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P Malek

Publications and source records attributed to P Malek.

At least 19 recordsLinked to original sources
PubMed1998

Accuracy and precision of access recirculation measurements by the hemodynamic recirculation monitor.

The hemodynamic monitor (HDM) is a device that uses magnetic principles to accurately measure access recirculation during hemodialysis. The measurement is based on differential conductivity between arterial and venous blood flow rates in the dialysis blood tubing sets. One milliliter of hypertonic saline is injected into the venous line of the blood tubing set as a conductivity "tracer." As the tracer enters the patient, the presence of access recirculation causes a percentage of the hypertonic saline to recirculate into the arterial line and is detected and quantified by the HDM; the percentage of access recirculation is calculated in under 1 minute. Clinical studies were performed in two centers on 106 patients with various forms of blood access (eg, arteriovenous fistulae, Gore-tex grafts [WL Gore and Associates, Flagstaff, AZ], Permcaths [Quinton Instrument Co, Bothell, WA], subclavian catheters). Access recirculation was detected under routine dialysis conditions in only 13 patients. In the remaining cases, attempts at inducing access recirculation were made by reversing the arterial and venous lines and/or increasing the blood pump to its maximum sustainable rate for a given patient. A 15-minute protocol was then instituted. Three blood samples (arterial, venous, and "peripheral" [stop-flow technique]) were first obtained to determine urea measurements and for subsequent calculation of access recirculation; immediately afterward, an HDM recirculation measurement was recorded to allow correlation of urea and HDM access recirculation results (accuracy). Two further HDM access recirculation measurements were made to analyze the precision or repeatability of the HDM test. This protocol was attempted up to three times in each patient on different dialysis days. Two hundred fifty-nine studies were made, and a strong linear correlation was obtained between urea and HDM results (r = 0.94, slope 0.95) over a range of access recirculation (5% to 60%) demonstrating accuracy. Repeated HDM access recirculation results showed a characteristic SD of 1.8% over the whole range of values, demonstrating a precision superior to the 6% expected using the urea method. When zero access recirculation was indicated by the HDM, "ground truth" tests were performed by injecting 1 mL of hypertonic saline (HS) into one injection port of the blood tubing set then 0.1 mL of HS into the other to simulate 10% access recirculation; the mean results were 9.96%+/-1.59% (+/-SD; n = 93), confirming the accuracy of the method.

Arteriovenous Shunt, Surgical↗
PubMed1997

Hemodialysis access blood flow rates can be measured by a differential conductivity technique and are predictive of access clotting.

Blood flow in peripheral arteriovenous fistulae and grafts as used for hemodialysis access can be derived from measurements of the amount of access recirculation induced by reversing the dialysis blood lines and a knowledge of the dialyzer blood flow rate. The Hemodynamic Monitor (HDM; GAMBRO Healthcare, Lakewood, CO) is a device that uses magnetic principles to accurately and precisely measure access recirculation during hemodialysis. The measurement is based on differential conductivity between arterial and venous blood flows in the dialysis blood tubing sets following the injection of hypertonic saline into the venous line as a conductivity tracer. Clinical studies were performed on 41 patients from two centers who had arteriovenous fistulae (25 patients) or Goretex grafts (16 patients; W.L. Gore & Associates, Flagstaff, AZ); each patient was studied on two successive dialysis days under variable conditions of dialyzer blood flow, and multiple measurements were made according to a standard protocol. The protocol involved temporarily reversing the arterial and venous lines, then performing an HDM recirculation test and recording the result along with the dialyzer blood flow rate as per the machine blood pump setting. The access blood flow rates measured 1,125+/-581 mL/min (mean+/-SD) on day 1 and 1,140+/-680 mL/ min on day 2 (P > 0.05 [NS]), with an absolute range of 221 to 3,118 mL/min. These flow rates are similar to those measured by other techniques. There was an excellent correlation between access blood flow rates measured in individual patients on days 1 and 2, even in a subset of 13 patients who had the dialyzer blood flow rates altered by > or =100 mL/min, suggesting the independence of access from dialyzer blood flow rates. Analysis of repeated measurements of access blood flow under identical conditions showed a characteristic standard deviation from the mean across the patient population of 7.89%, indicating that the HDM results are repeatable in clinical application. The influence of the measured access blood flow on the outcome of that access was determined after an 8-month follow-up period. Of the 41 accesses, nine were lost to clotting; seven of 14 that had initial blood flow rates less than 750 mL/min clotted, while only two of 27 with flow rates greater than 750 mL/min subsequently clotted (P = 0.005). The data show that the HDM can provide clinically important information on access blood flow.

Arteriovenous Shunt, Surgical↗
PubMedDate not supplied

The mental health patient profile: does it change primary care physicians' practice patterns?

BACKGROUND: We conducted a prospective trial randomizing 75 physicians to either a control or intervention arm to evaluate the impact of providing patient-reported information on anxiety and other mental health symptoms and disorders to primary care physicians. METHODS: Five hundred seventy-three patients of the study physicians who met entry criteria were randomized to either usual care or usual care supplemented with feedback of patient-reported mental health information to physicians. This mental health information was derived from initial patient-reported questionnaires completed in waiting rooms of physicians contracted to a mixed-model health maintenance organization in Colorado. Main outcome measures included impact of intervention on rates of (1) chart notation of anxiety, depression, or other mental health diagnoses or symptoms; (2) referral to mental health specialists; (3) prescription of psychotropic medications; (4) hospitalization; and (5) office visits during a 5-month observation period. RESULTS: Physicians receiving feedback on previously unrecognized and untreated anxiety patients were more likely to make chart notations (adjusted odds ratio [AOR] = 2.51, 95 percent confidence interval [CI] = 1.62-3.87), to make referrals to mental health specialists (AOR = 3.86, 95 percent CI = 1.63-9.16), and to see patients for more frequent outpatient visits (AOR = 1.73, 95 percent CI = 1.11-2.70). Use of psychotropic medications and rate of hospitalizations did not differ significantly. CONCLUSIONS: Providing patient-reported mental health information to primary care physicians resulted in increased recognition and referral rates for previously unrecognized and untreated anxiety patients, plus an increase in primary care visits, without concomitant increases in the use of psychotropic medications or rate of hospitalizations.

Adult↗