commonly stocked agents. 3

Comparative Performance with Other Agents

• Etomidate produces longer seizure durations than methohexital and may be preferred when seizure adequacy is a primary concern. 1, 5

• Etomidate demonstrates motor seizure duration of 35.92 seconds (±9.2) versus thiopentone's 26.69 seconds (±9.7), though this difference was significant (P<0.007). 5

• Propofol shortens seizure duration and may affect ECT efficacy, making it less ideal when seizure quality is suboptimal. 6, 7

Critical Pitfalls to Avoid

• Never omit anticholinergic premedication during seizure threshold determination or first unilateral treatment, as this leaves patients vulnerable to severe bradycardia or asystole. 2

• Do not use thiopentone as monotherapy without appropriate muscle relaxation (succinylcholine) and anticholinergic coverage. 1, 2

• Avoid rapid injection of low doses - unlike propofol which requires rapid injection at low doses, thiopentone dosing should follow standard induction practices. 7

• Monitor for prolonged apnea, though this is more common with propofol than thiopentone. 4

Medications to Discontinue Before ECT

• Lithium should be discontinued when clinically possible due to risk of acute brain syndrome. 2, 8

• Benzodiazepines increase seizure threshold and should be discontinued. 2, 8

• Carbamazepine may cause failure to induce seizures and should be stopped. 2, 8

• Trazodone is associated with prolonged seizures and requires discontinuation. 2, 8