Low systemic vascular resistance state following off-pump coronary artery bypass grafting

To determine the prevalence, hemodynamic characteristics, and risk factors for low systemic vascular resistance (SVR) state following after off-pump coronary artery bypass (OPCAB).

SVR data could be obtained for 116 OPCAB patients. Low SVR was defined as an indexed systemic vascular resistance (SVRi) of <1,800 dyne x s/cm(5) x m(2) at the end of operation. Hemodynamic data were recorded preoperatively, at the end of operation, just after entering ICU, and the following morning.

Low SVR state was noted in 54 of 116 patients (53%). The SVRi values in low-SVR and non-low-SVR patients were 1,406+/-253 and 2,326+/-509 dyne x s/cm(5) x m(2) at the end of operation (p<0.0001). Increased CI level, decreased MAP level, but unchanged CVP level was observed postoperatively in the low-SVR patients. The increase in CI and decrease in MAP were maximal at the end of operation. Patients with low SVR were more likely to have a higher body mass index (24.5+/-3.6 vs. 22.9+/-2.9; p=0.013) and to be male (82% vs. 62%; p=0.036) than no-low-SVR patients. In low-SVR patients, fluid balance was more positive intraoperatively (3,537+/-1,411 vs. 3,068+/-1,597; p=0.09), but more negative at 6 hours postoperatively (-136+/-978 vs. 234+/-844; p=0.034) and 12 h postoperatively (-282+/-1,321 vs. 268+/-1,238; p=0.024).

Low SVR state, a probable manifestation of systemic inflammatory response (SIRS), is common in patients who have undergone OPCAB. For these patients it is more reasonable to maintain MAP with vasopressors by restoring vascular tone, than by volume loading.