Ultrasonographic evaluation of abdominal organs after cardiac surgery

Background: Disturbances of the hepatosplanchnic region may occur after cardiac operations. Experimental studies have implicated impairment of splanchnic blood supply in major abdominal organ dysfunction after cardiopulmonary bypass (CPB). We investigated the impact of the cardiac operation and CPB on liver, kidney, and renal perfusion and function by means of ultrasonography and biochemical indices in a selected group of cardiac surgery patients.

Materials and methods: Seventy five patients scheduled for a major cardiac operation were prospectively included in the study. Criteria for selection were moderate or good left ventricular ejection fraction and absence of previous hepatic or renal impairment. Ultrasound examination of the hepatic and renal vasculature and examination of biochemical parameters were performed on the day preceding the operation (T0), on the first postoperative day (T1), and on the seventh postoperative day (T2).

Results: Portal vein velocity and flow volume increased significantly, whereas hepatic artery velocity and flow volume decreased at T1 in comparison with T0. Hepatic vein indices remained unaffected throughout the observation period. Renal artery velocity and flow decreased, whereas renal pulsatility index and renal resistive index increased at T1 as compared with T0. Aspartate aminotransferase and alanine aminotransferase values were increased as compared with baseline values 24 h postoperatively. All parameters displayed a trend to approach preoperative levels at T2. Strong negative correlations between alanine aminotransferase values at T1 and hepatic artery velocity and flow volume at the same time point were also demonstrated (R = 0.638, P < 0.001 and r = 0.662, P < 0.001, respectively).

Conclusions: The increase in portal vein flow and velocity and the decrease in hepatic artery flow and velocity in the period after CPB might be attributed to the hypothermic bypass technique and the hepatic arterial buffer response, respectively. The decrease in renal blood flow and velocity and the parallel increase in Doppler renal pulsatility index and renal resistive index could be considered as markers of kidney hypoperfusion and intrarenal vasoconstriction. Maintaining a high index of suspicion for the early diagnosis of noncardiac complications in the period after CPB and institution of supportive care in case of compromised splanchnic perfusion are warranted.