General Anesthesia
General Anesthesia Pharmacology
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Intravenous Anesthetic Agents
Steps of GA
- Induction (hypnotic, analgesia, muscle relaxant)
- Maintenance
- Recovery (reversal)
Types of Induction of General Anesthesia
- Intravenous
- Inhalational
Physiological Changes During General Anesthesia
- Depress ventilatory control, depress ventilation and muscle movement, leading to hypercapnia and hypoxemia.
- Loss of airway reflex and gag response because of CNS depression, which may lead to aspiration of stomach contents.
- Patient needs immediate support of his airway and start controlled ventilation.
- Anesthesia agent leads to depress myocardial contractility and rate, leading to hypotension and organ hypoperfusion.
- It leads to either direct or indirect SVR reduction, which also leads to hypotension and organ injury.
- Patient will not move, this may lead to body injury if not monitored and protected by anesthesiologist during surgery.
Risks (Complications) of GA
Common Risks to General Anesthesia
- Sore throat due to gas or tube used for breathing may notice difficulty in speaking but improves with time.
- Temporary pain in the muscle.
- Hypothermia for preterm and newborns leading to a drop in blood circulation and respiratory.
- The risk of apnea in preterm infants aged less than 60 weeks, which requires the need to enter ICU.
Uncommon Risks of General Anesthesia / Sedation
- Awareness of the operating room activity during surgery such as caesarean section, cardiac operations.
- Eye contact may be accompanied by pain and may need medical treatment.
- Damage to teeth, lips, and tongue.
- Memory dysfunction.
Rare Risks of General Anesthesia That May Cause Brain Damage, Neurological Disability or Death
- Airway obstruction that cannot be controlled quickly and difficulty intubation, leading to severe lack of oxygen.
- Pulmonary aspiration causing pneumonia, hypoxia, and death. Risk is more with obesity and in pregnant women and in non-fasting patients.
- Severe allergic reactions to anesthetics and other medications may cause difficulty breathing, skin rashes, hypotension, and cardiac arrest.
Risks increase with elderly patients, premature infants, and children under one year of age who suffer from chronic diseases such as heart disease, chest, arteries, pressure, diabetes, liver, and kidney disease, smokers, and obesity.
(ASA) Defines of (Level of Sedation / Analgesia)
| Description | Minimal Sedation | Moderate Sedation / Analgesia | Deep Sedation / Analgesia | General Anesthesia |
|---|---|---|---|---|
| Responsiveness | Normal response to verbal stimulation | Purposeful response to verbal or tactile stimulation | Purposeful response following repeated or painful stimulation | Unarousable even with painful stimulus |
| Airway | Unaffected | No intervention required | Intervention may be required | Intervention often required |
| Spontaneous Ventilation | Unaffected | Adequate | May be inadequate | Frequently inadequate |
| Cardiovascular | Unaffected | Usually maintained | Usually maintained | May be impaired |