Abstract
Electroconvulsive therapy (ECT) has been shown to be an effective and safe nonpharmacological treatment modality for a variety of severe neuropsychiatric disorders. Today, it is in worldwide use in both inpatient and outpatient settings. While ECT was originally performed without sedation or anesthesia, nowadays a “modified technique” is most often used with intravenous anesthesia, neuromuscular blockade, and mechanical ventilation providing more safety and less patient’s subjective unpleasantness along with reduced adverse side effects. To minimize risks, ECT requires close interdepartmental cooperation between psychiatrists and anesthetists. In the preanesthesia evaluation of ECT, a thorough history and physical examination are obligatory and the patient’s medical condition should be optimized. Anesthesia should be provided by an anesthetist familiar with both the effects of the anesthetic drugs on the ECT response and the physiologic alterations that may occur during the procedure as well as their specific treatment.
Keywords
Electroconvulsive therapy, Intravenous anesthesia, Muscle relaxant, Safety, Side effects
Background
Electroconvulsive therapy (ECT) inducing a generalized tonic-clonic epileptic seizure is established as an effective and safe treatment option for severe psychiatric disorders. Today, ECT is in worldwide use in both inpatient and outpatient settings. The main indications for ECT are unipolar major depression as well as manic episodes mostly not responding to psychopharmacological therapies. , Further indications include some other forms of psychiatric illness such as schizophrenic disorders, catatonia, suicidality, and neuroleptic malignant syndrome. , ECT can be combined with other treatment modalities. Since its introduction in 1938 by Italian scientists, there have been some changes in the administration of ECT to patients. While ECT was originally performed without sedation or anesthesia, a “modified technique” is presently most often used with general anesthesia, neuromuscular blockade, and mechanical ventilation providing more safety and patient comfort along with fewer procedure-associated adverse events. Currently, severe complications occur in less than 1 in 10,000 treatments, which require specific therapy. The mortality rate is very low and varies between 1:50,000 and 1:25,000 treatments, and is therewith comparable to the anesthetic-related mortality associated with minor procedures involving general anesthesia. These treatment-related cases of death are mostly caused by cardiovascular and, to a lesser extent, pulmonary complications. Although the safety and practice of ECT has improved for over 70 years, the underlying mechanisms responsible for the therapeutic effectiveness in psychiatric disorders are still under investigation and not yet clear to date. , Despite proven success, ECT remains the most pilloried treatment in psychiatry.
Technique of Electroconvulsive Therapy
To induce a generalized seizure that constitutes the therapeutic agent of ECT, an electrical current is applied to the brain via two surface electrodes. These are typically positioned either unilaterally or bilaterally on the scalp. The latter, also known as bitemporal or bifrontotemporal, is used today particularly in urgent clinical situations when the speed of clinical response is most important. Unilateral stimulation performed on the nondominant hemisphere avoids stimulation of the hemisphere responsible for language function and minimizes cognitive adverse effects and is therefore at present the preferred technique used for the majority of treatments. Modifications in electrode placement as well as energies and waveforms of the electrical current affect the seizure quality, which is crucial for treatment success. To date, the most accepted criteria for adequate seizure are at least 20 s of tonic-clonic movement or 25 s of electroencephalographic (EEG) seizure activity; seizures lasting less than 15 s are generally considered to be ineffective, and prolonged seizures may be associated with increased cognitive impairment. Seizure characteristics are monitored by an EEG on the ECT device.
Patients chosen for ECT most often need multiple treatments. ECT is usually administered up to two to three times a week until there is no further improvement. Most patients remit with a total of 6–12 treatments, but some patients require considerably more treatments. To prevent a relapse of the mood or psychotic episode that prompted the acute course of ECT, therapy may be continued with single ECT at an interval of 1–8 weeks during the first 6 months after remission. Thereafter, maintenance ECT may be a treatment option for patients who recovered from the acute episode and need prevention of a new episode.
Contraindications
There are no absolute medical contraindications to ECT in adults. Relative contraindications include untreated cerebral aneurysms, recent intracerebral hemorrhage, space-occupying cerebral lesions, cardiac failure, recent myocardial infarction, pheochromocytoma, retinal detachment, or glaucoma. In these situations, the risk–benefit ratio for the patients and their specific compromised clinical situation has to be calculated. If after this decision ECT remains the treatment of choice, appropriate precautions have to be performed to minimize the patient’s risk.
Preprocedure Management
Prior to elective ECT, written informed consent for anesthesia must be obtained from the patient or his responsible legal representative as for every anesthesia for diagnostic or surgical procedures. In cases of a life-threatening situation in which there is no possibility to obtain informed consent from the patient, ECT can also be administered after legal authorization and obtaining the informed consent of the patients’ legal representatives.
Pre-ECT medical evaluation is identical to the approach of a patient undergoing any procedure requiring general anesthesia. The evaluation should identify coexisting medical illnesses and evaluate their potential interaction with and impact on ECT treatment. In this respect, a thorough history and focused physical examination is required. Further investigations like electrocardiograms, chest radiographs, and blood tests should be performed as clinically indicated.
The majority of patients scheduled for ECT receive a variety of psychiatric drugs such as antidepressants, anticonvulsants, mood stabilizers, antipsychotics, anxiolytic drugs, or central nervous system stimulants with possible side effects. , Between these drugs and drugs used for anesthesia, pharmacodynamic or pharmacokinetic interactions may occur, and their characteristics may vary between subtle and significant. , For example, lithium may be associated with postprocedural delirium and may prolong the effects of succinylcholine. In close cooperation between anesthetists and psychiatrists it has to be clarified if the psychiatric medication should be modified or withhold prior to ECT. In most cases, patients should take their regular medications without tapering until the morning of the procedure. Although life-threatening drug interactions are rare, awareness of detection and adequate treatment is highly required.
Usually, patients will receive no premedication since most of the drugs used for this purpose interfere with seizure generation and may delay emergence.
Current fasting [nil per os (NPO)] guidelines for the procedure are 6 h for a meal and 2 h for clear liquids. Since patients often do not comprehend the need for withholding food and drink, NPO status must be checked prior to the procedure.
Anesthesia for Electroconvulsive Therapy
Today, in most countries general anesthesia, muscle relaxation, and mechanical ventilation is the standard of care for ECT. Anesthesia is used to avoid horrible feelings that awake patients may have during convulsion inducement. It also blocks the sensation of general paralysis caused by neuromuscular blocking agents (NMBAs), which reduce the risk of musculoskeletal injuries. Since only a short anesthesia is required for ECT, the ideal drugs used in this scenario should provide a rapid onset and offset of unconsciousness and muscle relaxation.
Induction Agents
Several intravenous anesthetics such as methohexital, thiopental, propofol, etomidate, and ketamine have been used with or without a short-acting opioid for the administration of ECT ( Table 48.1 ). , Their impact on ECT-induced seizure duration is of utmost importance, since seizure duration is crucial for the effectiveness of the treatment. EEG seizure activity lasting 25–60 s is assumed to be optimal. Seizure duration of less than 15 s and more than 120 s are less favorable. Ideally, the induction agent should have no or minimal effects on seizure duration, a rapid onset, and brief duration of action and minimal side effects. In fact, the intravenous anesthetic itself as well as its dosage may, however, influence the duration of seizure induced by the electrical stimulus because of a possible inherent anticonvulsive effect. In addition, it is questionable if a fixed dose for induction of anesthesia will result in an identical depth of anesthesia among all patients. Furthermore, a relatively high dose chosen may shorten seizure duration; otherwise, a relatively small dose chosen may result in insufficient depth of anesthesia or awareness. Therefore, a subtle equilibration is important to achieve an adequate depth of anesthesia as well as an optimal duration of seizure activity in every individual patient.
| Anesthetic Agent | Dosage |
|---|---|
| Methohexital | 0.5–1.5 mg/kg |
| Thiopental | 2–3 mg/kg |
| Propofol | 0.75–2.5 mg/kg |
| Etomidate | 0.15–0.3 mg/kg |
| Ketamine | 0.7–2.8 mg/kg |
| Sevoflurane | 6–8% inspired for induction, thereafter 1–2 MAC |
There are a lot of studies comparing the use of various anesthetics for ECT. Since most often different doses of the anesthetics were used, it is quite difficult or impossible to compare the results with respect to seizure quality, time to emergence, and adverse effects. This has to be kept in mind when interpreting the results of a Cochrane review including 18 randomized controlled studies dealing with the efficacy and safety of different regimes of sedatives and hypnotics for anesthesia of ECT. As implications for practice it was reported that: (1) propofol seemed to reduce EEG and motor seizure duration compared with methohexital and possibly with etomidate; (2) propofol was comparable with thiopental regarding EEG seizure duration; (3) motor seizure duration was longer with methohexital than with propofol; and (4) recovery times were shorter with propofol than with thiopental. Based on these results it was concluded that methohexital or etomidate may be superior to propofol and thiopental if there is a problem in eliciting an adequate seizure and that propofol might be preferred to thiopental if emergence from anesthesia is slow.
Since ketamine is less anticonvulsant than other anesthetics, it may prolong or enhance ECT seizures. However, ketamine should be used cautiously in patients with cardiovascular comorbidities because there may be a more pronounced elevation of the patients’ blood pressure. Furthermore, the use of ketamine may result in a higher rate of unwanted side effects such as disorientation, restlessness, delirium, or psychosis.
Coadjuvant opioids, especially the short-acting remifentanil, can enhance seizure quality, probably allowing a reduced dosage of the intravenous anesthetics, as the latter are known to have anticonvulsant effects. , Thereby, remifentanil itself seems to have no intrinsic properties that enhance ECT seizures.
Reports of the use of volatile anesthetics for ECT are rare, and aside from patients with poor peripheral veins in whom placement of intravenous access may be difficult, there are almost no advantages when compared with intravenous anesthetics usually used for ECT.
Currently, the bispectral index is widely used to monitor the level of consciousness of patients receiving general anesthesia, and there have been attempts to correlate this value to the duration of and recovery from an ECT-induced seizure. While several reports have described the value as unreliable for this purpose, its use may be beneficial to determine the induction dose of anesthetics for unconsciousness before electrical stimulation.
Neuromuscular Blocking Agents
Performing ECT treatments without muscle relaxation can cause bone fractures and dislocations, thus the use of NMBAs is recommended ( Table 48.2 ). The aims of their use are reduction of motor activity to avoid injuries, minimal interference with seizure activity, and prompt recovery of spontaneous ventilation without residual paralysis. In this context, succinylcholine is still the muscle relaxant most frequently used, despite its well-known adverse side effects like hyperkalemia and malignant hyperthermia. When succinylcholine is contraindicated, a nondepolarizing NMBA has to be used. It should be noted that the action of these NMBAs takes longer than the time normally required for an ECT treatment even when intermediate-acting NMBAs are used. Therefore, monitoring and reversal of neuromuscular blockade is strongly recommended. Today, the combination of rocuronium and sugammadex may be an alternative to succinylcholine since several reports demonstrated that sugammadex produced a complete and rapid reversal of neuromuscular blockade induced without other safety concerns.
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