1. GENERAL ANAESTHESIA
M. Attia
SVUH

2. Surgery Before Anesthesia50

3. Fun and Frolics led to Early Anesthesia50

4. General anesthetics (GAs)
History
General anesthesia was introduced
into clinical practice in the 19th century
with the use of volatile liquids such as
diethyl ether and chloroform.
Cardiac and hepatic toxicity limited
the usefulness of chloroform (out of date!).

5. William Morton (Boston, 1846) used
ether successfully to extract a tooth.

6. Pirogoff (Russia, 1847)
used ether.
Simpson (Glasgow, 1847)
used chloroform in obstetrics.
Queen Victoria gave
birth to her children
under chloroform anesthesia.

7. Te onset

8. The onset

9. Now

10. General Anaesthesia (GA)
unconsciousness
amnesia
analgesia.
A variety of drugs are given to the patient that have different effects with the overall aim of ensuring unconsciousness, amnesia and analgesia.

11. Overview General anaesthesia is a complex procedure involving :
Pre-anaesthetic assessment
Administration of general anaesthetic drugs
Cardio-respiratory monitoring
Analgesia
Airway management
Fluid management
Postoperative pain relief

12. Pre-anaesthetic evaluation
medical history, current medications.
previous anaesthetics.
History
age, weight, teeth condition.
Airway assessment, neck flexibility and head extension
Examination.
Relevant to age and medical conditions.
Investigations.

13. Pre-anaesthetic evaluation
The plan
best combination and drugs and dosages and the degree of how much monitoring is required .
fasting time
If airway management is deemed difficult, then alternative placement methods such as fiberoptic intubation may be used.

14. Aim Time Drugs Premedication induce drowsiness induce relaxation
from a couple of hours to a couple of minutes before the onset of surgery .
Time
narcotics (opioids such as fentanyl)
sedatives (most commonly benzodiazepines such as midazolam).
Drugs

15. Induction intravenous inhalational Faster onset
avoiding the excitatory phase of anaesthesia
inhalational
where IV access is difficult
Anticipated difficult intubation.
patient preference (children)

16. Intravenous Induction Agents
Commonly used IV induction agents include Prpofol, Sodium Thiopental and Ketamine.
They modulate GABAergic neuronal transmission. (GABA is the most common inhibitory neurotransmitter in humans).
The duration of action of IV induction agents is generally 5 to 10 minutes, after which time spontaneous recovery of consciousness will occur.

17. (1) Propofol
Short-acting agent used for the induction, maintenance of GA and sedation in adult patients and pediatric patients older than 3 years of age.
It is highly protein bound in vivo and is metabolised by conjugation in the liver.
Side-effects is pain on injection hypotension and transient apnea following induction

18. (2) Sodium thiopental
Rapid-onset ultra-short acting barbiturate, rapidly reaches the brain and causes unconsciousness within 30–45 seconds.
The short duration of action is due to its redistribution away from central circulation towards muscle and fat
The dose for induction is 3 to 7 mg/kg.
Causes hypotension, apnea and airway obstruction

19. Ketamine is an antagonist of NMDA-receptor.
It produces dissociative anaesthesia
(sedation, amnesia, dissociation, analgesia).
Ketamine can cause hallucinations and
unpleasant, brightly coloured dreams in 15% of
patients during recovery, which are very often
accompanied by delirium.
Its use is widespread in countries
where there are few skilled
specialists.
Usually it is applied mainly for
minor procedures in children
(10 mg/kg i.m.).

21. 1. Inhalational GAs Volatile liquids Gases Desflurane Isoflurane
Diethyl ether (out of date)
Gases
Nitrous oxide
Desflurane
Isoflurane
Enflurane
Halothane
Methoxyflurane
Sevoflurane
halogenated
anesthetics

22. inhalational induction agents
The most commonly-used agent is sevoflurane because it causes less irritation than other inhaled gases.
Rapidly eliminated and allows rapid awakening.

23. Inhaled Anesthetics Volatile anesthetics
Present as liquids at room temperature and pressure
Vaporized into gases for administration 90

24. Inhaled Anesthetics 24

25. Year of Introduction & Solubility

26. minimum alveolar concentration (MAC)
Anesthetic potency:
minimum alveolar concentration (MAC)
The potency of a drug is a measure of the quantity of
that drug that must be administered to achieve a given
effect. In the case of inhalation anesthetics potency is
described by the minimum alveolar concentration
(MAC). The MAC value is the minimum alveolar
concentration of anesthetic that produces immobility
in 50% of patients exposed to a standard
noxious stimulus.

27. Factor that decrease MAC
Factor that increase MAC
Hypothermia
Hyponatremia
Pregnancy
Old age
CNS depressants (sedatives, analgesics, injectable anesthetics)
Severe anemia
Severe hypotensia
Extreme respiratory acidosis
(PCO2 > 95 mmHg)
Hyperthermia
Hypernatremia
CNS stimulants (e.g. amphetamine, coffeinum)

28. Maintenance
In order to prolong anaesthesia for the required duration (usually the duration of surgery), patient has to breathe a carefully controlled mixture of oxygen, nitrous oxide, and a volatile anaesthetic agent. This is transferred to the patient's brain via the lungs and the bloodstream, and the patient remains unconscious.

29. Maintenance
Inhaled agents are supplemented by intravenous anaesthetics, such as opioids (usually fentanyl or morphine).
At the end of surgery the volatile anaesthetic is discontinued.
Recovery of consciousness occurs when the concentration of anaesthetic in the brain drops below a certain level (usually within 1 to 30 minutes depending upon the duration of surgery).

30. Maintenance
Total Intra-Venous Anaesthesia (TIVA): this involves using a computer controlled syringe driver (pump) to infuse Propofol throughout the duration of surgery, removing the need for a volatile anaesthetic.
Advantages: faster recovery from anaesthesia, reduced incidence of post-operative nausea and vomiting, and absence of a trigger for malignant hyperthermia.

31. Neuromuscular-blocking drugs
Block neuromuscular transmission at the neuromuscular junction.
Used as an adjunct to anesthesia to induce paralysis.
Mechanical ventilation should be available to maintain adequate respiration.

32. Non-depolarizing Depolarizing
Types of NMB
Non-depolarizing
competitive antagonists against ACh at the site of postsynaptic ACh receptors.
Examples:
Atracurium
Vecuronium
Rocuronium
Depolarizing
depolarizing the plasma membrane of the skeletal muscle fibre similar to acetylcholine
suxamethonium.
Osent: 30 seconds,
Duration: 5 minutes

33. Airway management
To maintain an open airway and enable mechanical ventilation, an endotracheal tube or laryngeal mask airways are often used.

34. Monitoring ECG Pulse oximetry (SpO2)
Blood Pressure Monitoring (NIBP or IBP)
Agent concentration measurement
Low oxygen alarm
Carbon dioxide measurement (capnography)
Temperature measurement
Circuit disconnect alarm

35. Postoperative Analgesia
oral pain relief medications
paracetamol and NSAIDS such as ibuprofen.
Minor surgical procedures
addition of mild opiates such as codeine
Moderate surgical procedures
combination of modalities
Patient Controlled Analgesia System (PCA) involving morphine
Major surgical procedures

36. Mortality rates Overall, about five deaths per million.
Most commonly related to surgical factors or pre-existing medical conditions ( haemorrhage, sepsis).
Common causes of death directly related to anaesthesia include:
1- aspiration of stomach contents
2- suffocation (due to inadequate airway management)
3- allergic reactions to anaesthesia
4- human error
5- equipment failure

37. McSleepy

38. Dr. Thomas M. Hemmerling of McGill’s Department of Anaesthesia and the Montreal General Hospital, who heads ITAG (Intelligent Technology in Anaesthesia research group), a team of anaesthesiologists, biomedical scientists and engineers.

39. “Think of ‘McSleepy’ as a sort of humanoid anaesthesiologist that thinks like an anaesthesiologist, analyses biological information and constantly adapts its own behaviour, even recognizing monitoring malfunction,” he added.

40. McSleepy welcomes you on board

48. It’s been coming for quite some time now, and it’s finally here
It’s been coming for quite some time now, and it’s finally here. The world’s first all-robotic surgery was performed on a Canadian man at Montreal General Hospital, who had his prostate successfully removed. The operation was performed by two main robots – McSleepy, which, as the name suggests, provides anesthesia to the patient, while the DaVinci system uses tools and performs movements way too delicate for any human to match.
The 360 degree arms of the DaVinci robot were guided by a team of surgeons viewing the details of the operation thanks to a 3D high-def camera. A constant stream of information on the patient’s vitals was also provided. So the human brains are still guiding things behind the scenes, but all the physical aspects are under the control of the robotic system.

49. McSleepy has a simpler task of pumping sleep- inducing drugs into a patient’s veins, but that is a vitally important aspect of any operation. The anesthesia bot has actually been in use for over two years, and DaVinci has helped out in many operations in this past, but this was the first time the two were combined, which eliminated the need for a human presence during the operation.
Dr. Aprikian, from the McGill University Health Center, stated his confidence that this will become a standard procedure in the future, and an all-robotic team will be able to improve results and save more lives on the operating table. While that sounds very promising, at least from all these news stories of successful robotic machines being employed in such operations, the trick will be getting the average Joe to feel comfortable enough knowing a robot is slicing his body. Even with a lot of reassurance, you know some people will feel skeptical about the process.

50. “We have been working on closed-loop systems, where drugs are administered, their effects continuously monitored, and the doses are adjusted accordingly, for the last 5 years,” said Dr. Thomas M. Hemmerling of McGill’s Department of Anaesthesia and the Montreal General Hospital, who heads ITAG (Intelligent Technology in Anaesthesia research group), a team of anaesthesiologists, biomedical scientists and engineers.
“Think of ‘McSleepy’ as a sort of humanoid anaesthesiologist that thinks like an anaesthesiologist, analyses biological information and constantly adapts its own behaviour, even recognizing monitoring malfunction,” he added.
The device claims to be much more accurate and precise and it can even be much more efficient than a human. To add in mobility to the device, the McSleepy communicates with personal digital assistants (PDAs) which allow distant monitoring and anesthetic control. The system has already been tested; however the researchers say that it will take approximately five years to get the system under the commercial spotlight.