General anesthesia involves inducing a state of unconsciousness through administration of anesthetic drugs. It suppresses functions like breathing, circulation, and swallowing, requiring close monitoring. Common classes of general anesthetics include inhalational gases like nitrous oxide and volatile liquids, as well as intravenous drugs. Inhalational anesthetics act in the brain by enhancing GABA activity, while intravenous drugs like propofol and etomidate also act through GABA or by blocking NMDA receptors. Selection of anesthetic drugs is based on the procedure and patient characteristics to safely induce, maintain, and recover from anesthesia.

1. General Anaesthetic
Department Of Pharmacy
Course Teacher: Mohammad Ibrahim
Student Name:
Course name: Pharmacology-I
Course Code: 2210
Id: 999-18-09

2. Introduction

3. Introduction
General anesthesia is the induction of a state of
unconsciousness with the absence of pain sensation
over the entire body, through the administration of
anesthetic drugs. It is used during certain medical and
surgical procedures.
3

4. Function
General anesthesia suppresses many of your body's
normal automatic functions, such as those that control
breathing, heartbeat, circulation of the blood (such as
blood pressure), movements of the digestive system, and
throat reflexes such as swallowing, coughing, or gagging
that prevent foreign material from being inhaled into
your lungs (aspiration).
Because these functions are suppressed, an anesthesia
4

5. Function
specialist must carefully keep a balance of medicines
while watching your heart, breathing, blood pressure,
and other
vital functions. An endotracheal (ET) tube or a laryngeal
mask airway device is usually used to give you an inhaled
anesthetic and oxygen and to control and assist your
breathing.
5

6. Drug class
General
anesthetics
Inhalational
Gas
Nitrous oxide
Zenon
Volatile
liquids
Ether
halothane
enflurane
isoflurane
desflurane
Sevoflurane
methoxyflurane
Intravenous
Slower acting
Dissociative
anesthesia
ketamine
opioid
fentanyl
Benzodiazepines
diazepam
lorazepam
midazolam
Inducing agents
Thiopentone
methohexitone
propofol
Etomidate
droperidol
6

7. mechanism of action of drug class
Inhalational anaesthetic: An inhalational anaesthetic is
a chemical compound possessing general
anaesthetic properties that can be delivered via inhalation.
They are administered by anaesthetists (a term which
includes anaesthesiologists, nurse anaesthetists,
and anaesthesiologist assistants) through an anaesthesia
mask, laryngeal mask airway or tracheal tube connected to
an anaesthetic vaporiser and an anaesthetic delivery
system. Agents of significant contemporary clinical interest
include volatile anaesthetic agents such
as isoflurane, sevoflurane and desflurane, as well as certain
anaesthetic gases such as nitrous oxide and xenon.
7

8. mechanism of action of drug class
Volatile anaesthetics: Volatile anaesthetic agents
share the property of being liquid at room temperature,
but evaporating easily for administration by inhalation.
All of these agents share the property of being
quite hydrophobic (i.e., as liquids, they are not
freely miscible with water, and as gases they dissolve in
oils better than in water). The ideal volatile anaesthetic
agent offers smooth and reliable induction and
maintenance of general anaesthesia with minimal
effects on other organ systems. In addition it is
odourless or pleasant to inhale; safe for all ages and
in pregnancy; not metabolised; rapid in onset and
offset;
8

9. mechanism of action of drug class
potent; and safe for exposure to operating room staff. It is
also cheap to manufacture; easy to transport and store,
with a long shelf life; easy to administer and monitor
with existing equipment; stable
to light, plastics, metals, rubber and soda lime; non-
flammable and environmentally safe. None of the
agents currently in use are ideal, although many have
some of the desirable characteristics. For example,
sevoflurane is pleasant to inhale and is rapid in onset
and offset. It is also safe for all ages. However, it is
expensive (approximately 3 to 5 times more expensive
than isoflurane), and approximately half as potent as
isoflurane.
9

10. mechanism of action of drug class
Gases: Other gases or vapors which produce general
anaesthesia by inhalation include nitrous oxide,
cyclopropane and xenon. These are stored in gas
cylinders and administered using flowmeters, rather
than vaporisers. Cyclopropane is explosive and is no
longer used for safety reasons, although otherwise it
was found to be an excellent anaesthetic. Xenon is
odourless and rapid in onset, but is expensive and
requires specialized equipment to administer and
monitor. Nitrous oxide, even at 80% concentration, does
not quite produce surgical level anaesthesia in most
persons at standard atmospheric pressure, so it must be
used as an adjunct anaesthetic, along with other
agents.
10

11. mechanism of action of drug class
Intravenous anesthetics:Intravenous (i.v.)
anesthetics include etomidate, midazolam,
propofol, thiopental, ketamine, and opioid
agonists. The first four agents act by enhancing
the activity of the inhibitory neurotransmitter γ-
aminobutyric acid (GABA) in the CNS. Ketamine
antagonizes the effect of the excitatory
neurotransmitter N-methyl-D-aspartate (NMDA)
on NMDA receptors, and opioid agonists
stimulate opioid receptors.
11

12. mechanism of action of drug class
The ideal i.v. anesthetic agent has a rapid onset of
action and is quickly cleared from the
bloodstream and CNS, facilitating control of the
anesthetic state (e.g., allowing titration of
effect). The ideal agent also protects vital tissues,
has other desirable pharmacologic effects (e.g.,
an antiemetic effect), does not affect the
circulatory system or cause other adverse
effects, and is inexpensive.
12

13. mechanism of action of drug class
Propofol is the most widely used i.v. anesthetic
agent for induction. It is highly lipophilic and
distributes rapidly into the CNS and other
tissues, which accounts for its rapid onset of
action. Propofol produces unconsciousness
within the time it takes for the drug to travel
from the injection site to the brain, which is
referred to as one "arm-brain circulation time"
and requires less than one minute.
13

14. mechanism of action of drug class
The onset of anesthesia is smooth, although the
drug can cause pain at the injection
site. Propofol is rapidly and extensively
metabolized in the liver and at extrahepatic
sites, which means it has a high rate of total
body clearance. The drug has a direct antiemetic
effect through an unknown mechanism. It also is
euphorigenic, but does not have residual
psychotic effects as does ketamine.
14

15. mechanism of action of drug class
Adult patients often prefer that anesthesia be
induced by i.v. injection because induction
occurs more quickly and smoothly and is
associated with less claustrophobia. In 40
patients undergoing ophthalmic surgery using
either inhaled sevoflurane plus nitrous oxide or
i.v. propofol for induction, satisfaction with
induction of anesthesia was assessed afterward
by asking patients whether
15

16. mechanism of action of drug class
they would be willing to receive the same
anesthetic agent again.[2] More patients given
propofol (90%) were willing to receive the same
anesthetic again than was the case with
sevoflurane (50%). The difference may be
attributed to claustrophobia. However, children
often prefer an inhalation induction of
anesthesia because of a fear of needles.
Inhalation induction also may be useful in
patients with a lack of venous access.
16

17. pharmacological action
Potent anesthetic, weak analgesic.
Administered with nitrous oxide, opioids or local
anesthetics
Being replaced by other agents due to its adverse
effects
Isoflurance: Undergoes little metabolism, not
toxic to the liver or kidney
Does not induce cardiac arrhythmias
Produces dose-dependent hypotension due to
peripheral vasodilation
17

18. pharmacological action
Desflurance:Provides very rapid onset and recovery due
to its low blood solubility, the lowest of all the volatile
anesthetics Popular anesthetic for outpatient surgery
Irritating to the airway and can cause laryngospasm,
coughing, and excessive secretions,
Degradation is minimal, tissue toxicity is rare.
Sevoflurance:Low pungency, allowing rapid induction
without irritating the airway, making it suitable for
inhalation induction in pediatric patients Replacing
halothane for this purpose Metabolized by the liver, and
compounds formed in the anesthesia circuit may be
nephrotoxic
18

19. pharmacological action
Nitrous Oxide:Non-irritating and a potent analgesic but
a weak general anesthetic
Nitrous oxide is frequently employed at concentrations of
30–50% in combination with oxygen for analgesia,
particularly in dental surgery.
Nitrous oxide at 80 percent (without adjunct agents)
cannot produce surgical anesthesia
Combined with other, more potent agents to attain pain-
free anesthesia
Mechanism of action is unresolved, might involve activity
on GABAA and NMDA receptors
Least hepatotoxic of all inhaled anesthetics
19

20. Side Effects
20

21. Precaution
21

22. Contamination
22

23. Contamination
23
Climate effect of inhaled anaesthetics:
Almost all areas of human activity have the potential
to influence climate. The administration of inhalation
anaesthetics is one such activity. However, since the
first dedicated study in 19891 of the possible role of
halogenated anaesthetics, they have received only
sporadic interest. Two recent papers, published in this
issue of the British Journal of Anaesthesia and
in Anesthesia and Analgesia3 earlier this year, have
refocused attention on isoflurane, desflurane, and
sevoflurane.

24. Contamination
24
To be clear, such anaesthetics currently make only
a very minor contribution to climate change. Using
an estimate of the amount currently in the
atmosphere (around a part per trillion), these three
gases contribute only 0.02% of the climate effect
that results from the increases in carbon dioxide
due to human activity.

25. market preparation
25
Market Value and Forecast
In terms of value, the global general anaesthesia
drugs market is estimated to expand at a CAGR of
3.8% during the forecast period. Moreover, global
general anaesthesia drugs markets value is
expected to increase to US$ 5,549.7 Mn by 2025
end.

26. market preparation
26
Market Dynamics:
Growth of the global general anaesthesia drugs
market is mainly driven by rising incidences of
cardiovascular diseases, chronic respiratory diseases,
craniomaxillofacial surgeries and accidents. However,
lack of a single effective drug for all type of surgeries,
side effects and complications during the surgical
procedure, lack of skilled anaesthesiologists and
certified registered nurse anaesthesiologists,
inadequate insurance coverage, coupled with high
prices of these drugs are restraining market growth.

27. market preparation
27
In addition, side effects such as nausea,
vomiting, allergy, sleep apnea and
complications during surgical procedures
are anticipated to drive the demand for
improvement in the quality of drugs.In
addition, side effects such as nausea,
vomiting, allergy, sleep apnea and
complications during surgical procedures
are anticipated to drive the demand for
improvement in the quality of drugs.

28. market preparation
28
Segmentation by Product:
The global general anaesthesia drugs market is
segmented on the basis of molecule/product. In
terms of value, the propofol segment is estimated
to account for over 29.8% share to the global
general anaesthesia drugs market by 2015 end and
is expected to remain dominant during the forecast
period.

29. Patient factors in selection of
anesthesia:
Drugs are chosen to provide safe and efficient anesthesia based
on:
1. The type of the surgical or diagnostic procedure
2. Patient characteristics such as organ function, medical
conditions, and concurrent medications. e.g., IHD, HTN,
hypovolemic shock, bronchial asthma.
Status of organ systems:
Cardiovascular system:
whereas the hypotensive effect of most anesthetics is
sometimes desirable, ischemic injury of tissues could follow
reduced perfusion pressure.
29

30. Stages and depth of anesthesia
General anesthesia has three stages: induction, maintenance, and
recovery.
Use preanesthetic medication
↓
Induce by I.V thiopental or suitable alternative
↓
Use muscle relaxant → Intubate
↓
Use, usually a mixture of N2O and a halogenated hydrocarbon→
maintain and monitor.
↓
Withdraw the drugs → recover
30

31. Depth of Anesthesia (GUEDEL’S Signs)
Guedel (1920) described four sequential stages with ether anaesthesia, dividing the stage 3
into 4 planes. The order of depression in the CNS is: Cortical centers→basal ganglia→spinal
cord→medulla
Stage of
Analgesia
• analgesia and amnesia, the patient is conscious and
conversational. Starts from beginning of anaesthetic inhalation
and lasts upto the loss of consciousness
• Pain is progressively abolished
• Reflexes and respiration remain normal
• Use is limited to short procedures
Stage of
Delirium
• From loss of consciousness to beginning of regular respiration
• Patient may shout, struggle and hold his breath; muscle tone
increases, jaws are tightly closed, breathing is jerky; vomiting,
involuntary micturition or defecation may occur
• Heart rate and BP may rise and pupils dilate due to sympathetic
stimulation
• No operative procedure carried out
• Can be cut short by rapid induction, premedication 31

32. Depth of Anesthesia (GUEDEL’S Signs)
Surgical
anaesthesia
• Extends from onset of regular respiration to cessation of
spontaneous breathing. This has been divided into 4 planes
which may be distinguished as:
• Plane 1 roving eye balls. This plane ends when eyes become
fixed.
• Plane 2 loss of corneal and laryngeal reflexes.
• Plane 3 pupil starts dilating and light reflex is lost.
• Plane 4 Intercostal paralysis, shallow abdominal respiration,
dilated pupil.
Medullary
paralysis
• Cessation of breathing to failure of circulation and death.
• Pupil is widely dilated, muscles are totally flabby, pulse is
thready or imperceptible and BP is very low
32

33. Depth of Anesthesia (GUEDEL’S Signs)
33

34. 34
Properties of Intravenous Anesthetic Agents
Drug Induction and
Recovery
Main Unwanted
Effects
Notes
thiopental Fast onset
(accumulation
occurs, giving slow
recovery) Hangover
Cardiovascular and
respiratory depression
Used as induction agent
declining. ↓ CBF and O2
consumption
Injection pain
etomidate Fast onset, fairly
fast recovery
Excitatory effects
during induction
Adrenocortical
suppression
Less cvs and resp
depression than with
thiopental, Injection site pain
propofol Fast onset, very fast
recovery
cvs and resp
depression
Pain at injection site.
Most common induction
agent. Rapidly metabolized;
possible to use as
continuous infusion. Injection
pain. Antiemetic
ketamine Slow onset, after-
effects common
during recovery
Psychotomimetic
effects following
recovery, Postop
nausea, vomiting，
salivation
Produces good analgesia
and amnesia. No injection
site pain
midazolam Slower onset than
other agents
Minimal CV and resp
effects.
Little resp or cvs depression.
No pain. Good amnesia.

35. 35