Abstract ID: A22
Abstract Title: The Effect of Motor Activity on the Onset and Progression of Brachial Plexus Block with Bupivacaine: Preliminary Results
Authors: Langen K1, Candido K2, King M3, Marra G4
Loyola University Medical Center Maywood Illinois USA1, Loyola University Medical Center Maywood Illinois USA2, Loyola University Medical Center Maywood Illinois USA3, Loyola University Medical Center Maywood Illinois USA4
Poster Type: Either
ABSTRACT BODY
Introduction:
Interscalene brachial plexus blocks (ISB) are routinely performed preoperatively for arthroscopic shoulder surgeries using long acting local anesthetics such as bupivacaine, as a method of providing postoperative pain control. Several authors have investigated various methods of decreasing the latency of onset of neural blockade with limited success. Okasha et al (1) have shown that repetitive muscle contraction of the hand was effective in reducing the latency of onset of brachial plexus blocks by 60 percent when using lidocaine as the local anesthetic. It would be highly desirable if a simple intervention such as repetitive hand exercise could reduce the latency of onset of ISB with bupivacaine. The ability to decrease the latency of bupivacaine would make the use of this agent more efficient in a busy surgical practice.
Materials and Methods:
After IRB approval and informed consent, patients receiving an ISB as a component of anesthesia for arthroscopic shoulder surgery were enrolled in this study. Patients were randomly assigned into one of two groups. Patients in group I, the “control group,” were instructed to rest quietly immediately following the performance of the ISB. Patients in group II, the “muscular exercise group,” were instructed to rapidly and forcefully open and close both of their hands immediately following the completion of the ISB for 5 minutes. Hand grip strength and tolerance to transcutaneous electrical stimulation (TES) were used to quantify the degree of motor and sensory blockade. Measurements were taken at baseline and at 5 minute intervals following the ISB. Hand grip strength was measured by asking subjects to grip a hand dynamometer. Tolerance to transcutaneous electrical stimulation (TES) was used to quantitatively assess the depth of cutaneous analgesia. Electrodes were placed on the skin 2 cm apart on the lateral aspect of the upper arm at the mid humerus level. Using an EZStim Model ES 400 ® (Life-Tech, Houston, TX) nerve stimulator, TES was initially delivered at 5 mA in a 50 Hz continuous square wave pattern and increased in 5 mA increments until each subject described mild discomfort or until a maximum of 60 mA was attained.
Results:
Preliminary results (exercise group n=8, control group n=6) of our study do not show a difference in the latency of onset of ISB in either motor or sensory blockade. Results of tolerance to TES and changes in grip strength are reported in figures 1 and 2 respectively. Values reported are the mathematical mean and bars represent the standard deviation.
Discussion:
Preliminary results of our prospective, randomized study fail to demonstrate a decrease in the latency of onset of brachial plexus block with motor activity using bupivacaine, as has been previously described with lidocaine. These results question the postulated clinical usefulness of frequency dependent conduction blockade.
References:
1.Okasha AS. el-Attar AM. Soliman HL. Enhanced brachial plexus blockade. Effect of pain and muscular exercises on the efficiency of brachial plexus blockade. Anaesthesia. 43(4):327-9, 1988 Apr.
ATTACHED FILES
A22_Figure 1.tif
A22_Figure 2.tif
Reg Anesth Pain Med 2005; 30(3):A22