体外循环自体血回收方法的血液流变学评价

目的：从血液流变学比较３种自体血回收技术的利弊。方法：将３０例心脏瓣膜替换术患者分成３组：自体肝素血组、离心组、超滤组，采集其体外循环结束后余血，分别经以上３种方法处理，测定血液流变学参数、红细胞变形指数、粘度、血细胞比容和部分血液成分的变化。结果：经离心、超滤处理后的血液与未经处理的自体肝素血相比，表现为变形性降低、高粘度和高血细胞比容，血钾、钙、钠离子的浓度和游离血红蛋白亦有差异，离心洗涤后的血液电解质改变显著，而超滤有明显的血液破坏作用。结论：应综合３种血液回收技术的优劣。     

{beta}2-Microglobulin Kinetics During Haemodialysis and Haemofiltration

Since the identification of ß₂-microglobulin as amajor component of ‘dialysis amyloid’, concern aboutits removal by different dialysis methods has been raised. Haemodialysiswith regenerated cellulose membranes increases serum ß₂-microglobulinby 10–15%. Serial measurements show a very early increaseduring cuprophan haemodialysis, the mechanism of which is asyet unknown. After cuprophan haemodialysis, serum values returnto the initial pretreatment concentrations by the time of thenext haemodialysis. In contrast to regenerated cellulose, dialysiswith polycarbonate lowers serum ß₂-microglobulin by8%, and dialysis with polysulphone by 53%. As opposed to cuprophan,after polysulphone haemodialysis the serum concentrations havenot returned to the initial pretreatment levels within 48 h.Comparison of ß₂-microglobulin removal using the samepolysulphone membrane for haemodialysis and haemofiltrationshows that ß₂-microglobulin is more effectively removedby convection than by diffusion when both treatment modes arematched for blood flow and urea clearance. Therefore, in contrast to haemodialysis with regenerated cellulosemembranes, where a transient, intradialytic release of ß₂-microglobulinis induced, significant removal is observed using, higher permeablemembranes. These findings may have implications for the generationof ‘dialysis amyloid’.     

Pharmacokinetics of vancomycin in patients undergoing haemodialysis and haemofiltration

Vancomycin is widely used for the treatment of infections with Gram-positive bacteria in patients with end-stage renal disease. The concentration of vancomycin in serum, in ultrafiltrate, and in dialysate was measured during nine haemofiltration and seven haemodialysis procedures with high-permeability membranes. The t1/2 of vancomycin was 101 +/- 19 h in the interdialytic and interhaemofiltration period. There was no significant difference between the haemodialysis clearance (55.2 +/- 18.5 ml/min) and the haemofiltration clearance (66.8 +/- 13.6 ml/min). The redistribution phenomenon was about 25% in the post haemofiltration period and only 10% in the post haemodialysis period. Approximately 270 mg of vancomycin was recovered in dialysate or ultrafiltrate. With high-permeability membranes more commonly used in patients with end-stage renal disease, continuous monitoring of vancomycin therapy is recommended.     

Detection of overdosage of sedation in a patient with renal failure by the absence of lower oesophageal motility

We report an accidental overdosage of morphine and midazolam in a patient with renal failure receiving haemofiltration detected by the absence of oesophageal motility. This situation demonstrates the difficulties of assessing the level of sedation as well as the dosage requirements in this type of patient.     

Influence of continuous haemofiltration-related hypothermia on haemodynamic variables and gas exchange in septic patients

Objective To investigate the influence of continuous haemofiltration (CHF) on haemodynamics, gas exchange and core temperature in critically ill septic patients with acute renal failure.Patients and methods In 20 patients (17 male, 3 female) ultrafiltration rate, core temperature, gas exchange and haemodynamic variables were measured at regular intervals during the first 48 h of haemofiltration. Baseline data were compared to those obtained 30 min after initiating CHF and also to those during hypothermia (if observed).Main results Haemodynamic variables remained remarkably constant throughout the study period. In patients with a relatively low ultrafiltration rate (855±278 ml/h) temperature did not change, while in patients with a high ultrafiltration rate (1468±293 ml/h) core temperature significantly decreased from 37.6±0.9°C to 34.8±0.8°C (p<0.001). There was a statistically significant correlation between temperature decrease and ultrafiltration rate (r=–0.68, Y=1.8–0.003 X,p<0.01). Hypothermic patients also showed a mean decrease in VO₂ from 141±22 ml/min/m² to 112±22 ml/min/m² (p<0.01) with a concomitant increase in PaO₂ from 103±37 mmHg to 140±42 mmHg (p<0.001) and in P O₂ from 35±4 mmHg to 41±5 mmHg (p<0.001).Conclusions: 1) Continuous haemofiltration does not cause significant alternations in haemodynamic variables. 2) Hypothermia frequently occurs in patients undergoing continuous haemofiltration with high ultrafiltration rates. These hypothermic patients show a reduction in O₂ leading to an increase in P O₂ and PaO₂. This mild hypothermia in these circumstances has no evident deleterious effects.     

Continuous venovenous haemofiltration using polyacrylonitrile filters does not activate contact system and intrinsic coagulation pathways

Objectives: To investigate whether continuous venovenous haemofiltration using polyacrylonitrile filters causes activation of the contact system and intrinsic coagulation pathways and if this, and/or low plasma levels of endogenous anticoagulants, influences filter lifespan. Design: Observational study. Setting: University Teaching Hospital Intensive Care Unit. Patients: Twelve critically ill patients with acute renal failure receiving continuous venovenous haemofiltration. Interventions: Blood samples were taken before starting haemofiltration, at 15 min, 1 h, 3–4 h, 8–12 h, 24 h and at 24-h intervals thereafter until filter blockage occurred. Measurement was made of the contact and intrinsic coagulation system proteins factor XII, activated factor XII and prekallikrein and the protease inhibitors antithrombin III, heparin co-factor II, alpha₂-macroglobulin and C1-esterase inhibitor. Thrombin-antithrombin complex levels were measured to provide evidence of thrombin generation. Results: (i) Factor XII, prekallikrein and contact system inhibitors were subnormal in 10/12 and activated factor XII raised in 11/12 patients at baseline, implying pre-existing contact pathway activation. (ii) No change occurred during haemofiltration in the intrinsic coagulation pathway factor or inhibitor levels. (iii) Clotting of the filter circuit within the first 24 h occurred in 5/12 and was associated with low baseline levels of antithrombin III and heparin co-factor II. Only in these patients did thrombin-antithrombin complex levels rise significantly. Conclusions: The contact system was not activated further by continuous venovenous haemofiltration using polyacrylonitrile filters in critically ill patients. Premature clotting of the haemofilter circuit was more common in patients with very low levels of antithrombin III and heparin co-factor II; although this was related to thrombin generation, the intrinsic coagulation pathway does not appear to be implicated. Received: 6 February 1995 Accepted: 4 October 1996     

Systematic review on the treatment of deceased organ donors

Background

Currently, there is no consensus on which treatments should be a part of standard deceased-donor management to improve graft quality and transplantation outcomes. The objective of this systematic review was to evaluate the effects of treatments of the deceased, solid-organ donor on graft function and survival after transplantation.

The consequences of continuous haemofiltration on lung mechanics and extravascular lung water in a porcine endotoxic shock model

Endotoxinaemia (E. coli endotoxin, 0.111.B4) and pulmonary hypertension were evoked in 20 swine, randomly assigned to receive either zero-balanced venovenous haemofiltration (HF) with an ultrafiltration and replacement rate of 600 ml/h (HF group,n=10) or to undergo an uninfluenced spontaneous course (E group,n=10) during a constant infusion of endotoxin until the end of the experiment. Endotoxin-induced pulmonary dysfunction was assessed on the basis of extravascular lung water (EVLW) using a thermo-dye technique via a fiberoptic intra-aortic probe, gas exchange and lung mechanics, the latter derived by a pressure-volume loop (P/V loop) of the respiratory system (super syringe, flow 30 ml/s, tidal volume 600 ml). A comparable increase in alveolo-arterial oxygen difference and a constant EVLW was observed in both groups. The progessive deterioration of hysteresis area and compliance parameters by endotoxinaemia was significantly blunted by HF. Independent of an impact on pulmonary oedema zero-balanced HF modifies endotoxin induced lung injury, probably by the convectice transport of mediator substances.