Comparison of central and mixed venous saturation during liver transplantation in cirrhotic patients: a pilot study

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.

Central venous oxygenation: when physiology explains apparent discrepancies

Central venous oxygen saturation (ScvO₂) >70% or mixed venous oxygen saturation (SvO₂) >65% is recommended for both septic and non-septic patients. Although it is the task of experts to suggest clear and simple guidelines, there is a risk of reducing critical care to these simple recommendations. This article reviews the basic physiological and pathological features as well as the metrological issues that provide clear evidence that SvO₂ and ScvO₂ are adaptative variables with large inter-patient variability. This variability is exemplified in a modeled population of 1,000 standard ICU patients and in a real population of 100 patients including 15,860 measurements. In these populations, it can be seen how optimizing one to three of the four S(c)vO₂ components homogenized the patients and yields a clear dependency with the fourth one. This explains the discordant results observed in large studies where cardiac output was increased up to predetermined S(c)vO₂ thresholds following arterial oxygen hemoglobin saturation, total body oxygen consumption needs and hemoglobin optimization. Although a systematic S(c)vO₂ goal-oriented protocol can be statistically profitable before ICU admission, appropriate intensive care mandates determination of the best compromise between S(c)vO₂ and its four components, taking into account the specific constraints of each individual patient.

Comparison of mixed venous oxygen saturation after in vitro calibration of pulmonary artery catheter with that of pulmonary arterial blood in patients undergoing living donor liver transplantation

INTRODUCTION

Mixed venous saturation (SvO2) reflects the balance between oxygen delivery and consumption throughout the body. A multifunction pulmonary artery catheter (PAC) can monitor continuous SvO2 after in vitro calibration (CSvO2), obviating the need for in vivo calibration with pulmonary arterial blood. In critically ill patients CSvO2 has shown a good correlation with measured SvO2 of pulmonary arterial blood using co-oximetry (MSvO2). The aim of this study was to compare CSvO2 and MSvO2 in liver transplantation (OLT) recipients.

METHODS

We enrolled 44 OLT recipients for comparison with 24 coronary artery bypass graft (CABG) controls free of end-stage liver disease. After anesthetic induction, the PAC was inserted after in vitro calibration and CSvO2 and MSvO2 simultaneously measured. In OLT recipients, additional measurements of CSvO2 and MSvO2 were performed at anhepatic and postreperfusion phases. Pearson's correlation analysis was used to evaluate the correlation between the 2 measurements. A Bland-Altman analysis was used to determine precision of and bias between the 2 measurements. With ±3% regarded to be interchangeable.

RESULTS

Cardiac output and intrapulmonary shunt in CABG patients were lower than among OLT recipients. OLT recipients, showed a significant correlation between CSvO2 and MSvO2, but the coefficients were different during the three phases of OLT (r = 0.597, 0.753, and 0.756). In addition, bias values between the two measurements were 6.0%, 6.4%, and 2.9% for the preanhepatic, anhepatic, and postreperfusion phases, respectively, with 29.5%, 31.8%, and 50% of them being interchangeable. In contrast CABG patients showed bias in -0.17% with 75% of measurements interchangeable.

CONCLUSION

While in vitro calibration of the PAC can be used in CABG patients, MSvO2 is higher than CSvO2 in OLT recipients. Therefore, in vivo calibration with pulmonary arterial blood is necessary for accurate monitoring of SvO2 in OLT recipients.

Impact of a goal-directed therapy protocol on postoperative fluid balance in patients undergoing liver transplantation: a retrospective study

OBJECTIVE

Liver transplantation carries major risks during the perioperative period. Few studies focused on the hemodynamics of patients undergoing liver transplantation. The present study was aimed to evaluate the impact of the implementation of a protocol including goal-directed therapy in patients undergoing liver transplantation. Our first goal was to determine its impact on the fluid balance. Secondarily, we evaluated possible improvements in the patient outcomes.

STUDY DESIGN

A before and after study.

PATIENTS AND METHODS

Fifty patients undergoing liver transplantation were included during two successive six-month periods. During the first period, the management of the patients was left at the discretion of the senior physicians (control group, n=25). During the second period, the patients were treated according to a predetermined protocol including a specific hemodynamic monitoring (protocol group, n=25).

RESULTS

The fluid balance was negative in the protocol group and positive in the control group at 24h (-606mL vs. +3445mL, P<0.01) and 48h (-2315mL vs. +1170mL, P<0.01) after liver transplantation. The volume of the crystalloid administration was lower in the protocol group than in the control group (5000mL vs. 8000mL, P<0.01, and 1500mL vs. 6000mL, P<0.01, during surgery and 48h after liver transplantation, respectively). The duration of mechanical ventilation and postoperative ileus were significantly reduced in the protocol group, as compared with the control group, 20h vs. 94h (P<0.01) and 4days vs. 6days (P<0.01), respectively.

CONCLUSION

For patients undergoing liver transplantation, the implementation of a protocol aiming to optimize hemodynamics was associated with reduced fluid balance and decreased requirement for mechanical ventilation and postoperative ileus duration.

Use of the PiCCO system in critically ill patients with septic shock and acute respiratory distress syndrome: a study protocol for a randomized controlled trial

BACKGROUND

Hemodynamic monitoring is very important in critically ill patients with shock or acute respiratory distress syndrome(ARDS). The PiCCO (Pulse index Contour Continuous Cardiac Output, Pulsion Medical Systems, Germany) system has been developed and used in critical care settings for several years. However, its impact on clinical outcomes remains unknown.

METHODS/DESIGN

The study is a randomized controlled multi-center trial. A total of 708 patients with ARDS, septic shock or both will be included from January 2012 to January 2014. Subjects will be randomized to receive PiCCO monitoring or not. Our primary end point is 30-day mortality, and secondary outcome measures include ICU length of stay, days on mechanical ventilation, days of vasoactive agent support, ICU-free survival days during a 30-day period, mechanical-ventilation-free survival days during a 30-day period, and maximum SOFA score during the first 7 days.

DISCUSSION

We investigate whether the use of PiCCO monitoring will improve patient outcomes in critically ill patients with ARDS or septic shock. This will provide additional data on hemodynamic monitoring and help clinicians to make decisions on the use of PiCCO.

TRIAL REGISTRATION

http://www.clinicaltrials.gov NCT01526382.

Central venous saturation is not an alternative to mixed venous saturation during cardiopulmonary bypass in coronary artery surgery patients

BACKGROUND

To evaluate the correlation and agreement between central venous saturation (ScvO(2)) and mixed venous saturation (SvO(2)) during cardiopulmonary bypass.

METHODS

Twenty-two consecutive patients scheduled for coronary artery surgery were prospectively included. Paired measurements of ScvO(2) and SvO(2) were performed 5 minutes after aortic cross-clamping, after each cardioplegia dose and after de-clamping of the aortic cross-clamp. ScvO(2) and SvO(2) were measured, respectively, by a fibreoptic catheter in the superior vena cava and on blood samples from the venous return line of the extracorporeal circuit, using a blood gas analyser

RESULTS

Ninety-five paired measurements of venous saturation were obtained. Correlation between the measurements was associated with an r = 0.55. The mean bias was 2.2 [Limits of agreement: -13.6%, +18%]. Changes in oxygen saturation over time showed an r = 0.4 and a mean bias of 0.2 [Limits of agreement: -17.9%, +18.3%]. Multivariate analysis identified the oxygen consumption index as the only factor explaining this variability.

CONCLUSIONS

Although mean biases between the measurements were low, limits of agreement were too large to provide a clinically acceptable estimation of SvO(2) by ScvO(2) in these conditions. Variations in regional oxygen consumption seem to be the main factor worsening the relationship.