[Blood gas analysis in the intensive cardiac care unit]. / La rapida lettura dell'emogasanalisi in unità di terapia intensiva cardiologica.

Arterial blood gas (ABG) analysis is a simple and quick test that can provide multiple respiratory and metabolic parameters. The interpretation of ABG analysis and acid-base disorders represents one of the most complex chapters of clinical medicine. In this brief review, the authors propose a rational approach that sequentially analyzes the information offered by the ABG to allow a rapid classification of the respiratory, metabolic or mixed disorder. The patient's history and clinical-instrumental assessment are the framework in which to insert the information derived from the ABG analysis in order to characterize the critical heart patient.

[Comparison of different methods for monitoring of acid base status in dairy cow herds]. / Methodenvergleich zur Überwachung des Säuren-Basen-Status in Milchviehherden.

OBJECT AND PURPOSE: Acid-base disorders in dairy herds can be diagnosed by determining urinary net base excretion (NBE). Modifications of this method are the differential NBE (dNBE) with determination of the urinary concentration-independent base-acid ratio (BAR) and the simplified NBE test with reduced urine volume (sNBE). The aim of this study was to compare these methods among themselves and as a pooled test, in their assessment of cow group acid base status as well as to derive recommendations for practical use. ANIMALS, MATERIAL, AND METHODS: The concentrations of NBE, dNBE, and sNBE were measured in urine samples derived from 855 German-Holstein cows in 127 cow groups at different stages of lactation. BAR was then calculated. dNBE and BAR were determined both individually per cow and as a pool of a group. Mixed linear models were used to examine the relationship between the mean of the individual animal values and the pool sample result of a group for these two parameters. In addition, all groups were evaluated with respect to acidotic or alkalotic load based on their single animal results of the respective methods, the mean values formed from them, and the measured pool result. By using the single animal BAR as reference, the sensitivity and specificity of the different methods were calculated. RESULTS: The calculated mean values of the individual measurements of dNBE and BAR differed from the measured value in the pool sample, especially in low and high measurement ranges. In the group assessment, NBE showed the best combined sensitivity and specificity for the detection of acid base disorders. The dNBE pool assay showed satisfactory specificity with respect to acidosis and alkalosis, while the sNBE on an individual animal basis and the BAR determination in the pool showed satisfactory sensitivity with respect to acidosis. CONCLUSIONS AND CLINICAL RELEVANCE: It was shown that NBE determined in individual animal samples is well suited for the assessment of acid base status of cow groups and can therefore be recommended for practical use. The determination of dNBE as well as BAR as a pool test is not sufficient for the detection of alkalotic load in cow groups but may help to confirm an existing acidotic load.

Base excess (BE): reloaded.

The base excess value (BE, mmol/L), not standard base excess (SBE), correctly calculated including pH, pCO2 (mmHg), sO2 (%) and cHb (g/dl) is a diagnostic tool for several in vivo events, e.g., mortality after multiple trauma or shock, acidosis, bleeding, clotting, artificial ventilation. In everyday clinical practice a few microlitres of blood (arterial, mixed venous or venous) are sufficient for optimal diagnostics of any metabolic acidosis or alkalosis.The same applies to a therapeutic tool-then referred to as potential base excess (BEpot)-for several in vitro assessments, e.g., solutions for infusion, sodium bicarbonate, blood products, packed red blood cells, plasma. Thus, BE or BEpot has been a parameter with exceptional clinical significance since 2007.

A Systematic Approach to Understanding Acid-Base Disorders in the Critically Ill.

OBJECTIVE: The objective of this review is to discuss acid-base physiology, describe the essential steps for interpreting an arterial blood gas and relevant laboratory tests, and review the 4 distinct types of acid-base disorders. DATA SOURCES: A comprehensive literature search and resultant bibliography review of PubMed from inception through March 7, 2023. STUDY SELECTION AND DATA EXTRACTION: Relevant English-language articles were extracted and evaluated. DATA SYNTHESIS: Critically ill patients are prone to significant acid-base disorders that can adversely affect clinical outcomes. Assessing these acid-base abnormalities can be complex because of dynamic aberrations in plasma proteins, electrolytes, extracellular volume, concomitant therapies, and use of mechanical ventilation. This article provides a systematic approach to acid-base abnormalities which is necessary to facilitate prompt identification of acid-base disturbances and prevent untoward morbidity and mortality. RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE: Many acid-base disorders result from medication therapy or are treated with medications. Pharmacists are uniquely poised as the medication experts on the multidisciplinary team to assist with acid-base assessments in the context of pharmacotherapy. CONCLUSION: The use of a systematic approach to address acid-base disorders can be performed by all pharmacists to improve pharmacotherapy and optimize patient outcomes.

Evaluating a low anion gap: A practical approach.

In teaching and in practice, little attention is given to a low anion gap. This oversight can result in a missed opportunity to diagnose acute or chronic disorders requiring treatment. In this article, we review the constituents of the anion gap, build a differential diagnosis for a low anion gap using case examples, and provide a stepwise approach to diagnostic testing to evaluate this abnormal finding.

Metabolic Acid-Base Disorders.

Metabolic acid-base disturbances are frequently encountered in the emergency department, and many of these patients are critically ill. In the evaluation of patients with these maladies, it is important for the emergency clinician to determine the cause, which can usually be elicited from a thorough history and physical examination. There are several mnemonics that can be used to form an appropriate list of potential causes. Most of the time, the management of these patients requires no specific treatment of the acid-base status but, rather, requires treatment of the underlying disorder that is causing the acid-base disturbance.

Spurious Electrolyte and Acid-Base Disorders in the Patient With Cancer: A Review.

Electrolyte and acid-base disorders are frequently encountered in patients with malignancy, either due to cancer itself or as a complication of its therapy. However, spurious electrolyte disorders can complicate the interpretation and management of these patients. Several electrolytes can be artifactually increased or decreased such that the serum electrolyte values do not correspond to their actual systemic levels, potentially resulting in extensive diagnostic investigations and therapeutic interventions. Examples of spurious derangements include pseudohyponatremia, pseudohypokalemia, pseudohyperkalemia, pseudohypophosphatemia, pseudohyperphosphatemia, and artifactual acid-base abnormalities. Correctly interpreting these artifactual laboratory abnormalities is imperative for avoiding unnecessary and potentially harmful interventions in cancer patients. The factors influencing these spurious results also must be recognized, along with the steps to minimize them. We present a narrative review of commonly reported pseudo electrolyte disorders and describe strategies to exclude erroneous interpretations of these laboratory values and avoid pitfalls. Awareness and recognition of spurious electrolyte and acid-base disorders can prevent unnecessary and harmful treatments.

Acid-Base Disorders in the Critically Ill Patient.

Acid-base disorders are common in the intensive care unit. By utilizing a systematic approach to their diagnosis, it is easy to identify both simple and mixed disturbances. These disorders are divided into four major categories: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis. Metabolic acidosis is subdivided into anion gap and non-gap acidosis. Distinguishing between these is helpful in establishing the cause of the acidosis. Anion gap acidosis, caused by the accumulation of organic anions from sepsis, diabetes, alcohol use, and numerous drugs and toxins, is usually present on admission to the intensive care unit. Lactic acidosis from decreased delivery or utilization of oxygen is associated with increased mortality. This is likely secondary to the disease process, as opposed to the degree of acidemia. Treatment of an anion gap acidosis is aimed at the underlying disease or removal of the toxin. The use of therapy to normalize the pH is controversial. Non-gap acidoses result from disorders of renal tubular H + transport, decreased renal ammonia secretion, gastrointestinal and kidney losses of bicarbonate, dilution of serum bicarbonate from excessive intravenous fluid administration, or addition of hydrochloric acid. Metabolic alkalosis is the most common acid-base disorder found in patients who are critically ill, and most often occurs after admission to the intensive care unit. Its etiology is most often secondary to the aggressive therapeutic interventions used to treat shock, acidemia, volume overload, severe coagulopathy, respiratory failure, and AKI. Treatment consists of volume resuscitation and repletion of potassium deficits. Aggressive lowering of the pH is usually not necessary. Respiratory disorders are caused by either decreased or increased minute ventilation. The use of permissive hypercapnia to prevent barotrauma has become the standard of care. The use of bicarbonate to correct the acidemia is not recommended. In patients at the extreme, the use of extracorporeal therapies to remove CO 2 can be considered.

Acid-Base.

In clinical medicine, evaluation of acid-base balance can be a valuable diagnostic and monitoring tool. Blood gas machines need very small volumes of blood and provide immediate results, making them ideal for use in the emergency room and intensive care setting. This review outlines the stepwise approach to assessment of acid-base balance in dogs, common causes of acid-base abnormalities, and the general approach to treatment.

Fundamentals of Arterial Blood Gas Interpretation.

Acid-base disturbances in patients with cardiopulmonary or other disorders are common and are often misinterpreted or interpreted incompletely. Treating acid-base disorders in greater detail facilitates pathophysiologic understanding and improved therapeutic planning. Understanding the ratiometric relationship between the lungs, which excrete volatile acid as carbon dioxide, and the kidneys, which contribute to maintenance of plasma bicarbonate, allows precise identification of the dominant acid-base disturbance when more than a simple disorder is present and aids in executing a measured treatment response. Concordantly, mapping paired values of the partial pressure of carbon dioxide (PCO2) and the bicarbonate concentration ([HCO3 -]) on a Cartesian coordinate system visually defines an acid-base disorder and validates the ratiometric methodology. We review and demonstrate the algebraic and logarithmic methods of arterial blood gas analysis through the example of a complex acid-base disorder, emphasizing examination of the PCO2-to-[HCO3 -] ratio.

Acid-base disorders: A primer for clinicians.

An understanding of acid-base physiology is necessary for clinicians to recognize and correct problems that may negatively affect provision of nutrition support and drug therapy. An overview of acid-base physiology, the different acid-base disorders encountered in practice, a stepwise approach to evaluate arterial blood gases, and other key diagnostic tools helpful in formulating a safe and effective medical and nutrition plan are covered in this acid-base primer. Case scenarios are also provided for the application of principles and the development of clinical skills.

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.

[Analysis of acid-base disturbances in the emergency department]. / ABC om Syra­bastolkning på akuten.

The analysis of acid-base disturbances contributes to the diagnostic work-up of critically ill patients. Most emergency departments are equipped with blood gas point-of-care analyzers that quantify within minutes pH, pCO2, standard bicarbonate, standard base excess, sodium and chloride levels. This article provides a pragmatic stepwise approach to the analysis of acid-base disturbances in the emergency department. Standard base excess is used to assess the adequacy of the secondary (compensatory) response. Calculation of the anion gap based on the actual bicarbonate is used to identify the coexistence of metabolic acidosis and metabolic alkalosis. The delta anion gap allows for the identification of measurement errors, such as falsely elevated lactate and chloride values, which in turn may provide diagnostic clues.

Association between anion gap and mortality of aortic aneurysm in intensive care unit after open surgery.

BACKGROUND: There has not been a well-accepted prognostic model to predict the mortality of aortic aneurysm patients in intensive care unit after open surgery repair. Otherwise, our previous study found that anion gap was a prognosis factor for aortic aneurysm patients. Therefore, we wanted to investigate the relationship between anion gap and mortality of aortic aneurysm patients in intensive care unit after open surgery repair. METHODS: From Medical Information Mart for Intensive Care III, data of aortic aneurysm patients in intensive care unit after open surgery were enrolled. The primary clinical outcome was defined as death in intensive care unit. Univariate analysis was conducted to compare the baseline data in different groups stratified by clinical outcome or by anion gap level. Restricted cubic spline was drawn to find out the association between anion gap level and mortality. Subgroup analysis was then conducted to show the association in different level and was presented as frost plot. Multivariate regression models were built based on anion gap and were adjusted by admission information, severity score, complication, operation and laboratory indicators. Receiver operating characteristic curves were drawn to compare the prognosis ability of anion gap and simplified acute physiology score II. Decision curve analysis was finally conducted to indicate the net benefit of the models. RESULTS: A total of 405 aortic aneurysm patients were enrolled in this study and the in-intensive-care-unit (in-ICU) mortality was 6.9%. Univariate analysis showed that elevated anion gap was associated with high mortality (P value < 0.001), and restricted cubic spline analysis showed the positive correlation between anion gap and mortality. Receiver operating characteristic curve showed that the mortality predictive ability of anion gap approached that of simplified acute physiology score II and even performed better in predicting in-hospital mortality (P value < 0.05). Moreover, models based on anion gap showed that 1 mEq/L increase of anion gap improved up to 42.3% (95% confidence interval 28.5-59.8%) risk of death. CONCLUSIONS: The level of serum anion gap was an important prognosis factor for aortic aneurysm mortality in intensive care unit after open surgery.

Approach to Patients With High Anion Gap Metabolic Acidosis: Core Curriculum 2021.

The anion gap (AG) is a mathematical construct that compares the blood sodium concentration with the sum of the chloride and bicarbonate concentrations. It is a helpful calculation that divides the metabolic acidoses into 2 categories: high AG metabolic acidosis (HAGMA) and hyperchloremic metabolic acidosis-and thereby delimits the potential etiologies of the disorder. When the [AG] is compared with changes in the bicarbonate concentration, other occult acid-base disorders can be identified. Furthermore, finding that the AG is very small or negative can suggest several occult clinical disorders or raise the possibility of electrolyte measurement artifacts. In this installment of AJKD's Core Curriculum in Nephrology, we discuss cases that represent several very common and several rare causes of HAGMA. These case scenarios highlight how the AG can provide vital clues that direct the clinician toward the correct diagnosis. We also show how to calculate and, if necessary, correct the AG for hypoalbuminemia and severe hyperglycemia. Plasma osmolality and osmolal gap calculations are described and when used together with the AG guide appropriate clinical decision making.

Pseudohyperchloremia and Negative Anion Gap - Think Salicylate!

BACKGROUND: Pseudohyperchloremia results in a very low or negative anion gap. Historically, the most common cause of this artifact was bromide poisoning. Bromide salts have been removed from most medications and bromism has become very uncommon. More recently, the introduction of chloride ion selective sensing electrodes (Cl-ISE) has generated a new cause of pseudohyperchloremia-salicylate poisoning. We describe 5 such patients and quantitate the error generated by this measurement artifact. METHODS: The magnitude of artifactual hyperchloremia generated by high salicylate levels was quantified in 5 patients by measuring chloride concentration with several Cl-ISEs from different manufacturers and with Cl-ISEs of different "ages," and comparing these results to measurements with a chloridometer (coulometric titration), which is free of the salicylate artifact. RESULTS: Cl-ISEs from different manufacturers generated a wide range of artifactual chloride concentration elevation. Furthermore, the same Cl-ISE generated increasingly severe pseudohyperchloremia as it was repeatedly reused over time and "aged." CONCLUSIONS: Salicylate interferes with measurement of the blood chloride concentration when a Cl-ISE is used. The severity of this artifact is related to the salicylate level, the specific Cl-ISE, and the "age" of the electrode. Toxic blood salicylate levels can generate marked pseudohyperchloremia, and consequently, an artifactual very small or negative anion gap. The large anion gap metabolic acidosis typical of salicylate poisoning is masked by this artifact. Salicylate has become the most common cause of pseudohyperchloremia, and physicians should immediately consider salicylate poisoning whenever the combination of hyperchloremia and a very small or negative anion gap is reported by the laboratory.

Base-excess chloride; the best approach to evaluate the effect of chloride on the acid-base status: A retrospective study.

To practically determine the effect of chloride (Cl) on the acid-base status, four approaches are currently used: accepted ranges of serum Cl values; Cl corrections; the serum Cl/Na ratio; and the serum Na-Cl difference. However, these approaches are governed by different concepts. Our aim is to investigate which approach to the evaluation of the effect of Cl is the best. In this retrospective cohort study, 2529 critically ill patients who were admitted to the tertiary care unit between 2011 and 2018 were retrospectively evaluated. The effects of Cl on the acid-base status according to each evaluative approach were validated by the standard base excess (SBE) and apparent strong ion difference (SIDa). To clearly demonstrate only the effects of Cl on the acid-base status, a subgroup that included patients with normal lactate, albumin and SIG values was created. To compare approaches, kappa and a linear regression model for all patients and Bland-Altman test for a subgroup were used. In both the entire cohort and the subgroup, correlations among BECl, SIDa and SBE were stronger than those for other approaches (r = 0.94 r = 0.98 and r = 0.96 respectively). Only BECl had acceptable limits of agreement with SBE in the subgroup (bias: 0.5 mmol L-1) In the linear regression model, only BECl in all the Cl evaluation approaches was significantly related to the SBE. For the evaluation of the effect of chloride on the acid-base status, BECl is a better approach than accepted ranges of serum Cl values, Cl corrections and the Cl/Na ratio.