Search

R EGIONAL CEREBRAL OXYGEN SATURATION (RSO2) depends on the balance between regional oxygen delivery and consumption. The factors that alter this relationship include global and regional cerebral blood flow, hemoglobin concentration, arterial oxygen saturation, and regional cerebral oxygen consumption. Near-infrared spectroscopy (NIRS) is a novel method used to determine RSO2 .1 This technique has been used predominantly in infants and children to determine cerebral oxygenation during extracorporeal membrane oxygenation. 2 Its application has been expanded for use during carotid endarterectomy and in operations involving cardiopulmonary bypass (CPB). 3,4 By providing continuous RSO2 monitoring, this technique may allow detection of changes that signal early cerebral hypoxia and thus allow for prompt therapeutic intervention to minimize risk of neurologic injury. This case report describes the use of continuous cerebral oximetry during coronary artery bypass graft (CABG) surgery in a patient with bilateral internal carotid artery occlusion.

Objective: To compare the cross-sectional area (CSA) of the right internal jugular vein (RIJV) with the left internal jugular vein (LIJV) using two-dimensional ultrasound and to measure the response to the Valsalva maneuver in both the supine and Trendelenburg positions. Design: Prospective and randomized. Setting: University-affiliated hospital. Participants: Fifty healthy adult volunteers. Interventions: The CSA of both the RIJV and LIJV was measured with a 5-MHz, two-dimensional surface transducer before and during a 10-second Valsalva maneuver with the subjects in the supine position, and then with the subjects in a 10° Trendelenburg tilt. Measurements and Main Results: After the baseline measurements were performed, the subjects were divided into two groups based on the CSA of the RIJV and LIJV. Group 1 had an LIJV CSA equal to or greater than that of the RIJV (n = 10) and group 2 had an LIJV CSA less than that of the RIJV (n = 40). Of the latter 40 patients, 17 (34%) had an LIJV CSA less than 50% of that of the RIJV. In both groups, the CSA of both veins increased significantly with the Valsalva maneuver, Trendelenburg tilt, and both maneuvers combined. Conclusion: The findings suggest that in one third of adults (34%), the LIJV is significantly smaller compared with the RIJV and, combined with operator inexperience, may influence the success rate and risk for complications. Thus, the use of ultrasound and maneuvers that increase CSA is suggested during LIJV cannulation.

To evaluate the effects of milrinone on middle cerebral artery blood flow velocity (Vmca) and pulsatility index (PI) during normocapnia and hyperventilation in adults after cardiopulmonary bypass (CPB).A prospective study.University-affiliated hospital and Veterans Affairs Medical Center.Twenty-five adults with left ventricular ejection fraction40% undergoing coronary artery bypass graft surgery.After separation from CPB, using transcranial Doppler ultrasonography, peak and mean Vmca and PI were recorded before and after the administration of 50 microg/kg of milrinone under normocapnia and with hyperventilation.Heart rate, arterial blood pressure, central venous pressure, and cardiac output were documented after each study period. Compared with baseline, milrinone increased peak Vmca by 20%, increased mean Vmca by 19%, and decreased PI by 16% (p0.001). Before the administration of milrinone, hyperventilation decreased peak Vmca by 20%, decreased mean Vmca by 26%, and increased PI by 24% (p0.01). After milrinone administration, hyperventilation also decreased peak Vmca by 22%, decreased mean Vmca by 21%, and increased PI by 19% (p0.01). Milrinone increased cardiac index and decreased mean arterial pressure and systemic vascular resistance (p0.05); however, heart rate and central venous pressure remained unchanged.The administration of milrinone increases cerebral blood flow after CPB most likely as a result of cerebral vasodilation. The response to hyperventilation seems to be partially preserved.

Objective: To identify the incidence of coronary-subclavian steal syndrome in patients undergoing noncardiac surgery. Design: Prospective. Setting: Veterans Affairs Medical Center and university-affiliated medical center. Participants: Adult patients with prior coronary artery bypass graft surgery and documented use of an internal mammary artery. Interventions: Bilateral simultaneous brachial blood pressures were determined noninvasively. The presumptive diagnosis of ipsilateral subclavian artery stenosis and coronary-subclavian steal syndrome was made if the systolic blood pressure differential was >20 mmHg. Measurements and Main Results: The presumptive diagnosis of ipsilateral subclavian artery stenosis based on a blood pressure differential was made in 6 of 86 (5%) patients screened. The diagnosis of coronary-subclavian steal syndrome was confirmed at cardiac catheterization by observing retrograde internal mammary artery flow in 3 patients or lack of internal mammary artery flow in 1 patient (3.4%). All 4 patients with angiographic confirmation had either angina or silent ischemia. Three patients had successful carotid subclavian bypass, and 1 patient refused surgery. Two patients had no evidence of myocardial ischemia and underwent their planned procedure without incident. Conclusion: Coronary-subclavian steal syndrome occurs with relative frequency in noncardiac surgery patients with prior coronary artery bypass graft surgery using internal mammary artery conduits. Bilateral blood pressure measurements should be routinely performed during the preoperative evaluation. A pressure differential >20 mmHg should suggest the possibility of coronary-subclavian steal syndrome. Copyright © 2001 by W.B. Saunders Company