Extracorporeal support: improves donor renal graft function after cardiac death

Donors after cardiac death (DCD) could increase the organ pool. Data supports good long-term renal graft survival. However, DCDs are <10% of deceased donors in the United States, due to delayed graft function, and primary nonfunction. These complications are minimized by extracorporeal support after cardiac death (ECS-DCD). This study assesses immediate and acute renal function from different donor types. DCDs kidneys were recovered by conventional rapid recovery or by ECS, and transplanted into nephrectomized healthy swine. Warm ischemia of 10 and 30 min were evaluated. Swine living donors were controls (LVD). ECS-DCDs were treated with 90 min of perfusion until organ recovery. After procurement, kidneys were cold storage 4-6 h. Renal vascular resistance (RVR), urine output (UO), urine protein concentration (UrPr) and creatinine clearance (CrCl), were collected during 4 h posttransplantation. All grafts functioned with adequate renal blood flow for 4 h. RVR at 4 h posttransplant returned to baseline only in the LVD group (0.36 mmHg/mL/min +/- 0.03). RVR was higher in all DCDs (0.66 mmHg/mL/min +/- 0.13), without differences between them. UO was >50 mL/h in all DCDs, except in DCD-30 (6.8 mL/h +/- 1.7). DCD-30 had lower CrCl (0.9 mL/min +/- 0.2) and higher UrPr >200 mg/dL, compared to other DCDs >10 mL/min and <160 mg/dL, respectively. Normothermic ECS can resuscitate kidneys to transplantable status after 30 min of cardiac arrest/WI.

Results of a phase I trial evaluating a liver support device utilizing albumin dialysis

BACKGROUND

We have previously reported the clearance of protein-bound and water-soluble hepatic toxins, in vitro and in an animal model, using albumin dialysis as an extracorporeal hepatic support (ECHS) device.

OBJECTIVE

The objective of this study was to evaluate albumin dialysis through a phase I clinical trial. We hypothesized that albumin dialysis would (1) decrease elevated levels of hepatic toxins, (2) increase the Fischer ratio, and (3) decrease hepatic encephalopathy (HES) and intracranial pressure (ICP), while (4) maintaining stable hemodynamics.

METHODS

Patients with acute liver failure were treated with an ECHS device utilizing continuous hemodiafiltration with continuous albumin dialysis. Mean arterial blood pressure (MAP), heart rate (HR), systemic venous oxygen saturation (Svo(2)), ICP, and HES were recorded. Blood samples were evaluated for hepatic toxins and factor VII levels.

RESULTS

Nine patients were enrolled (status I, n = 5; status IIA, n = 4). There was no significant change in MAP, HR, or Svo(2) (MAP: Pre = 81 +/- 5.6 mm Hg, Post = 79 +/- 5.9 mm Hg, P =.70; HR: Pre = 104 +/- 5.2 bpm, Post = 107 +/- 6.2 bpm, P =.62; Svo(2): Pre = 72 +/- 3.5, Post = 71 +/- 1.7, P =.77). There was a decrease in the ammonia and total bilirubin levels (NH(3): Pre = 129.8 +/- 23.8 mg/dL, Post = 63.9 +/- 16.1 mg/dL, P =.01; total bilirubin: Pre = 20.3 +/- 2.5 mg/dL, Post = 17.6 +/- 2.7 mg/dL, P =.4). There was a significant increase of the Fischer ratio and factor VII levels (Fischer ratio: Pre = 0.98 +/- 0.2, Post = 2.17 +/- 0.5, P =.038; factor VII: Pre = 13.9 +/- 4.9, Post = 23.2 +/- 4.8, P =.015). There was a significant decrease in the HES and ICP (HES: Pre = 3.8 +/- 0.1, Post = 2 +/- 0.7, P =.02; ICP: Pre = 37 +/- 3.9, Post = 13.3 +/- 2.8, P =.048). Of 5 status I patients, 1 recovered native hepatic function and 3 were bridged to transplantation.

CONCLUSIONS

This phase I study suggests that albumin dialysis as a liver support device is safe and effective in clearing hepatic toxins, with an associated decrease in the HES and ICP. This encouraging efficacy data warrant further investigation with a phase II/III trial.

A randomized double-blind comparative study of mycophenolate mofetil and azathioprine in combination with cyclosporine and corticosteroids in primary liver transplant recipients

Acute hepatic allograft rejection occurs in approximately 50% to 60% of the patients undergoing liver transplantation. In this study, we compared the rate of acute rejection in liver transplant recipients randomized in a double-blind comparative study to treatment with mycophenolate mofetil (MMF) or azathioprine (AZA), both in combination with cyclosporine and corticosteroids. Five hundred sixty-five primary liver transplant recipients were randomly assigned to treatment with MMF, 1 g twice daily intravenously followed by 1.5 g twice daily orally (n = 278), or AZA, 1.0 to 2.0 mg/kg/d intravenously followed by oral administration (n = 287), in combination with cyclosporine and corticosteroids. Patients were followed up for at least 1 year, and efficacy analysis was based on intent-to-treat methods. Acute rejection was defined according to the Banff histological criteria. The two study groups were balanced for demographic and clinical baseline characteristics. The incidence of acute rejection or graft loss was 47.7% in the AZA patients and 38.5% in the MMF patients (P <.03). The incidence of biopsy-proven and treated rejection censoring for graft loss was 40.0% in the AZA group versus 31.0% in the MMF group (P <.06). Steroid-resistant rejection requiring treatment with either OKT3 or antithymocyte globulin occurred in 8.2% of AZA patients versus 3.8% in MMF patients (P <.02). Patient and graft survival rates at 1 year posttransplantation were 85.4% in the AZA group and 85.3% in the MMF group (P = not significant). MMF was superior to AZA in preventing acute rejection in the first 6 months posttransplantation. MMF and AZA were equivalent in preventing graft loss at 1 year, and the safety profiles between the two immunosuppressive agents were similar.

Loudness discrimination of speech signals spectrally shaped by a simulated hearing aid

A discrimination task was used to assess changes in the loudness of speech that accompanied changes in the spectral tilt of a simulated hearing aid's frequency response. Band-limited (0.25-4 kHz) spondaic words were spectrally shaped at comparison tilt-factor values of -6, 0, and +6 dB per octave and delivered monaurally via insert earphone to each of 10 listeners with normal hearing (NH) and 15 listeners with mild-to-moderate sensorineural hearing impairment (HI). Results for the NH listeners indicated that loudness differences among the tilt factors were generally perceptible and that loudness judgments were highly transitive across different tilt-factor comparisons. Loudness differences were also perceptible to many of the HI listeners when they switched among tilt factors. The HI listeners' data showed some evidence of transitivity, but not so much as was shown by the NH listeners. Intersubject variability in the loudness judgments was found to be comparable for the two subject groups. Results of the study are discussed with regard to their implications for hearing aid fitting, with particular emphasis on the "parameter adjustment and selection" fitting procedure (J. Punch & R. Robb, 1992).

Transjugular intrahepatic portosystemic shunts and liver transplantation in patients with refractory hepatic hydrothorax

Hepatic hydrothorax is a relatively infrequent but potentially serious complication of cirrhosis resulting from the accumulation of ascitic fluid in the chest cavity. Medical management is initially directed at controlling ascites formation, but invasive therapeutic procedures may be required if symptoms persist. The aim of this study was to report on the long-term efficacy and safety of transjugular intrahepatic portosystemic shunt (TIPS) placement to reduce portal hypertension in 12 consecutive subjects with refractory hepatic hydrothorax. Most subjects had evidence of advanced cirrhosis of varying causes (Child-Pugh class A, 1; B, 5; C, 6). Mean subject age was 54 years, and subjects were followed up for a mean of 173 days (range, 7-926 days). The portosystemic pressure gradient after TIPS was reduced to <12 mmHg in all cases. Periprocedural morbidity was noted in 2 subjects, and 30-day survival after TIPS placement was 75%. Overall, 58% of subjects experienced either a complete or partial response following TIPS placement. Subject response did not correlate with age, baseline creatinine clearance, or Child-Pugh score. Cumulative subject survival was 42%, and 4 of the 5 long-term survivors required eventual liver transplantation. Subject age >65 years was associated with early mortality after TIPS placement, but this trend was not statistically significant. All 4 subjects undergoing liver transplantation required perioperative pleural fluid drainage, but only 1 subject has experienced recurrent effusion. We conclude that TIPS may be a safe and effective temporizing treatment for carefully selected patients with refractory hepatic hydrothorax. However, patient survival is limited after TIPS and is primarily determined by availability of liver transplantation.

The role of xanthine oxidase and xanthine dehydrogenase in skin ischemia

The importance of sequential events which lead to skin necrosis has significant implications in trauma, vascular injury, and wound healing. In this series of experiments, we tested the hypothesis that xanthine oxidase (XO) activity was increased along an ischemic gradient of a skin flap and that the XO enzyme activity correlated with an increase in neutrophils. There were two animal groups in which the skin flaps were raised and assayed at 0, 1, or 6 hr. In the other group, they were created as bipedicle flaps for 7 days, before the distal attachment was divided and the tissue assayed. In the acutely raised flaps, some animals were treated with the XO inhibitor, allopurinol. Xanthine dehydrogenase (XD) and XO activity was measured with a fluorometric pterin assay and neutrophil concentration was measured using a myeloperoxidase marker. In this model, there was consistent skin necrosis in the distal end of the skin flap (48 +/- 8%). The data showed that both XD and XO activity in the distal ends was statistically significantly increased over the sham control or proximal ends of the skin flaps at 1 hr (P < 0.05). XO activity remained elevated in the distal ends at 6 hr. Allopurinol significantly reduced the neutrophil concentrations in the distal ends of the skin flaps when compared to untreated animals (P < 0.05). Moreover, allopurinol reduced skin necrosis to 12 +/- 1%. Preconditioning of the skin flap reduced the XO activity to sham control levels. The observations implicate XO activity as source of free radical injury in skin necrosis seen in random skin flaps.(ABSTRACT TRUNCATED AT 250 WORDS)

The stress response in skin: the role of neutrophil products in preconditioning

In this study we tested the hypothesis that neutrophil products are present in ischemic skin flaps and that they are abolished with preconditioning of the skin. Random back flaps were created on rats, and the sequential appearance of neutrophil products and tissue oxidants was measured in the skin flaps. These flaps had predictable skin necrosis (4.7 +/- 0.8 cm) in the distal ends, while preconditioned flaps had no skin necrosis. Neutrophil products were assayed by both histomorphometrics and myeloperoxidase assays. Lipid peroxidation products were measured to assess tissue oxidant production. These data demonstrate that there is an increase in myeloperoxidase activity in skin flaps that is statistically significantly greater in the distal ends of the flaps at 24 hours (p < 0.05). The lipid peroxidation products were statistically significantly elevated at 48 hours in the distal ends (p < 0.05). Preconditioning the skin as a bipedicled skin flap for 7 days and then dividing the distal attachment abolished neutrophil products and tissue oxidant activity in the skin flaps (p < 0.05). These data suggest that neutrophil products and oxidant production are increased in ischemic skin and that preconditioning of the flap markedly attenuates this response.

Identification of xanthine oxidase activity following reperfusion in human tissue

In this series of experiments, we surveyed xanthine oxidase activity after microvascular transfer in the venous effluent after reperfusion of human rectus abdominis muscle (n = 8) and jejunum (n = 4). Enzyme activity was correlated with duration of ischemia and biochemical markers of cellular injury. Xanthine oxidase (XO) activity was measured spectrofluorometrically using a pterin assay, whereas cellular injury was measured with commercial creatinine phosphokinase activity assay and lipid peroxidation products using a spectrophotometer. The data demonstrated that XO activity was statistically significantly increased in muscle flaps kept at room temperature during ischemia compared with muscle flaps that were cooled (p < 0.05). Creatinine phosphokinase activity was also increased after 15 minutes of reperfusion in muscle flaps that were not cooled (p < 0.05). Two of the jejunal free flaps had ischemia times of > 1 hour and had elevated XO activity after reperfusion despite cooling (p < 0.05). Two other jejunal flaps had ischemia times of < 1 hour, but in one case, the XO activity was increased before harvest. The other case had no increase in XO activity.

Loudness matching of signals spectrally shaped by a simulated hearing aid

A hearing aid with multiple frequency responses was simulated by programming an equalizer to produce spectral tilt factors of -6, 0, and +6 dB/octave over the frequency range from 0.25 kHz to 4 kHz. Listeners with normal hearing matched the loudness of signals (speech and white noise) that were shaped by these different equalizer settings and delivered via an insert earphone. All signals with spectra that were tilted, either negatively or positively, were perceived as louder than untilted signals. The general pattern of loudness matching was similar across subjects, and intrasubject judgments were found to be highly transitive. A measure of signal power was found to account only moderately well for the individual data. Preliminary evidence from a follow-up study using tilt factors less severe than those used in the main experiment suggests that loudness differences are roughly proportional to the degree of spectral tilt. The incorporation of level corrections approximating those necessary to achieve equal loudness is recommended in the fitting of programmable hearing aids.

Xanthine oxidase: its role in the no-reflow phenomenon

This study was designed to probe the hypothesis that oxygen-derived free radicals are involved in initiation of the no-reflow phenomenon. We developed a reproducible model of no reflow in the rat hind limb. Laser Doppler studies confirmed that the hind limbs perfused well after 2 or 4 hours of ischemia, but perfusion ceased in the first 10 minutes after 6 hours of ischemia. Venous blood samples and biopsy specimens of skin and muscle were taken after 2 and 4 hours of ischemia to study tissue injury. Blood samples were evaluated for xanthine oxidase (XO), xanthine dehydrogenase, and creatine phosphokinase (CPK) activities. Conjugated dienes and iodine 125-labeled albumin extravasation were quantified in tissue samples. Groups of animals were treated with inhibitors of XO (allopurinol), antioxidant enzymes (superoxide dismutase plus catalase), and free radical scavengers (dimethyl sulfoxide and dimethyl thiourea) to assess the roles of free radicals in ischemia-reperfusion injury in the hind limbs. After 4 hours of ischemia followed by reperfusion, plasma XO activity rose threefold over preischemia levels (p less than 0.05). Xanthine dehydrogenase activity did not change; conjugated diene levels in muscle rose twofold; CPK levels rose sixfold, and 125I albumin extravasation rose twofold (p less than 0.05). Pretreatment with the XO inhibitor allopurinol reduced XO activity to negligible levels and significantly attenuated conjugated diene levels, CPK levels, and albumin extravasation. Albumin extravasation was also significantly attenuated by pretreating animals with superoxide dismutase together with catalase, dimethyl thiourea, and dimethyl sulfoxide. In all animals pretreated with allopurinol or superoxide dismutase and catalase, reperfusion persisted after 6 hours of ischemia. These data suggest that, in ischemia followed by reperfusion, tissue injury is related to oxygen products derived from XO activity.

Acute lung injury following reperfusion after ischemia in the hind limbs of rats

In this study, we proposed that oxygen free radicals participate in the acute pulmonary injury that follows limb ischemia/reperfusion. Using an established model of hind limb ischemia, reproducible lung injury occurred after reperfusion. Lung microvascular permeability was measured with 125I-BSA and increased two-fold after 30 minutes of reperfusion. Pulmonary injury was blocked with DMSO, DMTU, allopurinol, indomethacin, and SOD plus catalase. The degree of pulmonary neutrophil sequestration as assessed by tissue myeloperoxidase activity was significantly diminished in animals pretreated with antioxidants. Pretreatment with indomethacin did not attenuate the neutrophil sequestration within the pulmonary parenchyma. These data suggest that increased lung microvascular permeability and neutrophil accumulation occur following hind limb ischemia/reperfusion. Therapeutic interventions with oxygen radical inhibitors blocked this process, while the prostaglandin inhibitor, indomethacin, only reduced lung permeability.

Signal averaging in real ear probe tube measurements

In this study, signal averaging measurements were performed using a broadband noise as the test signal in two acoustic environments typifying relatively noisy situations in which real ear probe tube measurements are made clinically. The minimum time-domain signal averaging required to reduce the degrading effects of background noise to levels acceptable for the production of valid real ear unaided responses (REURs) was established for three normal listeners at various signal-to-noise (S/N) ratios. Generally, averaging was not required at S/Ns of 20 dB or higher. Acceptable responses were obtained at S/Ns as low as -5 dB when the number of averages was increased to 256 and higher. The function derived from the data in the two acoustic environments was in good agreement with a theoretical rule. Findings suggest that averaging of only a few sweeps of the test signal is required to obtain reliable and valid real ear measurements, even in somewhat noisy test environments. With a knowledge of the levels of the test signal and the background noise, data from this study can be used to determine the requisite number of signal sweeps to be averaged in acquiring real ear responses in a minimum amount of time.

Frequency of R factor-mediated multiple drug resistance in Klebsiella and Aerobacter

A comparative study was done on the transfer frequency of R factors from 90 strains of multiple drug-resistant Aerobacter and 81 strains of Klebsiella to Escherichia coli CSH-2 (F(-), met(-), pro(-), Nal-r). The most common resistance patterns for the Aerobacter isolants were ampicillin streptomycin chloramphenicol tetracycline and ampicillin streptomycin chloramphenicol tetracycline kanamycin neomycin; for the Klebsiella isolants, the most common resistance pattern was ampicillin kanamycin streptomycin tetracycline chloramphenicol neomycin. R factors were isolated from 14.1% of the Aerobacter strains; 61.5% of these R factors harbored R determinants for ampicillin streptomycin tetracycline. R factors were isolated from 79.1% of the Klebsiella strains; four R factors were isolated with significant frequency; streptomycin chloramphenicol kanamycin neomycin, 37.5%; ampicillin streptomycin tetracycline kanamycin neomycin, 14.1%; ampicillin streptomycin tetracycline, 12.5%; and streptomycin chloramphenicol tetracycline, 12.5%.Chloramphenicol, kanamycin, and neomycin resistance was rarely transferred from the Aerobacter strains, although over 50% of the clinical isolants possessed resistance to these antibiotics. In contrast, over 75% of the Klebsiella strains transferred resistance to chloramphenicol, kanamycin, neomycin. Highest frequency of transferred resistance to individual drugs in the Aerobacter strains was to streptomycin (14.8%), whereas in the Klebsiella group resistance to four drugs was transferred at a very high frequency: streptomycin (80.8%), chloramphenicol (78.5%), kanamycin (76.4%), and neomycin (75.9%).