Epidural clonidine does not decrease blood pressure or spinal cord blood flow in awake sheep

Area of Science:

• Anesthesiology
• Pharmacology
• Neuroscience

Background:

• Epidural clonidine shows antinociceptive and non-neurotoxic potential in preliminary studies.
• However, clonidine's vasoconstrictive properties raise concerns about spinal cord blood flow, as seen in anesthetized pigs.

Purpose of the Study:

• To investigate the effects of epidural clonidine on spinal cord blood flow in awake animals.
• To assess potential cardiovascular and spinal cord ischemic effects of epidural clonidine administration.

Main Methods:

• Adult sheep (N=13) were instrumented with arterial, venous, pulmonary, and left ventricular catheters.
• Epidural injections of saline (N=6) or clonidine (750 micrograms, N=7) were administered.
• Spinal cord blood flow, renal blood flow, cardiovascular parameters, and blood gases were measured using radioactive microspheres and other monitoring techniques.

Main Results:

• Epidural saline had no significant effect on measured variables.
• Clonidine caused transient decreases in heart rate and arterial PO2, and a later increase in body temperature.
• Importantly, epidural clonidine did not decrease overall spinal cord blood flow, with a transient increase observed in mid-thoracic flow at 45 minutes.

Conclusions:

• Epidural clonidine administration in awake sheep does not lead to global spinal cord ischemia.
• The study suggests that epidural clonidine does not induce dangerous cardiovascular depression in this model.
• Findings support the potential safety of epidural clonidine regarding spinal cord perfusion in awake subjects.