Influence of Nociception Level Monitor (NOL) Guided Analgesic Delivery on Robot-assisted Colorectal Surgery

During anesthesia for surgical procedures, anesthetic and muscle relaxant drugs can be meticulously administered using Bispectral Index (BIS) and neuromuscular monitors. However, analgesic drugs are still dispensed using poor surrogate parameters such as heart rate and blood pressure. This subjective dosing of analgesic drugs may invariably lead to inappropriate intra-operative consumption. This may result in tachycardia, hypertension, and postoperative pain due to e.g. insufficient analgesia, or hypotension, bradycardia, respiratory depression and Post-Operative Nausea and Vomiting (PONV) secondary to excessive analgesia. These effects may be detrimental to the patients especially those with multiple comorbidities with limited vital organ reserves such as patients classified to III or IV by the American Society of Anaesthesia classification (ASA) Similarly, immediate postoperative recovery may also get delayed due to pain, unstable hemodynamics, nausea and vomiting. In that context, there has long been search for a monitor which can guide meticulous administration of analgesics. Recently, a Nociception Level monitor (NOL) based on advanced software algorithms using multiple physiological parameters has been developed. It offers an objective score (NOL Index) which relates to the level of intra-operative pain. NOL technology has been validated and found superior to existing pain indicators in peer-reviewed publications. The NOL monitor may offer interesting observations in perioperative nociception levels and appropriate analgesic consumption in diverse surgeries, including robot-assisted surgery. These observations may supplement the current efforts towards further advantages in rapid restitution. Therefore, the investigators are planning a trial where intra-operative analgesics are guided using an NOL monitor.

Inclusion criteria

• American Society of Anaesthesiologists score III-IV
• Scheduled for elective major robot-assisted colorectal surgeries

Exclusion criteria

• Inability to give informed consent
• planned spinal or epidural anaesthesia
• all forms of regional anaesthesia, including wound infiltration
• nonelective procedures
• pregnancy or lactation
• atrial fibrillation