Sodium nitroprusside after cardiac surgery: systemic and splanchnic blood flow and oxygen transport.
BACKGROUND
Vasoactive drugs may interfere with splanchnic blood flow and tissue oxygenation. Sodium nitroprusside (SNP) is widely used in the treatment of postoperative hypertension after cardiac surgery, but the effects of SNP and other vasodilators on splanchnic blood flow have not been well documented.


METHODS
The effects of SNP on systemic blood flow, oxygen transport and gastric intramucosal pH (pHi) were studied in 12 patients with arterial hypertension after coronary artery bypass grafting. In 9 of these patients, the effect on regional (splanchnic and leg) blood flow and oxygen transport was also measured. Hemodynamic and regional blood flow responses were measured before and during SNP infusion (mean 2.8 +/- 1.7 micrograms/kg/min, range 0.6-6.3 micrograms/kg/min), when the goal of the vasodilator treatment, mean arterial pressure 70-80 mmHg, had been reached.


RESULTS
SNP increased splanchnic (0.65 +/- 0.22 vs. 0.87 +/- 0.37 L.min-1.m-2, P < 0.01) and femoral blood flow (0.15 +/- 0.04 vs. 0.21 +/- 0.06 L.min-1.m-2, P < 0.05) in parallel with cardiac index (2.6 +/- 0.6 vs. 3.3 +/- 0.7 L.min-1.m-2, P < 0.01). Fractional regional blood flows did not change. Mean gastric intramucosal pH decreased slightly (7.40 +/- 0.07 vs. 7.37 +/- 0.06, P < 0.05). Both systemic (420 +/- 85 vs. 495 +/- 90 mL.min-1.m-2, P < 0.05) and femoral oxygen delivery (25 +/- 5 vs. 32 +/- 10 mL.min-1.m-2, P < 0.05) increased, but neither systemic nor regional oxygen consumption changed.


CONCLUSIONS
These results suggest that vasoregulation is well preserved during treatment of early postoperative hypertension with SNP, and that SNP has no adverse effects on splanchnic tissue oxygenation.
Parviainen
I
I
Department of Intensive Care, Kuopio University Hospital, Finland.
Ruokonen
E
E
Takala
J
J
D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001026:Coronary Artery Bypass; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000188:drug therapy / Q000209:etiology; D008875:Middle Aged; D009599:Nitroprusside / Q000627:therapeutic use*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000187:drug effects; D011183:Postoperative Complications; D013152:Splanchnic Circulation / Q000187:drug effects*
D000959:Antihypertensive Agents; D009599:Nitroprusside; D010100:Oxygen