The role of perioperative IV administration of nimodipine, an L-type calcium channel antagonist which is capable of crossing the blood-brain barrier, on peri-operative opioid and anesthetics requirements, pain intensity, opioid-related side effects and early postoperative bowel mobility in patients undergoing surgical treatment for bowel cancer with open radical colectomy remains scarcely explored. A prospective double-blind, randomized controlled trial investigating the effect of perioperative IV administration of nimodipine in patients undergoing open colectomy for cancer treatment is therefore conducted.

Background with aim: Acute postoperative pain is still of major clinical concern for a large number of patients undergoing surgery worldwide. Despite advances in pain management strategies, many patients continue to suffer from moderate-to-severe pain during the early postoperative period, while opioids are still largely over-prescribed. Not effectively and especially unrelieved pain can result in decreased patient satisfaction, increased morbidity, prolonged hospital length-of-stay and increased risk of persistent pain. Furthermore, effective treatment of acute postoperative pain using opioid analgesics remains the core treatment for postoperative pain. Although the potential benefits of opioid therapy for acute pain lead to a short-term pain control there are several potential severe side-effects associated with opioid use which may outweigh the benefits including sedation, nausea, vomiting, constipation especially in bowel surgery, and the risk of long-term use. Although various non-opioid drugs have been investigated over the past decades, information regarding L-type calcium channel blockers in acute postoperative pain is limited. In this respect, the perioperative use of nimodipine, a drug which furthermore crosses the blood-brain barrier and has direct effects on the Central Nernous System (CNS) could potentiate the effects of opioid analgesia and intraoperative anesthetic requirements, providing improved analgesia and potentially reduce for opioids in the perioperative period. Therefore, the investigators decided to carry out the present study with the aim to examine the analgesic efficacy and safety of perioperatively administered IV nimodipine in patients undergoing open colectomy on perioperative opioid and anesthetic consumption, pain intensity, opioid-related side effects and early postoperative bowel mobility.

Method: A power analysis based on a previous preliminary study using IV nimodipine for medium risk general surgery (open cholecystectomy) showed that 9 patients would provide a power greater than 0.9 (α = 0.05) for detection of differences of pain scores and cumulative opioid consumption over time (up to 48 h). Therefore, 40 patients undergoing open colectomy will be included in this prospective, randomized, double-blind, controlled trial with two arms: an intervention arm (IV nimodipine 4 mg/h starting 1h prior to surgery until one h after the start of surgery, followed by 2 mg/h until 24 h post-operation) and a control arm (isotonic saline 20 ml/ h 1h prior to and until one h after start of surgery, followed by 10 ml/h until 24 h post-operation). The study is approved by the local hospital scientific board (#18-4_2024-12-05).

Hypothesis: The investigators hypothesize that perioperative intravenous administration of nimodipine, an L-type calcium channel antagonist, will be effective in reducing intraoperative anesthetic requirements, as well as intra- and postoperative opioid requirements, as well as postoperative pain intensity and opioid-related side effects.

Inclusion Criteria:

• Patients scheduled for open surgical treatment of bowel cancer at the General Hospital of Patra

Exclusion Criteria:

• Age < 18 years, > 75 years
• American Society of Anesthesiologists (ASA) physical status > III
• Allergy to nimodipine
• Inability to provide informed consent
• Known severe renal insufficiency
• Known severe bradyarrhythmia
• Daily opioid consumption the last 7 days before surgery
• Pain intensity assessed using the Numerical Rating Scale (NRS; 0-10), with scores greater than 5 reported on more than half of the days during the past month.

The data will be shared upon reasonable request by other researchers

Randomization and study medication will be handled by the hospital pharmacy. All research team members, caregiving clinicians and enrolled patients will be blinded to the study allocation arms and the randomization list will be concealed until all statistical analyses are made.