Changes in pulse wave transit time variability after interscalene brachial plexus block placement

Area of Science:

• Anesthesiology
• Cardiovascular Physiology
• Autonomic Nervous System Research

Background:

• Pulse wave transit time (PWTT) reflects vascular tone and is influenced by autonomic nervous system activity.
• Regional anesthesia, such as interscalene brachial plexus block (ISBPB), can cause sympathetic blockade, potentially altering cardiovascular parameters.
• PWTT variability, particularly low-frequency power (LF), is linked to autonomic nervous system function.

Purpose of the Study:

• To investigate the effect of interscalene brachial plexus block (ISBPB) on pulse wave transit time (PWTT).
• To determine if ISBPB alters the low-frequency power (LF) of PWTT variability.
• To explore the relationship between ISBPB and autonomic nervous system regulation via cardiovascular parameters.

Main Methods:

• Fifty-six patients undergoing ISBPB were analyzed.
• PWTT was measured as the interval between ECG R-peak and the second-derivative photoplethysmography peak.
• Low-frequency power (LF) of PWTT variability was calculated using fast Fourier transform analysis.

Main Results:

• PWTT significantly increased post-ISBPB compared to baseline (P < 0.001).
• The natural log-transformed LF (lnLF) of PWTT variability significantly decreased post-ISBPB (P < 0.01).
• Both PWTT and lnLF changes were observed between 5-10 and 15-20 minutes after block needle insertion.

Conclusions:

• ISBPB administration leads to a significant increase in PWTT.
• A significant reduction in the low-frequency power of PWTT variability was observed following ISBPB.
• These findings suggest that ISBPB-induced sympathectomy influences cardiovascular autonomic regulation.