Effect of dexmedetomidine on neuromuscular blockade in patients undergoing complex major abdmoinal or pelvic surgery

الملخص EN

Background and objectives : Dexmedetomidine is a highly selective a2 agonist with anesthetic, analgesic and sympatholytic properties.

Its neuromuscular effects in humans are unknown.

This study evaluates the effect of dexmedetomidine on neuromuscular block and hemodynamics during thiopental / isoflurane anesthesia for patients with complex abdominal or pelvic surgery.

Patients and methods : during thiopental/ isoflurane anesthesia, the rocuronium infusion rate was adjusted in 20 complex surgery patients to maintain a stable first response (T1) in the train of four sequence of 50 % ± 3 of the pre-rocuronium value.

Dexmedetomidine was then administered by infusion pump, targeting a plasma dexme-detomidine concentration of 0.6 ng / dL for 45 min.

The evoked mechanical responses of the adductor policies responses (T1 response and T4/T1 ratio), systolic blood pressure, diastolic blood pressure and heart rate (HR) were measured during the dexmedetomidine infusion using repeated measures analysis of variance.

Plasma levels ranged from 0.73 to 1.38 ng / mL.

Results: T1 values decreased during the infusion from 55 ± 2 to 38 ± 9 (p < 0.05).

T4 / T1 values did not change during the infusion.

Dexmedetomidine increased SBP (p < 0.001) and decreased HR (p < 0.05) (10 min median values) during the infusion compared with values before the infusion.

This study demonstrated that dexmedetomi-dine decreased T1, increased SBP and decreased HR during thiopental / isoflurane anesthesia.

Conclusion : we conclude that dexmedetomidine induced direct vasoconstriction may alter pharmacokinetics of rocuronium, therefore increasing plasma rocuronium concentration.

Although these effects were statistically significant, further studies should be held for understanding and characterizing the peripheral vasoconstrictive effects of a2 agonists that allow better management and determination of drug dosing regimens.