A/23. Inhalational anesthetics.

Question 1

Drugs need to know in this topic

Answer 1

nitrous oxide
isoflurane
desflurane
sevoflurane

Question 2

General anesthesia is a state characterized by

Answer 2

∙Unconsciousness
∙Analgesia
∙Loss of memory
∙SKM relaxation
∙loss of reflexes(sensory,
vegetative)

Question 3

Signs & Stages of Anesthesia

Answer 3

Stage I. Analgesia: reflexes still presennt

Stage II. Excitation: Patient appears to be delirious and excited (↓inhibitory neuron)
(Unconscious)

Stage III. Tolerance: Surgical anesthesia (no reflex), regular breathing

Stage IV. Asphyxia: Respiratory and vasomotor center↓
(medullary
depression)

(Conscious)

Question 4

General (balanced) anesthesia protocol – Stages

Answer 4

I. Induction

1. IV anesthetics → produce unconsciousness within 30-40 seconds after injection
2. At that time, additional inhalation and/or IV drugs comprising the selected anesthetic combination are given to produce the
   desired depth of surgical anesthesia
3. IV skeletal muscle relaxant (rocuronium, vecuronium, succinylcholine) → facilitate intubation and muscle relaxation

II. Maintenance

1. Continuous administration of volatile anesthetics, which offer good control over the depth of anesthesia
2. Opioids (fentanyl) are often used for pain relief along with inhalation agents
3. Monitoring of vital signs – the standard method of assessing depth of anesthesia during surgery

III. Recovery

Question 5

Mechanisms of action – general anesthetics

Answer 5

• *1. Increase the threshold for firing of CNS neurons
  2. Facilitate GABA-mediated inhibition at GABAA receptors
  3. Inhibits central glutamate receptors (NMDA receptors)
  4. Inhibit central nicotinic Ach receptors**

Question 6

Minimum alveolar anesthetic concentration(MAC)

Answer 6

The index of potency(ED50): the alveolar conc of anesthetic that is required
to produce immobility in 50% of patients subjected to a surgical stimuli
-More lipid-soluble anesthetic ->the lower the MAC->the greater the
potency

Question 7

Nitrous oxide

Answer 7

Induction
Maintenance

MAC >100

Sol 0.49

1. Risk of spontaneous abortion (may trigger uterine contraction)
   2.Potential drug of abuse (‘laughing gas’)
   3.Diffusional hypoxia (occurs when nitrous oxide diffuses out of the blood in
   large volumes → dilutes oxygen in the alveoli → reducing alveolar oxygen
   tension → hypoxia)
2. Second gas effect (increased concentration of a second agent, due to the
   rapid diffusion of N2O in the alveoli)

Question 8

Desflurane

Answer 8

Maintanance

Fast induction and recovery

Respiratory irritation

Question 9

Sevoflurane

Answer 9

Induction
Maintenance

Most commonly used

metabolic rate is relatively high->possible
nephrotoxic metabolite

Question 10

Isoflurane

Answer 10

Maintenance

is preferred in neurosurgery

1. Peripheral vasodilation
2. Sensitizes the myocardium to catecholamines (arrhythmias)
3. Respiratory irritation

CI: pt with angina