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KMID : 0350519930460041571
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Journal of Catholic Medical College
1993 Volume.46 No. 4 p.1571 ~ p.1578
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Plasma Catecholamine and Vasopressin Concentration and Renin Activity to Hypotension Following Cervical Epidural Block in Rabbits
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Kim Kwang-Jum
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Abstract
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Many authors report that block of sympathetic activity, compromized vasopressin secretion and renin activity play a mafor role in hypotension during epidural block, particularly in high level. It has been known that compensatory ability for
stress
such
as hypotension is also impaired during epidural block.
Clinically, cervical epidural blokc has been widely used for pain control and anesthesia for high risk patients such as aged patients or cardiac patients because of its high carrdiovascular stability. It blocks the area above the upper chest and
does
not disturb renin-angiotensin system so that blood pressure would be well maintained. However, its exact mechanism of stability has not been well elucidated yet.
This study was designed to evaluate the three main factors of maintaining blood pressure ; catecholamine, vasopressin and renin activity.
Cannulations of both femoral arteries and left femoral vein were performed under anesthesia using pentothal sodium intravenously and ketamine intramuscularly.
Cervical epidural block was performed by using 1.5 ml of 0.25% bupivacaine through catheter inserted cephalad at T6-T7 interspace after awakening from anesthesia.
After stabilization of 1 hour in vital signs, plasma levels of catecholamines(norepinphrine NE, epinephrine EPI) were measured by high performance liquid chromatography and vasopressin (AVP) and plasma renin activity (PRA) were measured by
radioimmunoassay before epidural blokc (normal group), at 30 minutes after epidural block (control group) and at 5 minutes after bleeding (experimental group ; bleeding under epidural block), respectively. Bleeding was done 10 ml/kg from one
femoral
artery for 10 minutes. Blood pressure, heart rate, ECG and respiration rate were measured at 5-minute interval continuously.
@ES The results were as follows ;
@EN 1. Cervical epidural block (control grou) showed significant decrease in both plasma levels of NE and EPI from normal group of 1,035.8±388.2 pg/ml and 204.1±116.0 pg/ml to 492.0±17.0 pg/ml and 68.3±53.2 pg/ml, respectively (P<0.05).
Bleeding
(experimental group) did not show significant change of NE but increased plasma level of EPI (P<0.05) compared with control.
2. Cervical epidural block (control group) showed significant increase in PRA compared with normal group (P<0.05) and PRA showed addithonal increse during bleeding (experimental group) (P<0.05).
3. Plasma level of AVP in control group was increased by about 8 times of normal group (27.9±18.7 pg/ml) (P<0.05) and marked increase of AVP in experimental group (74.5±19.5 pg/ml) (P<0.05) was also observed compared with control group
(3.7±2.7
pg/ml).
4. Blood pressure was significantly decreased in control group (65.5±8.0 mmHg) compared with normal group (94.5±6.7 mmHg) (P<0.05) and in experimental group was also significantly decreased (43.5±2.1 mmHg) compared with control group
(P<0.05).
5. Heart rate was decreased by 3.1±5.0% in experimental group compared with control group, respectively (P<0.05). There was no significant change of respiration rate in control group compared with normal. but in experimental group significantly
increased compared with control group. Dysrhythmias or changes of ST segment on ECG were not observed.
These results showed that cervical epidural block would suppress in part sympathetic nervous system but not suppress renin activity and vasopressin system. Thus, compensatory mechanism against stress such as bleeding was relatively well
maintained.
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KEYWORD
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