Intraoperative ultrasound imaging of the liver at the time of colorectal cancer resection

OBJECTIVES

To evaluate the accuracy of intraoperative ultrasound (IOUS) liver imaging at the time of primary colorectal cancer resection, which might eliminate incurable patients from adjuvant chemotherapy trials or permit earlier resection of curable metastases.

DESIGN

A prospective trial of routine IOUS liver imaging during resections of primary colorectal cancer. The rate of detection of occult metastases by IOUS imaging alone and the false-negative rate over 22.7 months of follow-up were determined.

SETTING

A tertiary care referral center in Boston, Mass.

PATIENTS

Fifty-five patients undergoing 56 operations for colorectal carcinoma between May 1990 and June 1992.

MAIN OUTCOME MEASURES

The rate of detection, by IOUS imaging alone, of otherwise occult hepatic metastases, the total number of patients with metastases detected at any time during follow-up, and the rate of false-negative findings on IOUS imaging and direct examination.

RESULTS

Occult hepatic metastases were detected by IOUS imaging alone in 5% of patients. Restriction of IOUS imaging to patients with T3 or T4 lesions or recurrent cancers would have identified all metastases and increased the detection rate to 10%. Occult metastases were detected by IOUS imaging alone in 12.5% of patients with T3, N0 lesions. The rate of false-negative findings on IOUS imaging was 13% overall, 0% for patients with T1 or T2 lesions, 3% for patients with node-negative findings, and 7% for patients with T3, N0 lesions.

CONCLUSIONS

The small increment in the detection of occult metastases by IOUS liver imaging does not warrant its use in all patients with colorectal cancer. Selective use in patients with T3 or T4 lesions or recurrent cancers increased the incremental gain in detection. The observed frequency of occult metastases in patients with T3, N0 lesions is sufficient to impact on results of adjuvant chemotherapy trials. Longer follow-up in more patients is needed to determine whether a negative IOUS study is an additional favorable prognosticator in patients with T1 and T2 lesions and node-negative findings.

The relationship of prostate-specific antigen to digital rectal examination and transrectal ultrasonography. Findings of the American Cancer Society National Prostate Cancer Detection Project

The participating institutions of the American Cancer Society National Prostate Cancer Detection Project did 520 biopsies on 2425 men over a 3.5-year period. A total of 88 cancers were confirmed pathologically, 93% of which clinically were organ confined. In 324 men (62.3%), a recommendation for biopsy was made based solely on the results of transrectal ultrasonography (TRUS); in 69 patients (13.3%), solely on the digital rectal examination (DRE); in 116 patients (22.3%), on abnormal DRE and TRUS examinations; and in 11 patients (2.1%), in whom DRE and TRUS were normal, on elevated prostate-specific antigen (PSA) levels. The TRUS was abnormal in 80.6% of men found to have cancer, and the PSA level and DRE were abnormal for 67% and 50% of cancers, respectively. The influence of PSA level on cancer detection increased as the serum level increased above 4 ng/ml. The positive predictive values of both the DRE and TRUS were influenced significantly by the presence of an elevated PSA level (P = 0.044 and P less than 0.001, respectively). The results of this ongoing multicenter study support the following statements: (1) the prostate cancer detection rate is influenced by this diagnostic triad and (2) the detection rate of organ-confined disease can be improved substantially by early detection programs.

Experimental and clinical observations on hepatic cryosurgery for colorectal metastases

Cryosurgery, using liquid nitrogen at -196 degrees C, was explored for treating colorectal liver metastases in an experimental study of rat colon cancer and in a clinical investigation of patients with unresectable liver tumors. The viability of rat colon cancer isografts showed that while two or three freeze-thaw cycles were 100% effective in controlling established isografts and preventing isograft take, one freeze-thaw cycle was suboptimal. In these animals cryosurgery was as effective as surgical resection in controlling established experimental liver metastases. Cryosurgery by operative liver exposure and intraoperative ultrasound monitoring were used to treat liver metastases from colorectal cancer in 24 patients. At a median follow-up of 2 years (range, 5 months to 5 years), seven patients (29%) are disease free, eight (33.5%) are alive with recurrent tumors, and nine (37.5%) have died. The patterns of failure were: remaining liver and extrahepatic sites, ten patients (59%); remaining liver only, six patients (35%); and extrahepatic only, one patient (6%). These data demonstrate that cryosurgery is a useful modality for treating unresectable primary and metastatic liver cancers. Addition of systemic adjuvant therapy may improve the tertiary failure following the control of liver metastases.

A 5-year study of cryosurgery in the treatment of liver tumors

This report summarizes our 5-year experience with cryosurgery for in situ ablation of liver tumors. The liver was exposed with laparotomy, and the tumors were subjected to two freeze-thaw cycles using liquid nitrogen delivered by insulated probes; cryoablation was monitored with intraoperative ultrasonography. Tumor markers and computed tomography evaluated tumor response during long-term follow-up. From 1985 to 1990, 32 patients (19 men and 13 women) were entered into this study. The histologic characteristics of the tumors were as follows: colorectal, 24 patients; hepatoma, three patients; neuroendocrine, two patients; and others, three patients. After a follow-up period of 5 to 60 months (median follow-up, 24 months), nine patients (28%) remained disease free, 11 patients (34%) were alive with disease, and 12 patients (38%) died. The patterns of failure included liver and extrahepatic disease in 54% of cases, liver disease only in 32% of cases, and extrahepatic disease only in 14% of cases. In patients with "liver only" failure, recurrence at the treatment site occurred in three patients (9%). This study establishes the long-term effectiveness of cryosurgery in the treatment of primary and metastatic liver tumors.

The blood pressure and heart rate chronome of centenarians

Rhythm characteristics of blood pressure (BP) and heart rate (Hr) of 11 healthy centenarians and 66 medical students are described. Each subject ambulatorily monitored measured BP and HR around the clock at 15-min intervals for 48 hours. Least-squares spectra were obtained by the fit of cosine curves (cosinor) and compared between the two populations. Confounding by geographic differences seems to be ruled out by comparisons with results from international data bases. A shift in prominence from the circadian domain to higher frequency harmonics was found for the BP but not for the HR of centenarians. In clinically mostly healthy centenarians, markers of primary aging may consist of a relatively low circadian BP and HR amplitude and a tendency toward internal and external desynchronization. Whether these chronobiologic changes with age are desirable, indifferent or undesirable can now be elucidated by outcome studies, in the light of the reference standards provided herein.

Effect of cyclosporine and steroids on canine bile flow

Cyclosporine and hydrocortisone are the main immunosuppressants used in transplant surgery. The purpose of this study was to determine the effect of intravenous administration of cyclosporine and hydrocortisone on bile flow in dogs. Cyclosporine in doses of 0.5, 1.0 and 1.5 mg.kg-1.hr-1 were administered along with 18 mumol/min intravenous sodium taurocholate to dogs with chronic biliary and gastric fistulas. Bile volume and bile chloride concentration and output were increased by cyclosporine in a dose-related manner, whereas bile salt concentration decreased and bile salt output was unchanged. Hydrocortisone produced small but significant increases in bile flow only at the highest dose of hydrocortisone administered. Subsequently, experiments were performed when sodium taurocholate was administered in progressively increasing doses (9, 18 and 36 mumol/min), with the dose changed every hour. Bile volume, [14C]erythritol clearance in bile and bile salt concentrations were measured with and without cyclosporine and hydrocortisone administration. Cyclosporine increased the bile salt-independent fraction of canalicular bile flow and ductular bile flow. Experiments evaluating the role of the cyclosporine carrier polyoxyethylated castor oil (Cremophor EL) demonstrated that this substance had no independent choleretic activity, whereas cyclosporine dissolved in ethanol and administered without Cremophor EL significantly increased bile flow. The results of this study indicate that cyclosporine stimulates chloride-rich choleresis independent of bile salt secretion.

Ankle tendons: evaluation with CT

Computed tomographic (CT) analysis of 21 clinically suspected ankle tendon injuries was performed in 18 patients. In six of the 21 ankles surgical exploration was done, and in one ankle evaluation was done while the patient was under anesthesia. In all seven cases the CT findings were confirmed and in three the clinical diagnosis was disproved. CT provided additional information and helped guide treatment in the majority of patients studied. Thus CT is an accurate, noninvasive modality for assessing ankle tendon injuries.

Hepatic cryosurgery with intraoperative ultrasound monitoring for metastatic colon carcinoma

We utilized cryosurgery with intraoperative ultrasound (IOUS) monitoring in ten patients to treat multiple unresectable hepatic metastases from colorectal carcinoma. The liver was exposed at laparotomy, and tumors were subjected to three cycles of freezing (eight minutes each) and thawing. Freezing was monitored by IOUS, which visualized frozen tumor as a hyperechoic rim with posterior acoustic shadowing. Frozen normal liver appeared hypoechoic after thawing compared with normal unfrozen liver. There were no significant complications. The follow-up ranged from four months to 17 months (median, 7.5 months). Tumor response was documented by pathologic findings (coagulative necrosis), progressive fall of carcinoembryonic antigen levels, and computed tomographic scan evidence of necrosis and shrinkage of tumor. One patient underwent repeated laparotomy five months after cryosurgery and had the frozen lesions resected; there was no residual tumor. This study establishes the technical feasibility and antitumor response of hepatic cryosurgery and the use of IOUS for precise localization and monitoring of cryoablations.

CT body stereotaxic system for placement of needle arrays

A new CT body stereotaxic system that is particularly suited to multiple placements of needles precisely in parallel is described. By scanning through a right triangle placed on the patient's skin, the stereotaxic method defines an entry point for the first needle placement. An articulating arm is then used to aim the needle at the entry point and hold the needle at the correct angle. The arm can be angled so that the complex approaches from one scan plane to another can be made to place needle arrays through inaccessible lesions, for instance, beneath the diaphragm. Animal and phantom studies have shown that placement of multiple needle arrays in parallel from CT scan data is possible.

The influence of domestic position on health status

Data from the Robert Wood Johnson Foundation 1982 survey of access to health care are used to examine the influence of household composition and members' domestic position--e.g. age, sex, marital status, and presence of children, on health status and use of health services. A hierarchical analysis was undertaken to sort groups of individuals and households having different domestic structures. The results of the analyses of use and access for these groups show that, after controlling for age, domestic position and household arrangements are significant explanatory variables. Ways to refine the approach are discussed.

Society of Gastrointestinal Radiologists Roscoe E. Miller Award. Monitoring hepatic cryosurgery with sonography

The intraoperative sonographic appearance of frozen hepatic tumors and frozen normal liver was correlated with the histologic appearance of pathologic specimens from six patients. Frozen tissue was visualized as a hyperechoic rim with posterior acoustic shadowing. Normal liver that was frozen and then thawed appeared hypoechoic when compared with normal unfrozen liver. These findings allowed visualization of the extent of freezing in relation to tumor margins. Pathologically, frozen tumors showed definite evidence of necrosis. Normal liver tissue was extremely sensitive to cold and was completely necrotic after freezing. The sonographic appearance of frozen and thawed liver correlated precisely with the gross morphologic and histologic changes seen in the cryolesion. It appears that intraoperative sonography allows accurate monitoring of hepatic cryosurgery.

CT body stereotaxis: an aid for CT-guided biopsies

A new body stereotaxic system used to facilitate CT-guided biopsies is described. By scanning through a triangle placed on the patient's skin, the method defines an entry point for the biopsy. An articulating arm is then used to aim the needle at the entry point and hold the needle at the correct angle. The arm can be angled so that complex approaches from one scan plane to another can be made in order to take biopsies of lesions beneath the diaphragm. Using the system, 23 of 25 lesions were hit on the first needle manipulation; two manipulations were needed for each of the other two lesions. In comparison with previous experience, procedure time was decreased and the numbers of needle manipulations and localization scans were decreased 75% and 90%, respectively.

Electrocochleographic changes in the hearing loss associated with X-linked hypophosphataemic osteomalacia

Transtympanic electrocochleography was carried out on 13 patients (21 ears) suffering from X-linked hypophosphataemic osteomalacia, and known to have cochlear hearing loss. The majority of ears exhibited a cochlear pattern of cochleogram with a recruiting input/output function and a markedly biphasic action potential. In addition 14 ears yielded a greatly enhanced negative summating potential, suggesting the presence of endolymphatic hydrops. It is proposed that the hearing loss so frequently associated with this condition is in part due to endolymphatic hydrops.

Systematic biases in functional status assessment of elderly adults: effects of different data sources

Measuring functional status using specific instruments is an important part of geriatric assessment. These instruments, however, often rely on data sources different from those with which they were originally validated. To study possible biasing effects of different data sources on functional status scores, we examined scores for two widely used instruments (the Lawton Personal Self-Maintenance Scale, PSMS, and Instrumental Activities of Daily Living, IADL, Scale) on a group of hospitalized elderly (n = 61) using three different data sources (the patients themselves, the patients' nurses, and significant others). Analysis showed that PSMS scores derived from patients were significantly higher than scores derived from significant others (p less than .025) and that patient-derived IADL scores were significantly higher than both nurse-derived scores (p less than .001) and significant-other-derived scores (p less than .001). We also compared scores for a group of nursing home patients (n = 68) on the Katz Activities of Daily Living (ADL) Scale, using data obtained from patients and their nurses. Again, the patient-derived scores were significantly higher than those from nurses (p less than .001). We conclude that data sources for determining patient functional ability are not interchangeable and that patients may overstate their functional abilities, whereas significant others may understate them, relative to judgments of skilled nursing personnel.

Impaired hearing in X-linked hypophosphataemic (vitamin-D-resistant) osteomalacia

We assessed the hearing of 25 patients with X-linked hypophosphataemic osteomalacia. Twelve patients had subjective hearing loss and 2 had had episodic tinnitus, deafness, and vertigo similar to that in Ménière's disease. On pure-tone audiometry, 19 patients were shown to have sensorineural hearing loss, 3 of whom had evidence of an added conductive element. Tests were done to delineate sensory (cochlear) from neural deafness. Analysis of the stapedius reflex threshold, percentage speech discrimination score, tone decay, and loudness recruitment showed a disturbance of cochlear function. The possible mechanisms responsible for this dysfunction are discussed in the light of pathologic characteristics of familial hypophosphataemia and its extraosseous manifestations. Sensorineural hearing loss, a previously unrecognised complication of familial hypophosphataemic osteomalacia, occurs frequently.

Developmental perspective of the Gilles de la Tourette syndrome

This paper concerned developmental perspectives of the Gilles de la Tourette Syndrome. Topics addressed included birth, developmental and family histories, and symptom picture. The neglected area of academic achievement was examined. Results of the first systematic investigation of neuro-psychological functioning of Tourette children undertaken in the United States was presented. Subjects were 13 diagnosed male Tourette patients between 10 and 13 yr. of age. Parents completed the Developmental History and Tourette Syndrome Questionnaires while subjects were administered the WISC-R, Wide Range Achievement Test, Bender-Gestalt, and Halstead Neuropsychological Test Battery for Children. There was no supporting evidence that pre-/postnatal trauma was significant in the etiology of the disorder. Again, evidence suggested a genetic component. Finally, academic difficulties appear related to the visuographic dysfunction noted on neuropsychological assessment.

UCLA hospice evaluation study. Methodology and instrumentation

An unbiased evaluation of hospice effectiveness requires a randomized controlled trial (RCT), but the implementation of such a design is difficult. This paper describes the methods of the only RCT to date and reports on the validity and reliability of scales selected or developed to assess attainment of hospice goals. The patients involved are those in a VA hospital in Los Angeles who have cancer and a prognosis of about 6 months and who consent. They and their significant others are interviewed periodically until the patient's death to measure such hospice variables as pain, depression, anxiety, satisfaction with care and the environment, activities of daily living, and bereavement effects. Many of the scales, including McGill Pain, CES-D Depression, and Satisfaction with Care scales, have been validated in other studies with similar samples. The authors' test-retest reliability analyses show that these scales are reliable with advanced cancer patients and their significant others with coefficients ranging from 0.77 to 0.97.

The outcome of hospitalization for acute illness in the elderly

The use of acute-care hospitals by the elderly is rising rapidly, particularly in the age group 75 and older. Any changes that will reduce the length of stay could result in considerable savings in health care costs. It is imperative to look at present policies and explore possible changes that could reduce costs by reducing the total hospital days. A study was conducted in a 290-bed county-founded community hospital in California that serves the majority of disadvantaged and poor elderly residing in an area with a population of approximately 300,000 persons. The objective was to determine what demographic, medical, and sociologic characteristics of elderly patients recorded at admission would be of value in predicting those most likely to change their functional status. It was found that the most important predictors of deterioration of function are (1) older age, especially 85+, and (2) abnormal mental status. Patients admitted from nursing homes had a longer than average length of stay, and those who survived (80 per cent) returned to a nursing home. It was concluded that routine assessment of elderly patients admitted for acute illness or injury could facilitate discharge planning by an early prediction of the level of care that will be required after discharge. This assessment should include preadmission mental and functional status; identification of causes for, and correction of, acute confusional states; and an assessment of the impact of the present illness or injury on future level of function following rehabilitation. This could result in a reduced length of average hospital stay.

Cultural factors affecting nursing home care for minorities: a study of black American and Japanese-American groups

In a pilot study of two nursing homes serving primarily different ethnic groups, differences were found in the importance black patients and their relatives attached to the ethnic character of the institution compared with respondents in a Japanese home. The latter placed more emphasis on all aspects of ethnic programming and homogeneity of patients and staff. The blacks placed more emphasis on access to family than on ethnic orientation per se.

Effect of timing of measles vaccination on compliance with immunizations during the second year of life

In 1976 the recommended time for routine measles immunization was changed from 12 to greater than or equal to 15 months of age. Because of the known decrease in compliance with immunizations given during the second year of life and the scheduling of an additional visit close to the time of the diphtheria-tetanus-pertussis (DTP) booster immunization, the potential benefit from this change might be offset by a decrease in compliance in securing both measles vaccination and DTP booster immunization. A study of the change in immunization compliance was carried out in a county health facility and in a prepaid medical group practice. Charts of 795 infants (395 born before and 400 born after the change) were reviewed to assess the rates of compliance with measles and with DTP immunizations. Administration of measles vaccine at a scheduled time decreased by 10% (0.05 less than P less than 0.06) at the public health facility after the change in 1976 and by 13% at the prepaid group practice (P less than 0.01). This difference evened out in the public health facility patients by age 2 years, but a 9% decrease was still apparent at the prepaid medical group. A similar pattern was seen in compliance with the DTP booster immunization at each site. Any benefit derived by an increased measles seroconversion rate apparently was offset by an overall decrease in compliance for both measles and DTP booster immunizations.

Ultrasound-guided catheter localization of intrahepatic abscesses--an aid in open surgical drainage

A catheter placed by the radiologist in a hepatic abscess before operation affords many luxuries to the surgeon. Percutaneous aspiration of the abscess provides material for Gram stain and culture, thereby allowing appropriate perioperative selection of antibiotics. The decompression provided gives the surgeon time to prepare the patient adequately for operation. Most important, use of the catheter as a guide to the abscess allows the surgeon to select the optimal approach to the liver and then proceed directly to the involved area. In this way operating time, blood loss, damage to uninvolved areas of the liver, and unnecessary contamination are kept to a minimum.

Physicians' attitudes toward female patients

The relative impact of a patient's sex and expressivity (expression of a personal problem) on attitudes of physicians toward patients was assessed using case simulations and questionnaires. Eight simulated cases were used that varied by presenting complaint, patient sex, and inclusion or exclusion of a personal problem. Two non-identical cases were read by each of 253 primary-care physicians, yielding 506 questionnaires for analysis. Of the physicians, 25 per cent believed women were likely to make excessive demands on physician time, although only 14 per cent believed this likely of men (p less than 0.01); women's complaints were judged more likely to be influenced by emotional factors (65 per cent versus 51 per cent in men, p less than 0.01), and were identified as psychosomatic more frequently than were men's (21 per cent versus 9 per cent, p less than 0.01). No sex differences were observed for tranquilizer prescriptions. Sex differences persisted when complaint and expressiveness were controlled; however, physicians' reactions to expressivity were strong enough to equalize male-female differences in some items. Although non-expressive women were more likely to receive a psychosomatic diagnosis than non-expressive men (14 per cent versus 2 per cent, p less than 0.01), expressive men and women were almost equally likely to receive psychosomatic diagnoses. Thus, differences in labeling occurred as a function of the patient's sex and expressivity. The effects of these differences on quality of care remain to be determined.

The future need for geriatric manpower in the United States

Additional medical manpower will be required to meet the growth in the elderly segment of the United States population over the next 50 years. This paper provides estimates of the needs for medical geriatric manpower under four different models: continuation of the status quo; academic geriatricians only; provision of care by academic and consultant geriatricians; and provision of care by academic, consultant, and primary-care geriatric practitioners. Each option is further analyzed in terms of three levels of delegation to nonphysician clinicians. We project the implications of these 12 patterns through the year 2030, assuming present usage levels and allowing for improved care of the elderly. The need for geropsychiatric care is explored separately. We think that geriatricians should provide improved care, including both consultant and primary care, to people aged 75 years and older, and that they should delegate a moderate amount of responsibility to nurse practitioners, physician assistants, and social workers. On the basis of these assumptions, and allowing for an academic role as well, we estimate that the United States will require between 7000 and 10,300 geriatricians by the year 1990; the best intermediate figure is about 8000.

Channeling health: a review of the evaluation of televised health campaigns

This article reviews efforts to assess the effectiveness of television programs on changing health behaviors. The relatively limited literature to date has featured primarily correlational studies which permitted no causal conclusions. The few experimental studies available present a mixed picture. Numerous methodologic problems beset any effort at assessment of effectiveness. Perhaps the greatest difficulty is operationalizing a design that permits true experimental manipulation on a relevant sample without contamination. The several methodologic problems and some potential means of surmounting them are discussed.

Phase II trial of cyclophosphamide, hexamethylmelamine, adriamycin, and cis-dichlorodiammineplatinum(II) combination chemotherapy in advanced ovarian carcinoma

A monthly four-drug regimen of cyclophosphamide, adriamycin, and cis-dichlorodiammineplatinum(II), each given iv of Day 1, and hexamethylmelamine, given orally on Days 1--14 (CHAP), was administered to 39 women with advanced epithelial ovarian carcinoma who had previously failed alkylating agent therapy. Of 35 evaluable patients with a measurable disease parameter, seven (20%) achieved a clinical complete response and ten (29%) achieved a clinical partial response. The median duration of complete response is greater than 9 months and the median duration of partial response is 4 months. Ninety percent of the patients required dose adjustments because of profound leukopenia, thrombocytopenia, or gastrointestinal intolerance. CHAP is an active but toxic regimen in the management of advanced ovarian cancer. The toxicity encountered reflected the intensity of the drug schedule as well as the combined influences of advanced stage of disease, poor nutritional and performance status, and prior therapy. The efficacy of this CHAP regimen warrants a controlled trial compared to other active drug programs.

Comparative studies of hemoperfusion devices. II. Pressure drop and flow uniformity tests

One resin-based hemoperfusion device and three charcoal-based hemoperfusion devices were tested to determine their pressure drop and flow uniformity characteristics. Measurements were made on pressure drop versus flow rate using distilled water and on pressure drop versus time using bovine blood. Effluent concentration curves obtained after the step-change introduction of a high molecular weight dye solution to each unit were used to determine the priming volumes of the devices and were interpreted to yield information regarding the uniformities of flow in each device. The pressure drop and priming volume values for the resin-based device were significantly higher than the corresponding values for the charcoal-based units.

Changes in utilization patterns in a National Health Service Corps community

Utilization patterns in two adjacent rural Utah counties were compared over a span of five years (1971-1976). In one, a three-physician National Health Service Corps site was established during the interval; the other went from one family physician to two during the same period. The Corps site showed an increase in physician utilization while the "control" county utilization remained unchanged. However, despite the increased utilization of physicians in the Corps site, fewer respondents identified a family physician, especially one located within the county. This is consistent with an interpretation that county residents were content to use Corps physicians, but saw them as transitory figures with whom they could form no permanent attachment. A second brief follow-up study a year later suggests that the community had already begun to acknowledge the Corps doctors as their family physicians.

Comparative studies of hemoperfusion devices. I. In vitro clearance characteristics

Drug adsorption studies were carried out using three charcoal-based and one resin-based hemoperfusion devices. They were the Sandev Hemocol unit, the Gambro Adsorba 300C unit unit, the Becton-Dickinson Hemodetoxifier, and the Extracorporeal Medical Specialties XR-010 Hemoperfusion column, respectively. Clearance versus time tests of up to six hours duration were performed using solutions of sodium salicylate, sodium barbital, and creatinine in a pH 7.4 buffer which were pumped through the columns at flow rates of either 100 or 200 ml/minute. Short term clearance tests were performed at various other flow rates to determine overall mass transfer resistances for the devices. Further analysis yielded values for the individual fluid-phase and solid-phase resistances. Studies were also done using sodium salicylate in bovine blood. The results provide information on typical adsorption capacities and drug removal rates for the four devices, and indicate the relative extents to which the solid and fluid phases control the drug uptake rates.