Does an interspinous device (Coflex?) improve the outcome of decompressive surgery in lumbar spinal stenosis? One-year follow up of a prospective case control study of 60 patients

A number of interspinous process devices have recently been introduced to the lumbar spinal market as an alternative to conventional surgical procedures in the treatment of symptomatic lumbar stenosis. One of those “dynamic” devices is the Coflex™ device which has been already implanted worldwide more than 14,000 times. The aim of implanting this interspinous device is to unload the facet joints, restore foraminal height and provide stability in order to improve the clinical outcome of surgery. Published information is limited, and there are so far no data of comparison between the implant and traditional surgical approaches such as laminotomy. The purpose of our prospective study is to evaluate the surgical outcome of decompressive surgery in comparison to decompressive surgery and additional implantation of the Coflex™ interspinous Device. 60 patients who were all treated in the Spine Center of Klinikum Neustadt, Germany for a one or two level symptomatic LSS with decompressive surgery were included. Two groups were built. In Group one (UD) we treated 30 patients with decompression surgery alone and group two (CO) in 30 patients a Coflex™ device was additional implanted. Pre- and postoperatively disability and pain scores were measured using the Oswestry disability index (ODI), the Roland–Morris score (RMS), the visual analogue scale (VAS) and the pain-free walking distance (WD). Patients underwent postoperative assessments 3, 6 and 12 month including the above-mentioned scores as well as patient satisfaction. In both groups we could see a significant improve (p < 0.001) in the clinical outcome assessed in the ODI, in the RMS for evaluation of back pain, in the VAS and in the pain-free WD at all times of reinvestigation compared to base line. At 1-year follow up there were no statistically differences between both groups in all ascertained parameters including patient satisfaction and subjective operation decision. Because there is no current evidence of the efficacy of the Coflex™ device we need further data from randomized controlled studies for defining the indications for theses procedures. To the best of our knowledge this is the first prospective controlled study which compares surgical decompression of lumbar spinal stenosis with additional implanting of an interspinous Coflex™ device in the treatment of symptomatic LSS.     

Effects of fentanyl, alfentanil, remifentanil and sufentanil on loss of consciousness and bispectral index during propofol induction of anaesthesia

The bispectral index (BIS) and a sedation score were used todetermine and compare the effect of propofol in the presenceof fentanyl, alfentanil, remifentanil and sufentanil. Seventy-fivenon-premedicated patients were assigned randomly into five groups(15 in each) to receive fentanyl, alfentanil, remifentanil,sufentanil or placebo. Opioids were administered using a target-controlledinfusion device, to obtain the following predicted effect-siteconcentrations: fentanyl, 1.5 ng ml^–1; alfentanil, 100ng ml^–1; remifentanil, 6 ng ml^–1; and sufentanil,0.2 ng ml^–1. After this, a target-controlled infusionof propofol (Diprifusor) was started to increase concentrationgradually, to achieve predicted effect-site concentrations of1, 2, and 4 µg ml^–1. At baseline and at each successivetarget effect-site concentration of propofol, the BIS, sedationscore and haemodynamic variables were recorded. At the momentof loss of consciousness (LOC), the BIS and the effect-siteconcentration of propofol were noted. The relationship betweenpropofol effect-site concentration and BIS was preserved withor without opioids. In the presence of an opioid, LOC occurredat a lower effect-site concentration of propofol and at a higherBIS₅₀ (i.e. the BIS value associated with 50% probability ofLOC), compared with placebo. Although clinically the hypnoticeffect of propofol is enhanced by analgesic concentrations ofµ-agonist opioids, the BIS does not show this increasedhypnotic effect. Br J Anaesth 2001; 86: 523–7     

Development of the Baylor Gyro Permanently Implantable Centrifugal Blood Pump as a Biventricular Assist Device

The Baylor Gyro permanently implantable centrifugal blood pump (Gyro PI pump) has been under development since 1995 at Baylor College of Medicine. Excellent results were achieved as a left ventricular assist device (LVAD) with survival up to 284 days. Based on these results, we are now focusing on the development of a biventricular assist device (BVAD) system, which requires 2 pumps to be implanted simultaneously in the preperitoneal space. Our hypothesis was that the Gyro PI pump would be an appropriate device for an implantable BVAD system. The Gyro PI 700 pump is fabricated from titanium alloy and has a 25 ml priming volume, pump weight of 204 g, height of 45 mm, and pump diameter of 65 mm. This pump can provide 5 L/min against 100 mm Hg at 2,000 rpm. In this study, 6 half-Dexter healthy calves have been used as the experimental model. The right pump was applied between the infundibular of the right ventricle and the main pulmonary artery. The left pump was applied between the apex of the left ventricle and the thoracic descending aorta. As for anticoagulation, heparin was administered at the first postoperative week and then converted to warfarin sodium from the second week after surgery. Both pump flow rates were controlled maintaining a pulmonary arterial flow of less than 160 ml/kg/min for the sake of avoidance of pulmonary congestion. Blood sampling was done to assess visceral organ function, and the data regarding pump performance were collected. After encountering the endpoint, which the study could not keep for any reasons, necropsy and histopathological examinations were performed. The first 2 cases were terminated within 1 week. Deterioration of the pump flow due to suction phenomenon was recognized in both cases. To avoid the suction phenomenon, a flexible conduit attached on the inlet conduit was designed and implanted. After using the flexible inflow conduit, the required power and the rotational speed were reduced. Furthermore, the suction phenomenon was not observed except for 1 case. There was no deterioration regarding visceral organ function, and pulmonary function was maintained within normal range except for 1 case. Even though the experimental animal survived up to 45 days with the flexible inflow conduit, an increase in power consumption due to thrombus formation behind the impeller became a problem. Lower rotational speed, which was probably produced by the effectiveness of the flexible inflow conduit, was speculated to be one of the reasons. And the minimum range of rotational speed was 1,950 rpm in these 6 BVAD cases and the previous 3 cases of LVAD. In conclusion, 6 cases of BVAD implantation were performed as in vivo animal studies and were observed up to 45 days. The flexible inflow conduit was applied in 4 of 6 cases, and it was effective in avoiding a suction phenomenon. The proper rotational speed of the Gyro PI 700 pump was detected from the viewpoint of antithrombogenicity, which is more than 1,950 rpm.     

Physiologic analysis of cardiac cycle in an implantable impeller centrifugal left ventricular assist device

The purpose of this study was to determine the physiologic relationship between the cardiac cycle and the nonpulsatile impeller centrifugal Taita No.1 left ventricular assist device (T-LVAD) in a chronic animal study. The relationship of the cardiac cycle, pump flow, aortic pressure, left ventricle pressure, and pump power were analyzed by 5 phases in 4 stages. The isovolumetric ventricular phase is from mitral valve closure (MVC) to aortic valve opening (AVO) and is called Stage 1. The ejection phase is from AVO to aortic valve closure (AVC) and is called Stage 2. The isovolumetric relaxation phase is from AVC to MVC and is called Stage 3. The passive filling and atrial contraction phase is from MVC to mitral valve opening (MVO) and called Stage 4. Based on evidence from the physiologic volume change of the left ventricle, the change of pump flow of the T-LVAD in a cardiac cycle by variable voltages of pump control was evaluated using animal models. After left posteriolateral thoracotomy via the fifth intercostal space under general anesthesia, the nonpulsatile centrifugal T-LVAD was implanted into 2 healthy calves. The inflow of the T-LVAD was inserted into the left ventricle through the mitral valve via the left atrial appendage. The arterial blood pressure waveform was measured and recorded on the outflow of the T-LVAD. The 4 phases of a cardiac cycle were defined as MVC-AVO (Stage 1), AVO-AVC (Stage 2), AVC-MVO (Stage 3) and MVC-MVO (Stage 4) according to the outflow pressure of the outflow of the T-LVAD and differential pressure between the outflow and inflow of the T-LVAD. We carried out the real-time waveform measurement for electrocardiogram, the outflow pressure, the T-LVAD flow and the speed, as well as open loop and constant voltage (V). In a cardiac cycle, the sensing current of the T-LVAD was inverse to the speed. The flow of the T-LVAD at the 4 stages was measured individually and analyzed with different control voltages from 10 to 18 V. The highest flow ratio of MVC-AVC/AVC-MVC was noted when the T-LVAD worked on 14 V. By using analysis methodology of the flow ratio of a cardiac cycle, the optimal physiologically effective control of the T-LVAD might be achieved.     

近端血流阻塞式脑保护装置下颈动脉支架成形术的临床研究

目的 研究近端血流阻塞式脑保护装置MO.MA系统在颈动脉支架成形术中预防脑血管栓塞的疗效,并评价其安全性及可操作性.方法 2007年10月至2008年7月,23例符合外科治疗指征的颈动脉硬化狭窄患者入选本研究,其中19例(82.6%)患者有神经系统症状.全脑血管造影后在脑保护装置MO.MA系统下行颈动脉球囊扩张及支架成形术,计算术中脑缺血时间,观察术中及术后30 d神经系统事件的发生情况.结果 颈动脉造影示,6例(26.1%)颈动脉狭窄50%～70%,17例(73.9%)颈动脉狭窄>70%.所有病例在MO.MA系统保护下颈动脉球囊扩张及支架植入均顺利进行,颈动脉平均阻断时间(5.3±1.2)min.术中及围手术期无死亡及脑卒中发生;2例在颈总动脉球囊阻断时出现短暂意识丧失伴对侧肢体短暂抽搐;2例术后出现心动过缓和低血压,持续时间分别为6 h及1周.9例患者术中颈动脉抽血中可见细小斑块碎片.术后30 d随访有1例TIA发作,1例对侧新发脑卒中,术后30 d累积脑卒中发生率及病死率为4.3%.结论 应用近端血流阻断式脑保护装置MO.MA系统在颈动脉支架成形术中预防神经系统事件发生是安全有效的,尤其适合重度及不稳定性斑块的颈动脉硬化狭窄支架成形术治疗.     

超声心动图在巨大房间隔缺损介入封堵术中的应用

目的评价经胸超声心动图(TTE)结合经食管超声心动图检查(TEE)指导巨大房间隔缺损(ASD)介入封堵术的可行性、安全性。方法术前应用TTE结合TEE测量ASD最大径或支撑径,明确其形态、边缘,筛选33例巨大ASD患者接受介入封堵术,术中指导封堵器植入,术后评价疗效。结果 33例中成功24例,失败9例,总成功率为72.73%;其中椭圆形ASD成功率76.47%,类圆形68.75%;ASD边缘足者81.82%,边缘不足者68.18%。TTE测量ASD最大径与封堵器大小相关性良好,TEE测量ASD支撑径与封堵器大小相关性进一步改善。24例成功病例随访6个月以上,无并发症发生。结论术前以TTE结合TEE详细观察ASD大小、形态、边缘筛选适应证,依据TTE和TEE测量的最大径及支撑径选择合适封堵器,结合术中指导及术后疗效评价,对提高巨大ASD介入封堵术的安全性及成功率有重要作用。     

Interaction of an idealized cavopulmonary circulation with mechanical circulatory assist using an intravascular rotary blood pump

This study evaluated the performance of an intravascular, percutaneously-inserted, axial flow blood pump in an idealized total cavopulmonary connection (TCPC) model of a Fontan physiology. This blood pump, intended for placement in the inferior vena cava (IVC), is designed to augment pressure and blood flow from the IVC to the pulmonary circulation. Three different computational models were examined: (i) an idealized TCPC without a pump; (ii) an idealized TCPC with an impeller pump; and (iii) an idealized TCPC with an impeller and diffuser pump. Computational fluid dynamics analyses of these models were performed to assess the hydraulic performance of each model under varying physiologic conditions. Pressure-flow characteristics, fluid streamlines, energy augmentation calculations, and blood damage analyses were evaluated. Numerical predictions indicate that the pump with an impeller and diffuser blade set produces pressure generations of 1 to 16 mm Hg for rotational speeds of 2000 to 6000 rpm and flow rates of 1 to 4 L/min. In contrast, for the same flow range, the model with the impeller only in the IVC demonstrated pressure generations of 1 to 9 mm Hg at rotational speeds of 10,000 to 12,000 rpm. Influence of blood viscosity was found to be insignificant at low rotational speeds with minimal performance deviation at higher rotational speeds. Results from the blood damage index analyses indicate a low probability for damage with maximum damage index levels less than 1% and maximum fluid residence times below 0.6 s. The numerical predictions further indicated successful energy augmentation of the TCPC with a pump in the IVC. These results support the continued design and development of this cavopulmonary assist device.     

Temporary Right Ventricular Mechanical Support in High‐Risk Left Ventricular Assist Device Recipients Versus Permanent Biventricular or Total Artificial Heart Support

Early planned institution of temporary right ventricular assist device (RVAD) support with the CentriMag (Levitronix LLC, Waltham, MA, USA) in left ventricular assist device (LVAD) recipients was compared with permanent biventricular assist device (BVAD) or total artificial heart (TAH) support. Between 2007 and 2011, 77 patients (age range: 25–70 years) with preoperative evidence of biventricular dysfunction (University of Pennsylvania score >50; University of Michigan score >5) were included. Forty‐six patients (38 men; median age 54.5 years, range: 25–70 years) underwent LVAD placement combined with temporary RVAD support (group A); in 31 patients (25 men; median age 56.7 years, range: 28–68 years), a permanent BVAD or TAH implantation (group B) was performed. Within 30 days, 12 patients from group A (26.08%) and 14 patients from group B (45.1%) died on mechanical support (P = 0.02). Thirty patients (65.2%) in group A were weaned from temporary RVAD support and three (6.5%) underwent permanent RVAD (HeartWare, Inc., Framingham, MA, USA) placement. A total of 26 patients (56.5%) were discharged home in group A versus 17 (54.8%) in group B (P = 0.56). Three patients (8.5%) received heart transplantation in group A and six (19.3%) in group B (P = 0.04). In group A, 90‐day and 6‐month survival was 54.3% (n = 25) versus 51.6% (n = 16) in group B (P = 0.66). In group A, 1‐year survival was 45.6% (n = 21) versus 45.1% (n = 14) in group B (P = 0.81). The strategy of planned temporary RVAD support in LVAD recipients showed encouraging results if compared with those of a similar permanent BVAD/TAH population. Weaning from and removal of the temporary RVAD support may allow patients to be on LVAD support only despite preoperative biventricular dysfunction.