Correlation of Inferior Vena Cava Respiratory Variability Index with Central Venous Pressure and Hemodynamic Parameters in Ventilated Pigs with Septic Shock

[2-3] . In this study, the relation of pulse-induced contour cardiac output (PiCCO) hemodynamic parameters with the maximum inferior vena cava diameter (IVCmax), minimum inferior vena cava diameter (IVCmin), inferior vena cava respiratory variability index (IVCrvi), and CVP was studied in pigs with septic shock. Ten juvenile pigs (5 males and 5 females) weighing 30.28±1.80 kg were anesthetized by intraperitoneal injection of 3% pentobarbital sodium (30 mg/kg), intravenous injection of fentanyl (25 μg/kg) and rocuronium bromide (0.6 mg/kg) through an indwelling ear vein catheter and maintained by intravenous infusion of 3% pentobarbital sodium (5-10 mL/h) and fentanyl (10 μg/kg/h). The animals were placed at the supine position, tracheal intubation was performed, followed by mechanical ventilation in SIMV mode, with a tidal volume of 10-15 mL/kg, a respiratory rate of 12 breaths/min, an inspiration of 21% oxygen, a positive end-expiratory pressure of 3 cm H2O, an inspiratory:expiratory ratio of 1:1.5-1:2.0. A 6F-diameter catheter was inserted into the internal jugular vein for monitoring of CVP a PiCCO sensor and a PiCCO plus monitor for monitoring of temperature. A femoral artery was isolated into which a PiCCO thermodilution catheter was inserted and connected to the PiCCO plus monitor. An animal model of septic shock was established by injecting 50 mL of diluted E. coli endotoxin into the internal jugular vein (100 μg/kg). Septic shock was induced when the mean arterial pressure (MAP) decreased to 70% of the baseline value. The fluid resuscitation was carried out 6 h after the establishment of septic shock model. PiCCO hemodynamic parameters were measured before, during, 1 and 6 h after the establishment of septic shock model. The cardiac index (CI), global end-diastolic volume (GEDV), intrathoracic blood volume (ITBV), stroke volume variation (SVV), CVP, IVCmax, IVCmin, and IVCrvi were recorded. The IVCmax and IVCmin were measured at the end of inspiration and expiration respectively with a portable ultrasound machine. The IVCrvi was calculated according to the formula: (IVCmax – IVCmin) / IVCmax × 100%. The data are expressed as mean±SD (n=3) and analyzed using the SPSS 15.0 software. Relevant parameters before and after fluid resuscitation were compared by repeated ANOVA. The relation between different parameters was analyzed by Pearson correlation analysis. P<0.05 was considered statistically significant. The IVCmin was significantly different from the IVCrvi (P<0.001), but not from the IVCmax (P=0.097) before and after fluid resuscitation. The CVP, CI, GEDV, ITBV, and SVV were also significantly different before and after fluid resuscitation (P=0.016, P=0.040, P=0.002, P=0.001, and P<0.001, Table 1). The CVP was significantly correlated with the CI, GEDV, ITBV, SVV, IVCmax, IVCmin, and IVCrvi (r=0.922, r=0.707, r=0.734, r=-0.653, r=0.433, r= 0.816, r=-0.719; P<0.001, P<0.001, P<0.001, P<0.001, P=0.00, P<0.001, P<0.001, Figure 1). The IVCmax was significantly correlated with the SVV (r=-0.362, P=0.022), but not with the CI, GEDV, or ITBV (r=0.135,