Influence of Dexmedetomidine and Lidocaine on Opioid Consumption, Cognitive Function and Incidence of Neuropathic Pain in Laparoscopic Intestine Resection

Introduction: The consumption of opioid analgetics and their side effects can be minimized by using the combination of opioid analgesics and analgesics with different mechanism of action. The investigators will use opioid analgesic fentanyl alone or in combination with dexmedetomidine or lidocaine. Dexmedetomidine is alpha 2 adrenergic receptor agonist and is used more and more during anesthesia because of its anesthetic and analgesic effects as it preserves mental status and decreases the consumption of analgesics. Lidocaine is a local anesthetic and antiarrhythmic drug which decreases opioid consumption as well.

The participants scheduled for laparoscopic intestine resection will be divided in three groups: in the first group, the participants will receive single boluses of fentanyl, in the second group, the participants will receive continuous infusion of lidocaine and single boluses of fentanyl, and in the third group, the participants will receive continuous infusion of dexmedetomidine and single boluses of fentanyl.

Hypothesis: Participants with intraoperative infusion od dexmedetomidine or lidocaine will need less boluses of fentanyl during the operation and less opioid analgesics after the operation in comparison to those who will receive only fentanyl boluses. Better cognitive function after the operation in participants receiving dexmedetomidine infusion is expected. There will be minimal incidence of neuropathic pain because of minimal surgical injury of peripheral nerves in all groups.

Justification: Lidocaine and dexmedetomidine are analgesics with different mechanism of action in comparison to opioid analgesics. Their use during the operation decreases the consumption of opioids intra- and postoperatively. Dexmedetomidine has beneficial effect on cognitive function and that is why the investigators expect preserved cognitive function in participants after the operation. Because of minimal surgical injury and, therefore, minimal probability of peripheral nerve injury, the investigators expect low incidence of neuropathic pain in all groups.

Methods: The investigators will include 60 participants in the study, between 35 to 85 years old, ASA 2 - 3 (American Society of Anesthesiologists, ASA) undergoing a planned laparoscopic intestine resection. The participants will be randomized into three groups. In the first group, fentanyl boluses will be adimistred during the operation, in the second, infusion of lidocaine will be added to fentanyl, and in the third, the infusion of dexmedetomidine will be added to fentanyl. The investigators will record opioid consumption during the operation and two days after the operation. The investigators will use mini mental test for evaluation of cognitive function before the operation and at the transfer of the participant postoperatively to the surgical ward, in order to explore the influence of analgesics used on cognitive function. Two months after the operation the degree of neuropathic pain will be evaluated with pain questionnaire. The data will be statistically evaluated.