Pro: low central venous pressure during liver transplantation--not too low

Association of Phlebotomy on Blood Product Transfusion Requirements During Liver Transplantation: An Observational Cohort Study on 1000 Cases

Background

During the past 2 decades, transfusion requirements have decreased drastically during orthotopic liver transplantation (OLT), and transfusion-free transplantation is nowadays increasingly common. Understanding that liberal intravenous volume loading in cirrhotic patients may have detrimental consequences is key. In contrast, phlebotomy is a method to lower central venous pressure and portal venous pressure. The objective of this study was to determine the effectiveness and safety of phlebotomy in the early phase of blood transfusion, blood loss, renal function, and mortality.

Methods

The present study evaluated the impact of phlebotomy on bleeding, transfusion rate, renal dysfunction, and mortality in 1000 consecutive OLTs. Two groups were defined and compared using phlebotomy. Multivariate logistic and linear regression models were used to determine predictors of bleeding, red blood cell (RBC) transfusion, renal dysfunction, and mortality.

Results

A mean of 0.7 ± 1.5 RBC units was transfused per patient for 1000 OLTs, 75% did not receive any RBCs, and the median and interquartile range (25-75) were 0 for all blood products transfused. The phlebotomy was associated with decreased transfusion (RBCs, plasma, platelets, cryoprecipitate, albumin), with less bleeding, and with an increased survival rate, both 1 mo and 1 y. Phlebotomy was not associated with renal dysfunction.

Conclusions

The practice of phlebotomy to lower portal venous pressure was associated with reduced blood product transfusions and blood loss during liver dissection without deleterious effect on renal function.

Liver Transplantation

The field of liver transplantation has changed since the MELD scoring system became the most widely used donor allocation tool. Due to the MELD-based allocation system, sicker patients with higher MELD scores are being transplanted. Persistent organ donor shortages remain a challenging issue, and as a result, the wait-list mortality is a persistent problem for most of the regions. This chapter focuses on deceased donor and live donor liver transplantation in patients with complications of portal hypertension. Special attention will also be placed on donor-recipient matching, perioperative management of transplant patients, and the impact of hepatic hemodynamics on transplantation.

Prediction of postoperative outcomes using intraoperative hemodynamic monitoring data

Major surgeries can result in high rates of adverse postoperative events. Reliable prediction of which patient might be at risk for such events may help guide peri- and postoperative care. We show how archiving and mining of intraoperative hemodynamic data in orthotopic liver transplantation (OLT) can aid in the prediction of postoperative 180-day mortality and acute renal failure (ARF), improving upon predictions that rely on preoperative information only. From 101 patient records, we extracted 15 preoperative features from clinical records and 41 features from intraoperative hemodynamic signals. We used logistic regression with leave-one-out cross-validation to predict outcomes, and incorporated methods to limit potential model instabilities from feature multicollinearity. Using only preoperative features, mortality prediction achieved an area under the receiver operating characteristic curve (AUC) of 0.53 (95% CI: 0.44–0.78). By using intraoperative features, performance improved significantly to 0.82 (95% CI: 0.56–0.91, P = 0.001). Similarly, including intraoperative features (AUC = 0.82; 95% CI: 0.66–0.94) in ARF prediction improved performance over preoperative features (AUC = 0.72; 95% CI: 0.50–0.85), though not significantly (P = 0.32). We conclude that inclusion of intraoperative hemodynamic features significantly improves prediction of postoperative events in OLT. Features strongly associated with occurrence of both outcomes included greater intraoperative central venous pressure and greater transfusion volumes.

Reducing transfusion requirements in liver transplantation

Liver transplantation (LT) was historically associated with massive blood loss and transfusion. Over the past two decades transfusion requirements have reduced dramatically and increasingly transfusion-free transplantation is a reality. Both bleeding and transfusion are associated with adverse outcomes in LT. Minimising bleeding and reducing unnecessary transfusions are therefore key goals in the perioperative period. As the understanding of the causes of bleeding has evolved so too have techniques to minimize or reduce the impact of blood loss. Surgical “piggyback” techniques, anaesthetic low central venous pressure and haemodilution strategies and the use of autologous cell salvage, point of care monitoring and targeted correction of coagulopathy, particularly through use of factor concentrates, have all contributed to declining reliance on allogenic blood products. Pre-emptive management of preoperative anaemia and adoption of more restrictive transfusion thresholds is increasingly common as patient blood management (PBM) gains momentum. Despite progress, increasing use of marginal grafts and transplantation of sicker recipients will continue to present new challenges in bleeding and transfusion management. Variation in practice across different centres and within the literature demonstrates the current lack of clear transfusion guidance. In this article we summarise the causes and predictors of bleeding and present the evidence for a variety of PBM strategies in LT.

Predicting fluid responsiveness in patients undergoing orthotopic liver transplantation: effects on intraoperative blood transfusion and postoperative complications

OBJECTIVE

To test the hypothesis that the restrictive volume therapy decreases blood transfusion requirement during liver orthotopic transplantation (OLT) without increasing acute renal complications and hospital length stay.

MATERIAL AND METHODS

We conducted a retrospective cohort study (n = 89), randomized into 2 groups: A (liberal fluid strategy) and B (restrictive therapy). We analyzed packed red blood cells (PRBCs) units, transfused units of fresh frozen plasma (FFP), colloids, crystalloids, perioperative renal function, and hospital length stay. For comparison of proportions, we used the χ(2) test and Student t test to compare means (parametric). A logistic regression model was constructed to evaluate the association of all these variables with probability of PRBCs transfusion.

RESULTS

In group A, 88.4% of patients required intraoperative transfusion of PRBCs, with a mean of 8.5 ± 7.02 IU, compared with 82.2% in group B with a mean of 5.02 ± 4.5 IU (P < .001). We also found differences in the following variables: FFP transfusion rate was 95.3% (mean, 15.02 ± 8.2 IU) in group A and 75.6% (mean, 8.7 ± 6.04 IU) in B (P < .001). The amount of colloid was 50% (mean, 692.8 ± 409.6 mL) in group A and 28.9% (mean, 607.6 ± 316.7 mL) in B (P = .032). Platelet concentrates transfusion was 79.1% (mean, 2.05 ± 1.1 IU) in group A and 51.1% (mean, 2.0 ± 1.08 IU) in B (P = .014). As an important effect of restrictive fluid therapy, renal function was assessed; no differences in mean creatinine or acute renal failure in the immediate postoperative period were observed. There was no difference in hospital length stay. Logistic regression modelling identified 3 variables as significant predictors of transfusion: Fluid administration policy, preoperative hemoglobin and FFP units transfused. Furthermore, an increase of preoperative hemoglobin is associated with a lesser probability of transfusion.

CONCLUSIONS

These results show that fluid restriction management for OLT decreased blood products requirements, especially FFP. This could suggest that liberal fluid management may aggravate, rather than prevent, bleeding in these patients. We did observed any no difference in failure of renal function.

The hydrostatic pressure indifference point underestimates orthostatic redistribution of blood in humans

The hydrostatic indifference point (HIP; where venous pressure is unaffected by posture) is located at the level of the diaphragm and is believed to indicate the orthostatic redistribution of blood, but it remains unknown whether HIP coincides with the indifference point for blood volume (VIP). During graded (± 20°) head-up (HUT) and head-down tilt (HDT) in 12 male volunteers, we determined HIP from central venous pressure and VIP from redistribution of both blood, using ultrasound imaging of the inferior caval vein (VIPui), and fluid volume, by regional electrical admittance (VIPadm). Furthermore, we evaluated whether inflation of medical antishock trousers (to 70 mmHg) affected HIP and VIP. Leaving cardiovascular variables unaffected by tilt, HIP was located 7 ± 4 cm (mean ± SD) below the 4th intercostal space (IC-4) during HUT and was similar (7 ± 3 cm) during HDT and higher (P < 0.0001) than both VIPui (HUT: 22 ± 16 cm; HDT: 13 ± 7 cm) and VIPadm (HUT: 29 ± 9 cm; HDT: 20 ± 9 cm below IC-4). During HUT antishock trousers elevated both HIP and VIPui [to 3 ± 5 cm (P = 0.028) and 17 ± 7 cm below IC-4 (P = 0.051), respectively], while VIPadm remained unaffected. By simultaneous recording of pressure and filling of the inferior caval vein as well as fluid distribution, we found HIP located corresponding to the diaphragm while VIP was placed low in the abdomen, and that medical antishock trousers elevated both HIP and VIP. The low indifference point for volume shows that the gravitational influence on distribution of blood is more profound than indicated by the indifference point for venous pressure.

Blood loss, predictors of bleeding, transfusion practice and strategies of blood cell salvaging during liver transplantation

Blood loss during liver transplantation (OLTx) is a common consequence of pre-existing abnormalities of the hemostatic system, portal hypertension with multiple collateral vessels, portal vein thrombosis, previous abdominal surgery, splenomegaly, and poor “functional” recovery of the new liver. The intrinsic coagulopathic features of end stage cirrhosis along with surgical technical difficulties make transfusion-free liver transplantation a major challenge, and, despite the improvements in understanding of intraoperative coagulation profiles and strategies to control blood loss, the requirements for blood or blood products remains high. The impact of blood transfusion has been shown to be significant and independent of other well-known predictors of posttransplant-outcome. Negative effects on immunomodulation and an increased risk of postoperative complications and mortality have been repeatedly demonstrated. Isovolemic hemodilution, the extensive utilization of thromboelastogram and the use of autotransfusion devices are among the commonly adopted procedures to limit the amount of blood transfusion. The use of intraoperative blood salvage and autologous blood transfusion should still be considered an important method to reduce the need for allogenic blood and the associated complications. In this article we report on the common preoperative and intraoperative factors contributing to blood loss, intraoperative transfusion practices, anesthesiologic and surgical strategies to prevent blood loss, and on intraoperative blood salvaging techniques and autologous blood transfusion. Even though the advances in surgical technique and anesthetic management, as well as a better understanding of the risk factors, have resulted in a steady decrease in intraoperative bleeding, most patients still bleed extensively. Blood transfusion therapy is still a critical feature during OLTx and various studies have shown a large variability in the use of blood products among different centers and even among individual anesthesiologists within the same center. Unfortunately, despite the large number of OLTx performed each year, there is still paucity of large randomized, multicentre, and controlled studies which indicate how to prevent bleeding, the transfusion needs and thresholds, and the “evidence based” perioperative strategies to reduce the amount of transfusion.

Utility of uncalibrated femoral stroke volume variation as a predictor of fluid responsiveness during the anhepatic phase of liver transplantation

We evaluated the value of the stroke volume variation (SVV) calculated with the Vigileo monitor, which recently has been increasingly advocated for fluid management, as a predictor of fluid responsiveness during the anhepatic phase of liver transplantation (LT). We also compared SVV to the central venous pressure (CVP) and pulmonary arterial occlusion pressure (PAOP) in patients. Thirty-three adult recipients scheduled for elective living donor LT were enrolled in this study. Twenty minutes after the start of the anhepatic phase, the CVP, PAOP, approximate inferior vena caval pressure, femoral SVV, and cardiac output values were measured before and 12 minutes after fluid loading. Fluid loading was performed with a 6% hydroxyethyl starch solution (10 mL/kg). The responders were defined as patients whose cardiac index increased ≥ 15% after fluid loading. Receiver operating characteristic (ROC) analysis showed that only femoral SVV (area under the curve = 0.894, P = 0.0001) could be used to predict fluid responsiveness during the anhepatic phase of LT. The area under the ROC curve for femoral SVV was 0.894 (P = 0.0001), and it was significantly larger than those for CVP (area under the curve = 0.576, P = 0.004) and PAOP (area under the curve = 0.670, P = 0.021). Femoral SVV >8% identified the responders with a sensitivity of 89% and a specificity of 80%. Our results suggest that femoral SVV derived with the Vigileo monitor would be useful for fluid management during the anhepatic phase in LT recipients.

Effects of low central venous pressure during preanhepatic phase on blood loss and liver and renal function in liver transplantation

BACKGROUND

Although the low central venous pressure (LCVP) technique is used to decrease blood loss during liver resection, its efficacy and safety during transplant procedures are still debatable. Our study aimed to assess the effects of this technique and its clinical safety for recipients undergoing liver transplantation.

METHODS

Eighty-six adult patients were randomly divided into a LCVP group and a control group. In the LCVP group, CVP was maintained below 5 mmHg or 40% lower than baseline during the preanhepatic phase by limiting infusion volume, manipulating the patient's posture, and administration of somatostatin and nitroglycerine. Recipients in the control group received standard care. Hemodynamics, blood loss, liver function, and renal function of the two groups were compared perioperatively.

RESULTS

A lower CVP was maintained in the LCVP group during the preanhepatic phase, resulting in a significant decrease in blood loss (1922 +/- 1429 vs. 3111 +/- 1833 ml, P < 0.05) and transfusion volume (1200 +/- 800 vs. 2400 +/- 1200 ml, P < 0.05) intraoperatively. Compared with the control group, the LCVP group had a significantly lower mean arterial pressure at 2 h after the start of the operation (74 +/- 11 vs. 84 +/- 14 mmHg, P < 0.05), a lower lactate value at the end of the operation (5.9 +/- 3.0 vs. 7.2 +/- 3.0 mmol/l, P < 0.05), and a better preservation of liver function after the declamping of the portal vein. There were no significant differences in perioperative renal function and postoperative complications between the groups.

CONCLUSIONS

The LCVP technique during the preanhepatic phase reduced intraoperative blood loss, protected liver function, and had no detrimental effects on renal function in LT.

Effects of phlebotomy and phenylephrine infusion on portal venous pressure and systemic hemodynamics during liver transplantation

BACKGROUND

A regimen of fluid restriction, phlebotomy, vasopressors, and strict, protocol-guided product replacement has been associated with low blood product use during orthotopic liver transplantation. However, the physiologic basis of this strategy remains unclear. We hypothesized that a reduction of intravascular volume by phlebotomy would cause a decrease in portal venous pressure (PVP), which would be sustained during subsequent phenylephrine infusion, possibly explaining reduced bleeding. Because phenylephrine may increase central venous pressure (CVP), we questioned the validity of CVP as a correlate of cardiac filling in this context and compared it with other pulmonary artery catheter and transesophageal echocardiography-derived parameters. In particular, because optimal views for echocardiographic estimation of preload and stroke volume are not always applicable during liver transplantation, we evaluated the use of transmitral flow (TMF) early peak (E) velocity as a surrogate.

METHODS

In study 1, the changes in directly measured PVP and CVP were recorded before and after phlebotomy and phenylephrine infusion in 10 patients near the end of the dissection phase of liver transplantation. In study 2, transesophageal echocardiography-derived TMF velocity in early diastole was measured in 20 patients, and the changes were compared with changes in CVP, pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), cardiac output (CO), and calculated systemic vascular resistance (SVR) at the following times: postinduction, postphlebotomy, preclamping of the inferior vena cava, during clamping, and postunclamping.

RESULTS

Phlebotomy decreased PVP along with CO, PAP, PCWP, CVP, and TMF E velocity. Phenylephrine given after phlebotomy increased CVP, SVR, and arterial blood pressure but had no significant effect on CO, PAP, PCWP, or PVP. The change in TMF E velocity correlated well with the change in CO (Pearson correlation coefficient 95% confidence interval 0.738-0.917, P< or =0.015) but less well with the change in PAP (0.554-0.762, P< or =0.012) and PCWP (0.576-0.692, P< or =0.008). TMF E velocity did not correlate significantly with CVP or calculated SVR.

CONCLUSION

Phlebotomy during the dissection phase of liver transplantation decreased PVP, which was unaffected when phenylephrine infusion was used to restore systemic arterial pressure. This may contribute to a decrease in operative blood loss. CVP often increased in response to phenylephrine infusion and did not seem to reflect cardiac filling. The changes in TMF E velocity correlated well with the changes in CO, PAP, and PCWP during liver transplantation but not with the changes in CVP.

MELD score and blood product requirements during liver transplantation: no link

BACKGROUND

Orthotopic liver transplantation has been traditionally associated with major blood loss and the need for allogenic blood product transfusions. In recent years, improvements in surgical and anesthetic techniques have greatly decreased the amount of blood products transfused. We have published a median of 0 for all intraoperative blood products transfused. Some authors argue that these results could be possible merely because of the relatively healthy cohort in terms of model of end-stage liver disease (MELD) score. The MELD score could be adjusted by some conditions (hepatocellular carcinoma, hemodialysis, hepatopulmonary syndrome, and amyloidosis) and was not adjusted in these series. The goal of this work was to verify the MELD score according to US standards and to find any link between the MELD score and the transfusion rate.

METHOD

Three hundred fifty consecutive liver transplantations were studied. The MELD score was adjusted according to US standards. Patients were divided into two groups according to the median of the MELD score. Blood loss and transfusion rate were determined for these two groups. Logistic regression models were used to find any link with transfusion of red blood cell (RBC) units.

RESULT

The MELD score before adjusting was 19+/-9 and 22+/-10 after. A mean of 0.5+/-1.3 RBC units/patient intraoperative were transfused with 80.6% of cases without any blood products. There was no difference for the blood loss (999+/-670 mL vs. 1017+/-885 mL) or the transfusion rate (0.4+/-1.2 vs. 0.5+/-1.4 RBC/patient) between two groups of MELD (<21 or >or=21) or any of its component (creatinine, bilirubin, and international normalized ratio). The logistic regression analysis found that only two variables were linked to RBC transfusion; starting hemoglobin value and phlebotomy.

CONCLUSION

In this series, the MELD score was as high as US series and did not predict blood losses and blood product requirement during liver transplantation. If the MELD system has to be implemented to prioritize orthotopic liver transplantation, it should be revisited, and the starting hemoglobin value should be added to the equation.