Effects of isoflurane anesthesia on cerebrovascular autoregulation in horses.

The research article investigates the effect of isoflurane anesthesia on the cerebrovascular autoregulation in horses. Through its study, it tests the hypothesis that isoflurane interferes with cerebrovascular autoregulation and whether an increased mean arterial blood pressure (MAP) would increase cerebral blood flow and intracranial pressure (ICP).

Research Methodology

• The study involved 6 healthy adult horses that served as subjects of the experiment.
• The horses were anesthetized with isoflurane at a constant end-tidal concentration that was sufficient to maintain MAP at 60 mm Hg.
• The facial, carotid, and dorsal metatarsal arteries were catheterized for blood sample collection and pressure measurements.
• A sub-arachnoid transducer was used to measure ICP.
• Fluorescent microspheres were injected through a left ventricular catheter during MAP conditions of 60 mm Hg, after which blood samples were collected.
• This process was repeated using different-colored microspheres at the same isoflurane concentration during MAP conditions of 80 and 100 mm Hg achieved with IV administration of dobutamine.
• After euthanasia, central nervous system tissue samples were obtained to quantify fluorescence and calculate blood flow.

Research Findings

• The research did not find any increase in ICP or blood flow in any of the brain tissues examined as a result of increased MAP.
• However, low blood flow was recorded for all tested brain regions except the pons and cerebellum.
• The study further noted a significantly decreased blood flow in the spinal cord at the highest MAP.

Conclusion

• The results concluded that healthy horses autoregulate blood flow in the CNS at moderate to deep planes of isoflurane anesthesia.
• However, the study points out that low blood flows in the brain and spinal cord of anesthetized horses may increase risks for hypoperfusion and neurologic injury.