The PowerPoint is an overview of the pharmacology of anesthesia that can offer great assistance to beginner medical and nursing students who are oftentimes confused about these drugs

1. PHARMACOLOGY
OF ANESTHETIC DRUGS
D. Sogoni|BScN

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DEFINITION OF TERMS
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Anesthesia- Is a state of controlled, temporary loss of sensation
or awareness that is induced for medical purposes. It may
include some or all of analgesia (relief from or prevention of
pain), paralysis (muscle relaxation), amnesia (loss of memory),
and unconsciousness.
Anesthetic agent- Any agent that produces a local or general loss
of sensation, including pain.
Analgesia – It is the inability to feel pain/ to relieve pain without
causing the loss of consciousness.
Pain - Highly unpleasant physical sensation caused by illness or
injury.

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ORIGIN OF ANESTHESIA
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• Early anesthesia can be traced back to ancient times (Babylonians,
Greeks, Chinese and Incas), but one of the first European accounts
occurred in the 1200s when Theodoric of Lucca, an Italian physician and
bishop, "used sponges soaked with opium and mandragora [from the
mandrake plant] for surgical pain relief,“
• One name stands out amongst all others when the founder of modern
anesthesia is discussed, William T.G. Morton (1819-1868). A young
Boston Dentist, Dr. Morton had been in the search for a better agent
than what had been used by many dentists: nitrous oxide.

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ORIGIN OF ANESTHESIA CONT….
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•Genesis 2:21-22
So the LORD God caused a deep sleep to fall upon the
man, and while he slept took one of his ribs and closed up
its place with flesh; [22] and the rib which the LORD God
had taken from the man he made into a woman and
brought her to the man…She shall be called Woman,
because she was taken out of Man."

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TYPES OF ANESTHESIA
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• There are three main categories of anesthesia used during surgery and
other procedures: general anesthesia, regional anesthesia, and local
anesthesia
• General anesthesia- it is the temporary loss of feeling and a complete
loss of awareness that feels like a very deep sleep.
• Regional anesthesia – makes an area of the body numb to prevent the
patient from feeling pain. It can completely block sensation to the area of the
body that requires surgery/ is in pain.
• Local anesthesia – It is a drug that’s able to cause temporary loss of
feeling in one small area of the body. The drug is usually
infiltrated/applied directly at the area of desired effect.

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GENERAL ANESTHESIA
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Mechanism Of Action
• General the anesthetics inhibit or block excitatory ligand-gated ion
channels and enhance the sensitivity of inhibitory ion channels such
as γ-aminobutyric acid A (GABAA) receptor.
• Examples include ; propofol, etomidate, ketamine, isoflurane,
benzodiazepines (midazolam, lorazepam, diazepam), and
barbiturates (sodium thiopental, methohexital, amobarbital,
Butabarbital, pentobarbital, secobarbital )
• Common procedures where general anesthesia is used include
major operations, such as knee and hip replacements, heart
surgeries, laparotomies and many types of surgical procedures to
treat cancer.

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REGIONAL ANESTHESIA
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Mechanism of action
• Local anesthetics produce anesthesia by inhibiting excitation of nerve
endings or by blocking conduction in peripheral nerves. This is achieved by
anesthetics reversibly binding to and inactivating sodium channels.
• There are three types; spinal, epidural, and nerve block. This is classically
depended upon the exact place it is injected.
• Examples include quicker onset like lidocaine and mepivacaine. The longer-
acting ones are bupivacaine and ropivacaine.
• Operations routinely done with regional anesthesia include orthopedic
surgery on an extremity (arm, leg, hand, or foot), female reproductive
surgery (gynecological procedures and cesarean section) or male
reproductive surgery such as prostatectomy , and for operations on the
bladder and urinary tract.

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LOCAL ANESTHESIA
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Mechanism of action
• Like regional anesthetics, they inhibiting excitation of nerve
endings and or practically block conduction of the nerve axons.
• The main difference between local anesthesia is that local is
injected at the site while regional is done in or around the spinal
cord; and sometimes along the nerve roots or fibers.
• Local anesthetics can be administered either as injectables for
minor procedures such as circumcision, biopsy, or wound
stitching ; or as topical applications to manage pain after minor
burns, bites, gums or hemorrhoids.
• Examples include lidocaine, bupivacaine, ropivacaine, prilocaine,
etidocaine, mepivacaine and levobupivacaine.

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SELECTING THE BEST ANESTHESIA FOR EACH PATIENT
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Anesthesia is selected using various criteria that include;
• The medical-surgical diagnosis and Pre-operative examination.
There are some surgeries that ideally require a specific type of
anesthesia.
• The type and extent of the surgical procedure. Major surgeries
tend to go with general anesthesia, however not always.
• Experience and training of anesthetist or whoever is
administering the drug.
• Availability of drugs and equipments.

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SPECIAL CONSIDERATIONS BEFORE GENERAL ANESTHESIA FOR THE PREOPERATIVE PATIENT
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• Patient should have been examined by the surgeon, anesthetist and
nurse before the procedure.
• Nil per oral for not less than 8 hours unless it is an emergency surgery
• Full set of vital signs taken
• Premedication done
• Lab work such as blood grouping and crossmatch, complete blood count,
UECs etc. done
• Catheterization done; and other procedure specific requirements
checked.
• Signed informed consent either by the patient or closes relative where
the patient was incapacitated to give it.

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COMMON SIDE EFFECTS OF GENERAL ANESTHESIA
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Most patient often take about 45 minutes to one hour for the strong effects of
general anesthesia to wear off. Some patients however still continue to
experience these side effects within the first 24 hours after the procedure. An
even smaller percentage will experience them for a longer period not exceeding
a week.
• Shivering
• Sleepiness
• Nausea or vomiting
• Dry mouth
• Sore throat
• Muscle aches
• Itching

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COMMON SIDE EFFECTS OF REGIONAL ANESTHESIA
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•Risk of systemic toxicity if the anesthetic is absorbed
through the bloodstream into the body.
•Infection
•Hematoma ; swelling, or bruising at the injection site
•Post lumber puncture headache
•Hypotension
•Neurogenic and cardiac toxicity

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COMMON SIDE EFFECTS OF LOCAL ANESTHESIA
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Local anesthesia are usually very safe. However, if it is given too much of it
and it ends up in blood, it could result into
• tinnitus
• Dizziness
• twitching
• a metallic taste in your mouth
In extremely high doses, anesthesia may cause:
• seizures
• low blood pressure
• Abnormal heart rate

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ASSIGNMENT
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• Write drug cards for the following drugs
1. Ketamine
2. Diazepam
3. Halothane
4. Nitrogen oxide
5. Lignocaine
6. Bupivacaine

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REFERENCES
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• Featherstone, D. (2011). History of Anaesthesia Society. Retrieved 7 October 2021, from
http://www.histansoc.org.uk/
• Robinson, D., & Toledo, A. (2012). Historical Development of Modern Anesthesia. Journal Of
Investigative Surgery, 25(3), 141-149. doi: 10.3109/08941939.2012.690328
• Midhudson, m. (2020). Pre-Op Instructions Before General Anesthesia | Kingston, NY | Mid-Hudson
Oral & Maxillofacial Practice, PC. Retrieved 11 October 2021, from
https://www.midhudsonoralsurgeon.com/pre-op-instructions-before-general-
anesthesia#:~:text=You%20should%20not%20have%20anything,the%20evening%20before%20your%
20appointment.
• FJ, S., & BC, C. (1985). Advantages and disadvantages of regional anesthesia for cesarean section. A
review. Retrieved 11 October 2021, from https://pubmed.ncbi.nlm.nih.gov/4078816/
• Torpy, J. (2011). Regional Anesthesia. JAMA, 306(7), 781. doi: 10.1001/jama.306.7.781
• Weatherspoon, D. (2018). Local Anesthesia: Uses, Types, Process, Risks, and Pregnancy Safety.
Retrieved 11 October 2021, from https://www.healthline.com/health/local-anesthesia#types
• (drugs.com2021). Retrieved 11 October 2021, from https://www.drugs.com/illicit/ketamine.html

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