Anesthesia controls pain during surgery or other medical procedures. It includes using medicines, and sometimes close monitoring, to keep you comfortable. It can also help control breathing, blood pressure, blood flow, and heart rate and rhythm, when needed. Anesthetics are divided into two classes:
- Those that suspend sensation in the whole body – General anesthesia
- Those that suspend sensation in certain parts of the body – local, regional, epidural or spinal anesthesia
This type of anesthesia promotes total loss of consciousness and sensation. General anesthesia is commonly achieved when the anesthetic is inhaled or administered intravenously. It affects the brain as well as the entire body. Types of general anesthesia administration:
- Volatile liquid anesthetics – this type of anesthetic produces anesthesia when their vapors are inhaled. Included in this group are the following:
- Halothane (Fluothane)
- Methoxyflurane (Penthrane)
- Enflurane (Ethrane)
- Isoflurane (Forane)
- Gas Anesthetics – anesthetics administered by inhalation and are ALWAYS combined with oxygen. Included in this group are the following:
- Nitrous Oxide
Stages of General Administration
Anesthesia consists of four stages, each of which presents a definite group of signs and symptoms.
Stage I: Onset or Induction or Beginning anesthesia. This stage extends from the administration of anesthesia to the time of loss of consciousness. The patient may have a ringing, roaring or buzzing in the ears and though still conscious, is aware of being unable to move the extremities easily. Low voices or minor sounds appear distressingly loud and unreal during this stage.
Stage II: Excitement or Delirium. Stage II extends from the time of loss of consciousness to the time of loss of lid reflex. This stage is characterized by struggling, shouting, talking, singing, laughing or even crying. However, these things may be avoided if the anesthetic is administered smoothly and quickly. The pupils become dilated but contract if exposed to light. Pulse rate is rapid and respirations are irregular.
Stage III: Surgical Anesthesia. This stage extends from the loss of lid reflex to the loss of most reflexes. It is reached by continued administration of the vapor or gas. The patient now is unconscious and is lying quietly on the table. Respirations are regular and the pulse rate is normal.
Stage IV: Overdosage or Medullary or Stage of Danger. This stage is reached when too much anesthesia has been administered. It is characterized by respiratory or cardiac depression or arrest. Respirations become shallow, the pulse is weak and thread and the pupils are widely dilated and no longer contract when exposed to light. Cyanosis develops afterwards and death follows rapidly unless prompt action is taken. To prevent death, immediate discontinuation of anesthetic should be done and respiratory and circulatory support is necessary.