254

Abstract

Introduction: Point of care ultrasound evaluates inferior vena cava (IVC) collapsibility and internal jugular vein (IJV) collapsibility to estimate intravascular volume status at the bedside. The reliability of the IVC and IJV collapsibility index in the setting of increased thoracic or intra-abdominal pressure remains unclear. Hypothesis: IVC and IJV collapsibility index correlate irrespective of changes in thoracic or intra-abdominal pressure for patients undergoing laparoscopic surgery. Methods: IRB approved prospective, observational study in an urban, academic tertiary care center for patients undergoing laparoscopic surgery. Three phases of sonographic scanning were performed: the pre-operative spontaneous ventilation (SV) phase, the intubated positive pressure ventilation (PPV) phase, and the increased intra-abdominal pressure (IAP) phase via laparoscopic insufflation to 15mmHg. IVC measurements were done at 1-2cm below the diaphragm in the anterior axillary line and IJV measurements were done at the level of the cricoid cartilage (IJV) during a complete respiratory cycle. Collapsibility index was calculated by max diameter-min diameter/max diameter x 100%. Chi-square, Fisher exact, t-test analysis and CORR procedure analysis were completed. Results: 16 patients were enrolled and 3 excluded for inability to obtain adequate ultrasound images. Mean age was 46 ± 15 years, BMI 29.5 ± 6.7kg/m2, 75% female and 69% African-American. Maximal IVC diameter was significantly smaller during increased IAP (16.5mm ±4.9) compared to SV (20.6mm ±4.8, p=0.04) and PPV (21.8mm ±5.6 p=0.01). Maximal diameter of IJV had no significant variability in the three phases. IVC and IJV collapsibility correlated in the setting of SV (r2= 0.86, p<0.01). IVC collapsibility had no correlation with IJV collapsibility in the setting of PPV (r2= 0.21, p=0.52) or increased IAP (r2= 0.26, p=0.42). Conclusions: Maximal IVC diameter is significantly smaller in the setting of increased intra-abdominal pressure. During laparoscopic surgery, the IJV and IVC collapsibility correlated only with spontaneous ventilation and not in the setting of increased thoracic or intra-abdominal pressure.