Hyperalgesia, Persistent Pain, and Fentanyl Dosing in On-Pump Coronary Artery Bypass Grafting

A prospective, randomized, double-blinded (patient, anesthesiologist, assessor) clinical study. This study will examine three different clinically used application schemes of fentanyl, an opioid used as the standard of care in routine practice. Patients will be randomized to receive one of the following three treatment arms for anesthesia maintenance (pre-sternotomy):

1. High-dose fentanyl bolus (20 µg/kg of body weight [BW]; e.g. 70kg 1400 µg or 1.4mg)
2. Low-dose fentanyl bolus (3 µg/kg BW; e.g. 70kg 210 µg or 0.2mg)
3. Continuous fentanyl application by Shibutani scheme

This study will include data from 69 adult patients (23 per arm) undergoing first time, elective, on-pump CABG surgery with median sternotomy and central cannulation.

Following randomization by the sealed envelope technique, fentanyl kits will be drawn up by an anesthesiologist not involved in patient care or outcome assessment. Patients with preexisting chronic pain, opioids in the last 30 days, a BMI>36kg/m2, sleep apnoea, renal failure (clearance <30ml/min), with neuraxial anesthesia, pregnant, with planned wound infiltration, known allergies/intolerance to opioids, and unable to understand pin-prick testing will be excluded.

At induction, all patients will receive a standard 3 µg/kg bolus of fentanyl (not study medication, but rather standard of care). 5 minutes prior to sternotomy, the patient will receive analgesia maintenance (one of the three fentanyl study arms). Clinicians will at all times be able to administer a bolus of fentanyl on a perceived "as needed" basis (not study medication, but rather standard of care).