Evaluation of a Model for Post-Anesthesia Troponin Increase and Heart Injury EStimation

Perioperative cardiac troponin leak is common and is strongly associated with mortality even in absence of classic myocardial infarction signs. In the VISION study 11.6% of patients undergoing non-cardiac surgery were troponin positive and 1.9% (95%CI 1.7-2.1%) of those patients died within 30 days of surgery. In selected populations of patients undergoing vascular surgery, a postoperative cTn leak, without clinical features of myocardial ischemia, is associated with an increased risk of 30-day mortality (odds ratio 5.03, 95% CI 2.88-8.79). Myocardial oxygen supply-demand imbalance and plaque rupture/thrombosis are the main mechanism involved in the pathogenesis of postoperative myocardial ischemic events. Frequently cardiac troponin leaks occur in absence of classical signs and symptoms of myocardial infarction. More than 80% of patients with postoperative cardiac troponin leak are clinically asymptomatic for myocardial ischemia, and ischemic ECG changes are often absent.

The identification of patients who will experience a postoperative myocardial ischemia will continue to be a challenge for anaesthesiologists.The current tool used for risk stratification using the AHA/ACC algorithm is Lee's Revised Cardiac Risk Index. Unfortunately, this tool can only reliably exclude low-risk patients and cannot identify patients which are likely to have perioperative cardiovascular complications.

The surgical plethysmographic index (SPI, GE Healthcare, Finland) during general anaesthesia has been correlated with the stressors of surgery (e.g. intubation, incision, …), and with stress hormone production. It has been demonstrated that SPI and other pulse photo-plethysmographic indices reflect sympathetic-mediated vasoconstriction, thus monitoring the SPI during general anesthesia could lead to a reduced sympathetic response to surgical stimuli. Unfortunately there is not a desirable level of SPI, and it is unknown if difference in SPI values during the surgery might affect the postoperative outcome.

Intraoperative hemodynamic parameters and SPI will be recorded in conjunction with preoperative cardiovascular risk scores and will be used to develop a multiple variable model for postoperative risk of myocardial ischemic events.

In this study Electrocardiogram, invasive arterial pressure, photoplethysmography,and electroencephalographic entropy will be collected continuously from 10 min before induction of general anesthesia until 20 min after awakening from anesthesia. Gupta's score and Revised Cardiac Risk Index will be recorded the day before surgery.

Blood samples for high sensitive cardiac troponin T (hs-TnT) assay will be collected on day of surgery (baseline) and on postoperative day 1, 2 and 3. According to this methodology, in this study postoperative myocardial ischemic events will be defined as:

• Myocardial Infarction according to the third universal definition (Thygesen K. et al. Third universal definition of myocardial infarction. Circulation 2012;126:2020-35 )
• Myocardial Injury defined a hs-TnT plasmatic concentration of (i) 20-65 ng/L with an increase >5ng/L between baseline to days 1-3, or (ii) >65 ng/L, or (iii) a rise >50% between baseline and days 1-3 in case of renal insufficiency, all of them in absence of non-ischemic causes of troponin increase (sepsis, pulmonary embolism, electrical cardioversion and acute respiratory failure).

Inclusion criteria

• patients scheduled for elective non-cardiac vascular surgery under general anesthesia

Exclusion criteria

• Raynaud's phemomenon
• permanent atrial fibrillation or non sinus rhythm on ECG or ectopic beats >5% of normal sinus beats
• implanted with pacemaker
• any circulation problem in forefingers
• scheduled for postoperative ICU admission
• a new therapy with beta-blockers started <7 days before the surgery