A simplified physicochemical approach to acid-base disorders: perioperative practical application.

The objectives of this retrospective study were to determine the main acid-base and electrolytes disorders in hospitalized cattle, using both Henderson-Hasselbalch and the physicochemical approach and to compare their diagnostic and therapeutic utility. A total of 31 medical records were reviewed of bovines admitted to the Large Animal Hospital at Universidad Nacional de Colombia, that met the inclusion criteria of the measurement of blood gases, blood electrolytes and plasma protein on admission before providing any treatment. Using the Henderson-Hasselbalch approach, acid base abnormalities were found in 83.3% of the patients, compared to 93.5% using the physicochemical approach. The principal acid-base disorders found were strong ion acidosis (61.29%) and weak acid acidosis (38.7%); strong ion gap (SIG) acidosis was found in 73.68% of cases showing strong ion acidosis. These results highlight the importance of the diagnosis of acid-base disorders in sick cattle for proper recognition of pathophysiological phenomena and its understanding to guide treatment decisions.

Objective: The traditional approach for acid base interpretation is based on Handerson-Hasselbalch formula and includes Base Excess (BE), bicarbonate (HCO3), albumin corrected anion gap. The Physicochemical approach is centered on the Carbon Dioxide tension (PCO2), the strong ion difference (SID), strong ion gap (SIG) = SID apparent-SID effective and totally weak acids (Atot). The study aims to compare between the traditional approach and the physicochemical approach in acid base disorder interpretation. Design: Prospective observational study in an adult Intensive Care Unit (ICU) recruiting six hundred and sixty one patients. Methods: Arterial blood samples were analyzed to measure pH, PaCO2 sodium, potassium, chloride and lactate. Venous blood samples were analyzed to measure ionized calcium, magnesium, phosphorous and albumin. These samples were interpreted by both techniques. Results: Normal HCO3 and BE were detected by traditional approach in 49 cases of which SIG acidosis was detected in 22 cases (46%) and Hyperchloremic acidosis was detected in 29 cases (60%) by physicochemical method. SIG was elevated in 72 cases (58%) of 124 cases with high anion gap acidosis. SIDeff and BE were strongly correlated, r = 0.8, p 0.0001, while SIG and Albumin corrected Anion Gap (ALAG) were moderately correlated r = 0.56, p Conclusion: Both approaches are important for interpretation of the acid base status. Traditional approach identifies the diagnostic description without many calculations and detects body compensatory response to acid base disorders. Physicochemical approach is essential to identify the exact causation and the severity of the acid base disorders.

This review on the approach to acid-base disorders uses the physiologic approach to assessing acid-base status, namely that based on the H2CO3/[HCO3–] buffer pair. A simple acid-base disorder is characterized by a primary abnormality in either carbon dioxide tension (Pco2) or serum [HCO3–] accompanied by the appropriate secondary response in the other component. The four cardinal, simple acid-base disorders are categorized into respiratory disorders and metabolic disorders. Respiratory disorders are expressed as primary changes in Pco2 and include respiratory acidosis or primary hypercapnia (primary increase in Pco2) and respiratory alkalosis or primary hypocapnia (primary decrease in Pco2). Metabolic disorders are expressed as primary changes in serum [HCO3–]) and include metabolic acidosis (primary decrease in serum [HCO3–]) and metabolic alkalosis (primary increase in serum [HCO3–]). A mixed acid-base disorder denotes the simultaneous occurrence of two or more simple acid-base disorders. Arriving at an accurate acid-base diagnosis rests with assessment of the accuracy of the acid-base variables, calculation of the serum anion gap, and identification of the dominant acid-base disorder and whether a simple or mixed disorder is present. Identifying the cause of the acid-base disorder depends on a detailed history and physical examination as well as obtaining additional testing, as appropriate. Key words: acid-base disorders; simple disorders; mixed disorders; anion gap; physiologic approach; physicochemical approach; base-excess approach

This review on the approach to acid-base disorders uses the physiologic approach to assessing acid-base status, namely that based on the H2CO3/[HCO3–] buffer pair. A simple acid-base disorder is characterized by a primary abnormality in either carbon dioxide tension (Pco2) or serum [HCO3–] accompanied by the appropriate secondary response in the other component. The four cardinal, simple acid-base disorders are categorized into respiratory disorders and metabolic disorders. Respiratory disorders are expressed as primary changes in Pco2 and include respiratory acidosis or primary hypercapnia (primary increase in Pco2) and respiratory alkalosis or primary hypocapnia (primary decrease in Pco2). Metabolic disorders are expressed as primary changes in serum [HCO3–]) and include metabolic acidosis (primary decrease in serum [HCO3–]) and metabolic alkalosis (primary increase in serum [HCO3–]). A mixed acid-base disorder denotes the simultaneous occurrence of two or more simple acid-base disorders. Arriving at an accurate acid-base diagnosis rests with assessment of the accuracy of the acid-base variables, calculation of the serum anion gap, and identification of the dominant acid-base disorder and whether a simple or mixed disorder is present. Identifying the cause of the acid-base disorder depends on a detailed history and physical examination as well as obtaining additional testing, as appropriate. Key words: acid-base disorders; simple disorders; mixed disorders; anion gap; physiologic approach; physicochemical approach; base-excess approach

This review on the approach to acid-base disorders uses the physiologic approach to assessing acid-base status, namely that based on the H2CO3/[HCO3–] buffer pair. A simple acid-base disorder is characterized by a primary abnormality in either carbon dioxide tension (Pco2) or serum [HCO3–] accompanied by the appropriate secondary response in the other component. The four cardinal, simple acid-base disorders are categorized into respiratory disorders and metabolic disorders. Respiratory disorders are expressed as primary changes in Pco2 and include respiratory acidosis or primary hypercapnia (primary increase in Pco2) and respiratory alkalosis or primary hypocapnia (primary decrease in Pco2). Metabolic disorders are expressed as primary changes in serum [HCO3–]) and include metabolic acidosis (primary decrease in serum [HCO3–]) and metabolic alkalosis (primary increase in serum [HCO3–]). A mixed acid-base disorder denotes the simultaneous occurrence of two or more simple acid-base disorders. Arriving at an accurate acid-base diagnosis rests with assessment of the accuracy of the acid-base variables, calculation of the serum anion gap, and identification of the dominant acid-base disorder and whether a simple or mixed disorder is present. Identifying the cause of the acid-base disorder depends on a detailed history and physical examination as well as obtaining additional testing, as appropriate. Key words: acid-base disorders; simple disorders; mixed disorders; anion gap; physiologic approach; physicochemical approach; base-excess approach

ObjectivesTo investigate the acid‐base status of sick goats using the simplified strong ion difference (sSID) approach, to establish the quantitative contribution of sSID variables to changes in blood pH and HCO3 − and to determine whether clinical, acid‐base, and biochemical variables on admission are associated with the mortality of sick goats.AnimalsOne hundred forty‐three sick goats.MethodsRetrospective study. Calculated sSID variables included SID using 6 electrolytes unmeasured strong ions (USI) and the total nonvolatile buffer ion concentration in plasma (Atot). The relationship between measured blood pH and HCO3 −, and the sSID variables was examined using forward stepwise linear regression. Cox proportional hazard models were constructed to assess associations between potential predictor variables and mortality of goats during hospitalization.ResultsHypocapnia, hypokalemia, hyperchloremia, hyperlactatemia, and hyperproteinemia were common abnormalities identified in sick goats. Respiratory alkalosis, strong ion acidosis, and Atot acidosis were acid‐base disorders frequently encountered in sick goats. In sick goats, the sSID variables explained 97% and 100% of the changes in blood pH and HCO3 −, respectively. The results indicated that changes in the respiratory rate (<16 respirations per minute), USI, and pH at admission were associated with increased hazard of hospital mortality in sick goats.Conclusions and Clinical ImportanceThe sSID approach is a useful methodology to quantify acid‐base disorders in goats and to determine the mechanisms of their development. Clinicians should consider calculation of USI in sick goats as part of the battery of information required to establish prognosis.

The traditional approach for clinically assessing acid-base status uses the Henderson-Hasselbalch equation to categorize 4 primary acid-base disturbances: respiratory acidosis (increased PCO2), respiratory alkalosis (decreased PCO2), metabolic acidosis (decreased extracellular base excess or actual HCO3- concentration), and metabolic alkalosis (increased extracellular base excess or actual HCO3- concentration). The anion gap is calculated to detect unidentified anions in plasma. This approach works well clinically and is recommended for use whenever serum total protein, albumin, and phosphate concentrations are approximately normal. However, because the Henderson-Hasselbalch approach is more descriptive than mechanistic, when these concentrations are markedly abnormal the Henderson-Hasselbalch equation frequently provides erroneous information as to the cause of an acid-base disturbance. The new quantitive physicochemical approach to evaluating acid-base balance uses the simplified strong ion model to categorize 6 primary acid-base disturbances: respiratory acidosis (increased PCO2), respiratory alkalosis (decreased PCO2), strong ion acidosis (decreased strong ion difference), strong ion alkalosis (increased strong ion difference), nonvolatile buffer ion acidosis (increased plasma concentrations of albumin, globulins, or phosphate), and nonvolatile buffer ion alkalosis (decreased plasma concentrations of albumin, globulins, or phosphate). The strong ion gap is calculated to detect unidentified anions in plasma. The simplified strong ion approach works well clinically and is recommended for use whenever serum total protein, albumin, or phosphate concentrations are markedly abnormal. The simplified strong ion approach is mechanistic and is therefore well suited for describing the cause of any acid-base disturbance.

Strong ion difference and strong anion gap: The Stewart approach to acid base disturbances

BackgroundSagittal split ramus osteotomy is often associated with significant postoperative pain. Intraoral inferior alveolar nerve blocks have variable success rates and higher risks of vascular complications, while ultrasound-guided approaches to the pterygomandibular space require precise needle placement in a narrow anatomical space. We present a novel perioperative application of ultrasound-guided lateral pterygoid muscle injection for regional anesthesia.Case presentationsThree female patients underwent bilateral sagittal split ramus osteotomy under general anesthesia. After anesthesia induction, ultrasound-guided lateral pterygoid muscle injections were performed using 10 mL of 0.25% levobupivacaine. All patients demonstrated excellent postoperative pain control (numerical rating scale score ≤ 2) with minimal analgesic requirements and no complications.ConclusionThis novel lateral pterygoid muscle injection technique for perioperative analgesia demonstrates promising clinical efficacy through a simplified ultrasound-guided approach, providing effective opioid-free postoperative pain management for sagittal split ramus osteotomy.

Patients with sepsis admitted to the intensive care unit often present with acid-base disorders. As the traditional interpretation might be clinically misleading, an alternative approach described by Stewart may allow one to quantify the individual components of acid-base abnormalities and provide an insight into their pathogenesis. The aim of our study was to compare the traditional and Stewart approaches in the analysis of acid-base disturbance. We analyzed arterial blood gases (ABG) taken from 43 ICU septic patients from admission to discharge categorising them according to SBE values. The traditional concept analysis was compared with the physicochemical approach using the Stewart equations. 990 ABGs were analysed. In the SBE < -2 mEq L⁻¹ group, hyperlactatemia was observed in 34.7% ABG, hypoalbuminemia in 100% and SIG acidosis in 42% ABG. Moreover, a Cl/Na ratio > 0.75 was present in 96.9% ABG. In the normal range SBE group, elevated lactates were present in 21.3% ABG, SIG acidosis in 14.9%, elevated Cl/Na ratio in 98.4% and hypoalbuminemia in all 324 ABG. In the metabolic alkalosis group (SBE > +2 mEq L⁻¹), hyperlactatemia was observed in 18.4% ABG, SIG acidosis in 5% ABG, Cl/Na ratio> 0.75 in 88.8%, while 99.1% samples revealed hypoalbuminemia. The use of the Stewart model may improve our understanding of the underlying pathophysiological mechanism and the true etiology of the derangements of acid-base disorders. Indeed, it proves that patients may suffer from mixed arterial blood gas disorders hidden under normal values of SBE and pH.

Introduction: Arterial Blood Gas (ABG) interpretation plays an indispensable role in emergency medicine and the care of intensive care patients, yet it remains a challenging task. Although several graphical methods exist for ABG interpretation, they are not commonly used at the bedside. The existing graphs are complicated, difficult to understand, and unable to diagnose many disorders. In previous research articles, the current author developed and published a four-quadrant graphical tool for ABG interpretation. The tool incorporates compensation rules, which are crucial for identifying changes resulting from compensations or the presence of a second primary acid-base disorder. Aim: To develop a method for applying compensation rules in a four-quadrant graphical tool to interpret ABG reports for complex acid-base disorders in clinical practice. Materials and Methods: This cross-sectional study was conducted at Shri Sathya Sai Medical College and Research Institute, Chennai, Tamil Nadu, India, from November 2022 to April 2023. A total of 232 ABG samples were utilised, and the values of pH, pCO2, HCO3, Standard HCO3, and Standard Base Excess (SBE) were recorded. These values were classified according to different acid-base disorders. Three derived ratios were calculated using the values of pCO2, bicarbonate, and standard bicarbonate, as these ratios change in various acid-base disorders and provide clues for differentiating between different acid-base disturbances. A four-quadrant graph method was constructed using the values of SBE, pCO2, and these ratios. Subsequently, compensation rules were applied to this graph method. Results: The four-quadrant method facilitated the easy identification of different acid-base disorders, and the application of compensation rules further simplified the identification of mixed or compensatory acid-base disorders. Conclusion: The application of compensation rules in this four- quadrant graphical tool for ABG interpretation distinguishes this tool as a unique method among existing approaches. This tool offers an optimal and simplified approach for interpreting ABG results for complex acid-base disturbances, making it highly suitable for clinical practice at the bedside.

Background: Stewart’s approach is known to have better diagnostic accuracy for the identification of metabolic acid–base disturbances compared to traditional methods based either on plasma bicarbonate concentration ([HCO3−]) and anion gap (AG) or on base excess/deficit (BE). This study aimed to identify metabolic acid–base disorders using either Stewart’s or traditional approaches in critically ill COVID-19 patients admitted to the ICU, to recognize potential hidden acid–base metabolic abnormalities and to assess the prognostic value of these abnormalities for patient outcome. Methods: This was a single-center retrospective study, in which we collected data from patients with severe COVID-19 admitted to the ICU. Electronical files were used to retrieve data for arterial blood gases, serum electrolytes, and proteins and to derive [HCO3−], BE, anion gap (AG), AG adjusted for albumin (AGadj), strong ion difference, strong ion gap (SIG), and SIG corrected for water excess/deficit (SIGcorr). The acid–base status was evaluated in each patient using the BE, [HCO3−], and physicochemical approaches. Results: We included 185 patients. The physicochemical approach detected more individuals with metabolic acid–base abnormalities than the BE and [HCO3−] approaches (p < 0.001), and at least one acid–base disorder was recognized in most patients. According to the physicochemical method, 170/185 patients (91.4%) had at least one disorder, as opposed to the number of patients identified using the BE 90/186 (48%) and HCO3 62/186 (33%) methods. Regarding the derived acid–base status variables, non-survivors had greater AGadj, (p = 0.013) and SIGcorr (p = 0.035) compared to survivors. Conclusions: The identification of hidden acid–base disturbances may provide a detailed understanding of the underlying conditions in patients and of the possible pathophysiological mechanisms implicated. The association of these acid–base abnormalities with mortality provides the opportunity to recognize patients at increased risk of death and support them accordingly.

Internal acid–base homeostasis is fundamental for maintaining life. Accurate and timely interpretation of an acid–base disorder can be lifesaving, but the establishment of a correct diagnosis may be challenging.1 The three major methods of quantifying acid–base disorders are the physiological approach, the base-excess approach, and the physicochemical approach (also called the Stewart method).2 This article reviews a stepwise method for the physiological approach. The physiological approach uses the carbonic acid–bicarbonate buffer system. Based on the isohydric principle, this system characterizes acids as hydrogen-ion donors and bases as hydrogen-ion acceptors. The carbonic acid–bicarbonate system is important in maintaining homeostatic control. In . . .

Bedside rule secondary response in metabolic acid-base disorders is unreliable

Assessment of acid–base disorders