Anaesthesia for ECT
A 55 year-old patient is due to have electro-convulsive therapy (ECT) for severe depression.
a) What are the specific pre-operative considerations for ECT? (5 marks)
b) What are the physiological effects of ECT (7 marks) and which physical injuries may occur during
treatment? (3 marks)
c) The patient is taking lithium and fluoxetine. What are the anaesthetic implications of these agents
during ECT? (5 marks)
Click for model answer by Dr Gareth Paul
- A 55 year-old patient is due to have electro-convulsive therapy (ECT) for severe depression.
What are the specific pre-operative considerations for ECT? (5 marks)
Standard Preoperative history, examination and relevant investigations focusing on;
Cardiac disease specifically coronary heart disease and recent history of myocardial infarction, uncontrolled heart failure, hypertension, arrhythmias, valvular disease or previous deep vein thrombosis. Presence of an ICD or PPM.
Recent Cerebral Vascular Accident or intracranial pathology vulnerable to changes in intracranial pressure such as tumours or unprotected aneurysms.
Recent fracture or history of osteoporosis.
History of retinal detachment or glaucoma.
Gastro oesophageal reflux or hiatus hernia.
Drug history particularly psychotropic medication and allergies.
Previous Anaesthetic complications focusing on Malignant Hyperpyrexia or Succinylcholine Apnoea.
Focused examination concentrating on the above pathologies.
Airway assessment and examination of dentition.
Blood tests, ECGs, ECHOs, PFTs as clinically indicated.
What are the physiological effects of ECT (7 marks) and which physical injuries may occur during treatment? (3 marks)
Automonic nervous system activation.
Initially parasympathetic activation with risks of bradycardia, hypotension and asystole.
Prominent sympathetic response follows onset of seizure activity, systolic pressure may increase by 30-40% and an increase in heart rate of 20% or more.
Increased myocardial oxygen consumption as a result of this.
Hypertension can persist post procedure.
Potential for arrhythmias.
Increased cerebral blood flow and intracranial pressure during induced seizure.
Increased cerebral oxygen consumption.
Risks of cerebral ischaemia and haemorrhage.
Increase in intraocular pressure.
Pulmonary oedema is rare but occurs.
Results from either negative pressure from inadequate recovery from neuromuscular blockade and attempted inhalation against a closed glottis.
Potentially neurogenic in origin as a result of the sympathetic surge after onset of seizure.
Increased intragastic pressure.
Increase in ACTH, Adrenaline, Cortisol, Vasopressin, Prolacin and Growth Hormone.
Increased release of Creatinine Kinase.
Oral cavity or tongue lacerations.
Temporomandibular Joint damage.
The patient is taking lithium and fluoxetine. What are the anaesthetic implications of these agents during ECT? (5 marks)
Prolongs NDMR blockade if used.
Lowers the seizure threshold so may prolong ECT induced seizure requiring intervention.
Reduces Anaesthetic requirement.
If levels are supratherapeutic, arrhythmias are more common.
Can induce hypothyroidism with thyroid enlargement potentially causing obstructive symptoms.
Fluoxetine - SSRIs;
In combination with seratonergic drugs, Sertonin Syndome could be provoked.
Increased risk of bleeding if patient also takes NSAIDs or Warfarin, relevant if there is an intraoral injury.
Magnetic resonance imaging - anaesthetic hazards
(a) Briefly describe the physics of magnetic resonance imaging (20%)
(b) What are the indications for MRI? (20%)
(c) What groups of patients might the anaesthetist be asked to provide general anaesthesia for? (20%)
(d) What are the hazards in MRI unit for patients and staff? How may these be prevented? (20%)
(e) Describe the anaesthetic management of a general anaesthetic in the MRI unit. (20%)
Click for model answer by Dr Anna Laird
- Atoms with an odd unpaired proton such as hydrogen atoms are abundant in the body and each have their own magnetic field causing them to spin.
- The MRI is a large magnet that emits a static elecrotromagnetic field commonly 1.5-3 telsa. It causes these nuclei to align themselves with the field.
- Other smaller electromagnetic fields are created and are switched on and off and cause the molecules to switch alignment by absorption of the energy.
- When magnetic field is turned off they fall back to their original position and release energy which is detected by a receiving coil in the scanner and converted to an image.
- Different tissues return to equilibrium at different rates and that how image is created.
Imaging of soft tissue:
Especially central nervous, musculoskeletal, cardiovascular systems, pelvis and liver.
Patients with severe movement disorders
Patients whose position is limited by pain
Ventilated and other ITU patients
Certain patients undergoing stereotactic neurosurgical procedures
Patients having surgery with intraoperative MRI
- Remote anaesthesia - ensure emergency equipment, trained staff
- Metal dislodgement - make sure checks made to ensure no ferrous material
- Implanted pacemakers, defibrillators, and other devices may be inactivated, reprogrammed, dislodged, or converted to an asynchronous mode- not beyond the 5gauss line until check list complete
- Induces a current sufficient to stimulate the peripheral nerve and muscle cells causing discomfort. - limit set on MRI
- Ventilators risk movement- outside 50 guass line or use MRI safe
- Hearing damage due noise of machine - wear ear protection
- Risk hyperthermia - . Radiofrequency radiation produced by the MR scanner and absorbed by the patient causes an increase in body temperature. Care long procedures
- Burning if electrodes/ monitor cables heat up - fibreoptic, high impedance, braided, short leads, and MRI-safe electrodes placed in a narrow triangle on the patient’s chest, padding between patient and cables
- Monitors can emit radio-frequencies that might interfere with the image quality - battery powered
- Pumps can deliver wrong dosages - use MRI safe or place in control room.
- Long length ventilator tubing - increased dead space
- Quench - in shut down occurs in MRI liquid helium expands and needs released risk asphyxiation- O2 sensors and ventilation
- Pre-op check - no pacemaker or ferrous material at risk of interference by MRI
- Induction in dedicated anaesthetic room adjacent to the MRI scanner but outside the 5 G contour prior to transfer to MRI department or use of deep sedation.
- Use MRI safe ventilator so can be used next to patient in MRI scanner.
- Maintenance of anaesthesia with volatile or TIVA - pumps MRI safe or extension to control room.
- Discontinue all non essential drug infusions
- IABP or MRI safe BP cuff (nylon)
- Pulse oximeter at distal site
- Electrodes MRI safe
- Cables fibre optic MRI safe and padded
- All alarms should be visual because of the noise made by the MR scanner, and the view of the monitor, anaesthetic machine and patient should be unobstructed at all times.
- Monitoring screens should be present in the MR control room to allow for remote monitoring of the patient so that the anaesthetist can leave the MR examination room.
- Ventilator if MRI conditional can sit next to patient therefore now brains/circle or t-piece used.
- Piped O2 with back up nonferrous cylinders available
- Scavenging of anaesthetics gases as usual
- Transfer back to anaesthetic room for waking and extubation.