Intraoperative Blood Flow Measurements and Liver Allograft Function: Preliminary Results

Transit time ultrasound perivascular flow probe technology is superior to MR imaging on hepatic blood flow measurement in a porcine model

BACKGROUND

The hepatic hemodynamics is an essential parameter in surgical planning as well as in various disease processes. The transit time ultrasound (TTUS) perivascular flow probe technology is widely used in clinical practice to evaluate the hepatic inflow, yet invasive. The phase-contrast-MRI (PC-MRI) is not invasive and potentially applicable in assessing the hepatic blood flow. In the present study, we compared the hepatic inflow rates using the PC-MRI and the TTUS probe, and evaluated their predictive value of post-hepatectomy adverse events.

METHODS

Eighteen large white pigs were anaesthetized for PC-MRI and approximately 75% hepatic resection was performed under a unified protocol. The blood flow was measured in the hepatic artery (Qha), the portal vein (Qpv), and the aorta above the celiac trunk (Qca) using PC-MRI, and was compared to the TTUS probe. The Bland-Altman method was conducted and a partial least squares regression (PLS) model was implemented.

RESULTS

The mean Qpv measured in PC-MRI was 0.55 ± 0.12 L/min, and in the TTUS probe was 0.74 ± 0.17 L/min. Qca was 1.40 ± 0.47 L/min in the PC-MRI and 2.00 ± 0.60 L/min in the TTUS probe. Qha was 0.17 ± 0.10 L/min in the PC-MRI, and 0.13 ± 0.06 L/min in the TTUS probe. The Bland-Altman method revealed that the estimated bias of Qca in the PC-MRI was 32% (95% CI: -49% to 15%); Qha 17% (95% CI: -15% to 51%); and Qpv 40% (95% CI: -62% to 18%). The TTUS probe had a higher weight in predicting adverse outcomes after 75% resection compared to the PC-MRI (β= 0.35 and 0.43 vs β = 0.22 and 0.07, for tissue changes and premature death, respectively).

CONCLUSIONS

There is a tendency of the PC-MRI to underestimate the flow measured by the TTUS probes. The TTUS probe measures are more predictive of relevant post-hepatectomy outcomes.

Intraoperative Portal Vein Flow > 123 mL/min Per 100 g Predicts a Better Survival of Patients After Liver Transplantation

OBJECTIVE

To assess the importance of intraoperative portal vein flow measurement during liver transplantation in relation to postoperative complications and graft and patient survival.

MATERIALS AND METHODS

Retrospective review including 291 patients who had all the information and covering a period of 10 years (2007-2017). Using a receiver operating characteristic curve, a cut-off point that would have the greatest impact on the probability of being alive at 5 years was established. In relation to this value, 2 groups were formed (low and high flow) and demographic variables, intraoperative variables, postoperative complications, and graft and patient survival were compared.

RESULTS

A portal flow of 123 mL/min per100 g of liver tissue was established (area under the curve = 0.58), obtaining a low-flow (n = 129) and a high-flow group (n = 162). The 2 groups were similar in their preoperative characteristics, except for a higher proportion of preoperative ascites, a higher Model for End-Stage Liver Disease score and a lower weight of donors in the high-flow group. The arterial and portal flows were significantly higher in the high-flow group. In the postoperative period, the high-flow group presented a higher rate of ascites. The 5-year survival rate of patients was significantly higher in the high-flow group (76% vs 84%, P = .03).

CONCLUSIONS

Patients undergoing liver transplantation with an intraoperative portal vein flow measurement >123 mL/min per 100 g present a greater 5-year survival rate.

A Case of Left Renal Vein Ligation in a Patient with Solitary Left Kidney Undergoing Liver Transplantation to Control Splenorenal Shunt and Improve Portal Venous Flow

Patient: Male, 51

Final Diagnosis: Liver cirrhosis by hepatitis virus C and hepatocellular carcinoma

Symptoms: Ascites

Medication: —

Clinical Procedure: Liver transplantantion

Specialty: Surgery

Left renal vein ligation: a technique to mitigate low portal flow from splenic vein siphon during liver transplantation

Low portal vein flows in liver transplant have been associated with poor allograft survival. Identifying and ameliorating causes of inadequate portal flow is paramount. We describe successful reversal of significant splenic vein siphon from a spontaneous splenorenal shunt during liver transplant. The patient is a 43-year-old male with cirrhosis from hepatitis C and Budd-Chiari syndrome, who had a variceal hemorrhage necessitating an emergent splenorenal shunt with 8 mm PTFE graft. Imaging in 2006 revealed thrombosis of the splenorenal shunt and evidence of a new spontaneous splenorenal shunt. The patient developed hepatocellular carcinoma and underwent transplant in 2009. After reperfusion, portal flows were low (150-200 mL/min). A mesenteric varix was ligated without improvement. Due to adhesions, direct collateral ligation was not attempted. In order to redirect the splenic siphon, the left renal vein was stapled at its confluence with the inferior vena cava. Portal flows subsequently increased to 1.28 L/min. Postoperatively, the patient had stable renal and liver function. We conclude that spontaneous splenorenal shunts can cause low portal flows. A diligent search for shunts with understanding of flow patterns is critical; ligation or rerouting of splanchnic flow may be necessary to improve portal flows and allograft outcomes.

Prospective evaluation of intraoperative hemodynamics in liver transplantation with whole, partial and DCD grafts

The interaction of systemic hemodynamics with hepatic flows at the time of liver transplantation (LT) has not been studied in a prospective uniform way for different types of grafts. We prospectively evaluated intraoperative hemodynamics of 103 whole and partial LT. Liver graft hemodynamics were measured using the ultrasound transit time method to obtain portal (PVF) and arterial (HAF) hepatic flow. Measurements were recorded on the native liver, the portocaval shunt, following reperfusion and after biliary anastomosis. After LT HAF and PVF do not immediately return to normal values. Increased PVF was observed after graft implantation. Living donor LT showed the highest compliance to portal hyperperfusion. The amount of liver perfusion seemed to be related to the quality of the graft. A positive correlation for HAF, PVF and total hepatic blood flow with cardiac output was found (p = 0.001). Portal hypertension, macrosteatosis >30%, warm ischemia time and cardiac output, independently influence the hepatic flows. These results highlight the role of systemic hemodynamic management in LT to optimize hepatic perfusion, particularly in LDLT and split LT, where the highest flows were registered.

Early noninvasive measurement of the indocyanine green plasma disappearance rate accurately predicts early graft dysfunction and mortality after deceased donor liver transplantation

Early diagnosis of graft dysfunction in liver transplantation is essential for taking appropriate action. Indocyanine green clearance is closely related to liver function and can be measured noninvasively by spectrophotometry. The objectives of this study were to prospectively analyze the relationship between the indocyanine green plasma disappearance rate (ICGPDR) and early graft function after liver transplantation and to evaluate the role of ICGPDR in the prediction of severe graft dysfunction (SGD). One hundred seventy-two liver transplants from deceased donors were analyzed. Ten patients had SGD: 6 were retransplanted, and 4 died while waiting for a new graft. The plasma disappearance rate was measured 1 hour (PDRr60) and within the first 24 hours (PDR1) after reperfusion, and it was significantly lower in the SGD group. PDRr60 and PDR1 were excellent predictors of SGD. A threshold PDRr60 value of 10.8%/minute and a PDR1 value of 10%/minute accurately predicted SGD with areas under the receiver operating curve of 0.94 (95% confidence interval, 0.89-0.97) and 0.96 (95% confidence interval, 0.92-0.98), respectively. In addition, survival was significantly lower in patients with PDRr60 values below 10.8%/minute (53%, 47%, and 47% versus 95%, 94%, and 90% at 3, 6, and 12 months, respectively) and with PDR1 values below 10%/minute (62%, 62%, and 62% versus 94%, 92%, and 88%). In conclusion, very early noninvasive measurement of ICGPDR can accurately predict early severe graft dysfunction and mortality after liver transplantation.

Mensuração do volume de fluxo portal em pacientes esquistossomóticos: avaliação da reprodutibilidade do ultra-som Doppler

OBJETIVO: Avaliar a reprodutibilidade do ultra-som Doppler na quantificação do volume de fluxo portal em pacientes esquistossomóticos. MATERIAIS E MÉTODOS: Estudo prospectivo, transversal, observacional e autopareado, avaliando 21 pacientes portadores de esquistossomose hepatoesplênica, submetidos a mensuração do fluxo portal pelo ultra-som Doppler por três observadores, de forma independente, sendo calculada a concordância entre estes, dois a dois, pelo coeficiente de correlação intraclasse, teste t-pareado e grau de linearidade de Pearson. RESULTADOS: A concordância interobservador foi excelente. O coeficiente de correlação intraclasse variou entre 80,6% e 93,0% (IC a 95% [65,3% ; 95,8%]), com coeficiente de correlação de Pearson variando entre 81,6% e 92,7% e sem diferença estatisticamente significante entre os observadores quanto à média do fluxo portal mensurado pelo ultra-som Doppler (p = 0,954 / 0,758 / 0,749). CONCLUSÃO: O ultra-som Doppler é um método confiável para quantificar o fluxo portal em pacientes portadores de hipertensão porta de origem esquistossomótica, apresentando boa concordância interobservador.