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Intrathecal clonidine in obstetrics: sheep studies
1Department of Anesthesia, Wake Forest University Medical Center, Winston-Salem, North Carolina 27103.
Anesthesiology
|April 1, 1990
Summary
Intrathecal clonidine affects maternal blood pressure biphasically and decreases heart rate in ewes. High doses cause fetal hypoxemia and hypertension, limiting obstetric use.
Area of Science:
- Anesthesiology
- Pharmacology
- Obstetrics
Background:
- Intrathecal clonidine is used with local anesthetics or given accidentally during epidural procedures.
- Understanding clonidine's effects on maternal and fetal physiology is crucial for obstetric safety.
Purpose of the Study:
- To investigate the acute maternal and fetal effects of intrathecal clonidine administration in near-term ewes.
Main Methods:
- Nine chronically prepared ewes received cumulative intrathecal doses of clonidine (100-1500 micrograms).
- Maternal and fetal vital signs, blood gases, glucose, and cortisol were monitored.
- Intrathecal saline served as a control.
Main Results:
- Clonidine caused a biphasic maternal blood pressure response and dose-dependent decreases in maternal and fetal heart rate.
- The highest dose (1500 micrograms) led to maternal and fetal hypoxemia, fetal hypertension, and bradycardia.
- Maternal and fetal serum glucose increased, but cortisol levels remained unchanged.
Conclusions:
- While lower doses of intrathecal clonidine may enhance spinal anesthesia, higher doses (>10 micrograms/kg) can cause significant fetal bradycardia and hypoxemia.
- These findings suggest caution regarding the use of large doses of intrathecal clonidine in obstetric settings.
- Observed hypoxemia and hyperglycemia appear specific to sheep models.