Microvascular Reactivity in Cardiac Surgery

Overview

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.

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

Study Type

  • Study Type: Observational
  • Study Design
    • Time Perspective: Prospective
  • Study Primary Completion Date: May 30, 2019

Detailed Description

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 (INVOSĀ® 5100C Cerebral/Somatic Oximeter; Medtronic, Minneapolis, MN, USA) was placed on the thenar eminence and an automated tourniquet (A.T.SĀ® 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.

Interventions

  • 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.

Clinical Trial Outcome Measures

Primary Measures

  • Recovery slope
    • Time Frame: during applying cardiopulmonary bypass, an average 1-2 hours
    • 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.
  • Major adverse events
    • Time Frame: within postoperative 30 days
    • death, acute kidney injury, myocardial infarction, acute respiratory distress syndrome, aggravated heart failure, gastrointestinal bleeding

Participating in This Clinical Trial

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

Gender Eligibility: All

Minimum Age: 19 Years

Maximum Age: N/A

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • Pusan National University Hospital
  • Provider of Information About this Clinical Study
    • Principal Investigator: Hyeon-Jeong Lee, Professor – Pusan National University Hospital
  • Overall Official(s)
    • Heon-Jeong Lee, PhD, Principal Investigator, Pusan National University Hospital

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