General Anaesthesia Mechanism

General Anaesthesia

• General anaesthesia is a state of controlled unconsciousness, amnesia, and immobility, with a lack of response to surgical stimuli.
• The ideal anaesthetic agent should have a rapid onset and offset of action, be easy to administer, and have minimal side effects.

Mechanism of Action

• General anaesthetics act on the spinal cord and brain, altering neuronal function and synaptic transmission.
• They influence the activity of ion channels, neurotransmitters, and receptors, leading to a decrease in neural activity.

Stages of Anaesthesia

• Stage 1: Anaesthesia is induced, and the patient becomes disoriented and confused.
• Stage 2: The patient becomes unconscious and loses reflexes, but still responds to painful stimuli.
• Stage 3: Surgical anaesthesia, characterized by unconsciousness, amnesia, and immobility.
• Stage 4: Medullary paralysis, a state of deep anaesthesia, where the patient is unresponsive and may experience respiratory depression.

Induction of Anaesthesia

• Induction agents, such as propofol, etomidate, and ketamine, are used to induce anaesthesia.
• The choice of induction agent depends on the patient's condition, the type of surgery, and the anaesthetist's preference.

Maintenance of Anaesthesia

• Maintenance agents, such as halothane, isoflurane, and sevoflurane, are used to maintain anaesthesia.
• The minimum alveolar concentration (MAC) is the concentration of anaesthetic required to prevent movement in response to surgical stimuli.

Side Effects and Complications

• Respiratory depression, cardiovascular depression, and allergic reactions are potential side effects of general anaesthesia.
• Malignant hyperthermia is a rare but life-threatening complication of general anaesthesia.