Metabolic acidosis in the intensive care unit

pH Quantification in Human Dermal Interstitial Fluid Using Ultra-Thin SOI Silicon Nanowire ISFETs and a High-Sensitivity Constant-Current Approach

In this paper, we propose a novel approach to utilize silicon nanowires as high-sensitivity pH sensors. Our approach works based on fixing the current bias of silicon nanowires Ion Sensitive Field Effect Transistors (ISFETs) and monitor the resulting drain voltage as the sensing signal. By fine tuning the injected current levels, we can optimize the sensing conditions according to different sensor requirements. This method proves to be highly suitable for real-time and continuous measurements of biomarkers in human biofluids. To validate our approach, we conducted experiments, with real human sera samples to simulate the composition of human interstitial fluid (ISF), using both the conventional top-gate approach and the optimized constant current method. We successfully demonstrated pH sensing within the physiopathological range of 6.5 to 8, achieving an exceptional level of accuracy in this complex matrix. Specifically, we obtained a maximum error as low as 0.92% (equivalent to 0.07 pH unit) using the constant-current method at the optimal current levels (1.71% for top-gate). Moreover, by utilizing different pools of human sera with varying total protein content, we demonstrated that the protein content among patients does not impact the sensors' performance in pH sensing. Furthermore, we tested real-human ISF samples collected from volunteers. The obtained accuracy in this scenario was also outstanding, with an error as low as 0.015 pH unit using the constant-current method and 0.178 pH unit in traditional top-gate configuration.

Diabetic ketoacidosis mimicking COVID‐19 in an adolescent

Diabetic ketoacidosis (DKA) may be associated with nonspecific symptoms such as dyspnea, tachycardia, anorexia, and vomiting that are similar to COVID‐19. We describe an adolescent who was referred to the emergency department with the above symptoms and died after being discharged, regardless of the differential diagnosis and laboratory findings.

“The Bitter Truth of Sugar”—Euglycemic Diabetic Ketoacidosis due to Sodium-glucose Cotransporter-2 Inhibitors: A Case Series

Diabetic ketoacidosis (DKA) is an acute and major complication of diabetes mellitus (DM), both type I and type II. Biochemically, DKA consists of a triad of blood sugar levels greater than 250 mg/dL, ketonemia of greater than 3 mmol/L and/or significant ketonuria, and a blood pH less than 7.3 with an increased anion gap. Currently, the sodium-glucose cotransporter-2 inhibitors (SGLT-2i) are widely used in management of type II diabetes. There have been several reports of an association between euglycemic diabetic ketoacidosis (EuDKA) and SGLT-2i agents. We present three different patients who were on SGLT-2i therapy who developed recurrent EuDKA postprocedure or sepsis. We believe that prolonged treatment (5–6 days) with intravenous (IV) insulin with glucose until resolution of glycosuria can be considered as an inexpensive marker of resolution of EuDKA. Moreover, the recommended duration for discontinuation of these drugs prior to elective procedures should be longer than 3 days.

How to cite this article: Shah M, Pathrose E, Bhagwat NM, Chandy D. “The Bitter Truth of Sugar”—Euglycemic Diabetic Ketoacidosis due to Sodium-glucose Cotransporter-2 Inhibitors: A Case Series. Indian J Crit Care Med 2022;26(1):123–126.

Iatrogenic Toxicities in the Intensive Care Unit

Drug-induced iatrogenic toxicities are common in critically ill patients and have been associated with increased morbidity and mortality. Early recognition and management of iatrogenic toxicities is essential; however, the diagnosis is usually complicated by the underlying critical illness, comorbidities, and administration of multiple medications. This article reviews several types of iatrogenic toxicities associated with medications that are commonly used in critically ill patients. The mechanism of the iatrogenic toxicities, clinical presentation, and diagnosis, as well as management are discussed.

Acid base disorders in patients with COVID-19

Purpose

Acid–base derangement has been poorly described in patients with coronavirus disease 2019 (COVID-19). Considering the high prevalence of pneumonia and kidneys injury in COVID-19, frequent acid–base alterations are expected in patients admitted with SARS-Cov-2 infection. The study aimed to assess the prevalence of acid–base disorders in symptomatic patients with a diagnosis of COVID-19.

Methods

The retrospective study enrolled COVID-19 patients hospitalized at the University Hospital of Modena from 4 March to 20 June 2020. Baseline arterial blood gas (ABG) analysis was collected in 211 patients. In subjects with multiple ABG analysis, we selected only the first measurement. A pH of less than 7.37 was categorized as acidemia and a pH of more than 7.43 was categorized as alkalemia.

Results

ABG analyses revealed a low arterial partial pressure of oxygen (PO₂, 70.2 ± 25.1 mmHg), oxygen saturation (SO₂, 92%) and a mild reduction of PO₂/FiO₂ ratio (231 ± 129). Acid–base alterations were found in 79.7% of the patient. Metabolic alkalosis (33.6%) was the main alteration followed by respiratory alkalosis (30.3%), combined alkalosis (9.4%), respiratory acidosis (3.3%), metabolic acidosis (2.8%) and other compensated acid–base disturbances (3.6%). All six patients with metabolic acidosis died at the end of the follow-up.

Conclusion

Variations of pH occurred in the majority (79.7%) of patients admitted with COVID-19. The patients experienced all the type of acid–base disorders, notably metabolic and respiratory alkalosis were the most common alterations in this group of patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-021-02855-1.

Sodium Bicarbonate in Different Critically Ill Conditions: From Physiology to Clinical Practice

Intravenous sodium bicarbonate is commonly used in several critically ill conditions for the management of acute acidemia independently of the etiology, and for the prevention of acute kidney injury, although this is still controversial from a physiologic point of view.

Isolated Starvation Ketoacidosis: A Rare Cause of Severe Metabolic Acidosis Presenting with a pH Less than 7

Anion gap metabolic acidosis (AGMA) occurs when an anion gap exists along with metabolic acidosis, most commonly due to diabetic ketoacidosis (DKA) and lactic acidosis (LA). Isolated starvation ketoacidosis (ISK) is one of the rare causes of AGMA; however, it usually presents with a mild disturbance in pH. We report a rare case of a 45-year-old female with previously diagnosed squamous cell cancer (SCC) of the larynx. She presented to the emergency department complaining of difficulty in breathing following laryngectomy and tracheostomy for SCC. Her laboratory results on admission were consistent for isolated starvation ketoacidosis and the patient responded quickly to the appropriate treatment.

High serum potassium level is associated with successful electrical cardioversion for new-onset atrial fibrillation in the intensive care unit: A retrospective observational study

Electrical cardioversion (ECV) is a potentially life-saving treatment for haemodynamically unstable new-onset atrial fibrillation (AF); however, its efficacy is unsatisfactory. We aimed to elucidate the factors associated with successful ECV and prognosis in patients with AF. This retrospective observational study was conducted in two mixed intensive care units (ICUs) in a university hospital. Patients with new-onset AF who received ECV in the ICU were enrolled. We defined an ECV session as consecutive shocks within 15 minutes. The success of ECV was evaluated five minutes after the session. We analysed the factors associated with successful ECV and ICU mortality. Eighty-five AF patients who received ECV were included. ECV was successful in 41 (48%) patients, and 11 patients (13%) maintained sinus rhythm until ICU discharge. A serum potassium level ≥3.8 mol/L was independently associated with successful ECV in multivariate analysis (odds ratio (OR), 3.13; 95% confidence interval (CI), 1.07-9.11; p = 0.04). Maintenance of sinus rhythm until ICU discharge was significantly associated with ICU survival (OR 9.35; 95% CI 1.02-85.78, p = 0.048). ECV was successful in 48% of patients with new-onset AF developed in the ICU. A serum potassium level ≥3.8 mol/L was independently associated with successful ECV, and sinus rhythm maintained until ICU discharge was independently associated with ICU survival. These results suggested that maintaining a high serum potassium level may be important when considering the effectiveness of ECV for AF in the ICU.

Euglycemic Diabetic Ketoacidosis in the ICU: 3 Case Reports and Review of Literature

Diabetic ketoacidosis (DKA) is an acute complication of diabetes mellitus, both type I and type II, as well as other types with diabetes such gestacional diabetes mellitus. It is characterized by blood glucose levels greater than 250 mg/dL and metabolic acidosis (pH < 7.3 and serum bicarbonate < 15 mEq/dL) with an increased anion gap and the presence of ketone bodies in the blood or urine. Within this pathology, there is a subgroup of pathologies which are characterized by being present with no signs of hyperglycemia, posing a diagnostic challenge due to the absence of the main sign of the pathology and the diversity of their pathophysiology. In this article, we will present 3 clinical cases with 3 different forms of clinical presentation: a case of DKA in pregnancy, a case of DKA associated with the use of sodium-glucose cotransporter 2 (SGLT-2) inhibitors, and a third case related to sepsis, together with a narrative review of the literature on the topic.

Early pH Change Predicts Intensive Care Unit Mortality

Aim of the Study:

Metabolic acidosis is associated with increased mortality in critically ill patients. We hypothesized that early correction of acidosis of presumed metabolic origin results in improved outcomes.

Patients and Methods:

We conducted a prospective, observational study from February 2015 to June 2016 in a 12 bed mixed intensive care unit (ICU) of a 1000 bed tertiary care hospital in the north of India. ICU patients aged above 18 years with an admission pH ≥7.0 to <7.35 of presumed metabolic origin were included. Arterial blood gas parameters including pH, PaO₂, PaCO₂, HCO₃⁻, Na⁺, K⁺, Cl⁻, anion gap (AG), base excess, and lactate at 0, 6, and 24 h along with other standard laboratory investigations were recorded. The primary outcome was to assess the impact of early pH changes on mortality at day 28 of ICU.

Results:

A total of 104 patients with 60.6% males and 91.3% medical patients were included in the study. Sepsis of lung origin (60.6%) was the predominant etiology. By day 28, 68 (65.4%) patients had died. Median age was 49.5 years, weight 61.7 kg, Sequential Organ Failure Assessment, and Acute Physiologic and Chronic Health Evaluation II scores were 16 and 12, respectively. Nonsurvivors had a higher vasopressor index (P < 0.01), lactate and central venous oxygen saturation (P < 0.05), and lower pH (P < 0.05). A pH correction/change of ≥1.16% during the first 24 h had the best receiver operating characteristic for predicting survival at day 28, with area under the curve (95% confidence interval, 0.72 [0.62–0.82], P < 0.05) compared to HCO₃^-, BE, lactate, and AG.

Conclusions:

Metabolic acidosis is associated with higher mortality in ICU. The rate of change in pH may better predict ICU mortality than other metabolic indices.

Practical approach to detection and management of acute kidney injury in critically ill patient

Background

Acute kidney injury (AKI) is a common complication in critically ill patients and is associated with high morbidity and mortality. This paper provides a critical review of the etiologies of AKI and a systematic approach toward its diagnosis and management with emphasis on fluid volume assessment and the use of urine biochemical profile and microscopy in identifying the nature and the site of kidney injury.

Materials and methods

The search of PubMed and selection of papers had employed observational designs or randomized control trials relevant to AKI.

Results

AKI is defined by the rate of rise of serum creatinine and a decline in urine output. The pathophysiology is diverse and requires a careful and systematic assessment of predisposing factors and localization of site of injury. The majority of AKIs are due to prerenal causes such as fluid volume deficit, sepsis, or renal as in acute tubular injury. The use of central venous and arterial blood pressure monitoring and inferior vena cava echocardiography complemented by urine analysis and microscopy allows assessment of fluid volume status and AKI etiology.

Conclusions

Timely intervention by avoidance of fluid volume deficit and nephrotoxic agents and blood pressure support can reduce the incidence of AKI in critically ill patients.

A comparison of traditional and quantitative analysis of acid-base imbalances in hypoalbuminemic dogs

OBJECTIVE

To compare the traditional (HH) and quantitative approaches used for the evaluation of the acid-base balance in hypoalbuminemic dogs.

DESIGN

Prospective observational study.

SETTING

ICU of a veterinary teaching hospital.

ANIMALS

One hundred and five client-owned dogs.

MEASUREMENTS AND MAIN RESULTS

Jugular venous blood samples were collected from each patient on admission to determine: total plasma protein (TP), albumin (Alb), blood urea nitrogen (BUN), glucose (Glu), hematocrit (HCT), Na(+) , Cl(-) , K(+) , phosphate (Pi ), pH, PvCO2, bicarbonate (HCO3 (-) ), anion gap (AG), adjusted anion gap for albumin (AGalb ) or phosphate (AGalb-phos ), standardized base excess (SBE), strong ion difference (SID), concentration of nonvolatile weak buffers (Atot ), and strong ion gap (SIG). Patients were divided in 2 groups according to the severity of the hypoalbuminemia: mild (Alb = 21-25 g/L) and severe (Alb ≤20 g/L). All parameters were compared among groups. Patients with severe hypoalbuminemia showed significant decrease in TP (P = 0.011), Atot (P = 0.050), and a significant increase in adjusted AG (P = 0.048) and the magnitude of SIG (P = 0.011) compared to animals with mild hypoalbuminemia. According to the HH approach, the most frequent imbalances were simple disorders (51.4%), primarily metabolic acidosis (84.7%) associated with a high AG acidosis. However, when using the quantitative method, 58.1% of patients had complex disorders, with SIG acidosis (74.3%) and Atot alkalosis (33.3%) as the most frequent acid-base imbalances. Agreement between methods only matched in 32 cases (kappa < 0.20).

CONCLUSIONS

The agreement between the HH and quantitative methods for interpretation of acid-base balance was poor and many imbalances detected using the quantitative approach were missed using the HH approach. Further studies are necessary to confirm the clinical utility of using the quantitative approach in the decision-making process of the severely ill hypoalbuminemic patients.

Septic ketoacidosis

Various unmeasured anions other than lactate appear in the blood of septic patients, including ketones. However, the occurrence of sepsis-induced ketoacidosis without diabetes mellitus has not been reported to date. We herein describe severe ketoacidosis in a patient with septic shock despite the absence of diabetes, alcohol and starvation. A 76-year-old woman presented with septic shock due to acute obstructive cholangitis. She exhibited ketoacidosis and a remarkably strong ion gap, except for ketones. Sepsis alone may lead to ketoacidosis in patients without diabetes under specific conditions. The accumulation of ketones and other strong anions can occur in cases involving a decreased metabolic function. There may be a pathological condition called septic ketoacidosis.

Adenosine, glutamate and pH: interactions and implications

Adenosine's role in the nervous system is multifaceted. As the core molecule of adenosine triphosphate (ATP), adenosine exists in equilibrium with the adenine nucleotide pool and contributes to cellular energy charge, a quantification of relative amounts of available ATP, ADP, AMP and adenosine. Beyond participating in overall energy balance and thus in maintaining cellular homeostasis, adenosine critically influences dynamic signaling in the nervous system. In particular, adenosine has an effect on and is affected by excitatory synaptic transmission. This report describes the ubiquitous nature of adenosine's influence, outlines specific scenarios of clinical import and highlights emerging knowledge about the regulation of adenosine.

Use of sodium-chloride difference and corrected anion gap as surrogates of Stewart variables in critically ill patients

Introduction

To investigate whether the difference between sodium and chloride ([Na⁺] – [Cl⁻]) and anion gap corrected for albumin and lactate (AG_corr) could be used as apparent strong ion difference (SID_app) and strong ion gap (SIG) surrogates (respectively) in critically ill patients.

Methods

A total of 341 patients were prospectively observed; 161 were allocated to the modeling group, and 180 to the validation group. Simple regression analysis was used to construct a mathematical model between SID_app and [Na⁺] – [Cl⁻] and between SIG and AG_corr in the modeling group. Area under the receiver operating characteristic (ROC) curve was also measured. The mathematical models were tested in the validation group.

Results

in the modeling group, SID_app and SIG were well predicted by [Na⁺] – [Cl⁻] and AG_corr (R² = 0.973 and 0.96, respectively). Accuracy values of [Na⁺] – [Cl⁻] for the identification of SID_app acidosis (<42.7 mEq/L) and alkalosis (>47.5 mEq/L) were 0.992 (95% confidence interval [CI], 0.963–1) and 0.998 (95%CI, 0.972–1), respectively. The accuracy of AG_corr in revealing SIG acidosis (>8 mEq/L) was 0.974 (95%CI: 0.936–0.993). These results were validated by showing excellent correlations and good agreements between predicted and measured SID_app and between predicted and measured SIG in the validation group (R² = 0.977; bias = 0±1.5 mEq/L and R² = 0.96; bias = −0.2±1.8 mEq/L, respectively).

Conclusions

SID_app and SIG can be substituted by [Na⁺] – [Cl⁻] and by AG_corr respectively in the diagnosis and management of acid-base disorders in critically ill patients.

Acute kidney injury and the critically ill patient

Acute kidney injury (AKI) is a serious complication for the critically ill patient. The term has been increasingly adopted over recent years as efforts have been made to capture and better define mild to severe renal dysfunction. Persistent AKI can lead to the subsequent development of renal failure recognized as an important determinant of morbidity and mortality in the critically ill patient. This article explores the clinical implications of AKI for the critically ill patient and how this can have a profound influence on the principal presenting disease and expected outcome.

Acid-base disorders in critically ill neonates

Objective:

To study acid–base imbalance in common pediatric diseases (such as sepsis, bronchopneumonia, diarrhea, birth-asphyxia etc.) in neonates.

Design and Setting:

An observational study was conducted in an emergency room of a tertiary teaching care hospital in Haryana, India.

Patients and Methods:

Fifty neonates (from first hour to one month) attending pediatric emergency services with various ailments. Blood gas analysis, electrolytes, plasma lactate, and plasma albumin were estimated in neonates.

Results:

Metabolic acidosis was the most common acid–base disorder. Hyperlactatemia was observed in more than half of such cases. Birth asphyxia was another common disorder with the highest mortality in neonates followed by bronchopneumonia and sepsis. Significant correlation between mortality and critical values of lactate was observed.

Conclusion:

Birth asphyxia with high-lactate levels in neonates constituted major alterations in acid–base disorders seen in an emergency room of a tertiary teaching care hospital. Plasma lactate concentration measurement provides an invaluable tool to assess type of metabolic acidosis in addition to predicting mortality in these neonates.

Acid-base disorders in ICU patients

Metabolic acid-base disorders are comnom clinical problems in ICU patients. Arterial blood gas analysis and anion gap (AG) are important laboratory data in approaching acid-base interpretation. When measuring the AG, several factors such as albumin have influence on unmeasured anions and unmeasured cations. If a patient has hypoalbuminemia, the AG should be adjusted according to the albumin level. High AG metabolic acidoses including lactic acidosis, ketoacidosis, and ingestion of toxic alcohols are common in ICU patients. The treatment target of lactic acidosis and ketoacidosis is not the acidosis, but the underlying condition causing acidosis. Gastric acid loss, diuretics, volume depletion, renal compensation for respiratory acidosis, hypokalemia, and mineralocorticoid excess are common causes of metaboic alkalosis. In chloride responsive metaboic alkalosis, volume and potassium repletion are mandatory.

Mismatch of arterial and central venous blood gas analysis during haemorrhage

BACKGROUND AND OBJECTIVE

Arterial base excess and lactate levels are key parameters in the assessment of critically ill patients. The use of venous blood gas analysis may be of clinical interest when no arterial blood is available initially.

METHODS

Twenty-four pigs underwent progressive normovolaemic haemodilution and subsequent progressive haemorrhage until the death of the animal. Base excess and lactate levels were determined from arterial and central venous blood after each step. In addition, base excess was calculated by the Van Slyke equation modified by Zander (BE(z)). Continuous variables were summarized as mean +/- SD and represent all measurements (n = 195).

RESULTS

Base excess according to National Committee for Clinical Laboratory Standards for arterial blood was 2.27 +/- 4.12 versus 2.48 +/- 4.33 mmol(-l) for central venous blood (P = 0.099) with a strong correlation (r(2) = 0.960, P < 0.001). Standard deviation of the differences between these parameters (SD-DIFBE) did not increase (P = 0.355) during haemorrhage as compared with haemodilution. Arterial lactate was 2.66 +/- 3.23 versus 2.71 +/- 2.80 mmol(-l) in central venous blood (P = 0.330) with a strong correlation (r(2) = 0.983, P < 0.001). SD-DIFLAC increased (P < 0.001) during haemorrhage. BE(z) for central venous blood was 2.22 +/- 4.62 mmol(-l) (P = 0.006 versus arterial base excess according to National Committee for Clinical Laboratory Standards) with strong correlation (r(2) = 0.942, P < 0.001). SD-DIFBE(z)/base excess increased (P < 0.024) during haemorrhage.

CONCLUSION

Central venous blood gas analysis is a good predictor for base excess and lactate in arterial blood in steady-state conditions. However, the variation between arterial and central venous lactate increases during haemorrhage. The modification of the Van Slyke equation by Zander did not improve the agreement between central venous and arterial base excess.

Renal and cardiorespiratory effects of treatment with lactated Ringer's solution or physiologic saline (0.9% NaCl) solution in cats with experimentally induced urethral obstruction

OBJECTIVE

To compare the renal and cardiorespiratory effects of IV treatment with lactated Ringer's solution (LRS) or physiologic saline (0.9% NaCl) solution (PSS) in severely decompensated cats with urethral obstruction (UO).

ANIMALS

14 cats (4 cats were used only to establish infusion rates).

PROCEDURES

An occluded urethral catheter was used to induce UO in each cat. After development of severe metabolic acidosis, hyperkalemia, and postrenal azotemia, the obstruction was relieved (0 hours); LRS or PSS (5 cats/group) was administered IV (gradually decreasing rate) beginning 15 minutes before and continuing for 48 hours after UO relief. Ten minutes before urethral catheter placement (baseline), at start of fluid therapy (SFT), and at intervals during fluid administration, various physical and clinicopathologic evaluations were performed.

RESULTS

Metabolic acidosis was detected in the PSS-treated group at SFT and 2 hours after relief of UO and in the LRS-treated group only at SFT The PSS-treated group had significantly lower blood pH and bicarbonate concentrations at 8 through 48 hours and lower base excess values at 2 through 48 hours, compared with the LRS-treated group. Hypocalcemia and hypernatremia were detected in the PSS-treated group at 2 and 12 hours, respectively. Absolute serum potassium and chloride concentrations did not differ significantly between groups at any time point.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment with LRS or PSS appeared to be safe and effective in cats with experimentally induced UO; however, LRS was more efficient in restoring the acid-base and electrolyte balance in severely decompensated cats with UO.

Is salt, vitamin, or endocrinopathy causing this encephalopathy? A review of endocrine and metabolic causes of altered level of consciousness

Altered level of consciousness describes the reason for 3% of critical emergency department (ED) visits. Approximately 85% will be found to have a metabolic or systemic cause. Early laboratory studies such as a bedside glucose test, serum electrolytes, or a urine dipstick test often direct the ED provider toward endocrine or metabolic causes. This article examines common endocrine and metabolic causes of altered mentation in the ED via sections dedicated to endocrine-, electrolyte-, metabolic acidosis-, and metabolism-related causes.

Metabolic acid-base disorders in the critical care unit

The recognition and management of acid-base disorders is a commonplace activity in the critical care unit, and the role of weak and strong acids in the genesis of metabolic acid-base disorders is reviewed. The clinical approach to patients with metabolic alkalosis and metabolic acidosis is discussed in this article.

Acid-base disturbances in the intensive care unit: current issues and the use of continuous renal replacement therapy as a customized treatment tool

Continuous renal replacement therapies (CRRT) are often used to manage complex acid-base problems in critically ill patients. These techniques allow a constant manipulation of the plasma composition. Several technical factors from CRRT influence the acid-base status; namely, the effluent rate, the operational characteristics of the technique, the content of the solutions and the metabolic rate of the buffer. This article reviews the common acid base disorders occurring in the intensive care unit, using both the anion gap and the strong ion gap approaches, and describes the influence of CRRT on acid-base physiology. The use of CRRT as a customized therapy for acid-base disorders is discussed, allowing an integration of both physiological and technical concepts.

Intermittent versus continuous renal replacement therapy: a matter of controversy

BACKGROUND

Acute Renal Failure (ARF) requiring some form of replacement therapy is a frequent complication in the critically ill patient. Despite potential therapeutic advantages the expectation of an improvement in patient outcomes using Continuous Renal Replacement Therapy (CRRT) compared to conventional Intermittent Haemodialysis (IHD) remains controversial.

AIMS AND METHOD

This article will review the literature on the issues surrounding the use of IHD versus CRRT in the management of the critically ill patient. Articles were selected according to level of evidence with priority given to meta-analyses and randomised controlled trials.

DISCUSSION

Several operational features of CRRT allow this technique to be tolerated more easily in critical illness than IHD. The gradual removal of fluid reduces the incidence of hypotension and the risk of volume overload. Decreased variability in the concentration of solutes enables greater azotemia control. However, CRRT is required to operate uninterrupted to achieve a treatment dose that is equivalent to a conventional IHD treatment schedule. In the absence of definitive evidence to validate superior patient survival and return of renal function there is disagreement as to the most appropriate form of Renal Replacement Therapy (RRT) for the critically ill patient. The introduction of 'hybrid' therapies offers a further alternative treatment strategy, which combine favourable aspects of IHD and CRRT.

CONCLUSION

The decision to use IHD or CRRT should be guided by the therapeutic needs of the patient rather than the operational differences between the two techniques. The resources and expertise available at the organisation are also important in determining the mode best able to manage the critically ill patient at any stage and may change according to the severity of illness. The emergence of hybrid therapies provides a compromise option which encompasses many of the features of both systems, but does not embrace all options of either approach.

Determinants of alcohol use and abuse: Impact of quantity and frequency patterns on liver disease

More than 70% of alcohol is consumed by 10% of the population in the United States. Implicit in this statistic is that tremendous variation in the pattern of drinking (quantity, frequency, and duration) exists among alcohol consumers. Individuals who are binge or chronic drinkers will have different health outcomes than social drinkers. Therefore, knowing the pattern of drinking will shed light on how severely individuals are alcohol-dependent and on the extent of liver damage. Thus, these parameters assume particular relevance for the treatment-providing physician. Genetic factors contribute substantially to differences in alcohol metabolism. Variations in the activities of the alcohol-metabolizing enzymes, cytosolic alcohol dehydrogenase and mitochondrial aldehyde dehydrogenase, in part determine blood alcohol concentration, thereby contributing to the predisposition to becoming alcohol-dependent and to susceptibility to alcohol-induced liver damage. Chronic alcohol consumption induces cytochrome P450 2E1, a microsomal enzyme that metabolizes alcohol at high concentrations and also metabolizes medications such as acetaminophen and protease inhibitors. Alcohol metabolism changes the redox state of the liver, which leads to alterations in hepatic lipid, carbohydrate, protein, lactate, and uric acid metabolism. The quantity and frequency of alcohol consumption severely impact the liver in the presence of comorbid conditions such as infection with hepatitis B or C and/or human immunodeficiency virus, type 2 diabetes, hemochromatosis, or obesity and thus have implications with respect to the extent of injury and response to medications.

CONCLUSION

Knowledge of the relationships between the quantity, frequency, and patterns of drinking and alcoholic liver disease is limited. A better understanding of these relationships will guide hepatologists in managing alcoholic liver disease.

Hyperchloremia is the dominant cause of metabolic acidosis in the postresuscitation phase of pediatric meningococcal sepsis

OBJECTIVE

Metabolic acidosis is common in septic shock, yet few data exist on its etiological temporal profile during resuscitation; this is partly due to limitations in bedside monitoring tools (base excess, anion gap). Accurate identification of the type of acidosis is vital, as many therapies used in resuscitation can themselves produce metabolic acidosis.

DESIGN

Retrospective, cohort study.

SETTING

Multidisciplinary pediatric intensive care unit with 20 beds.

PATIENTS

A total of 81 children with meningococcal septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Acid-base data were collected retrospectively on 81 children with meningococcal septic shock (mortality, 7.4%) for the 48 hrs after presentation to the hospital. Base excess was partitioned using abridged Stewart equations, thereby quantifying the three predominant influences on acid-base balance: sodium chloride, albumin, and unmeasured anions (including lactate). Metabolic acidosis was common at presentation (mean base excess, -9.7 mmol/L) and persisted for 48 hrs. However, the pathophysiology changed dramatically from one of unmeasured anions at admission (mean unmeasured anion base excess, -9.2 mmol/L) to predominant hyperchloremia by 8-12 hrs (mean sodium-chloride base excess, -10.0 mmol/L). Development of hyperchloremic acidosis was associated with the amount of chloride received during intravenous fluid resuscitation (r = .44), with the base excess changing, on average, by -0.4 mmol/L for each millimole per kilogram of chloride administered. Hyperchloremic acidosis resolved faster in patients who 1) manifested larger (more negative) sodium chloride-partitioned base excess, 2) maintained a greater urine output, and 3) received furosemide; and slower in those with high blood concentrations of unmeasured anions (all, p < .05).

CONCLUSIONS

Hyperchloremic acidosis is common and substantial after resuscitation for meningococcal septic shock. Recognition of this entity may prevent unnecessary and potentially harmful prolonged resuscitation.

Qu'apporte le modèle de Stewart à l'interprétation des troubles de l'équilibre acide–base?

OBJECTIVES

To explain the different approaches for interpreting acid-base disorders; to develop the Stewart model which offers some advantages for the pathophysiological understanding and the clinical interpretation of acid-base imbalances.

DATA SOURCE

Record of french and english references from Medline data base. The keywords were: acid-base balance, hyperchloremic acidosis, metabolic acidosis, strong ion difference, strong ion gap.

DATA EXTRACTION

Data were selected including prospective and retrospective studies, reviews, and case reports.

DATA SYNTHESIS

Acid-base disorders are commonly analysed by using the traditional Henderson-Hasselbalch approach which attributes the variations in plasma pH to the modifications in plasma bicarbonates or PaCO2. However, this approach seems to be inadequate because bicarbonates and PaCO2 are completely dependent. Moreover, it does not consider the role of weak acids such as albuminate, in the determination of plasma pH value. According to the Stewart concept, plasma pH results from the degree of plasma water dissociation which is determined by 3 independent variables: 1) strong ion difference (SID) which is the difference between all the strong plasma cations and anions; 2) quantity of plasma weak acids; 3) PaCO2. Thus, metabolic acid-base disorders are always induced by a variation in SID (decreased in acidosis) or in weak acids (increased in acidosis), whereas respiratory disorders remains the consequence of a change in PaCO2. These pathophysiological considerations are important to analyse complex acid-base imbalances in critically ill patients. For example, due to a decrease in weak acids, hypoalbuminemia increases SID which may counter-balance a decrease in pH and an elevated anion gap. Thus if using only traditional tools, hypoalbuminemia may mask a metabolic acidosis, because of a normal pH and a normal anion gap. In this case, the association of metabolic acidosis and alkalosis is only expressed by respectively a decreased SID and a decreased weak acids concentration. This concept allows to establish the relationship between hyperchloremic acidosis and infusion of solutes which contain large concentration of chloride such as NaCl 0.9%. Finally, the Stewart concept permits to understand that sodium bicarbonate as well as sodium lactate induces plasma alkalinization. In fact, sodium remains in plasma, whereas anion (lactate or bicarbonate) are metabolized leading to an increase in plasma SID.

CONCLUSION

Due to its simplicity, the traditional Henderson-Hasselbalch approach of acid-base disorders, remains commonly used. However, it gives an inadequate pathophysiological analysis which may conduct to a false diagnosis, especially with complex acid-base imbalances. Despite its apparent complexity, the Stewart concept permits to understand precisely the mechanisms of acid-base disorders. It has to become the most appropriate approach to analyse complex acid-base abnormalities.

Impact of chloride balance in acidosis control: The Stewart approach in hemodialysis critically ill patients

BACKGROUND

Metabolic acidosis is highly prevalent in critically ill patients with acute renal failure. Little is known about the mechanisms by which renal replacement therapy intervenes in such cases. The objective of this study is to analyze the role of hemodialysis in acidosis correction in intensive care unit patients, with an emphasis on chloride levels in plasma and dialysate.

METHODS

We studied 19 intermittent hemodialysis procedures in 17 acidotic patients. The patients were grouped by procedure type (conventional or sustained low-efficiency dialysis) and by predialysis plasma chloride level (higher or lower than the dialysate chloride concentration). Immediately before and after each procedure, blood samples were collected for biochemical analysis. The Stewart method was used to calculate the strong ion difference and strong ion gap.

RESULTS

The patients presented acidosis related to hyperchloremia, hyperphosphatemia, and high unmeasured anions. Hypoalbuminemia had an alkalinizing effect. Hemodialysis corrected acidosis mainly by reducing phosphate and unmeasured anions. In the group as a whole, chloride levels did not change after dialysis. However, when analyzed according to predialysis plasma chloride, the high-chloride group presented a reduction in plasma chloride, resulting in better base excess improvement (Delta standard base excess) than in the low-chloride group. Among the determinants of acid-base status, the only factors correlating with Delta SBE were Delta strong ion gap and Delta chloride.

CONCLUSION

The serum chloride/dialysate chloride relationship during hemodialysis has an important impact on acidosis control.

Unmeasured anions in metabolic acidosis: unravelling the mystery

In the critically ill, metabolic acidosis is a common observation and, in clinical practice, the cause of this derangement is often multi-factorial. Various measures are often employed to try and characterise the aetiology of metabolic acidosis, the most popular of which is the anion gap. The purpose of the anion gap can be perceived as a means by which the physician is alerted to the presence of unmeasured anions in plasma that contribute to the observed acidosis. In many cases, the causative ion may be easily identified, such as lactate, but often the causative ion(s) remain unidentified, even after exclusion of the 'classic' causes. We describe here the various attempts in the literature that have been made to address this observation and highlight recent studies that reveal potential sources of such hitherto unmeasured anions.

Differentiating the causes of metabolic acidosis in the poisoned patient

Numerous drugs and toxins may induce the development of a metabolic acidosis. The treating physician should be cognizant of the many compounds that can produce metabolic acidosis following an overdose or an accidental exposure, or with therapeutic use. Knowledge and comprehension of the substances associated with metabolic acidosis will facilitate the diagnosis and treatment of poisoned patients.

Lactic acidosis: from sour milk to septic shock

Lactic acidosis is frequently encountered in the intensive care unit. It occurs when there is an imbalance between production and clearance of lactate. Although lactic acidosis is often associated with a high anion gap and is generally defined as a lactate level >5 mmol/L and a serum pH <7.35, the presence of hypoalbuminemia may mask the anion gap and concomitant alkalosis may raise the pH. The causes of lactic acidosis are traditionally divided into impaired tissue oxygenation (Type A) and disorders in which tissue oxygenation is maintained (Type B). Lactate level is often used as a prognostic indicator and may be predictive of a favorable outcome if it normalizes within 48 hours. The routine measurement of serum lactate, however, should not determine therapeutic interventions. Unfortunately, treatment options remain limited and should be aimed at discontinuation of any offending drugs, treatment of the underlying pathology, and maintenance of organ perfusion. The mainstay of therapy of lactic acidosis remains prevention.

Metabolic acidosis: differentiating the causes in the poisoned patient

Metabolic acidosis may arise from several drugs and toxins through a variety of mechanisms. Differentiating the causes of metabolic acidosis in the poisoned patient is an indispensable skill in clinical practice. Comprehension of toxin-induced metabolic acidosis, combined with a thorough history, physical examination, appropriate use of laboratory tests, and a stepwise approach, should aid the clinician in determining the cause of metabolic acidosis in the poisoned patient. When confronted with such a patient, it is imperative that one administer appropriate antidotal therapy, when necessary, and provide the patient with exceptional supportive care.

Differential Diagnosis of Metabolic Acidosis

Metabolic acidosis is defined as an acidemia created by one of three mechanisms: increased production of acids, decreased excretion of acids, or loss of alkali. This article addresses the identification and correct diagnosis of metabolic acidosis by reviewing important historical factors, pathophysiological principles, clinical presentation,and laboratory findings accompanying common high and normal anion gap metabolic acidoses in emergency department patients.

Validation of a method to partition the base deficit in meningococcal sepsis: a retrospective study

Introduction

The base deficit is a useful tool for quantifying total acid–base derangement, but cannot differentiate between various aetiologies. The Stewart–Fencl equations for strong ions and albumin have recently been abbreviated; we hypothesised that the abbreviated equations could be applied to the base deficit, thus partitioning this parameter into three components (the residual being the contribution from unmeasured anions).

Methods

The two abbreviated equations were applied retrospectively to blood gas and chemistry results in 374 samples from a cohort of 60 children with meningococcal septic shock (mean pH 7.31, mean base deficit -7.4 meq/L). Partitioning required the simultaneous measurement of plasma sodium, chloride, albumin and blood gas analysis.

Results

After partitioning for the effect of chloride and albumin, the residual base deficit was closely associated with unmeasured anions derived from the full Stewart–Fencl equations (r² = 0.83, y = 1.99 – 0.87x, standard error of the estimate = 2.29 meq/L). Hypoalbuminaemia was a common finding; partitioning revealed that this produced a relatively consistent alkalinising effect on the base deficit (effect +2.9 ± 2.2 meq/L (mean ± SD)). The chloride effect was variable, producing both acidification and alkalinisation in approximately equal proportions (50% and 43%, respectively); furthermore the magnitude of this effect was substantial in some patients (SD ± 5.0 meq/L).

Conclusion

It is now possible to partition the base deficit at the bedside with enough accuracy to permit clinical use. This provides valuable information on the aetiology of acid–base disturbance when applied to a cohort of children with meningococcal sepsis.

Comparison of three strong ion models used for quantifying the acid-base status of human plasma with special emphasis on the plasma weak acids

Currently, three strong ion models exist for the determination of plasma pH. Mathematically, they vary in their treatment of weak acids, and this study was designed to determine whether any significant differences exist in the simulated performance of these models. The models were subjected to a "metabolic" stress either in the form of variable strong ion difference and fixed weak acid effect, or vice versa, and compared over the range 25 < or = Pco(2) < or = 135 Torr. The predictive equations for each model were iteratively solved for pH at each Pco(2) step, and the results were plotted as a series of log(Pco(2))-pH titration curves. The results were analyzed for linearity by using ordinary least squares regression and for collinearity by using correlation. In every case, the results revealed a linear relationship between log(Pco(2)) and pH over the range 6.8 < or = pH < or = 7.8, and no significant difference between the curve predictions under metabolic stress. The curves were statistically collinear. Ultimately, their clinical utility will be determined both by acceptance of the strong ion framework for describing acid-base physiology and by the ease of measurement of the independent model parameters.

Stimulation of intestinal glutamine absorption in chronic metabolic acidosis

BACKGROUND

Amino acid glutamine plays a central role in inter-organ nitrogen transfer in acidosis, a compensatory mechanism that is essential in maintaining acidbase balance. Intestinal glutamine absorption is a key exogenous glutamine source in maintaining glutamine homeostasis. The purpose of this in vivo study was to investigate the regulation of intestinal glutamine absorption during chronic metabolic acidosis.

METHODS

Metabolic acidosis in adult male Sprague-Dawley rats was induced by adding 1.5% NH4Cl to drinking water. [3H]-L-glutamine transport activity across brush border membrane vesicles and glutamine transporter ATB0 messenger RNA levels by relative reverse transcriptase-polymerase chain reaction were measured in rat jejunum. Data were analyzed by t test (P < .05).

RESULTS

Acidosis occurred as early as 1 day and was partially compensated by 7 days. Glutamine transport in brush border membrane vesicles was increased after 2 days of acidosis. Chronic acidosis (7 days) resulted in an 8-fold increase of glutamine transport activity. The glutamine transport maximal capacity (Vmax) was stimulated 5-fold, while the transport affinity (Km) was not affected by acidosis. Relative reverse transcriptase-polymerase chain reaction showed a 2.5-fold increase of glutamine transporter ATB0 messenger RNA levels.

CONCLUSIONS

Chronic metabolic acidosis stimulates intestinal glutamine absorption via a mechanism that involves an increase of functional membrane glutamine transporter units.

Lactic and hydrochloric acids induce different patterns of inflammatory response in LPS-stimulated RAW 264.7 cells

Metabolic acidosis frequently complicates sepsis and septic shock and may be deleterious to cellular function. Different types of metabolic acidosis (e.g., hyperchloremic and lactic acidosis) have been associated with different effects on the immune response, but direct comparative studies are lacking. Murine macrophage-like RAW 264.7 cells were cultured in complete medium with lactic acid or HCl to adjust the pH between 6.5 and 7.4 and then stimulated with LPS ( Escherichia coli 0111:B4; 10 ng/ml). Nitric oxide (NO), IL-6, and IL-10 levels were measured in the supernatants. RNA was extracted from the cell pellets, and RT-PCR was performed to amplify corresponding mediators. Gel shift assay was also performed to assess NF-κB DNA binding. Increasing concentrations of acid caused increasing acidification of the media. Trypan blue exclusion and lactate dehydrogenase release demonstrated that acidification did not reduce cell viability. HCl significantly increased LPS-induced NO release and NF-κB DNA binding at pH 7.0 but not at pH 6.5. IL-6 and IL-10 expression (RNA and protein) were reduced with HCl-induced acidification, but IL-10 was reduced much more than IL-6 at low pH. By contrast, lactic acid significantly decreased LPS-induced NO, IL-6, and IL-10 expression in a dose-dependent manner. Lactic acid also inhibited LPS-induced NF-κB DNA binding. Two common forms of metabolic acidosis (hyperchloremic and lactic acidosis) are associated with dramatically different patterns of immune response in LPS-stimulated RAW 264.7 cells. HCl is essentially proinflammatory as assessed by NO release, IL-6-to-IL-10 ratios, and NF-κB DNA binding. By contrast, lactic acidosis is anti-inflammatory.