Equilibrium of acidifying and alkalinizing metabolic acid-base disorders in cirrhosis

No Good Deed: Acidosis in Chronic Kidney and Liver Disease

OBJECTIVE

Studies have shown that low or high serum bicarbonate levels (reflecting metabolic acidosis or alkalosis) are associated with increased all-cause mortality rates in moderate and advanced chronic kidney disease (CKD) cases. Correction of presumed acidosis using sodium bicarbonate, targeting serum levels around 22 mmol/L, has proven to be beneficial in delaying the progression of the disease and provided mortality benefit. A similar prognostic association may exist between uncorrected metabolic acidosis in chronic liver disease. Correcting it with sodium-containing salts may require more interventions due to increased sodium/fluid load. In patients with liver failure, a naturally alkalotic state, where sodium load is a concern, the impact of this intervention is unclear.

DESIGN

This study aims to generate proof of concept through a retrospective chart review in individuals with CKD-related metabolic acidosis and liver cirrhosis.

RESULT

Our analysis revealed a statistically significant association between the need for paracentesis and bicarbonate therapy. Our study has multiple drawbacks, including a retrospective chart review and limitation of data due to single-center patients.

CONCLUSION

We extrapolate that lowering bicarbonate targets in other clinical scenarios like liver failure, pregnancy, and cardiac failure may be prudent and will lead to a lower sodium load.

Acid-base abnormalities and liver dysfunction

In addition to the kidneys and lungs, the liver also plays an important role in the regulation of the Acid-Base Equilibrium (ABE). The involvement of the liver in the regulation of ABE is crucial because of its role in lactic acid metabolism, urea production and in protein homeostasis. The main acid-base imbalance that occurs in patients with liver cirrhosis is Respiratory Alkalosis (RAlk). Due to the fact that in these patients additional pathophysiological mechanisms that affect the ABE are present, other disorders may appear which compensate or enhance the primary disorder. Conventional ABE reading models fail to identify and assess the underlying disorders in patients with liver cirrhosis. This weakness of the classical models led to the creation of new physicochemical mathematical models that take into account all the known parameters that develop and affect the ABE. In addition to the RAlk, in patients with liver cirrhosis, metabolic alkalosis (due to hypoalbuminemia), hyponatremic metabolic acidosis, hyperchloremic metabolic acidosis, lactic acidosis and metabolic alkalosis due to urea metabolism are some of the pathophysiological mechanisms that affect the ABE.

Admission Serum Bicarbonate Predicts Adverse Clinical Outcomes in Hospitalized Cirrhotic Patients

A low serum bicarbonate (SB) level is predictive of adverse outcomes in kidney injury, infection, and aging. Because the liver plays an important role in acid-base homeostasis and lactic acid metabolism, we speculated that such a relationship would exist for patients with cirrhosis. To assess the prognostic value of admission SB on adverse hospital outcomes, clinical characteristics were extracted and analyzed from a large electronic health record system. Patients were categorized based on admission SB (mEq/L) into 7 groups based on the reference range (22-25) into mildly (18-21), moderately (14-17), and severely (<14) decreased groups and mildly (26-29), moderately (30-33), and severely (>30) increased groups, and the relationship of SB category with the frequency of complications (acute kidney injury/hepatorenal syndrome, portosystemic encephalopathy, gastrointestinal bleeding, ascites, and spontaneous bacterial peritonitis) and hospital metrics (length of stay [LOS], admission to an intensive care unit [ICU], and mortality) was assessed. A total of 2,693 patients were analyzed. Mean SB was 22.9 ± 4.5 mEq/L. SB was within the normal range (22-25 mEq/L) in 1,072 (39.8%) patients, and 955 patients (36%) had a low SB. As the SB category decreased, the incidence of complications progressively increased (p < 0.001). Increased MELD-Na score and low serum albumin also correlated with frequency of complications (p < 0.001). As the SB category decreased, LOS, ICU admission, and mortality progressively increased (p < 0.001). On multivariate analysis, the association of decreased SB with higher odds of complications, LOS, ICU admission, and mortality persisted. Conclusion. Low admission SB in patients with cirrhosis is associated with cirrhotic complications, longer LOS, increased ICU admissions, and increased hospital mortality.

Metabolic acidosis in critically ill patients with cirrhosis: Epidemiology and short-term mortality risk factors

BACKGROUND/AIMS

Metabolic acidosis is a common complication in patients with cirrhosis at the intensive care units (ICUs) and associated with increased mortality. The aim of our research was to explore the epidemiology and risk factors of metabolic acidosis in critically ill patients with cirrhosis.

MATERIALS AND METHODS

A total of 975 patients with cirrhosis were selected into our study, and all participants were followed up for at least 28 days. Cox regression model and machine-learning algorithm were used to identify the importance of different risk factors, respectively. Finally, an improved prognostic model as Model for End-stage Liver Disease and metabolic acidosis (MELD-MA) was developed.

RESULTS

Among the 975 patients with liver cirrhosis, 506 had metabolic acidosis, including 257 patients who had decompensated metabolic acidosis at ICU admission. The 28-day mortality was 41% (206/506) in patients with metabolic acidosis. Bilirubin (hazard ratio (HR): 1.023, 95% confidence interval (CI): 1.011-1.036), international normalized ratio (HR: 1.527, 95% CI: 1.332-1.750), pH (HR: 0.173, 95% CI: 0.047-0.640), BE-Lac (HR: 0.907, 95% CI: 0.868-0.948), and BE-Na (HR: 0.923, 95% CI: 0.859-0.991) were considered as independent prognostic parameters for 28-day mortality. MELD-NA had significantly higher discrimination (area under the receiver operating characteristic curve 0.79) than MELD and Child-Pugh score.

CONCLUSION

Critically ill patients with cirrhosis have a high mortality rate and poor prognosis because of the high prevalence of metabolic acidosis. Lactic acidosis is the worst prognosis of all types of metabolic acidosis. MELD-MA performs well on the short-term mortality assessment in critically ill patients with cirrhosis and metabolic acidosis.

Pseudo-Renal Tubular Acidosis: Conditions Mimicking Renal Tubular Acidosis

Hyperchloremic metabolic acidosis, particularly renal tubular acidosis, can pose diagnostic challenges. The laboratory phenotype of a low total carbon dioxide content, normal anion gap, and hyperchloremia may be misconstrued as hypobicarbonatemia from renal tubular acidosis. Several disorders can mimic renal tubular acidosis, and these must be appropriately diagnosed to prevent inadvertent and inappropriate application of alkali therapy. Key physiologic principles and limitations in the assessment of renal acid handling that can pose diagnostic challenges are enumerated.

Acid-base status and its clinical implications in critically ill patients with cirrhosis, acute-on-chronic liver failure and without liver disease

Background

Acid–base disturbances are frequently observed in critically ill patients at the intensive care unit. To our knowledge, the acid–base profile of patients with acute-on-chronic liver failure (ACLF) has not been evaluated and compared to critically ill patients without acute or chronic liver disease.

Results

One hundred and seventy-eight critically ill patients with liver cirrhosis were compared to 178 matched controls in this post hoc analysis of prospectively collected data. Patients with and without liver cirrhosis showed hyperchloremic acidosis and coexisting hypoalbuminemic alkalosis. Cirrhotic patients, especially those with ACLF, showed a marked net metabolic acidosis owing to increased lactate and unmeasured anions. This metabolic acidosis was partly antagonized by associated respiratory alkalosis, yet with progression to ACLF resulted in acidemia, which was present in 62% of patients with ACLF grade III compared to 19% in cirrhosis patients without ACLF. Acidemia and metabolic acidosis were associated with 28-day mortality in cirrhosis. Patients with pH values < 7.1 showed a 100% mortality rate. Acidosis attributable to lactate and unmeasured anions was independently associated with mortality in liver cirrhosis.

Conclusions

Cirrhosis and especially ACLF are associated with metabolic acidosis and acidemia owing to lactate and unmeasured anions. Acidosis and acidemia, respectively, are associated with increased 28-day mortality in liver cirrhosis. Lactate and unmeasured anions are main contributors to metabolic imbalance in cirrhosis and ACLF.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0391-9) contains supplementary material, which is available to authorized users.

Acid-base disorders in liver disease

Alongside the kidneys and lungs, the liver has been recognised as an important regulator of acid-base homeostasis. While respiratory alkalosis is the most common acid-base disorder in chronic liver disease, various complex metabolic acid-base disorders may occur with liver dysfunction. While the standard variables of acid-base equilibrium, such as pH and overall base excess, often fail to unmask the underlying cause of acid-base disorders, the physical-chemical acid-base model provides a more in-depth pathophysiological assessment for clinical judgement of acid-base disorders, in patients with liver diseases. Patients with stable chronic liver disease have several offsetting acidifying and alkalinising metabolic acid-base disorders. Hypoalbuminaemic alkalosis is counteracted by hyperchloraemic and dilutional acidosis, resulting in a normal overall base excess. When patients with liver cirrhosis become critically ill (e.g., because of sepsis or bleeding), this fragile equilibrium often tilts towards metabolic acidosis, which is attributed to lactic acidosis and acidosis due to a rise in unmeasured anions. Interestingly, even though patients with acute liver failure show significantly elevated lactate levels, often, no overt acid-base disorder can be found because of the offsetting hypoalbuminaemic alkalosis. In conclusion, patients with liver diseases may have multiple co-existing metabolic acid-base abnormalities. Thus, knowledge of the pathophysiological and diagnostic concepts of acid-base disturbances in patients with liver disease is critical for therapeutic decision making.

Electrolyte and Acid-Base Disturbances in End-Stage Liver Disease: A Physiopathological Approach

Electrolyte and acid-base disturbances are frequent in patients with end-stage liver disease; the underlying physiopathological mechanisms are often complex and represent a diagnostic and therapeutic challenge to the physician. Usually, these disorders do not develop in compensated cirrhotic patients, but with the onset of the classic complications of cirrhosis such as ascites, renal failure, spontaneous bacterial peritonitis and variceal bleeding, multiple electrolyte, and acid-base disturbances emerge. Hyponatremia parallels ascites formation and is a well-known trigger of hepatic encephalopathy; its management in this particular population poses a risky challenge due to the high susceptibility of cirrhotic patients to osmotic demyelination. Hypokalemia is common in the setting of cirrhosis: multiple potassium wasting mechanisms both inherent to the disease and resulting from its management make these patients particularly susceptible to potassium depletion even in the setting of normokalemia. Acid-base disturbances range from classical respiratory alkalosis to high anion gap metabolic acidosis, almost comprising the full acid-base spectrum. Because most electrolyte and acid-base disturbances are managed in terms of their underlying trigger factors, a systematic physiopathological approach to their diagnosis and treatment is required.

Strong ion and weak acid analysis in severe preeclampsia: potential clinical significance

BACKGROUND

The influence of common disturbances seen in preeclampsia, such as changes in strong ions and weak acids (particularly albumin) on acid-base status, has not been fully elucidated. The aims of this study were to provide a comprehensive acid-base analysis in severe preeclampsia and to identify potential new biological predictors of disease severity.

METHODS

Fifty women with severe preeclampsia, 25 healthy non-pregnant- and 46 healthy pregnant controls (26-40 weeks' gestation), were enrolled in this prospective case-control study. Acid-base analysis was performed by applying the physicochemical approach of Stewart and Gilfix.

RESULTS

Mean [sd] base excess was similar in preeclamptic- and healthy pregnant women (-3.3 [2.3], and -2.8 [1.5] mEq/L respectively). In preeclampsia, there were greater offsetting contributions to the base excess, in the form of hyperchloraemia (BE(Cl) -2 [2.3] vs -0.4 [2.3] mEq/L, P<0.001) and hypoalbuminaemia (BE(Alb) 3.6 [1] vs 2.1 [0.8] mEq/L, P<0.001). In preeclampsia, hypoalbuminaemic metabolic alkalosis was associated with a non-reassuring/abnormal fetal heart tracing (P<0.001). Quantitative analysis in healthy pregnancy revealed respiratory and hypoalbuminaemic alkalosis that was metabolically offset by acidosis, secondary to unmeasured anions and dilution.

CONCLUSIONS

While the overall base excess in severe preeclampsia is similar to that in healthy pregnancy, preeclampsia is associated with a greater imbalance offsetting hypoalbuminaemic alkalosis and hyperchloraemic acidosis. Rather than the absolute value of base excess, the magnitude of these opposing contributors may be a better indicator of the severity of this disease. Hypoalbuminaemic alkalosis may also be a predictor of fetal compromise.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov: NCT 02164370.

Acid-base disturbance in patients with cirrhosis: relation to hemodynamic dysfunction

PURPOSE

Acid-base disturbances were investigated in patients with cirrhosis in relation to hemodynamic derangement to analyze the hyperventilatory effects and the metabolic compensation.

METHODS

A total of 66 patients with cirrhosis and 44 controls were investigated during a hemodynamic study.

RESULTS

Hyperventilatory hypocapnia was present in all patients with cirrhosis and progressed from Child class A to C (P<0.01). Arterial pH increased significantly from class A to C (P<0.001) and was correlated inversely to the mean arterial blood pressure (r=-0.30, P<0.02), systemic vascular resistance (r=-0.25, P<0.05), indocyanine green clearance (r=-0.37, P<0.005), and serum sodium (r=-0.38, P<0.002). Metabolic compensation was shown by a reduced standard base excess in all patients (P<0.001). Standard base excess contained elements related to changes in serum albumin, water dilution, and effects of unidentified ions (all P<0.001). A significant hepatic component in the acid-base disturbances could not be identified.

CONCLUSION

Hypocapnic alkalosis is related to disease severity and hyperdynamic systemic circulation in patients with cirrhosis. The metabolic compensation includes alterations in serum albumin and water retention that may result in a delicate acid-base balance in these patients.

Physicochemical evaluation of acid-base disorders after liver transplantation and the contribution from administered fluids

OBJECTIVES

To analyze the mechanism of acid-base disorders in liver transplant recipients and to examine the relationship between these disorders and the fluids administered during surgery.

METHODS

This prospective study in a university-affiliated hospital intensive care unit (ICU) included 52 patients admitted to the ICU from December 2009 to January 2011. We examined the contributions of inorganic ion differences, lactate, unmeasured anions, phosphate, and albumin to metabolic acidosis. In addition to laboratory variables, we collected demographic and clinical data.

RESULTS

Metabolic acidosis (standard base excess ≤ -2.0 mmol/L) was identified in 37 (71.2%) patients during the immediate postoperative period. The inorganic ion difference was the main determinant of acidosis, accounting for -6.17 mEq/L of acidifying effect. The acidemia was attenuated mainly by the alkalinizing effect of albumin reduction, which contributed +6.03 mEq/L. There was an inverse proportional relationship between the quantity of saline solution used during surgery and the inorganic ion difference during the immediate postoperative period.

CONCLUSIONS

Hyperchloremia is the primary contributor to metabolic acidosis in liver transplant recipients. Possibly the use of chloride-rich solutions increases the incidence of this disorder.

Acid-base disturbances in critically ill patients with cirrhosis

BACKGROUND/AIMS

The equilibrium of offsetting metabolic acid-base disorders in stable cirrhosis might be lost during episodes of hepatic decompensation, haemorrhage or sepsis. The purpose of this study was to determine whether the acid-base state is destabilized in critically ill patients with cirrhosis and whether this is associated with mortality.

PATIENTS AND METHOD

One-hundred and eighty-one consecutive patients with cirrhosis were investigated in a prospective observational cohort study on admission to a medical intensive care unit (ICU) of a university hospital. Arterial acid-base state was assessed according to the Gilfix methodology. Clinical data, ICU mortality and hospital mortality were recorded.

MAIN RESULTS

Patients had net metabolic acidosis owing to unmeasured anions and owing to hyperchloraemic, dilutional and lactic acidosis. Lactic acidosis, acidemia and acute renal failure on ICU admission were associated with increased mortality. Lactate and pH discriminated survivors from non-survivors. The presence of lactic acidosis could not always be recognized by customary acid-base parameters.

CONCLUSION

The stable equilibrium of acid-base disorders is lost when patients with cirrhosis become critically ill. Lactic acidosis and acidaemia are associated with increased ICU mortality caused by severe underlying organ dysfunction.

Das Säure-Basen-Modell nach Stewart

In addition to paCO(2), Stewart's acid base model takes into account the influence of albumin, inorganic phosphate, electrolytes and lactate on acid-base equilibrium. It allows a comprehensive and quantitative analysis of acid-base disorders. Particularly simultaneous and mixed metabolic acid-base disorders, which are common in critically ill patients, can be assessed. Stewart's approach is therefore a valuable tool in addition to the customary acid-base approach based on bicarbonate or base excess. However, some chemical aspects of Stewart's approach remain controversial.

Modification of acid-base balance in cirrhotic patients undergoing liver resection for hepatocellular carcinoma

OBJECTIVE

To examine modifications of acid-base balance of cirrhotic patients undergoing hepatectomy for hepatocellular carcinoma (HCC).

SUMMARY BACKGROUND DATA

Acid-base disorders are frequently observed in cirrhotics; however, modifications during hepatectomy and their impact on prognosis have never been investigated.

METHODS

Two hundred and two hepatectomies for HCC on cirrhosis were reviewed. Arterial blood samples were collected immediately before and at the end of resection. Preresection and postresection acid-base parameters were compared and related to patient characteristics and postoperative course. The accuracy of acid-base parameters in predicting postoperative liver failure, defined as an impairment of liver function after surgery that led to patient death or required transplantation, was assessed using receiver operating characteristic analysis (ROC).

RESULTS

All patients showed a significant reduction in pH, bicarbonate, and base excess at the end of hepatectomy (P < 0.001 in all cases), worsened by intraoperative blood loss (P < 0.010) and preoperative Model for end-stage liver disease score > or =11 (P < 0.010). ROC curve analysis identifies patients with postresection bicarbonate <19.4 mmol/L at high risk for liver failure (50.0%) whereas levels >22.1 mmol/L did not lead to the event (0%; P < 0.001). Postoperative prolongation of prothrombin time and increases in bilirubin, creatinine, and morbidity were also more frequent in patients with lower postresection bicarbonate, resulting in a longer in-hospital stay.

CONCLUSION

In cirrhotic patients, a trend toward a relative acidosis can be expected during surgery and is worsened by the severity of the underlying liver disease and intraoperative blood loss. Postresection bicarbonate level lower than 19.4 mmol/L is an adverse prognostic factor.

Acid-Base and Potassium Disorders in Liver Disease

Acid-base and potassium disorders occur frequently in the setting of liver disease. As the liver's metabolic function worsens, particularly in the setting of renal dysfunction, hemodynamic compromise, and hepatic encephalopathy, acid-base disorders ensue. The most common acid-base disorder is respiratory alkalosis. Metabolic acidosis alone or in combination with respiratory alkalosis also is common. Acid-base disorders in patients with liver disease are complex. The urine anion gap may help to distinguish between chronic respiratory alkalosis and hyperchloremic metabolic acidosis when a blood gas is not available. A negative urine anion gap helps to rule out chronic respiratory alkalosis. In this disorder a positive urine anion gap is expected owing to suppressed urinary acidification. Distal renal tubular acidosis occurs in autoimmune liver disease such as primary biliary cirrhosis, but often is a functional defect from impaired distal sodium delivery. Potassium disorders are often the result of the therapies used to treat advanced liver disease.

The acidifying effect of lactate is neutralized by the alkalinizing effect of hypoalbuminemia in non-paracetamol-induced acute liver failure

BACKGROUND/AIMS

Hyperlactatemia with unexplained absence of metabolic acidosis is observed in acute liver failure. In chronic liver disease offsetting metabolic acid-base disorders could be revealed by means of physical-chemical acid-base analysis. The purpose of this study was to determine whether the acidifying effect of lactate is neutralized by the alkalinizing effect of hypoalbuminemia in acute liver failure.

METHODS

Serial arterial blood samples of 46 consecutive patients with non-paracetamol-induced acute liver failure were studied after admission to a medical ICU in a prospective investigation and compared to healthy controls. Acid-base state was assessed by quantitative physical-chemical analysis.

RESULTS

Lactate was increased and albumin was decreased in patients with acute liver failure compared to healthy controls resulting in normal net metabolic acid-base state. The alkalinizing effect of hypoalbuminemia was neutralized by the acidifying effect of elevated lactate. This observation was confirmed in serial analysis during 5 days after admission.

CONCLUSIONS

The acidifying effect of lactate is neutralized by the alkalinizing effect of hypoalbuminemia in non-paracetamol-induced acute liver failure. The absence of apparent metabolic acidosis in the presence of elevated lactate can be explained by means of the physical-chemical acid-base model.