A. Gurlek et al., DRUG-INDUCED VASODILATION - THE EFFECTS OF SODIUM-NITROPRUSSIDE, HYDRALAZINE, AND CROMAKALIN ON THE RABBIT CAROTID-ARTERY - IN-VITRO AND IN-VIVO STUDY, Journal of reconstructive microsurgery, 13(6), 1997, pp. 415-421
Extreme arterial and venous constrictions are common problems in micro
vascular surgery, often leading to tissue injury and flap failure. The
ideal pharmacologic tool to counteract. ischemia should exert its act
ion both locally and distally in the microcirculation of the flap, In
this study, the vascular properties of sodium nitroprusside, hydralazi
ne, and cromakalin were evaluated and compared in in vitro and in viva
models in the rabbit carotid artery. In the in vitro study, 20 rings
from the rabbit carotid artery were bathed in Krebs-Ringers solution,
stretched progressively to an optimal tension of 3.7 to 4.2 gm, and th
eir isometric contractile activity was measured. The specimens were pr
econtracted with norepinephrine (1 mu M) and a dose-response curve was
established by adding cumulatively either sodium nitroprusside (n = 7
), cromokalin (n = 7), or hydralazine (n = 7) at increasing concentrat
ions. In the in vivo study, microvascular anastomoses were performed b
ilaterally in the rabbit carotid artery in 19 animals using 9-0 nylon
suture and standard microsurgical techniques. In each animal, one side
was treated with heparinized sodium chloride, and served as control.
The other side was treated blindly with the topical application of 1 m
l of either sodium nitroprusside (10 mg/ml, n = 5), hydralazine (20 mg
/ml, n = 5), or cromakalin (25 mg/ml, n = 4), during and after the ana
stomoses. Blood-flow changes in the vessels were continuously monitore
d with the transonic Doppler applied to both carotid arteries for 60 m
in after the procedure. Sodium nitroprusside and cromakalin elicited a
concentration-dependent relaxation of norepinephrine-precontracted ca
rotid artery rings in vitro. Sodium nitroprusside was significantly mo
re effective than cromakalin in inducing relaxation. Hydralazine elici
ted a biphasic response, with low concentrations (1.5 x 10(-5) to 1.5
x 10(-3) M) potentiating the norepinephrine-induced contraction, and h
igh concentrations relieving this contraction. Microsurgical anastomos
is in the rabbit carotid artery-produced a significant decrease of blo
od flow through the vessel as measured by the transonic Doppler for 30
min. Topical application of heparinized saline did not significantly
change the blood flow after the microvascular anastomosis. Topical app
lication of sodium nitroprusside and cromakalin significantly increase
d the blood flow in the vessel after the anastomosis; however, the top
ical hydralazine did not significantly alter blood flow, but demonstra
ted a trend toward increased flow values. The data support the conclus
ion that sodium nitroprusside and cromakalin could be used to relieve
vascular constriction. It is suggested that further studies on the cli
nical use of these drugs in microsurgery is warranted.