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Regional intravascular sympathetic (RIS) block with guanethidine (Ismelin)
The Netherlands Journal of Surgery
|January 1, 1980
Summary
Regional intravascular sympathetic (RIS) block using guanethidine in rabbit ears demonstrated rapid tissue binding, reducing systemic effects. This method effectively prevented vasoconstriction and proved relatively safe for potential human application.
Area of Science:
- Pharmacology
- Autonomic Nervous System
- Vascular Biology
Background:
- Regional intravascular sympathetic (RIS) block is a technique to target sympathetic nerves locally.
- Guanethidine is a sympatholytic agent with potential applications in regional blockade.
- Understanding the pharmacokinetics and efficacy of RIS block is crucial for its clinical translation.
Purpose of the Study:
- To investigate the dose-effect relationship of guanethidine administered via RIS block in rabbit ears.
- To evaluate the duration and efficacy of RIS block in preventing sympathetic-mediated vasoconstriction.
- To assess the safety profile of RIS block by comparing systemic effects with intravenous administration.
Main Methods:
- Regional intravascular sympathetic (RIS) block was induced in rabbit ears using intra-arterial guanethidine with tourniquet occlusion.
- Mean arterial blood pressure was monitored after tourniquet release at 30 seconds and 10 minutes post-injection.
- Vasoconstriction response to cold provocation was assessed in the treated ear.
- The duration of the block and the effect of repeat administration were studied.
Main Results:
- RIS block significantly reduced systemic effects of guanethidine compared to intravenous injection, with 64% reduction after 30s occlusion and 80% after 10min.
- Vasoconstriction during cold provocation was abolished in the treated ear, maintaining high skin temperature.
- The block duration ranged from 3 days (0.625 mg) to 5 days (2.5 and 10 mg).
- Repeat blockade within 5 days was less effective, but efficacy was restored after three weeks.
Conclusions:
- Guanethidine administered via RIS block exhibits rapid and non-specific tissue binding, minimizing immediate systemic exposure.
- RIS block effectively inhibits sympathetic-mediated vasoconstriction, as evidenced by sustained high skin temperature.
- The prolonged duration and reduced systemic effects suggest RIS block is a potentially safe and effective method for regional sympathetic blockade.