Title 21. GENERAL ANESTHETICS.pdf ✅

PHARMD GURU Page 1 General Anesthetics refer to drug-induced reversible loss of consciousness and all sensations. The features of GA are as follows: 1. Reversible loss of consciousness. 2. Reversible loss of sensation. 3. Analgesia and amnesia. 4. Muscle relaxation and abolition of reflexes. There is no single anaesthetic agent that can produce all the above effects. Hence, anaesthetic protocol includes: 1. Premedication. 2. Induction of anaesthesia (e.g. propofol). 3. Maintenance of anaesthesia (e.g. N2O " isoflurane). 4. Skeletal muscle relaxation. 5. Analgesia – as premedication, during and after the operation. 6. Use of other drugs:  To reverse neuromuscular blockade.  To reverse the residual effects of opioids (naloxone) and BZDs (flumazenil). Minimal alveolar concentration (MAC) is the minimum concentration of an anaesthetic in alveoli required to produce immobility in response to a painful stimulus in 50% patients. It indicates the potency of inhalational general anaesthetics (N2O > 100%, halothane 0.75%). MECHANISM OF ACTION OF GENERAL ANAESTHETICS: The main site of action of anaesthetics is reticular formation, which normally maintains a state of consciousness. Most anaesthetics decrease transmission in reticular formation by enhancing the activity of inhibitory transmitters like GABA (e.g. BZDs, barbiturates and propofol) and blocking the activity of excitatory transmitters (e.g. blockade of N-methyl-D-aspartate [NMDA] glutamate receptors by ketamine and nitrous oxide). GENERAL ANESTHETICS