Hemodynamic monitoring in liver transplantation 'the hemodynamic system'

PURPOSE OF REVIEW

The purpose of this article is to provide a comprehensive review of hemodynamic monitoring in liver transplantation.

RECENT FINDINGS

Radial arterial blood pressure monitoring underestimates the aortic root arterial blood pressure and causes excessive vasopressor and worse outcomes. Brachial and femoral artery monitoring is well tolerated and should be considered in critically ill patients expected to be on high dose pressors. The pulmonary artery catheter is the gold standard of hemodynamic monitoring and is still widely used in liver transplantation; however, it is a highly invasive monitor with potential for serious complications and most of its data can be obtained by other less invasive monitors. Rescue transesophageal echocardiography relies on few simple views and should be available as a standby to manage sudden hemodynamic instability. Risk of esophageal bleeding from transesophageal echocardiography in liver transplantation is the same as in other patient populations. The arterial pulse waveform analysis based cardiac output devices are minimally invasive and have the advantage of real-time beat to beat monitoring of cardiac output. No hemodynamic monitor can improve clinical outcomes unless integrated into a goal-directed hemodynamic therapy. The hemodynamic monitoring technique should be tailored to the patient's medical status, surgical technique, and the anesthesiologist's level of expertise.

SUMMARY

The current article provides a review of the current hemodynamic monitoring systems and their integration in goal-directed hemodynamic therapy.

Focused transoesophageal TOE (fTOE): A new accreditation pathway

The concept of a focused ultrasound study to identify sources of haemodynamic instability has revolutionized patient care. Point-of-care ultrasound (POCUS) using transthoracic scanning protocols, such as FUSIC Heart, has empowered non-cardiologists to rapidly identify and treat the major causes of haemodynamic instability. There are, however, circumstances when a transoesphageal, rather than transthoracic approach, may be preferrable. Due to the close anatomical proximity between the oesophagus, stomach and heart, a transoesphageal echocardiogram (TOE) can potentially overcome many of the limitations encountered in patients with poor transthoracic ultrasound windows. These are typically patients with severe obesity, chest wall injuries, inability to lie in the left lateral decubitus position and those receiving high levels of positive airway pressure. In 2022, to provide all acute care practitioners with the opportunity to acquire competency in focused TOE, the Intensive Care Society (ICS) and Association of Anaesthetists (AA) launched a new accreditation pathway, known as Focused Transoesophageal Echo (fTOE). The aim of fTOE is to provide the practitioner with the necessary information to identify the aetiology of haemodynamic instability. Focused TOE can be taught in a shorter period of time than comprehensive and teaching programmes are achievable with support from cardiothoracic anaesthetists, intensivists and cardiologists. Registration for fTOE accreditation requires registration via the ICS website. Learning material include theoretical modules, clinical cases and multiple-choice questions. Fifty fTOE examinations are required for the logbook, and these must cover a range of pathology, including ventricular dysfunction, pericardial effusion, tamponade, pleural effusion and low preload. The final practical assessment may be undertaken when the supervisors deem the candidate's knowledge and skills consistent with that required for independent practice. After the practitioner has been accredited in fTOE, they must maintain knowledge and competence through relevant continuing medical education. Accreditation in fTOE represents a joint venture between the ICS and AA and is endorsed by Association of Cardiothoracic Anaesthesia and Critical care (ACTACC). The process is led by TOE experts, and represents a valuable expansion in the armamentarium of acute care practitioners to assess haemodynamically unstable patients.

Using Transesophageal Echocardiography in Liver Transplantation with Veno-Venous Bypass Is a Tool with Many Applications: A Case Series from an Italian Transplant Center

BACKGROUND

Hemodynamic instability (HDI) is common during liver transplantation (LT); veno-venous bypass (VVB) is a tool used in selected cases to ensure hemodynamic stability and for surgical needs. Transesophageal echocardiography (TEE) allows the transplant team to identify the causes of HDI and to guide therapies. We present a case series of four patients showing the valuable role of TEE during LT in VVB.

METHODS

We report four explicative cases of TEE use in LT with VVB performed at IRCCS Azienda Ospedaliero-Universitaria di Bologna. Four transplants were performed between 2016 and 2022.

RESULTS

Many authors have highlighted the diagnostic value of TEE during LT in the case of HDI. However, its specific role during LT with VVB is poorly described. This paper illustrates multiple potential uses of TEE in LT with VVB: TEE as a guide for catheterization and optimal cannula positioning, TEE as a tool for intraoperative Patent Foramen Ovale management, TEE as help for anticoagulation therapy and finally, TEE as support when evaluating bypass efficiency and correcting hypovolemia.

CONCLUSION

TEE is a useful instrument during LT with VVB. However, further studies are needed to assess the suitable applications of TEE during LT in patients with HDI requiring VVB. TEE should be part of the anesthetist's cultural background.