Microvascular Reactivity in Cardiac Surgery

Study Overview
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Brief Summary
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Microcirculatory disturbance occurs most seriously during cardiopulmonary bypass (CPB) in cardiac surgery. If microvascular reactivity compensates for microcirculatory disturbance during CPB, tissue hypoxemia may be minimized. On the other hand, tissue hypoxemia may develop and lead to poor clinical outcomes. The primary aim of this study was to assess whether microvascular reactivity during CPB can predict major adverse events (MAE) within 30 days after cardiac surgery. This prospective, observational, single-center study was conducted on 115 patients who underwent elective on-pump cardiac surgery. The vascular occlusion test (VOT) with near-infrared spectroscopy was performed five times for each patient, before the induction of general anesthesia (baseline, T0), 30 min after the induction of general anesthesia (T1), 30 min after applying CPB (T2), 10 min after injection of protamine (T3), and after sternal closure (T4). Sequential Organ Failure Assessment (SOFA) and Acute Physiologic and Chronic Health Evaluation (APACHE) II scores and the length of ventilator care, intensive care unit stay, and hospital stay were recorded. Postoperative MAE within 30 days after surgery was also recorded.

Detailed Description
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The VOT was performed five times in each patient, before the induction of general anesthesia (baseline, T0), 30 min after the induction of general anesthesia (T1), 30 min after applying CPB (T2), 10 min after injection of protamine (T3), and after sternal closure (T4). Before induction of anesthesia, an NIRS sensor (INVOS® 5100C Cerebral/Somatic Oximeter; Medtronic, Minneapolis, MN, USA) was placed on the thenar eminence and an automated tourniquet (A.T.S® 3000 Automatic Tourniquet System; Zimmer Inc., Warsaw, IL, USA) was placed around the upper arm. The arterial catheter was placed in the contralateral radial artery and the baseline blood pressure was measured. When the baseline tissue oxygen saturation (StO2) was stabilized, the automatic tourniquet was inflated to 50 mmHg over the patient's baseline systolic blood pressure and maintained for 5 min. After the 5-min ischemic period, the tourniquet rapidly deflated to 0 mmHg. StO2 data were continuously recorded during the VOT procedure. Baseline StO2, minimum StO2 during the 5-min inflation of the tourniquet, and maximum StO2 during deflation of the tourniquet were obtained. The occlusion slope and recovery slope were calculated based on the measured StO2 data. The occlusion slope, which is related to oxygen extraction, was defined as the slope of the StO2 descent to the lowest value. The recovery slope, which is related to microvascular reactivity, was calculated from the deflation of the tourniquet until the recovery of StO2 to the highest value.

Official Title
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Microvascular Reactivity as a Predictor of Major Adverse Events in Patients With On-pump Cardiac Surgery: A Prospective Observational Study

Conditions
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Cardiac Disease

Intervention / Treatment
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* Diagnostic Test: vascular occlusion test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: adult patients aged >18 years elective on-pump cardiac surgery Exclusion Criteria: pregnancy inability to tolerate VOT (e.g., patients with arm deformities, arteriovenous shunts, burns)adult patients aged >18 years scheduled for elective on-pump cardiac surgery refusal to participate in the study

Ages Eligible for Study
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Minimum Age: 19 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Diagnostic Test: vascular occlusion test|The VOT was performed five times in each patient, before the induction of general anesthesia (baseline, T0), 30 min after the induction of general anesthesia (T1), 30 min after applying CPB (T2), 10 min after injection of protamine (T3), and after sternal closure (T4). Before induction of anesthesia, an NIRS sensor was placed on the thenar eminence and an automated tourniquet was placed around the upper arm. The arterial catheter was placed in the contralateral radial artery and the baseline blood pressure was measured. When the baseline tissue oxygen saturation (StO2) was stabilized, the automatic tourniquet was inflated to 50 mmHg over the patient's baseline systolic blood pressure and maintained for 5 min. After the 5-min ischemic period, the tourniquet rapidly deflated to 0 mmHg. StO2 data were continuously recorded during the VOT procedure.|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Recovery slope | Recovery slope is related to microvascular reactivity, was calculated from the deflation of the tourniquet until the recovery of tissue oxygen saturation to the highest value. | during applying cardiopulmonary bypass, an average 1-2 hours | 
| Major adverse events | death, acute kidney injury, myocardial infarction, acute respiratory distress syndrome, aggravated heart failure, gastrointestinal bleeding | within postoperative 30 days |