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Biomedical subjects

C A Steward

Publications and source records attributed to C A Steward.

8 recordsLinked to original sources
PubMed1999

Measuring total body water in peritoneal dialysis patients using an ethanol dilution technique.

UNLABELLED: Measuring total body water in peritoneal dialysis patients using an ethanol dilution technique. BACKGROUND: The accuracy with which total body water (TBW) is estimated is a direct determinant of the reliability of Kt/V urea measurements in peritoneal dialysis (PD) patients. Ethanol dilution has been previously shown to be a reliable measure of TBW. Advances in breath alcohol technology make this a feasible clinical tool. METHODS: We gave 19 fasting chronic PD patients 0.3 g/kg of ethanol (EtOH) orally on two separate occasions. Breath alcohol concentrations (BrACs), determined by dual-beam infrared analysis, were recorded at baseline and periodically thereafter until BrACs were less than 0.01%. The TBW was then determined by standard pharmacokinetic techniques. RESULTS: TBW measurements were reproducible, with a mean between-run difference of -0.004 liter/kg (95% limits of agreement -0.040 to 0. 032 by Bland-Altman). The Watson equations tended to underestimate TBW, with a mean difference (EtOH - Watson) of +3.0 liters (SD 4.0 liters, P = 0.004) and a mean absolute difference of 4.1 liters (SD 2.7 liters, range -4.4 to 9.5 liters). Kt/V was calculated from dialysate and urine collection, using V as determined from TBW estimates from EtOH and Watson. The mean Kt/V(EtOH) was 2.31 (SD 0. 50) compared with 2.46 (SD 0.52) using Watson. The mean absolute difference between the two Kt/V estimates was 0.26 (SD 0.20, range -0.87 to 0.57), with Kt/V overestimated by Watson in 14 patients. EtOH was well tolerated, and the procedure was completed in about four hours. CONCLUSIONS: Measuring V by the BrAC technique does not require blood sampling, is reliable, and is reproducible. It is a potentially useful method for a periodic determination of volume that may allow for more accurate Kt/V measurement in PD patients.

Administration, Oral↗
PubMed1998

Pharmacokinetics of intraperitoneal fluconazole during continuous cycling peritoneal dialysis.

OBJECTIVE: To investigate the pharmacokinetic characteristics of intraperitoneal fluconazole in patients undergoing continuous cycling peritoneal dialysis (CCPD). DESIGN: Prospective, nonrandomized, single-dose, open-label study. PARTICIPANTS: Five noninfected volunteer CCPD patients. INTERVENTIONS: Patients received a single dose of intraperitoneal fluconazole 200 mg during their long daytime dwell. Blood samples were collected before and 1, 3, 6, 12 (end of first dwell), 24 (after overnight cycling), 48, 72, 96, and 120 hours after dosing. Used dialysate was collected throughout the study. Unless the patient was anuric, urine was collected for the first 48 hours. MAIN OUTCOME MEASURE: Fluconazole concentrations were assayed by gas-liquid chromatography. Pharmacokinetic parameters were calculated using standard noncompartmental techniques. RESULTS: The bioavailability of intraperitoneal fluconazole was 96% +/- 2% over a 12-hour dwell, absorption half-life was 2.5 +/- 1.2 hours, serum elimination half-life was 71.65 +/- 12.76 hours, and volume of distribution was 0.66 +/- 0.13 L/kg. Peritoneal clearance was 5.96 +/- 0.93 mL/min and proportional to total dialysate volume. Renal clearance was proportional to renal creatinine clearance. CONCLUSIONS: Current treatment guidelines for fungal peritonitis suggest fluconazole 200 mg intraperitoneally every 24 hours. Our data suggest that this dose, administered every 48 hours, is more than sufficient to maintain serum and peritoneal concentrations above the minimum inhibitory concentration for most Candida spp. Other factors, such as residual renal function and dialysis prescription, may also need to be considered.

Adult↗
PubMed1998

Pharmacokinetics of vancomycin when administered during high flux hemodialysis.

This study was undertaken to evaluate the pharmacokinetics of relatively high-dose vancomycin when administered during high-flux hemodialysis using a polysulfone membrane (F-80, Fresenius). Five noninfected, anuric patients received a single dose of 25 mg/kg of vancomycin infused during hemodialysis at a rate of one gram per hour and timed such that the end of the infusion coincided with the end of dialysis. Blood samples were drawn during the infusion, up to six hours after the end of dialysis and then prior to the next three dialysis treatments. Spent dialysate was collected during the infusion. Samples were analyzed using the EMIT assay. The percent of vancomycin lost during the first dialysis session ranged from 39.1 to 55.1% (mean, 45.7+/-6.4). The concentration of vancomycin at 6 hours after hemodialysis ranged from 18.2 to 45.1 mg/L (mean, 29.6+/-10.0 mg/l). Dialysis clearance ranged from 96.1 to 158.1 ml/min (mean, 130.7 +/-30.0 ml/min). One week after dosing, serum concentrations ranged from 8.14 mg/l to 10.1 mg/l (mean, 9.0+/-1.0 mg/l). This study suggests than an initial dose of 25 mg/kg of vancomycin, given during high-flux dialysis, may provide adequate serum concentrations in anuric hemodialysis patients for up to seven days. This dosing scheme reduces inconvenience to the patient and staff, and potentially can reduce nursing costs associated with post-dialysis administration; its cost is minimal. At this point, subsequent dosing is best determined by therapeutic drug monitoring.

Adult↗
PubMed1997

Validation of a revised slow-stop flow recirculation method.

Slow flow/stop flow methods have replaced the three needle technique as methods of choice for measuring recirculation. However, the time delay after reducing blood flow may affect the BUN in the systemic (slow flow/stop flow arterial line) sample and therefore limit the accuracy of this methodology. It has been observed that recirculation does not occur in a properly cannulated access unless the access blood flow rate is less than the dialyzer blood flow rate (BFR). This suggests that the systemic sample could be obtained at a higher than usual blood pump rate. We studied 50 patients and compared a revised slow-stop flow (S/SF) recirculation technique in which the systemic sample was drawn after the blood pump rate was reduced to 120 ml/min for 10 seconds and then stopped, to a non-urea based method that utilized indicator velocity dilution (IVDM). Seven patients were found to have recirculation by IVDM; all had recirculation by S/SF of more than 10% (minimum 16.7%) and an access BFR that was less than the dialyzer BFR. In the 43 patients without recirculation by IVDM, the mean recirculation by S/SF was 1.9 +/- 3.2% (mean +/- SD). Five patients without recirculation by IVDM had more than 5% recirculation by S/SF (range, 5.9 to 8.3%). Although there was a small systematic tendency to overestimate recirculation, this modified urea based method was still able to detect recirculation with good reliability. Single values above 10% are highly likely to indicate the presence of true recirculation. Repeated values over 5%, are also likely to be significant, indicating the presence of true recirculation and its clinical correlate, marginal access blood flow.

Blood Circulation↗
PubMed1995

A comparative study of seven measures of patient satisfaction.

The acceptability of satisfaction as a quality indicator is qualified by several well known measurement problems. This study examines the variability in satisfaction evaluations related to different measurement methods and the effect of response biases on reported satisfaction. Satisfaction evaluations using seven different, commonly used measures of patient satisfaction were obtained from the same sample of respondents. The seven measures were: 1) a global measure of satisfaction using a visual analogue scale; 2) a multidimensional measure of satisfaction based on the Patient Satisfaction Questionnaire using an evaluation response format (poor, fair, good, very good, excellent); 3) a two-item overall evaluation of quality using the evaluation response format; 4) a six-item attitude measure of general satisfaction using a five-point Likert agree-disagree response format; 5) a four-item attitude measure of satisfaction with physician, using the agree-disagree response format; 6) a four-item measure of behavioral intention; and 7) willingness-to-pay in dollars. The percentage of favorable evaluations of care ranged from 63% to 82% across six of the seven measures. Willingness-to-pay does not appear to be a valid measure of satisfaction. Correlations were highest between measures with similar response formats. Although an oppositional response bias was not found, a very substantial acquiescent response bias was detected. Acquiescence reduced the internal consistency of three multiple-item measures, the general and physician attitude and behavioral intention measures, to levels unacceptable even for group comparisons. Between highly and nonacquiescent respondents, levels of satisfaction were somewhat lower for the multidimensional measure of satisfaction and significantly lower for the two attitude satisfaction measures. Highly acquiescent respondents were older, less well educated, and in poorer health than nonacquiescent subjects. Results of satisfaction evaluations dependent on the measurement method used, and unreliability of measurement may be a significant problem in satisfaction measurement, especially for the oldest and most ill patients.

Adult↗
PubMed1993

The importance of patient preferences in the measurement of health care satisfaction.

The idea that patients will be more satisfied with health care services that are delivered to meet their preferences is central to the concept of health care marketing. Health care providers increasingly use market segmentation and target marketing to optimize the fit between their services and the consumers who receive them. This study evaluates one model for incorporation of patient preferences into the measurement of satisfaction. Using multiple regression analysis, evaluations of three dimensions of health care satisfaction, interpersonal care, technical quality, access to care accounted for 63% of the variance in overall satisfaction. Inclusion of preferences, defined as importance ranks of each dimension, did not improve ability to predict satisfaction. Four preference segments were identified: interpersonal care seekers, access/quality seekers, access seekers and quality seekers. These four subgroups differed significantly on a number of sociodemographic, health status and health service use characteristics but no significant differences were found in satisfaction between preference segments. Patient satisfaction can best be measured as quality evaluations of dimensions without regard to preferences. In considering the merits of market segmentation and target marketing, alternative satisfaction models that link preferences to health care satisfaction or the possibility that preference targeting does not lead to greater satisfaction should be evaluated.

Consumer Behavior↗