This study will investigate the potential of guiding remifentanil analgesia during cardiac and vascular surgery in moderate to high risk patients requiring general anesthesia.

Justification:

Moderate-to-high risk cardiovascular surgery is associated with perioperative morbidity and mortality. These patients undergo general anesthesia and often require tight blood pressure control (e.g., using norepinephrine titration) to avoid the complications associated with hypotension and reduced cardiac output. Standard analgesia opioid titration to control nociception (i.e., the patient's unconscious response to noxious stimuli) is based on the anesthesiologist's experience and variations in the patient's heart rate and blood pressure. This causes anesthesiologists to often give too much analgesic, which can lead to inhibition of the sympathetic autonomic nervous system, hypotension, and associated side effects. A recently developed nociception monitor, the PMD-200 (Medasense, Israel), is capable of measuring the patient's level of nociception-antinociception balance and can guide opioid administration. This monitor may allow anesthesiologists to administer only the required amount of opioid, which may lead to better hemodynamic stability and better postoperative outcome.

Objectives:

The goal of this study is to determine if titrating analgesia using the Nol-Index, when compared to standard care, leads to decreased infused remifentanil, decreased norepinephrine, increased cardiac output, more stable blood pressure control, and decreased postoperative complications in moderate-to-high risk patients undergoing cardiac or vascular surgery.

Inclusion Criteria:

• moderate-to-high risk cardiac or vascular surgery
• ASA 2-4

Exclusion Criteria:

• chronic arrhythmia (e.g. atrial fibrillation)
• aortic insufficiency
• pacemaker
• implanted defibrillator
• valve surgery