IRB-HSR# 14296 The Use of the Intrathoracic Pressure Regulator (ITPR) to Improve Systemic Blood Pressure in Patient Undergoing CABG Surgery

Briefly, after the induction of anesthesia and the placement of TEE, hemodynamic variables (pulmonary and systemic blood pressure, central and pulmonary venous pressure, cardiac output, calculated SVR, etc.) will be collected. In addition, left ventricular performance (including estimates of LVEDV, LVESV, EF, FAC, etc.) will be assessed using TEE. Once these baseline data are recorded, the ITPR will be inserted in the anesthesia circuit and activated to provide -9 mmHg ETP. After the ITPR has been active for at least two minutes, the same hemodynamic and TEE data obtained above will be gathered. After the data is recorded, the ITPR will be disconnected and no further interventions will be made. In addition to the hemodynamic and echocardiographic data described above, an arterial blood gas will be obtained from the pre-existing radial artery catheter during the on- and off- states.

Finally, the TEE examination will be recorded on videotape or DVD. A second echocardiographer, blinded to patient and ITPR status will review each echocardiogram and assess left ventricular performance. In addition to the data derived at the time of testing, the second echocardiographer will assess, if possible, changes in EF using Simpson's method of disks is used to calculate the LV volume.

This is a proof of concept/feasibility study designed to test the primary hypothesis that use of the ITPR will result in increased systemic blood pressure and cardiac output in patients undergoing CABG surgery. The effect of the ITPR on other secondary indicators of cardiac performance will also be examined. These include but are not limited to left ventricular end diastolic volume (LVEDV), ejection fraction (EF), left ventricular end systolic volume (LVESV), and fractional area change (FAC) as assessed by echocardiography, pulmonary artery pressure, and calculated systemic vascular resistance (SVR).

The ITPR is an FDA-approved device intended to increase circulation and blood pressure in hypovolemic and cardiogenic shock. The device is inserted within a standard respiratory circuit between the patient and the ventilator. It functions by decreasing intrathoracic pressure during the expiratory phase to subatmospheric levels after each positive pressure ventilation. The decrease in intrathoracic pressure creates a vacuum within the thorax relative to the rest of the body thereby enhancing blood return to the heart and consequently increasing cardiac output and blood pressure. Activation of the device is also accompanied by a decrease in SVR. The end result is a device that simultaneously improves cardiac output by increasing LVEDP/LVEDV and decreasing SVR while increasing coronary perfusion pressure by increasing blood pressure and decreasing LVESP/LVESV.1-8

Eligibility Criteria:
Inclusion Criteria:

* 1. patients presenting for elective CABG with planned intraoperative TEE 2. age 18 years of age and older 3. informed consent has been obtained

Exclusion Criteria:

* 1. Patients with planned valve surgery (valve or CABG + valve) 2. patients with a contraindication to transesophageal echocardiography (TEE); including patients with extensive esophageal or gastric disease. Relative contraindications include esophageal varices, Barrett's esophagus, Zenker's diverticulum, and postradiation therapy of the esophageal area.

  3. patients requiring IABP or VAD pre-operatively 4. emergent CABG 5. pneumothorax 6. hemothorax 7. uncontrolled bleeding 8. uncontrolled hypertension defined as SBP \> 180 mmHg at the time of surgery