Longnecker's Anesthesiology > Part 4. Managing Anesthesia Care > Section C. Anesthesia Drugs and Drug Delivery Systems > Chapter 40. Pharmacology of Intravenous Anesthetics Mark Dershwitz, MD, PhD, and Carl E. Rosow, MD, PhD

Key Points

"1. Thiopental decreases cerebral metabolic rate for oxygen and cerebral blood flow. By causing vasoconstriction of CNS blood vessels, thiopental also significantly decreases intracranial pressure.

2. When thiopental is given in advance of a planned decrease or interruption in cerebral perfusion, the likelihood or severity of CNS damage appears to be reduced.

3. Thiopental produces a dose-dependent decrease in ventilatory drive. It causes a decreased tidal volume and minute ventilation and an increased PaCO₂. The ventilatory depressant effect of thiopental is exaggerated in patients with underlying chronic obstructive pulmonary disease (COPD).

4. Thiopental has a direct effect on the heart by decreasing contractility, leading to a decrease in cardiac output. It also has a direct effect on both systemic arteries and veins causing vasodilatation.

5. Coexisting factors, such as previous premedication (e.g., benzodiazepines and/or opioids), advanced age, or presence of concurrent disease (e.g., cardiac dysfunction, COPD, hypovolemia) will decrease the required dose of thiopental to produce unconsciousness. Patients with acquired tolerance because of chronic use of barbiturates or cross-tolerance to benzodiazepines, anticonvulsants, or alcohol may require higher doses of thiopental to produce unconsciousness.

6. The CNS effects..."