Background and Goal of Study: Comparison of the plasma pharmacokinetics of bupivacaine in combination with clonidine versus dexmedetomidine in a spinal anesthesia.

Materials and Methods: randomized, double-blind prospective study including 40 patients ASA I or II, admitted for surgery for fracture of the femoral neck under spinal anesthesia. divided into 2 groups: GC (injection of 10 mg of bupivacaine hyperbare0,5% + 15 µg clonidine) and GD (10 mg hyperbaric bupivacaine + 3μg dexmedetomidine) neither the patient nor the pharmacologist know the nature of the adjuvant.another anesthesiologist who assured only transport of samples, evaluates the time and duration of sensory block (prick-touch test at T12) and motor (modified Bromage score> 2) Venous blood samples of 3 ml were obtained before bupivacaine injection and immediately after spinal injection and at 5, 10, 30, 45, 60, 120 and 240 min after the final injection. The plasma separated by centrifugation of blood samples and stored at −20°C until use. Bupivacaine quantification in samples was carried out using HPLC method with ultraviolet absorbance detection (λ =207 nm). Statistic study with SPSS22.

Results and Discussion:

 
	GC	GD	p
delay sensitif block (min)	7,8±2,6	5,7±1,9	0,044
delay motor block (min)	10,8±3,4	10,2±3,1	0,21
duration of act (min)	54,6±16,2	50,8±19,1	0,54
duration of motor bloc(min)	92,2±31,6	101,1±29,4	0,07
duration of sensitif bloc (min)	151,4±39,2	176,6±44,6	0,031
Systemic clairance Cl (ml/min)	930±282	818±131	0,024
Volume of distribution VD (l)	102±24,8	118±41,8	0,067
Plasmatic half-life T½ (min)	88,7±34,9	104,6±49,6	0,029
Maximal plasma bupivacaïne concentration Cmax (µg/ml)	0,668±0,234	0,412±0,186	0,034
Time to reach the peak plasma concentration Tmax (min)	38,66±16,44	51,29±18,87	0,041
 



Conclusion :Dexmedetomidine decreases the systemic absorption of bupivacaine compared to clonidine during spinal anesthesia, which could explain the extension of sensory block.


06 / Pharmacokinetics of bupivacaïne in combination with clonidine versus dexmedetomidine in spinal anesthesia.