Perioperative indocyanine green clearance is predictive for prolonged intensive care unit stay after coronary artery bypass grafting--an observational study

An efficient method for measuring plasma volume using indocyanine green dye

Plasma volume (PV) can be an important marker of health status and may affect the interpretation of plasma biomarkers, but is rarely measured due to the complexity and time required. Indocyanine green (ICG) is a water-soluble tricarbocyanine dye with a circulatory half-life of 2–3 min, allowing for quick clearance and repeated use. It is used extensively in medical diagnostic tests including ophthalmologic imaging, liver function, and cardiac output, particularly in critical care. ICG has been validated for measuring PV in humans, however previous work has provided minimal published details or has focused on a single aspect of the method. We aimed to develop a detailed, optimal protocol for the use of ICG to measure PV in women of reproductive age. We combined best practices from other studies and optimized the protocol for efficiency.

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This method reduces the time from blood collection to PV determination to ˜2 h and the amount of plasma required to estimate PV to 2.5 mL (1.5 mL before ICG injection and 1.0 mL post-injection).

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Participant inconvenience is reduced by inserting an intravenous (IV) catheter in only one arm, not both arms.

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Five post-injection plasma samples (2–5 min after ICG bolus) are enough to accurately develop the decay curve for plasma ICG concentration and estimate PV by extrapolation.

Assessment of liver perfusion and function by indocyanine green in the perioperative setting and in critically ill patients

Indocyanine green (ICG) is a water-soluble dye that is bound to plasma proteins when administered intravenously and nearly completely eliminated from the blood by the liver. ICG elimination depends on hepatic blood flow, hepatocellular function and biliary excretion. ICG elimination is considered as a useful dynamic test describing liver function and perfusion in the perioperative setting, i.e., in liver surgery and transplantation, as well as in critically ill patients. ICG plasma disappearance rate (ICG-PDR) which can be measured today by transcutaneous systems at the bedside is a valuable method for dynamic assessment of liver function and perfusion, and is regarded as a valuable prognostic tool in predicting survival of critically ill patients, presenting with sepsis, ARDS or acute liver failure.

Outcomes of abdominal surgery in patients with liver cirrhosis

Patients suffering from liver cirrhosis (LC) frequently require non-hepatic abdominal surgery, even before liver transplantation. LC is an important risk factor itself for surgery, due to the higher than average associated morbidity and mortality. This high surgical risk occurs because of the pathophysiology of liver disease itself and to the presence of contributing factors, such as coagulopathy, poor nutritional status, adaptive immune dysfunction, cirrhotic cardiomyopathy, and renal and pulmonary dysfunction, which all lead to poor outcomes. Careful evaluation of these factors and the degree of liver disease can help to reduce the development of complications both during and after abdominal surgery. In the emergency setting, with the presence of decompensated LC, alcoholic hepatitis, severe/advanced LC, and significant extrahepatic organ dysfunction conservative management is preferred. A multidisciplinary, individualized, and specialized approach can improve outcomes; preoperative optimization after risk stratification and careful management are mandatory before surgery. Laparoscopic techniques can also improve outcomes. We review the impact of LC on surgical outcome in non-hepatic abdominal surgeries required in this cirrhotic population before, during, and after surgery.

Influence of cirrhosis in cardiac surgery outcomes

Liver cirrhosis has evolved an important risk factor for cardiac surgery due to the higher morbidity and mortality that these patients may suffer compared with general cardiac surgery population. The presence of contributing factors for a poor outcome, such as coagulopathy, a poor nutritional status, an adaptive immune dysfunction, a degree of cirrhotic cardiomyopathy, and a degree of renal and pulmonary dysfunction, have to be taken into account for surgical evaluation when cardiac surgery is needed, together with the degree of liver disease and its primary complications. The associated pathophysiological characteristics that liver cirrhosis represents have a great influence in the development of complications during cardiac surgery and the postoperative course. Despite the population of cirrhotic patients who are referred for cardiac surgery is small and recommendations come from small series, since liver cirrhotic patients have increased their chance of survival in the last 20 years due to the advances in their medical care, which includes liver transplantation, they have been increasingly considered for cardiac surgery. Indeed, there is an expected rise of cirrhotic patients within the cardiac surgical population due to the increasing rates of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis, especially in western countries. In consequence, a more specific approach is needed in the assessment of care of these patients if we want to improve their management. In this article, we review the pathophysiology and outcome prediction of cirrhotic patients who underwent cardiac surgery.

Hepatopancreaticobiliary Values after Thoracoabdominal Aneurysm Repair

BACKGROUND

After thoracoabdominal aortic aneurysm (TAAA) repair, blood tests assessing hepatopancreaticobiliary (HPB) organs commonly have abnormal results. The clinical significance of such abnormalities is difficult to determine because the expected postoperative levels have not been characterized. Therefore, we sought to establish expected trends in HPB laboratory values after TAAA repair.

METHODS

This 5-year study comprised 155 patients undergoing elective Crawford extent II TAAA repair. In accordance with a prospective study protocol, all repairs involved left-sided heart bypass, selective visceral perfusion, and cold renal perfusion. Blood levels of aspartate transaminase (AST), alanine transaminase (ALT), γ-glutamyl transpeptidase (GGT), lactate dehydrogenase (LDH), total bilirubin, amylase, and lipase were measured before TAAA repair and for 7 days afterward. Ratios between postoperative and baseline levels were compared for each time point with 95% confidence intervals.

RESULTS

Temporal patterns for the laboratory values varied greatly. Amylase, lipase, and AST underwent significant early increases before decreasing to preoperative levels. LDH increased immediately and remained significantly elevated, whereas ALT increased more gradually. GGT remained near baseline through postoperative day 4, and then increased to more than twice baseline. Total bilirubin never differed significantly from baseline. After adjusted analysis, the ischemic time predicted the maximum AST, lipase, GGT, and LDH values.

CONCLUSIONS

Although most HPB laboratory values increase significantly after elective TAAA repair, the temporal trends for different values vary substantially. The ischemic time predicts the maximum AST, lipase, GGT, and LDH levels. These trends should be considered when laboratory values are assessed after TAAA repair.

Green light for liver function monitoring using indocyanine green? An overview of current clinical applications

The dye indocyanine green is familiar to anaesthetists, and has been studied for more than half a century for cardiovascular and hepatic function monitoring. It is still, however, not yet in routine clinical use in anaesthesia and critical care, at least in Europe. This review is intended to provide a critical analysis of the available evidence concerning the indications for clinical measurement of indocyanine green elimination as a diagnostic and prognostic tool in two areas: its role in peri-operative liver function monitoring during major hepatic resection and liver transplantation; and its role in critically ill patients on the intensive care unit, where it is used for prediction of mortality, and for assessment of the severity of acute liver failure or that of intra-abdominal hypertension. Although numerous studies have demonstrated that indocyanine green elimination measurements in these patient populations can provide diagnostic or prognostic information to the clinician, 'hard' evidence - i.e. high-quality prospective randomised controlled trials - is lacking, and therefore it is not yet time to give a green light for use of indocyanine green in routine clinical practice.

Indocyanine green clearance as an outcome prediction tool in cardiac surgery: a prospective study

PURPOSE

To evaluate the role of plasma disappearance rate of indocyanine green (PDR-ICG) as an outcome prediction tool in cardiac surgery.

PATIENTS AND METHODS

One hundred ninety patients undergoing coronary artery bypass grafting, valve surgery or combined procedures were enrolled. PDR-ICG measurements along with standard lab values were performed preoperative and on postoperative days 1, 2, and on discharge from the intensive care unit. Adverse outcomes were defined as prolonged length of stay in the intensive care unit and/or mortality. Two groups were defined according to length of stay in the intensive care unit (≤ 3 days vs >3 days).

RESULTS

PDR-ICG values differed significantly for all time points between the groups. In a multivariate model, in patients over 65 years with a EuroSCORE below 8.5, a preoperative PDR-ICG value below 12.85%/min was the strongest independent predictor for prolonged intensive care unit stay (>3 days). A preoperative PDR-ICG value below 8.2%/min was the strongest independent predictor for mortality in a multivariate analysis including age, cardiac function, and EuroSCORE.

CONCLUSIONS

In addition to the established scores, PDR-ICG may provide valuable information for the assessment of perioperative morbidity and mortality in cardiac surgery. Pre- and early postoperative measurements may help to identify patients at risk for developing perioperative complications.

How to assess liver function?

PURPOSE OF REVIEW

The liver comprises a multitude of parenchymal and nonparenchymal cells with diverse metabolic, hemodynamic and immune functions. Available monitoring options consist of 'static' laboratory parameters, quantitative tests of liver function based on clearance, elimination or metabolite formation and scores, most notably the 'model for end-stage liver disease'. This review aims at balancing conventional markers against 'dynamic' tests in the critically ill.

RECENT FINDINGS

There is emerging evidence that conventional laboratory markers, most notably bilirubin, and the composite model for end-stage liver disease are superior to assess cirrhosis and their acute decompensation, while dynamic tests provide information in the absence of preexisting liver disease. Bilirubin and plasma disappearance rate of indocyanine green reflecting static and dynamic indicators of excretory dysfunction prognosticate unfavorable outcome, both, in the absence and presence of chronic liver disease better than other functions or indicators of injury. Although dye excretion is superior to conventional static parameters in the critically ill, it still underestimates impaired canalicular transport, an increasingly recognized facet of excretory dysfunction.

SUMMARY

Progress has been made in the last year to weigh static and dynamic tests to monitor parenchymal liver functions, whereas biomarkers to assess nonparenchymal functions remain largely obscure.

Indocyanine green clearance after cardiac surgery: the impact of cardiopulmonary bypass

Plasma clearance of indocyanine green has recently been established as a tool to monitor hepatic function and perfusion non-invasively. Reduced indocyanine green clearance has been associated with adverse outcome in cardiac surgery patients, and cardiopulmonary bypass has been hypothesized to be one important triggering factor. We performed a prospective observational study comparing the influence of off-pump and on-pump coronary surgery on perioperative indocyanine green clearance. Twenty-five consecutive adult patients without known pre-existing hepatic diseases scheduled for off-pump coronary artery bypass grafting were evaluated for hepatic dysfunction pre- and postoperatively with serial measurements of indocyanine green plasma clearance, specific laboratory values and liver function scores. Twenty-five matched patients who underwent coronary artery bypass grafting surgery with cardiopulmonary bypass in the same period served as controls. Parameters of postoperative hepatic function, including measurements of indocyanine green plasma clearance and specific laboratory values and scores, did not differ significantly between patients undergoing off-pump coronary artery bypass grafting and patients undergoing coronary artery bypass grafting with extracorporeal circulation. In patients without pre-existing hepatic diseases, a significant influence of cardiopulmonary bypass on perioperative indocyanine green plasma clearance as well as on liver specific laboratory parameters and scores cannot be proven.