Anesthetics: Classification, types and uses.

1. General
Anesthetics By Abril Santos
Universidad Popular Autónoma del Estado de Puebla
International Intership Program

2. introduction
General anesthetics (GAs) are drugs
which:
• Reversible loss of all sensations and
consciousness.
• Loss of memory and awareness
with insensitivity to painful stimuli,
during a surgical procedure.

3. General Anesthesia
Need for
unconsciousness
‘Amnesia-hypnosis’
Need for analgesia
‘Loss of sensory and
autonomic reflexes’
Need for muscle
relaxation

4. • 1846 – Oliver Wendell Sr. “Anesthesia”
meaning:
Insensibility during surgery produced by
inhalation of ether.
• William T. G. Morton (dentist) was the first
to publicly demonstrate the use of ether
during surgery.
• 1860 – Albert Niemann  Cocaineas.

5. Types of Anesthesia
• General anesthesia
• Local and regional anesthesia
• Local Infiltration
• Topical block
• Surface anesthesia
• Nerve Block
• Spinal or subarachnoid anesthesia
• Peridural anesthesia

6. Balanced Anesthesia
Describes the multidrug approach to managing the patient needs.
Beneficial effects Adverse Qualities

7. Intraoperative, an ideal anaesthetic drug:
1. Would induce anesthesia smoothly, rapidly
2. Permit rapid recovery as soon as administration ceased.
*So a ‘balanced anesthesia’ is achieved by a combination of I.V and inhaled anesthesia and Pre-anaesthetic medications

8. General Anesthesia
Inhalational
Gas
Nitrous oxide
Zenon
Volatile liquids
Ether
Halothane
Enflurane
Isoflurane
Desflurane
Sevoflurane
Methoxyflurane
Intravenous
Slower acting
Dissociative
anesthesia
Ketamine
Opiod analgesia
Fentanyl
Benzodiazepines
Diazepam
Lorazepam
Midazolam
Inducing agents
Thiopentone sod.
Methohexitone sod.
Propofol
Etomidate
Droperidol

9. Stages of
anesthesia
Guedel (1920) described four stages with
ether anesthesia, dividing the III stage into 4
planes.
The order of depression in the CNS is:
1. Cortical centers
2. Basal ganglia
3. Spinal cord
4. Medulla

10. Surgical Period and GA protocol
Use pre-anesthetic 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

11. Pre-operative Period
• Meet the patient personally.
• Choose the right technique by
the preferences, case and
patient.
Use the ASA and GOLDMAN scale
for anaesthetic risk.

12. ASA
score
Use to measure risk for anaesthetic
procedures.

13. Pre-anaesthetic
Medications

14. Pre-anaesthetic Medications
Serve to
• Calm the patient, relieve pain
• Protect against undesirable effects of the subsequently administered anesthetics or the
surgical procedure.
• Facilitate smooth induction of anesthesia
• Lowered the dose of anaesthetic required

15. PreanestheticMedicine:
• Benzodiazepines; midazolam or diazepam: Anxiolysis & Amnesia.
• Barbiturates; pentobarbital: sedation
• Diphenhydramine: prevention of allergic reactions: antihistamines
• H2 receptor blocker- ranitidine: reduce gastric acidity.

16. Intraoperative Period
• Induction: Onset of anesthetic to the surgical anesthesia (I.V thiopental
or inhalated halothane or sevoflurane)
• Maintenance: Volatile anesthetics = good minute-to-minute control
over the depth. (halothane, isoflurane or fentanyl, morphine,
pethidine + N.M blocking agents)
• Recovery: From discontinuation of anesthesia until
• Consciousness
• Protective physiologic reflexes
Regained.

17. Post-operative Period
• N.M blocking agents and Opioids  worn off or reversed by
antagonists.
• Regained consciousness and protective reflex restored
• Relief of pain: NSAIDs
• Postoperative vomiting: metoclopramide, prochlorperazine

18. Properties of Intravenous Anesthetics.
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.

19. Non-barbiturate induction drugs effects
on BP and HR
Drug Systemic BP Heart rate
Propofol ↓ ↓
Etomidate No change or slight ↓ No change
Ketamine ↑ ↑

21. Local Anesthetics

24. Order of sensory
function block
1. Pain
2. Cold
3. Warmth
4. Touch
5. Deep pressure
6. Motor
*Recovery in reverse order.

25. Vasoconstrictors decrease the rate of vascular absorption which allows
more anesthetic to reach the nerve membrane and improves the depth
Vasoconstrictor
of anesthesia.

26. In Conclusion:
• Type of surgical procedure
• Duration of surgical procedure
• Type of anesthesia
• PATIENT
• Risk vs Benefit
• ALWAYS monitor

27. References
• American Society of Anesthesiologists (2011). Guidelines for patient care in
anesthesiology. Available online: http://www.asahq.org/For-
Members/Standards-Guidelines-and-Statements.aspx.
• Dorian RS (2010). Anesthesia of the surgical patient. In FC Brunicardi et al., eds.,
Schwartz’s Principles of Surgery, 9th ed., pp. 1731–1752. New York: McGraw-Hill.
• Brown DL (2010). Spinal, epidural and caudal anesthesia. In RD Miller et al., eds.,
Miller's Anesthesia, 7th ed., pp. 1611–1638. Philadelphia: Churchill Livingstone.
• Handbook of Local Anesthesia 6th ed. Stanley F. Malamed, DDS iii Handbook of
Local Anesthesia, 6th Edition

28. Thank You!