Anaesthesia

Question 1

What is anaesthesia?

How does anaesthesia work?

Answer 1

• loss of sensation
• local/regional/general

Drugs that cause anaesthesia work by blocking the signals that pass along nerves to the brain. When drug wears off, normal sensations, including pain, are felt again.

Question 2

What is conscious sedation?

Answer 2

• drug produces a state of depression of CNS enabling treatment to be carried out, but during which verbal contact with pt is maintained throughout period of sedation
• drugs and techniques should carry a margin of safety wide enough to render loss of consciousness unlikely

Question 3

What are important points to consider in the medical history for anaesthesia?

What is malignant hyperthermia?

Answer 3

• past surgical and anaesthetic history
• reflux
• allergies - anaphylaxis
• medications/conditions
• airway
• bleeding disorders

Malignant hyperthermia: inherited disorder of skeletal muscle only triggered by anaesthetics

• abnormal accumulation of calcium in muscle cells leads to hypermetabolism, muscle rigidity and muscle breakdown –> anaesthetic emergency!!

Question 4

What are the characteristics of malignant hyperthermia?

What drug limits the MH process?

Answer 4

• tachycardia
• hypoxic - increase in O2 requirements
• temp increases, CO2 concentration increases

Only drug effective at limiting the MH process is dantrolene

• active cooling of pt is also done

Question 5

What monitoring takes place during anaesthesia?

Answer 5

• BP cuff, O2 saturation, canula
• benzodiazepines - pre-medication to reduce the amount of other agents required for anaesthesia
• propofol, thiopental, etomidate - inhalation drug to induce and maintain anaesthesia: usually administered in a mixture of oxygen and air or nitrous oxide

Question 6

What are the stages of anaesthesia?

What makes anaesthesia balanced?

Answer 6

Stage I - loss of consciousness

Stage II - excitement or delirium, coughing, vomiting, struggling

Stage III - stage of surgical anaesthesia - from onset of automatic respiration to respiratory paralysis, larungeal reflex lost, pupils dilate

Stage IV - cessation of respiration to death (overdose)

Balanced anaesthesia:

• anaesthesia, analgesia, muscle relaxation

Question 7

What is the purpose of muscle relaxants?

Name a short acting muscle relaxant:

Long acting:

Answer 7

Muscle relaxants - cause muscle paralysis allowing intubation and surgical access to body cavities

Short acting: suxamethonium

Long acting (30 mins or more): atracurium/rocuronium