Low-dose dopamine after kidney transplantation: assessment by Doppler ultrasound

Low-dose dopamine (LDD) is commonly used after kidney transplantation as a renoprotective agent, although the benefits of dopamine (DA) in this settin g are controversial. LDD increases renal blood flow, decreases resistive in dex (RI) and causes diuresis in normal kidneys. We hypothesised that the va sculature of a denervated renal transplant may not respond to DA in the sam e way as healthy native kidneys. In a prospective, controlled study, renal blood flow velocity and vascular resistance were measured by Doppler ultras ound in recent kidney transplants (n = 20) over a range of DA doses (0-5 mu g/kg/min). Main renal artery velocity was lower in kidneys with acute rena l dysfunction than in those with normal function (0.60 +/- 0.31 vs. 0.81 +/ - 0.24. respectively, p < 0.05). There was no demonstrable haemodynamic eff ect of LDD on either RI or main renal artery velocity as measured by Dopple r ultrasound. Interestingly, the only significant correlation with mean RI was trough cyclosporin A level (r = 0.57, p < 0.001). Technical or timing f actors cannot be used to explain the absence of DA effect, with equivalent doses capable of producing vasodilatation and reduced RI in studies of norm al kidneys. In summary, these findings contrast the DA response of healthy native kidneys and may explain studies showing no clinical benefit of LDD i n the early post-transplant period. These data suggest an insensitivity of recently implanted kidneys to the vasodilatory effects of LDD, that other f actors such as cyclosporin A vasoconstriction may also be important, and qu estion the rationale for routine LDD after kidney transplantation.