Validation of cardiac output measurement by ultrasound dilution technique with pulmonary artery thermodilution in a pediatric animal model.

Novel COstatus system (Transonic Systems, Inc., NY), based on ultrasound dilution (UD), works off in situ arterial and central venous catheters in pediatric patients to measure cardiac output (CO). The purpose of the present study was to validate CO measurement by UD (COUD) with pulmonary artery (PA) thermodilution (COTD) in a prospective animal study. Ten anesthetized pigs (16-45 kg) were instrumented with pediatric PA, central venous, and peripheral artery catheters. For COUD measurements, normothermic saline (0.5-1.0 ml/kg body weight, up to a maximum of 30 ml) was injected into the venous limb of an arteriovenous loop that was connected between in situ catheters. For COTD measurements, 5-10 ml cold saline was injected into the PA catheter. Sixty-four averaged sets were obtained for comparison. COTD mean was 2.98 ± 1.21 l/min (range 1.33-6.29), and COUD mean was 2.68 ± 1.16 l/min (range 1.33-5.85). This study yielded a correlation r = 0.96, COUD = 0.91*(COTD) - 0.04 l/min; bias was 0.3 l/min with limits of agreement as -0.39 to 0.99 l/min; and the percentage error was 23.73% between the methods. CO measurements by UD agreed well with thermodilution measurements in the pediatric swine model.

Determination of cardiac output by ultrasound velocity dilution in normovolemia and hypovolemia in dogs.

OBJECTIVE: The purpose of this study was to compare CO measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in a canine model of acute hemorrhage. STUDY DESIGN: Prospective descriptive evaluation. ANIMALS: Twelve dogs (15-34 kg). METHODS: Dogs were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases and CO. The CO was measured by use of LiDCO and UDCO techniques. Measurements were obtained from each animal at baseline and during a low CO state (hemorrhagic state). Measurements were converted to cardiac index (CI = CO/BSA) values for statistical analysis. To measure CO using UDCO, a 20 mL bolus of 0.9% sodium chloride was administered and CO was calculated from the transient dilution of blood proteins created by the injection bolus. Hypovolemia was induced by withdrawing 40% of the blood volume until the mean arterial blood pressure (MAP) was stable at 40 mmHg for 10 minutes. Agreement was determined using Bland & Altman analysis and concordance correlation coefficients. RESULTS: Twenty-four comparisons were made. Lithium determinations of CI ranged between 7.5 and 1.3 L minute(-1) m(-2), and the mean overall difference between the two methods was -0.40 L minute(-1) m(-2). The mean relative bias was -17 ± 21% (limits of agreements: -59% to 25%). There was no significant effect of state of CI on bias or relative bias (p = 0.24 and p = 0.10, respectively). The concordance correlation coefficient between LiDCO and UDCO as 0.88 (p < 0.0001). CONCLUSIONS: When compared to lithium dilution, the UDCO technique is a viable method for measuring cardiac output in a model of normovolemia and hypovolemia in dogs.

Theory and in vitro validation of a new extracorporeal arteriovenous loop approach for hemodynamic assessment in pediatric and neonatal intensive care unit patients.

OBJECTIVES: No simple method exists for repeatedly measuring cardiac output in intensive care pediatric and neonatal patients. The purpose of this study is to present the theory and examine the in vitro accuracy of a new ultrasound dilution cardiac output measurement technology in which an extracorporeal arteriovenous tubing loop is inserted between existing arterial and venous catheters. DESIGN: Laboratory experiments. SETTING: Research laboratory. SUBJECTS: None. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In vitro validations of cardiac output, central blood volume, total end-diastolic volume, and active circulation volume were performed in a model mimicking pediatric (children 2-10 kg) and neonatal (0.5-3 kg) flows and volumes against flows and volumes measured volumetrically. Reusable sensors were clamped onto the arterial and venous limbs of the arteriovenous loop. A peristaltic pump was used to circulate liquid at 6-12 mL/min from the artery to the vein through the arteriovenous loop. Body temperature injections of isotonic saline (0.3-10 mL) were performed. In the pediatric setting, the absolute difference between cardiac output measured by dilution and cardiac output measured volumetrically was 3.97% +/- 2.97% (range 212-1200 mL/min); for central blood volume the difference was 4.59% +/- 3.14% (range 59-315 mL); for total end-diastolic volume the difference was 4.10% +/- 3.08% (range 24-211 mL); and for active circulation volume the difference was 3.30% +/- 3.07% (range 247-645 mL). In the neonatal setting the difference for cardiac output was 4.40% +/- 4.09% (range 106-370 mL/min); for central blood volume the difference was 4.90% +/- 3.69% (range 50-62 mL); and for active circulation volume the difference was 5.39% +/- 4.42% (range 104-247 mL). CONCLUSIONS: In vitro validation confirmed the ability of the ultrasound dilution technology to accurately measure small flows and volumes required for hemodynamic assessments in small pediatric and neonatal patients. Clinical studies are in progress to assess the reliability of this technology under different clinical situations.

Quantitative response of volumetric variables measured by a new ultrasound dilution method in a juvenile model of hemorrhagic shock and resuscitation.

OBJECTIVE: New volumetric variables of preload, such as total end-diastolic volume index (TEDVI) and active circulation volume index (ACVI) and central blood volume index (CBVI), may represent good indicators of preload and predictors of fluid responsiveness. During acute changes of intravascular volume these variables would allow a more accurate intervention. AIM: The aim of the present study was to investigate the changes in TEDVI, ACVI, CBVI in a juvenile model of hemorrhagic shock and resuscitation. METHODS: Twelve anaesthetized ponies (3-8 months of age) were studied at normovolaemia (BASE), after blood withdrawal to mean arterial pressure (MAP) of 40 mmHg (HEMO), after infusion of norepinephrine to reach a MAP of ± 10% of baseline (HE-NE), and after retransfusion of shed blood (RESU). TEDVI, ACVI, CBVI were measured by Ultrasound Dilution (UD) technology with CoStatus device. Data were analyzed using 1-way (ANOVA) followed by Bonferroni's multiple pairwise comparisons. Evaluation of dependence between CoStatus volumetric variables and stroke volume index (SVI) were performed using the linear regression analysis and calculating the r(2) coefficient of determination. RESULTS: TEDVI and ACVI changed significantly during HEMO and RESU status. NE administration induced MAP and CVP significant changes, whereas TEDVI and ACVI remained unchanged. CBVI showed high variability and seemed to be inconsistent on the identification of the volume status. In the correlation analysis, only TEDVI consistently correlated with SVI and volume induced SVI changes. CONCLUSIONS: In this animal model, TEDVI and ACVI were superior to CBVI in consistently reflecting hemorrhage. TEDVI but not ACVI and CBVI correlated with volume-induced changes in SVI. NE administration did not affect this correlation.