Validation in the sheep of an ultrasound velocity dilution technique for haemodialysis graft flow

BACKGROUND: A simple, rapid, inexpensive method for measuring the flow in a patient's vascular access would permit routine monitoring during haemodialysis, and hence provide information of access graft deterioration sufficiently early to increase the success of minimally invasive remedial procedures. This paper reports the validation of such a method in animals. METHODS: A PTFE graft was implanted in sheep between the carotid artery and the jugular vein. While the sheep was under general anaesthesia and on an haemodialysis circuit, ultrasound velocity in its blood was perturbed by the injection of a 5-10 ml bolus of isotonic NaCl. The pump tubing flow was measured by a transit-time blood flow meter. This flow was combined with the areas of perturbation generated by the injection before and after mixing in the access flow to estimate graft flow. The calculated graft flow was compared to flow measured directly by a transit-time probe on the same carotid artery. RESULTS: Over a 10-fold range, 120-1260 ml/min, graft flow measured by ultrasound velocity dilution agreed well with graft flow measured directly with a scatter of 76 ml/min about the regression line. CONCLUSION: Ultrasound velocity dilution provides a method for measuring flow in the graft accurate enough for clinical evaluation of patients on dialysis.      

Die neue Rubrik ?Molekularbiologie: Prinzipien und Praxis”

Ohne Zusammenfassung     

Elasticity and mechanism of action of bandage material in compression bandages

Supportive bandages without elasticity (e.g. UNNA's-boats) aid the blood lift into the deep veins. Well-stretching bandages result in a more difficult return into the superficial veins. This may be demonstrated by photoplethysmography (PPG).     

Crosslinking of fibrinogen and fibronectin by free radicals: a possible initial step in adhesion formation in osteoarthritis of the temporomandibular joint.

PURPOSE: Adhesion formation in osteoarthritis (OA) of the temporomandibular joint (TMJ) typically results in a sustained limitation of joint movement. We propose the hypothesis that free-radical-mediated crosslinking of proteins underlies this adhesion formation in affected joints. Free radicals may cause oxidative modification of proteins, creating an opportunity for the formation of intramolecular and intermolecular crosslinks via covalent bonds. This may stabilize protein aggregates, rendering them more resistant to degradation. In this study, the free-radical-mediated crosslinking of model proteins (fibrinogen and fibronectin) was investigated to test our hypothesis that free radicals contribute to adhesion formation via this mechanism in OA of the TMJ. MATERIALS AND METHODS: Physiological clot formation of fibrinogen by thrombin and free-radical-induced crosslinking of fibrinogen and of fibronectin were analyzed using spectrophotometric turbidity measurements, light-scattering techniques, polyacrylamide gel electrophoresis (PAGE), and rotary shadowing. RESULTS: Fibrinogen was shown to aggregate after free radical treatment, as detected using turbidity measurements and light-scattering techniques. Using PAGE, fibrinogen as well as fibronectin was shown to degrade under low oxidative stress. Under high oxidative stress, however, fragments from both proteins were found to be covalently crosslinked, resulting in high-molecular-weight protein aggregates. The aggregation was shown to be at random with rotary shadowing. CONCLUSION: The study shows that high oxidative stress contributes to the formation of crosslinked proteins that may serve as an initial scaffolding for the development of adhesions frequently seen in OA of the TMJ.     

Untersuchungen zur Effizienz der notärztlichen Therapie bei Patienten mit Schädel-Hirn- bzw. Polytrauma Ein Beitrag zur Qualitätssicherung in der Notfallmedizin

For cardio-pulmonary resuscitation there are standardized treatment concepts, but there have been few prospective investigations examining the efficacy of prehospital advanced trauma life support and its effect on the outcome in patients with severe head injury and multiple trauma treated within the German emergency system. The results of this study underline the importance of intensive prehospital treatment and highlight some problems that should be taken into account in future in the training of emergency physicians. Methods. A total of 179 patients with cerebral trauma were investigated. Data obtained included demographic and logistic data of the patients and the emergency physicians, diagnoses and treatment at the scene of the accident and state of the patient on admission in each case. Having divided the patients into three groups by severity of the trauma, we distinguished between sufficient and insufficient treatment and assessed infusion therapy, ventilatory support, positioning and immobilization, and analgesic and sedative therapy. For statistical analysis of the data we used χ²-test and Fisher's exact test. P<0.05 was considered significant. Results. There were 102 patients who had sustained a cerebral trauma without other life-threatening lesions (score 1), 40 with multiple trauma (score 2) and 37 with multiple trauma (score 3). On average 2.4?IV lines were established and the patients received 1186±765?cc of crystalloid in addition to 801±411?cc of colloid fluids. In all groups, patients who received adequate infusion therapy had a better outcome; even in the group with score 1 significantly fewer had a fatal outcome. In all, 167 (93%) patients had endotracheal tubes placed, and in 150 cases (84%) ventilatory therapy was considered sufficient. The proportion of score 1 patients with sufficient ventilatory support who had a fatal outcome was significantly lower than that in the group with insufficient treatment. In patients with multiple trauma we could not separate the benefits of sufficient respiratory therapy and infusion therapy. In only 54% of the cases a vacuum mattress was used and in only 41% the patients were positioned with the upper part of the body elevated by 30°. These were 28 patients (16%) who received neither analgesics nor sedatives. Regardless of the quality of prehospital treatment of isolated head injury, a Glasgow Coma Scale (GCS) score lower than 5 involved a very high mortality and all patients with a GCS score of 9 or more survived. In the group with GCS scores between 5 and 8, however, significantly more of the patients who received adequate treatment survived (82.5% vs 40%). Conclusions. The present study confirms that sufficient advanced trauma life support can improve the outcome of trauma victims with cerebral trauma. Adequate infusion and respiratory therapy reduce the mortality among such patients significantly. In patients with multiple trauma a clear positive effect of generous infusion therapy also is evident. The clearest effect of sufficient prehospital treatment is seen in patients with isolated cerebral trauma and a GCS score between 5 and 8. These results demonstrate the importance of advanced trauma life support and show emphatically that the so-called scoop-and-run strategy should be abandoned when resources are available for extended preclinical emergency treatment. On the other hand, we detected some problem areas in the prehospital treatment of trauma victims, such as positioning, immobilization and drug therapy with analgesics and sedatives. These findings allow us to pinpoint specific points that should be stressed in the training of emergency physicians and paramedics.     

Combination of ABO blood group incompatibility and glucose-6-phosphate dehydrogenase deficiency: effect on hemolysis and neonatal hyperbilirubinemia

The incidence (%) of hyperbilirubinemia (serum bilirubin ≥257 μmol/l) was similar in neonates with a combination of ABO incompatibility and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency (45%), with ABO incompatibility (54%) or G-6-PD deficiency (37%), alone (ns). Carboxyhemoglobin values, corrected for inspired CO, were similarly elevated in all three groups (0.87 ± 0.32%, 0.82 ± 0.29%, 0.76 ± 0.18%, respectively, ns), but correlated with bilirubin only in those with ABO incompatibility alone. ABO-incompatible/G-6-PD-deficient neonates, compared with those with either condition alone, are not at increased risk for hemolysis or hyperbilirubinemia.