Cerebral blood flow and oxygenation in liver transplantation for acute or chronic hepatic disease without venovenous bypass

Comprehensive characterization of metabolic consumption and production by the human brain

Metabolism is vital for brain function. However, a systematic investigation to understand the metabolic exchange between the human brain and circulatory system has been lacking. Here, we compared metabolomes and lipidomes of blood samples from the cerebral venous sinus and femoral artery to profile the brain's uptake and release of metabolites and lipids (1,365 metabolites and 140 lipids). We observed a high net uptake of glucose, taurine, and hypoxanthine and identified glutamine and pyruvate as significantly released metabolites by the brain. Triacylglycerols are the most prominent class of lipid consumed by the brain. The brain with cerebral venous sinus stenosis (CVSS) consumed more glucose and lactate and released more glucose metabolism byproducts than the brain with cerebral venous sinus thrombosis (CVST). Our data also showed age-related alterations in the uptake and release of metabolites. These results provide a comprehensive view of metabolic consumption and production processes within the human brain.

Evaluation of dynamic cerebrovascular autoregulation during liver transplantation

BACKGROUND

Cerebrovascular autoregulation in patients with acute and chronic liver failure is often impaired, yet an intact autoregulation is essential for the demand-driven supply of oxygenated blood to the brain. It is unclear, whether there is a connection between cerebrovascular autoregulation during liver transplantation (LTX) and the underlying disease, and if perioperative anesthesiologic consequences can result from this.

METHODS

In this prospective observational pilot study, data of twenty patients (35% female) undergoing LTX were analyzed. Cerebral blood velocity was measured using transcranial doppler sonography and was correlated with arterial blood pressure. The integrity of dynamic cerebrovascular autoregulation (dCA) was evaluated in the frequency domain through transfer function analysis (TFA). Standard clinical parameters were recorded. Mixed one-way ANOVA and generalized estimating equations were fitted to data involving repeated measurements on the same patient. For all other correlation analyses, Spearman's rank correlation coefficient (Spearman's-Rho) was used.

RESULTS

Indications of impaired dCA are seen in frequency domain during different phases of LTX. No correlation was found between various parameter of dCA and primary disease, delirium, laboratory values, length of ICU or hospital stay, mortality or surgical technique.

CONCLUSIONS

Although in most cases the dCA has been impaired during LTX, the heterogeneity of the underlying diseases seems to be too diverse to draw valid conclusions from this observational pilot study.

Implication of Hypotension in the Pathogenesis of Cognitive Impairment and Brain Injury in Chronic Liver Disease

The incidence of chronic liver disease is on the rise. One of the primary causes of hospital admissions for patients with cirrhosis is hepatic encephalopathy (HE), a debilitating neurological complication. HE is defined as a reversible syndrome, yet there is growing evidence stating that, under certain conditions, HE is associated with permanent neuronal injury and irreversibility. The pathophysiology of HE primarily implicates a strong role for hyperammonemia, but it is believed other pathogenic factors are involved. The fibrotic scarring of the liver during the progression of chronic liver disease (cirrhosis) consequently leads to increased hepatic resistance and circulatory anomalies characterized by portal hypertension, hyperdynamic circulatory state and systemic hypotension. The possible repercussions of these circulatory anomalies on brain perfusion, including impaired cerebral blood flow (CBF) autoregulation, could be implicated in the development of HE and/or permanent brain injury. Furthermore, hypotensive insults incurring during gastrointestinal bleed, infection, or liver transplantation may also trigger or exacerbate brain dysfunction and cell damage. This review will focus on the role of hypotension in the onset of HE as well as in the occurrence of neuronal cell loss in cirrhosis.

Pathogenic factors of cognitive dysfunction after liver transplantation: an observational study

OBJECTIVES

Neurocognitive complications significantly reduce long-term health-related quality of life in patients undergoing liver transplantation; however, few studies have focused on their perioperative cognitive status. The authors designed a prospective observational study to determine the incidence and risk factors of posttransplant cognitive dysfunction.

METHODS

This study included patients with end-stage liver disease who were on the liver transplantation waiting list. We performed an investigation with a neuropsychological battery before and 1 week after the successful transplant, analyzed the changes, and further explored the complicated perioperative factors that contribute to cognitive dysfunction.

RESULTS

A total of 132 patients completed all the investigations. Compared with healthy controls and preoperative cognitive performance, 54 patients experienced deterioration, 50 patients remained unchanged, and 28 patients showed rapid improvement. Logistic regression analysis showed that age [odds ratio (OR) = 1.15, 95% confidence interval (CI, 1.07-1.22), P  < 0.001], the model for end-stage liver disease (MELD) score [OR = 1.07, 95% CI (1.03-1.13), P  = 0.038], systemic circulation pressure [OR = 0.95, 95% CI (0.91-0.99), P  = 0.026] within the first 30 min after portal vein opening, and total bilirubin concentration [OR = 1.02, 95% CI (1.01-1.03), P  = 0.036] on the seventh day post-transplant were closely related to the deterioration of cognitive function.

CONCLUSION

The incidences of deterioration, maintenance, and improvement in cognitive function were 40.9%, 37.9%, and 21.2%, respectively. Increasing age, higher MELD score, lower perfusion pressure in the early stage of the new liver, and higher total bilirubin concentration postoperatively may be independent pathogenic factors.

Rupture Risk of Intracranial Aneurysm and Prediction of Hemorrhagic Stroke after Liver Transplant

Postoperative hemorrhagic stroke (HS) is a rare yet devastating complication after liver transplantation (LT). Unruptured intracranial aneurysm (UIA) may contribute to HS; however, related data are limited. We investigated UIA prevalence and aneurysmal subarachnoid hemorrhage (SAH) and HS incidence post-LT. We identified risk factors for 1-year HS and constructed a prediction model. This study included 3544 patients who underwent LT from January 2008 to February 2019. Primary outcomes were incidence of SAH, HS, and mortality within 1-year post-LT. Propensity score matching (PSM) analysis and Cox proportional hazard analysis were performed. The prevalence of UIAs was 4.63% (n = 164; 95% confidence interval (CI), 3.95–5.39%). The 1-year SAH incidence was 0.68% (95% CI, 0.02–3.79%) in patients with UIA. SAH and HS incidence and mortality were not different between those with and without UIA before and after PSM. Cirrhosis severity, thrombocytopenia, inflammation, and history of SAH were identified as risk factors for 1-year HS. UIA presence was not a risk factor for SAH, HS, or mortality in cirrhotic patients post-LT. Given the fatal impact of HS, a simple scoring system was constructed to predict 1-year HS risk. These results enable clinical risk stratification of LT recipients with UIA and help assess perioperative HS risk before LT.

Neurocritical care monitoring of encephalopathic children with acute liver failure: A systematic review

Research on non-invasive neuromonitoring specific to PALF is limited. This systematic review identifies and synthesis the existing literature on non-invasive approaches to monitoring for neurological sequelae in patients with PALF. A series of literature searches were performed to identify all publications pertaining to five different non-invasive neuromonitoring modalities, in line with PRISMA guidelines. Each modality was selected on the basis of its potential for direct or indirect measurement of cerebral perfusion; studies on electroencephalographic monitoring were therefore not sought. Data were recorded on study design, patient population, comparator groups, and outcomes. A preponderance of observational studies was observed, most with a small sample size. Few incorporated direct comparisons of different modalities; in particular, comparison to invasive intracranial pressure monitoring was largely lacking. The integration of current evidence is considered in the context of the clinically significant distinctions between pediatric and adult ALF, as well as the implications for planning of future investigations to best support the evidence-based clinical care of these patients.

Ventilatory strategy during liver transplantation: implications for near-infrared spectroscopy-determined frontal lobe oxygenation

BACKGROUND

As measured by near infrared spectroscopy (NIRS), cerebral oxygenation (ScO2) may be reduced by hyperventilation in the anhepatic phase of liver transplantation surgery (LTx). Conversely, the brain may be subjected to hyperperfusion during reperfusion of the grafted liver. We investigated the relationship between ScO2 and end-tidal CO2 tension (EtCO2) during the various phases of LTx.

METHODS

In this retrospective study, 49 patients undergoing LTx were studied. Forehead ScO2, EtCO2, minute ventilation (VE), and hemodynamic variables were recorded from the beginning of surgery through to the anhepatic and reperfusion phases during LTx.

RESULTS

In the anhepatic phase, ScO2 was reduced by 4.3% (95% confidence interval: 2.5-6.0%; P < 0.0001), EtCO2 by 0.3 kPa (0.2-0.4 kPa; P < 0.0001), and VE by 0.4 L/min (0.1-0.7 L/min; P = 0.0018). Conversely, during reperfusion of the donated liver, ScO2 increased by 5.5% (3.8-7.3%), EtCO2 by 0.7 kPa (0.5-0.8 kPa), and VE by 0.6 L/min (0.3-0.9 L/min; all P < 0.0001). Changes in ScO2 were correlated to those in EtCO2 (Pearson r = 0.74; P < 0.0001).

CONCLUSION

During LTx, changes in ScO2 are closely correlated to those of EtCO2. Thus, this retrospective analysis suggests that attention to maintain a targeted EtCO2 would result in a more stable ScO2 during the operation.

New model of veno-venous bypass for management of anhepatic phase in experimental study on dogs

Blood is shunted from the inferior vena cava and portal vein to the superior vena caval system to prevent congestion in the lower parts of the body during the anhepatic phase (AP) of liver transplantation. It leads to overload in the superior vena caval system retarding cranial outflow due to a nonphysiological blood redistribution. To overcome this problem, we developed a new bypass in dogs: blood is shunted from the inferior (caudal) vena cava and portal vein to the suprahepatic inferior (caudal) vena cava. This model was compared with traditional one with or without a pump. Blood pressure and flow parameters were estimated during 3 hours of AP in four groups of four dogs each. The current study showed that a nontraditional scheme of venous bypass reduced circulatory complications during AP, especially in the cranial vena caval system, although a low rate of congestion remains in the caudal vena cava and portal vein systems. Whereas the same scheme using a pump effectively prevented congestion in all of the systems: cranial, caudal, and portal. We concluded that application of a nontraditional bypass scheme, providing venous blood return into suprahepatic part of caudal vena cava, can be considered to be a method of choice for experimental liver transplantation.

Lactate fuels the human brain during exercise

The human brain releases a small amount of lactate at rest, and even an increase in arterial blood lactate during anesthesia does not provoke a net cerebral lactate uptake. However, during cerebral activation associated with exercise involving a marked increase in plasma lactate, the brain takes up lactate in proportion to the arterial concentration. Cerebral lactate uptake, together with glucose uptake, is larger than the uptake accounted for by the concomitant O(2) uptake, as reflected by the decrease in cerebral metabolic ratio (CMR) [the cerebral molar uptake ratio O(2)/(glucose+(1/2) lactate)] from a resting value of 6 to <2. The CMR also decreases when plasma lactate is not increased, as during prolonged exercise, cerebral activation associated with mental activity, or exposure to a stressful situation. The CMR decrease is prevented with combined beta(1)- and beta(2)-adrenergic receptor blockade but not with beta(1)-adrenergic blockade alone. Also, CMR decreases in response to epinephrine, suggesting that a beta(2)-adrenergic receptor mechanism enhances glucose and perhaps lactate transport across the blood-brain barrier. The pattern of CMR decrease under various forms of brain activation suggests that lactate may partially replace glucose as a substrate for oxidation. Thus, the notion of the human brain as an obligatory glucose consumer is not without exceptions.

The need for venovenous bypass in liver transplantation

Since introduction of the conventional liver transplantation (CLTx) by Starzl, which was based on the resection of recipient inferior vena cava (IVC) along the liver, the procedure has undergone several refinements. Successful use of venovenous bypass (VVB) was first introduced by Shaw et al., although in recent decades there has been controversy regarding the routine use of VVB during CLTx. With development of piggyback liver transplantation (PLTx), the use of caval clamping and VVB is avoided, leading to fewer complications related to VVB. However, some authors still advocate VVB in PLTx. The great diversity among centers in their use of VVB during CLTx, or even along the PLTx technique, has led to confusion regarding the indication setting for VVB. For this reason, we present an overview of the use of VVB in CLTx, the target of patients for whom VVB could be beneficial, and the needs assessment of VVB for patients undergoing PLTx. Recent studies have shown that with the advancement of surgical skills, refinement of surgical techniques, and improvements in anesthesiology, there are only limited indications for doing CLTx with VVB routinely. PLTx with preservation of IVC can be performed in almost all primary transplants and in the majority of re-transplantations without the need for VVB. Nevertheless, in a few selective cases with severe intra-operative hemodynamic instability, or with a failed test of transient IVC occlusion, the application of VVB is still justifiable. These indications should be judged intra-operatively and the decision is based on each center's preference.

Headache and liver disease: is their relationship more apparent than real?

Headache is regarded by patients as a disturbing (or unpleasant) symptom. It can be produced by either organic diseases or functional head abnormalities. Twenty-five years ago headache was supposed to be a psychosomatic angiospastic algia. Certain unusual forms were thought to be caused by triggers like anger, cough, exertion, and sexual activity. Experimental research explored the role of circulating serotonin, prostaglandin, estrogen levels, and platelet abnormalities. As computed tomography, helical computed tomography, and scanning or magnetic resonance imaging evolved, new data became available. None of the newer reports have demonstrated liver involvement as a cause of headache. This minireview intends to cover the spectrum of brain alteration in liver disease. It describes some of the pathophysiological characteristics of hepatic encephalopathy and, also, the relationship among migraine, constipation, and liver disease.

Right lobe living donor liver transplantation with or without venovenous bypass

BACKGROUND

Venovenous bypass was considered necessary to maintain haemodynamic stability and avoid splanchnic and retroperitoneal congestion during the anhepatic phase of liver transplantation. It was essential for right lobe living donor liver transplantation (LDLT) in which the inferior vena cava needed to be cross-clamped to construct wide and short hepatic vein anastomoses. However, many complications related to venovenous bypass have been reported. This study aimed to determine whether venovenous bypass was necessary for right lobe LDLT.

METHODS

Between June 1996 and June 2001, 72 patients underwent right lobe LDLT. The outcomes for the first 29 patients who had venovenous bypass during the operation were compared with those of the remaining 43 patients who did not have venovenous bypass. In patients without bypass, blood pressure was maintained during the anhepatic phase by boluses of fluid infusion and vasopressors.

RESULTS

Compared with patients undergoing operation without venovenous bypass, patients who had venovenous bypass required significantly more blood, fresh frozen plasma and platelet infusion, and had a lower body temperature; their postoperative hepatic and renal function in the first week was worse than that in patients who did not have a bypass. The time to tracheal extubation was longer and the incidence of reintubation for ventilatory support was higher with venovenous bypass. Six of the 29 patients with venovenous bypass died in hospital, compared with two of the 43 patients without a bypass (P = 0.05). By multivariate analysis, the lowest body temperature during the transplant operation was the most significant factor that determined hospital death.

CONCLUSION

Venovenous bypass is not necessary and is probably harmful to patients undergoing right lobe LDLT, and should therefore be avoided.

S-100b and neuron-specific enolase in patients with fulminant hepatic failure

Patients with fulminant hepatic failure (FHF) frequently develop cerebral edema and intracranial hypertension. The aim of this study was to evaluate circulating S-100b and neuron-specific enolase (NSE) levels as markers of neurological outcome in patients with FHF. In a subgroup of patients, the cerebral flux of S-100b and NSE was measured. We included 35 patients with FHF, 6 patients with acute on chronic liver disease (AOCLD), 13 patients with cirrhosis of the liver without hepatic encephalopathy, and 8 healthy subjects. Blood samples were obtained from catheters placed in the radial artery and internal jugular bulb. The net cerebral flux of S-100b and NSE was measured, and the effect of short-term hyperventilation, as well as the effect of high-volume plasmapheresis, on circulating levels of these two biomarkers was determined. Blood levels of S-100b were greater in patients with FHF and AOCLD than patients with cirrhosis and healthy subjects (median, 0.39 microg/L; range, 0.02 to 10.31 microg/L; and 1.11 microg/L; range, 0.19 to 4.84 microg/L v 0.05 microg/L; range, 0.02 to 0.27 microg/L; and 0.09 microg/L; range, 0.02 to 0.15 microg/L, respectively; P <.05, ANOVA). Among patients with FHF, blood levels of NSE tended to be greater in patients who subsequently developed cerebral herniation than in survivors (median, 10.5 microg/L; range, 5.2 to 15.9 microg/L v 5.1 microg/L; range, 2.8 to 12 microg/L; P =.05). There was no net cerebral flux of S-100b or NSE. Short-term hyperventilation had no effect on any of these measures, whereas high-volume plasmapheresis reduced circulating S-100b levels from 0.45 microg/L (range, 0.19 to 10.31 microg/L) to 0.42 microg/L (range, 0.11 to 6.35 microg/L; P =.01). In conclusion, blood levels of S-100b were elevated in almost all patients with FHF and AOCLD, but were unrelated to survival. Conversely, NSE showed a clear tendency toward greater circulating levels in patients with FHF who subsequently developed cerebral herniation than in survivors. This finding encourages further evaluation of NSE as a marker of neurological outcome in FHF.