Autoregulation Assessment During Liver Transplantation

Study Overview
=================
Brief Summary
-----------------
Patients with liver failure undergoing liver transplantation often have clinical or sub-clinical encephalopathy that may lead to increased intracranial pressure. The latter may lead to abnormal regulation of blood flow to the brain (cerebral autoregulation) complicating patient management during and after general anesthesia. The current methods for monitoring for elevated intracranial pressure are invasive and, thus, limited to severe encephalopathy. In this study the investigators will evaluate the potential utility of monitoring cerebral blood flow (CBF) autoregulation non-invasively using near infra-red spectroscopy in patients undergoing liver transplantation.

Detailed Description
-----------------
Hepatic encephalopathy complicating chronic liver failure in patients undergoing liver transplantation increases the risk for adverse outcomes including mortality. Even mild hepatic encephalopathy may not be recognized clinically without specific testing but can be associated with impaired functional status and reduced quality of life before liver transplantation. The changes that can be seen in chronic liver failure, (cerebral edema and increased intracranial pressure) can adversely affect cerebral blood flow autoregulation that may predispose to brain injury during the multiple hemodynamic perturbations that occur during and after liver transplantation. Currently, invasive monitoring with an intracranial bolt is the only method to aggressively manage patients with elevated intracranial pressure from acute liver failure and hepatic encephalopathy. The placement of an intracranial pressure catheter in patient with liver failure is associated with a risk of brain hemorrhage due the presence of a coagulopathy. Further, the risk of this type of monitoring outweighs the benefits in the patients with milder or subclinical forms of hepatic encephalopathy. In this pilot study of 20 patients undergoing liver transplantation the investigators will evaluate the feasibility of non-invasive monitoring of CBF autoregulation and assess whether autoregulation is impaired in this group of patients. The investigators hypothesize that cerebral blood flow autoregulation is impaired in patients undergoing liver transplantation based on severity of liver disease. In this situation, improved patient monitoring would allow clinicians to maintain arterial blood pressure above an individual's lower limit of cerebral blood flow autoregulation that might prevent devastating brain injury during and after surgery. Cerebral blood flow autoregulation can be continuously monitored by evaluating the correlation coefficient between cerebral blood flow velocity measured with transcranial Doppler and arterial blood pressure. The investigators have developed a novel method of autoregulation monitoring using near infrared spectroscopy that allows continuous monitoring of autoregulation with the cerebral oximetry index and the hemoglobin volume index(, a moving linear correlation coefficient between cortical tissue oxygen saturation and hemoglobin level with arterial blood pressure, respectively. The latter approach is more practical and would allow widespread autoregulation monitoring in diverse clinical settings. A secondary hypothesis of this study is that near infrared spectroscopy-based monitoring of CBF autoregulation will provide an accurate assessment of the limits of autoregulation compared with the more clinically challenging transcranial Doppler methods . Specific Aims: To assess whether patients undergoing liver transplantation have impaired cerebral blood flow autoregulation. To evaluate whether non-invasive monitoring of cerebral blood flow autoregulation with cerebral oximetry index and hemoglobin volume index can identify the lower limit of autoregulation within 10 mmHg compared with that measured with transcranial Doppler.

Official Title
-----------------
Non-Invasive Assessment of Cerebral Blood Flow Autoregulation in Patients Undergoing Liver Transplantation

Conditions
-----------------
Liver Failure, Liver Transplantation, Encephalopathy

Intervention / Treatment
-----------------
* Other: Near infrared spectroscopy monitoring
* Other: Autoregulation monitoring


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: -Age > 18 years old and undergoing liver transplantation. Exclusion Criteria: Clinical instability as judged by the attending physicians whereby autoregulation monitoring may interfere with clinical care. Women of child bearing potential require a negative urine human chorionic gonadotropin (HCG) test to be enrolled.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Autoregulation monitoring<br>Patients will be grouped into Meld Score | Other: Near infrared spectroscopy monitoring<br>* This is an observational study without interventions<br>* Other names: Cerebral oximetry index and hemaglobin volume index;Other: Autoregulation monitoring<br>* There are no interventions in this observational study<br>* Other names: Cerebral oximetry;|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
liver failure, liver transplantation