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Many critically ill patients require inotropic or vasopressor support to maintain adequate oxygen delivery. Removal of catecholamines by continuous hemodiafiltration (CHD) could alter exogenous catecholamine requirements. The authors have studied hemodynamic state, catecholamine clearances, and catecholamine requirements in 12 critically ill patients (mean APACHE II score, 24.5) receiving CHD. Hemodynamic parameters were assessed before CHD initiation, and at 4 and 24 hours of therapy. Simultaneous determinations of serum and ultradiafiltrate dopamine (D), norepinephrine (NE), and epinephrine (E) concentrations were obtained. There were no significant changes in any of many hemodynamic parameters measured during CHD. Mean catecholamine requirements were not altered by CHD. Plasma catecholamine levels were not significantly affected by CHD (mean values at 0, 4, and 24 hours: D: 10,801, 12,056, and 8,797 pg/ml; NE: 1124, 566, and 926 pg/ml; E: 1,420, 1,383, and 843 pg/ml). Catecholamine clearances from CHD (D:43.7 ml/min; NE: 43.5 ml/min; and E: 46.6 ml/min) resulted in daily excretion of only 379 micrograms D, 32.9 micrograms NE, and 37.2 micrograms E. Clearances of catecholamines by CHD represented a daily loss of less than 0.1% of the administered load. In conclusion, although CHD can remove circulating catecholamines, cumulative daily catecholamine extraction is minimal in pharmacologic terms, and has no impact on hemodynamic status.

This study assessed myocardial ischemia after resuscitation from cardiac arrest using direct mechanical ventricular actuation (DMVA) or cardiopulmonary bypass (CPB). Myocardial ischemic tolerance was better after DMVA resuscitation. Resuscitation using DMVA, when compared with CPB, may improve outcome when subsequent coronary artery bypass grafting (CABG) is required.

A protamine-coated Cuprophan hemodialysis membrane possessing improved blood compatibility was developed. Protamine was covalently immobilized onto the inner walls of the Cuprophan hollow fibers, using the cyanogen bromide (CNBr) activation method. Studies conducted with aqueous solutions indicated that the immobilization process did not introduce deterioration of the membrane mechanical and mass transfer properties; the permeability of several compounds through the protamine-coated membrane was unchanged. The modified membrane was rendered nonthrombogenic by the adsorption of heparin to the protamine-bound surfaces. Heparin adsorbed on the immobilized protamine retained about 20% of its initial anticoagulant activity. Preliminary studies using the hemolytic complement assay indicated that complement activation by the protamine-coated membrane was statistically far less than that by the untreated membrane.

The efficiency of a new tracheal prosthesis was studied. The prosthesis consists of fine Marlex mesh reinforced with a continuous Teflon spiral, and it is grafted and coated with pig collagen, with the aim of promoting connective tissue infiltration and providing air-tightness during the initial stage of implantation. Complete surgical resection and replacement of a 4-6 tracheal ring segment of the cervical trachea was performed in 13 adult mongrel dogs. Except for two dogs that developed anastomotic insufficiency, the prostheses in all dogs were infiltrated by the surrounding connective tissue, and were completely incorporated by the host trachea at the anastomotic sites. Formation of respiratory epithelium that lined the prosthesis lumen, was seen to varying degrees, and in one dog killed at 4 months after reconstruction, this was confirmed histologically from the upper to the lower anastomosis of the prosthesis. Stenosis of the lumen often occurred, however, due to deformation of the prosthesis and overgrowth of granulation tissue. The authors conclude that this tracheal prosthesis is highly biocompatible, and might be useful for repairing tracheal defects by improving prosthesis processing, especially that used for insertion of stents.

Data on the use of recombinant human erythropoietin (rHuEPO) were obtained from 25 hemodialysis centers to determine whether route of administration (intravenous [i.v.] vs. subcutaneous [s.c.]) or various dialysis factors influenced the response to rHuEPO; 844 of 958 patients had sufficient data for evaluation. Hematocrit (HCT) increased from 23.8 to 29.1% after a mean rHuEPO treatment period of 202 days; 48.4% of all patients did not reach a HCT greater than or equal to 29%. The s.c. route increased HCT more than the i.v. route. Multivariate analysis of the response (i.e., increase in HCT from baseline) showed a positive correlation with more rapid dialysis but a negative correlation with reuse, baseline HCT, transfusion dependence, and frequency of administration. The effects of dialysis and reuse were not present when the response was normalized by weekly dose. It was concluded that one half of all patients treated did not attain the recommended target HCT, perhaps due to economic constraints or resetting of goals. The s.c. route may be preferable to optimize response.

Expanded polytetrafluoroethylene (EPTFE) grafts have poor neoendothelial healing characteristics and low patency rates after long-term implantation. The authors have shown that this is due to the low porosity of currently used EPTFE grafts (20-30 microns fibril length). The inner surface coated grafts made of long antithrombogenic material fibrils (40-60 microns) are desirable, especially for small diameter grafts. The authors have implanted these surface modified grafts (coated grafts) and noncoated grafts into abdominal arteries of rats and observed good patency rates, and the effects of surface modification of the grafts on stable endothelial tissue growth. The authors used four different kinds of grafts (fibril length, 20, 40, 60, and 90 microns, respectively) to investigate the effect of porosity. High porosity (long fibril length) grafts induce good neoendothelial healing and collagen production.

Forty-eight chronic hemodialysis (HD) patients (pts) completed questionnaires that used linear analogue scales (LAS), yes/no responses, and demographic data collection to characterize sleep disorders. Twenty-five pts (52%) reported problems sleeping. These pts graded sleep problems significantly higher than those without sleep problems (6.5 +/- 3 vs. 1.8 +/- 2, p less than 0.001 by LAS). Those with sleep disorders were more likely to smoke cigarettes (13/25 vs. 6/23, p less than 0.05) and have bone pain (14/25 vs. 6/23, p less than 0.05). No differences among pts with and without sleep problems were seen in age, gender, time on dialysis, caffeine intake, pruritus, feelings of sadness, worry, or anxiety, or Kt/V values (1.5 +/- 0.2 vs. 1.4 +/- 0.2, p less than 0.13). Restless legs (84%), onset insomnia (76%), and nighttime (76%) and early A.M. waking (72%) characterized the sleep disorders; symptoms suggesting nocturnal myoclonus were less common (20%). We conclude that sleep disorders are common in HD pts and may be exacerbated by tobacco use, bone pain, and restless legs. Kt/V does not correlate with sleep disorders. Further examination of this problem, including formal sleep studies, is needed.

To continuously monitor the blood pressure (BP) in an internal arteriovenous fistula, the blood tubing wall was punctured with a long, fine needle (25 gauge), and the needle tip was advanced into the fistula vein through the lumen of the outflow blood access puncture needle. It was found that the intrafistula BP thus measured varied in parallel with the systemic arterial BP during hemodialysis (HD). When the intrafistula BP fell to 60% of the level at the start of HD, 50 ml of saline was administered. As a result, hypotension was prevented completely in 60 HD in five patients who often showed symptomatic hypotension during HD.

Simultaneous heparin extracorporeal LDL precipitation (HELP)-dialysis was carried out at weekly intervals in six patients with end-stage renal failure, associated hyperlipidemia, and a high risk of premature atherosclerosis. Evaluating 135 single treatments, a mean acute total cholesterol/LDL reduction of 31% and 39%, respectively, was found, while clearance of urinary substances was comparable to that in regular hemodialysis treatment. Treatment tolerance was excellent and no derangements in albumin, hemodialysis parameters, or blood coagulation were detected.

Fe3+ preincubation has been shown to inhibit pathologic calcification of glutaraldehyde preserved bovine pericardium (GPBP) in the short-term rat subdermal model (21 days). This study was designed to test the long-term anticalcification efficacy of Fe3+ in the same model. Glutaraldehyde preserved bovine pericardium was preincubated (1 hr, 25 degrees C) in 0.1M FeCl3, 0.01M FeCl3, or 0.05M HEPES, then implanted subdermally in weanling male rats (40-60 gm) for 21, 60, 90, and 120 days. At explant, Fe3+ and Ca2+ levels were measured by atomic absorption spectroscopy. Fe3+ effectively inhibited calcification in both experimental groups compared to control through the longest implant (Ca2+ levels, 120 day implant: 0.1M FeCl3 = 46.85 +/- 17.45 micrograms/mg; 0.01M FeCl3 = 17.31 +/- 7.38 micrograms/mg; control = 258.04 +/- 15.71). Measurement of explanted GPBP Fe3+ levels showed that tissue Fe3+ levels of at least 7.28 +/- 0.70 micrograms/mg were required to effectively inhibit calcification after a 120-day implant. There was no evidence of Fe3+ impairment of rat growth. In conclusion, Fe3+ pretreatment of GPBP significantly inhibited calcification after long-term (120 day) rat subdermal implant.