Anaesthesia for medical students!
What does it mean?
from Greek an-, "not/without" and aesthētos, "perceptible/ able to feel".
Anaesthetists- the largest hospital speciality
Anaesthesia for surgery
Research (physiology, altitude, basic science etc)
Resuscitation
Transport of ill patients
Management
Intensive care
Pain relief
‘Hospital at night teams’
Education
Drugs in Anaesthesia
The ‘Triad of anaesthesia’- a convenient way of thinking about anaesthetic drugs
A person having an anaesthetic will often have a combination from 1 each.
Consider CVS RS (airway / gas exchange) GI (reflux) NEURO METABOLIC effects
1 Hypnosis = unconsciousness
Intravenous
Propofol / Thiopentone / Etomidate / Methohexitone vs Ketamine
Effect all organ systems to differing extents
CVS – hypotension / dyrhythmias
RS – Airway reflexes / respiratory depression (apnoea)
GI -  oesophageal sphincter tone (regurgitation)
One off dose.. or infusions
Sedation vs anaesthesia
Metabolised by liver
Elderly, ill, hypovolaemic need less – greater side effects (eg cardiac arrest)
Ketamine – CVS stimulant, analgesia
Gaseous- volatile =…….ane’
‘Halothane’- (rarely used UK) Isoflurane / sevoflurane /desflurane / Enflurane
Given (1-8%) with Oxygen (30%+) in air or Nitrous oxide
Exhaled unmetabolised (80-99.4%)
Action to cause hypnosis…??
Effect most organ systems
CVS – hypotension / dysrhythmias
RS – Airway reflexes / respiratory depression
Can trigger Malignant hyperpyrexia
2 Analgeisa: WHO cancer analgesia ladder
Simple eg paracetamol
NSAIDS eg diclofenac/ ibuprofen
Opiods quick (eg fentanyl, alfentanil, remifentanil) vs slow/long (eg dia/morphine) vs
weak (eg Codeine Phosphate)
+ regional (eg nerve/root block)
+ central (spinal/epidural)
+ other eg N20, Tramadol, discussion, reassurance, splinting #
3 Paralysis: competitive vs non-competitive
Normal Physiology: at NMJ, ACh released from nerves crosses cleft- ACh, Ca++ release
Suxamethonium 30-60 secs on, 4-5 mins off, depolarises/non-competitive,
enzymes degrade (cholinesterase)
Vecuronium, atracurium, others etc longer onset minutes /offset 15-45mins: competitive
either fall off as more ACh is made (naturally) or cholinesterase inhibitors
Practicalities: the conduct of general anaesthesia
Also has three parts… different problems.. different solutions
1 Induction – from consciousness to the ‘surgical plane’ of anaesthesia
Either gaseous - slower, continuous respiration, not as nice(?)
or intravenous - fast, may cause apnoea, greater CVS effects
Airway very important during induction (competent cough/gag to absent)
Quick CVS effects also potentially dangerous
2 Maintenance – during surgery
Anaesthesia is CVS/RS depressant vs surgical stimulation
Haemorrhage, surgical manipulation (eg vagal effect) all CVS depressant etc
Can be gaseous or intravenous
3 Emergence – from anaesthesia to restoration of consciousness
The opposite of induction; potentially dangerous time
Airway important again
Other effects (CVS, pain, Neurological etc)
Practicalities: how to do it!
Preoperative visit (Hx Ex Ix Discussion Plan)
Anaesthetic room + surgery considerations
Airway: secure/definitive vs non-secure
Facemask, gudel airway, Laryngeal Mask Airway
Endotrachel tube (COETT), Tracheostomy
Breathing: spontaneous vs artificial ventilation (IPPV)
Which volatile/ carrier gas / breathing system / ventilator / paralysis
Circulation: IV Access / monitoring / fluids / drugs / blood
Drugs: emergency and other
Equipment: checked and appropriate?
Analgesia: systemic (what, how much, when) vs regional
Position and protection: supine/ side or prone; head down etc
warmers, pressure areas etc
Postoperative
Where should the patient go? (ward/HDU/ICU/other hospital)
Analgesia
Monitoring and observations
DVT prophylaxis
Fluid
Oxygen
Communication (surgeon, nurses, patient, relatives)
Could I have done anything different/better?