Hepatic artery reconstruction using an operating microscope in pediatric liver transplantation—Is it worth the effort?

In pediatric liver transplantation (pLT), hepatic artery thrombosis (HAT) is associated with inferior transplant outcome. Hepatic artery reconstruction (HAR) using an operating microscope (OM) is considered to reduce the incidence of HAT.

The primary endpoint was the occurrence of HAT. Secondary endpoints were 1-year patient and graft survival and complications.

| Graft types and operation technique
The allocation process of DDLT grafts was organized by Eurotransplant.
The LDLT donors were selected by a standardized protocol and accepted by the living donation ethics committee. Liver transplantation was carried out with caval replacement (full-size graft, extended right lobe) or in a piggy-back technique (S 2/3 or S 2/3/4). In both the standard and microsurgical cohorts, the order of anastomoses was as follows: vena cava, portal vein, hepatic artery, and finally bile reconstruction. Vena cava, left hepatic vein, and portal vein were anastomosed using PDS 5-0, 6-0, or 7-0 running sutures. In the SL group, HAR was performed with PDS 7-0 or 8-0 interrupted or running sutures. In the OM group, HAR was performed with interrupted 9-0 or 10-0 silk sutures by a plastic surgeon. The OM (OPMI ® Vario 700, Carl Zeiss Meditec AG) was placed on the right side of the patient and the plastic surgeon stood on the left side.

| Perioperative management
We used a standardized clinical protocol for immunosuppression, using the anti-IL-2 receptor antagonist Basiliximab for induction and on tacrolimus and tapered steroids. All patients were treated with i.v. heparin aiming a postoperative activated partial thromboplastin time of 50 s. In patients without signs of hemorrhage, acetylsalicylic acid was routinely administered (3-5 mg/kg/day) from postoperative day 3 and continued for 6 months. Ultrasound screening of graft perfusion was carried out routinely 4 times per day in the first 3 days after pLT and 2 times per day on days 4-7. CT was carried out in all patients with loss or pathological arterial Doppler signal flow in the ultrasound examination to confirm or exclude HAT.

| Data acquisition and definitions
Electronic records of recipient clinical data were collected from the hospital information system (SAP ® SE). Anonymous donor data were Conclusion: In pLT, the use of an OM is significantly associated to reduce HAT rate, biliary complications, and graft loss and outweighs the disadvantages of delayed arterial perfusion and prolonged warm ischemia time (WIT).

K E Y W O R D S
hepatic artery reconstruction, hepatic artery thrombosis, operating microscope, pediatric liver transplantation, surgical loupes acquired from the ENIS. All patients were tracked for recipient age, gender, height, weight, GRWR (in %), etiology of the liver disease, graft-type (LDLT, DDLT), anastomosis technique (SL/OM), WIT, CIT, length of stay, and complications.
Patient and graft survival, MELD, and PELD were defined according to the UNOS criteria. [16][17][18][19] Laboratory MELD was calculated for all recipients, while PELD was calculated for all recipients aged 11 years and younger. The last follow-up was August 1, 2021. The analysis and reporting of data received institutional ethics board approval (EA2/267/20).

| Statistical analysis
Statistical analyses were carried out using IBM SPSS Statistics,   Table 1.

| RE SULTS
In 58 (73.4%) cases, HAR was carried out using SL and in 21 (26.6%) cases using an OM. The two groups showed no significant differences with regard to recipient age (11.9 [7.7-99.5] in OM vs. In the OM group, 9 (    Multiple regression analysis revealed DDLT (p = .014) and HAR with SL (p = .022) as an independent risk factor for HAT occurrence (Table 3). HAT was independently associated with the need for retransplantation (p < .001) and biliary leakage (p = .045) but not with patient mortality (p = .140) and ITBL (p = .759; Table 4).

| DISCUSS ION
Albeit the evolution of surgical techniques and instruments, HAR remains the most demanding part of pLT, with HAT being one of the most dramatic complications. [7][8][9] If not resolved within the first 24 h, HAT almost invariably leads to major morbidity, graft loss, and mortality. 10,20 Even if urgently resolved by surgical or radiological thrombectomy, patient and graft outcome remains poor and retransplantation is often required. 21 Consequently, preventing HAT by optimizing anastomosis techniques seems of high importance for successful pLT. In our analysis, HAT occurrence was independently associated with DDLT and HAR with SL. Comparable to our data, HAT rates in pLT are reported to be 6-fold higher after DDLT than LDLT. 22,23 Unfortunately, the causes for increased HAT rates in DDLT are still unknown. 22 In our cohort, HAT rate was 24.1% and occurred only in pLT with HAR using SL. These results are at the upper end of published HAT rates in the literature. 22,24 Possible explanations are not only the already mentioned use of DDLT, but also the inclusion of retransplantations in our study. Regardless of the considerably high HAT rates in the SL group, our data support the idea that HAT occurrence can be significantly reduced, or-as shown in this case-series-entirely avoided in pLT by using an OM. [7][8][9] Therefore, HAR performed by a plastic surgeon using an OM appears to be a logical step, and many authors suggest the use of an OM for HAR in pLT. 4,13,25,26 Still, its implementation has not fully been established in most pLT programs due to multiple reasons. First, this technique requires higher logistical and personnel resources, which can be a significant limitation for many centers.
The set-up of the OM takes between 5 and 15 min with trained staff. Several aspects must be taken into account, when arranging the anastomotic field: HAR in LDLT can be substantially more complex than in DDLT due to a short and narrow hepatic artery of the graft, vessel size discrepancy between donor and recipient, anatomical variations (e.g., multiple branching) as well as a deep anastomotic field. For this reason, many surgical techniques have been described to facilitate anastomosis in the setting of pLT. 14,27 TA B L E 1 Epidemiological, clinical, and operative data of pLTs (<16 years of age) performed between 2009 and 2020 divided into hepatic artery reconstruction with OM and SL Some historical results suggested that reconstruction of all artery branches in pLT is not always necessary, as an adequate graft supply can often be achieved by anastomosis of one main artery. 28 Our center's strategy is to perform HAR of all hepatic branches if anatomically possible. In addition-to reduce WIT-the recon-  6.9% in the SL group) did not differ significantly between groups.
Our data strengthen the suggestion that the advantage of a pre- Despite the limitations mentioned above, our manuscript demonstrates the advantages of HAR using OM.

| CON CLUS ION
HAR using OM was identified as an independent risk factor for HAT.

CO N FLI C T O F I NTE R E S T
The authors declare no conflicts of interest.

AUTH O R CO NTR I B UTI O N
All authors have made substantial contributions to the study and approved the submitted manuscript. TD collected the data, drafted and wrote the manuscript, designed and performed the research. CW and RÖ designed the research, interpreted the data, and critically revised the manuscript.

DATA AVA I L A B I L I T Y S TAT E M E N T
Data are available on request due to privacy/ethical restrictions.

TA B L E 3
Multiple linear regression analyses of perioperative independent risk factors for the development of HAT