The catheter-over-needle assembly offers greater stability and less leakage compared with the traditional counterpart in continuous interscalene nerve blocks: a randomized patient-blinded study

Abstract

To the Editor, Continuous peripheral nerve blocks are susceptible to various complications, including leakage from the catheter insertion site which increases the risk of leakage of the bolus of injectate. This has the potential to disrupt the adhesive dressing and may further compromise the sterility of the surgical field if leakage occurs during the operation. Continuous interscalene brachial plexus blocks are commonly administered for pain control following shoulder and upper arm surgery. A prior study of complications of continuous interscalene analgesia showed a 9.3% incidence of leakage at the catheter site. We conducted a prospective randomized study to test the hypothesis that interscalene catheter-over-needle (CON) assemblies are clinically less prone to leakage at the insertion site compared with conventional catheterthrough-needle (CTN) counterparts. The primary outcome of the study was leakage from the catheter insertion site. Secondary outcomes were block performance time (the time from the initial skin puncture to first application of Tegaderm dressing) and pain scores in recovery and at 24 and 48 hr post-surgery. An 11-point visual analogue scale in which 0 indicated ‘‘no pain’’ and 10 indicated ‘‘worst pain imaginable’’ was used to record pain scores. The study was conducted from May 2012 to September 2012 at the University of Alberta Hospital. Following approval from the University of Alberta Health Research Ethics Board (January 2012) and informed written consent, adult patients admitted for shoulder surgery or surgery of the proximal humerus were randomly assigned using sealed envelopes to the CON (catheter-over-needle: study) or CTN (catheter-through-needle: control) group. Patients were blinded to the allocation, as was a member of the research team who collected follow-up data. Ultrasound-guided interscalene brachial plexus blocks using the CTN and CON methods were performed as previously described. All blocks were performed by staff regional anesthesiologists or by supervised regional anesthesia trainees. After insertion of the catheter, general anesthetic was administered to patients in both groups. A nerve block catheter remained in each of the patients in both groups throughout the operation and in the postoperative period with local anesthetic infusion with bolus dose for two to three days. Ten patients, six in the CON group and four in the CTN group, were approached and consented to participate in the trial. After the fourth CTN patient, the study was terminated at the request of our surgical colleagues (see below). None (0/6) of the CON patients experienced leakage around the catheter, and none required catheter remanipulation or fortification during the perioperative period (Table). Based on the ‘‘rule of three’’, the 95% confidence interval for the occurrence of leakage in CON patients was 0 to 0.5. In contrast, all CTN patients (4/4) experienced leakage around the perineural catheter during the perioperative period. One CTN catheter migrated out on postoperative day one, and two CTN catheters required fortification with gauze to address leakage. One CTN catheter was removed just before surgery due to excessive leakage; this case has been described previously. Following this case, the study had to be terminated earlier than anticipated at the surgeon’s request due to ClinicalTrials.gov Identifier: NCT01522053.