A Comparative Cadaver Study of Automated Pulsed Bolus Versus Continuous Basal Infusion on Distribution of Dye in a Interscalene Nerve Block Catheter
The purpose of this study is to determine if the spread of contrast dye is greater in a continuous basal infusion or automated pulsed dosing in an interscalene catheter.
After IRB approval, a fresh cadaver was studied. The cadaver was placed in the supine position and bilateral interscalene catheters were placed. Using a linear probe (15-6 MHz) for in-plane ultrasound guidance (SonoSite Export), bilateral 5 Fr. catheters over an 18Ga. needle (Fascile® Continuous Peripheral Nerve Block, Solo-Dex Inc. Boulder, CO) were placed between the C5 and C6 nerve roots and secured. The cadaver was transported and placed on a computer tomography (CT) scanner table and not moved after the infusions were started. The two catheters were attached to an infusion of iohexol dye (Omnipaque, GE Healthcare Ireland, Cork, Ireland) diluted 1:10, one side was assigned to continuous infusion of 5 mL/h and the contralateral side an automated 5mL hourly boluses (PIBPCA, ambit, Summit Medical Products, Sandy, Utah). Separate CT scans were obtained after 10, 15 and 20 milliliters were infused.
The distribution and spread of the dye in the interscalene space is shown in Figure 1 and 2. The pulsed side demonstrated greater diffusion and spread of the dye. No leakage of dye was observed from any of the catheters.
Pulsed dosing of contrast dye had a greater distribution than continuous infusion in an interscalene nerve block catheter. In a cadaver model there is no absorption of dye in comparison to a live model. Pulse dosing at a rate of 5 cc/hour, which is 1 cc per 12 minutes, may greatly affect the spread of local anesthesia in patients. Clinical studies are needed to determine the efficacy of pulsed dosing.