Dorsal hand vein responses to the α1-adrenoceptor agonist phenylephrine do not predict responses to the α2-adrenoceptor agonist dexmedetomidine

Significant inter-individual variability exists in responses of human dorsal hand veins to activation of α-adrenoceptors. Simultaneous graded infusions of the α1- and α2-adrenoceptor agonists phenylephrine (3.66-8000 ng/min) and dexmedetomidine (0.0128-1000 ng/min) were given into dorsal veins of both hands and responses of 75 subjects were analyzed to assess whether a subject's sensitivity to phenylephrine (ED50) predicts his sensitivity to dexmedetomidine. Individual ED50 estimates of dexmedetomidine and phenylephrine ranged between 0.06-412 and 14.2-7450 ng/min and exhibited only a weak positive relationship (r2 = 0.074, P = 0.018). Finger temperature, body mass index, age and phenylephrine sensitivity together accounted for about 30% of dexmedetomidine ED50 variation (r2 = 0.315, P < 0.001). The large inter-individual variability observed in the responses of dorsal hand veins to both α1- and α2-adrenoceptor agonists is not explained by some common factors; instead, dorsal hand vein responsivity is separately determined for both receptor mechanisms.