Serum anion gap in the differential diagnosis of metabolic acidosis in critically ill newborns

Association between early metabolic acidosis and bronchopulmonary dysplasia/death in preterm infants born at less than 28 weeks' gestation: an observational cohort study

BACKGROUND

Metabolic acidosis occurs frequently during the first postnatal days in extremely preterm infants and is mainly attributed to renal immaturity. Recent studies suggested a link between metabolic acidosis and the development of BPD. The aim of this study was to systematically investigate the association between severe metabolic acidosis during the first two weeks of life and bronchopulmonary dysplasia (BPD) / mortality among preterm infants born before 28 weeks' gestation.

METHODS

Monocentric observational cohort study including 1748 blood gas samples of 138 extremely preterm infants born 2020-2022. Metabolic acidosis was defined as pH < 7.2 with base excess (BE) < -10 mmol/L or standard bicarbonate (SBC) < 12 mmol/L. Primary outcome was BPD and/or death at 36 weeks postmenstrual age.

RESULTS

Fifty-six (40.6%) infants had BPD/death. Metabolic acidosis occurred in 50.0% of infants with BPD/death, compared to 22.0% of BPD-free survivors (p = 0.001) during the first 14 postnatal days. Minimum pH (median 7.12 vs. 7.19, p < 0.001), BE (median -10.9 vs. -9.5 mmol/L, p = 0.005), SBC (median 14.7 vs. 16.1 mmol/L, p < 0.001) were different between the two groups. After adjusting for confounders, pH (postnatal days 2-6), BE (postnatal day 3) and SBC (postnatal days 2-4) were significantly lower in infants with BPD/death. Metabolic acidosis on postnatal days 1-7 was associated with higher odds of BPD (adjusted Odds Ratio (aOR) 3.461, 95% CI 1.325-9.042) and BPD/death (aOR 3.087, 95% CI 1.225-7.778).

CONCLUSIONS

Metabolic acidosis during the first week of life was associated with higher odds of BPD/death in extremely preterm infants.

Association between Serum Lactate and Morbidity and Mortality in Neonates: A Systematic Review and Meta-Analysis

OBJECTIVE

Lactate is a marker of hypoperfusion in critically ill patients. Whether lactate is useful for identifying and stratifying neonates with a higher risk of adverse outcomes remains unknown. This study aimed to investigate the association between lactate and morbidity and mortality in neonates.

METHODS

A meta-analysis was performed to determine the association between blood lactate levels and outcomes in neonates. Ovid MEDLINE, EMBASE, Cochrane Library, and ClinicalTrials.gov were searched from inception to 1 May 2021. A total of 49 observational studies and 14 data accuracy test studies were included. The risk of bias was assessed using the Newcastle-Ottawa Scale for observational studies and the QUADAS-2 tool for data accuracy test studies. The primary outcome was mortality, while the secondary outcomes included acute kidney injury, necessity for renal replacement therapy, neurological outcomes, respiratory morbidities, hemodynamic instability, and retinopathy of prematurity.

RESULTS

Of the 3184 articles screened, 63 studies fulfilled all eligibility criteria, comprising 46,069 neonates. Higher lactate levels are associated with mortality (standard mean difference, -1.09 [95% CI, -1.46 to -0.73]). Using the estimated sensitivity (0.769) and specificity (0.791) and assuming a prevalence of 15% for adverse outcomes (median of prevalence among studies) in a hypothetical cohort of 10,000 neonates, assessing the lactate level alone would miss 346 (3.46%) cases (false negative) and wrongly diagnose 1776 (17.76%) cases (false positive).

CONCLUSIONS

Higher lactate levels are associated with a greater risk of mortality and morbidities in neonates. However, our results do not support the use of lactate as a screening test to identify adverse outcomes in newborns. Research efforts should focus on analyzing serial lactate measurements, rather than a single measurement.

The practices of intravenous sodium bicarbonate therapy in neonatal intensive care units: A multi-country survey

A common occurrence in the neonatal intensive care unit (NICU) is metabolic acidosis. Sodium bicarbonate (SB) has been widely used, but there is insufficient evidence on how SB affects neonates in NICUs with metabolic acidosis. The worsening of intracellular acidosis, the impairment of myocardial function, fluctuations in cerebral blood flow, and intracranial hemorrhage are some of the unfavorable effects of SB treatment in neonates that have been documented in the literature. This study aimed to explore neonatologists' practices for using intravenous SB (ISB) in NICUs. A multi-country survey was carried out in 2022 using an online questionnaire sent to neonatologists in various countries in order to gather information about the use of ISB in NICUs. A previously validated questionnaire was adapted and used in this study. The response rate was 67%. The findings show that 91.2% of neonatologists were using SB to correct metabolic acidosis in the NICU; 71.4% did not have written guidelines for using sodium bicarbonate. The majority of them (78.9%) reported that dosage is included in their guidelines for the use of ISB. The findings of this study emphasize the critical importance of providing guidelines in using ISB for managing metabolic acidosis in NICU to standardize procedures and reduce the use of potentially unsuitable and unsafe treatments, as it has been shown that 71.4% of neonatologists worldwide use sodium bicarbonate without guidelines.

Association between delta anion gap and hospital mortality for patients in cardiothoracic surgery recovery unit: a retrospective cohort study

Backgrounds

High level of anion gap (AG) was associated with organic acidosis. This study aimed to explore the relationship between delta AG (ΔAG = AG_max − AG_min) during first 3 days after intensive care unit (ICU) admission and hospital mortality for patients admitted in the cardiothoracic surgery recovery unit (CSRU).

Methods

In this retrospective cohort study, we identified patients from the open access database called Multiparameter Intelligent Monitoring in Intensive Care III (MIMIC III). A logistic regression model was established to predict hospital mortality by adjusting confounding factors using a stepwise backward elimination method. We conducted receiver operating characteristic (ROC) curves to compare the diagnostic performance of acid–base variables. Cox regression model and Kaplan Meier curve were applied to predict patients’ 90-day overall survival (OS).

Results

A total of 2,860 patients were identified. ΔAG was an independent predictive factor of hospital mortality (OR = 1.24 per 1 mEq/L increase, 95% CI: 1.11–1.39, p < 0.001). The area under curve (AUC) values of ΔAG suggested a good diagnostic accuracy (AUC = 0.769). We established the following formula to estimate patients’ hospital mortality: Logit(P) = − 15.69 + 0.21ΔAG + 0.13age-0.21BE + 2.69AKF. After calculating Youden index, patients with ΔAG ≥ 7 was considered at high risk (OR = 4.23, 95% CI: 1.22–14.63, p = 0.023). Kaplan Meier curve demonstrated that patients with ΔAG ≥ 7 had a poorer 90-day OS (Adjusted HR = 3.20, 95% CI: 1.81–5.65, p < 0.001).

Conclusion

ΔAG is a prognostic factor of hospital mortality and 90-day OS. More prospective studies are needed to verify and update our findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-022-01625-9.

Use of intravenous sodium bicarbonate in neonatal intensive care units in Italy: a nationwide survey

Background

Metabolic Acidosis (MA) is a disturbance of the acid-base balance that can occur in preterm and critically ill term neonates due to different etiologies. Intravenous sodium bicarbonate (SB) has been traditionally used to correct such unbalance, despite the lack of evidence about its safety and efficacy. In literature, reported undesirable effects of treatment with SB in neonates include worsening of intracellular acidosis, impairment of myocardial function, cerebral blood flow fluctuations and intracranial hemorrhage. A national survey was conducted by the Neonatal Pharmacotherapy Study Group of the Italian Society of Neonatology with the aim to assess and describe attitudes and practices concerning the use of SB, particularly for the treatment of MA in Italian NICUs.

Methods

A questionnaire regarding treatment of MA and SB prescription habits was sent to the directors of 120 Italian NICUs from June 2017 to March 2018.

Results

The survey response rate was 97.5% (117/120 centers). Findings showed that in 55% of the surveyed NICUs (64/117 units) it is common practice to correct MA with intravenous SB. On the other hand, the remaining 45% of the units try to solve the metabolic disturbances adopting different approaches (improving perfusion, adjusting ventilation parameters or increasing blood volume). Moreover, to prevent the occurrence of MA, 37.6% of the NICUs (44/117) include buffer salts (lactate, acetate or both) in parenteral nutrition prescriptions. SB is also used as a treatment for other conditions, mainly pathologies with bicarbonate loss and tubular acidosis (respectively in 53.8 and 32.5% of the NICUs).

Conclusion

This survey showed how SB is a commonly used treatment for MA in more than half of Italian NICUs, with indications and prescription criteria that significantly vary across centers. Based on current knowledge, it is reasonable to suggest that the management of neonatal MA should be firstly directed to identify the underlying disorders. Thus, the use of SB should be reserved only for selected cases, also considering the severity of SB adverse effects and the lack of evidence about its efficacy. Guidance for the management of MA is required to harmonize practices and reduce the use of potentially inappropriate and unsafe treatments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-021-00955-3.

A Simple Method of Calculation in Excel for the Protein Requirements in Preterm New Borns

INTRODUCTION

The nutritional balance between the nutritional requirements of the organism and the intake is a very delicate thing to adjust especially when it comes to the premature new-born in whom often the oral feeding is very challenging and the need for parenteral feeding is very pressing.

PURPOSE

The goal of this article is to present a simple method of calculation for the amino acid parenteral intake in preterm infants using the Excel spreadsheet platform as a platform.

MATERIAL AND METHOD

Using Excel commands, we translate the algorithms for the protein requirements calculation into an electronic format. This will allow the creation of a template that quickly identifies the need for proteins according to the clinical and evolutional features of the premature new-born, significantly reducing the duration of the calculation.

RESULTS

This method is easy to perform, simple and efficient. The calculation template has significantly reduced the errors and the actual working time with the algorithms. These effects are very obvious in intensive care units that take care of a large number of premature babies.

CONCLUSIONS

Computerized calculation allows a decrease in calculation errors and also reduces the time actually allocated for the calculation, especially for the very complicated algorithms. Following this template in Excel, we can create separate modules for the algorithms necessary to calculate the needs for the intake of liquids, calories, lipids, and minerals.

Optimizing operational efficiencies in early phase trials: The Pediatric Trials Network experience

Performing drug trials in pediatrics is challenging. In support of the Best Pharmaceuticals for Children Act, the Eunice Kennedy Shriver National Institute of Child Health and Human Development funded the formation of the Pediatric Trials Network (PTN) in 2010. Since its inception, the PTN has developed strategies to increase both efficiency and safety of pediatric drug trials. Through use of innovative techniques such as sparse and scavenged blood sampling as well as opportunistic study design, participation in trials has grown. The PTN has also strived to improve consistency of adverse event reporting in neonatal drug trials through the development of a standardized adverse event table. We review how the PTN is optimizing operational efficiencies in pediatric drug trials to increase the safety of drugs in children.

Endocrine and metabolic emergencies in children: hypocalcemia, hypoglycemia, adrenal insufficiency, and metabolic acidosis including diabetic ketoacidosis

It is important to fast diagnosis and management of the pediatric patients of the endocrine metabolic emergencies because the signs and symptoms of these disorders are nonspecific. Delayed diagnosis and treatment may lead to serious consequences of the pediatric patients, for example, cerebral dysfunction leading to coma or death of the patients with hypoglycemia, hypocalcemia, adrenal insufficiency, or diabetic ketoacidosis. The index of suspicion of the endocrine metabolic emergencies should be preceded prior to the starting nonspecific treatment. Importantly, proper diagnosis depends on the collection of blood and urine specimen before nonspecific therapy (intravenous hydration, electrolytes, glucose or calcium injection). At the same time, the taking of precise history and searching for pathognomonic physical findings should be performed. This review was described for fast diagnosis and proper management of hypoglycemic emergencies, hypocalcemia, adrenal insufficiency, and metabolic acidosis including diabetic ketoacidosis.

Drug-induced acid-base disorders

The incidence of acid-base disorders (ABDs) is high, especially in hospitalized patients. ABDs are often indicators for severe systemic disorders. In everyday clinical practice, analysis of ABDs must be performed in a standardized manner. Highly sensitive diagnostic tools to distinguish the various ABDs include the anion gap and the serum osmolar gap. Drug-induced ABDs can be classified into five different categories in terms of their pathophysiology: (1) metabolic acidosis caused by acid overload, which may occur through accumulation of acids by endogenous (e.g., lactic acidosis by biguanides, propofol-related syndrome) or exogenous (e.g., glycol-dependant drugs, such as diazepam or salicylates) mechanisms or by decreased renal acid excretion (e.g., distal renal tubular acidosis by amphotericin B, nonsteroidal anti-inflammatory drugs, vitamin D); (2) base loss: proximal renal tubular acidosis by drugs (e.g., ifosfamide, aminoglycosides, carbonic anhydrase inhibitors, antiretrovirals, oxaliplatin or cisplatin) in the context of Fanconi syndrome; (3) alkalosis resulting from acid and/or chloride loss by renal (e.g., diuretics, penicillins, aminoglycosides) or extrarenal (e.g., laxative drugs) mechanisms; (4) exogenous bicarbonate loads: milk-alkali syndrome, overshoot alkalosis after bicarbonate therapy or citrate administration; and (5) respiratory acidosis or alkalosis resulting from drug-induced depression of the respiratory center or neuromuscular impairment (e.g., anesthetics, sedatives) or hyperventilation (e.g., salicylates, epinephrine, nicotine).

Metabolic acidosis in the first 14 days of life in infants of gestation less than 26 weeks

Extremely immature newborns develop a self-limiting normal anion gap metabolic acidosis in early life. This study examined the natural history of this acidosis in a population of infants of gestation less than 26 weeks in the first 14 days of life. The acidosis was maximal on day 4 with a mean base deficit of 10.6 mmol/l and had resolved in 90 % of infants by day 11. Dopamine usage was the only independent predictor of the acidosis. Its use was associated with a greater degree of acidosis.

CONCLUSION

Extremely preterm infants experience a self-limiting normal anion gap metabolic acidosis in the first 2 weeks of life which is consistent with renal tubular immaturity.

[Inherited metabolic disorders in pediatric emergency services]

INTRODUCTION

Advances in the early diagnosis and treatment have led to improved survival, and a better quality of life for patients with inherited metabolic disorders (IMD). They can go to the Pediatric Emergency Services (PES) for reasons unrelated to their disease. The purpose of this study was to review the characteristics of visitors to the PES of these patients in a tertiary hospital.

MATERIAL AND METHODS

A retrospective observational study was conducted on all visits from patients with IMD to the PES of Hospital Infantil La Paz over the years 2011 and 2012. IMD type, complaint, duration of symptoms, need for hospitalization, and presence of metabolic decompensation was recorded.

RESULTS

A total of 107 visits were analyzed, with the most frequent reason being for consultation of respiratory processes (30.8%). When the consultation was for vomiting, patients with protein-related disorders were those who delayed less in going to PES. One third of visitors were admitted, half of them due to metabolic decompensation of the underlying pathology.

CONCLUSIONS

Patients with IMD came to PES for many different reasons, which in some cases were the cause or consequence of an acute metabolic decompensation that led to hospitalization. Being diseases with low prevalence, it would be useful to have diagnostic and therapeutic protocols in order to provide optimal care.

Paediatric acid-base disorders: A case-based review of procedures and pitfalls

Acid-base disorders occur frequently in paediatric patients. Despite the perception that their analysis is complex and difficult, a straightforward set of rules is sufficient to interpret even the most complex disorders - provided certain pitfalls are avoided. Using a case-based approach, the present article reviews the fundamental concepts of acid-base analysis and highlights common mistakes and oversights. Specific topics include the proper identification of the primary disorder; distinguishing compensatory changes from additional primary disorders; use of the albumin-corrected anion gap to generate a differential diagnosis for patients with metabolic acidosis; screening for mixed disorders with the delta-delta formula; recognizing the limits of compensation; use of the anion gap to identify 'hidden' acidosis; and the importance of using information from the history and physical examination to identify the specific cause of a patient's acid-base disturbance.

Blood lactate monitoring in critically ill patients: a systematic health technology assessment

OBJECTIVE

To decide whether the use of blood lactate monitoring in critical care practice is appropriate. We performed a systematic health technology assessment as blood lactate monitoring has been implemented widely but its clinical value in critically ill patients has never been evaluated properly.

DATA SOURCE

PubMed, other databases, and citation review.

STUDY SELECTION

We searched for lactate combined with critically ill patients as the target patient population. Two reviewers independently selected studies based on relevance for the following questions: Does lactate measurement: 1) perform well in a laboratory setting? 2) provide information in a number of clinical situations? 3) relate to metabolic acidosis? 4) increase workers' confidence? 5) alter therapeutic decisions? 6) result in benefit to patients? 7) result in similar benefits in your own setting? 8) result in benefits which are worth the extra costs?

DATA EXTRACTION AND SYNTHESIS

We concluded that blood lactate measurement in critically ill patients: 1) is accurate in terms of measurement technique but adequate understanding of the (an)aerobic etiology is required for its correct interpretation; 2) provides not only diagnostic but also important prognostic information; 3) should be measured directly instead of estimated from other acid-base variables; 4) has an unknown effect on healthcare workers' confidence; 5) can alter therapeutic decisions; 6) could potentially improve patient outcome when combined with a treatment algorithm to optimize oxygen delivery, but this has only been shown indirectly; 7) is likely to have similar benefits in critical care settings worldwide; and 8) has an unknown cost-effectiveness.

CONCLUSIONS

The use of blood lactate monitoring has a place in risk-stratification in critically ill patients, but it is unknown whether the routine use of lactate as a resuscitation end point improves outcome. This warrants randomized controlled studies on the efficacy of lactate-directed therapy.

Serum anion gap in metabolic acidosis

METABOLIC ACIDOSIS, DEFINED AS A pathophysiologic state characterized by an arterial pH <7.35 in the absence of an elevated partial pressure of carbon dioxide in arterial blood (PaCO2), is a common finding in the critically ill neonate. It is the result of excess acid production, decreased renal excretion of acid, or increased loss of base.1,2In the neonatal period, metabolic acidosis is most often the result of shock or severe liver or kidney failure. In rare cases, however, it may be a discrete finding suggestive of an inborn error affecting acid production or renal acid excretion.3Left untreated, this acidosis can disturb many cell functions, potentially resulting in respiratory distress, pulmonary vasoconstriction, right ventricular dysfunction, tachycardia, myocardial depression, increased intracranial pressure, hyperkalemia, insulin resistance, decreased affinity of oxygen for hemoglobin, abdominal distention, or vomiting.4Although the most common treatment for acidosis is to “correct” it with bicarbonate (HCO3−), this therapy is not without its potential adverse effects. Therefore, correction of the underlying cause is considered to be the most important therapeutic measure in the management of metabolic acidosis.3,5Calculation of the anion gap is a useful and inexpensive tool with which to develop a differential diagnosis for metabolic acidosis in the neonate. This column examines the usefulness and limitations of calculating the serum anion gap.

Evidence-based medicine in equine critical care

One of the fundamental skills required for practicing evidence-based medicine is the development of a well-built clinical question, which specifies the patient group or problem, intervention, and outcome of interest. For this purpose, various "levels of evidence" have been developed in the human literature, which rank the validity of evidence. Our established conclusions and advice are thus supported by specific "grades of recommendations," which are intended to give an indication of the "strength" of a clinical recommendation. This article was compiled with these principles in mind.

Methanol toxicity in a newborn

BACKGROUND

Methanol poisoning during human pregnancy rarely has been described. We report the first human newborn with a documented methanol concentration resulting from maternal exposure.

CASE REPORT

A 28-year-old pregnant woman EGA 30 weeks with HIV infection and asthma presented to the emergency department in respiratory distress. She was acidotic (pH 7.17) with an anion gap of 26, and fetal bradycardia was noted. Her son was delivered by emergent C-section (birthweight 950 g, Apgars 1 and 3) and required aggressive resuscitation. During his hospital course, acidosis (initial pH 6.9) persisted despite fluid, blood, and bicarbonate administration. His mother also had persistent metabolic acidosis despite fluids, bicarbonate, and dopamine. Results of other laboratory tests on the mother included undetectable ethanol and salicylates and an osmolar gap of 41. An ethanol drip was initiated for the mother 36 h after admission when a methanol level of 54 mg/dL was reported. When consulted on hospital day 3, our regional poison center recommended hemodialysis for the mother and administering fomepizole and testing the methanol level of the newborn (61.6 mg/dL). Because the infant developed a grade 4 intraventricular bleed, no further therapy was offered, and he died on day 4. His mother died on day 10.

CONCLUSION

Fatal neonatal methanol toxicity can result from transplacental exposure.

Risk Factors and Prognostic Variables for Survival of Foals with Radiographic Evidence of Pulmonary Disease

The medical records of 163 neonatal foals that had thoracic radiographs taken within 48 hours of admission to a referral hospital were reviewed. The objectives of this study were (1) to identify risk factors for the development of thoracic radiographic changes and (2) to identify prognostic indicators for survival in foals with radiographic evidence of pulmonary disease. Failure of transfer of passive immunity (IgG concentration < or = 400 mg/dL) was the only risk factor for radiographic evidence of respiratory disease identified by multivariate analysis. Hypoxemic patients (PaO2 < or = 60 mm Hg) were 4.9 times more likely to reveal radiographic abnormalities in a subset of foals for which arterial blood gas results were available. Foals with a serum creatinine concentration > 1.7 mg/dL upon presentation, dyspnea, and a history of dystocia were significantly more likely to die based on the multivariate statistical outcome analysis. An anion gap > or = 20 mEq/dL was strongly associated with nonsurvival in a subset of foals with arterial blood gas results. These hematologic and biochemical variables can be readily obtained during the initial evaluation of sick foals. The presence of a high anion gap appeared to have the greatest clinical impact and may be a useful prognostic indicator in foals with radiographic evidence of respiratory disease. In contrast, the majority of physical examination variables, including evaluation of tachypnea, abnormal respiratory sounds, fever, weakness, and milk reflux from the nares, which are usually obtained during the general respiratory evaluation of foals, were unrelated to outcome.

Serum bicarbonate concentration correlates with arterial base deficit in critically ill patients

BACKGROUND

Base deficit (BD) and lactate concentration have been established as endpoints of resuscitation (EOR) in critically ill patients. However, obtaining these data has traditionally required an arterial blood gas (ABG) sample. We hypothesized that the more easily available serum bicarbonate (SB) concentration could approximate BD and potentially serve as a useful EOR of critically ill or septic patients. We evaluated retrospectively the correlation of SB with BD in a cohort of surgical intensive care unit patients.

MATERIALS AND METHODS

Clinical data from April 1996 through April 1998 were recorded in a computerized application from 1,712 critically ill adult patients. The data were downloaded daily and imported into a relational database for storage and analysis. A subset of paired SB and ABG samples obtained simultaneously was analyzed by linear regression to determine the correlation coefficients (r) and coefficient of determinations (r(2)) for the respective analyses.

RESULTS

A total of 26,690 BD and 16,737 SB determinations were available in the database. Of these, 5,301 BD and SB samples were drawn simultaneously on the same patient. The correlation coefficient for these data pairs was 0.91, and the coefficient of determination was 0.83. The base deficit was predicted by the equation: BD = 22.43 - (0.9522 x SB) (p < 0.0001).

CONCLUSION

In this large data set, there was a close inverse correlation between SB and BD in critically ill or septic patients. The predictive equation explains 83% of the variability for BD values. A prospective study comparing SB to BD and lactate could confirm SB as a useful marker of resuscitation.