Inhaled GAs

Question 1

What is the general mechanism of GAs?

Answer 1

GAs ENHANCE INHIBITORY postsynapic channel activity (GABAA and glycine receptors)

GAs INHIBIT EXCITATORY synaptic channel activity (Nicotinic acetylcholine and glutamate receptors)

Question 2

What are the inhaled GAs?

Answer 2

Non halogenated - Nitric Oxide

Volatile Halogenated Agents: Isoflurane, Desflurane, Sevoflurane

Question 3

What are the MOA and characteristics adverse effects of Nitric Oxide?

Answer 3

MOA: NMDA Antagonist (non-competative)

Characteristics: weak anesthetically
Good analgesic
Safest Inhalation anesthsia (colorless &
Odorless

NO TOXIC EFFECTS on Heart, Liver & Kidney;
CAUTION: Can cause DIFFUSIONAL HYPOXIA;
Abuse can lead to neuropathies and megaloblastic anemia – due to oxidation of cobalt co-factor in VitB12

Question 4

What cis the adverse effect of Volatile GAs on patients with Malignant Hyperthermia?

Answer 4

LIFE-THREATENING --- due to massive release of 
  intracellular Ca2+ in skeletal muscle from 
  sarcoplasmic reticulum (SR) – 

TX: Dantrolene IV

Question 5

What is the clinical use, MOA, Blood/gas coefficient advantages and adverse effects of Isoflurane?

Answer 5

Clinical Use: Neurosurgery (less ICP and cerebral blood flow)

MOA: Moderate analgesic and good skeletal muscle relaxant activity

Blood/gas coefficient: 1.4 — MODERATE induction (onset) and recovery

Advantage: CARDIAC OUTPUT is maintained; DOES NOT sensitize heart to catecholamines; NON-TOXIC metabolites

Adverse Effects: BRONCHODILATOR AND IRRITANT, Pungent odor   
Reduce BP (use with N2O and O2)
increase HR

Question 6

What is the clinical use, MOA, blood/gas coefficient advantages and adverse effects of Desflurane?

Answer 6

Clinical Use: Outpatient Surgery (rapid recovery)

MOA: Directly relaxes smooth muscle

Blood/gas coefficients: the lowest .42 (very rapid induction and recovery)

Advantage: CARDIAC OUTPUT is maintained; DOES NOT sensitize heart to catecholamines; NON-TOXIC metabolites

Adverse Effects: Like isoflurane, it has PUNGENT ODOR (Lung irritant); Reduce BP (Reduce by N2O), Increase HR

Question 7

What is the clinical use MOA, blood/gas coefficient, advantages and adverse effects of Sevoflurane?

Answer 7

Clinical Use: Inpatient & Outpatient Surgery, directly

MOA: Directly Relaxes smooth muscle

Blood gas portion coefficient: LOW 0.69

Advantage: PLEASANT ODOR – NON-IRRITATING (pediatric patients)

Adverse Effects: Reacts with SODA LIME (absorbs exhaled CO2)
IGNITE OR EXPLODE —
NEPHROTOXIC metabolite COMPOUND A;
epileptogenic anesthetic