Pharmacokinetics and Pharmacodynamics of Dexmedetomidine Administered as an Adjunct to Bupivacaine for Transversus Abdominis Plane Block in Patients Undergoing Lower Abdominal Cancer Surgery

South Egypt Cancer Institute

Assiut University

Pharmacokinetics and Pharmacodynamics of Dexmedetomidine Administered as an Adjunct to Bupivacaine for Transversus Abdominis Plane Block in Patients Undergoing Lower Abdominal Cancer Surgery

Research Authors
Fatma A El Sherif, Hala Abdel-Ghaffar, Ahmed Othman, Sahar Mohamed, Mervat Omran, Samia Shouman, Nivin Hassan, Ayat Allam, Sahar Hassan
Research Member
Ahmed Hassan Othman Hassan
Fatma Adel Abd Diab
Neveen Abdelazeem Abdelraheem
Sahar Abdel Baky Mohamed Ahmad
Research Department
Department of Anesthesia, Intensive care and Pain management
Research Date
Research Year
2022
Research Journal
J Pain Res.
Research Vol
15
Research Rank
1
Research_Pages
1–12
Research Website
doi: 10.2147/JPR.S335806
Research Abstract

Background

Despite the growing interest in dexmedetomidine as an adjunct to truncal blocks, little is known about the systemic absorption of dexmedetomidine after these blocks and its role in analgesia and in hemodynamics.

Objective

We investigated the pharmacokinetics and pharmacodynamics of dexmedetomidine as an adjunct to transversus abdominis plane (TAP) block in patients undergoing lower abdominal cancer surgery.

Methods

Twenty-four adult patients were randomized to receive a bilateral single-injection TAP block before surgery with 20 mL of bupivacaine 0.5% (TAP group, n = 12) or combined with 1 µg/kg dexmedetomidine (TAP-DEX group, n = 12) and diluted with saline to a volume of 40 mL (20 mL on each side). Plasma concentrations of dexmedetomidine and its pharmacokinetics were investigated using non-compartmental methods, postoperative analgesia, hemodynamics, and adverse events (nausea, vomiting, itching, hypotension, bradycardia, and respiratory depression).

Results

Dexmedetomidine was detected in the plasma of 11 patients in the TAP-DEX group. The mean dexmedetomidine peak plasma concentration (Cmax) was 0.158 ± 0.085 (range, 0.045–0.31) ng/mL. The median time to reach peak plasma concentration of dexmedetomidine (Tmax) was 15 (15–45) min. From 2 to 8 h postoperatively, visual analog pain scale (VAS) scores at rest and during movement were significantly lower in the TAP-DEX group. Analgesia time was (11.3 ± 3.12 vs 9.0 ± 4.69 h; P = 0.213) and postoperative morphine consumption was (7.4 ± 3.24 vs 11.5 ± 4.46 mg; P = 0.033) in TAP-DEX and TAP groups, respectively. Lower mean heart rate and mean blood pressure were recorded in the TAP-DEX group intraoperatively and 2 h postoperatively (P < 0.05). Except for mild nausea and vomiting, no adverse events were recorded in either group.

Conclusion

Systemic absorption of dexmedetomidine administered in a TAP block is common. Direct central effects on the locus coeruleus caused by this systemic absorption may play a role in the analgesia and hemodynamic effects produced by TAP-dexmedetomidine in addition to local mechanisms.