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Vol. 15. Issue 2.
Pages 151-153 (April - June 2022)
Vol. 15. Issue 2.
Pages 151-153 (April - June 2022)
Letter to the Editor
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Improving the effectiveness of electroconvulsive therapy through the determination of anaesthetic depth. Preliminary results
Mejora de la efectividad de la terapia electroconvulsiva mediante la determinación de la profundidad anestésica. Resultados preliminares
Òscar Alcoverro-Fortunya,b,
Corresponding author
, Ferran Viñas Usana, Carmen Elena Sanabriac, José Emilio Rojo Rodesb,d
a Unidad Hospitalización Breve Psiquiatría, Benito Menni - H. General Granollers, Granollers, Barcelona, Spain
b Doctorado en Ciencias de la Salud, Departamento de Medicina, Universidad Internacional de Catalunya, Barcelona, Spain
c Departamento Anestesiología y Reanimación, H. General Granollers, Granollers, Barcelona, Spain
d CASM-Benito Menni, Sant Boi de Llobregat, Barcelona, Spain
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Dear Editor,

The anaesthetic agents such as propofol used in modified ECT may hinder an optimum convulsion1, thereby reducing its antidepressant effect and increasing the secondary cognitive effects because the stimulus energy has to be increased1. The PSI (Patient State Index) was specifically designed to control patient sedation and the effect of drugs in intraoperative interventions and intensive cures2, predicting loss of consciousness and detecting intraoperative waking3. Use of this index has made it possible to reduce the dose of propofol used in anaesthesia, improving recovery time without increasing intraoperative recall4. The first results are presented of an experimental prospective study with a control group, to determine the impact in terms of efficacy and safety of using the ECT procedure while monitoring the depth of anaesthesia using the PSI, in comparison with the traditional clinical method.

The sample is composed of 31 patients admitted to the BM-CASM-HGG Psychiatric Unit. They were recruited from November 2017 to September 2020 and fulfilled the criteria for major depressive disorder according to the DSM-IV-TR and the indication for ECT.

This study fulfils the conditions of the Helsinki Declaration, and it was approved by the Clinical Research Ethics Committee of Granollers H. General. The patients voluntarily accepted taking part, giving their informed consent. 2 sessions per week with propofol and succinylcholine took place, using Thymatron SYSTEM IV apparatus (Somatics LLC, U.S.A.), and determining the PSI with a SedLine® monitor (Masimo Corporation, U.S.A.). The stimulus dose was calculated using the “age-based method”5 and using a pulse width of 0.5ms. for bifrontotemporal ECT and 0.25ms. for the unilateral right side. Patients in the PSI group were stimulated when its value showed a tendency to rise between the values of 50–70, and those in the control group were stimulated when the score was 5–6 on the Ramsay scale6 and the fasciculations caused by the succinylcholine had ended. Patients were re-stimulated if the convulsion lasted for less than 25s in the EEG. The appropriateness of the convulsion was evaluated in each session according to a method similar to that used by Rattehalli7, together with the presence of delirium and waking intra-ECT8; likewise clinical state using HDRS-17 and CGI in alternating sessions and cognitive state with the MCE. The patients finalized the study when they achieved clinical remission or if after 12 sessions this was not possible, and if with a stimulus of 100% energy a convulsion of at least 25s was not achieved.

The SPSS program (version 23, IBM Corp., NY, U.S.A) was used for statistical analysis; the Mann-Whitney U test was used for quantitative variables and the χ2 test was used for qualitative variables. Statistical significance was considered to exist if P.05.

No statistically significant differences were found between the clinical and sociodemographic characteristics of both groups. The average PSI value was 56.71±6.81.

The PSI group obtained longer and higher quality convulsions with less energy, and required fewer repeat stimulations (Table 1). Unlike other studies9, the number of sessions was neither lower nor statistically significant in the PSI group, probably because of the small size of the sample. The use of repeat stimulations and higher stimulation energies have been associated with adverse cognitive effects10, and although we did not find this, it is possible that more sensitive tests than the MCE would be required11.

Table 1.

Results in terms of efficacy and safety.

  PSI-TEC  TEC  Statistical analysis
      Test  p 
No. of sessions, average (SD)  6.64 (3.71)  6.59 (3.64)  Mann-Whitney U test=115  0.87 
Repeat stimulation, n (%)  5 (2.7)  43 (19.2)  χ2=26.61 gl=<0.001 
No convulsion with E=100%, n (%)  3 (17.6)  Fisher’s exact test  0.23 
Dose of propofol mg/session, average (SD)  77.6 (22.9)  70.1 (21.6)  Mann-Whitney U test=4225.5  0.019 
Dose of propofol mg/kg, average (SD)  1.2 (0.39)  1.1 (0.34)  Mann-Whitney U test=4195.5  0.017 
Stimulus energy Mc, average (SD)  232.16 (126.6)  258.05 (107.6)  Mann-Whitney U test=5828  0.022 
Convulsion duration EEG in sec., average (SD)  39.95 (14.2)  34.6 (20.8)  Mann-Whitney U test=5374  0.001 
Suitable convulsion, n (%)  71 (75.5)  60 (39)  χ2=31.33 gl=<0.001 
Waking time in sec., average (SD)  473.1 (179.4)  558.11 (225.22)  Mann-Whitney U test=3505.5  0.004 
Delirium (CAM), n (%)  1 (1.2)  2 (1.8)  Fisher’s exact test 
Intra-ECT waking, n (%)  3 (3.2)  Fisher’s exact test  0.25 
HDRS-17 final, average (SD)  8.29 (4.91)  8.88 (5.58)  Mann-Whitney U test=102.5  0.51 
CGI final ≤4, n (%)  12 (46.2)  14 (53.8)  Fisher’s exact test 
GAF final, average (SD)  64.36 (9.25)  62.88 (11.28)  Mann-Whitney U test=108.5  0.88 
Final MCE, average (SD)  29.77 (5.54)  29.35 (4.73)  Mann-Whitney U test=97.5  0.58 

CAM: Confusion Assessment Method; CGI: Clinical Global Impression; EEG: electroencephalogram; GAF: Global Assessment of Functioning; HDRS-17, Hamilton Depression Rating Scale-17; MCE: Mini Cognitive Exam.

The waiting time until the ideal PSI value was reached may explain reduced action of the anaesthesia at the instant of stimulation, as other studies have shown12, and that in this group effectiveness improved in spite of the patients receiving a higher dose of propofol. The higher dose may be due to occasional supplementation to optimize sedation during the said waiting time.

Using the PSI maintains the efficacy of the procedure, as it achieves a level of remission comparable to the group treated traditionally.

No patient in the PSI group mentioned intra-ECT recall, although the possible presence of anterograde amnesia at the moment of evaluation may have influenced this.

The size of the sample, the lack of double blind and non-standardization of PSI values in a psychiatric population are limitations that should be taken into account.

We believe this to be the first study in which the PSI is applied in ECT, and it may be concluded that it is a suitable means of determining when to apply the stimulus. It improves the efficacy of the latter, giving better convulsions with less stimulus energy and fewer repeat stimulations). It does not affect safety, without any greater cognitive affect or increased intra-ECT awareness, although this requires confirmation in larger samples.


This work was financed by the Prize for the best research project in the “IV Jornada de Recerca i Innovació de la Fundació Privada Hospital Asil de Granollers”.

Conflict of interests

The authors have no conflict of interests to declare.

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Please cite this article as: Alcoverro-Fortuny Ò, Viñas Usan F, Elena Sanabria C, Rojo Rodes JE. Mejora de la efectividad de la terapia electroconvulsiva mediante la determinación de la profundidad anestésica. Resultados preliminares. Rev Psiquiatr Salud Ment (Barc). 2022;15:151–153.

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