Upload
trankhuong
View
218
Download
0
Embed Size (px)
Citation preview
Anaesthesia for ECT Session 1Dr Richard CreeConsultant in Anaesthesia & ICU
Roseberry Park Hospital andThe James Cook Hospital, Middlesbrough
Anaesthesia for ECT
CHAPTERS
1. The principles of anaesthesia2. Anaesthetic pharmacology
Induction agents Muscle relaxants
3. The physiological effects of ECT4. Anaesthetic assessment
Contraindications for ECT Patient assessment Investigations
The Principles of Anaesthesia
What is anaesthesia?
“without sensation” Oliver Wendell Holmes, 1846
“reversible lack of awareness”General anaesthesia
The Principles of Anaesthesia
History
Alcohol – Mesopotamia 3000BC Opium – Sumeria 2000BC Mafeisan – China 300BC Dwale – UK 1200-1500 Morphine – Germany 1804 Nitrous Oxide – UK 1844 Ether – USA 1846 Chloroform – UK 1847 Cocaine – 1877 Thiopentone - 1934 Curare – 1940s Halothane – 1950s
The Principles of Anaesthesia
How do Anaesthetics Work?
Biochemical mechanism unclear Myriad sites of action
Anaesthesia triad
1. Anaesthesia2. Analgesia3. Muscle relaxation
The Principles of Anaesthesia
Aim of ECT Anaethsesia
Short period of unconsciousness to allow 1. The muscle relaxation2. The ECT stimulus 3. The seizure
Return to full consciousness Protection from the adverse physiological
effects of the above
The Principles of Anaesthesia
Anaesthetic Drugs
Induction agents1. Propofol2. Thiopentone3. Etomidate4. Methohexitone5. Sevoflurane6. KetamineMuscle relaxants1. Suxamethonium2. Others
Anaesthetic Drugs
Propofol
PROS Rapid onset Short action Nice! - Less nausea Suppresses haemodynamic response
CONS Raises seizure threshold Short seizures – but no effect on efficacy Painful
Anaesthetic Drugs
Thiopentone (Thiopental)
PROS Longer seizures
than Propofol
CONS Raises seizure
threshold Cardiac arrhythmias Less effect on haemodynamic stability
Anaesthetic Drugs
Etomidate (Hypnomidate)
PROS Lowers seizure threshold –
useful in refractory seizures Long seizures
CONS No suppression of haemodynamic response Nausea Painful Abnormal movements Adrenal suppression?
Anaesthetic Drugs
Methohexitone(Methohexital/Brevital)
PROS ‘Gold standard’ Rapid onset, rapid recovery No effect on seizure threshold
or duration
CONS Expensive Unlicensed since 2000 Difficult to obtain
Anaesthetic Drugs
Sevoflurane
Inhalational anaesthetic
No effect on seizure Useful for difficult venous access Attenuates post-ECT uterine contraction
in 3rd trimester of pregnancy
Requires anaesthetic machine, vapouriser & scavenging
Anaesthetic Drugs
Ketamine
PROS Longer seizures Less memory deficit?
CONS Slow onset Longer acting Emergence phenomena - hallucinations Less attenuation of haemodynamic
response
Anaesthetic Drugs
Opioids
PROS Attenuate haemodynamic response Alfentanil & remifentanil prolong seizures Single agent in refractory seizures?
CONS Fentanyl shortens seizure duration Prolong recovery time
Anaesthetic Drugs
Muscle Relaxants Suxamethonium
Depolarising muscle relaxant
PROS Rapid onset Short acting
CONS Fasciculation & muscle pain Suxamethonium apnoea Malignant hyperpyrexia Masseter spasm
Anaesthetic Drugs
Muscle Relaxants- Atracurium, Rocuronium
Non-depolarising muscle relaxant
PROS It isn’t suxamethonium!
CONS Slow onset Long acting
– maintain anaesthesia & ventilation
The Physiological effects of ECT
ECT stimulus results in ….
1. Increased cerebral blood flow2. Generalised tonic-clonic seizure3. Cardiovascular effects
Parasympathetic Sympathetic
4. Complex neuro-endocrine effects – why it works!
Physiological effects of ECT
Increased Cerebral Blood Flow
Cerebral blood flow (CBF) increases by over 100% in ECT
Munroe-Kelly doctrine Brain in a tight, rigid box – the skull Brain 80% Blood 12% and CSF 8%
Increasing CBF → Increased intra-cranial pressure (ICP)
Risks – recent strokes or haemorrhages, aneurysms, AV malformations, brain tumours etc.
Physiological effects of ECT
The Seizure
Risks of the tonic-clonic convulsion:
1. Damage to teeth, tongue and mouth- Direct effect of the stimulus
2. Long bone fractures
3. Avulsion fractures
4. Cervical spine injury e.g. rheumatoid disease or ankylosing spondylitis
Physiological effects of ECT
Cardiovascular Effects
Autonomic nervous system effects –
1. Parasympathetic nervous system During the stimulus Effects mediated by acetylcholine Bradycardia – rarely asystole Salivation
May be exacerbated by suxamethonium Can prevent with glycopyrrolate or atropine
Physiological effects of ECT
Cardiovascular Effects
2. Sympathetic nervous system During the seizure Effects mediated by adrenaline Effects fade over 10-20 mins Tachycardia Hypertension
Effects attenuated by Anaesthetic agents - propofol Cardac drugs – e.g. beta-blockers Short acting opiates
Physiological effects of ECT
Cardiovascular Effects
Ensure optimal treatment ofunderlying
cardiovascular conditions
Anaesthetic Assessment
ASA GradeAmerican Society of Anaesthesiologists (ASA) grading system
Grade Description Example
I Healthy
II Mild systemic disease –no functional limitation
Well controlled hypertension, diabetes, asthma
III Moderate systemic diseaseDefinite functional limitation
COPD with exercise limit. Diabetes with complications. Exertional angina
IV Severe systemic diseaseConstant threat to life
Unstable angina. COPD-breathless at rest
V Moribund – Expected to die in 24hours
Critically ill ICU patient undergoing emergency surgery
Anaesthetic Assessment
ASA GradeASA grade – Anaesthetic assessment for ECT
ASA Grades 1 & 2
ASA Grade 3
ASA Grade 4
Can be seen by Anaesthetist immediately prior to ECT. Routine investigations & assessment only required.
May need further assessment, investigations and specialist opinion prior to ECT. Consider conducting treatment in main operating theatre suite.
Will require thorough assessment, investigation and specialist opinion prior to ECT. Treatment will need to be conducted in main operating theatre suite. Full consideration of risks vs. benefits.
Anaesthetic Assessment
Contra-Indications to ECT
Relative contra-indications:
1. Increased intra-cranial pressure Brain tumour Recent stroke Untreated cerebral aneurysm or AVM
2. Cardiovascular disease Recent acute coronary syndrome Unstable angina Untreated cardiac failure Aortic or thoracic aneurysm Severe valvular heart disease
Anaesthetic Assessment
Contra-Indications to ECT
3. Musculo-skeletal disease Unstable cervical or lumbar spine - acute
injury or chronic disease Severe osteoposis Unstabilised fractures
4. Phaechromocytoma5. Deep venous thrombosis6. Pregnancy7. Cochlear implant?
Anaesthetic Assessment
Investigations
Local guidelines as agreed with your anaesthetist
Results must be available for the anaesthetic assessment before first treatment
Often do not need repeating during treatment period
New tests may not be required if already performed within the previous three months
Anaesthetic Assessment
Full blood count
Rationale – to check O2 carrying capacity
Perform in – All patients over 60 yrs ASA grades III or IV Any cardiorespiratory disease Renal disease Diabetes Some antipsychotics – e.g. Olanzapine
Anaesthetic Assessment
Urea & Electrolytes
Electrolyte disturbance → arrhythmias→ affect seizure threshold
Perform in – All patients over 60 yrs ASA grades III or IV Any cardiorespiratory disease Renal disease Poor fluid intake / dehydration Diabetes Lithium
Anaesthetic Assessment
Other Blood Tests
Clotting & INRDetect over anti-coagulation inpatients taking warfarin
Sickle Cell Anaemia ScreenDetect risk of sickle cell crisis in patients ofAfrican, Caribbean, Mediterranean or Asianethnic origin
Anaesthetic Assessment
Other Blood Tests
Thyroid function
Liver functionPatients with known liver disease or alcoholexcess and those taking drugs affecting liver function – e.g. olanzipine, carbamazepine
Pregnancy testAny woman of childbearing ageAllows discussion of risks vs. benefits of ECT
Anaesthetic Assessment
Electrocardiogram
Rationale – detect myocardial ischaemia & previous cardiac damage, risk of arrthymias
Useful baseline Perform in –
All patients over 60 yrs ASA grades III or IV Cardiorespiratory disease Diabetes
Anaesthetic Assessment
X-Rays
Chest X-ray and / or pulmonary function tests only after discussion with anaesthetist
Other imaging / tests only on specialist advice