Near-infrared spectroscopy to assess microvascular dysfunction: A prospective pilot study in cardiac surgery patients.

Purpose: The diagnosis of microvascular dysfunction remains challenging after cardiac surgery. We hypothesized that peripheral near-infrared spectroscopy (NIRS) monitoring in combination with a vascular occlusion test could reliably assess postoperative microvascular dysfunction in that setting.

Materials And Methods: Twenty-two patients undergoing cardiac surgery with cardiopulmonary bypass and 10 healthy volunteers were prospectively investigated. Relevant NIRS parameters (regional tissue oxygen saturation, desaturation, and resaturation rates) were recorded the day before surgery (D-1), at the arrival in the intensive care unit (postoperative day [POD] 0) and on POD 1 and POD 2.

Results: No difference in NIRS parameters was found at baseline between healthy volunteers and cardiac surgical patients. Absolute values of regional tissue oxygen saturation significantly increased at POD 0 and POD 1 when compared with D-1: 78% (75%-81%) and 75% (73%-78%) vs 68% (64%-72%), P < .001. No statistical difference was evidenced within the postoperative period in desaturation and resaturation rates compared with D-1: desaturation rate, 0.11% · s(-1) (0.08-0.14) and 0.15% · s(-1) (0.08-0.22) vs 0.14% · s(-1) (0.10-0.17), P = .233, and resaturation rate, 0.76% · s(-1) (0.41-1.11) and 0.77% · s(-1) (0.53-1.02) vs 0.79% · s(-1) (0.61-0.97), P = .453. The use of postoperative norepinephrine infusion did not change the results.

Conclusions: Peripheral NIRS monitoring in combination with a vascular occlusion test failed to assess cardiopulmonary bypass-induced microvascular dysfunction.