Blood volume measurements using an integrated fiberoptic monitoring system in a porcine septic shock model

OBJECTIVES:To compare the accuracy of an integrated fiberoptic monitoring system using transpulmonary thermo-dye dilution technique to measure blood volume (BV) with standard method using chromium-51-tagged erythrocytes in septic shock. DESIGN:Prospective blinded animal laboratory study. SETTING:University department of anesthesiology. SUBJECTS:Thirty-five anesthetized and mechanically ventilated pigs (21.4 ± 2.2 kg) were investigated over a period of 6 hrs. INTERVENTIONS:Septic shock was induced with fecal peritonitis (0.75 g · kg per body weight autologous feces). A central venous catheter was used for injection of the indicator dyes. MEASUREMENTS AND MAIN RESULTS:BV was measured by detecting indocyanine green using a 4-Fr aortic catheter with an integrated fiberoptic and thermistor connected to a computer system for calculation of transpulmonary indicator dilution BV (BVTPID). Cr-tagged erythrocytes were used as standard method of BV measurement (BV-Cr). Hemodynamic treatment scheme was aimed at maintenance of a central venous pressure of 12 mm Hg. Data were analyzed using Bland-Altman analyses. One hundred and five data pairs of simultaneous BV measurements were yielded during hemodynamic stability with a mean BVTPID of 64.2 ± 17.8 mL · kg. Mean BV-Cr was 83.1 ± 17.0 mL · kg. Linear regression equation was BVTPID = 0.58 × BV-Cr + 15.8 (r = .56, p < .01). Mean bias was 18.9 mL · kg (95% confidence interval, 15.7–22.1 mL · kg), with limits of agreement of −13.9 to 51.7 mL · kg. CONCLUSIONS:Transpulmonary indicator dilution for blood volume measurement agrees moderately with standard method using Cr-tagged erythrocytes in porcine septic shock.