Conscious stages achieved by anaesthesia

Three parameters must be achieved to perform a surgery.

1. Loss of consciousness
2. Loss of pain
3. Muscle relaxation

When considering loss of consciousness, there are several stages. Each stage can be achieved by anaesthetic agents. The aim of anaesthetic agents is to achieve the desired conscious stage appropriate for that surgery.

The conscious stages are listed below.

Stage 1 – In this stage the person is awake and aware of the surrounding environment and stimuli. 

Stage 2 – In this stage the person is unconscious but he/she is in a highly stimulated state. It is indicated by high blood pressure, increased heart rate etc. Due to these reasons this stage is not appropriate for surgery, because surgery needs a calm patient for optimum outcome.

Stage 3 – This is the stage achieved by anaesthesia. It has 3 levels.

• Level 1 – This level is a little close to stage 2 and therefore, with a little high blood pressure and heart rate. Therefore this stage is not used for surgery.
• Level 2 – This is the level suitable for most of the surgeries.
• Level 3 – This is a deeper level of loss of consciousness and therefore more closer to death. This level is used for surgeries which need highly suppressed nervous system; surgeries like neurosurgeries.

Stage 4 - Death

Fundamentals of Anaesthesia (Cambridge Medicine)