Rat brain osmolality during barbiturate anesthesia and global brain ischemia

Area of Science:

• Neuroscience
• Physiology
• Pharmacology

Background:

• Ischemic brain damage can be mitigated by barbiturate therapy post-insult.
• Brain hyperosmolality during ischemia may exacerbate brain edema after circulation is restored.

Purpose of the Study:

• To investigate changes in brain osmolality during ischemia.
• To evaluate the effect of barbiturate anesthetics on brain osmolality during ischemic conditions.

Main Methods:

• Measurement of whole and regional brain osmolality in rats subjected to decapitation ischemia.
• Comparison between unanesthetized and pentobarbital-anesthetized rats.
• Osmolality measurements were taken for up to 2 hours post-ischemia.

Main Results:

• Normal (non-ischemic) brain osmolality was higher in pentobarbital-anesthetized rats (319 mOsm/L) than in unanesthetized rats (307 mOsm/L).
• The rate of increase in whole brain osmolality was 60% slower in the first hour of ischemia in anesthetized rats.
• Regional brain osmolality increased by a maximum of 32 mOsm/L in anesthetized rats versus 45 mOsm/L in unanesthetized rats.

Conclusions:

• Pentobarbital anesthesia significantly attenuates the rate and magnitude of brain osmolality increase during ischemia.
• The potential for edema formation, indicated by the percent change and rapidity of osmolality increase, is greater in unanesthetized rats.
• Barbiturate anesthesia demonstrates a protective effect against ischemia-induced brain hyperosmolality and potential edema.