title: Catheter-based impedance measurements in the right atrium for continuously monitoring hematocrit and estimating blood viscosity changes; an in vivo feasibility study in swine.
abstract: Hematocrit is the most important determinant of whole blood viscosity and it affects thrombosis. As hematocrit can be measured accurately in vitro by using an electrical impedance technique, aim of the present study is to investigate the diagnostic potential of using this technique in vivo to continuously monitor hematocrit. Characteristics of a special catheter for in vivo measurement of electrical resistivity in blood in the right atrium are described. In five anesthetized swine hematocrit is monitored continuously with this catheter while different levels of hemoconcentration are induced. In addition, blood viscosity is increased by inducing 'acute phase' reaction the day before surgery, resulting in variable degree of elevated fibrinogen levels in the five swine. Good reproducibility of the resistivity measurements (S.D < 0.01) and excellent correlation between resistivity data in vivo and hematocrit levels in each swine are found (r2 = 0.95-0.99). Furthermore, stepwise regression analysis of data from all swine shows a highly significant contribution also of other important parameters of blood viscosity, such as fibrinogen, total protein and temperature (cumulative r2 = 0.97). Determining hematocrit continuously in vivo by electrical resistivity measurements with a catheter in the right atrium is feasible and these measurements correlate significantly also with other important parameters of blood viscosity.
authors.affiliation: Department of Cardiology, Thoraxcenter, Experimental Cardiology, Thoraxcenter, Erasmus MC Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands.
authors.forename: Gheorghe A
authors.initials: GA
authors.lastname: Pop
authors.forename: Zu-yao
authors.initials: ZY
authors.lastname: Chang
authors.forename: Cornelis J
authors.initials: CJ
authors.lastname: Slager
authors.forename: Bert-Jan
authors.initials: BJ
authors.lastname: Kooij
authors.forename: Elza D
authors.initials: ED
authors.lastname: van Deel
authors.forename: Liviu
authors.initials: L
authors.lastname: Moraru
authors.forename: Jan
authors.initials: J
authors.lastname: Quak
authors.forename: Gerard C
authors.initials: GC
authors.lastname: Meijer
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Duncker
mesh_terms: D000818:Animals; D016280:Atrial Function, Right / Q000502:physiology*; D001809:Blood Viscosity / Q000502:physiology*; D002408:Catheters, Indwelling; D017097:Electric Impedance; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004566:Electrodes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D005260:Female; D006400:Hematocrit / Q000295:instrumentation* / Q000379:methods; D018056:Hemorheology / Q000295:instrumentation* / Q000379:methods; D008297:Male; D009862:Online Systems; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity