General anesthesia involves making a patient unconscious and free from pain during surgery. It typically involves three components - sleep, analgesia, and muscle relaxation. Preparations include checking equipment and positioning the patient. Induction can be done via inhalation of gases or intravenous drugs and maintenance can be achieved through inhalation or intravenous methods. Local anesthesia involves blocking nerve transmission in a specific area to reduce pain from procedures.

1. Principals of Anesthesia
Prepared by:
Syed umair
Academic coordinator
Anesthesia and critical care
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2. Types of Anesthesia
General
Anesthesia
Local
Anesthesia
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3. General Anesthesia
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• The word Anesthesia means absence of sensation,
and general anesthesia therefore implies
unconsciousness.
• General Anesthetics include any agents capable of
producing total insensibility in a reversible manner,
it can be inhalational, intravenous or combined.

4. What is Surgical anesthesia?
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• Its a state of harmless and reversible insensibility
which allows operations of considerable magnitude
to be carried out without hindrance to the surgeon
or detriment to the patient.
• It is convenient to consider this anesthetic state as
consisting of a triad of SLEEP, ANALGESIA and
MUSCLE RELAXATION.

5. Preparations for GA
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• Before giving anesthesia, considerations should be
given to the induction of anesthesia, the position of
the patient on the operating table, monitoring, the
use of intravenous fluids or blood transfusion,
postoperative care and recovery facilities which will
be required.
• The availability and function of all anesthetic
equipment should be checked before starting.

6. Induction of GA
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A. Inhalational induction.
• Can be done by one of the inhalational anesthetic
agents which are: Halothane, Isoflurane and
Sevoflurane.
• If spontaneous ventilation is to be maintained
throughout the procedure, the mask is applied more
firmly as consciousness is lost and the airway can
be supported by guedel airway or by laryngeal
mask or by endotracheal tube.

7. Induction of GA cont.
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• Indications for Inhalational induction are:
1. Young children.
2. Upper airway obstruction.
3. Lower airway obstruction with foreign body.
4. Bronchopleural fistula.
. Difficulties and Complications:
1. Slow induction of anesthesia.
2. Airway obstruction, bronchospasm.
3. Laryngeal spasm

8. Induction cont..
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B. Intravenous Induction.
Monitoring should be started on the patient including
Spo2, Blood pressure, ECG, Temperature.
Preoxygenation should be started using facemask
with delivering of 100% oxygen.
Induction can be done by one of the IV induction
agents: Thiopentone, Etomidate, Propofol, Ketamine.

9. Induction cont..
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• Complications of IV induction:
1. Regurgitation and vomiting.
2. Intra-arterial injection.
3. Cardiovascular depression.
4. Respiratory depression.
5. Histamine release.
6. others, like pain on injection.

10. Positioning
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• After induction, the patient is placed on the
operating table in a position appropriate for the
proposed surgery.
• When positioning the patient, the technologist
should take into account surgical access, patient
safety, anesthetic technique, monitoring and
position of i.v. lines.

11. Positioning cont..
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• Here is the commonly used positions, each may have adverse
effects on skeletal, ventilatory, circulatory and neurological.
1. The lithotomy position may result in nerve damage
2. The lateral position may cause asymmetrical lung ventilation.
3. The prone position may cause abdominal compression.
4. The trendelenburg position may cause pressure on the
diaphragm.
5. The sitting position needs good support of the head.
6. The supine position may cause supine hypotension

12. Maintenance of GA
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• Maintenance means continuation of anesthesia.
• Maintenance can be achieved by :
A. Inhalational + spontaneous ventilation.
B. Inhalational + controlled ventilation.
C. Intravenous + spontaneous ventilation.
D. Intravenous + controlled ventilation.

13. Inhalational Anesthesia
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• Its suitable for superficial operations, minor procedures and
small operations that don't require muscle relaxants.
• MAC is the minimum alveolar concentration of an inhaled
anesthetic agent which prevents reflex movement in response
to surgical incision in 50% of subjects.
• The main advantage of inhalational anesthesia is rapid control
to deep anesthesia.
• The signs of inadequate depth of anesthesia are: Tachypnea,
Tachycardia, Hypertension and sweating.

14. Complications of Inhalational
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1. Airway obstruction.
2. Laryngeal spasm.
3. Bronchospasm.
4. Malignant hyperthermia.
5. Raised intracranial pressure.

15. Maintenance cont..
• Inhalational anesthesia can be delivered by face mask, laryngeal
mask airway (LMA) or by endotracheal tube (ETT).
• USE OF FACE MASK:
The face mask has many variants of type and size, the selection
of the correct fit is important to provide a gas-tight seal.
A mask with excessive dead space should be avoided in
pediatric age group.
Maintenance of the airway may be assisted further by the use of
Guedel airway.
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16. Maintenance cont..
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• Use of the laryngeal mask airway:
Indications:
1. To provide a clear airway with hands free
anesthetist.
2. To avoid intubation during spontaneous ventilation.
3. To assist intubation in case of difficulties.
Contraindications:
1. Full stomach patient.
2. Any possibilities of regurgitations
3. surgery in the pharynx

17. Maintenance cont..
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• Use of endotracheal intubation:
Indications:
1. secure clear airway.
2. Can be used in unusual positions.
3. Naso-tracheal tube can be used for head&neck
surgery.
4. Help suction of the respiratory system.
5. For thoracic surgeries.

18. Relaxant Anesthesia
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• Is an alternative to deep anesthesia with spontaneous
ventilation and volatile agents leading to multisystem
depression, the triad of sleep, suppression of reflexes
and muscle relaxation may be provided separately with
specific agents.
• Relaxant anesthesia provides muscle relaxation with light
level of anesthesia with less risk of cardiovascular
depression.
• Its appropriate for major abdominal, intraperitoneal,
thoracic or intracranial operations.

19. Assessment of Relaxant
Anesthesia
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A. Adequacy of Anesthesia.
Autonomic reflex activity with lacrimation, sweating,
tachycardia, hypertension or reflex movement in
response to surgery indicate “light anesthesia”.
B. Awareness during anesthesia.
The anesthetist should ensure that this possibility is
avoided by constant observation of the patient for
clinical signs of light anesthesia.

20. Assessment of Relaxant
Anesthesia cont..
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C. Adequacy of muscle relaxation.
We should observe return of muscle tone, any
abdominal movement or diaphragmatic or facial
movement.
An increase in airway pressure may indicate an
increase in muscle tone.
D. Adequacy of ventilation.
The clinical signs of inadequacy are tachycardia,
hypertension and increase in PaCo2.

21. Reversal of Relaxation
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• At the end of operation, residual neuromuscular
blockade is antagonized and spontaneous
ventilation established before the tracheal tube is
removed and the patient awakened.
• Reversal drug composed of ( Neostigmine 2.5 mg +
Atropine 1.2 mg) for adults.
• Resumption of spontaneous ventilation should
occur if normocapnic ventilation has been employed
and assured by monitoring on end tidal Co2.

22. Reversal of Relaxation cont.
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• In patients at risk of regurgitation and potential aspiration,
the lateral position is preferred.
Return of respiratory reflexes is significant by coughing and
resistance to the presence of the tracheal tube.
Tracheobroncheal suction via the tracheal tube is carried
out using suction catheter.
Pharyngeal suction is performed best under direct vision,
avoiding trauma to the pharyngeal mucosa, uvula or
epiglottis.
After extubation, the patient’s ability to maintain the airway
is ensured; Administration of oxygen is continued by face
mask.
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23. Complications of Extubation
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• Laryngeal spasm:
This may follow stimulation from extubation. Local
anesthetic spray to the larynx may block the reflex and
pharyngeal suction before extubation removes
secretions which may cause stimulation.
• Regurgitation / inhalation:
If case of emergency surgery the patient’s stomach
may be full, So aspiration by the nasogastric tube
should be performed before tracheal extubation to
remove gastric liquid.

24. Local Anesthesia
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• Local anesthetic drugs act by producing a reversible
block to the transmission of peripheral nerve
impulse.
• A reversible block may be produced also by
physical factors including pressure and cold.
• Many types of drug have local anesthetic actions
(e.g. B-blocker and anti-histamines). But all those
known and used as local anesthetics have
originated from cocaine.

25. Properties of Ideal LA
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• Potent.
Non-irritant.
No allergic reaction.
No systemic toxicity.
Reversible action.
Rapid onset of action.
Sufficient duration of action.
Stable in solutions.
Not expensive.
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26. Indications
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• For local Anesthesia.
• Treatment of ventricular arrhythmia.
• To decrease hemodynamic response to tracheal
intubation.
• Treatment of convulsions.

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