• Correlating IVC Measurements with Intravascular Volume Changes at Three Distinct Measurement Sites

      Yang, Kimberly; The University of Arizona College of Medicine - Phoenix; Wu, Teresa (The University of Arizona., 2014-04)
      Bedside ultrasound of the inferior vena cava (IVC) has grown to be an important tool in the assessment and management of critically ill patients. This study endeavors to examine which location along the IVC is most highly correlated with changes in intravascular volume status: (1) the diaphragmatic juncture (DJ) (2) two centimeters caudal to the hepatic vein juncture (2HVJ) or (3) left renal vein juncture (LRVJ). Data was collected in this prospective observational study on patients in the emergency department who were at least 16 years of age, being treated with intravenous fluids (IVF). Measurements of the IVC were recorded at each site during standard inspiratory and expiratory cycles, and again with the patient actively sniffing to decrease intrapleural pressures. IVF was then administered per the patient’s predetermined treatment, and the same six measurements were repeated after completion of fluid bolus. The difference in caval index (dCI) was calculated for all six data sets and correlated with the mL/kg of IVF administered. There was a statistically significant correlation between mL/kg of IVFs administered and dCI at all three sites (DJ: r = 0.354, p value = 0.0002; 2HVJ: r = 0.334, p value = 0.0003; LRVJ: r = 0.192, p value = 0.03). The greatest correlation between amount of fluids administered and dCI was observed along the IVC at the site 2 cm caudal to the juncture of the hepatic veins (2HVJ). This site is also where the largest change in diameter can be appreciated on ultrasound during intravascular volume resuscitation. Our data also suggests that every mL/kg of IVFs administered should change the dCI by 0.86-1.00%. This anticipated change in IVC diameter can be used to gauge a patient’s response to intravascular volume repletion.
    • Non‐invasive testing to determine cardiac or non‐cardiac etiology of dyspnea in the ED

      Morris, Jason; The University of Arizona College of Medicine - Phoenix; Wu, Teresa (The University of Arizona., 2014-04)
      Objectives: There were two main objectives of this study. The first was to determine the diagnostic threshold of hemodynamic values derived from impedance cardiography (ICG) and whether these thresholds are sex specific in determining the etiology of shortness of breath (dyspnea) in patients presenting to the emergency department (ED). The second was to compare ICG hemodynamic values with the results of bedside cardiothoracic ultrasonography and B-type natriuretic peptide (BNP) levels in patients with dyspnea in the ED. Methods: A prospective cohort of 50 adult patients presenting to the Maricopa Medical Center ED with dyspnea were evaluated using ICG, bedside cardiothoracic ultrasound, and BNP to determine the etiology of their complaint. The final etiology was determined through review of the treating practitioner’s final diagnosis and evaluation of the data available from the patient’s ED visit. Cardiac and non-cardiac groups were then compared to determine the accuracy, sensitivity, and specificity of ICG, bedside cardiothoracic ultrasound and BNP in identifying the etiology of their complaint. Results: BNP at a threshold of 164 pg/mL proved to be the most accurate with a sensitivity of 84.21%, a specificity of 79.17% and an area under the curve (AUC) of 0.8684 when plotted on a receiver operating characteristics (ROC) curve. Right ventricle diameter during systole was the most accurate bedside ultrasound parameter; at a threshold of 1.71 cm it showed a sensitivity of 77.78%, a specificity of 60.00% and an AUC of 0.7489. Heather index (HI) was the most accurate ICG parameter; at a threshold of 9.2 Ohm/sec2 it showed a sensitivity of 72.41%, a specificity of 85.00%, and an AUC of 0.8405. Only HI showed a significant difference between male and female patients. HI in females at a threshold of 10.4 Ohm/sec2 was 87.50% sensitive and 87.50% specific with an AUC of 0.9297. In males a HI threshold of 6.9 Ohm/sec2 was 69.23% sensitive and 66.67% specific with an AUC of 0.7564. Conclusion: Bedside cardiac ultrasound was technically challenging and the least accurate modality. ICG demonstrated some sex specific thresholds and while an easy to use modality, it was slightly less accurate than BNP which proved to be a simple and accurate modality for determining a cardiac or non-cardiac etiology of dyspnea.