Pulse wave transit time (PWTT) increases due to decreased arterial vascular tone resulting from sympathetic blockade caused by regional anesthesia. Its oscillation (PWTT variability) also contains information on the interaction between autonomic nervous system and the cardiovascular system. The changes in PWTT and its variability have not been investigated in patients receiving interscalene brachial plexus block (ISBPB). It was hypothesized that ISBPB increases PWTT and reduces low frequency power of PWTT variability.
Study Type
OBSERVATIONAL
Enrollment
59
Using a linear ultrasound transducer connected to an ultrasound machine, the compactly arranged brachial plexus is visualized lateral to the pulsating subclavian artery. The transducer is moved cephalad to visualize the 5th to 8th cervical (C5 to C8) nerve roots located between the anterior and middle scalene muscles. Using an in-plane technique, a block needle is inserted close to a nerve root in a lateral-to-medial direction. The needle is moved to place 0.75% ropivacaine around each nerve root. The C8 nerve root is blocked first, and the C5 nerve root is blocked last. After blocking the four cervical nerve roots, ropivacaine is placed in the intermuscular plane between the sternocleidomastoid and scalene muscles to block the supraclavicular nerves. A total of 26 ml of 0.75% ropivacaine is used for the interscalene brachial plexus block (6 ml per nerve root and 2 ml for the supraclavicular nerves).
Daegu Catholic University Medical Center
Daegu, South Korea
Natural-log-transformed low frequency power of pulse wave transit time variability
Calculated by integrating the power spectra of pulse wave transit time variability between 0.04 and 0.15 Hz.
Time frame: Between 15 and 20 minutes after block needle insertion
Natural-log-transformed low frequency power of pulse wave transit time variability
Calculated by integrating the power spectra of pulse wave transit time variability between 0.04 and 0.15 Hz.
Time frame: During 5 minutes before the end of the acclimatization period
Natural-log-transformed low frequency power of pulse wave transit time variability
Calculated by integrating the power spectra of pulse wave transit time variability between 0.04 and 0.15 Hz.
Time frame: Between 5 and 10 minutes after block needle insertion
Natural-log-transformed high frequency power of pulse wave transit time variability
Calculated by integrating the power spectra of pulse wave transit time variability between 0.15 and 0.4 Hz.
Time frame: During 5 minutes before the end of the acclimatization period
Natural-log-transformed high frequency power of pulse wave transit time variability
Calculated by integrating the power spectra of pulse wave transit time variability between 0.15 and 0.4 Hz.
Time frame: Between 5 and 10 minutes after block needle insertion
Natural-log-transformed high frequency power of pulse wave transit time variability
Calculated by integrating the power spectra of pulse wave transit time variability between 0.15 and 0.4 Hz.
Time frame: Between 15 and 20 minutes after block needle insertion
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Pulse wave transit time
Time difference in milliseconds between the R peak of the electrocardiographic waveform and the peak of the 2nd-derivative photoplethysmographic waveform.
Time frame: During 5 minutes before the end of the acclimatization period
Pulse wave transit time
Time difference in milliseconds between the R peak of the electrocardiographic waveform and the peak of the 2nd-derivative photoplethysmographic waveform.
Time frame: Between 5 and 10 minutes after block needle insertion
Pulse wave transit time
Time difference in milliseconds between the R peak of the electrocardiographic waveform and the peak of the 2nd-derivative photoplethysmographic waveform.
Time frame: Between 15 and 20 minutes after block needle insertion
Sensory blockade
Assessed by grading the coldness with a 3-level scale consisting of 0 (no cold sensation), 1 (reduced cold sensation), and 2 (normal cold sensation) after applying an alcohol swab to the upper limb dermatomal areas innervated by the C5 to T1 nerve roots.
Time frame: 20 minutes after block needle insertion
Motor blockade
The muscle contraction power is rated as 0 (complete block), 1 (partial block), and 2 (no block) for shoulder abduction (axillary nerve), elbow flexion (musculocutaneous nerve), forearm supination (radial nerve), forearm pronation (median nerve), wrist extension (radial nerve), wrist flexion (median nerve), finger abduction (ulnar nerve), thumb abduction (radial nerve), thumb adduction (ulnar nerve), and thumb opposition (median nerve).
Time frame: 20 minutes after block needle insertion
Bilateral pupil diameters
Measured using a portable automated monocular infrared pupillometer (PLR-3000, NeurOptics Inc., Irvine, CA, the United States) at 30 Hz for 2 seconds.
Time frame: Within 1 minute after acclimatization
Bilateral pupil diameters
Measured using a portable automated monocular infrared pupillometer (PLR-3000, NeurOptics Inc., Irvine, CA, the United States) at 30 Hz for 2 seconds.
Time frame: 20 minutes after block needle insertion
Incidence of side effects related to interscalene brachial plexus block
Horner's syndrome, subjective dyspnea, and hoarseness
Time frame: 20 minutes after block needle insertion