Cuff occlusion on the left upper arm increases flow of the left internal mammary artery and bypass flow to the left anterior descending artery.

Purpose: Changes in vascular resistance in the left forearm may affect the flow of left internal mammary artery (LIMA)- to left anterior descending artery (LADA) bypass, because the LIMA is a major branch of the subclavian artery. We studied the effects of occlusion of the left upper arm on blood flow of LIMA-to-LADA bypass in patients undergoing coronary artery bypass grafting (CABG).

Methods: In ten patients, the blood volume shed from LIMA with the distal end open (LIMA free flow) was stored for 1 min before and during cuff inflation in CABG surgery. LIMA-LADA bypass flow was measured with ultrasonic flow-metry before and after cuff inflation on the left upper arm in an other ten patients. Mean arterial blood pressure (MAP), heart rate (HR), and electrocardiograms (ECGs) were monitored throughout the studies.

Results: LIMA free flow (ml x min(-1)) increased from 50.3 +/- 7.1 to 60.9 +/- 8.4 (P < 0.01) at the end of 1-min cuff inflation. LIMA-LADA bypass flow (ml x min(-1)) increased from 31.4 +/- 3.7 to 39.7 +/- 4.0 (P section sign 0.05) at 1 min after cuff inflation. MAP, HR, and ST segments on ECGs did not show any significant changes related to measurement times.

Conclusion: LIMA-LADA bypass flow increased after cuff inflation on the left upper arm and returned to the baseline values after cuff deflation. Anesthesiologists should be aware of this relationship between local vascular resistance and bypass flow for the evaluation of LIMA-LADA anastomosis.