How to dose ECT?

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Brief guide about dosing electrical stimulus of ECT

Brief guide about dosing electrical stimulus of ECT

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  • 1. Dosing ECT Stimulus Ahmad al-Ajhuri, MBChB MScMed Emory University ECT mini-fellowship Director of ATP
  • 2. Related Electricity principles• V=I×R “Ohm’s Law”V: voltage in volts, I: current intensity in milliamperes, R: resistance (impedance) in ohms• U=Q×I×RU: energy in joules, Q: charge in millicoulombs, I: current intensity in milliamperes, R: resistance (impedance) in ohms• Q = I × PW × 2F × DQ: charge in millicoulombs, I: current intensity in milliamperes, PW: pulse width, F: frequency in hertz (cycles pairs per second), D: duration of stimulus train in seconds• 1 mC = 1 mA / 1 sec• Constant current devices: safe• Summary metric: J / mC?• Energy (J): unpredictable Ohm’s law triangleatpbox@gmail.com Cairo, May 2011 2
  • 3. Electrical waveforms of ECT• Waveform: the “shape” of the stimulus as a function of time.• Sine wave ECT: 1930s Cerletti and Bini, wall outlets, continuous, neurotoxic!• Brief pulse ECT: 0.5 – 2 ms, late 1970s• Ultra-brief pulse ECT: < 0.5 ms, late 1990satpbox@gmail.com Cairo, May 2011 3
  • 4. Sine Vs Pulse squared waveatpbox@gmail.com Cairo, May 2011 4
  • 5. Seizure Threshold (ST)• The total amount of electricity necessary to induce a seizure ie CONVULSIVE THRESHOLD.• IMPEDANCE: static (200 – 3000 Ω) and dynamic (120 – 350 Ω). Electrodes, scalp and skull.• IMPEDANCE: automatic self-test in MECTA devices Females > Males RUL > BT > BF• Scalp SHUNTING of current: a lower proportion of current entering the brain. It is a short-circuitatpbox@gmail.com Cairo, May 2011 5
  • 6. Cause of variations in impedanceatpbox@gmail.com Cairo, May 2011 6
  • 7. ST• ST variance: up to 50 folds, a lot of factors, strong evidence for gender and electrode placement• Titration session : up to 4-5 restimualtions with 20 seconds apart• STIMULUS INTENSITY: moderately suprathreshold ie 1.5 – 2.5 × ST in BT/BF, 2.5 – 6 × ST in RULatpbox@gmail.com Cairo, May 2011 7
  • 8. Factors influencing STatpbox@gmail.com Cairo, May 2011 8
  • 9. Psychotropics during ECTatpbox@gmail.com Cairo, May 2011 9
  • 10. Is seizure duration enough?atpbox@gmail.com Cairo, May 2011 10
  • 11. STIMULUS DOSING• Why? – Cerebral generalization: more effective – Barely suprathreshold (just above ST): ineffective – Markedly suprathreshold (far beyond ST): hazardous – ST is increasing along index ECT course: fixed dosing is inappropriate• EMPERICAL TITRATION: most precise• PRE SELECTED (FORMULA-BASED) METHOD: pts do not tolerate titration, eg cardiac, severely suicidal. etc• FIXED DOSING: may be a malpractice, esp if randomly assigned.atpbox@gmail.com Cairo, May 2011 11
  • 12. STIMULUS DOSING: MECTA devices• Stimulus 1: RUL, Female• Stimulus 2: BT/BF Female, RUL Male• Stimulus 3: BT/BF Male• After 3rd failed stimulus (uncommon): jump 2 levels for 4th one• Preselected stimulus: calculated dose Stimulus 3: RUL, Female Stimulus 4: All others• Dial the device knob: 1 / 2 – 1 × pt age ( poor method with no evidence)atpbox@gmail.com Cairo, May 2011 12
  • 13. STIMULUS DOSING: MECTA devices• Remember : therapeutic STIMULUS INTENSITY is moderately suprathreshold for next sessions: 1.5 – 2.5 × ST in BT/BF, 2.5 – 6 × ST in RUL• General rule: restimulate increasing 50 – 100 % of the previous stimulus when needed, eg missed seizure, brief seizure, etcatpbox@gmail.com Cairo, May 2011 13
  • 14. SEIZURE ADEQUACY• Pattern & Duration: motor & EEG• Pattern: generalization both motor & EEG• Duration: 20 – 60 sec motor, 30 – 120 sec EEG• MISSED: no activity both motor & EEG• BRIEF (ABORTIVE): < 20 sec motor, < 30 sec EEG• PROLONGED: > 60 sec motor, > 120 EEG• Post-ictal suppression: a valid parameter• Although: seizure adequacy parameters are still unclear, and lacking good evidenceatpbox@gmail.com Cairo, May 2011 14
  • 15. Seizure durationatpbox@gmail.com Cairo, May 2011 15
  • 16. How to manage inadequate seizure?• MISSED / ABORTIVE: – Check device and connections – Restimulate: 20 sec apart, up to 5 times ( very rare), vary the duration and frequency, then pulse width – Hyperventilate: 15 – 20 / min – IV Flumazenil: if pt is on BZD – DC / Taper drugs interfering: eg AEDs – Decrease IV anesthetic dose / switch to less anticonvulsant one. Consider xanthines: Caffeine, theophylline, aminophylline. – Space the schedule – Check recent stimulus increase: paradoxical area of curveatpbox@gmail.com Cairo, May 2011 16
  • 17. PROLONGED / TARDIVE seizures• More than 60 sec motor / 120 sec EEG (APA Task Reprot 2001: 180 sec both !) – Abort with IV anesthetic (thiopental) / BZD (midazolam). If no response (rare): intubate, IV loading phenytoin and refer to ICU. – Good ventilation – Additional dose of muscle relaxant – Decrease stimulus – Check pt drugs: eg xanthinesatpbox@gmail.com Cairo, May 2011 17
  • 18. ECT seizure vs Epileptic seizureatpbox@gmail.com Cairo, May 2011 18
  • 19. Electrode placement BT RUL BF d’Elia Letemendiaatpbox@gmail.com Cairo, May 2011 19
  • 20. Factors may increase cognitive side effectsatpbox@gmail.com Cairo, May 2011 20
  • 21. atpbox@gmail.com Cairo, May 2011 21
  • 22. atpbox@gmail.com Cairo, May 2011 22
  • 23. Non standardized constant voltage ECT deviceatpbox@gmail.com Cairo, May 2011 23
  • 24. A flower from Abbassia GardensATP Building at Abbassia atpbox@gmail.com Cairo, May 2011 24