Modulation of locomotor activity in complete spinal cord injury

The aim of this study was to evaluate the modulation of muscle activity during locomotor-like movements by different walking speeds in subjects with a motor complete spinal cord injury (SCI) compared to actively- and passively-walking control subjects without neurological deficit. Stepping movements on a treadmill were induced and assisted by a driven gait orthosis. Electromyographic (EMG) muscle activity of one leg (rectus and biceps femoris, tibialis anterior and gastrocnemius) was recorded and analyzed at three stepping velocities with similar body weight support in both subject groups. In SCI subjects, the EMG amplitude of biceps femoris, tibialis anterior and gastrocnemius was in general similar or weaker than in passively- and actively-stepping control subjects, but that of rectus femoris was larger. The degree of co-activation between tibialis anterior and gastrocnemius was higher in SCI than in control subjects. A significant velocity-dependent EMG modulation was present in all four-leg muscles in both subject groups. In SCI subjects, this EMG modulation was similar to that in actively stepping control subjects. It is concluded that in complete spastic SCI subjects, spinal neuronal circuits underlying locomotion can to a large extent adequately respond to a change in external drive to adapt the neuronal pattern to a new locomotion speed. The application of various speeds might enhance the effect of locomotor training in incomplete SCI subject

Volatile anaesthetics and positive pressure ventilation reduce left atrial performance: a transthoracic echocardiographic study in young healthy adults

Background Animal and in vitro studies suggest that volatile anaesthetics affect left atrial (LA) performance. We hypothesized that human LA pump function and dimensions are altered by volatile anaesthetics in vivo. Methods We performed transthoracic echocardiographic (TTE) measurements in 59 healthy subjects (aged 18-48 yr) undergoing minor surgery under general anaesthesia. The unpremedicated patients were randomly assigned to anaesthesia with sevoflurane, desflurane, or isoflurane. TTE examinations were performed at baseline and after induction of anaesthesia and upon placement of a laryngeal mask during spontaneous breathing. After changing to intermittent positive pressure ventilation (IPPV), an additional TTE was performed. The study focused on the velocity-time integral of late peak transmitral inflow velocity (AVTI) and maximum LA volume. Results We found no evidence for relevant differences in the effects of the three volatile anaesthetics. AVTI decreased significantly from 4.1 (1.2) cm at baseline to 3.2 (1.1) cm during spontaneous breathing of 1 minimum alveolar concentration of volatile anaesthetics. AVTI decreased further to 2.8 (1.0) cm after changing to IPPV. The maximum LA volume was 45.4 (18.6) cm3 at baseline and remained unchanged during spontaneous breathing but decreased to 34.5 (16.7) cm3 during IPPV. Other parameters of LA pump function and dimensions decreased similarly. Conclusions Volatile anaesthetics reduced active LA pump function in humans in vivo. Addition of IPPV decreased LA dimensions and further reduced LA pump function. Effects in vivo were less pronounced than previously found in in vitro and animal studies. Further studies are warranted to evaluate the clinical implications of these findings. Clinical trial registration NCT002445

Perioperative factor concentrate therapy

Transfusion of allogeneic plasma has been a life-saving measure for decades in patients with severe trauma or suffering from major surgical blood loss. The safety of allogeneic blood components has improved in terms of pathogen transmission, but haemostatic efficacy of plasma is hindered by the large volume and time required for thawing and infusion. Several plasma-derived and recombinant factor concentrates are clinically available and indicated for targeted replacement of missing coagulation elements in hereditary disorders of thrombosis and haemostasis. When used appropriately, factor concentrate therapy can rapidly restore deficient factor(s) without causing volume overload. The haemostatic defect in perioperative patients is often multifactorial, and therefore careful clinical judgement and timely coagulation testing must be exercised before the administration of factor concentrates. In this review, the rationale for including factor concentrates in perioperative haemostatic management will be discussed in conjunction with the limitations of plasma transfusio

Formation of a stable deacagonal quasicrystalline Al-Pd-Mn surface layer

We report the in situ formation of an ordered equilibrium decagonal Al-Pd-Mn quasicrystal overlayer on the 5-fold symmetric surface of an icosahedral Al-Pd-Mn monograin. The decagonal structure of the epilayer is evidenced by x-ray photoelectron diffraction, low-energy electron diffraction and electron backscatter diffraction. This overlayer is also characterized by a reduced density of states near the Fermi edge as expected for quasicrystals. This is the first time that a millimeter-size surface of the stable decagonal Al-Pd-Mn is obtained, studied and compared to its icosahedral counterpart.Comment: Submitted to Phys. Ref. Lett. (18 July 2001

Impact of loss of high-molecular-weight von Willebrand factor multimers on blood loss after aortic valve replacement

Background Severe aortic stenosis is associated with loss of the largest von Willebrand factor (vWF) multimers, which could affect primary haemostasis. We hypothesized that the altered multimer structure with the loss of the largest multimers increases postoperative bleeding in patients undergoing aortic valve replacement. Methods We prospectively included 60 subjects with severe aortic stenosis. Before and after aortic valve replacement, vWF antigen, activity, and multimer structure were determined and platelet function was measured by impedance aggregometry. Blood loss from mediastinal drainage and the use of blood and haemostatic products were evaluated perioperatively. Results Before operation, the altered multimer structure was present in 48 subjects (80%). Baseline characteristics and laboratory data were similar in all subjects. The median blood loss after 6 h was 250 (105-400) and 145 (85-240) ml in the groups with the altered and normal multimer structures, respectively (P=0.182). After 24 h, the cumulative loss was 495 (270-650) and 375 (310-600) ml in the groups with the altered and normal multimer structures, respectively (P=0.713). Multivariable analysis revealed no significant influence of multimer structure and platelet function on bleeding volumes after 6 and 24 h. After 24 h, there was no obvious difference in vWF antigen, activity, and multimer structure in subjects with and without the altered multimer structure before operation or in subjects with and without perioperative plasma transfusion. Conclusions The altered vWF multimer structure before operation was not associated with increased bleeding after aortic valve replacement. Our findings might be explained by perioperative release of vWF and rapid recovery of the largest vWF multimer

Remifentanil does not impair left ventricular systolic and diastolic function in young healthy patients

Background Experimental studies and investigations in patients with cardiac diseases suggest that opioids at clinical concentrations have no important direct effect on myocardial relaxation and contractility. In vivo data on the effect of remifentanil on myocardial function in humans are scarce. This study aimed to investigate the effects of remifentanil on left ventricular (LV) function in young healthy humans by transthoracic echocardiography (TTE). We hypothesized that remifentanil does not impair systolic, diastolic LV function, or both. Methods Twelve individuals (aged 18-48 yr) without any history or signs of cardiovascular disease and undergoing minor surgical procedures under general anaesthesia were studied. Echocardiographic examinations were performed in the spontaneously breathing subjects before (baseline) and during administration of remifentanil at a target effect-site concentration of 2 ng ml−1 by target-controlled infusion. Analysis of systolic function focused on fractional area change (FAC). Analysis of diastolic function focused on peak early diastolic velocity of the mitral annulus (e′) and on transmitral peak flow velocity (E). Results Remifentanil infusion at a target concentration of 2 ng ml−1 did not affect heart rate or arterial pressure. There was no evidence of systolic or diastolic dysfunction during remifentanil infusion, as the echocardiographic measure of systolic function (FAC) was similar to baseline, and measures of diastolic function remained unchanged (e′) or improved slightly (E). Conclusion Continuous infusion of remifentanil in a clinically relevant concentration did not affect systolic and diastolic LV function in young healthy subjects during spontaneous breathing as indicated by TT

Haemodilution-induced profibrinolytic state is mitigated by fresh-frozen plasma: implications for early haemostatic intervention in massive haemorrhage

Background Fibrinolysis contributes to coagulopathy after major trauma and surgery. We hypothesized that progressive haemodilution is responsible, at least in part, for increased fibrinolytic tendency of blood clot. Methods The study was performed in two parts. First, whole blood (WB) samples collected from six healthy, consented volunteers were diluted in vitro with either saline or fresh-frozen plasma (FFP) to 40% and 15% of baseline. We quantified factor levels related to coagulation and fibrinolysis, and measured endogenous thrombin generation in undiluted control plasma samples and in samples diluted with saline or FFP. Additionally, thromboelastometry was used to assess susceptibility to fibrinolysis after adding tissue plasminogen activator in undiluted WB samples and in samples diluted with saline before and after substitution of fibrinogen or FFP. Secondly, as a model of in vivo haemodilution, we evaluated the same parameters before and after operation in nine consented patients undergoing off-pump coronary artery bypass surgery. Results The dilution with saline caused dose-dependent decreases in plasma levels of coagulation and antifibrinolytic factors, and in thrombin generation. In FFP-supplemented samples, factor levels and thrombin generation were maintained within normal ranges. Fibrinolytic tendency was significantly higher after haemodilution with saline independent of fibrinogen substitution compared with FFP. Similarly, increased tendency for fibrinolysis was also observed in the in vivo haemodilution. Conclusions We demonstrated in vitro and in vivo that progressive haemodilution decreases endogenous antifibrinolytic proteins including α2-antiplasmin and thrombin-activatable fibrinolysis inhibitor, resulting in increased fibrinolytic tendency. Therefore, early fluid replacement therapy with FFP might be advantageous after massive haemorrhag

Perioperative administration of fibrinogen does not increase adverse cardiac and thromboembolic events after cardiac surgery

Background Although infusion of fibrinogen concentrate is increasingly used in bleeding patients after cardiac surgery, safety data are scarce. We aimed to evaluate the effect of perioperative administration of fibrinogen concentrate on postoperative morbidity and mortality in patients undergoing cardiac surgery. Methods During a 2 yr study period, 991 patients underwent cardiac surgery at a single university centre and were eligible for propensity score (PS) matching. We matched 190 patients with perioperative infusion of fibrinogen concentrate (median dose 2 g) with 190 controls without fibrinogen administration. After PS matching, crude outcome was analysed. Further, a multivariate logistic regression including additional risk factors for adverse outcome was performed. The primary endpoint was a composite of mortality and the occurrence of major cardiac and thromboembolic events within 1 yr. Secondary outcomes included mortality after 30 days and 1 yr and the composite of mortality and adverse events after 30 days. Results The administration of fibrinogen concentrate was not associated with an increased risk for mortality and thromboembolic or cardiac events within 1 yr after cardiac surgery [unadjusted hazard ratio (HR) 0.91; 95% confidence interval (CI) 0.55-1.49; P=0.697]. When using multivariate logistic regression model, the HR for adverse outcome in patients with administration of fibrinogen concentrate was 0.57 (95% CI 0.25-1.17; P=0.101). Similarly, the administration of fibrinogen concentrate did not adversely affect the secondary outcomes when applying unadjusted and multivariate regression analyses. Conclusions Our study strongly suggests that the administration of fibrinogen concentrates at low dose is not associated with thromboembolic complications or adverse outcomes after cardiac surger