Potential use of pharmacological markers to quantitatively assess liver function during liver transplantation surgery

Hepatic function and non-invasive hepatosplanchnic monitoring in patients with abdominal hypertension

A better understanding of intra-abdominal hypertension with relation to the liver is vital to the management of all forms of liver pathophysiology. Supporting good hepatic function within the critically ill patient is important not only in maintaining synthetic function, but also in avoiding the multi-organ complications of liver dysfunction. The resulting reduction in hepato-splanchnic blood flow (HSBF) observed with increasing intra-abdominal pressure has been clearly documented and seen to be exaggerated in animals with established liver disease. Unfortunately the tools required to measure this, remain difficult to apply routinely in the clinical setting and as such goal directed therapy to specifically improve the hepatosplanchnic circulation remains elusive. Given the documented effects of IAP on HSBF and the relatively high incidence of intra-abdominal hypertension and the abdominal compartment syndrome within "liver patients" as a whole, close attention to IAP and timely correction by appropriate medical or surgical means would appear to be essential.

The significance of ICG-R15 in predicting hepatic toxicity in patients receiving radiotherapy for hepatocellular carcinoma

AIM

To evaluate whether the retention rate of indocyanine green 15 min after administration (ICG-R15) could predict radiation hepatotoxicity in patients treated with radiotherapy (RT) for hepatocellular carcinoma (HCC).

METHODS

We retrospectively reviewed data of 146 HCC patients treated with RT between February 1994 and December 2008. The ICG-R15 was measured within 1 month prior to the start of RT. Radiation hepatotoxicity was evaluated by incidence of radiation-induced liver disease (RILD) between 2 weeks and 3 months after completion of RT. We analysed the correlation between the incidence rate of RILD and the ICG-R15 before RT (pre-RT ICG-R15).

RESULTS

The classic and non-classic RILD occurred in 15 patients (10.3%): classic type in five patients (3.4%) and non-classic RILD in 10 patients (6.9%). A positive correlation was shown between the probability of RILD and increase in pre-RT ICG-R15 (P < 0.0001). Univariate analysis indicated that cut-off value of pre-RT ICG-R15 could predict RILD significantly. The incidence of RILD for the patients with 22% or higher pre-RT ICG-R15 levels was 40.7% as compared to 3.4% for those with levels lower than 22% (P < 0.0001). There was no clinical factor that significantly affected RILD in univariate analysis. Multivariate analysis indicated that the pre-RT ICG-R15 value was the only significant factor affecting RILD (P < 0.0001).

CONCLUSION

These results suggest that pre-RT ICG-R15 could be a useful factor in predicting radiation hepatotoxicity in HCC patients treated with RT.

Lidocaïne test for easier and less time consuming assessment of liver function in several hepatic injury models

PURPOSE

In this study, we developed an ex vivo functional assay to assess liver metabolic capacity adapted from the lidocaïne test in rats.

METHODS

Animals used were subjected to different models of liver injury: hypothermic ischemia (H/I, n = 8), ischemia-reperfusion (I/R, n = 8) and CCl4 induced liver cirrhosis (n = 11), and compared with sham operated rats (n = 5). Livers were then extracted and a fragment of whole tissue was incubated with lidocaïne for 15, 30, 60, 120, 240, 360, and 720 min at which both lidocaïne and its major metabolite monoethylglycinexylidide (MEGX) were measured by high performance liquid chromatography (HPLC). A histological study and biochemical assays (transaminase levels) were also performed to further evaluate and confirm our data.

RESULTS

Pharmacokinetic profile of lidocaïne metabolism in sham-operated animals revealed that the maximum concentration of MEGX is achieved at 120 min. Both lidocaïne metabolism and MEGX formation levels were significantly altered in all three models of hepatic injury. The extent of hepatic damage was confirmed by increased levels of transaminase levels and alteration of hepatocyte's structure with areas of necrosis.

CONCLUSION

Our method provides reliable and reproducible results using only a small portion of liver which allows for a fast and easy assessment of liver metabolic capacity. Moreover, our method presents an alternative to the in vivo technique and seems more feasible in a clinical setting.

The LiMAx test: a new liver function test for predicting postoperative outcome in liver surgery

BACKGROUND

Liver failure has remained a major cause of mortality after hepatectomy, but it is difficult to predict preoperatively. This study describes the introduction into clinical practice of the new LiMAx test and provides an algorithm for its use in the clinical management of hepatic tumours.

METHODS

Patients with hepatic tumours and indications for hepatectomy were investigated perioperatively with the LiMAx test. In one patient, analysis of liver volume was carried out with preoperative three-dimensional virtual resection.

RESULTS

A total of 329 patients with hepatic tumours were evaluated for hepatectomy. Blinded preoperative LiMAx values were significantly higher before resection (n= 139; mean 351 microg/kg/h, range 285-451 microg/kg/h) than before refusal (n= 29; mean 299 microg/kg/h, range 223-376 microg/kg/h; P= 0.009). In-hospital mortality rates were 38.1% (8/21 patients), 10.5% (2/19 patients) and 1.0% (1/99 patients) for postoperative LiMAx of <80 microg/kg/h, 80-100 microg/kg/h and >100 microg/kg/h, respectively (P < 0.0001). A decision tree was developed to avoid critical values and its prospective preoperative application revealed a reduction in mortality from 9.4% to 3.4% (P= 0.019).

DISCUSSION

The LiMAx test can validly determine liver function capacity and is feasible in every clinical situation. Combination with virtual resection could enable the calculation of residual liver function. The LiMAx decision tree algorithm for hepatectomy might significantly improve preoperative evaluation and postoperative outcome in liver surgery.

Early diagnosis of primary nonfunction and indication for reoperation after liver transplantation

Initial graft function is a major factor influencing the clinical outcome after liver transplantation (LTX), but a reliable method for assessing and predicting graft dysfunction directly after LTX is not available. Ninety-nine patients undergoing deceased-donor LTX were studied in a prospective pilot study to evaluate the LiMAx test, the indocyanine green test, and conventional biochemical parameters with respect to their sensitivity and prognostic power for the diagnosis of initial graft dysfunction. Patients suffering from initial graft dysfunction (defined as technical complications or primary nonfunction (n = 8)) had significantly decreased LiMAx readouts (43 +/- 18 versus 184 +/- 98 mug/kg/hour, P < 0.001) immediately after LTX. Univariate analysis also showed significant differences for serum bilirubin, ammonia, glutamate dehydrogenase, and the international normalized ratio (P < 0.05), but multivariate analysis revealed LiMAx as the single independent predictor of initial dysfunction (P = 0.008) with an area under the receiver operating characteristic curve (AUROC) of 0.960 (95% confidence interval = 0.921-0.998, P < 0.001). In addition, the diagnosis of primary nonfunction (n = 3) was evaluated with LiMAx and aspartate aminotransferase (AST) activity on the first postoperative day. The calculated AUROC values were 0.992 (0.975-1.0, P = 0.004) for LiMAx and 0.967 (0.929-1.0, P = 0.006) for AST. By a combination of test results obtained directly after LTX and on the first day, LiMAx indicated primary nonfunction with a sensitivity of 1.0 (0.31-1.0) and a positive predictive value of 1.0 (0.31-1.0), whereas AST classification showed a sensitivity of 0.67 (0.13-0.98) and a positive predictive value of 0.29 (0.05-0.70). In conclusion, the assessment of initial graft function using the LiMAx test might be effective for identifying critical complications that could threaten graft survival within 24 hours after LTX.

A prospective study of isolated human hepatocyte function following liver resection for colorectal liver metastases: the effects of prior exposure to chemotherapy

BACKGROUND/AIMS

Chemotherapy is increasingly used prior to resection of colorectal liver metastases, yet few studies have addressed its effect on the viability and function of hepatocytes. This study evaluated the effect of pre-operative chemotherapy on human hepatocytes.

METHODS

Studies were carried out on isolated hepatocytes from 47 patients undergoing hepatectomy for colorectal metastases. The function of drug metabolising enzymes in hepatocytes was assessed in vitro, as well as hepatocyte integrity and culture longevity. These results were compared between patients undergoing no pre-operative chemotherapy (N = 8), 5 fluorouracil (5FU) post-bowel resection (N = 20), and neo-adjuvant 5FU alone (N = 7) or in a combination with oxaliplatin (N = 12).

RESULTS

Average cell viability at isolation determined by trypan blue dye exclusion was 71% with no significant difference between the no chemotherapy or pre-resection chemotherapy groups. There was no significant difference in LDH leakage and cellular ATP content over a 96-h time course between the patient treatment groups. The function of cytochromes P450 (CYP1A2, CYP2A6, CYP2C9, CYP2D6, CYP2E1, CYP3A4) and phase II enzymes (UDP-glucuronosyltransferase and sulphotransferase) was not adversely affected by pre-operative chemotherapy.

CONCLUSIONS

Pre-resection chemotherapy does not impair the function or culture integrity of hepatocytes isolated at the time of liver resection.

The variability of liver graft function and urinary 6beta-hydroxycortisol to cortisol ratio during liver regeneration in liver transplant recipients

The urinary ratio of 6beta-hydroxycortisol to cortisol (6beta-OHF/F) is considered to be the simplest and most practical method for estimation of hepatic cytochrome P450 3A4 (CYP3A4) activity as a non-invasive marker of human in vivo CYP3A4 activity. However, the inter- and intra-individual variability of the urinary 6beta-OHF/F ratio during liver regeneration and the effect of variability on optimal dose of tacrolimus have not yet been clarified. The objective of this study was to clarify the change in the urinary 6beta-OHF/F ratio during liver regeneration and to determine the effect of the liver graft function on the optimal tacrolimus dose in liver transplant recipients. Two liver transplant recipients (one male and one female) and eight healthy volunteers (five males and three females) were enrolled in this study. Urine samples were collected from the recipients from 08.00 hours for 24 h on post-transplant period, 1-10 and 21-30 days postoperatively. In the healthy volunteers, morning spot urine samples were collected at 08.00 hours. The mean urinary 6beta-OHF/F ratio in the immediate postoperative period was significantly low (p < 0.05). However, a marked difference in the regulation of CYP3A4 activity during liver regeneration was found in the two recipients. A significant correlation was found between the urinary 6beta-OHF/F ratio and the C/D ratio of tacrolimus (R = 0.658, p < 0.05). The urinary 6beta-OHF/F ratio is a useful probe for estimating the variability of CYP3A4 activity in liver transplant recipients in early postoperative phase. Future studies should evaluate the clinical usefulness of the urinary 6beta-OHF/F ratio as a predictor of tacrolimus pharmacokinetics in liver transplantation.

Relationship between postoperative erythromycin breath test and early morbidity in liver transplant recipients

BACKGROUND

Interindividual variability in dosage requirements of the calcineurin inhibitor immunosuppressive agents cyclosporine and tacrolimus after liver transplantation may result from differences in the CYP3A activity of the liver graft. Early postoperative erythromycin breath test (ERMBT) is an in vivo measure of graft CYP3A activity. This study evaluates the usefulness of an early postoperative ERMBT in predicting early morbidity in liver transplant recipients.

METHODS

In 26 liver transplant recipients, ERMBT was performed within 2 hr after transplantation. Main end points were the occurrence of cyclosporine and tacrolimus nephrotoxicity, episodes of early graft rejection, early graft function, and graft survival.

RESULTS

Cyclosporine and tacrolimus nephrotoxicity were associated with low postoperative ERMBT values (mean 0.63%+/-0.25% 14C/hr vs. 1.35%+/-0.84% 14C/hr, P=0.02). No significant association between early graft rejection and ERMBT values was demonstrated. There was a significant inverse correlation between postoperative ERMBT values and the time to normalization of international normalized ratio as a measure of early graft function (r=-0.78, P<0.001). Graft loss was associated with low postoperative ERMBT values (0.21%+/-0.15% 14C/hr vs. 1.09%+/-0.72% 14C/hr, P=0.002).

CONCLUSION

An early postoperative ERMBT may be useful in predicting the development of cyclosporine and tacrolimus nephrotoxicity, severe graft dysfunction, or even graft loss in liver transplant recipients when calcineurin inhibitors are administered according to protocols. Whether ERMBT results may be used to individualize dosage of calcineurin inhibitors needs to be explored.

MEGX disposition in critically-ill trauma patients: subsequent assessments during the first week following trauma

The objective of this study was to evaluate MEGX disposition as a surrogate marker in assessing the influence that injury may exert on liver function during the first week after the traumatic event in young vs. elderly patients. The MEGX exposure over time was assessed at 0.25, 0.5, 1, 2, 4 and 6 h after the intravenous administration of a 1 mg/kg lidocaine test dose in 12 young and 7 elderly trauma patients on days 1, 4 and 7 after a severe injury (Apache II score > 10). MEGX plasma concentration-time profiles were consistently different on day 1 in the elderly vs. young, consistent with a statistically significant lower rate of both lidocaine clearance and MEGX formation, and with a considerably longer MEGX elimination in the elderly than in the young. This suggests an impairment of liver blood flow as a result of splanchnic vasoconstriction occurring mainly in elderly trauma patients. A significant improvement in MEGX disposition occurred on days 4 and 7 vs. the day of trauma in most elderly, whereas minor changes were observed in the young. Multiple factors may account for these major changes in the elderly: the more severe status, the major sensitivity to the pathophysiologic changes induced by trauma, and also at least partially the ageing processes. Although referring to a limited number of observations, our findings on MEGX disposition suggest that liver function may be affected by the severity of injury, even if the influence of age should not be underestimated in these patients.

Neuromuscular paralysis as a pharmacodynamic probe to assess organ function during liver transplantation

Potential for assessing liver function during liver transplantation surgery by monitoring muscle paralysis from nondepolarizing neuromuscular blockers that are hepatically cleared is critically assessed. Rocuronium is strongly favored as a promising pharmacodynamic probe for predicting allograft liver function because it is predominantly eliminated via the liver and its putative metabolites are not active. Prolongation of recovery from rocuronium paralysis is closely correlated with allograft liver function postoperatively. Vecuronium, pancuronium, and perhaps pipecuronium may also prove to be useful probes, but the two former blockers have active metabolites. Further prospective studies are necessary with more precise measurement of neuromuscular function to confirm the predictive value of this method. Alterations in neuromuscular blocker plasma concentrations that are correlated with changes in liver function and either the dose required or the intensity or duration of paralysis needs to be demonstrated for this technique to be clinically useful.