Anesthetic Considerations in Electroconvulsive Therapy

Anatomy and Physiology

During ECT, a seizure is induced by an external electrical device while the patient is under general anesthesia. This results in a generalized tonic-clonic seizure with a duration that is variable. Seizures cause profound autonomic nervous system activity. First, the parasympathetic nervous system is activated, resulting in possible bradycardia and even asystole. The bradycardia is typically short-lived and followed by a sympathetic surge that causes hypertension and tachycardia. This sympathetic stimulation can last for anywhere from 5 to 10 min after the seizure has been induced.

The effect of a seizure causing a parasympathetic surge increases the risk of myocardial ischemia if the bradycardia is severe enough for too long. Glycopyrrolate, an anticholinergic medication, can be given to counteract the parasympathetic response such as increased salivation and bradycardia. Unfortunately, the administration of anticholinergic medications causes the opposite effect of producing tachycardia, which is exacerbated during the sympathetic response.

During the sympathetic discharge, prolonged tachycardia and hypertension increase the risk of cardiovascular events due to increased myocardial demand and oxygen consumption. Sympathetic stimulation and the seizure itself cause an increase in cerebral blood flow and an increase in cerebral metabolic rate of oxygen, resulting in increased intracranial pressure. Increases in intraocular and intragastric pressure occur as well. Esmolol can be used to blunt the sympathetic response.[3] Patients can also have postictal states with stroke-like symptoms or cognitive agitation, which can confuse the clinical picture as they are also recovering from general anesthesia at the same time.[4]

Indications

Providing general anesthesia for ECT is essential in every case and is only done without anesthesia in developing countries where proper equipment and personnel are not available. ECT is a first-line treatment for several disorders. When psychotic features and suicide risk are high, ECT is a useful initial treatment.  If a patient's depression has caused catatonia or psychomotor retardation involving the inability to eat or drink, then ECT is a viable treatment. It can provide fast relief if it is effective. One report indicates that for severe psychomotor depression, ECT provides up to 90% relief within two weeks.[5] Neuroleptic malignant syndrome is also an indication for ECT. Severe depression and psychotic features in pregnancy are conditions where ECT is used preferentially when medications can be harmful to the patient or the developing fetus.[6] 

ECT as a second-line treatment is mainly used when pharmacotherapy is ineffective or the patient's symptoms worsen.[7] In certain conditions, ECT is considered an experimental treatment with promising benefits such as treatment-resistant epilepsy, Parkinson disease, depression and tremors, and Tourette syndrome.[8][9][10]

Contraindications

There are several contraindications to ECT. Most contraindications are relative and need special consideration. The anesthesia provider must take into account each patient's comorbidities and address how a generalized seizure will affect them.  In most cases, pheochromocytoma and elevated intracranial pressure with mass effect at baseline are absolute contraindications.[11]  

An increase in intracranial or intraocular pressure is not tolerated very well for a patient with intracranial mass, retinal detachment, or intracerebral aneurysms. Patients with myocardial disease, cardiac arrhythmias, bleeding disorders, and pheochromocytoma may not tolerate the hemodynamic instability from extreme parasympathetic and sympathetic stimulation during the procedure.[12][13]

Equipment

There are several items needed before performing ECT. The American Society of Standard of care for monitoring a patient under general anesthesia includes monitoring heart rhythm with an electrocardiogram and monitoring heart rate, oxygenation, ventilation, and blood pressure. A tourniquet should be used on one of the patient's extremities to prevent the muscle relaxant from affecting that extremity, which allows monitoring of the effectiveness of the motor portion of the seizure.  Electroencephalogram (EEG) monitors, or processed EEG, monitor the status of the brain during the seizure. Emergency airway equipment should be readily available. A soft bite block is provided in the oropharynx to prevent tongue and tooth injury, as a generalized epileptic seizure has been shown to cause such trauma even in the setting of muscle relaxation.[14] A bag-valve mask and a simple oxygen face mask should be available to administer oxygen. A suctioning device is a necessity to help clear secretions.

Personnel

The personnel required for ECT are a psychiatrist, a nurse, and a trained anesthetic provider who can perform general anesthesia for the patient. These requirements vary by state and governing body.

Technique or Treatment

An intravenous catheter (IV)  is placed before the induction of anesthesia. Typically, a patient breathes 100% oxygen before induction of anesthesia. The patient's vital signs are monitored throughout the procedure. The intravenous anesthetic of choice is administered, followed by hyperventilation with a bag mask to induce hypocapnia which lowers cerebral blood flow and reduces the seizure threshold. After general anesthesia is successfully induced, a muscle relaxant is given to prevent myalgias and musculoskeletal injuries during the seizure. A tourniquet is commonly placed on one of the lower extremities to block muscle relaxants from reaching the area. This helps monitor the motor portion of the seizure by allowing personnel to observe the tonic and clonic activity of the lower extremity. A soft bite block is then placed to prevent the patient from developing an oral injury during the seizure.  The electrical stimulus is then administered to induce the seizure and is monitored by a processed EEG.

The goal is for the seizure to last around 25 to 75 seconds but no shorter than 15 seconds.[15][16] More prolonged seizures can be desirable if the patient has had ECTs that were less than 15 seconds in the past. The patient is then recovered in a post-anesthesia unit having their neurological status and hemodynamics monitored until it is appropriate for them to return home or to their assigned hospital room.

There are a variety of anesthetic agents and muscle relaxants that are used to induce anesthesia for ECT. Most dosing regimens for medications administered should be used in the lowest effective dose.

Methohexital is considered the gold standard for induction of anesthesia for ECT. It is a barbiturate that stimulates Gamma-aminobutyric acid (GABA) receptors which are the main inhibitory receptors in the brain. Methohexital produces anesthesia for approximately 4 to 7 minutes, which is ideal for ECT. It does not affect seizure threshold and, compared to propofol, does not shorten seizure length.[17] Methohexital causes moderate cardiac depression, which helps counteract the sympathetic discharge produced by a seizure. The initial dose is usually 1 to 1.5 mg/kg.[18] 

Etomidate is a unique drug that also works by activating GABA receptors in the brain. Studies have shown that it tends to produce a longer seizure compared to propofol.[19]  Etomidate does not cause cardiac depression, so the sympathetic discharge tends to be elevated when used as the sole anesthetic for ECT. Supplementing with an intravenous opioid such as remifentanil or a beta-blocker like esmolol to inhibit sympathetic discharge is common. Etomidate is known to cause adrenal suppression and should be avoided in patients with known adrenal insufficiency or critical illness. A dose of 0.3 mg/kg of etomidate is given to induce general anesthesia, lasting around 5 to 10 minutes.[20][21] 

Propofol also acts as a GABA agonist. However, it tends to shorten seizure duration as it increases the seizure threshold. It is used in ECT as an anesthetic agent when previous seizures induced by ECTs have been prolonged and when a rapid onset is needed. Propofol is dosed at 1.5 to 2 mg/kg.[22] 

Ketamine is N-methyl-D-aspartate (NMDA) antagonist, and it causes dissociative anesthesia as well as analgesia. It is not often used in ECT as it tends to increase seizure length and causes indirect myocardial stimulation. Ketamine also has antidepressant properties, and studies are ongoing determining its effectiveness as an adjunct for the treatment of depression. Doses of 1 to 2 mg/kg are typically used to induce adequate anesthesia.[23] Ketamine has the potential side effect of causing psychomimetic delirium during recovery, vivid dreams, and hallucinations. This is often pretreated with a benzodiazepine.[24][25] Recovery from ketamine is the slowest, followed by etomidate, methohexital, propofol when given for a short period.

Sevoflurane is an option for induction of anesthesia in ECT. It has a slow onset compared to intravenous anesthetics. It can be helpful to initiate anesthesia to obtain IV access on a patient who is uncooperative awake. When used for a short period, sevoflurane has a quick recovery. In a systematic review, sevoflurane reduces seizure length more prominently than propofol, barbiturates, and ketamine.[26] Sevoflurane does not attenuate the sympathetic stimulation to the extent as other induction agents, so opioids or beta-blockers are often used to maintain hemodynamic stability.[27] Sevoflurane enhances muscular blockade compared to intravenous anesthetics. 

Succinylcholine is the preferred muscle relaxant for ECT. It is a depolarizing neuromuscular blocker and is given in doses of 1 mg/kg to produce adequate muscle relaxation for intubating conditions within 30 seconds of administration. It typically lasts 5 to 8 minutes.[28] Succinylcholine raises the serum potassium by 0.5 meq/L after IV administration. In the setting of elevated plasma potassium and conditions that can cause an exaggerated increase in serum potassium when succinylcholine is given, lethal arrhythmias occur, and succinylcholine should be avoided.[29] There is no reversal agent for succinylcholine, but typically that is not needed since its duration of action is short. Succinylcholine and sevoflurane should be avoided if the patient has a history of malignant hyperthermia, as these are triggering agents for malignant hyperthermia.

Nondepolarizing neuromuscular blocking agents are good alternatives to succinylcholine, with the most common being rocuronium. Rocuronium is given at doses of 0.6 mg/kg to produce intubating conditions. Its effects last around 35 minutes. If the patient is on an antiepileptic medication or mood stabilizer such as lithium, the anesthetic provider must be aware. Lithium can delay the onset and prolong the actions of succinylcholine and nondepolarizing neuromuscular blocking agents.[30] Antiepileptic medications acutely can prolong the effects of nondepolarizing neuromuscular blocking agents, but when chronically taken, resistance to these muscle relaxants occurs, requiring larger doses.[31]

Complications

Complications in ECT, although rare, do occur. The anesthetic provider should be monitoring the patient at all times. The most common side effects of ECTs are headaches and cognitive impairment.[1] These tend to be temporary. The cognitive impairment is compounded by the administration of general anesthesia, the underlying psychiatric disorder, and the induced seizure. A seizure that lasts too long can result in status epilepticus. This condition requires prompt treatment in the form of administering benzodiazepine or propofol until termination of seizure. Status epilepticus is more common when pretreatment with theophylline is used to prolong the seizure.[32] 

Upon induction of general anesthesia and muscle relaxation, it may be difficult to mask ventilate the patient. Depending on which medications were used, letting the patient wake up and return to spontaneous ventilation may be the best option. Endotracheal intubation may be required to prevent severe hypoxia.

During recovery in the post-anesthesia care unit, myocardial infarction, ischemic or hemorrhagic stroke are possible. Evaluation by cardiology or neurology should be implemented if these conditions are noticed. Patients emerging from anesthesia may also become agitated and experience pain. Postictal side effects such as paralysis or mania are also possible.

Patients with deep brain stimulators or cardiac devices require special considerations. Deep brain stimulators can cause electrical interference when inducing a generalized seizure and should thus be turned off. A physician specialized in deep brain stimulation should be consulted.[33] Patients with pacemakers and other cardiac devices are primarily considered safe to undergo ECT with only ECG monitoring. There is a very low likelihood that the electrical impulse interferes with the cardiac device.[34] A magnet should be readily available in case of an emergency. The anesthetic provider should communicate with the patient's cardiologist to determine the severity of illness and risk of undergoing general anesthesia.

Clinical Significance

ECT is an effective treatment for pharmacotherapy-resistant depression and other severe psychiatric disorders. Its effects are quickly seen, but some patients may require multiple sessions of this therapy. Providing general anesthesia for ECT is standard and has been the case since the 1950s. Anesthesia for ECT provides a safe environment for a generalized epileptic seizure to take place.  Treatment of hemodynamic instability and prevention of painful and detrimental side effects are possible through a carefully planned anesthetic.

The ideal anesthetic agent provides amnesia with minimal effects on hemodynamic stability and seizure duration. An anesthetic agent that does affect seizure duration might be desirable if the patients' previous seizure during ECT was too long or short. Muscle relaxation protects the musculoskeletal system from the tonic and clonic actions of a generalized seizure. There are enough options and ways to provide anesthesia for ECT to suit most patients' needs. Alterations are made by the anesthesiologist, who recognizes reactions, patient discomfort, and side effects. Today, ECT is seldom performed without the use of general anesthesia except in developing countries. Musculoskeletal injury and post-traumatic stress disorder are not uncommon when enduring ECT without anesthesia.[35][36] Anesthesia prevents harm and trauma to the patient while enabling them to undergo a procedure that significantly improves their psychiatric disorder.

Enhancing Healthcare Team Outcomes

ECT provides patients with certain psychiatric disorders a treatment option for improvement in their mental state. Performing ECT requires an entire team composed of interprofessional colleagues, including anesthesiologists, psychiatrists, and nurses.[37][16] [Level 5]

Prior to undergoing ECT, a patient should be evaluated by an anesthetic provider to ensure the patient is safe to undergo general anesthesia and consent to the use of general anesthesia. Additionally, this allows the anesthetic provider to determine if the patient's comorbidities and current medication regimen require alterations to the anesthetic plan. The anesthesia team should also coordinate with the psychiatrist to determine the severity of the patient's psychiatric disorders and the length of seizure desired. A nurse is present before, during, and after the procedure to ensure the patient is ready for the procedure and monitored afterward. Nursing staff help to position the patient and to make sure all safety guidelines are followed. During recovery, nurses help recognize side effects and reactions to either the anesthesia or seizure.