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Vascular complications are not uncommon after orthotopic liver transplantation (OLTx).1,2 In order to further improve the outcome of OLTx, intra- and postoperative adjunctive measures will be required to further improve such problems as hepatic artery thrombosis. Since the first successful measurement in 1945 by Bradley and others3 with a dye clearance method using bromosulphthalein, various methods have been advocated for the accurate measurement of blood flow to the human liver.4 Of these, the electromagnetic flowmeter technique has emerged to be one of the most reliable, and allows the direct measurement of flow through the hepatic artery (HA) and the portal vein (PV) independently.4 The purpose of this study was to clarify the importance of blood flow measurements during or after OLTx.
Between July 1, 1987 and February 18, 1988, 230 patients underwent 272 OLTx at the Presbyterian Unversity Hospital and Children’s Hospital of Pittsburgh. Their ages varied from 6 months to 72 years old with a mean of 35.9 years; 125 were male (54.3%). During this eight month period, hepatic blood flows were measured in 51 liver allografts of 42 patients after OLTx (18.8%). Of these, 35 grafts in 28 pediatric patients underwent elective flow measurements, and 11 grafts in ten adult and one pediatric patient underwent emergency blood flow measurements. None of the patients were hemodynamically unstable at the time of flow measurement.
Blood flows in the HA and PV were measured with a square-wave electromagnetic flowmeter, Cliniflow II®, Model FM701D (Carolina Medical Electronics, Inc., King, North Carolina). Probes which fit the vessels snugly were selected for the measurement. A zero flow reference was obtained by placing the probes in an isolated ground in a plastic beaker filled with normal saline. At the time of flow measurement, the heart rate, blood pressure, central venous pressure, urine output, the dose of vasopressors and, when available, pulmonary artery pressure and cardiac output were recorded.
Of the 35 grafts in the 28 pediatric patients who underwent elective flow measurements, six (21.4%) had HA flows of less than 60 mL/min. Table 1 lists the flow data of these six patients. Of these six, five patients (83.3%) developed HA thrombosis; four with complete and one with partial thrombosis. Three of these grafts in three patients (10.7%) demonstrated abnormally low HA flows in the presence of good pulsation of the HA (Cases 2, 3, 4). Cases 2 and 3 received no additional definitive procedures, with an assumption that there was flowmeter malfunction. In both cases, HA thrombosis was confirmed immediately postoperatively. In Case 4, HA thrombosis was confirmed intraoperatively by taking down the HA anastomosis. Replacement of the donor celiac axis and common hepatic artery with an interposition arterial graft (donor iliac artery) improved the flow to 50 mL/min. However, this patient also went on to develop HA thrombosis postoperatively.
As shown in Table 2, 11 patients underwent emergency flow measurements. Indications were intraoperative or postoperative HA thrombosis in five (45.5%) and clinical impression of poor HA flow in six patients (54.5%). Among the five patients who underwent flow measurements for intraoperative or postoperative HA thromboses, Case 10 underwent a composite HA reconstruction, in which an aortohepatic interposition graft was anastomosed to the donor proper hepatic artery, and the recipient aberrant right hepatic artery was anastomosed to the donor aberrant right hepatic artery. Of the six patients who underwent flow measurements for poor inflow, three of these patients (50%) underwent a definitive procedure to increase inflow; 1) aortohepatic interpositon graft (Case 1), 2) splenic artery ligation (Case 2) and 3) conversion of the inflow vessel to the recipient aberrant right hepatic artery (Case 3). The other three patients (50%) demonstrated adequate HA flow by flowmeter. Of these 11 patients, HA in nine patients (75%) remained patent, whereas three patients (25%) in whom HA had flows of 120, 300 and 45 mL/min, developed HA thrombosis. In case 6, HA thrombosis was found at the time of retransplantation for primary graft nonfunction at seven days after the inital OLTx.
Of the various vascular complications during or following OLTx, HA thrombosis represents one of the most significant and devastating complications, which has been attributed in large part to technical difficulties, which include anatomical variation, the deep location of the vessels as well as the caliber of the anastomosis.5,6 The present study clearly demonstrates that routine measurement of blood flow in pediatric OLTx can be extremely helpful, since the flow determinations can alert the surgeon to an unrecognized HA thrombosis or to an abnormally low HA flow. This occurred in six out of 28 children (21.4%) in this study.
The results from this study further emphasize that palpation of the HA after HA anastomosis is not necessarily a reliable method to examine HA patency or flow, and that strong pulsatile flow from the amputated distal donor splenic artery merely suggests good inflow to that point, and does not necessarily verify the presence of distal arterial patency. The other contribution of blood flow measurements after OLTx is the acquisition of objective data on hepatic arterial flow following reconstruction of the HA for HA thrombosis. Although our experience in the measurement of blood flow after such arterial revision has been limited, low HA flow after the revision may be associated with recurrent HA thrombosis.
Supported by Research Grants from the Veterans Administration and Project Grant No. AM 29961 from the National Institute of Health, Bethesda, Maryland.