Early introduction of tolvaptan after cardiac surgery: a renal sparing strategy in the light of the renal resistive index measured by ultrasound

Background: Renal failure is a serious complication after cardiac surgery, which can be caused by long-term intravenous (IV) loop diuretic use. Tolvaptan is an oral selective vasopressin-2 receptor antagonist used in patients irresponsive to loop diuretics. We investigated their renal perfusion changes using the resistive index (RI) postoperatively. Methods: Serial renal RI, echocardiography, and laboratory examinations from 14 patients requiring continuous postoperative IV loop diuretics were reviewed. Eight patients received tolvaptan (Group T) and six received oral loop diuretics before the discontinuation of IV loop diuretics (Group L). The 1st data were obtained between postoperative day 0 and 2, the 2nd when patients were still under IV loop diuretic treatment, the 3rd after the initiation of tolvaptan or oral loop diuretic, and the 4th after the discontinuation of IV diuretics. Results: The 2nd RI value was higher in Group T than Group L (0.77 +/- 0.09 vs. 0.69 +/- 0.01, p = 0.049) but significantly decreased after tolvaptan administration [0.77 +/- 0.09 to 0.65 +/- 0.05 (2nd to 3rd), to 0.62 +/- 0.04 (to 4th), both p = 0.006], while no such changes were seen in Group L. The serum sodium and albumin levels, and echo-derived tricuspid annular plane systolic excursion increased only in Group T (134.1 +/- 1.5 to 138.8 +/- 3.2 mEq/L, 3.3 +/- 0.3 to 3.7 +/- 0.5 g/dL, 16.4 +/- 3.6 to 19.7 +/- 4.2 mm, all p < 0.05). The duration of IV loop diuretics tended to be shorter in Group T than Group L (5.6 +/- 1.6 vs. 8.7 +/- 3.6 days, p = 0.051). Conclusions: Administration of tolvaptan in patients undergoing cardiac surgery may improve their renal perfusion, as reflected by the renal RI measured using renal Doppler ultrasound.