Biomedical subjects

C Wardrop

Publications and source records attributed to C Wardrop.

7 recordsLinked to original sources

PubMed2000

Measuring blood volume with fluorescent-labeled hydroxyethyl starch.

OBJECTIVES: To develop and evaluate a method for measuring blood volume using the dilution of a fluorescent-labeled hydroxyethyl starch. DESIGN: Laboratory and clinical investigation. SETTING: Biochemistry laboratory at the University of Cardiff. Hematology clinic, surgical ward and intensive care unit of the University Hospital of Wales. PATIENTS: Seventeen patients with suspected polycythemia. Eight patients who had undergone major surgery and/or were receiving intensive postoperative care. INTERVENTIONS: All surgical and postoperative care was provided by clinicians not involved in the study. Patients with suspected polycythemia were referred for blood volume measurement using labeled albumin and red blood cells. MEASUREMENT AND MAIN RESULTS: A proprietary brand of hydroxyethyl starch (Elohaes) was labeled with fluorescein isothiocyanate. Dilution of this compound in vivo was used for measuring blood volume, and the results were compared with those obtained using radiolabeled albumin and the considered criterion, radiolabeled red cells. The elimination of the labeled starch follows the same progress as that of the parent compound, indicating that the fluorescent tag is stable in vivo. The volume of distribution of the labeled starch is 2.5 mL/kg lower than that for labeled albumin (p = .05). Blood volume, measured from the dilution of fluorescent starch, is lower (4.9 mL/kg) than that measured with albumin (p = .048) but higher (6.61 mL/kg) than that measured with red blood cells (p = .0007). This latter difference may be even smaller at marginally higher doses of the fluorescent starch. CONCLUSION: These data support the view that hydroxyethyl starch provides a valid alternative to red cell labels as a means of calculating blood volume in patients. Labeling the starch with a fluorescent marker makes the assay procedure more sensitive and infinitely easier. The dose required is not high enough to affect the hemodynamic status of the patient.

Blood Volume↗

PubMed1999

Blood volume determination by the carbon monoxide method using a new delivery system: accuracy in critically ill humans and precision in an animal model.

OBJECTIVE: To evaluate accuracy and repeatability of blood volume determinations made by the carbon monoxide method, using a ventilator-driven administration system. DESIGN: Prospective within-patient comparison, using simultaneous measurements by two methods to determine accuracy. Prospective laboratory investigation in animals to estimate repeatability. SUBJECTS: For accuracy: Nineteen ventilated critically ill patients in a university hospital intensive care unit. For repeatability: Six anesthetized, mechanically ventilated normovolemic pigs because this is impossible to perform in humans. INTERVENTIONS: In the accuracy study, a small mass of carbon monoxide was administered via a closed breathing system and arterial blood samples were taken from existing cannulas. In the repeatability study, an intramuscular sedative was given, followed by an inhalational anesthetic induction and mechanical ventilation via a tracheal tube. Left axillary artery and external jugular vein cannulas were sited. Anesthesia was maintained using an intravenous infusion. Five sequential circulating hemoglobin and blood volume estimations were made using the carbon monoxide method. MEASUREMENTS AND MAIN RESULTS: The small carboxyhemoglobin increase produced by uptake of a small, known mass of carbon monoxide was used to estimate the circulating blood volume. Simultaneous measurement, using 51Cr-labeled red blood cells, was performed. Twenty measurements were made in 19 patients. The bias (mean difference between blood volume measurements by the two methods) was 397 mL (5.53 mL x kg(-1)) +/-415 mL (+/-5.95 mL x kg(-1)); the limits of agreement (mean difference +/-2 SD) were -433 mL and 1227 mL (-6.36 mL x kg(-1) and 17.42 mL x kg(-1)). Therefore, 95% of expected differences will lie between these limits. The mean blood volume was 75.8 mL x kg(-1) in the animals. The coefficient of variation of repeated estimates was 9.49%. Mean circulating hemoglobin mass was 7.31 mmol with a coefficient of variation of 10.18%. The mean hemoglobin concentration, by co-oximetry, was 5.014 mmol x L(-1), coefficient of variation, 2.99%. CONCLUSION: This arrangement is a potential bedside method of estimating blood volume and circulating hemoglobin mass. We have rendered the technique more acceptable clinically by creating a ventilator-driven administration system.

Administration, Inhalation↗

PubMed1993