A quantitative analysis of the acidosis of cardiac arrest: a prospective observational study

The relationship between serum anion gap levels and short-, medium-, and long-term all-cause mortality in ICU patients with congestive heart failure: a retrospective cohort study

BACKGROUND

There hasn't been research done on the connection between serum anion gap (AG) levels and long-, medium-, and short-term all-cause mortality in congestive heart failure (CHF) patients. This study aims to investigate the association between serum anion gap levels and all-cause mortality in CHF patients after adjusting for other covariates.

METHODS

For each patient, we gather demographic information, comorbidities, laboratory results, vital signs, and scoring data using the ICU (Intensive Care Unit) Admission Scoring System from the MIMIC-III database. The connection between baseline AG and long-, medium-, and short-term all-cause mortality in critically ill congestive heart failure patients was investigated using Kaplan-Meier survival curves, subgroup analysis, restricted cubic spline, and Cox proportional risk analysis.

RESULTS

4840 patients with congestive heart failure in total were included in this study. With a mean age of 72.5 years, these patients had a gender split of 2567 males and 2273 females. After adjusting for other covariates, a multiple regression analysis revealed that, in critically ill patients with congestive heart failure, all-cause mortality increased significantly with rising AG levels. In the fully adjusted model, we discovered that AG levels were strongly correlated with 4-year, 365-day, 90-day, and 30-day all-cause mortality in congestive heart failure patients with HRs (95% CI) of 1.06 (1.04, 1.08); 1.08 (1.05, 1.10); and 1.08 (1.05, 1.11) (p-value < 0.05). Our subgroup analysis's findings demonstrated a high level of consistency and reliability. K-M survival curves demonstrate that high serum AG levels are associated with a lower survival probability.

CONCLUSION

Our research showed the association between CHF patients' all-cause mortality and anion gap levels was non-linear. Elevated anion gap levels are associated with an increased risk of long-, medium-, and short-term all-cause death in patients with congestive heart failure. Continuous monitoring of changes in AG levels may have a clinical predictive role.

Physiology-Guided Resuscitation: Monitoring and Augmenting Perfusion during Cardiopulmonary Arrest

Given the high morbidity and mortality associated with cardiopulmonary arrest, there have been multiple trials aimed at better monitoring and augmenting coronary, cerebral, and systemic perfusion. This article aims to elucidate these interventions, first by detailing the physiology of cardiopulmonary resuscitation and the available tools for managing cardiopulmonary arrest, followed by an in-depth examination of the newest advances in the monitoring and delivery of advanced cardiac life support.

Intra-arrest blood-based biomarkers for out-of-hospital cardiac arrest: A scoping review

Objective

Blood-based biomarkers play a central role in the diagnosis and treatment of critically ill patients, yet none are routinely measured during the intra-arrest phase of out-of-hospital cardiac arrest (OHCA). Our objective was to describe methodological aspects, sources of evidence, and gaps in research surrounding intra-arrest blood-based biomarkers for OHCA.

Methods

We used scoping review methodology to summarize existing literature. The protocol was designed a priori following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. Inclusion criteria were peer-reviewed scientific studies on OHCA patients with at least one blood draw intra-arrest. We excluded in-hospital cardiac arrest and animal studies. There were no language, date, or study design exclusions. We conducted an electronic literature search using PubMed and Embase and hand-searched secondary literature. Data charting/synthesis were performed in duplicate using standardized data extraction templates.

Results

The search strategy identified 11,834 records, with 118 studies evaluating 105 blood-based biomarkers included. Only eight studies (7%) had complete reporting. The median number of studies per biomarker was 2 (interquartile range 1-4). Most studies were conducted in Asia (63 studies, 53%).  Only 22 studies (19%) had blood samples collected in the prehospital setting, and only six studies (5%) had samples collected by paramedics. Pediatric patients were included in only three studies (3%). Out of eight predefined biomarker categories of use, only two were routinely assessed: prognostic (97/105, 92%) and diagnostic (61/105, 58%).

Conclusions

Despite a large body of literature on intra-arrest blood-based biomarkers for OHCA, gaps in methodology and knowledge are widespread.

Phosphate toxicity and SERCA2a dysfunction in sudden cardiac arrest

Almost half of the people who die from sudden cardiac arrest have no detectable heart disease. Among children and young adults, the cause of approximately one-third of deaths from sudden cardiac arrest remains unexplained after thorough examination. Sudden cardiac arrest and related sudden cardiac death are attributed to dysfunctional cardiac ion-channels. The present perspective paper proposes a pathophysiological mechanism by which phosphate toxicity from cellular accumulation of dysregulated inorganic phosphate interferes with normal calcium handling in the heart, leading to sudden cardiac arrest. During cardiac muscle relaxation following contraction, SERCA2a pumps actively transport calcium ions into the sarcoplasmic reticulum, powered by ATP hydrolysis that produces ADP and inorganic phosphate end products. Reviewed evidence supports the proposal that end-product inhibition of SERCA2a occurs as increasing levels of inorganic phosphate drive up phosphate toxicity and bring cardiac function to a sudden and unexpected halt. The paper concludes that end-product inhibition from ATP hydrolysis is the mediating factor in the association of sudden cardiac arrest with phosphate toxicity. However, current technology lacks the ability to directly measure this pathophysiological mechanism in active myocardium, and further research is needed to confirm phosphate toxicity as a risk factor in individuals with sudden cardiac arrest. Moreover, phosphate toxicity may be reduced through modification of dietary phosphate intake, with potential for employing low-phosphate dietary interventions to reduce the risk of sudden cardiac arrest.

Lactate versus Phosphate as Biomarkers to Aid Mechanical Circulatory Support Decisions in Patients with Out-of-Hospital Cardiac Arrest and Return of Spontaneous Circulation

AIMS

Identifying patients who may benefit from mechanical circulatory support (MCS) after out-of-hospital cardiac arrest (OHCA) and return of spontaneous circulation (ROSC) remains challenging; thus, a search for helpful biomarkers is warranted. We aimed to evaluate phosphate and lactate levels on admission regarding their associations with survival with and without MCS.

METHODS

In 224 OHCA patients who achieved ROSC, the initial phosphate and lactate levels were investigated to discriminate in-hospital mortality by receiver operating characteristic (ROC) curves. According to the Youden Index (YI) from the respective ROC, the groups were risk stratified by both biomarkers, and 30-day mortality was analyzed in patients with and without MCS.

RESULTS

Within the entire collective, MCS was not associated with a better chance of survival. Both phosphate and lactate level elevations showed good yet comparable discriminations to predict mortality (areas under the curve: 0.80 vs. 0.79, p = 0.74). In patients with initial phosphate values > 2.2 mmol/L (>YI), 30-day mortality within the MCS cohort was lower (HR 2.3, 95% CI: 1.4-3.7; p = 0.0037). In patients with lower phosphate levels and groups stratified by lactate, 30-day mortality was similar in patients with and without MCS.

CONCLUSIONS

We found a significant association between survival and MCS therapy in patients with phosphate levels above 2.2 mmol/L (Youden Index), and a similar discrimination of patient overall survival by lactate and phosphate. Prospective studies should assess the possible independent prognostic value of phosphate and its clearance for MCS efficiency.

Elevated Initial Serum Phosphate Levels Predict Higher Mortality and Impaired Neurological Outcome in Cardiac Arrest Patients with Return of Spontaneous Circulation

Purpose: Although a moderate proportion of cardiac arrest (CA) patients achieve a return of spontaneous circulation (ROSC), few survive to discharge, mostly with poor neurological development. As serum phosphate levels were described as elevated after cardiopulmonary resuscitation (CPR), we asked whether these elevations would predict a higher risk of mortality and impaired neurological outcome in CA patients following ROSC. Methods: Initial serum phosphate levels, survival, and neurologic status at discharge of 488 non-traumatic CA patients treated at a single German hospital after achieving ROSC were analyzed. The cut-off value of phosphate for mortality prediction was determined using the receiver operator characteristic (ROC) curve, and patients were divided accordingly for comparison. Results were validated by analyzing phosphate levels in a multi-centric cohort containing 3299 CA patients from the eICU database of the United States. Results: In the German cohort, ROC analysis showed a 90% specificity for phosphate levels >2.7 mmol/L to predict mortality (AUC: 0.76, p < 0.0001), and phosphate level elevations were associated with higher in-hospital mortality (crude odds ratio 3.04, 95% CI 2.32 to 4.08). Patients with initial phosphate levels >2.7 mmol/L had significantly higher mortality in both analyzed collectives (p < 0.0001). Similarly, patients from the German cohort who initially had higher phosphate levels also showed a higher proportion of impaired neurological status at discharge and morphological signs of brain injury. Conclusions: In CA patients following ROSC, initial serum phosphate levels >2.7 mmol/L predict higher mortality and impaired neurological outcome. Our data suggests that phosphate determination might improve the preciseness of the overall and neurologic prognostication in patients after CPR following ROSC.

Relationship of Admission Serum Anion Gap and Prognosis of Critically Ill Patients: A Large Multicenter Cohort Study

Background

There were controversies over the relationship between Anion gap (AG) and mortality in critically ill patients. Therefore, a large multicenter cohort study was conducted to evaluate the association of AG and mortality in large-scale intensive care units (ICUs) patients.

Methods

This retrospective cohort study included adult ICU patients enrolled from eICU Collaborative Research Database. According to initial serum AG upon ICU admission, patients were divided into three groups: AG < 8 mmol/L, 8 ≤ AG ≤ 16 mmol/L, and AG > 16 mmol/L. Logistic regression models were built to investigate the association between serum AG and ICU and hospital mortalities. Serum AG was added into Acute Physiology and Chronic Health Evaluation (APACHE) IV score and the model discrimination was assessed by the area under the curve (AUC) of receiver operating characteristic curves. The relationship between serum AG and mortalities in patients with different acid-base status and serum lactate were also evaluated. An external validation was performed with the Critical care database comprising patients with infection at Zigong Fourth People's Hospital.

Results

A total of 8520 patients entered the final cohort. There are 42 patients with serum AG < 8 mmol/L, 3238 patients with 8 ≤ AG ≤ 16 mmol/L, and 5240 patients with AG > 16 mmol/L. Serum AG > 16 mmol/L is related with increased ICU mortality (odds ratio [OR], 1.530; 95% confidence interval [CI], 1.305-1.794) and hospital mortality (OR, 1.618; 95% CI, 1.415-1.849), compared with 8 ≤ AG ≤ 16 mmol/L. Adding Serum AG to APACHE IV score could statistically improve the prediction of ICU (0.770 [0.761-0.779] to 0.774 [0.765-0.783], P = 0.001) and hospital mortalities (0.756 [0.747-0.765] to 0.761 [0.751-0.770], P = 0.012). The associations between serum AG and mortalities remain robust in patients with different acid-base statuses and serum lactate. The findings are validated in the external cohort.

Conclusions

Initial serum AG > 16 mmol/L after ICU admission is associated with increased mortality in critically ill patients.

Incidence, characteristics and predictors of mortality following cardiac arrest in ICUs of a German university hospital: A retrospective cohort study

BACKGROUND

Cardiac arrest in intensive care is a rarely studied type of in-hospital cardiac arrest.

OBJECTIVE

This study examines the incidence, characteristics, risk factors for mortality as well as long-term prognosis following cardiac arrest in intensive care.

DESIGN

Retrospective cohort study.

SETTING

Five noncardiac surgical ICUs (41 surgical and 37 medical beds) at a German university hospital between 2016 and 2019.

PATIENTS

Adults experiencing cardiac arrest defined as the need for chest compressions and/or defibrillation occurring for the first time on the ICU.

MAIN OUTCOME MEASURES

Primary endpoint: occurrence of cardiac-arrest in the ICU. Secondary endpoints: diagnostic and therapeutic measures; risk factors and marginal probabilities of no-return of spontaneous circulation; rates of return of spontaneous circulation, hospital discharge, 1-year-survival and 1-year-neurological outcome.

RESULTS

A total of 114 cardiac arrests were observed out of 14 264 ICU admissions; incidence 0.8%; 95% confidence interval (CI) 0.7 to 1.0; 45.6% received at least one additional diagnostic test, such as blood gas analysis (36%), echocardiography (19.3%) or chest x-ray (9.9%) with a resulting change in therapy in 52%, (more frequently in those with a return of spontaneous circulation vs none, P = 0.023). Risk factors for no-return of spontaneous circulation were cardiac comorbidities (OR 5.4; 95% CI, 1.4 to 20.7) and continuous renal replacement therapy (OR 5.9; 95% CI, 1.7 to 20.8). Bicarbonate levels greater than 21 mmol l-1 were associated with a higher mortality risk in combination either with cardiac comorbidities (bicarbonate <21 mmol l-1: 13%; 21 to 26 mmol l-1: 45%; >26 mmol l-1: 42%) or with a SOFA at least 2 (bicarbonate <21 mmol l-1: 8%; 21 to 26 mmol l-1: 40%; >26 mmol l-1: 37%). In-hospital mortality was 78.1% (n=89); 1-year-survival-rate was 10.5% (95% CI, 5.5 to 17.7) and survival with a good neurological outcome was 6.1% (95% CI, 2.5 to 12.2).

CONCLUSION

Cardiac arrest in ICU is a rare complication with a high mortality and low rate of good neurological outcome. The development of a structured approach to resuscitation should include all available resources of an ICU and adequately consider the complete diagnostic and therapeutic spectra as our results indicate that these are still underused. The development of prediction models of death should take into account cardiac and hepatic comorbidities, continuous renal replacement therapy, SOFA at least 2 before cardiac arrest and bicarbonate level. Further research should concentrate on identifying early predictors and on the prevention of cardiac arrest in ICU.

Sublingual microcirculation predicts survival after out-of-hospital cardiac arrest

BACKGROUND

Despite successful resuscitation with return of spontaneous circulation (ROSC), the prediction of survival in patients suffering out-of-hospital cardiac arrest (OHCA) remains difficult. Several studies have shown alterations in sublingual microcirculation in the critical ill. We hypothesized that early alterations in sublingual microcirculation may predict short-term survival after OHCA.

METHODS

We prospectively included all adults admitted to our university hospital between April and September 2019 with ROSC following OHCA. Sidestream dark-field microscopy to obtain sublingual microcirculation was performed at admission and after 6, 12 and 24 hours. Primary outcome was survival until discharge.

RESULTS

Twenty-five patients were included. Six hours after ROSC, the proportion of perfused small vessels (PPV_small ) was lower in non-survivors than in survivors (85 ± 7.9 vs. 75 ± 6.6%; p = .01). PPV_small did not correlate with serum lactate. Stratification for survival with cutoff values >78.4% for PPV_small 6 h post-admission and <5.15 mmol/l for initial serum lactate as suggested by ROC-Analyses results in a positive predictive value of 100% and a negative one of 67% for our study population.

CONCLUSION

Estimating short-term prognosis of OHCA patients with ROSC may be supported by measuring the PPV_small at the sublingual microcirculation 6 hours after admission.

Proton Quantum Tunneling: Influence and Relevance to Acidosis-Induced Cardiac Arrhythmias/Cardiac Arrest

Acidosis and its associated pathologies predispose patients to develop cardiac arrhythmias and even cardiac arrest. These arrhythmias are assumed to be the result of membrane depolarization, however, the exact mechanism of depolarization during acidosis is not well defined. In our study, the model of quantum tunneling of protons is used to explain the membrane depolarization that occurs during acidosis. It is found that protons can tunnel through closed activation and inactivation gates of voltage-gated sodium channels Nav1.5 that are present in the membrane of cardiac cells. The quantum tunneling of protons results in quantum conductance, which is evaluated to assess its effect on membrane potential. The quantum conductance of extracellular protons is higher than that of intracellular protons. This predicts an inward quantum current of protons through the closed sodium channels. Additionally, the values of quantum conductance are influential and can depolarize the membrane potential according to the quantum version of the GHK equation. The quantum mechanism of depolarization is distinct from other mechanisms because the quantum model suggests that protons can directly depolarize the membrane potential, and not only through indirect effects as proposed by other mechanisms in the literature. Understanding the pathophysiology of arrhythmias mediated by depolarization during acidosis is crucial to treat and control them and to improve the overall clinical outcomes of patients.

Associations between initial serum pH value and outcomes of pediatric out-of-hospital cardiac arrest

INTRODUCTION

Pediatric out-of-hospital cardiac arrest (OHCA) is one of the most critical conditions seen in the emergency department (ED). Although initial serum pH value is reported to be associated with outcome in adult OHCA patients, the association is unclear in pediatric OHCA patients. Thus, we aimed to identify the association between initial pH value and outcome among pediatric OHCA patients.

METHODS

This study was a retrospective analysis of a multicenter prospective cohort registry (Japanese Association for Acute Medicine out-of-hospital cardiac arrest registry) from 87 hospitals in Japan. We included pediatric OHCA patients younger than 16 years of age who were registered in this registry between June 2014 and December 2017. Of the 34,754 patients in the database, 458 patients were ultimately included in the analysis. We equally divided the patients into four groups, based on their initial pH value, and conducted a multivariate logistic regression analysis to calculate the adjusted odds ratios of the initial pH value on hospital arrival with their 95% confidence intervals for the primary outcome.

RESULTS

The median (interquartile range) age was 1 (0-6) year, and 77.9% (357/458) of the first monitored rhythm was asystole. The primary outcome was 1-month survival. The overall 1-month survival was 13.3% (61/458), and a 1-month favorable neurologic outcome was seen in 5.2% (24/458) of cases. The adjusted odds ratios and 95% confidence intervals for the pH 6.81-6.64, pH 6.63-6.47, pH <6.47, and pH unknown groups compared with the pH ≥6.82 group for 1-month survival were 0.39 (0.16-0.97), 0.13 (0.04-0.44), 0.03 (0.00-0.24), and 0.07 (0.02-0.21), respectively.

CONCLUSIONS

This study demonstrated the association between the initial pH value on hospital arrival and 1-month survival among pediatric OHCA patients.

Cardiac arrest and drug-related cardiac toxicity in the Covid-19 era. Epidemiology, pathophysiology and management

SARS-CoV-2 (Covid-19) infection has recently become a worldwide challenge with dramatic global economic and health consequences. As the pandemic is still spreading, new data concerning Covid-19 complications and related mechanisms become increasingly available. Accumulating data suggest that the incidence of cardiac arrest and its outcome are adversely affected during the Covid-19 period. This may be further exacerbated by drug-related cardiac toxicity of Covid-19 treatment regimens. Elucidating the underlying mechanisms that lead to Covid-19 associated cardiac arrest is imperative, not only in order to improve its effective management but also to maximize preventive measures. Herein we discuss available epidemiological data on cardiac arrest during the Covid-19 pandemic as well as possible associated causes and pathophysiological mechanisms and highlight gaps in evidence warranting further investigation. The risk of transmission during cardiopulmonary resuscitation (CPR) is also discussed in this review. Finally, we summarize currently recommended guidelines on CPR for Covid-19 patients including CPR in patients with cardiac arrest due to suspected drug-related cardiac toxicity in an effort to underscore the most important common points and discuss discrepancies proposed by established international societies.

Do not disregard the initial 12 lead ECG after out-of-hospital cardiac arrest: It predicts angiographic culprit despite metabolic abnormalities

Objectives

The initial 12 lead electrocardiogram (ECG) following return of spontaneous circulation (ROSC) after out-of-hospital cardiac arrest (OHCA), is often disregarded by clinicians in ability to predict acute thrombotic coronary occlusion (ATCO) due to markedly abnormal metabolic milieu (AMM). We sought to evaluate the accuracy of initial vs. follow-up ECG prior to invasive coronary angiography (ICA) to predict ATCO following resuscitated OHCA.

Methods

We included OHCA patients with initial shockable rhythm who underwent invasive coronary angiography (ICA). AMM was defined as one of: pH ​< ​7.1, lactate >2 ​mmol/L, serum potassium <2.8 or >6.0 mEq/L. Two ECGs A (initial) and B (follow-up) following ROSC but prior to ICA were adjudicated by 2 experienced readers using expanded ECG criteria to predict angiographic ATCO on ICA.

Results

152 consecutive patients (mean age 58 years, 75% male) met inclusion criteria, 77% had AMM. Among those with both ECGs (n ​= ​102), overall accuracy, sensitivity, specificity, positive predictive value, negative predictive value for correctly predicting angiographic ATCO for ECG A was 72%, 63%, 81%, 61%, 83% and for ECG B was 71%, 50%, 91%, 73%, 80% respectively. Predictive accuracy for angiographic ATCO was similar between ECG A [odds ratio (OR) 7.31, CI 2.87–18.62, p ​< ​0.0001) and ECG B [OR 10.67; CI 3.6–31.61, p ​< ​0.0001], and consistent in AMM.

Conclusions

In OHCA, despite AMM, the initial post ROSC ECG retains a statistically significant, and similar accuracy as the follow-up ECG to predict angiographic ATCO using expanded criteria.

Fatal Rattlesnake Envenomation in Northernmost Brazilian Amazon: A Case Report and Literature Overview

Snakebite envenomations are classified as Category A Neglected Tropical Diseases by the World Health Organization. In Brazil, 405 snake species are distributed among 11 families, with the genera Bothrops and Crotalus being the most studied and main responsible for severe and lethal envenomations. In the country, Crotalus genus (i.e., rattlesnakes) is represented by Crotalus durissus species, showing seven different subspecies distributed along the country, including Crotalus durissus ruruima, which inhabits Roraima, the Brazilian nothermost state from Amazon forest. Here, we report a fatal case of a severe envenomation following a rattlesnake bite. The patient presented classic crotalic neurological signs and symptoms such as ptosis, drooling of saliva, sluggishness, macroscopic hematuria, and oliguria, which evolved to acute kidney failure (AKF) and hemodynamic instability. Although the patient was treated with the specific antivenom therapy, the severe envenomation resulted in three cardiac arrests and death of the victim in less than 38 h. This study discusses the causes of the patient death, the features of rattlesnake venom-induced AKF, and shows evidences that the Brazilian crotalic antivenom should be improved to treat rattlesnake envenomations caused by C. d. ruruima venom in Roraima state.

Prognostic value of the delta neutrophil index in pediatric cardiac arrest

The delta neutrophil index (DNI), which reflects the ratio of circulating immature neutrophils, has been reported to be highly predictive of mortality in systemic inflammation. We investigated the prognostic significance of DNI value for early mortality and neurologic outcomes after pediatric cardiac arrest (CA). We retrospectively analyzed the data of eligible patients (<19 years in age). Among 85 patients, 55 subjects (64.7%) survived and 36 (42.4%) showed good outcomes at 30 days after CA. Cox regression analysis revealed that the DNI values immediately after the return of spontaneous circulation, at 24 hours and 48 hours after CA, were related to an increased risk for death within 30 days after CA (P < 0.001). A DNI value of higher than 3.3% at 24 hours could significantly predict both 30-day mortality (hazard ratio: 11.8; P < 0.001) and neurologic outcomes (odds ratio: 8.04; P = 0.003). The C statistic for multivariable prediction models for 30-day mortality (incorporating DNI at 24 hours, compression time, and serum sodium level) was 0.799, and the area under the receiver operating characteristic curve of DNI at 24 hours for poor neurologic outcome was 0.871. Higher DNI was independently associated with 30-day mortality and poor neurologic outcomes after pediatric CA.

Initial arterial pH as a predictor of neurologic outcome after out-of-hospital cardiac arrest: A propensity-adjusted analysis

BACKGROUND

Lower pH after out-of-hospital cardiac arrest (OHCA) has been associated with worsening neurologic outcome, with <7.2 identified as an "unfavorable resuscitation feature" in consensus treatment algorithms despite conflicting data. This study aimed to describe the relationship between decremental post-resuscitation pH and neurologic outcomes after OHCA.

METHODS

Consecutive OHCA patients treated with targeted temperature management (TTM) at multiple US centers from 2008 to 2017 were evaluated. Poor neurologic outcome at hospital discharge was defined as cerebral performance category ≥3. The exposure was initial arterial pH after return of spontaneous circulation (ROSC) analyzed in decremental 0.05 thresholds. Potential confounders (demographics, history, resuscitation characteristics, initial studies) were defined a priori and controlled for via ATT-weighting on the inverse propensity score plus direct adjustment for the linear propensity score.

RESULTS

Of 723 patients, 589 (80%) experienced poor neurologic outcome at hospital discharge. After propensity-adjustment with excellent covariate balance, the adjusted odds ratios for poor neurologic outcome by pH threshold were: ≤7.3: 2.0 (1.0-4.0); ≤7.25: 1.9 (1.2-3.1); ≤7.2: 2.1 (1.3-3.3); ≤7.15: 1.9 (1.2-3.1); ≤7.1: 2.4 (1.4-4.1); ≤7.05: 3.1 (1.5-6.3); ≤7.0: 4.5 (1.8-12).

CONCLUSIONS

No increased hazard of progressively poor neurologic outcomes was observed in resuscitated OHCA patients treated with TTM until the initial post-ROSC arterial pH was at least ≤7.1. This threshold is more acidic than in current guidelines, suggesting the possibility that post-arrest pH may be utilized presently as an inappropriately-pessimistic prognosticator.

Severe metabolic acidosis after out-of-hospital cardiac arrest: risk factors and association with outcome

BACKGROUND

Metabolic acidosis is frequently observed as a consequence of global ischemia-reperfusion after out-of-hospital cardiac arrest (OHCA). We aimed to identify risk factors and assess the impact of metabolic acidosis on outcome after OHCA.

METHODS

We included all consecutive OHCA patients admitted between 2007 and 2012. Using admission data, metabolic acidosis was defined by a positive base deficit and was categorized by quartiles. Main outcome was survival at ICU discharge. Factors associated with acidosis severity and with main outcome were evaluated by linear and logistic regressions, respectively.

RESULTS

A total of 826 patients (68.3% male, median age 61 years) were included in the analysis. Median base deficit was 8.8 [5.3, 13.2] mEq/l. Male gender (p = 0.002), resuscitation duration (p < 0.001), initial shockable rhythm (p < 0.001) and post-resuscitation shock (p < 0.001) were associated with an increased level of acidosis. ICU mortality rate increased across base deficit quartiles (39.1, 59.2, 76.3 and 88.3%, p for trend < 0.001), and base deficit was independently associated with ICU mortality (p < 0.001). The proportion of CPC 1 patients among ICU survivors was similar across base deficit quartiles (72.8, 67.1, 70.5 and 62.5%, p = 0.21), and 7.3% of patients with a base deficit higher than 13.2 mEq/l survived to ICU discharge with complete neurological recovery.

CONCLUSION

Severe metabolic acidosis is frequent in OHCA patients and is associated with poorer outcome, in particular due to refractory shock. However, we observed that about 7% of patients with a very severe metabolic acidosis survived to ICU discharge with complete neurological recovery.

Metabolic acidosis and the role of unmeasured anions in critical illness and injury

Acid-base disorders are frequently present in critically ill patients. Metabolic acidosis is associated with increased mortality, but it is unclear whether as a marker of the severity of the disease process or as a direct effector. The understanding of the metabolic component of acid-base derangements has evolved over time, and several theories and models for precise quantification and interpretation have been postulated during the last century. Unmeasured anions are the footprints of dissociated fixed acids and may be responsible for a significant component of metabolic acidosis. Their nature, origin, and prognostic value are incompletely understood. This review provides a historical overview of how the understanding of the metabolic component of acid-base disorders has evolved over time and describes the theoretical models and their corresponding tools applicable to clinical practice, with an emphasis on the role of unmeasured anions in general and several specific settings.

Enhanced pyruvate dehydrogenase activity improves cardiac outcomes in a murine model of cardiac arrest

Rationale

Post-ischemic changes in cellular metabolism alter myocardial and neurological function. Pyruvate dehydrogenase (PDH), the limiting step in mitochondrial glucose oxidation, is inhibited by increased expression of PDH kinase (PDK) during ischemia/reperfusion injury. This results in decreased utilization of glucose to generate cellular ATP. Post-cardiac arrest (CA) hypothermia improves outcomes and alters metabolism, but its influence on PDH and PDK activity following CA are unknown. We hypothesized that therapeutic hypothermia (TH) following CA is associated with the inhibition of PDK activity and increased PDH activity. We further hypothesized that an inhibitor of PDK activity, dichloroacetate (DCA), would improve PDH activity and post-CA outcomes.

Methods and results

Anesthetized and ventilated adult female C57BL/6 wild-type mice underwent a 12-minute KCl-induced CA followed by cardiopulmonary resuscitation. Compared to normothermic (37°C) CA controls, administering TH (30°C) improved overall survival (72-hour survival rate: 62.5% vs. 28.6%, P<0.001), post-resuscitation myocardial function (ejection fraction: 50.9±3.1% vs. 27.2±2.0%, P<0.001; aorta systolic pressure: 132.7±7.3 vs. 72.3±3.0 mmHg, P<0.001), and neurological scores at 72-hour post CA (9.5±1.3 vs. 5.4±1.3, P<0.05). In both heart and brain, CA increased lactate concentrations (1.9-fold and 3.1-fold increase, respectively, P<0.01), decreased PDH enzyme activity (24% and 50% reduction, respectively, P<0.01), and increased PDK protein expressions (1.2-fold and 1.9-fold, respectively, P<0.01). In contrast, post-CA treatment with TH normalized lactate concentrations (P<0.01 and P<0.05) and PDK expressions (P<0.001 and P<0.05), while increasing PDH activity (P<0.01 and P<0.01) in both the heart and brain. Additionally, treatment with DCA (0.2 mg/g body weight) 30 min prior to CA improved both myocardial hemodynamics 2 hours post-CA (aortic systolic pressure: 123±3 vs. 96±4 mmHg, P<0.001) and 72-hour survival rates (50% vs. 19%, P<0.05) in normothermic animals.

Conclusions

Enhanced PDH activity in the setting of TH or DCA administration is associated with improved post-CA resuscitation outcomes. PDH is a promising therapeutic target for improving post-CA outcomes.

Therapeutic Hypothermia Reduces Oxidative Damage and Alters Antioxidant Defenses after Cardiac Arrest

After cardiac arrest, organ damage consequent to ischemia-reperfusion has been attributed to oxidative stress. Mild therapeutic hypothermia has been applied to reduce this damage, and it may reduce oxidative damage as well. This study aimed to compare oxidative damage and antioxidant defenses in patients treated with controlled normothermia versus mild therapeutic hypothermia during postcardiac arrest syndrome. The sample consisted of 31 patients under controlled normothermia (36°C) and 11 patients treated with 24 h mild therapeutic hypothermia (33°C), victims of in- or out-of-hospital cardiac arrest. Parameters were assessed at 6, 12, 36, and 72 h after cardiac arrest in the central venous blood samples. Hypothermic and normothermic patients had similar S100B levels, a biomarker of brain injury. Xanthine oxidase activity is similar between hypothermic and normothermic patients; however, it decreases posthypothermia treatment. Xanthine oxidase activity is positively correlated with lactate and S100B and inversely correlated with pH, calcium, and sodium levels. Hypothermia reduces malondialdehyde and protein carbonyl levels, markers of oxidative damage. Concomitantly, hypothermia increases the activity of erythrocyte antioxidant enzymes superoxide dismutase, glutathione peroxidase, and glutathione S-transferase while decreasing the activity of serum paraoxonase-1. These findings suggest that mild therapeutic hypothermia reduces oxidative damage and alters antioxidant defenses in postcardiac arrest patients.

The Effects of On-Pump and Off-Pump Coronary Artery Bypass Surgery on Metabolic Profiles in the Early Postoperative Period

OBJECTIVE

Hyperlactatemia and base deficit (BD) are markers of adverse outcome after cardiac surgery, and their derangement can be influenced by the use of extracorporeal circulation. The authors hypothesized a better postoperative metabolic profile in off-pump coronary artery bypass grafting (OPCABG) compared with "on-pump" coronary artery bypass grafting (ONCABG).

DESIGN

This was a retrospective study, with consecutive data collected for 1 year from electronic medical records.

SETTING

Cardiothoracic intensive care unit at a tertiary university hospital.

PARTICIPANTS

The study comprised 339 patients who underwent elective coronary artery bypass grafting (ONCABG [n = 215], OPCABG [n = 124]).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The metabolic (arterial lactatemia, pH, and BD) and hemodynamic (inotropic/vasopressor support) parameters of OPCABG and ONCABG patients were compared at 7 predefined time points (intensive care admission and the 1st, 3rd, 6th, 12th, 18th, and 24th postoperative hours). For each output of interest, mixed-effects linear regression models were used (with time as random-effect to allow for clustering of repeated measures) and adjusted for a predetermined set of covariates. Arterial lactatemia and pH were comparable at all time points; BD was worse in the ONCABG group overall (p = 0.01) and at most time points (except at the 1st and 24th postoperative hours). For the whole period, inotropic support was more common in ONCABG patients (p<0.05), whereas vasopressor use was more frequent in the OPCABG group (p< 0.05).

CONCLUSIONS

Improved postoperative BD values were demonstrated in the OPCABG group, although pH and lactatemia were similar between groups. Inotropic support was less common in the OPCABG group at the expense of more frequent vasopressor support.

Severe acidemia on arrival not predictive of neurologic outcomes in post-cardiac arrest patients

PURPOSE

This study aimed to determine whether severe acidemia (pH <7.2) on arrival at the emergency department (ED) is a predictive factor for neurologic outcomes of post-cardiac arrest patients treated with targeted temperature management (TTM).

MATERIALS AND METHODS

Data in the National Disaster Medical Center, a tertiary care hospital, were used to perform a case-control study on post-cardiac arrest patients treated with TTM from January 2013 to April 2015. The case group comprised patients with good neurologic outcomes (cerebral performance categories 1 and 2), whereas the control group comprised patients with poor neurologic outcomes (cerebral performance categories 3-5). Exposure was defined as arterial pH less than 7.2 on arrival at the ED.

RESULTS

We identified 32 patients matching our criteria, of which 13 had good outcomes and 19 poor outcomes. Arterial pH on arrival was not significantly associated with neurologic outcomes (P = .47; odds ratio, 0.5; 95% confidence interval, 0.09-2.61). In 24 patients with cardiogenic causes of cardiac arrest, pH on arrival was not significantly associated with neurologic outcomes (P = .68; odds ratio, 0.5; 95% confidence interval, 0.09-2.73) after matched-pair analysis by age, sex, and presence of light reflex.

CONCLUSION

Severe acidemia on arrival at the ED is not a significant predictive factor for neurologic outcomes in post-cardiac arrest patients treated with TTM, particularly in patients with cardiogenic causes of cardiac arrest. These results suggest that treatment should not be withheld in post-cardiac arrest patients with severe acidemia.

Snake constriction rapidly induces circulatory arrest in rats

As legless predators, snakes are unique in their ability to immobilize and kill their prey through the process of constriction, and yet how this pressure incapacitates and ultimately kills the prey remains unknown. In this study, we examined the cardiovascular function of anesthetized rats before, during and after being constricted by boas (Boa constrictor) to examine the effect of constriction on the prey's circulatory function. The results demonstrate that within 6 s of being constricted, peripheral arterial blood pressure (PBP) at the femoral artery dropped to 1/2 of baseline values while central venous pressure (CVP) increased 6-fold from baseline during the same time. Electrocardiographic recordings from the anesthetized rat's heart revealed profound bradycardia as heart rate (fH) dropped to nearly half of baseline within 60 s of being constricted, and QRS duration nearly doubled over the same time period. By the end of constriction (mean 6.5±1 min), rat PBP dropped 2.9-fold, fH dropped 3.9-fold, systemic perfusion pressure (SPP=PBP−CVP) dropped 5.7-fold, and 91% of rats (10 of 11) had evidence of cardiac electrical dysfunction. Blood drawn immediately after constriction revealed that, relative to baseline, rats were hyperkalemic (serum potassium levels nearly doubled) and acidotic (blood pH dropped from 7.4 to 7.0). These results are the first to document the physiological response of prey to constriction and support the hypothesis that snake constriction induces rapid prey death due to circulatory arrest.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The impact of severe acidemia on neurologic outcome of cardiac arrest survivors undergoing therapeutic hypothermia

INTRODUCTION

Therapeutic Hypothermia (TH) has become a standard of care in improving neurological outcomes in cardiac arrest (CA) survivors. Previous studies have defined severe acidemia as plasma pH<7.20. We investigated the influence of severe acidemia at the time of initiation of TH on neurological outcome in CA survivors.

METHODS

A retrospective analysis was performed on 196 consecutive CA survivors (out-of-hospital CA and in-hospital CA) who underwent TH with endovascular cooling between January 2007 and October 2012. Arterial blood gas drawn prior to initiation of TH was utilized to measure pH in all patients. Shockable and non-shockable CA patients were divided into two sub-groups based on pH (pH<7.2 and pH≥7.2). The primary end-point was measured using the Pittsburgh Cerebral Performance Category (CPC) scale prior to discharge from the hospital: good (CPC 1 and 2) and poor (CPC 3 to 5) neurologic outcome.

RESULTS

Sixty-two percent of shockable CA patients with pH≥7.20 had good neurological outcome as compared to 34% patients with pH<7.20. Shockable CA patients with pH≥7.20 were 3.3 times more likely to have better neurological outcome when compared to those with pH <7.20 [p=0.013, OR 3.3, 95% CI (1.28-8.45)]. In comparison, non-shockable CA patients with p≥7.20 did not have a significantly different neurological outcome as compared to those with pH<7.20 [p=0.97, OR 1.02, 95% CI (0.31-3.3)].

CONCLUSION

Presence of severe acidemia at initiation of TH in shockable CA survivors is significantly associated with poor neurological outcomes. This effect was not observed in the non-shockable CA survivors.

Stewart analysis of apparently normal acid-base state in the critically ill

PURPOSE

This study aimed to describe Stewart parameters in critically ill patients with an apparently normal acid-base state and to determine the incidence of mixed metabolic acid-base disorders in these patients.

MATERIALS AND METHODS

We conducted a prospective, observational multicenter study of 312 consecutive Dutch intensive care unit patients with normal pH (7.35 ≤ pH ≤ 7.45) on days 3 to 5. Apparent (SIDa) and effective strong ion difference (SIDe) and strong ion gap (SIG) were calculated from 3 consecutive arterial blood samples. Multivariate linear regression analysis was performed to analyze factors potentially associated with levels of SIDa and SIG.

RESULTS

A total of 137 patients (44%) were identified with an apparently normal acid-base state (normal pH and -2 < base excess < 2 and 35 < PaCO2 < 45 mm Hg). In this group, SIDa values were 36.6 ± 3.6 mEq/L, resulting from hyperchloremia (109 ± 4.6 mEq/L, sodium-chloride difference 30.0 ± 3.6 mEq/L); SIDe values were 33.5 ± 2.3 mEq/L, resulting from hypoalbuminemia (24.0 ± 6.2 g/L); and SIG values were 3.1 ± 3.1 mEq/L. During admission, base excess increased secondary to a decrease in SIG levels and, subsequently, an increase in SIDa levels. Levels of SIDa were associated with positive cation load, chloride load, and admission SIDa (multivariate r(2) = 0.40, P < .001). Levels of SIG were associated with kidney function, sepsis, and SIG levels at intensive care unit admission (multivariate r(2) = 0.28, P < .001).

CONCLUSIONS

Intensive care unit patients with an apparently normal acid-base state have an underlying mixed metabolic acid-base disorder characterized by acidifying effects of a low SIDa (caused by hyperchloremia) and high SIG combined with the alkalinizing effect of hypoalbuminemia.

Biochemical profile and outcomes in trauma patients subjected to open cardiopulmonary resuscitation: a prospective observational pilot study

BACKGROUND

The predictive factors to regain a heartbeat following emergency department resuscitative thoracotomy (EDT) for trauma are poorly understood. The objective of the present study was to prospectively assess the electrolyte profile, coagulation parameters, and acid-base status from intracardiac blood samples in trauma patients subjected to open cardiopulmonary resuscitation (CPR) in the presence of established cardiac arrest.

METHODS

All patients who underwent EDT following trauma were considered for inclusion. Prior to the injection of any resuscitative medications, a sample of intracardiac blood from the right ventricle was obtained for analysis.

RESULTS

During the study period, a total of 22 patients had intracardiac blood samples obtained and were eligible for analysis. Twelve patients never regained cardiac activity, and 10 patients transiently regained a heartbeat for a mean of 51 ± 69 min, but ultimately died. Some 91 % (20/22) of patients presented with severe acidosis (pH < 7.20). The pCO(2) was <45 mmHg in 68 % (15/22) of patients, and the pO(2) level was >75 mmHg in 77 % (17/22) of patients. Patients who never regained cardiac activity had a significantly higher lactate level than those with a return of cardiac rhythm (17.1 ± 2.6 vs. 10.6 ± 4.9 mmol/L, p = 0.018). The sodium and potassium levels were higher for those who never regained a rhythm than for those who did regain a pulse (sodium: 155 ± 14 vs. 147 ± 9 mmol/L, p = 0.094; potassium: 6.0 ± 1.1 vs. 4.6 ± 1.0 mmol/L, p = 0.014). Severe hyperkalemia (potassium > 5.5 mmol/L) occurred significantly more often in patients who did not regain a heart beat (p = 0.030). Coagulopathy (INR > 1.2 and/or prothrombin time >15 s and/or platelet count <100,000/μL) was noted in 96 % of patients.

CONCLUSIONS

Most patients undergoing open CPR have normal blood gas levels. Severe lactic acidosis, hyperkalemia, and hypernatremia are associated with decreased probability for return of cardiac function. Calcium and magnesium levels were not significantly different between the two groups, making the therapeutic role of these electrolytes very questionable.

High sugar intake exacerbates cardiac reperfusion injury in perinatal taurine depleted adult rats

Perinatal taurine depletion and high sugar diets blunted baroreflex function and heightens sympathetic nerve activity in adult rats. Cardiac ischemia/reperfusion also produces these disorders and taurine treatment appears to improve these effects. This study tests the hypothesis that perinatal taurine exposure predisposes recovery from reperfusion injury in rats on either a basal or high sugar diet. Female Sprague-Dawley rats were fed normal rat chow with 3% beta-alanine (taurine depletion, TD), 3% taurine (taurine supplementation, TS) or water alone (control, C) from conception to weaning. Male offspring were fed normal rat chow and water containing 5% glucose (G) or water alone (W) throughout the experiment. At 7-8 weeks of age, all rats were anesthetized and their trachea clamped until cardiac arrest occurred and mean arterial pressure fell below 60 mm Hg. The clamp was immediately released and cardiopulmonary resuscitation was performed with cardiac function returning within 4 min. Twenty-four hours later, arterial pressure, heart rate, and baroreflex function were measured in conscious and one day later in anesthetized conditions. Basic blood chemistry and circulating markers of cardiac injury were also measured. Baroreflex sensitivity was depressed moderately in CG and TDW, and severely in TDG. TSW displayed increased baroreflex and high sugar intake returned it to CW. Sympathetic nerve activity increased and parasympathetic decreased in TDW but not TSW and these effects were exacerbated sharply in TDG and slightly in TSG. Arterial pressure and heart rate increased in all groups but to a lesser degree in TDG. Plasma aspartate aminotransferase increased in all groups except TSW, but the increase was nearly 3X greater in TDG vs. any other group. Creatine kinase-MB increased in all groups except TSG and was far greater in TD than other groups. Troponin-T and brain natriuretic peptide were greatly increased in TDG compared to all other groups. Thus, perinatal taurine depletion increases injury from cardiac ischemia/reperfusion, and in adult rats on a high sugar diet, these effects are greatly exacerbated.

Severe metabolic alkalosis due to the combination of unmeasured cations and hypochloraemia in a patient with gastroparesia and frequent emesis

This report describes a patient with gastroparesia and frequent emesis admitted with severe metabolic alkalaemia, hyperlactataemia and acute renal failure. Metabolic alkalaemia was not only due to hypochloraemia but also due to unmeasured cations. These cations were found to be present by calculating anion gap and strong ion gap (both were negative, which is rare). After massive gastric bleeding the patient had a cardiac arrest; following cardiopulmonary resuscitation and infusion of a large volume of normal saline, new blood tests revealed improvement in chloraemia but also a significant increase in the anion gap, suggesting that unmeasured anions rapidly overcame unmeasured cations. The patient died after sequential episodes of cardiac arrest. Anion gap and strong ion gap were useful in the diagnosis of this "hidden" unusual cause of metabolic alkalosis and also in the diagnosis of metabolic acidosis after cardiac arrest, even with normal/high values of base excess and bicarbonate.

Survival following Profound Lactic Acidosis and Cardiac Arrest: Does Metformin Really Induce Lactic Acidosis?

We report the case of a 63-year-old man who suffered a witnessed pulseless electrical activity cardiac arrest on presentation to the emergency department. Despite a profound post-arrest acidosis (pH 6.48) he went on to make an unexpectedly good recovery. He was treated for metformin-associated lactic acidosis (MALA) and septic shock, although the origin of the sepsis was never confirmed. We discuss the growing evidence against the existence of MALA as a lone diagnosis and the aetiology of post-cardiac arrest metabolic acidosis.

The strong ion gap and outcome after cardiac arrest in patients treated with therapeutic hypothermia: a retrospective study

OBJECTIVE

This study investigates whether the strong ion gap (SIG) is associated with long-term outcome after cardiac arrest in patients treated with therapeutic hypothermia. The hypothesis of the study was that an elevated SIG was associated with unfavourable outcome after cardiac arrest.

DESIGN

Retrospective review of records from 1995 to 2007 of patients who received cardiopulmonary resuscitation.

SETTING

Emergency department of a university hospital.

PATIENTS

Patients who were successfully resuscitated after cardiac arrest (n = 288) and treated with mild therapeutic hypothermia.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Acid-base variables were calculated according to Stewart's approach, as modified by Figge and Fencl, and were determined immediately on admission and 12 h after the return of spontaneous circulation. Acid-base variables were determined at 37 degrees C and are reported without correction for patient temperature. Differences in SIG were compared between patients with favourable (survival 6 months with cerebral performance category 1 or 2) and unfavourable outcomes. SIG on admission and 12 h after return of spontaneous circulation was higher in patients with unfavourable outcome (n = 151; 52%). SIG 12 h after return of spontaneous circulation was identified as an independent predictor of outcome. A SIG > 8.9 mmol/L was associated with an increased cumulative hazard of death.

CONCLUSIONS

An elevated SIG 12 h after return of spontaneous circulation may be associated with unfavourable outcome in patients after cardiac arrest treated with mild therapeutic hypothermia. The unmeasured anions hidden behind an elevated SIG may represent markers of tissue damage.

Severe hyperlactatemia with normal base excess: a quantitative analysis using conventional and Stewart approaches

INTRODUCTION

Critically ill patients might present complex acid-base disorders, even when the pH, PCO2, [HCO3-], and base excess ([BE]) levels are normal. Our hypothesis was that the acidifying effect of severe hyperlactatemia is frequently masked by alkalinizing processes that normalize the [BE]. The goal of the present study was therefore to quantify these disorders using both Stewart and conventional approaches.

METHODS

A total of 1,592 consecutive patients were prospectively evaluated on intensive care unit admission. Patients with severe hyperlactatemia (lactate level > or = 4.0 mmol/l) were grouped according to low or normal [BE] values (<-3 mmol/l or >-3 mmol/l).

RESULTS

Severe hyperlactatemia was present in 168 of the patients (11%). One hundred and thirty-four (80%) patients had low [BE] levels while 34 (20%) patients did not. Shock was more frequently present in the low [BE] group (46% versus 24%, P = 0.02) and chronic obstructive pulmonary disease in the normal [BE] group (38% versus 4%, P < 0.0001). Levels of lactate were slightly higher in patients with low [BE] (6.4 +/- 2.4 mmol/l versus 5.6 +/- 2.1 mmol/l, P = 0.08). According to our study design, the pH, [HCO3-], and strong-ion difference values were lower in patients with low [BE]. Patients with normal [BE] had lower plasma [Cl-] (100 +/- 6 mmol/l versus 107 +/- 5 mmol/l, P < 0.0001) and higher differences between the changes in anion gap and [HCO3-] (5 +/- 6 mmol/l versus 1 +/- 4 mmol/l, P < 0.0001).

CONCLUSION

Critically ill patients may present severe hyperlactatemia with normal values of pH, [HCO3-], and [BE] as a result of associated hypochloremic alkalosis.

Causes of metabolic acidosis in canine hemorrhagic shock: role of unmeasured ions

Introduction

Metabolic acidosis during hemorrhagic shock is common and conventionally considered to be due to hyperlactatemia. There is increasing awareness, however, that other nonlactate, unmeasured anions contribute to this type of acidosis.

Methods

Eleven anesthetized dogs were hemorrhaged to a mean arterial pressure of 45 mm Hg and were kept at this level until a metabolic oxygen debt of 120 mLO₂/kg body weight had evolved. Blood pH, partial pressure of carbon dioxide, and concentrations of sodium, potassium, magnesium, calcium, chloride, lactate, albumin, and phosphate were measured at baseline, in shock, and during 3 hours post-therapy. Strong ion difference and the amount of weak plasma acid were calculated. To detect the presence of unmeasured anions, anion gap and strong ion gap were determined. Capillary electrophoresis was used to identify potential contributors to unmeasured anions.

Results

During induction of shock, pH decreased significantly from 7.41 to 7.19. The transient increase in lactate concentration from 1.5 to 5.5 mEq/L during shock was not sufficient to explain the transient increases in anion gap (+11.0 mEq/L) and strong ion gap (+7.1 mEq/L), suggesting that substantial amounts of unmeasured anions must have been generated. Capillary electrophoresis revealed increases in serum concentration of acetate (2.2 mEq/L), citrate (2.2 mEq/L), α-ketoglutarate (35.3 μEq/L), fumarate (6.2 μEq/L), sulfate (0.1 mEq/L), and urate (55.9 μEq/L) after shock induction.

Conclusion

Large amounts of unmeasured anions were generated after hemorrhage in this highly standardized model of hemorrhagic shock. Capillary electrophoresis suggested that the hitherto unmeasured anions citrate and acetate, but not sulfate, contributed significantly to the changes in strong ion gap associated with induction of shock.

The reno-protective effect of hydration with sodium bicarbonate plus N-acetylcysteine in patients undergoing emergency percutaneous coronary intervention: the RENO Study

OBJECTIVES

This study was designed to determine the effectiveness of a protocol for rapid intravenous hydration to prevent contrast-induced nephropathy (CIN) in patients undergoing emergency percutaneous coronary intervention (PCI).

BACKGROUND

Contrast-induced nephropathy frequently complicates PCI, resulting in prolonged hospitalization and increased in-hospital and long-term morbidity and mortality. Little is known regarding prevention of CIN in patients undergoing urgent PCI.

METHODS

We conducted a prospective, controlled, randomized, single-center trial in 111 consecutive patients with acute coronary syndrome undergoing emergency PCI. As part of the hydration therapy, 56 patients (group A) received an infusion of sodium bicarbonate plus N-acetylcysteine (N-AC) started just before contrast injection and continued for 12 h after PCI. The remaining 55 patients (group B) received the standard hydration protocol consisting of intravenous isotonic saline for 12 h after PCI. In both groups, 2 doses of oral N-AC were administered the next day.

RESULTS

The 2 groups were similar with respect to age, gender, diabetes mellitus, and baseline serum creatinine. A serum creatinine concentration >0.5 mg/dl from baseline after emergency PCI was observed in 1 patient in group A (1.8%) and in 12 patients in group B (21.8%; p < 0.001). Acute anuric renal failure was observed in 1 patient (1.8%) in group A and in 7 patients (12.7%) in group B (p = 0.032).

CONCLUSIONS

Rapid intravenous hydration with sodium bicarbonate plus N-AC before contrast injection is effective and safe in the prevention of CIN in patients undergoing emergency PCI.