A New Measure for Monitoring Intraoperative Somatosensory Evoked Potentials

ObjectiveTo propose a new measure for effective monitoring of intraoperative somatosensory evoked potentials (SEP) and to validate the feasibility of this measure for evoked potentials (EP) and single trials with a retrospective data analysis study.MethodsThe proposed new measure (hereafter, a slope-measure) was defined as the relative slope of the amplitude and latency at each EP peak compared to the baseline value, which is sensitive to the change in the amplitude and latency simultaneously. We used the slope-measure for EP and single trials and compared the significant change detection time with that of the conventional peak-to-peak method. When applied to single trials, each single trial signal was processed with optimal filters before using the slope-measure. In this retrospective data analysis, 7 patients who underwent cerebral aneurysm clipping surgery for unruptured aneurysm middle cerebral artery (MCA) bifurcation were included.ResultsWe found that this simple slope-measure has a detection time that is as early or earlier than that of the conventional method; furthermore, using the slope-measure in optimally filtered single trials provides warning signs earlier than that of the conventional method during MCA clipping surgery.ConclusionOur results have confirmed the feasibility of the slope-measure for intraoperative SEP monitoring. This is a novel study that provides a useful measure for either EP or single trials in intraoperative SEP monitoring.     

Skeletal muscle fibrosis and stiffness increase after rotator cuff tendon injury and neuromuscular compromise in a rat model

Rotator cuff tears can cause irreversible changes (e.g., fibrosis) to the structure and function of the injured muscle(s). Fibrosis leads to increased muscle stiffness resulting in increased tension at the rotator cuff repair site. This tension influences repairability and healing potential in the clinical setting. However, the micro‐ and meso‐scale structural and molecular sources of these whole‐muscle mechanical changes are poorly understood. Here, single muscle fiber and fiber bundle passive mechanical testing was performed on rat supraspinatus and infraspinatus muscles with experimentally induced massive rotator cuff tears (Tenotomy) as well as massive tears with chemical denervation (Tenotomy + BTX) at 8 and 16 weeks post‐injury. Titin molecular weight, collagen content, and myosin heavy chain profiles were measured and correlated with mechanical variables. Single fiber stiffness was not different between controls and experimental groups. However, fiber bundle stiffness was significantly increased at 8 weeks in the Tenotomy + BTX group compared to Tenotomy or control groups. Many of the changes were resolved by 16 weeks. Only fiber bundle passive mechanics was weakly correlated with collagen content. These data suggest that tendon injury with concomitant neuromuscular compromise results in extra‐cellular matrix production and increases in stiffness of the muscle, potentially complicating subsequent attempts for surgical repair. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1111–1116, 2014.     

A randomized feasibility trial of clonidine to reduce perioperative cardiac risk in patients on chronic beta-blockade: the EPIC study

Purpose

Clonidine may help prevent cardiac complications in patients undergoing non-cardiac surgery and receiving chronic beta-blocker therapy. We conducted a multicentre pilot randomized trial to estimate recruitment rates for a full-scale trial and to assess the safety and tolerability of combining clonidine with chronic beta-blockade.

Methods

Patients who were at elevated perioperative cardiac risk, receiving chronic beta-blockade, and scheduled for major non-cardiac surgery were recruited in a blinded (participants, clinicians, outcome assessors) placebo-controlled randomized trial at three Canadian hospitals. Participants were randomized to clonidine (0.2 mg oral tablet one hour before surgery, plus 0.2 mg·day^?1 transdermal patch placed one hour before surgery and removed four days after surgery or hospital discharge, whichever came first) or matching placebo. Feasibility was evaluated based on recruitment rates, with each centre being required to recruit 50 participants within 12-18 months. Additionally, we reviewed study drug withdrawals and safety outcomes, including clinically significant hypotension or bradycardia.

Results

Eighty-two of the 168 participants were randomized to receive clonidine and 86 to receive placebo. The average time to recruit 50 participants at each centre was 14.3 months. Six patients (7%) withdrew from clonidine, while four (5%) withdrew from placebo. Based on qualitative review, there were no major safety concerns related to clonidine. There was a moderate overall rate of cardiac morbidity, with 18 participants (11%) suffering postoperative myocardial infarction.

Conclusion

This pilot randomized trial confirmed the feasibility, safety, and tolerability of a full-scale trial of oral and transdermal clonidine for reducing the risk of cardiac complications during non-cardiac surgery. This trial was registered at www.clinicaltrials.gov: NCT00335582.     

Unilateral otitis media with effusion caused by retained surgical gauze as an unintended iatrogenic complication of orthognathic surgery: case report

Inadvertent retention of surgical gauze during an operation can have disastrous consequences for both the patient and the surgeon. Several cases have been reported, particularly after abdominal surgery. However, it has never to our knowledge been reported as a leading cause of dysfunction of the Eustachian tube after orthognathic surgery. We recently encountered a patient in whom it presented with unilateral otitis media with an effusion after orthognathic surgery. All surgeons involved with orthognathic surgery should be aware that remnants of surgical gauze after orthognathic surgery can compromise the Eustachian tube and cause otitis media with an effusion.