Longnecker's Anesthesiology > Part 4. Managing Anesthesia Care > Section C. Anesthesia Drugs and Drug Delivery Systems > Chapter 37. Pharmacology of Inhalational Anesthetics Stuart A. Forman, MD, PhD, and George A. Mashour, MD, PhD

Key Points

"1. Inhaled anesthetics are delivered and eliminated via pulmonary ventilation. The most useful definition of "dose" for these drugs is the partial pressure in alveolar gases, which is readily monitored in end-tidal expired gases.

2. Some early inhaled anesthetic alkanes and ethers were flammable. Halogenation reduces flammability. Fluorination tends to decrease metabolic breakdown.

3. All halogenated anesthetics break down, releasing carbon monoxide and heat when they contact desiccated alkaline chemicals, such as those in common carbon dioxide (CO₂) adsorbents. Potential harm to patients from this breakdown can be prevented by proper use and maintenance of anesthesia equipment and by use of less alkaline CO₂ adsorbents.

4. Biophysical properties of inhaled anesthetics, including blood/gas partition coefficients and tissue–blood partition coefficients, determine the speed of drug uptake, distribution among tissue groups, and elimination.

5. Low blood solubility of inhaled anesthetics is associated with rapid uptake and elimination via the lungs.

6. The rate at which the alveolar anesthetic concentration (FA or P_alv) approaches the inspired (circuit) concentration (FI or P_circ) depends on minute alveolar ventilation (increased ventilation accelerates FA/FI), cardiac output (increased..."