Published online Sep 27, 2019. doi: 10.4254/wjh.v11.i9.689
Peer-review started: April 15, 2019
First decision: June 5, 2019
Revised: June 25, 2019
Accepted: September 5, 2019
Article in press: September 5, 2019
Published online: September 27, 2019
Early allograft dysfunction (EAD) after liver transplantation (LT) is an important cause of morbidity and mortality. To ensure adequate graft function, a critical hepatocellular mass is required in addition to an appropriate blood supply. We hypothesized that intraoperative measurement of portal venous and hepatic arterial flow may serve as a predictor in the diagnosis of EAD.
EAD is a condition that can occur after implantation. The development of graft dysfunction is multifactorial. The degree of impairment can range from a very mild and temporary form to a more severe and potentially deadly form unless the patient receives an early retransplantation, which is determined by initial poor function. The regenerative capacity of the hepatic parenchyma conditions most dysfunctions to be transient. Currently, there are a large number of predictive models for graft failure, all of which are heterogeneous because they use different criteria to select the independent variables. In general, the models try to predict the development of liver dysfunction and aid clinicians in the liver graft selection process. To ensure proper function of a liver graft, the hepatocellular critical mass is needed to maintain synthetic function and adequate blood supply through the vascular tree. Hepatic flow is a determining factor in early graft function. Intraoperatively, measurable arterial and venous flow after implantation may be useful in predicting the development of EAD because blood flow values provide an indirect measurement of the oxygen and nutrient levels. A study of the intraoperative factors that may influence the development of EAD should be performed to address additional, related problems in the field.
To study whether hepatic flow is an independent predictor of EAD following LT.
This is an observational cohort study performed in a single institution. Hepatic arterial and portal venous blood flows were measured intraoperatively by transit flow. The measurement of the intraoperative flows was performed with a VeriQ™ flowmeter (Medistin, Norway). VeriQ™ offers both proven transit time flow measurement and Doppler velocity measurements that are specifically designed for intraoperative blood flow and graft patency verification. The Doppler effect uses the transmission of a continuous wave, and MFTT employs the transmission of pulses. By applying the Doppler concept to the blood components, we can measure the vessel blood flow velocity. If the sound is directed in the direction of flow, the received signal will be different depending on whether the blood components are near or far from the transducer. The sensor used by the MFTT contains two transducers and a reflector. The two transducers are located on one side of the vessel and the reflector on the opposite side; this arrangement causes a double ultrasound passage through the vessel. The crystal located in the direction of flow generates a pulse of ultrasound that is captured by the glass oriented in the opposite direction. The difference in transit time depends on the volume of blood flow. Measurement probes of 5-7 mm calibre are used for the hepatic artery and 8-12 mm for the portal vein. Once the vascular anastomoses have been performed, a brief period of approximately 5 min is allowed for the intrahepatic flow to stabilize, and then the arterial and portal flows are measured sequentially at one centimetre distal to the suture on the side of the graft. In cases where the arterial intraoperative flow measured is absent or very poor, revision of the arterial anastomosis is indicated, once the absence of the portal flow compensatory effect (“hepatic arterial buffer effect”) has been proven. EAD was defined using the Olthoff criteria. Univariate and multivariate analyses were used to determine intraoperative predictors of EAD. Survival analysis and prognostic factor analysis were performed using the Kaplan-Meier and Cox regression models.
A total of 195 liver transplants were performed between January 2008 and December 2014 in 188 patients. A total of 54 (27.7%) patients developed EAD. The median follow-up was 39 mo. Portal venous flow, hepatic arterial flow (HAF) and total hepatic arterial flow were associated with EAD in both univariate and multivariate analyses. HAF is an independent prognostic factor for 30-d patient mortality. This is the first study that relies on current EAD criteria and 30-d patient survival data based on hepatic flow measured intraoperatively.
In conclusion, we have shown that intraoperative measurements of hepatic blood flow can predict the development of EAD and that hepatic artery flow has an impact on survival at 30 d.
Future efforts may focus on study strategies directed at identifying those grafts that are more susceptible to developing alterations in blood flow and how we can mend these alterations in hepatic blood flow in the intraoperative setting.