Life-supporting human complement regulator decay accelerating factor transgenic pig liver xenograft maintains the metabolic function and coagulation in the nonhuman primate for up to 8 days

BACKGROUND

It is not known whether the pig liver is capable of functioning efficiently when transplanted into a primate, neither is there experience in transplanting a liver from a transgenic pigs expressing the human complement regulator human complement regulator decay accelerating factor (h-DAF) into a baboon. The objective of this study was to determine whether the porcine liver would support the metabolic functions of non-human primates and to establish the effect of hDAF expression in the prevention of hyperacute rejection of porcine livers transplanted into primates.

METHODS

Five orthotopic liver xenotransplants from pig to baboon were carried out: three from unmodified pigs and two using livers from h-DAF transgenic pigs.

FINDINGS

The three control animals transplanted with livers from unmodified pigs survived for less than 12 hr. Baboons transplanted with livers from h-DAF transgenic pigs survived for 4 and 8 days. Hyperacute rejection was not detected in the baboons transplanted with hDAF transgenic pig livers; however, it was demonstrated in the three transplants from unmodified pigs. Baboons transplanted with livers from h-DAF transgenic pigs were extubated at postoperative day 1 and were awake and able to eat and drink. In the recipients of hDAF transgenic pig livers the clotting parameters reached nearly normal levels at day 2 after transplantation and remained normal up to the end of the experiments. In these hDAF liver recipients, porcine fibrinogen was first detected in the baboon plasma 2 hr postreperfusion, and was present up to the end of the experiments. One animal was euthanized at day 8 after development of sepsis and coagulopathy, the other animal arrested at day 4, after an episode of vomiting and aspiration. The postmortem examination of the hDAF transgenic liver xenografts did not demonstrate rejection.

INTERPRETATION

The livers from h-DAF transgenic pigs did not undergo hyperacute rejection after orthotopic xenotransplantation in baboons. When HAR is abrogated, the porcine liver maintains sufficient coagulation and protein levels in the baboon up to 8 days after OLT.

Tranexamic acid reduces red cell transfusion better than epsilon-aminocaproic acid or placebo in liver transplantation

We evaluated the efficacy of the prophylactic administration of epsilon-aminocaproic acid and tranexamic acid for reducing blood product requirements in orthotopic liver transplantation (OLT) in a prospective, double-blinded study performed in 132 consecutive patients. Patients were randomized to three groups and given one of three drugs prophylactically: tranexamic acid, 10 mg. kg(-1). h(-1); epsilon-aminocaproic acid, 16 mg. kg(-1). h(-1), and placebo (isotonic saline). Perioperative management was standardized. Coagulation tests, thromboelastogram, and blood requirements were recorded during OLT and in the first 24 h. There were no differences in diagnosis, Child score, or preoperative coagulation tests among groups. Administration of packed red blood cells was significantly reduced (P = 0.023) during OLT in the tranexamic acid group, but not in the epsilon-aminocaproic acid group. There were no differences in transfusion requirements after OLT. Thromboembolic events, reoperations, and mortality were similar in the three groups. Prophylactic administration of tranexamic acid, but not epsilon-aminocaproic acid, significantly reduces total packed red blood cell usage during OLT.

IMPLICATIONS

In a randomized study of 132 consecutive patients undergoing liver transplantation, we found that tranexamic acid, but not epsilon-aminocaproic acid, reduced intraoperative total packed red blood cell transfusion.

Serum ionized magnesium monitoring during orthotopic liver transplantation

During orthotopic liver transplantation (OLT) citrate accumulates and magnesium can be chelated, which can lead to ionized hypomagnesemia and cardiovascular dysfunction. Our aim was to study the serum ionized magnesium (Me2+) evolution and establish its relation to serum total Mg and citrate levels during OLT. We studied 58 adult patients undergoing OLT. The serum Me2+ level dropped significantly at the end of the preanhepatic phase, and remained low until the end of the procedure. Furthermore, the Me2+ levels remained below the range of reference from the beginning of the anhepatic phase onward. There was an inverse correlation between Me2+ and citrate for all patients. Me2+, like ionized calcium (Ca2+), is chelated by citrate and its evolution is a mirror image of that of citrate. In our patients, we did not observe any significant dysrhythmias that could be directly attributed to ionized hypomagnesemia. In conclusion, low preoperative levels, together with the massive transfusion of blood products and the increase in renal losses, cause progressive ionized hypomagnesemia in OLT patients. We propose that it he routinely monitored and treated accordingly, as is already done with Ca2+.