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

The role of serum chloride ion in the prognosis of COPD

BACKGROUND

As exacerbations of chronic obstructive pulmonary disease (COPD) are one of the leading causes of hospitalization and are associated with significant mortality, it is particularly important to accurately assess the risk of exacerbations in COPD. Most of the current clinical biomarkers are related to inflammation and few consider how ion levels affect COPD. Chloride ion, the second most abundant serum electrolyte, has been shown to be associated with poor prognoses in several diseases, but their relationship with COPD remains unclear.

METHODS

In total, 105 patients with acute exacerbations of COPD were recruited. Data on clinical characteristics, lung function, blood count, blood biochemistry, relevant scales including the Clinical COPD Questionnaire (CCQ), BODE (BMI, airflow obstruction, dyspnea, exercise capacity) index and the St. George's Respiratory Questionnaire (SGRQ) were collected from all patients for statistical analysis.

RESULT

There were significant differences in lung function indicators and disease severity in the low chloride ion subgroup compared with the high chloride ion subgroup. On multiple logistic regression analysis, chloride ion was an independent factor affecting lung function in COPD patients (OR = 0.808, 95% CI: 0.708 - 0.922, p = 0.002). The sensitivity of chloride ion in predicting COPD severity was 78%, the specificity was 63%, and the area under the curve was 0.734 (p < 0.001). Subgroup analysis showed that chloride ion was a stronger predictor in male and smoking patients.

CONCLUSIONS

Chloride ion was a novel prognostic biomarker for COPD, and low levels of chloride ion were independently associated with exacerbations in COPD patients.

Acid-Base Analysis in the Operating Room: A Bedside Stewart Approach

The bedside Stewart approach to acid–base disorders is a simple, pragmatic tool that can assist anesthesiologists in analyzing and managing acid–base changes in the operating room, particularly metabolic acidosis.

Stewart analysis unmasks acidifying and alkalizing effects of ionic shifts during acute severe respiratory alkalosis

PURPOSE

Although both the Henderson-Hasselbalch method and the Stewart approach can be used to analyze acid-base disturbances and metabolic and respiratory compensation mechanisms, the latter may be superior in detecting subtle metabolic changes.

MATERIALS AND METHODS

We analyzed acid-base disturbances using both approaches in six healthy male volunteers practicing extreme voluntary hyperventilation. Arterial blood gas parameters were obtained during a breathing exercise consisting of approximately 30 cycles of powerful hyperventilation followed by breath retention for approximately 2 min.

RESULTS

Hyperventilation increased pH from 7.39 ± 0.01 at baseline to 7.74 ± 0.06, PaCO₂ decreased from 34.1 ± 1.1 to 12.6 ± 0.7 mmHg, PaO₂ increased from 116 ± 4.6 to 156 ± 4.3 mmHg. Baseline apparent strong ion difference was 42.3 ± 0.5 mEq/L, which decreased to 37.1 ± 0.7 mEq/L following hyperventilation. The strong ion gap significantly decreased following hyperventilation, with baseline levels of 10.0 ± 0.9 dropping to 6.4 ± 1.1 mEq/L.

CONCLUSIONS

Henderson-Hasselbalch analysis indicated a profound and purely respiratory alkalosis with no metabolic compensation following extreme hyperventilation. The Stewart approach revealed metabolic compensation occurring within minutes. These results challenge the long-held axiom that metabolic compensation of acute respiratory acid-base changes is a slow process.

The hidden secrets of a neutral pH-blood gas analysis of postoperative patients according to the Stewart approach

Background

The superiority of either the traditional or Stewart based approach to acid-base balance has focused primarily on analyzing metabolic acidemia, with little attention given to patients with neutral pH. In this study, we evaluate metabolic disturbances in patients in the immediate postoperative period focusing on patients with neutral pH, while comparing the Stewart and traditional approach.

Methods

We conducted a single center retrospective observational cohort study. Over a 17-month period, data on arterial blood gas analysis, electrolytes, and albumin on the morning after surgery were retrieved from patients admitted to the postsurgical high dependency unit (HDU). Albumin-corrected anion gap (AG), apparent (SIDa) and effective strong ion difference (SIDe), and strong ion gap (SIG) were calculated.

Results

Out of 1207 HDU admissions, 400 cases had a complete set of laboratory-data including albumin of which 281 presented with neutral pH (7.35 ≤ pH ≤ 7.45), 64 with acidemia (pH < 7.35) and 55 with alkalemia (pH > 7.45). In pH neutral patients, the following acidifying disturbances were found: SIDa was lowered in 101 (36%), and SIG was raised in 60 (21%). Base excess (BE) was decreased in 16 (6%) and corrected AG raised in 107 (38%). The alkalizing effect of hypoalbuminemia was present in 137 (49%). Out of 134 cases with normal BE and corrected AG, SIDa was lowered in 58 (43%). Out of 136 cases with normal SIDa and SIG, none had lowered BE and 28 increased AG (21%). Length of stay was significantly longer in patients with hypoalbuminemia, lowered SIDa, and increased corrected AG, but not decreased BE (hypoalbuminemia: 16 days vs. 10 days, P < 0.001; low SIDa: 15 days vs. 12 days, P = 0.015; increased AG: 16 days vs. 11 days, P < 0.001; low BE: 14 days vs. 13 days, P = 0.736).

Conclusions

Metabolic disturbances, characterized mainly by the presence of lowered SIDa, increased AG, and hypoalbuminemia, are frequent in our population with apparent neutral acid-base balance based on pH and base excess. These changes on the morning after surgery are associated with increased length of stay.

Hypochloremia is associated with increased risk of all-cause mortality in patients in the coronary care unit: A cohort study

Objective

Serum chloride disorders have been gaining increased attention. We aimed to assess the impact of serum chloride on all-cause mortality in critically ill patients in coronary care units (CCUs).

Methods

We extracted clinical data from the Multiparameter Intelligent Monitoring in Intensive Care III database. We used data for the first CCU admission of each patient; baseline data were extracted within 24 hours after CCU admission. Statistical methods included the Lowess smoothing technique, Cox proportional hazards model, and subgroup analyses.

Results

A total 5616 patients who met the inclusion criteria were included. We observed a U-shaped relationship between admission chloride levels and 30-day all-cause mortality. In multivariate analysis adjusted for age, ethnicity, and sex, both hyper- and hypochloremia were significant predictors of risk of 30-day, 90-day, and 365-day all-cause mortality. After adjusting additional clinical characteristics, hypochloremia remained a significant predictor of risk of 30-day all-cause mortality (hazard ratio, 1.47; 95% confidence interval, 1.19–1.83). For 90-day and 365-day all-cause mortality, similar significant robust associations were found.

Conclusions

We observed a U-shaped relationship between admission chloride levels and 30-day all-cause mortality among patients in the CCU. Hypochloremia was associated with increased risk of all-cause mortality in these patients.

The effects of severe hemoconcentration on acid-base equilibrium in critically ill patients: the forgotten role of buffers in whole blood

PURPOSE

Idiopathic Systemic Capillary Leak Syndrome (ISCLS) is a paroxysmal permeability disorder characterized by abrupt onset of shock and hemoconcentration due to massive shift of fluids and proteins from the intravascular to the interstitial compartment. We hypothesize that increased hemoglobin concentration has a pivotal role in the acid-base imbalance during life-threatening crises.

MATERIALS AND METHODS

Analysis of the acid-base balance fluctuations during six severe ISCLS flares admitted to ICU of a referral center for ISCLS.

RESULTS

Acid-base equilibrium was assessed for plasma and the whole blood by single and multicompartmental models. The acute phase of ISCLS was characterized by shock, hypoalbuminemia, severe hemoconcentration, and acidosis. The physical-chemical approach for plasma found a remarkable component of unmeasured anions (SIG) during the acute phase. After correction of the physical-chemical model for the whole blood, the SIG variations disappeared because the buffer role of hemoglobin was relevant.

CONCLUSION

Hemoglobin has a remarkable role in buffering metabolic acidosis during the shock phase of ISCLS. In these circumstances, the assessment of acid-base equilibrium in plasma alone may overestimate unmeasured anions. On the contrary, the physical-chemical model corrected for whole blood better explains the metabolic component of acid-base imbalance when marked shift of hemoglobin concentration occurs.

Role of electrolyte abnormalities and unmeasured anions in the metabolic acid-base abnormalities in dogs with parvoviral enteritis

BACKGROUND

The strong ion model (SIM) is an alternative paradigm in the characterization of acid-base disturbances particularly in complex disorders.

HYPOTHESIS/OBJECTIVES

To compare the acid-base changes in dogs with parvoviral enteritis (PE) using the Henderson-Hasselbalch (HH) approach, with 2 strong ion approaches.

ANIMALS

Forty-four dogs with PE, and 16 age-matched control dogs.

METHODS

Prospective controlled observational study. Acid-base status was evaluated using the HH model, Fencl-Stewart (FS) approach and a validated strong ion model (VDM). The acid-base changes according to each model were classified and compared. Statistical correlations between pH, CO₂ , and various SIM variables were performed, as well as between the sum of effects (SOE) of the SIM and the individual variables comprising the SOE.

RESULTS

The HH model identified acid-base disorders in 31/44 cases of which 16/31 were mixed with metabolic acidosis and concurrent respiratory alkalosis the most common (10/31). Using the FS approach, metabolic changes were present 36/42 cases, with changes in free water (FW), chloride, and unmeasured anions (UA) being the most prevalent. Both FW and UA correlated well with pH; however, UA were most consistently abnormal in severe acidemia. Similarly to the HH, the VDM detected acid-base disturbances in 28/44 cases. Major contributors to the acid-base changes were hyponatremia, hypochloremia, and A_tot acidosis because of elevated globulins and increased UA.

CONCLUSIONS AND CLINICAL IMPORTANCE

Acid-base changes are common and complex in dogs with PE, and were easier to understand using a SIM paradigm. Increases in UA have not been documented in PE in dogs.

A physiology-based mathematical model for the selection of appropriate ventilator controls for lung and diaphragm protection

Mechanical ventilation is used to sustain respiratory function in patients with acute respiratory failure. To aid clinicians in consistently selecting lung- and diaphragm-protective ventilation settings, a physiology-based decision support system is needed. To form the foundation of such a system, a comprehensive physiological model which captures the dynamics of ventilation has been developed. The Lung and Diaphragm Protective Ventilation (LDPV) model centers around respiratory drive and incorporates respiratory system mechanics, ventilator mechanics, and blood acid–base balance. The model uses patient-specific parameters as inputs and outputs predictions of a patient’s transpulmonary and esophageal driving pressures (outputs most clinically relevant to lung and diaphragm safety), as well as their blood pH, under various ventilator and sedation conditions. Model simulations and global optimization techniques were used to evaluate and characterize the model. The LDPV model is demonstrated to describe a CO₂ respiratory response that is comparable to what is found in literature. Sensitivity analysis of the model indicate that the ventilator and sedation settings incorporated in the model have a significant impact on the target output parameters. Finally, the model is seen to be able to provide robust predictions of esophageal pressure, transpulmonary pressure and blood pH for patient parameters with realistic variability. The LDPV model is a robust physiological model which produces outputs which directly target and reflect the risk of ventilator-induced lung and diaphragm injury. Ventilation and sedation parameters are seen to modulate the model outputs in accordance with what is currently known in literature.

Comparative analysis of acid-base balance in patients with severe sepsis and septic shock: traditional approach vs. physicochemical approach

Introduction: The evaluation of metabolism and the diagnostic classification of acid-base disorders has generated great controversy. Acid-base balance (ABB) is approached by means of the physicochemical and Henderson’s models.Objective: To compare two diagnostic approaches to ABB in patients with severe sepsis.Materials and methods: Prospective, descriptive study conducted in patients with severe sepsis. ABB was analyzed within the first 24 hours. The diagnosis was compared according to each model and the causes of the disorders were compared according to the physicochemical model.Results: 38 patients were included in the study, of which 21 (55%) were women; the mean age was 49 years, the median APACHE II, 13.28, and the mortality at 28 days, 24.3%. The traditional approach identified 8 patients with normal ABB, 20 with metabolic acidosis, and 10 with other disorders. Based on the physicochemical model, all subjects had acidosis and metabolic alkalosis. Increased strong ion difference (SID) was the most frequently observed disorder.Conclusion: The physicochemical model was useful to diagnose more patients with acid-base disorders. According to these results, all cases presented with acidosis and metabolic alkalosis; the most frequent proposed mechanism of acidosis was elevated SID. The nature of these disorders and their clinical relevance is yet to be established.

Hyperchloremia in Intensive Care Unit Mortality: An Underestimated Fact

Objective

The goal of the study was to determine the percentage of hyperchloremia in patients who died in medical intensive care unit (ICU) and thus emphasizing the need of avoiding chloride-rich solutions due to their deleterious effects.

Study design

We conducted a retrospective study of data from 206 patients who expired in medical ICU in one year from January 2017 to December 2017 in the department of critical care medicine at Shifa International Hospital, Islamabad.

Material and methods

The study included 206 patients: 93 (43.1%) men and 123 (56.9%) women, over the age of 18 years who expired in medical ICU in one year from January 2017 to December 2017. Patients included for the study were all those who expired with any diagnosis but those who remained admitted in ICU for at least 72 hours and received intravenous fluids. The serum chloride levels of the patients at the time of admission and at 72 hours of stay in ICU were collected. The patients who were having serum chloride levels of 107 milliequivalent per deciliter (meq/dl) or more were labeled as having hyperchloremia. The data were analyzed using IBM SPSS Statistics for Windows, Version 23.0 (IBM Crop., Armonk, NY, USA). The mean and standard deviations were calculated for continuous variables while frequency and percentages were calculated for qualitative variables.

Results

Among 206 patients who expired in our ICU, 109 (50.5%) patients had hyperchloremia at 72 hours of admission in ICU while 107 (49.5%) patients did not had hyperchloremia. Hyperchloremia was more frequent in patients with sepsis or septic shock.

Conclusion

Higher percentage (50.5%) of hyperchloremia at 72 hours of admission among patients (who expired in our medical ICU) indicates excessive use of chloride-rich intravenous fluids. This finding may have significant impact on mortality along with other contributing factors that lead to death of the patients. Keeping in view the findings of the study, chloride-rich solutions should be used carefully to counter the effects of hyperchloremia in patients requiring large volume fluid resuscitation in ICU. Fluids with lower content of chloride such as lactated ringer may be equally good in large volume fluid resuscitation with advantage of avoiding hyperchloremia.

Damage control orthopaedics: State of the art

Damage control orthopaedics (DCO) originally consisted of the provisional immobilisation of long bone - mainly femur - fractures in order to achieve the advantages of early treatment and to minimise the risk of complications, such as major pain, fat embolism, clotting, pathological inflammatory response, severe haemorrhage triggering the lethal triad, and the traumatic effects of major surgery on a patient who is already traumatised (the “second hit” effect). In recent years, new locations have been added to the DCO concept, such as injuries to the pelvis, spine and upper limbs. Nonetheless, this concept has not yet been validated in well-designed prospective studies, and much controversy remains. Indeed, some researchers believe the indiscriminate application of DCO might be harmful and produce substantial and unnecessary expense. In this respect, too, normalised parameters associated with the acid-base system have been proposed, under a concept termed early appropriate care, in the view that this would enable patients to receive major surgical procedures in an approach offering the advantages of early total care together with the apparent safety of DCO. This paper discusses the diagnosis and treatment of severely traumatised patients managed in accordance with DCO and highlights the possible drawbacks of this treatment principle.

Clinical use of plasma lactate concentration. Part 1: Physiology, pathophysiology, and measurement

OBJECTIVE

To review the current literature with respect to the physiology, pathophysiology, and measurement of lactate.

DATA SOURCES

Data were sourced from veterinary and human clinical trials, retrospective studies, experimental studies, and review articles. Articles were retrieved without date restrictions and were sourced primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection.

HUMAN AND VETERINARY DATA SYNTHESIS

Lactate is an important energy storage molecule, the production of which preserves cellular energy production and mitigates the acidosis from ATP hydrolysis. Although the most common cause of hyperlactatemia is inadequate tissue oxygen delivery, hyperlactatemia can, and does occur in the face of apparently adequate oxygen supply. At a cellular level, the pathogenesis of hyperlactatemia varies widely depending on the underlying cause. Microcirculatory dysfunction, mitochondrial dysfunction, and epinephrine-mediated stimulation of Na⁺ -K⁺ -ATPase pumps are likely important contributors to hyperlactatemia in critically ill patients. Ultimately, hyperlactatemia is a marker of altered cellular bioenergetics.

CONCLUSION

The etiology of hyperlactatemia is complex and multifactorial. Understanding the relevant pathophysiology is helpful when characterizing hyperlactatemia in clinical patients.

Strong ion difference and CVVH: Different response during nadroparin versus citrate anticoagulation

PURPOSE

To determine the effect on strong ion difference of citrate as an anticoagulant during continuous veno-venous hemofiltration (CVVH).

MATERIALS AND METHODS

ICU patients with renal failure and CVVH were included. Patients were treated with either nadroparin (N) or sodium citrate (C) as an anticoagulant. Strong ion difference (SID) apparent (SIDa) and SID effective (SIDe) and strong ion gap (SIG) were calculated at t = 0 and t = 24 h. Citrate concentration was measured in the citrate treated patients.

RESULTS

Ten patients with N and nine with C were included. In both groups the SIDa did not change significantly. SIG decreased significantly with N (11.4 ± 4.2 to 4.0 ± 3.1 meq/l; p = 0.005) but not with C (9.3 ± 1.9 to 8.1 ± 2.4 meq/l; p = 0.097). The decrease was significantly greater for N compared to C; p = 0.014. This is reflected by the SIDe which increased significantly (p = 0.022) more from 24.7 ± 4.5 to 32.9 ± 3.9 (p = 0.005) for N and from 26.3 ± 5.8 to 29.6 ± 1.6 for C (p = 0.058).

CONCLUSION

Citrate anticoagulation results in a persistently high SIG during CVVH compared to nadroparin. This is associated with the presence of unmeasured anions such as citrate in the systemic circulation.

Baseline Chloride Levels are Associated with the Incidence of Contrast-Associated Acute Kidney Injury

Although hypo- and hyperchloremia have been associated with worsening renal outcomes, there has been no study that correlates hypo- and hyperchloremia and the incidence of contrast-associated acute kidney injury (CA-AKI). A total of 13,088 patients with less than 2.0 mg/dL of serum creatinine (Cr) who underwent contrast-enhanced abdominal CT (CECT) were included. Patients were divided into 3 groups based on Cl (the hypo-, normo- and hyperchloremia groups). Patients were also classified by baseline Cr (<1.2; the ‘Normal Cr group’ and 1.2–2.0 mg/dL; the ‘Slightly increased Cr group’). Multivariate logistic regression analysis was used to reveal the association between Cl and CA-AKI. Among patients, 2,525 (19.3%) and 241 (1.8%) patients were classified in the hypo- and hyperchloremia group. The incidence of CA-AKI was significantly lower in the normochloremia group (4.0%) compared to the hypo- (5.4%) and hyperchloremia groups (9.5%). On multivariate logistic regression, hypochloremia was significantly associated with the incidence of CA-AKI compared with normochloremia (1.382, P = 0.002). Moreover, hypochloremia was still significantly associated with the incidence of CA-AKI in ‘Normal Cr group’ compared with normochloremia (1.314, P = 0.015), while hyperchloremia did not show significant association with CA-AKI incidence. In conclusion, hypochloremia might be associated with the incidence of CA-AKI even in patients who have normal-range Cr levels.

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.

An increased chloride level in hypochloremia is associated with decreased mortality in patients with severe sepsis or septic shock

Only a few observational studies investigated the association between hypochloremia and mortality in critically ill patients, and these studies included small number of septic patients. Also, no study has evaluated the effect of an increase in chloride (Cl^-) concentration in hypochloremia on the mortality. A total of 843 Korean septic patients were divided into three groups based on their baseline Cl^- level, and Cox analyses were performed to evaluate the 28-day mortality. Moreover, the change in Cl^- level (ΔCl) from baseline to 24, 48, or 72 hour was determined, and Cox analyses were also conducted to evaluate the relationship of ΔCl with mortality. 301 (35.7%) patients were hypochloremic (Cl^- < 97 mEq/L), and 38 (4.5%) patients were hyperchloremic (Cl^- > 110 mEq/L). During the follow-up period, 119 (14.1%) patients died. Hypochloremia was significantly associated with an increased mortality after adjusting for several variables, but an 1 mEq/L increase of ΔCl within 24 hour in patients with hypochloremia was significantly related to a decreased mortality. Caution might be required in severe septic patients with hypochloremia considering their increased mortality rate. However, an increased Cl^- concentration might decrease the mortality rate of such patients.

A comparison of prognostic significance of strong ion gap (SIG) with other acid-base markers in the critically ill: a cohort study

Background

This cohort study compared the prognostic significance of strong ion gap (SIG) with other acid-base markers in the critically ill.

Methods

The relationships between SIG, lactate, anion gap (AG), anion gap albumin-corrected (AG-corrected), base excess or strong ion difference-effective (SIDe), all obtained within the first hour of intensive care unit (ICU) admission, and the hospital mortality of 6878 patients were analysed. The prognostic significance of each acid-base marker, both alone and in combination with the Admission Mortality Prediction Model (MPM₀ III) predicted mortality, were assessed by the area under the receiver operating characteristic curve (AUROC).

Results

Of the 6878 patients included in the study, 924 patients (13.4 %) died after ICU admission. Except for plasma chloride concentrations, all acid-base markers were significantly different between the survivors and non-survivors. SIG (with lactate: AUROC 0.631, confidence interval [CI] 0.611–0.652; without lactate: AUROC 0.521, 95 % CI 0.500–0.542) only had a modest ability to predict hospital mortality, and this was no better than using lactate concentration alone (AUROC 0.701, 95 % 0.682–0.721). Adding AG-corrected or SIG to a combination of lactate and MPM₀ III predicted risks also did not substantially improve the latter’s ability to differentiate between survivors and non-survivors. Arterial lactate concentrations explained about 11 % of the variability in the observed mortality, and it was more important than SIG (0.6 %) and SIDe (0.9 %) in predicting hospital mortality after adjusting for MPM₀ III predicted risks. Lactate remained as the strongest predictor for mortality in a sensitivity multivariate analysis, allowing for non-linearity of all acid-base markers.

Conclusions

The prognostic significance of SIG was modest and inferior to arterial lactate concentration for the critically ill. Lactate concentration should always be considered regardless whether physiological, base excess or physical-chemical approach is used to interpret acid-base disturbances in critically ill patients.

Association of Hyperchloremia With Hospital Mortality in Critically Ill Septic Patients

OBJECTIVES

Hyperchloremia is frequently observed in critically ill patients in the ICU. Our study aimed to examine the association of serum chloride (Cl) levels with hospital mortality in septic ICU patients.

DESIGN

Retrospective cohort study.

SETTING

Urban academic medical center ICU.

PATIENTS

ICU adult patients with severe sepsis or septic shock who had Cl measured on ICU admission were included. Those with baseline estimated glomerular filtration rate less than 15 mL/min/1.73 m or chronic dialysis were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 1,940 patients included in the study, 615 patients (31.7%) had hyperchloremia (Cl ≥ 110 mEq/L) on ICU admission. All-cause hospital mortality was the dependent variable. Cl on ICU admission (Cl0), Cl at 72 hours (Cl72), and delta Cl (ΔCl = Cl72 - Cl0) were the independent variables. Those with Cl0 greater than or equal to 110 mEq/L were older and had higher cumulative fluid balance, base deficit, and Sequential Organ Failure Assessment scores. Multivariate analysis showed that higher Cl72 but not Cl0 was independently associated with hospital mortality in the subgroup of patients with hyperchloremia on ICU admission (adjusted odds ratio for Cl72 per 5 mEq/L increase = 1.27; 95% CI, 1.02-1.59; p = 0.03). For those who were hyperchloremic on ICU admission, every within-subject 5 mEq/L increment in Cl72 was independently associated with hospital mortality (adjusted odds ratio for ΔCl 5 mEq/L = 1.37; 95% CI, 1.11-1.69; p = 0.003).

CONCLUSIONS

In critically ill septic patients manifesting hyperchloremia (Cl ≥ 110 mEq/L) on ICU admission, higher Cl levels and within-subject worsening hyperchloremia at 72 hours of ICU stay were associated with all-cause hospital mortality. These associations were independent of base deficit, cumulative fluid balance, acute kidney injury, and other critical illness parameters.

Strong ion and weak acid analysis in severe preeclampsia: potential clinical significance

BACKGROUND

The influence of common disturbances seen in preeclampsia, such as changes in strong ions and weak acids (particularly albumin) on acid-base status, has not been fully elucidated. The aims of this study were to provide a comprehensive acid-base analysis in severe preeclampsia and to identify potential new biological predictors of disease severity.

METHODS

Fifty women with severe preeclampsia, 25 healthy non-pregnant- and 46 healthy pregnant controls (26-40 weeks' gestation), were enrolled in this prospective case-control study. Acid-base analysis was performed by applying the physicochemical approach of Stewart and Gilfix.

RESULTS

Mean [sd] base excess was similar in preeclamptic- and healthy pregnant women (-3.3 [2.3], and -2.8 [1.5] mEq/L respectively). In preeclampsia, there were greater offsetting contributions to the base excess, in the form of hyperchloraemia (BE(Cl) -2 [2.3] vs -0.4 [2.3] mEq/L, P<0.001) and hypoalbuminaemia (BE(Alb) 3.6 [1] vs 2.1 [0.8] mEq/L, P<0.001). In preeclampsia, hypoalbuminaemic metabolic alkalosis was associated with a non-reassuring/abnormal fetal heart tracing (P<0.001). Quantitative analysis in healthy pregnancy revealed respiratory and hypoalbuminaemic alkalosis that was metabolically offset by acidosis, secondary to unmeasured anions and dilution.

CONCLUSIONS

While the overall base excess in severe preeclampsia is similar to that in healthy pregnancy, preeclampsia is associated with a greater imbalance offsetting hypoalbuminaemic alkalosis and hyperchloraemic acidosis. Rather than the absolute value of base excess, the magnitude of these opposing contributors may be a better indicator of the severity of this disease. Hypoalbuminaemic alkalosis may also be a predictor of fetal compromise.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov: NCT 02164370.