Bahareh Khatibi , MD 1 , Engy T. Said , MD 2 , Jacklynn F. Sztain , MD 3 , Amanda M. Monahan , MD 4 , Rodney A. Gabriel , MD 5 , Timothy J. Furnish , MD 6 , Johnathan T. Tran , BS 7 , Michael C. Donohue , PhD 8 , Brian M. Ilfeld , MD, MS 9 , Clinical Investigation
01 April 2018
It remains unknown whether continuous or scheduled intermittent bolus local anesthetic administration is preferable for transversus abdominis plane (TAP) catheters. We therefore tested the hypothesis that when using TAP catheters, providing local anesthetic in repeated bolus doses increases the cephalad-caudad cutaneous effects compared with a basal-only infusion.
Bilateral TAP catheters (posterior approach) were inserted in 24 healthy volunteers followed by ropivacaine 2 mg/mL administration for a total of 6 hours. The right side was randomly assigned to either a basal infusion (8 mL/h) or bolus doses (24 mL administered every 3 hours for a total of 2 bolus doses) in a double-masked manner. The left side received the alternate treatment. The primary endpoint was the extent of sensory deficit as measured by cool roller along the axillary line at Hour 6 (6 hours after the local anesthetic administration was initiated). Secondary endpoints included the extent of sensory deficit as measured by cool roller and Von Frey filaments along the axillary line and along a transverse line at the level of the anterior superior iliac spine at Hours 0–6.
While there were statistically significant differences between treatments within the earlier part of the administration period, by Hour 6 the difference in extent of sensory deficit to cold failed to reach statistical significance along the axillary line (mean=0.9 cm; SD=6.8; 95% CI −2.0, 3.8; p=0.515) and transverse line (mean=2.5 cm; SD=10.1; 95% CI −1.8, 6.8; p=0.244). While the difference between treatments was statistically significant at various early time points for the horizontal, vertical and estimated area measurements of both cold and mechanical pressure sensory deficits, no comparison remained statistically significant by Hour 6.
No evidence was found in this study involving healthy volunteers to support the hypothesis that changing the local anesthetic administration technique (continuous basal versus hourly bolus) when using ropivacaine 0.2% and TAP catheter at 8 mL/h and 24 mL every 3 hours significantly influences the cutaneous effects after 6 hours of administration. Additional research is required to determine whether changing variables (e.g., local anesthetic concentration, basal infusion rate, bolus dose volume and/or interval) would provide different results.