Sustained complete autonomic blockade

Area of Science:

• Physiology
• Pharmacology

Background:

• The autonomic nervous system regulates critical physiological functions.
• Understanding the effects of complete autonomic blockade is crucial for physiological research.

Purpose of the Study:

• To investigate the physiological consequences of complete autonomic blockade in anesthetized animals.
• To determine the reversibility and lethality of autonomic blockade.

Main Methods:

• Induction of a 3-hour complete autonomic blockade using trimetaphan camphorsulphonate and atropine in sheep and dogs.
• Monitoring of circulatory, respiratory, and metabolic parameters for 24 hours or until death.
• Administration of trimetaphan alone, or in combination with dopamine or hypertensin during blockade, for comparison.

Main Results:

• Complete autonomic blockade resulted in sustained hypotension and irreversible shock, leading to death within hours of blockade termination.
• The shock observed was not associated with typical respiratory or metabolic signs of circulatory failure.
• Trimetaphan alone was well-tolerated.
• Co-administration of dopamine or hypertensin during blockade halved the mortality rate, but survivors remained hypotensive.

Conclusions:

• Complete autonomic blockade induces a unique form of fatal shock, independent of typical circulatory failure consequences.
• Autonomic blockade requires careful consideration due to its severe and potentially irreversible hypotensive effects.
• Vasopressor support can mitigate mortality but does not fully resolve hypotension post-blockade.