Perioperative Use of Continuous Renal Replacement Therapy for Orthotopic Liver Transplantation

Role of the Lymphocyte Count-to-C-Reactive Protein Ratio in the Risk Stratification for High EASE Scores After Living Donor Liver Transplantation: A Retrospective Observational Cohort Study

Background: Early allograft failure (EAF) significantly contributes to mortality, necessitating re-transplantation following liver transplantation. The EAF simplified estimation (EASE) score has been recently developed to predict EAF. We aimed to assess the predictive capacity of high EASE scores for EAF and postoperative outcomes and to evaluate the association between the lymphocyte count-to-C-reactive protein ratio (LCR) and high EASE scores after living donor liver transplantation (LDLT). Methods: We retrospectively analyzed the data of 808 patients who underwent LDLT. After excluding 16 patients with incomplete laboratory data, the final cohort included 792 patients. Patients with EASE scores ≥-0.74 were categorized into the high EASE group. Multivariate logistic regression was used to examine the association between the LCR and high EASE scores. Results: High EASE scores demonstrated superior predictive accuracy for EAF development relative to that of the early allograft dysfunction (EAD) model (p = 0.018) and were more closely associated with overall mortality (p = 0.033). A preoperative LCR < 12.7 significantly increased the odds (odds ratio, 3.3; confidence interval, 1.997-5.493) of exhibiting high EASE scores post-LDLT, alongside preoperative hematocrit levels, operative duration, intraoperative continuous renal replacement therapy, administered calcium dose, mean heart rate, and donor age. Conclusions: The EASE score could offer enhanced utility for predicting EAF and overall mortality following LDLT relative to that of EAD. Identifying and managing risk factors, including low LCR values, for elevated EASE scores is essential for improving patient prognoses.

Expert consensus on perioperative management of liver transplantation in adults with acute-on-chronic liver failure

Acute-on-chronic liver failure (ACLF) is a syndrome in which acute liver failure with extrahepatic organ failure occurs on chronic liver disease. Recently, liver transplantation is the only effective treatment for ACLF. There is still room for discussion on the optimal surgery timing for ACLF, perioperative infection prevention and control, and maintenance of nutrition and organ function. The Transplantation Immunology Committee of Branch of Organ Transplantation Physician of Chinese Medical Doctor Association and Enhanced Recovery of Liver Transplantation Group of Enhanced Recovery after Surgery Committee of Chinese Research Hospital Association invited relevant experts to discuss the perioperative management of ACLF liver transplantation in areas including surgery timing, organ protection, nutritional support, infection prevention and control, rehabilitation exercises, regulation of the internal environment, etc. An expert consensus was developed as reference for clinicians.

Role of thrombocytopenia in risk stratification for acute kidney injury after living donor liver transplantation

The aim of our study was to investigate pre and intraoperative clinical factors, including platelet count, which could inform risk stratification of early acute kidney injury (AKI) after living donor liver transplantation (LDLT). Additionally, the impact of severe thrombocytopenia on AKI risk was assessed using a propensity score (PS)-matched analysis. In total, 591 adult patients who underwent LDLT between January 2009 and December 2018 at our hospital were retrospectively analyzed. Early postoperative AKI was determined based on the KDIGO criteria, and 149 patients (25.2%) developed AKI immediately after surgery. In a multivariate analysis, a lower preoperative platelet count was significantly associated with early postoperative AKI, together with diabetes mellitus, lower hourly urine output, and longer graft ischemic time; furthermore, a decrease in platelet count was correlated with AKI severity. After adjusting for the PS, the probability of AKI was significantly (1.9-fold) higher in patients with severe thrombocytopenia than in those without severe thrombocytopenia. Patients with thrombocytopenia showed a higher postoperative incidence of AKI and a higher requirement for dialysis than those without thrombocytopenia. The platelet count can easily be obtained via regular blood analysis of patients scheduled for LDLT and can be used to identify patients at risk for AKI.

Risk stratification for early bacteremia after living donor liver transplantation: a retrospective observational cohort study

BACKGROUND

This study investigated perioperative clinical risk factors for early post-transplant bacteremia in patients undergoing living donor liver transplantation (LDLT). Additionally, postoperative outcomes were compared between patients with and without early post-transplant bacteremia.

METHODS

Clinical data of 610 adult patients who underwent elective LDLT between January 2009 and December 2018 at Seoul St. Mary's Hospital were retrospectively collected. The exclusion criteria included overt signs of infection within 1 month before surgery. A total of 596 adult patients were enrolled in this study. Based on the occurrence of a systemic bacterial infection after surgery, patients were classified into non-infected and infected groups.

RESULTS

The incidence of bacteremia at 1 month after LDLT was 9.7% (57 patients) and Enterococcus faecium (31.6%) was the most commonly cultured bacterium in the blood samples. Univariate analysis showed that preoperative psoas muscle index (PMI), model for end-stage disease score, utility of continuous renal replacement therapy (CRRT), ascites, C-reactive protein to albumin ratio, neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio, and sodium level, as well as intraoperative post-reperfusion syndrome, mean central venous pressure, requirement for packed red blood cells and fresh frozen plasma, hourly fluid infusion and urine output, and short-term postoperative early allograft dysfunction (EAD) were associated with the risk of early post-transplant bacteremia. Multivariate analysis revealed that PMI, the CRRT requirement, the NLR, and EAD were independently associated with the risk of early post-transplant bacteremia (area under the curve: 0.707; 95% confidence interval: 0.667-0.745; p < 0.001). The overall survival rate was better in the non-infected patient group. Among patients with bacteremia, anti-bacterial treatment was unable to resolve infection in 34 patients, resulting in an increased risk of patient mortality. Among the factors included in the model, EAD was significantly correlated with non-resolving infection.

CONCLUSIONS

We propose a prognostic model to identify patients at high risk for a bloodstream bacterial infection; furthermore, our findings support the notion that skeletal muscle depletion, CRRT requirement, systemic inflammatory response, and delayed liver graft function are associated with a pathogenic vulnerability in cirrhotic patients who undergo LDLT.

2019 Clinical Update in Liver Transplantation

Liver transplantation continues be the standard for treatment of end-stage liver disease, and even with recent advances in organ preservation, the anesthetic management continues to require understanding of multiple organ systems beyond the liver. Multiple factors contribute to hemodynamic changes after reperfusion of the liver graft that anesthesiologists should be aware of before unclamping. Concomitant renal dysfunction in end-stage liver disease is not uncommon, and preparation for continuous renal replacement therapy may need to be considered in certain cases. Cardiac evaluation of liver transplantation patients with an emphasis on arrhythmias, including atrial fibrillation, can help prevent both intraoperative and postoperative complications detrimental to the patient and graft. Finally, combined liver and thoracic organ transplantations may be indicated for certain disease processes that affect multiple organs. These cases require an understanding of the surgical technique and acknowledgment that some goals of the procedures may be in direct opposition to each other.

Predictive utility of the C-reactive protein to albumin ratio in early allograft dysfunction in living donor liver transplantation: A retrospective observational cohort study

BACKGROUND

This study was performed to determine the association between the ratio of C-reactive protein to albumin (CRP/ALB) and the risk of early allograft dysfunction (EAD) in patients undergoing living donor liver transplantation (LDLT).

PATIENTS AND METHODS

A total of 588 adult patients undergoing LDLT were retrospectively investigated, after 22 were excluded because of signs of overt infection or history of ALB infusion. The study population was classified into high and low CRP/ALB ratio groups according to EAD. All laboratory variables, including CRP and ALB, had been collected on the day before surgery. A percentage value for the CRP/ALB ratio (%) was calculated as CRP/ALB × 100.

RESULTS

After LDLT, 83 patients (14.1%) suffered EAD occurrence. A higher CRP/ALB ratio was independently associated with risk of EAD, Model for End-stage Liver Disease score, fresh frozen plasma transfusion, and donor age. Based on a cutoff CRP/ALB ratio (i.e., > 20%), the probability of EAD was significantly (2-fold) higher in the high versus low CRP/ALB group. The predictive utility of CRP/ALB ratio for EAD was greater than those of other inflammatory markers. In addition, patients with a high CRP/ALB ratio had poorer survival than those with a low CRP/ALB ratio during the follow-up period.

CONCLUSIONS

The easily calculated CRP/ALB ratio may allow estimation of the risk of EAD after LDLT and can provide additional information that may facilitate the estimation of a patient's overall condition.

Analysis of pre- and intraoperative clinical for successful operating room extubation after living donor liver transplantation: a retrospective observational cohort study

BACKGROUND

Early extubation after liver transplantation is safe and accelerates patient recovery. Patients with end-stage liver disease undergo sarcopenic changes, and sarcopenia is associated with postoperative morbidity and mortality. We investigated the impact of core muscle mass on the feasibility of immediate extubation in the operating room (OR) after living donor liver transplantation (LDLT).

METHODS

A total of 295 male adult LDLT patients were retrospectively reviewed between January 2011 and December 2017. In total, 40 patients were excluded due to emergency surgery or severe encephalopathy. A total of 255 male LDLT patients were analyzed in this study. According to the OR extubation criteria, the study population was classified into immediate and conventional extubation groups (39.6 vs. 60.4%). Psoas muscle area was estimated using abdominal computed tomography and normalized by height squared (psoas muscle index [PMI]).

RESULTS

There were no significant differences in OR extubation rates among the five attending transplant anesthesiologists. The preoperative PMI correlated with respiratory performance. The preoperative PMI was higher in the immediate extubation group than in the conventional extubation group. Potentially significant perioperative factors in the univariate analysis were entered into a multivariate analysis, in which preoperative PMI and intraoperative factors (i.e., continuous renal replacement therapy, significant post-reperfusion syndrome, and fresh frozen plasma transfusion) were associated with OR extubation. The duration of ventilator support and length of intensive care unit stay were shorter in the immediate extubation group than in the conventional extubation group, and the incidence of pneumonia and early allograft dysfunction were also lower in the immediate extubation group.

CONCLUSIONS

Our study could improve the accuracy of predictions concerning immediate post-transplant extubation in the OR by introducing preoperative PMI into predictive models for patients who underwent elective LDLT.

Intraoperative management of liver transplant recipients having severe renal dysfunction: results of 42 cases

Purpose

Whereas continuous renal replacement therapy (CRRT) has been utilized during liver transplantation (LT), there was a lack of evidence to support this practice. We investigated the adverse events at the perioperative periods in recipients of LT who received preoperative CRRT without intraoperative CRRT.

Methods

We retrospectively reviewed medical records of adult patients (age ≥ 18 years) who received LT between December 2009 and May 2015. Perioperative data were collected from the recipients, who received preoperative CRRT until immediately before LT, because of refractory renal dysfunction.

Results

Of 706 recipients, 42 recipients received preoperative CRRT. The mean (standard deviation) Model for end-stage liver disease score were 49.6 (13.4). Twenty-six point two percent (26.2%) of recipients experienced the serum potassium > 4.5 mEq/L before reperfusion and treated with regular insulin. Thirty-eight point one percent (38.1%) of recipients were managed with sodium bicarbonate because of acidosis (base excess < −10 mEq/L throughout LT). All patients finished their operations without medically uncontrolled complications such as severe hyperkalemia (serum potassium > 5.5 mEq/L), refractory acidosis, or critical arrhythmias. Mortality was 19% at 30 day and 33.3% at 1 year.

Conclusion

Although intraoperative CRRT was not used in recipients with severe preoperative renal dysfunction, LT was safely performed. Our experience raises a question about the need for intraoperative CRRT.

Prevention of the Osmotic Demyelination Syndrome After Liver Transplantation: A Multidisciplinary Perspective

The osmotic demyelination syndrome (ODS) is a serious neurologic condition that occurs in the setting of rapid correction of hyponatremia. It presents with protean manifestations, from encephalopathy to the "locked-in" syndrome. ODS can complicate liver transplantation (LT), and its incidence may increase with the inclusion of serum sodium as a factor in the Mayo End-Stage Liver Disease score. A comprehensive understanding of risk factors for the development of ODS in the setting of LT, along with recommendations to mitigate the risk of ODS, are necessary. The literature to date on ODS in the setting of LT was reviewed. Major risk factors for the development of ODS include severe pretransplant hyponatremia (serum sodium [SNa] < 125 mEq/L), the magnitude of change in SNa pre- versus posttransplant, higher positive intraoperative fluid balance, and the presence of postoperative hemorrhagic complications. Strategies to reduce the risk of ODS include correcting hyponatremia pretransplant via fluid restriction and/or ensuring an appropriate rate of increase from the preoperative SNa via close attention to fluid and electrolyte management both during and after surgery. Multidisciplinary management involving transplant hepatology, nephrology, neurology, surgery, and anesthesiology/critical care is key to performing LT safely in patients with hyponatremia.

Kidney Injury in Liver Disease

Acute kidney injury (AKI) occurs frequently in patients with liver disease and increases morbidity and mortality. Hepatorenal syndrome is a common cause of AKI in patients with decompensated cirrhosis and is due to alterations in systemic and renal hemodynamics. Serum creatinine-based estimation of kidney function is a key component of the Model for End-stage Liver Disease score in liver transplant candidates. Continuous renal replacement therapy is used in critically ill patients with liver failure and AKI. Simultaneous liver-kidney transplantation (SLK) may be required in patients with liver failure and prolonged AKI. Identification of appropriate candidates for SLK remains controversial.

Anaesthesia and intensive care for simultaneous liver-kidney transplantation: A single-centre experience with 12 recipients

Background and Aims:

The perioperative management of patients presenting for simultaneous liver and kidney transplantation (SLKT) is a complex process. We analysed SLKTs performed in our institution to identify preoperative, intraoperative and post-operative challenges encountered in the management.

Methods:

We retrospectively studied the case records of 12 patients who underwent SLKT between 2009 and 2014 and analysed details of pre-operative evaluation and optimisation, intraoperative anaesthetic management and the implications of use of perioperative continuous renal replacement therapy (CRRT) and the post-operative course of these patients.

Results:

Of the total 12 cases, 4 were under 16 years of age. The indications for SLKT were primary hyperoxaluria (5), congenital hepatic fibrosis with polycystic kidney disease (2), ethanol-related end-stage liver disease (ESLD) with hepatorenal syndrome type 1 (1). Four patients had ESLD with end-stage renal disease due to other causes. Six recipients received live donor grafts and 6 patients received cadaveric grafts. Seven patients received intraoperative CRRT. Mean duration of surgery was 12.5 h. Cardiac output monitors used were trans-oesophageal echocardiogram (2), pulmonary artery catheter (1) and pulse contour cardiac output monitor (3). There was 1 sepsis-related mortality on 7^th post-operative day.

Conclusion:

A thorough pre-operative evaluation and optimisation, knowledge and anticipation of potential problems, and meticulous intraoperative fluid management guided by appropriate monitoring and use of CRRT when needed can help in achieving successful outcomes.

Complications and mortality after adult to adult living donor liver transplantation: A retrospective cohort study

BACKGROUND AND AIMS

Living donor liver transplantation (LDLT) is widely performed for patients to resolve the critical shortage of organs from cadavers. Despite rapid implementation of the procedure, both complications and mortality of LDLT are annoying problems. The aim of this study was to analyze complications and mortality of patients after adult to adult LDLT (A-ALDLT) in a single center.

METHODS

Between April 2003 and November 2013, 167 (A-ALDLT) recipients in National Liver Institute, Egypt were included. We retrospectively analyzed complications and mortality in them.

RESULTS

The overall incidence of complications was 86.2% (n = 144) and classified as biliary 43.7% (n = 73), vascular 21.6% (n = 36), Small for size syndrome (SFSS) 12.6% (n = 21), Gastrointestinal tract (GIT) 19.8% (n = 33), wound 12.6% (n = 21), chest 19.8% (n = 33), neurological 26.3% (n = 44), renal 21% (n = 35), intra abdominal collection 21.6% (n = 36), recurrent hepatitis C virus (HCV) 16.8% (n = 28), recurrent hepatocellular carcinoma (HCC) 2.4% (n = 4), acute rejection 19.2% (n = 32). 65 (45.1%) of 144 complicated patients died, while 10 (43.5%) of 23 non complicated died. The incidence of whole, in hospital and late mortalities were 44.9%, 28.7% and 16.2% respectively.

CONCLUSIONS

Mortality was higher among complicated cases where vascular complications and SFSS had significant effect on it so prevention and treatment of them is required for improving outcome.

Complications and mortality after adult to adult living donor liver transplantation: A retrospective cohort study

BACKGROUND AND AIMS

Living donor liver transplantation (LDLT) is widely performed for patients to resolve the critical shortage of organs from cadavers. Despite rapid implementation of the procedure, both complications and mortality of LDLT are annoying problems. The aim of this study was to analyze complications and mortality of patients after adult to adult LDLT (A-ALDLT) in a single center.

METHODS

Between April 2003 and November 2013, 167 (A-ALDLT) recipients in National Liver Institute, Egypt were included. We retrospectively analyzed complications and mortality in them.

RESULTS

The overall incidence of complications was 86.2% (n = 144) and classified as biliary 43.7% (n = 73), vascular 21.6% (n = 36), Small for size syndrome (SFSS) 12.6% (n = 21), Gastrointestinal tract (GIT) 19.8% (n = 33), wound 12.6% (n = 21), chest 19.8% (n = 33), neurological 26.3% (n = 44), renal 21% (n = 35), intra abdominal collection 21.6% (n = 36), recurrent hepatitis C virus (HCV) 16.8% (n = 28), recurrent hepatocellular carcinoma (HCC) 2.4% (n = 4), acute rejection 19.2% (n = 32). 65 (45.1%) of 144 complicated patients died, while 10 (43.5%) of 23 non complicated died. The incidence of whole, in hospital and late mortalities were 44.9%, 28.7% and 16.2% respectively.

CONCLUSIONS

Mortality was higher among complicated cases where vascular complications and SFSS had significant effect on it so prevention and treatment of them is required for improving outcome.

Outcome of Patients with Infective Endocarditis who were Treated with Extracorporeal Membrane Oxygenation and Continuous Renal Replacement Therapy

Infective endocarditis is a potentially life threatening condition. It is associated with high mortality and morbidity resulting mostly due to cardiorespiratory failure. Extracorporeal membrane oxygenation is a modality of treatment used to support hypoxic respiratory failure especially in patients who are already on mechanical ventilation. Continuous renal replacement therapy is added mainly for maintaining fluid and electrolyte balance. Here we report a case series of patients diagnosed with infective endocarditis who were treated with combined extracorporeal membrane oxygenation and continuous renal replacement therapy. Three patients in the age group 20-60 years were admitted with clinical features suggestive of infective endocarditis. During the course of hospital stay they developed cardiorespiratory failure requiring mechanical ventilation and extracorporeal membrane oxygenation support for refractory hypoxia. It was complicated by heart failure, renal failure and fluid overload which required initiation of continuous renal replacement therapy. All the three patients succumbed in spite of the aggressive treatment. In addition to the role played by each complication, delayed start of continuous renal replacement therapy might have also contributed to the high mortality. Early initiation of continuous renal replacement therapy for management of fluid overload needs to be considered in the management of these critically ill patients.

Liver transplantation in recipients receiving renal replacement therapy: outcomes analysis and the role of intraoperative hemodialysis

The Model for End-Stage Liver Disease (MELD) system has dramatically increased the number of recipients requiring pretransplant renal replacement therapy (RRT) prior to liver transplantation (LT). Factors affecting post-LT outcomes and the need for intraoperative RRT (IORRT) were analyzed in 500 consecutive recipients receiving pretransplant RRT, including comparisons among recipients not receiving IORRT (No-IORRT, n = 401), receiving planned IORRT (Pl-IORRT, n = 70), and receiving emergent, unplanned RRT after LT initiation (Em-IORRT, n = 29). Despite a median MELD of 39, overall 30-day, 1-, 3- and 5-year survivals were 93%, 75%, 68% and 65%, respectively. Em-IORRT recipients had significantly more intraoperative complications (arrhythmias, postreperfusion syndrome, coagulopathy) compared with both No-IORRT and Pl-IORRT and greater 30-day graft loss (28% vs. 10%, p = 0.004) and need for retransplantation (24% vs. 10%, p = 0.099) compared with No-IORRT. A risk score based on multivariate predictors of IORRT accurately identified recipients with chronic (sensitivity 84%, specificity 72%, concordance-statistic [c-statistic] 0.829) and acute (sensitivity 93%, specificity 61%, c-statistic 0.776) liver failure requiring IORRT. In this largest experience of LT in recipients receiving RRT, we report excellent survival and propose a practical model that accurately identifies recipients who may benefit from IORRT. For this select group, timely initiation of IORRT reduces intraoperative complications and improves posttransplant outcomes.

Renal support during liver transplantation: when to consider it?

Patients undergoing orthotopic liver transplantation constitute a difficult-to-treat population. They often have multiorgan dysfunction: acute kidney injury, severe water-electrolyte and acid-base imbalances, systemic inflammatory responses, thrombocytopenia, as well as abnormalities of coagulation and fibrinolysis. All of these disorders may be further exacerbated by the surgical procedure, which is lengthy and technically complex, requiring massive blood product and other fluid infusions with a high risk to develop severe lactic acidosis, hyperkalemia, or cerebral edema. These considerations provide a rationale to institute intraoperative renal replacement therapy (ioRRT), at least for the most critically ill, namely, patients with kidney dysfunction, or those in whom one anticipates intraoperative clinical and technical problems. This article discusses the most common indications and strategies for ioRRT, examining their advantages and disadvantages as well as current experiences.

Acute liver failure

Untreated acute liver failure (ALF) has a poor outcome and so rapid diagnosis and management is vital if the patient is to survive. ALF has such profound and widespread physiological consequences that whenever possible, patients with ALF should be managed in an intensive care unit. Management is to support the physiology and treat the underlying cause. Advice should be sought from a centre capable of performing liver transplantation. Should recovery seem unlikely, liver transplantation is a viable treatment option in some cases.

Predictors of renal recovery in patients with pre-orthotopic liver transplant (OLT) renal dysfunction

BACKGROUND

Renal dysfunction occurs commonly in patients awaiting orthotopic liver transplantation (OLT) for end-stage liver disease. The use of simultaneous liver-kidney transplantation has increased in the MELD scoring era. As patients may recover renal function after OLT, identifying factors predictive of renal recovery is a critical issue, especially given the scarcity of available organs.

METHODS

Employing the UNOS database, we sought to identify donor- and patient-related predictors of renal recovery among 1720 patients with pre-OLT renal dysfunction and transplanted from 1989 to 2005. Recovery of renal function post-OLT was defined as a composite endpoint of serum creatinine (SCr) ≤1.5 mg/dL at discharge and survival ≥29 days. Pre-OLT renal dysfunction was defined as any of the following: SCr ≥2 mg/dL at any time while awaiting OLT or need for renal replacement therapy (RRT) at the time of registration and/or OLT.

RESULTS

Independent predictors of recovery of renal function post-OLT were absence of hepatic allograft dysfunction, transplantation during MELD era, recipient female sex, decreased donor age, decreased recipient ALT at time of OLT, decreased recipient body mass index at registration, use of anti-thymocyte globulin as induction therapy, and longer wait time from registration. Contrary to popular belief, a requirement for RRT, even for prolonged periods in excess of 8 weeks, was not an independent predictor of failure to recover renal function post-OLT.

CONCLUSION

These data indicate that the duration of renal dysfunction, even among those requiring RRT, is a poor way to discriminate reversible from irreversible renal dysfunction.

Anesthesia for Liver Transplantation

Orthotopic liver transplantation is the only definitive treatment for end-stage liver disease. More than 6000 procedures are performed in the United States annually with excellent survival rates. The shortage of donor organs leads to continued interest in techniques to enlarge the potential donor pool. Patients presenting for liver transplant suffer from important cardiovascular, respiratory, renal, neurological, and gastroenterological comorbidity. In the Western world, liver failure is increasingly caused by steatohepatitis, and transplant candidates are thus becoming older and more comorbid. The role of the transplant anesthesiologist is highly important in the preoperative assessment, intraoperative management, and postoperative care of these complex and sick patients. Appropriate investigation and management of comorbidities such as coronary artery disease and portopulmonary hypertension is controversial and differs between programs. The transplant procedure is a major surgery, and although massive transfusion is no longer commonplace, there is potential for significant hemodynamic instability, coagulopathy, and metabolic disturbance. Liver transplant surgery can be divided into the preanhepatic phase, the anhepatic phase, and the reperfusion phase, with important anesthetic considerations at each point.  An understanding of the surgical techniques used for vascular exclusion of the liver and the role of venovenous bypass is crucial for the anesthesiologist. Recent trends in perioperative care include the use of antifibrinolytic drugs and point-of-care coagulation tests, intraoperative renal replacement therapy, and “fast-track” extubation and postoperative care. Care of patients with fulminant hepatic failure or those receiving split-liver grafts requires special consideration.