Comparative Study Between Intraperitoneal Administration of Either Bupivacaine and Tramadol Versus Bupivacaine and Dexmedetomedine for Analgesia After Abdominal Laparoscopic Cancer Surgeries. A Prospective Randomized Pilot Study

Recently laparoscopic procedures have become popular and familiar to both surgeons and anesthetists. They have many advantages such as rapid postoperative recovery, low postoperative complication rates, early mobilization, and early home discharge; consequently reduce hospital stay and costs. Although previous studies have been shown that laparoscopy is associated with less pain than laparotomy, it is not totally pain free. Some laparoscopic procedures for abdominal cancer surgeries has shown that there may be more intense pain and greater analgesic requirements in the immediate postoperative period than after open laparotomy.

Thoroughly understanding the difference of pain generators in laparotomy than in laparoscopy gave some ideas helping in the control of each of them. While laparotomy results mainly in parietal pain, visceral pain remains predominantly in patients after laparoscopic surgeries resulting from the stretching of intra-abdominal cavity, peritoneal inflammation and phrenic nerve irritation caused by residual carbon dioxide in the peritoneal cavity resulting in postoperative abdominal and shoulder pain after laparoscopy. Hence, Intraperitoneal (IP) administration of some drugs can be effective for pain relief after laparoscopic surgery. The results have been variable as the published studies are heterogeneous and often lack appropriate controls. For that, no definitive conclusion can yet be made regarding its value and effectiveness.

The α2-adrenergic agonist provides excellent sedation, anxiolysis, analgesia and sympatholysis. Of them, dexmedetomidine has become one of the frequently used drugs in anaesthesia aiming to its hemodynamic, sedative, anxiolytic, analgesic, neuroprotective and anaesthetic sparing effect. In addition, the high selectivity of dexmedetomidine to α2- receptors favored its widespread use in regional anaesthesia practice and local nerve blocks techniques.

As noradrenergic neurons descending through the dorso-lateral funiculus from the brainstem to the dorsal horn significantly contribute in the modulation of pain by controlling impulse transmission (descending inhibitory pathway). Adrenergic agonists, such as dexmedetomedine, possess significant antinociceptive activity by a central action on the brainstem and a spinal action on the substantia gelatinosa of the dorsal horn.

Tramadol is a synthetic opioid pain medication used to treat moderate to moderately severe pain. It exerts its analgesic effects through a variety of different targets on the noradrenergic, serotoninergic and opioid receptors systems. It also exists as a racemic mixture, the positive enantiomer inhibits serotonin reuptake while the negative enantiomer inhibits noradrenaline re-uptake, by binding to and blocking the transporters. Finally, tramadol has also been shown to act as a serotonin releasing agent. Both enantiomers of tramadol are agonists of the μ-opioid receptor and its M1 metabolite, O-demethylate, which is also a μ-opioid receptor agonist but is 6 times more potent than tramadol itself. All these effects work synergistically to induce analgesia.