Continuous Renal Replacement Therapy (CRRT) in Surgery Room During Orthotopic Liver Transplantation (OLT)

The study is interventional, non-pharmacological, single-center. The clinical practice adopted to date provides that upon arrival of the liver to be transplanted, dialysis is interrupted before entering the surgery room, and then resumed, if necessary, upon exiting the room. The aim of this study is to test the possible added value of CRRT in the surgery room during liver transplantation, compared to the investigators center current practice. The incidence of some clinical and metabolic alterations that often complicate transplantation in the absence of CRRT will be evaluated, by measuring a series of parameters related to the state of water filling, acid-base balance, general metabolic structure, hemodynamics and supportive drugs. Some parameters related to patient safety will be evaluated.

For each patient enrolled in the study, the following will be collected:

baseline data (taken before entering the operating room), intraoperative data, postoperative data for the first 48 hours, and data at 3 and 6 months after surgery.

Baseline data:

• demographic data: age, sex
• anamnestic data: etiology of liver disease (viral, alcoholic, neoplastic, other); state of liver disease (acute, acute on chronic, cirrhosis, decompensated cirrhosis); etiology of acute kidney injury (sepsis, hypovolemia/hemorrhage, iatrogenic/drugs, hepatorenal syndrome, other); indication for dialysis treatment (uremia, electrolyte imbalance, acidosis, oligo-anuria, fluid overload, other)
• biochemical parameters (as indicated in the "Objectives" paragraph): pH, HCO3, pO2, pCO2, BE, P/F ratio, DO2, SVO2; hemoglobin, hematocrit, sodium, potassium, calcium, lactate, CPK, ammonium, glycemia
• Hemodynamic parameters: heart rate, mean arterial pressure, cardiac output, peripheral vascular resistance, central venous pressure, pulmonary wedge pressure, stroke volume
• Severity scores: MELD and SOFA pre- and post-intervention
• Other clinical data: amine infusion (YES/NO), mechanical ventilation (YES/NO), urine output (volume/minute), radiological signs of pulmonary congestion/edema (YES/NO).

Intra- and post-operative data:

The biochemical, hemodynamic and clinical parameters listed above will be recorded at the following times:

• at the induction of anesthesia
• in the anhepatic phase
• at 5, 30 and 120 and 180 minutes after reperfusion
• at the end of surgery
• at 24 and 48 hours after leaving the operating room The following will also be reported: intraoperative onset of arrhythmia (YES/NO), intraoperative coagulation of the extracorporeal circuit (YES/NO), intraoperative replacement of the extracorporeal circuit for TMP>200 (YES/NO), onset of hypophosphatemia (\<2.5 mg\dl) and hypocalcemia (calcium ion \<0.9 mmol\l) hypercalcemia (calcium ion \<1.3 mmol\l) assessed at the end of surgery.

Data 3 and 6 months post intervention:

• survival
• INR
• Bilirubin
• Creatinine
• GFR

CRRT protocol:

The extracorporeal renal function replacement treatment modality adopted in the population under study is continuous veno-venous hemodiafiltration (CVVHDF) without anticoagulation. The Prismax® Baxter monitor will be used. A commercially available dialysis solution will be used and in particular: Prismasol 2 ® Baxter used both as dialysate and as post-dilution reinfusion, blood flow 150 ml/min; dialysis dose initially prescribed 30-35 ml/min which may be increased during treatment if necessary to obtain better metabolic/electrolytic control.

During the transplant, a dialysis nurse will be present in the surgery room for the entire duration of the operation. At the end of the operation, CRRT will continue in Intensive Care Unit.

The results of this exploratory study will be useful to document what was rationally hypothesized, that is, that the continuation of dialysis treatment even during the hours of surgery, in this narrow category of patients, is actually useful to reduce the possible clinical and metabolic complications, intra- and/or post-operative (within 48 hours of transplant), linked to the simultaneous presence of renal failure.

The statistical analysis is aimed at analyzing the behavior of different indicators of clinical complications and comparing them with what was found in the historical series, in the hypothesis that with the new procedure the analyzed parameters are better. In detail, the mean values at the end of treatment will be compared for:

• Central venous pressure
• Potassiemia
• Lactatemia
• pH

The following will also be evaluated:

• dose of vasoconstrictor drugs, defined by the variation between the dose at the beginning of administration during the anhepatic phase and the maximum dose reached
• pulmonary congestion/pulmonary edema, defined by radiological signs of alveolar congestion/edema on chest X-ray in the post-surgery period
• safety parameters: episodes of hypokalemia requiring supplementation (K\<3.5 mmol/l), post-surgery hypophosphatemia, number of coagulation events in the extracorporeal circuit, appearance of cardiac arrhythmias.