pharma sheet # 26 - lama alsayed

General anesthesia

Applications of general anesthesia in dentistry are very limited we don’t use it except the patient was psychiatric or have some disability that you can’t deal with, and sometimes you have to apply it in children in case analgesic and hypnotic techniques don’t work, but you as a dentist are not allow to apply it, you have to transfer the patient to the hospital and then you work under general anesthesia, that’s why these drugs are in group B except for Nitrous oxide.
In general, in general anesthesia we render the patient toward unconsciousness he/she won’t be able to breathe alone we will have to use the ventilator (this is the difference between conscious sedation and general anesthesia)
General anesthesia is essential to surgical practice, because it renders patients analgesic, amnesia, and unconscious reflexes, while causing muscle relaxation and suppression of undesirable reflexes, this means that the patient won’t have any type of activity.
General anesthesia cannot be done by one drug or one agent, many agents have to be involved in general anesthesia, and not all anesthetic drugs can be analgesic and vice versa.
Anesthesia can be divided into 3 stages:
Induction, is the period time from onset of administration of the anesthetic to development of effective surgical anesthesia. Y3ne 2le mnda5el 2l patient feha bel anesthesia.
Maintenance, the period we carry the procedure under.
and recovery, the period after operation (post operation) the one that include nausea, vomiting and hallucination.
 the most important one of them is maintenance
 induction can be done by intravenous injection of some agent with very quick action for about 20 to 30 sec.
 examples of these short acting agents are barbiturate, Thiopental, which are used in induction of anesthesia.
 So General anesthesia is normally induced with an intravenous anesthesia like thiopental, that produce unconsciousness within 25 seconds
 After that, additional inhalation or intravenous drugs comprising anesthesia. The selected anesthesia combination is given to produce the desired depth of surgical anesthesia ( this is what we mean by maintenance ; to put the patient in the desired depth of anesthesia and maintain this situation during surgery )
 These agents make co2 center depression, they inhibit the respiratory center and they are very critical and have a narrow therapeutic index.

Halothane
 Used in the past , they are group of volatile ether origin called halogenated hydrocarbons
 It is a prototype of ether, ether was used in the past but nowadays it is only used with animals because it has many toxic side effect it can cause hepatitis
 Halothane is still used in children.
 There are many problem associated with general anesthesia because the mechanism of action is not fully understood yet; for example we have halothane, Enflurane, Isofluran, and nitrous oxide, each of which have different structure and shape but they all end with the same end result which is anesthesia the main reason for that is they may not have receptors, however there mechanism of action is quite strange.

 Halothane is metabolized in the body to tissue toxic materials, which may be responsible for the toxic reaction that some patients (especially females) developed after anesthetic.

 Halothane can cause hepatitis in one of every 350000 patient and this one usually is a female this happens because inside the patient body it can be metabolites in such a way that can cause hepatitis and this type of hepatitis is very difficult to treat it is irreversible ,,, but this side effect doesn’t happen with children.

 Is not hepatotoxic in pediatric patients, and it has a pleasant odor, which make it suitable in children for inhalation induction.

 We can’t use halothane for induction with adult because it is very slow in action also in adult it can cause arrhythmia and hepatitis but With children we can’t use the usual inductions for anesthesia (we don’t give them Thiopental or Propofol) instead we use halothane because they have small body so it act faster plus it has a pleasant odor and doesn’t cause hepatitis in children.

Enflurane
 It is better than halothane
 It has a disadvantage it can cause CNS excitation and can lead to seizure


Isoflurane
 It is widely used nowadays with adults, and it doesn’t cause arrhythmia or hepatitis but it can cause hypotension.
 Is widely used, and little metabolized to fluorine, thus it is not tissue toxic.
 It dilates the coronary artery and so may be beneficial for patient with ischemic heart disease this is one of its advantages.
 It has only one disadvantage that it can cause hypotension due to dilation of the vessels and this disadvantage is present in all of these drugs

Nitrous oxide
Previously we talked about sedation, there are three types of sedation Deep sedation we do it by IV, dental sedation, and inhalation sedation in which we use nitrous oxide
 It has a very nice activity as analgesic
 Note: when we do anesthesia we give some analgesic drug
 Nitrous oxide is a very potent analgesic but it can’t put the patient into deep anesthesia, so it is not used alone in general anesthesia what we do is that we give the patient halothane and then we give nitrous oxide so the patient will be under anesthesia and analgesia at the same time .

 Is frequently employed at concentration of 30% in combination with oxygen for analgesia, particularly in dental surgery.

 Nitrous oxide is the most widely used as a dental sedative.

 Its main disadvantages are that it has a speed movement, which may retard the oxygen uptake during recovery, thus causing diffusion hypoxia.


Intravenous anesthesia
Intravenous anesthesia is used in induction and these are of two types Barbiturates and Propofol, Propofol is better and more widely used.
• Propofol is widely used and has replaced thiopental as the first choice for anesthesia induction and sedation.
• Note: the doctor neglected these slide and said only these thing about them
As a summarization:
What happen in the hospital is First we do induction anesthesia by IV injection of Propofol Then we put the patient under Isoflurane for a certain period then we stop these drugs, and sometimes we give the patient diazepam for muscle relaxant , and sometimes we do intubation for the patient by succinyl coline.

Exceptional circumstances
These are the circumstances where you as a dentist may apply general anesthesia.
• For example treatment for certain groups of special needs patients, like disabled patient or psychiatric patients ….
• procedures which would be very unpleasant if the patient were conscious (such as very complex extractions of bony impacted wisdom teeth).
• certain other types of oral surgery.
• and people with an extreme anxiety of dental procedures for whom conscious IV sedation isn't enough.
note: these drugs have a very short half life because they enter through the lung and exist through the lung.

Local anesthesia
o it is an everyday procedure for you as a dentist.

o it is a type of agent that can be administered either topically or injectable ; it can be in the form of gel or ointment or injection act…

o The main idea of these drugs is to reduce the connections between the nerve ending and the brain by blocking the action potential, via preventing the propagation of the action potential, deferent level of local anesthesia means different level blocking of the action potential.


o Drugs used in local anesthesia resemble each other in their shapes ; they are of two types either esters or amides :
esters have been used in the past, they can cause allergy more than amides also they stay for a long time in the body and they are associated with other problems like cardiac arrhythmia, so they are replaced nowadays with amides, so most of the local anesthesia u use as a dentist are amides but some topical local anesthetic are esters (like the one used by football players during the match)

o Note: drugs in the family of local anesthesia ends with suffix caine.

o Note: all local anesthetic drugs have something to do with heart beat for example lidocaine is used as anti -arrhythmia but itself can case arrhythmia (this point will become more clear when we study the cardiovascular system ).

o Mechanism of action is: simply by blocking of Na+ channels preventing the initiation and spread of action potential.

o Most are used with adrenaline to prolong duration of action by constricting blood vessels.

Lidocaine
 is perhaps the most frequently used local anesthetic
 It is well absorbed by mucous membranes and is available in several dosage forms including:
 sterile injection, 1%, 1.5%, and 2% (which the most commonly used in dentistry), with or without epinephrine because sometimes you can’t give the patient epinephrine.
 topical ointment, 5%
 topical jelly, 2%
 topical oral spray, 10%, here the percentage increase to enable the drug to be absorbed and inter the tissue.

 these drugs are lipophilic ; they have an amide group at one end and a benzene ring (which is lipophlic) at the other end , the amide group can be tertiary or quaternary if it was quaternary it will have a positive charge on it , and each time the PH of the mucosa (where u supposed to administer the drug) changes the charge of the amide group will change and this will affect the absorption of the drug forcing you to increase the percentage to increase absorption, these drugs must be lipophilic to be able to penetrate the mucus membrane and Schwann cell of the nerve.
the PH of the mucosa can change if there is infection or inflammation or cancer in that area so the PH will be different than normal so sometimes if the patient has inflammation u won’t be able to perform anesthesia on him/her and you’ll have to ask the patient to go home and take antibiotic. Because inflammation can result in change in the PH of the mucosa which will lead to change response toward local anesthesia.



This is all for today good luck




Done by: lama alsayed
Pharma lec # 26
Date of the lec. 27-11