Pulmonary arterial thermodilution, femoral arterial thermodilution and bioreactance cardiac output monitoring in a pediatric hemorrhagic hypovolemic shock model.

Aim: Bioreactance is a new non-invasive method for cardiac output measurement (NICOM). There are no studies that have analysed the utility of this technique in a pediatric animal model of hemorrhagic shock.

Methods: A prospective study was performed using 9 immature Maryland pigs weighing 9 to 12 kg was performed. A Swan-Ganz catheter, a PiCCO catheter and 4 dual surface electrodes were placed at the four corners of the anterior thoracic body surface. Shock was induced by withdrawing a blood volume of 30 mL/kg, and then after, 30 mL/kg of Normal saline was administered. Seven simultaneous measurements of cardiac index (CI) were made by pulmonary artery thermodilution (PATD), Femoral artery thermodilution (FATD), and NICOM before, during, and after hypovolaemia and during and after volume expansion.

Results: The mean difference (bias) of differences (limits of agreement) between PATD and FATD was 0.84 (-1.87-3.51)L/min/1.77 m(2), between PATD and NICOM was 1.95 (-1.79-5.69)L/min/1.77 m(2), and between FATD and NICOM was 1.06 (-1.40-3.52)L/min/1.77 m(2). A moderate correlation was found between PATD and FATD (r=0.43; P=0.01), but no correlation was found between bioreactance and either PATD or FATD. Hypovolemia and volume expansion produced important significant differences in CI as measured by PATD and FATD, while the changes with bioreactance were small and non significant.

Conclusions: PATD and FATD measurements showed similar responses to hypovolemic shock and volume expansion. Bioreactance persistently underestimates the CI and is not significantly altered by either inducing hemorrhagic shock, or later, through volume expansion. Bioreactance is not a suitable method for monitoring the CI in pediatric hemorrhagic shock.