Hypoalbuminaemia in critically ill children: incidence, prognosis, and influence on the anion gap

Association between serum albumin levels at admission and clinical outcomes in pediatric intensive care units: a multi-center study

BACKGROUND

Albumin, a vital component in regulating human blood oncotic pressure, plays an important role in the prediction of prognosis in pediatric patients.Previous research identified significant differences in serum albumin levels of healthy and critically ill children.

METHODS

The present study aims to investigate the correlation between albumin levels measured during pediatric intensive care unit(PICU) admission and clinical outcomes. In 2022, a comprehensive analysis of the records was conducted retrospectively in four tertiary hospital PICUs in different cities in the south-east region of Turkey. We then conducted a ROC analysis to predict mortality based on hypoalbuminemia.A cut-off value was determined, and the patients were divided into two groups: hypoalbuminemic and normoalbuminemic.Based on this cut-off level, we evaluated the association between admission serum albumin levels and mortality, length of stay, laboratories, need for mechanical ventilation, and extracorporeal treatments.

RESULTS

A total of 1329 patients admitted to the PICUs between January 1, 2022 and January 1, 2023 were included. The mortality rate amounted to 16.2%.The mean albumin level was 4.03 ± 0.69 g/dl in the surviving and 3.35 ± 0.90 g/dl in the non-surviving group(p < 0.001).The average length of stay in the PICU amounted to 8.98 ± 17.07, while the mean length of hospital stay was 11.23 ± 18.81days.Patients with hypoalbuminemia had significantly longer stays in the PICU and hospital as compared to those with normal albumin levels(p = 0.025 and p < 0.001,respectively).We found robust evidence that albumin levels are a strong predictor of mortality, with a predictive rate of 84.5%(OR:0.322, 95% CI:0.263-0.395, p < 0.001).The cut-off value was 3.785(AUC:0.731, Sensitivity:68.3%, Specificity:67%). A negative correlation was identified between albumin levels and lactate, C- reactive protein (CRP), and Blood urea nitrogen (BUN) levels across all patients. Conversely, a positive correlation was observed between neutrophil, lymphocyte, platelet, hemoglobin, sodium, and glucose levels. However, in patients with a cut-off point of 3.785 for albumin levels, a negative correlation was observed between albumin and lactate, CRP, and creatine levels. Conversely, a positive correlation was found between bicarbonate, platelet, hemoglobin, and glucose levels. Based on these findings, we conclude that hypoalbuminemia is associated with a higher rate of inotrope therapy and mechanical ventilation support. Furthermore, the rates of plasmapheresis, continuous renal replacement therapy, and extracorporeal membrane oxygenation initiation were markedly reduced in patients with elevated albumin levels (p < 0.001).

CONCLUSION

The serum albumin, which is an excellent and cost-effective biomarker that can be readily and economically evaluated in any center worldwide, as evidenced by the findings of our study, is a highly efficacious indicator of admission albumin levels for the prediction of mortality and outcomes in PICUs. Furthermore, it predicts the selection of appropriate treatment and mechanical supports. It is straightforward to utilise, as it does not necessitate the use of scoring systems or tests that require lengthy and intricate analyses, and it is readily available.

A Narrative Literature Review of the Established Safety of Human Serum Albumin Use as a Stabilizer in Aesthetic Botulinum Toxin Formulations Compared to Alternatives

Despite more than 80 years of use in a number of conditions, including in critically ill patients, comments have recently arisen regarding the safety and efficacy of human serum albumin (HSA) as a therapeutic product and stabilizer/excipient in botulinum neurotoxins. This review summarizes the literature on the safety of HSA. Beyond decades of safe use, the largest clinical dataset of HSA safety is a large meta-analysis of HSA supplier data, which found only an extremely remote risk of serious adverse events across millions of doses of therapeutic concentrations of HSA. There is a paucity of literature identifying HSA-specific adverse events when used as a stabilizer/excipient; however, studies of HSA-containing botulinum neurotoxins (BoNTs) suggest that adverse events are not related to HSA. Polysorbates, which are synthetically produced and not physiologically inert, are contained in pending or new-to-market BoNT formulations. In contrast to HSA, evidence exists to suggest that polysorbates (particularly PS20/PS80) can cause serious adverse events (e.g., hypersensitivity, anaphylaxis, and immunogenicity).

Association between albumin corrected anion gap and 30-day all-cause mortality of critically ill patients with acute myocardial infarction: a retrospective analysis based on the MIMIC-IV database

BACKGROUND

The anion gap (AG) has been linked to the prognosis of many cardiovascular disorders. However, the correlation between albumin-corrected anion gap (ACAG) and 30 d all-cause mortality of intensive care patients with acute myocardial infarction (AMI) is unclear. Furthermore, owing to the lack of studies, it is also unknown whether ACAG is more accurate than AG in predicting the mortality of AMI.

METHODS

The Medical Information Mart for Intensive Care IV (MIMIC IV) dataset was used to provide patient data in this retrospective cohort study. ACAG is computed using the formulae: [4.4-{albumin (g/dl)}] × 2.5 + AG. The primary outcome was 30 d all-cause mortality intensive care patients with AMI. To explore the prognostic worthiness of ACAG, the receiver operating characteristic curve, smooth curve fitting, Cox regression model, and Kaplan survival analysis was performed.

RESULTS

We enrolled 2,160 patients in this study. ACAG had a better predictive value for 30 d all-cause mortality than AG, with an area under the curve of 0.66. The association between ACAG levels and overall mortality was nonlinear. In our model, after correcting for confounding factors, the ACAG was the independent predictor for 30 d all-cause mortality (HR 1.75, 95%CI 1.24, 2.47). ACAG K-M estimator curve analyses revealed that the group with ACAG ≥ 21.75 mmol/l had poor survival rate than the other group.

CONCLUSIONS

High serum ACAG levels were a significant risk factor for 30 d all-cause mortality in critically ill patients with AMI. ACAG concentration and 30 d all-cause mortality had a nonlinear relationship. ACAG had better predictive value in identifying 30 d all-cause mortality of patients with AMI in ICU than the AG.

Acute diarrhea in horses: A multicenter Canadian retrospective study (2015 to 2019)

This study describes the clinicopathological findings, diagnostic approach, treatment, and factors associated with non-survival of diarrheic horses admitted to 4 Canadian university teaching hospitals between 2015 and 2019. A total of 300 horses, ≥1-year-old, with acute diarrhea were included and represented 1.6% (300/18 481; range: 0.7 to 3%) of admissions during that period, 70% of the horses survived to discharge. Testing for enteropathogens was limited to a single fecal culture for Salmonella spp. in most cases. An enteropathogen was identified in 14% (42/300) of the horses, but in the hospital with higher testing rates enteropathogens were detected in 29% (16/55) of cases. Neorickettsia risticii was the pathogen most frequently detected (31%, 32/102). Antimicrobial drugs and plasma were administered to 57 and 8% of the cases, respectively. Laminitis occurred in 24/298 (8%) of the horses. A multivariable regression model identified an association between non-survival of diarrheic horses and colic signs, increased heart rate, packed cell volume, creatinine concentration, and decreased total protein concentration. A standardized approach for pathogen detection in diarrheic horses is not consistent among Canadian veterinary teaching hospitals, and testing for known pathogens is limited. Signs of colic, severe dehydration, endotoxemia, and hypoproteinemia are associated with non-survival of diarrheic horses.

Serum Albumin Level as a Predictor of Outcome in Patients Admitted to Pediatric Intensive Care Units

OBJECTIVE

The aim of this study was to assess serum albumin level on admission to the pediatric intensive care unit (PICU) as a prognostic indicator.

METHODS

A prospective study was conducted in Fayoum University Children's Hospital. The study subjects' demographics and clinical and laboratory data were recorded. Pediatric Risk of Mortality III (PRISM-III) score was calculated. Serum albumin level was assessed within 24 hours from admission. Outcomes included mortality, PICU and hospital stay, need and duration of mechanical ventilation, and inotrope use.

RESULTS

The incidence of admission hypoalbuminemia was 26%. The study subjects had a significantly higher mortality rate than subjects with normal albumin levels (42.3% vs 17.6%, respectively, P = 0.011). Each unit of increase in serum albumin decreased the risk of mortality by 28.9% (odds ratio, 0.289; confidence interval, 0.136-0.615, P = 0.001). Serum albumin showed a fair discriminatory power (area under the curve, 0.738). At a cutoff point of ≤3.7 g/dL, albumin had a 79.2% sensitivity, 67.1% specificity, 43.2% positive predictive value, and 91.1% negative predictive value. Incorporation of serum albumin with PRISM-III score was more predictive of mortality than either predictors alone (area under the curve, 0.802). No significant difference was found between the 2 groups regarding either PICU and hospital stay as well as the need and duration of ventilation.

CONCLUSIONS

In PICUs, admission hypoalbuminemia is a good predictor of mortality. Further studies to confirm the value of adding serum albumin to PRISM-III score are recommended.

Recent Advances in Therapeutic Drug Monitoring of Voriconazole, Mycophenolic Acid, and Vancomycin: A Literature Review of Pediatric Studies

The review includes studies dated 2011-2021 presenting the newest information on voriconazole (VCZ), mycophenolic acid (MPA), and vancomycin (VAN) therapeutic drug monitoring (TDM) in children. The need of TDM in pediatric patients has been emphasized by providing the information on the differences in the drugs pharmacokinetics. TDM of VCZ should be mandatory for all pediatric patients with invasive fungal infections (IFIs). Wide inter- and intrapatient variability in VCZ pharmacokinetics cause achieving and maintaining therapeutic concentration during therapy challenging in this population. Demonstrated studies showed, in most cases, VCZ plasma concentrations to be subtherapeutic, despite the updated dosages recommendations. Only repeated TDM can predict drug exposure and individualizing dosing in antifungal therapy in children. In children treated with mycophenolate mofetil (MMF), similarly as in adult patients, the role of TDM for MMF active form, MPA, has not been well established and is undergoing continued debate. Studies on the MPA TDM have been carried out in children after renal transplantation, other organ transplantation such as heart, liver, or intestine, in children after hematopoietic stem cell transplantation or cord blood transplantation, and in children with lupus, nephrotic syndrome, Henoch-Schönlein purpura, and other autoimmune diseases. MPA TDM is based on the area under the concentration-time curve; however, the proposed values differ according to the treatment indication, and other approaches such as pharmacodynamic and pharmacogenetic biomarkers have been proposed. VAN is a bactericidal agent that requires TDM to prevent an acute kidney disease. The particular group of patients is the pediatric one. For this group, the general recommendations of the dosing may not be valid due to the change of the elimination rate and volume of distribution between the subjects. The other factor is the variability among patients that concerns the free fraction of the drug. It may be caused by both the patients' population and sample preconditioning. Although VCZ, MMF, and VAN have been applied in pediatric patients for many years, there are still few issues to be solve regarding TDM of these drugs to ensure safe and effective treatment. Except for pharmacokinetic approach, pharmacodynamics and pharmacogenetics have been more often proposed for TDM.

Individualized precision dosing approaches to optimize antimicrobial therapy in pediatric populations

Introduction:Severe infections continue to impose a major burden on critically ill children and mortality rates remain stagnant. Outcomes rely on accurate and timely delivery of antimicrobials achieving target concentrations in infected tissue. Yet, developmental aspects, disease-related variables, and host factors may severely alter antimicrobial pharmacokinetics in pediatrics. The emergence of antimicrobial resistance increases the need for improved treatment approaches.Areas covered:This narrative review explores why optimization of antimicrobial therapy in neonates, infants, children, and adolescents is crucial and summarizes the possible dosing approaches to achieve antimicrobial individualization. Finally, we outline a roadmap toward scientific evidence informing the development and implementation of precision antimicrobial dosing in critically ill children.The literature search was conducted on PubMed using the following keywords: neonate, infant, child, adolescent, pediatrics, antimicrobial, pharmacokinetic, pharmacodynamic target, Bayes dosing software, optimizing, individualizing, personalizing, precision dosing, drug monitoring, validation, attainment, and software implementation. Further articles were sought from the references of the above searched articles.Expert opinion:Recently, technological innovations have emerged that enabled the development of individualized antimicrobial dosing approaches in adults. More work is required in pediatrics to make individualized antimicrobial dosing approaches widely operationalized in this population.

Low serum albumin concentration predicts the need for surgical intervention in neonates with necrotizing enterocolitis

PURPOSE

To investigate whether serum albumin (SA) concentration can predict the need for surgical intervention in neonates with necrotizing enterocolitis (NEC).

METHODS

Retrospective review of all cases with NEC Bell's stage 2 and 3 that were treated in a single center between 2009 and 2015. Data on patient demographics, clinical parameters, laboratory findings and surgical status were recorded. Receiver operating characteristics analysis was used to evaluate optimal cutoffs and predictive values.

RESULTS

Overall, 151 neonates with NEC were identified. Of these, 132 (87.4%) had confirmed NEC Bell's stage 2. The median gestational age was 28.4 (range, 23.1-39.0) weeks and 69 (52.3%) had a birth weight of ≤1000 g. Sixty-eight (51.5%) underwent surgery, showing a sustained reduction in SA over time with significantly lower median SA levels compared to 64 (48.5%) cases that responded well to medical treatment (18.3 ± 3.7 g/L vs. 26.0 ± 2.0 g/L; P < 0.001). SA concentration of ≤20 g/L on day 2 of NEC diagnosis was a significant predictor for surgery (OR 3.41; P = 0.019) with a positive predictive value of 71.4%.

CONCLUSIONS

An SA concentration of ≤20 g/L on day 2 of the NEC disease process is associated with a higher likelihood for surgical intervention in neonates with NEC Bell's stage 2. SA, in combination with other clinical parameters and serological markers, may be a useful predictive tool for surgery in NEC.

LEVEL OF EVIDENCE

II.

Human albumin solutions in intensive care: A review

Albumin plays a key role in the critically ill patient acting as a prognostic marker and as a therapy in the form of human albumin solutions. However, the use of human albumin solution has varied over time with notable differences between health systems. Whilst its use is widely accepted for some clinical indications, its role has not always been clear in the critically ill and has been found to be harmful in some cohorts. Numerous studies have showed conflicting results and critical care clinicians have not always been guided by robust evidence. Nonetheless, at present the use of human albumin solution appears to be increasing again in the United Kingdom. Below, we discuss the latest evidence base for its use in critically ill patients.

The Utility of Albumin Level as a Marker of Postoperative Course in Infants Undergoing Repair of Congenital Heart Disease

We sought to examine the role of preoperative and 2nd postoperative day albumin levels as predictors for postoperative course in infants undergoing repair of congenital heart disease. This retrospective, single-center, observational study comprised consecutive infants younger than 1 year who had undergone repair of tetralogy of Fallot, ventricular septal defect, complete atrioventricular canal or transposition of the great arteries over a 25 months period. We correlated preoperative and postoperative day (POD) #2 albumin level to vaso-inotropic score (VIS) and intensive care unit (ICU) length of stay (LOS) as markers for degree and duration of postoperative cardiac support. A composite outcome was defined as maximal vaso-inotropic score of > 10 and ICU LOS > 96 h. Preoperative albumin level negatively correlated with VIS and ICU LOS. Compared to preoperative albumin level of > 4 g/dL, the relative risk of meeting composite criteria was 1.5 for preoperative albumin of 3.1-4 g/dL and 2.6 for preoperative albumin ≤ 3 g/dL. Compared to POD#2 albumin level > 3 g/dL, the relative risk of meeting composite criteria was 1.8 for albumin of 2.6-3 g/dL, and 2.5 for albumin ≤ 2.5 g/dL. In summary, we found that preoperative and POD#2 albumin levels predicted prolonged and complicated postoperative course. These finding may help clinicians to inform the patient's parents, early in the ICU hospitalization, as to the predicted risks and difficulties of their infant's postoperative course.

The Influence of Albumin Level in Critically Ill Children to Length of Stay and Mortality in Paediatric Intensive Care Unit

BACKGROUND

The use of albumin in the critical care setting is a very controversial issue. Low serum albumin concentration in critical illness is associated with a poor outcome.

AIM

We aimed to evaluate the influence of albumin level in critically ill children to the length of stay and mortality in the Pediatric Intensive Care Unit (PICU) Haji Adam Malik General Hospital, Medan, Indonesia.

METHODS

The study used an observational method with a cross-sectional design. The population of the study was all patients with major postoperative surgery and critically ill that admitted to the PICU at Haji Adam Malik Hospital from the period of June 2008 to September 2008. The albumin level of the subjects was determined on the first day admitted.

RESULTS

The group with hypoalbuminemia (< 3 g/dL) was given albumin supplementation according to a protocol in the PICU. The group with hypoalbuminemia have an average length of stay 7.6 days (9.7%) and mortality of 12 subjects (36.4%). The group with normal albumin level have 4.7 days (5.0%) and mortality 13 subjects (37.1%). There was no significant effect of albumin level to mortality.

CONCLUSION

Albumin level did not affect the length of stay and mortality in PICU.

Prediction of Early Liver Failure in Pediatric Patients Admitted to Intensive Care Unit

BACKGROUND Hepatic dysfunction has been associated with poor prognosis in critically ill patients. We aimed to investigate the incidence of early liver dysfunction and its association with probable predictive variables in a group of Iranian patients. METHODS The study was conducted on 149 pediatric patients referred to the pediatric intensive care unit (PICU), Shiraz University of Medical Sciences, Shiraz, Iran between April and October 2016. Serum levels of liver aminotransferase, alkaline phosphatase, total bilirubin, direct bilirubin, and international normalized ratio (INR) were recorded in 24, 48, and 96 hours after admission. RESULTS On the first day of admission, direct bilirubin was the least (9.1%) and abnormal alkaline phosphatase level was the most (66.9%) common abnormalities. Abnormal levels of all tests except alkaline phosphatase were predictive of increased rate of mortality. In univariable logistic regression, abnormal aminotransferases (ALT and AST), INR, total bilirubin, and direct bilirubin had significant relationship with patients' mortality after 24, 48, and 96 hours. In multivariable logistic regression only ALT and INR in the first 24 hours had significant relationship with mortality in final model. Although univariate logistic regression revealed a significant relationship between AST and ALT levels with PICU length of stay, no significant relationship was observed between these variables and PICU length of stay (except AST in the first 24 hours) in multivariable analysis. CONCLUSION Increase in liver enzymes may predict mortality and increased PICU length of stay in critically ill children.

Perioperative serum albumin and its influence on clinical outcomes in neonates and infants undergoing cardiac surgery with cardiopulmonary bypass: a multi-centre retrospective study

Hypoalbuminemia is associated with morbidity and mortality in critically ill children. In this multi-centre retrospective study, we aimed to determine normative values of serum albumin in neonates and infants with congenital heart disease, evaluate perioperative changes in albumin levels, and determine if low serum albumin influences post-operative outcomes. Consecutive eligible neonates and infants who underwent cardiac surgery with cardiopulmonary bypass at one of three medical centres, January 2012-August 2013, were included. Data on serum albumin levels from five data points (pre-operative, 0-24, 24-48, 48-72, 72 hours post-operative) were collected. Median pre-operative serum albumin level was 2.5 g/dl (IQR, 2.1-2.8) in neonates versus 4 g/dl (IQR, 3.5-4.4) in infants. Hypoalbuminemia was defined as &lt;25th percentile of these values. A total of 203 patients (126 neonates, 77 infants) were included in the study. Post-operative hypoalbuminemia developed in 12% of neonates and 20% of infants; 97% occurred in the first 48 hours. In multivariable analysis, perioperative hypoalbuminemia was not independently associated with any post-operative morbidity. However, when analysed as a continuous variable, lower serum albumin levels were associated with increased post-operative morbidity. Pre-operative low serum albumin level was independently associated with increased odds of post-operative hypoalbuminemia (OR, 3.67; 95% CI, 1.01-13.29) and prolonged length of hospital stay (RR, 1.40; 95% CI, 1.08-1.82). Lower 0-24-hour post-operative serum albumin level was independently associated with an increased duration of mechanical ventilation (RR, 1.35; 95% CI, 1.12-1.64). Future studies should further assess hypoalbuminemia in this population, with emphasis on evaluating clinically meaningful cut-offs and possibly the use of serum albumin levels in perioperative risk stratification models.

Serum Albumin as a Biomarker of Poor Prognosis in the Pediatric Patients in Intensive Care Unit

Background

Serum albumin as an indicator of the disease severity and mortality is suggested in adult patients, but its role in pediatric patients has not been established. The objectives of this study are to investigate the albumin level as a biomarker of poor prognosis and to compare it with other mortality predictive indices in children in intensive care unit (ICU).

Methods

Medical records of 431 children admitted to the ICU at Severance Hospital from January 1, 2012 to December 31, 2015 were retrospectively analyzed. Children who expired within 24 hours after ICU admission, children with hepatic or renal failure, and those who received albumin replacement before ICU admission were excluded.

Results

The children with hypoalbuminemia had higher 28-day mortality rate (24.60% vs. 9.28%, P < 0.001), Pediatric Index of Mortality (PIM) 3 score (9.23 vs. 8.36, P < 0.001), Pediatric Risk of Mortality (PRISM) III score (7.0 vs. 5.0, P < 0.001), incidence of septic shock (12% vs. 3%, P < 0.001), C-reactive protein (33.0 mg/L vs. 5.8 mg/L, P < 0.001), delta neutrophil index (2.0% vs. 0.6%, P < 0.001), lactate level (1.6 mmol/L vs. 1.2 mmol/L, P < 0.001) and lower platelet level (206,000/μl vs. 341,000/μl, P < 0.001) compared to the children with normal albumin level. PIM 3 (r = 0.219, P < 0.001) and PRISM III (r = 0.375, P < 0.001) were negatively correlated with serum albumin level, respectively.

Conclusions

Our results highlight that hypoalbuminemia can be a biomarker of poor prognosis including mortality in the children in ICU.

Impact of vancomycin protein binding on target attainment in critically ill children: back to the drawing board?

Objectives

The objectives of this observational study were to investigate plasma protein binding and to evaluate target attainment rates of vancomycin therapy in critically ill children.

Patients and methods

Paediatric ICU patients, in whom intravenous intermittent dosing (ID) or continuous dosing (CD) with vancomycin was indicated, were included. Covariates on unbound vancomycin fraction and concentration were tested using a linear mixed model analysis and attainment of currently used pharmacokinetic/pharmacodynamic (PK/PD) targets was evaluated. Clinicaltrials.gov: NCT02456974.

Results

One hundred and eighty-eight plasma samples were collected from 32 patients. The unbound vancomycin fraction (median = 71.1%; IQR = 65.4%-79.7%) was highly variable within and between patients and significantly correlated with total protein and albumin concentration, which were both decreased in our population. Total trough concentration (ID) and total concentration (CD) were within the aimed target concentrations in 8% of patients. The targets of AUC/MIC ≥400 and f AUC/MIC ≥200 were achieved in 54% and 83% of patients, respectively. Unbound vancomycin concentrations were adequately predicted using the following equation: unbound vancomycin concentration (mg/L) = 5.38 + [0.71 × total vancomycin concentration (mg/L)] - [0.085 × total protein concentration (g/L)]. This final model was externally validated using 51 samples from another six patients.

Conclusions

The protein binding of vancomycin in our paediatric population was lower than reported in non-critically ill adults and exhibited large variability. Higher target attainment rates were achieved when using PK/PD indices based on unbound concentrations, when compared with total concentrations. These results highlight the need for protein binding assessment in future vancomycin PK/PD research.

Association between the lactate/albumin ratio and mortality in pediatric septic shock patients with underlying chronic disease: retrospective pilot study

BACKGROUND

We aimed to evaluate the ability of the lactate/albumin ratio to predict mortality in pediatric septic shock patients.

METHODS

Retrospective analysis of the medical records of a pediatric intensive care unit. The study cohort comprised 90 pediatric septic shock patients admitted from February 2012 to May 2015.

RESULTS

The serum lactate and albumin levels and lactate/albumin ratio were compared between survivors and non-survivors. We assessed whether the lactate/albumin ratio could be used to predict mortality. The 28-day hospital mortality was 26.7% (24/90). The lactate level was higher (2.5±2.2 vs. 8.1±5.1 mmol/L, P<0.001) and the albumin level was lower (2.9±0.5 vs. 2.7±0.5 mg/dL, P=0.063) in non-survivors than in survivors. The lactate/albumin ratio was 0.9±0.8 in survivors and 3.2±2.4 in non-survivors (P<0.001). According to the area under the receiver operating characteristic curve (AUC), the lactate/albumin ratio showed good discriminatory power for predicting mortality (AUC=0.867). A lactate/albumin ratio exceeding 1.016 led to a 7.636-fold increase in mortality.

CONCLUSIONS

The lactate/albumin ratio is a useful predictor of mortality in pediatric septic shock patients.

Nutritional status as a predictor of duration of mechanical ventilation in critically ill children

OBJECTIVES

Critically ill children admitted to the pediatric intensive care unit (PICU) often are malnourished. The aim of this study was to determine the role of nutritional status on admission as a predictor of the duration of mechanical ventilation in critically ill children.

METHODS

This was a single-center, prospective cohort study, including consecutive children (ages 1 mo to 15 y) admitted to a PICU. Demographic characteristics, clinical characteristics, and nutritional status were recorded and patients were followed up until hospital discharge. Nutritional status was evaluated by anthropometric parameters and malnutrition was considered if the Z-scores for the parameters were ≤-2. Adjusted Cox's regression analysis was used to determine the association between nutritional status and duration of mechanical ventilation.

RESULTS

In all, 72 patients were included. The prevalence of malnutrition was 41.2%, according to height-for-age Z-score, 18.6% according to weight-for-height Z-score, and 22.1% according body mass index-for-age Z-score. Anthropometrical parameters that predicted the duration of mechanical ventilation were weight-for-age (hazard ratio [HR], 2.73; 95% confidence interval [CI], 1.44-5.18); height-for-age (HR, 2.49; 95% CI, 1.44-4.28); and upper arm muscle area-for-age (HR, 5.22; 95% CI, 1.19-22.76).

CONCLUSION

Malnutrition, based on a variety of anthropometric variables, was associated with the duration of mechanical ventilation in this cohort of critically ill children. Assessment of nutritional status by anthropometry should be performed on admission to the PICU to allow targeted nutritional rehabilitation for the subset of children with existing malnutrition.

Association of Serum Albumin Level and Mortality in Premature Infants

BACKGROUND

Hypoalbuminemia has been proven to be a powerful predictor of mortality in adult patients. However, prognostic value of serum albumin in neonates is not clear.

OBJECTIVE

To assess the relationship between serum albumin level within the first day of life and outcome in preterm infants born before 32 weeks of gestation.

METHODS

The study was conducted prospectively in Baskent University Hospital between October 2008 and November 2009. Patients were divided by gestational age into two groups as below or of 28 weeks and above 28 weeks. Then serum albumin percentile groups were established within each gestational age group and were defined as <25, 25-75, and >75 percentile groups by combining percentile groups between the two gestational age groups. Three serum albumin percentile groups were compared regarding neonatal outcomes.

RESULTS

A total of 199 infants with mean birth weight of 1,272 ± 390 g and mean gestational age of 29.2 ± 2.2 weeks were admitted to the study. The mean serum albumin level was 30.6 ± 4.7 g/l for all patients. The mean serum albumin levels were 25.5 ± 3.8, 30.1 ± 2.7, and 35.3 ± 3.7 g/l for <25, 25-75, and >75 percentile groups, respectively. Prevalence of infants with respiratory distress syndrome and prevalence of infants with sepsis and mortality were significantly higher in <25 percentile group. Logistic regression analysis showed that serum albumin <25 percentile and birth weight were independent predictive variables of mortality. Albumin concentrations lower than 27.2 g/l was associated with mortality, with a sensitivity of 71% and a specificity of 86%.

CONCLUSION

Low serum albumin level within the first day of life is an independent predictor of mortality in preterm infants.

Serum Albumin Is an Independent Predictor of Clinical Outcomes in Critically Ill Children

OBJECTIVES

Serum albumin is a strong biomarker of disease severity and prognosis in adult patients. In contrast, its value as predictor of outcome in critically ill children has not been established. We aimed to determine whether admission hypoalbuminemia is associated with outcome in a general pediatric population of critically ill patients, taking into account the inflammatory response, disease severity, and nutritional status of the patient.

DESIGN

Analysis of prospectively collected database.

SETTING

PICU of a teaching hospital.

PATIENTS

Two hundred seventy-one patients consecutively admitted. Neonates, patients with chronic liver or kidney disease, inborn errors of metabolism, those who received prior administration of albumin solution, and readmissions were excluded.

MEASUREMENTS AND MAIN RESULTS

Outcome variables were 60-day mortality, probability of ICU discharge at 60 days, and ventilator-free days. Potential exposure variables for the outcome were sex, age, nutritional status, albumin, C-reactive protein and serum lactate at admission, and Pediatric Index of Mortality 2 score. Admission hypoalbuminemia was present in 64.2% of patients. After adjustment for confounding factors, only serum lactate, Pediatric Index of Mortality 2 score, and serum albumin were associated with higher mortality: the increase of 1.0 g/dL in serum albumin at admission resulted in a 73% reduction in the hazard of death (hazard ratio, 0.27; 95% CI, 0.14-0.51; p < 0.001). The increase of 1 g/dL in serum albumin was also independently associated with a 33% rise in the probability of ICU discharge (subhazard ratio, 1.33; 95% CI, 1.07-1.64; p = 0.008) and increased ventilator-free-days (odds ratio, 1.86; 95% CI, 0.56-3.16; p = 0.005).

CONCLUSIONS

Hypoalbuminemia at admission to a PICU is associated with higher 60-day mortality, longer duration of mechanical ventilation, and lower probability of ICU discharge. These associations are independent of the magnitude of inflammatory response, clinical severity, and nutritional status.

Physicochemical Approach to Determine the Mechanism for Acid-Base Disorders in 793 Hospitalized Foals

BACKGROUND

The quantitative effect of strong electrolytes, unmeasured strong anions (UAs), pCO2, and plasma protein concentrations in determining plasma pH can be demonstrated using the physicochemical approach. Plasma anion gap (AG) and strong ion gap (SIG) are used to assess UAs in different species.

HYPOTHESES

Strong ions are a major factor influencing changes in plasma pH of hospitalized foals. AG and SIG accurately predict severe hyper-L-lactatemia ([L-lac(-)] > 7 mmol/L).

ANIMALS

Seven hundred and ninety three hospitalized foals < 7 days old.

METHODS

Retrospective study. The relationship between measured pH and physicochemical variables, and the relationship between plasma [L-lac(-)] and AG and SIG, were determined using regression analyses. Optimal AG and SIG cut points to predict hyper-L-lactatemia were identified using an ROC curve analysis.

RESULTS

Combined, the measured strong ion difference and SIG accounted for 54-69% of the changes in the measured arterial pH of hospitalized foals. AG and SIG were significantly associated with plasma [L-lac(-)] (P < .0001). The receiver operator characteristics (ROC) AUC of AG and SIG for prediction of severe hyper-L-lactatemia were 0.89 (95%CI, 0.8-0.95; P < .0001) and 0.90 (95%CI, 0.81-0.96; P < .0001), respectively. Severe hyper-L-lactatemia was best predicted by AG > 27 mmol/L (sensitivity 80%, 95%CI, 56-94, specificity 85%, 95%CI, 73-93; P < .0001) and SIG <-15 mmol/L (sensitivity 90%, 95%CI, 68-98; specificity 80%; 95%CI, 68-90; P < .0001).

CONCLUSION AND CLINICAL RELEVANCE

Altered concentrations of strong ions (Na(+), K(+), Cl(-)) and UAs were the primary cause of acidemia of hospitalized foals. AG and SIG were good predictors of hyper-L-lactatemia and could be used as surrogate tests.

Postoperative hypoalbuminemia following surgery related to craniosynostosis

BACKGROUND

An episode of postoperative phenytoin toxicity in a patient undergoing surgery related to craniosynostosis highlighted the presence of hypoalbuminemia. We believe that hypoalbuminemia contributed to the altered pharmacokinetics of phenytoin in this case.

OBJECTIVES

To establish the incidence of postoperative hypoalbuminemia in patients undergoing surgery related to craniosynostosis and to investigate the likely etiology.

METHODS

Data on 114 patients undergoing surgery for craniosynostosis over a 2-year period at Oxford Children's Hospital, between May 2011 and May 2013, were retrospectively reviewed. Twenty-two patients were excluded due to incomplete data. This cohort represents the entire population for whom transfusion data had been formally collected at our institution. Preoperative and day 1 postoperative serum albumin levels were collected from the hospital laboratory database. Data regarding blood loss and intra-operative fluid management were reviewed from the anesthetic database. Linear regression analysis was used to establish the relationship between percentage drop in serum albumin with: (i) milliliters per kilogram (ml·kg(-1)) volume of albumin-poor fluids used intra-operatively and (ii) percentage estimated red cell mass loss.

RESULTS

All patients experienced a statistically significant drop in serum albumin. The mean difference in albumin was 17.1 g·l(-1), 95% CI (16.1-18.0) (P < 0.001). Expressed as a percentage, the mean reduction was 37.9% (range 16-61%), SD 9.7. The decrease in albumin was associated with an increase in estimated red cell mass loss (P < 0.001) and an increased ml·kg(-1) volume of albumin-poor fluids given (P < 0.001).

CONCLUSION

Hemodilution due to large volume blood loss and transfusion with albumin-poor fluids is strongly associated with postoperative hypoalbuminemia in patients undergoing surgery related to craniosynostosis. Practitioners should be aware of this risk and the implications of postoperative hypoalbuminemia in this population.

Has Stewart approach improved our ability to diagnose acid-base disorders in critically ill patients?

The Stewart approach-the application of basic physical-chemical principles of aqueous solutions to blood-is an appealing method for analyzing acid-base disorders. These principles mainly dictate that pH is determined by three independent variables, which change primarily and independently of one other. In blood plasma in vivo these variables are: (1) the PCO₂; (2) the strong ion difference (SID)-the difference between the sums of all the strong (i.e., fully dissociated, chemically nonreacting) cations and all the strong anions; and (3) the nonvolatile weak acids (A_tot). Accordingly, the pH and the bicarbonate levels (dependent variables) are only altered when one or more of the independent variables change. Moreover, the source of H⁺ is the dissociation of water to maintain electroneutrality when the independent variables are modified. The basic principles of the Stewart approach in blood, however, have been challenged in different ways. First, the presumed independent variables are actually interdependent as occurs in situations such as: (1) the Hamburger effect (a chloride shift when CO₂ is added to venous blood from the tissues); (2) the loss of Donnan equilibrium (a chloride shift from the interstitium to the intravascular compartment to balance the decrease of A_tot secondary to capillary leak; and (3) the compensatory response to a primary disturbance in either independent variable. Second, the concept of water dissociation in response to changes in SID is controversial and lacks experimental evidence. In addition, the Stewart approach is not better than the conventional method for understanding acid-base disorders such as hyperchloremic metabolic acidosis secondary to a chloride-rich-fluid load. Finally, several attempts were performed to demonstrate the clinical superiority of the Stewart approach. These studies, however, have severe methodological drawbacks. In contrast, the largest study on this issue indicated the interchangeability of the Stewart and conventional methods. Although the introduction of the Stewart approach was a new insight into acid-base physiology, the method has not significantly improved our ability to understand, diagnose, and treat acid-base alterations in critically ill patients.

Hypoalbuminemia in critically sick children

CONTEXT

There is a paucity of data evaluating serum albumin levels and outcome of critically ill-children admitted to intensive care unit (ICU).

AIMS

The aim was to study frequency of hypoalbuminemia and examine association between hypoalbuminemia and outcome in critically ill-children.

SETTINGS AND DESIGN

Retrospective review of medical records of 435 patients admitted to 12 bedded pediatric ICU (PICU).

MATERIALS AND METHODS

Patients with hypoalbuminemia on admission or any time during PICU stay were compared with normoalbuminemic patients for demographic and clinical profile. Effect of albumin infusion was also examined. Odds ratio and 95% confidence interval were calculated using SPSS 16.

RESULTS

Hypoalbuminemia was present on admission in 21% (92 of 435) patients that increased to 34% at the end of 1(st) week and to 37% (164 of 435) during rest of the stay in PICU. Hypoalbuminemic patients had higher Pediatric Risk of Mortality scores (12.9 vs. 7.5, P < 0.001) and prolonged PICU stay (13.8 vs. 6.7 days, P < 0.001); higher likelihood of respiratory failure requiring mechanical ventilaton (84.8% vs. 28.8%, P < 0.001), prolonged ventilatory support, progression to multiorgan dysfunction syndrome (87.8% vs. 16.2%) and risk of mortality (25.6% vs. 17.7%). Though, the survivors among recipients of albumin infusion had significantly higher increase in serum albumin level (0.76 g/dL, standard deviation [SD] 0.54) compared with nonsurvivors (0.46 g/dL, SD 0.44; P = 0.016), albumin infusion did not reduce the risk of mortality.

CONCLUSIONS

Hypoalbuminemia is a significant indicator of mortality and morbidity in critically sick children. More studies are needed to define role of albumin infusion in treatment of such patients.

Clinical usefulness of the serum anion gap

The anion gap in the serum is useful in the interpretation of acid-base disorders and in the diagnosis of other conditions. In the early 1980s, ion-selective electrodes for specific ionic species were introduced for the measurement of serum electrolytes. This new method has caused a shift of the anion gap from 12±4 mEq/L down 6±3 mEq/L. It is worthy for clinicians to understand the range of normal anion gap and the measuring methods for serum sodium and chloride in the laboratories that support their practice. While an increase in the anion gap is almost always caused by retained unmeasured anions, a decrease in the anion gap can be generated by multiple mechanisms.

Ceftriaxone pharmacokinetic properties during continuous veno-veno haemofiltration using an in vitro adult, paediatric and neonatal model

During continuous venoveno haemofiltration (CVVH), extracorporeal drug clearance is dependant on blood flow, ultrafiltration rate, albumin binding, and the drug’s molecular weight and volume of distribution. Drug doses are adjusted assuming reduced drug clearance by the renal system and CVVH. High volume haemofiltration, pre-dilution and different filter membranes can greatly alter drug clearance. Consequently, assessing the adequacy of cephalosporin dosing during CVVH is complex; under- or overdosing may occur. We studied the pharmacokinetic properties of ceftriaxone during CVVH in vitro. Renaflow filters were used to model 6, 20 and 50 kg patients. Each circuit and reservoir was prepared with a known volume of Hartmann’s solution, human albumin solution 4.5% or blood. Pump speed and exchange rate were standardised for weight. Haemosol BO was used as the replacement fluid with 70% pre-dilution. Following paired sampling from the circuit and ultrafiltrate fluid, ceftriaxone was injected into the circuit. Paired samples were taken up to 720 minutes. Ceftraxione concentrations were determined using high performance liquid chromatography (HPLC). Maximum circuit concentrations (Cmax) at 2 minutes for albumin were 3.5, 2.65 and 4.85 mg/l, for blood were 4.5, 6.5 and 5.55 mg/l and for Hartmann’s were 1.65, 2.95 and 3.65 mg/l for 6kg, 20kg and 50kg models. The sieving coefficients (Sc) from blood (ratio of mean concentrations in the ultrafiltrate/circuits samples) were 0.31 and 0.51 with T1/2 (the half life) 62 and 20 minutes in the 6kg and the 20kg circuits, respectively. The data suggest in an in vitro model of ceftriaxone is rapidly cleared during CVVH. Albumin circuits had the lowest Sc and longest terminal T1/2, reflecting protein binding of the drug and suggest ceftriaxone clearance may be more rapid in hypoalbuminaemic patients. The Cmax was lower in the Hartmann circuits, possibly reflecting precipitation of the drug with calcium in this solution.

Physicochemical interpretation of acid-base abnormalities in 54 adult horses with acute severe colitis and diarrhea

BACKGROUND

The quantitative effect of strong electrolytes, pCO2 , and plasma protein concentration in determining plasma pH and bicarbonate concentrations can be demonstrated with the physicochemical approach. Plasma anion gap (AG) and strong ion gap (SIG) are used to assess the presence or absence of unmeasured anions.

HYPOTHESES

The physicochemical approach is useful for detection and explanation of acid-base disorders in horses with colitis. AG and SIG accurately predict hyperlactatemia in horses with colitis.

ANIMALS

Fifty-four horses with acute colitis and diarrhea.

METHODS

Retrospective study. Physicochemical variables were calculated for each patient. ROC curves were generated to analyze sensitivity and specificity of AG and SIG for predicting hyperlactatemia.

RESULTS

Physicochemical interpretation of acid-base events indicated that strong ion metabolic acidosis was present in 39 (72%) horses. Mixed strong ion acidosis and decreased weak acid (hypoproteinemia) alkalosis was concomitantly present in 17 (30%) patients. The sensitivity and specificity of AG and SIG to predict hyperlactatemia (L-lactate > 5 mEq/L) were 100% (95% CI, 66.4-100; P < .0001) and 84.4% (95% CI, 70.5-93.5 P < .0001). Area under the ROC curve for AG and SIG for predicting hyperlactatemia was 0.95 (95% CI, 0.86-0.99) and 0.93 (95% CI, 0.83-0.99), respectively.

CONCLUSION AND CLINICAL RELEVANCE

These results emphasize the importance of strong ions and proteins in the maintenance of the acid-base equilibria. AG and SIG were considered good predictors of clinically relevant hyperlactatemia.

Metabolic acid-base disorders in the critical care unit

The recognition and management of acid-base disorders is a commonplace activity in the critical care unit, and the role of weak and strong acids in the genesis of metabolic acid-base disorders is reviewed. The clinical approach to patients with metabolic alkalosis and metabolic acidosis is discussed in this article.

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.

Effects of hypercapnia on BP in hypoalbuminemic and Nagase analbuminemic rats

STUDY OBJECTIVE

To determine if animals with abnormally low albumin levels are more susceptible to the effects of hypercapnia on BP compared to normal animals.

DESIGN

Prospective, controlled laboratory experiment.

SETTING

University research laboratory.

ANIMALS

Eighteen male Sprague-Dawley rats: 6 rats 10 to 12 weeks old (young Sprague-Dawley [YSD]), 6 rats 6 to 9 months old (old Sprague-Dawley [OSD]), and 6 rats 10 to 12 weeks old (Nagase analbuminemic mutant Sprague-Dawley [NAR]).

METHODS

Under general anesthesia and paralysis, we varied the Paco(2) by changing the respiratory rate on mechanical ventilation. Mean arterial pressure (MAP) was monitored in a continuous fashion. We obtained arterial blood for blood gas and electrolyte analysis, and nitric oxide (NO) production.

RESULTS

OSD rats had reduced serum albumin, while NAR rats were analbuminemic. Although NAR animals had a decreased buffer capacity compared to age-matched control animals (0.010 vs 0.013, p < 0.05), the MAP decreased in an identical fashion in all three groups. NO production increased with hypercapnia but was similar in all three groups. However, NAR rats had consistently higher plasma strong ion gap (2.8 to 4.1 mEq/L greater) compared to either YSD or OSD rats (p < 0.01), and baseline strong ion difference (mean +/- SD) was significantly lower in NAR rats (28.7 +/- 2.1 mEq/L) compared to either YSD rats (33.0 +/- 5.1 mEq/L) or OSD rats (31.2 +/- 5.1 mEq/L) [p < 0.05].

CONCLUSIONS

These findings suggest that analbuminemic or hypoalbuminemic rats are not more susceptible to hypercapnia-induced hemodynamic instability. Baseline values for apparent strong ion difference are lower in NA rats consistent with a reduced buffer base resulting from analbuminemia.

Comparison of three different methods of evaluation of metabolic acid-base disorders

OBJECTIVES

The Stewart approach states that pH is primarily determined by Pco2, strong ion difference (SID), and nonvolatile weak acids. This method might identify severe metabolic disturbances that go undetected by traditional analysis. Our goal was to compare diagnostic and prognostic performances of the Stewart approach with a) the traditional analysis based on bicarbonate (HCO3) and base excess (BE); and b) an approach relying on HCO3, BE, and albumin-corrected anion gap (AGcorrected).

DESIGN

Prospective observational study.

SETTING

A university-affiliated hospital intensive care unit (ICU).

PATIENTS

Nine hundred thirty-five patients admitted to the ICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The Stewart approach detected an arterial metabolic alteration in 131 (14%) of patients with normal HCO3- and BE, including 120 (92%) patients with metabolic acidosis. However, 108 (90%) of these patients had an increased AGcorrected. The Stewart approach permitted the additional diagnosis of metabolic acidosis in only 12 (1%) patients with normal HCO3, BE, and AGcorrected. On the other hand, the Stewart approach failed to identify 27 (3%) patients with alterations otherwise observed with the use of HCO3-, BE, and AGcorrected (16 cases of acidosis and 11 of alkalosis). SID and BE, and strong ion gap (SIG) and AGcorrected, were tightly correlated (R2 = .86 and .97, p < .0001 for both) with narrow 95% limits of agreement (8 and 3 mmol/L, respectively). Areas under receiver operating characteristic curves to predict 30-day mortality were 0.83, 0.62, 0.61, 0.60, 0.57, 0.56, and 0.67 for Sepsis-related Organ Failure Assessment (SOFA) score, SIG, AGcorrected, SID, BE, HCO3-, and lactates, respectively (SOFA vs. the rest, p < .0001).

CONCLUSIONS

In this large group of critically ill patients, diagnostic performance of the Stewart approach exceeded that of HCO3- and BE. However, when AGcorrected was included in the analysis, the Stewart approach did not offer any diagnostic or prognostic advantages.

Measurement of serum free cortisol shows discordant responsivity to stress and dynamic evaluation

CONTEXT

Routinely available assays of adrenal function measure serum total cortisol (TC) and not the biologically active free cortisol (FC). However, there are few data on FC levels during surgical stress and in response to standard pharmacological tests.

OBJECTIVE

Our objective was to evaluate TC and FC levels in different states of physical stress.

DESIGN AND SETTING

We conducted a prospective observational study in a university hospital.

PARTICIPANTS AND MAIN OUTCOME MEASURES

We measured TC and FC levels in 64 patients: group A, 17 healthy controls without stress; group B, 23 medical patients with moderate stress; and group C, 24 surgical patients undergoing coronary bypass grafting. Cortisol levels in group C were measured basally and at several time points thereafter and were compared with responsivity to a pharmacological dose of ACTH. FC was measured using equilibrium dialysis.

RESULTS

In group C patients after extubation, the relative increase above basal FC was higher than the increase in TC levels (399 +/- 266 vs. 247 +/- 132% of initial values, respectively; mean +/- sd; P = 0.02) and then fell more markedly, FC levels falling to 67 +/- 49% and TC levels to 79 +/- 36% (P = 0.04). After ACTH stimulation, TC levels increased to 680 +/- 168 nmol/liter, which was similar to the increase with major stress (811 +/- 268 nmol/liter). In contrast, FC levels increased to 55 +/- 16 nmol/liter after ACTH stimulation but significantly greater with surgical stress to 108 +/- 56 nmol/liter (P < 0.001).

CONCLUSION

The more pronounced increase in FC seen during stress as compared with the ACTH test suggests that this test does not adequately anticipate the FC levels needed during severe stress.

Treffpunkt Stewart

OBJECTIVE

Development of a two-buffer model which simulates the acid-base properties of blood and allows comparison of the different acidbase concepts according to Stewart and to Siggaard-Andersen.

METHODS

The two-buffer model consisted of different aqueous solutions of bicarbonate/CO(2) (pCO(2), sCO(2), pK(1)), HEPES buffer (A(tot), pK(a)) and electrolytes. These were used to calculate the pH from the independent variables according to Stewart - strong ion difference (SID), pCO(2) and total concentration of the weak acids (A(tot)) - from which all other dependent variables (cHCO(3)(-), cA(-), BB, BE) were obtained and compared with the measured values.

RESULTS

The normal pH (7.408) was calculated from the normal values for SID (48 mmol/l), pCO(2) (40 mmHg) and A(tot) (45.2 mmol/l) and agreed perfectly with the measured value (7.409+/-0.001). This was also valid for all calculated and measured pH values when the SID was varied: non-respiratory alkalosis ( upward arrow) or acidosis ( downward arrow), pCO(2):respiratory acidosis ( upward arrow) or alkalosis ( downward arrow) and A(tot):hyperproteinemic acidosis ( upward arrow) or hypoproteinemic alkalosis ( downward arrow) were varied and the sum of the buffer bases (BB) was always equal to the SID. All changes and hence BE were also equal, providing that A(tot) was normal. This was not the case, however, if A(tot) was outside the normal range, when BE was then the difference from the normal BB at the respective reference point. Whereas the deviation of the measured pCO(2) was acceptable (1.74+/-0.86 mmHg), this was not the case for the SID (-6.18+/-3.58 mmol/l) calculated from the measured ion concentrations (Na, K, Ca, Cl).

CONCLUSIONS

Despite controversial discussions, both concepts are much closer than might be expected. Whereas in the Stewart approach the focus of analysis is on plasma, with the Siggaard-Andersen approach it is on blood. Hence, a combined analysis of the blood gases (pH, pCO(2), pO(2), sO(2), cHb, BE) and of the strong ion gap (SIG) may be useful.

Essentials of laboratory medicine for the nephrology clinician

The purpose of this review is to compile and bring to the attention of the pediatric nephrology community various aspects of laboratory medicine pertinent to nephrology. The review addresses different aspects in laboratory medicine that should be taken into account during interpretation of a test result, such as methodological and analytical issues, statistical considerations and the biological interpretation of a test result in the context of the clinical setting. An understanding of the considerations and limitations in laboratory medicine will be helpful to the pediatric nephrologist when ordering and interpreting biochemical tests.

CRITICAL CARE ISSUES FOR THE NEPHROLOGIST: Acid-base Disturbances in the Intensive Care Unit: Metabolic Acidosis

This article will discuss metabolic acidosis and, to a lesser extent, metabolic alkalosis in the ICU setting. A classification and clinical approach will be the focus.

Risk factors for death among critically ill patients with acute renal failure

CONTEXT AND OBJECTIVE

Acute renal failure is a common medical problem, with a high mortality rate. The aim of this work was to investigate the risk factors for death among critically ill patients with acute renal failure.

DESIGN AND SETTING

Retrospective cohort at the intensive care unit of Hospital Universitário Walter Cantídio, Fortaleza.

METHODS

Survivors and non-survivors were compared. Univariate and multivariate analyses were performed to establish risk factors for death.

RESULTS

Acute renal failure occurred in 128 patients (33.5%), with mean age of 49 +/- 20 years (79 males; 62%). Death occurred in 80 (62.5%). The risk factors most frequently associated with death were hypotension, sepsis, nephrotoxic drug use, respiratory insufficiency, liver failure, hypovolemia, septic shock, multiple organ dysfunction, need for vasoactive drugs, need for mechanical ventilation, oliguria, hypoalbuminemia, metabolic acidosis and anemia. There were negative correlations between death and: prothrombin time, hematocrit, hemoglobin, systolic blood pressure, diastolic blood pressure, arterial pH, arterial bicarbonate and urine volume. From multivariate analysis, the independent risk factors for death were: need for mechanical ventilation (OR = 3.15; p = 0.03), hypotension (OR = 3.48; p = 0.02), liver failure (OR = 5.37; p = 0.02), low arterial bicarbonate (OR = 0.85; p = 0.005), oliguria (OR = 3.36; p = 0.009), vasopressor use (OR = 4.83; p = 0.004) and sepsis (OR = 6.14; p = 0.003).

CONCLUSIONS

There are significant risk factors for death among patients with acute renal failure in intensive care units, which need to be identified at an early stage for early treatment.

Total phenytoin concentrations do not accurately predict free phenytoin concentrations in critically ill children

OBJECTIVE

To determine the relationship between estimated free, measured free, and measured total phenytoin levels in critically ill pediatric patients, assess the utility of the Sheiner-Tozer equation in predicting free phenytoin levels, and identify comedications that may influence phenytoin binding or confound attempts to maintain therapeutic concentrations.

DESIGN

Retrospective chart review.

SETTING

Twenty-four-bed medical-surgical pediatric intensive care unit.

PATIENTS

Sixty critically ill pediatric patients receiving phenytoin for treatment of seizures in a large multidisciplinary intensive care unit.

INTERVENTIONS AND MAIN RESULTS

The linear correlation between free and total phenytoin concentrations was moderate (r = .795), but the mean difference between actual free concentrations and those estimated from total concentrations using the Sheiner-Tozer equation was -0.31 +/- 0.5 microg/mL (95% confidence interval, -1.3 to 0.7). This difference was of concern, as 10% of patients had toxic free levels (>2 microg/mL) when simultaneously measured total levels were therapeutic (<20 microg/mL). The mean free/total phenytoin ratio was 0.13 +/- 0.07 (range, 0.06-0.42) and varied considerably among patients. Free fractions were particularly elevated in children whose serum albumin concentrations were <2.5 g/dL (0.22, p < .001). However, the relationship between free phenytoin and serum albumin concentration appeared to be nonlinear. Coadministration of valproic acid and cefazolin also increased free fraction (p < .001).

CONCLUSIONS

Measured total phenytoin concentrations are unreliable for directing therapy in critically ill children. In part, this is because phenytoin binding shows greater variability in this population than has been reported in adults. This phenomenon is exacerbated by coadministration of other highly protein-bound drugs. Instead, free phenytoin concentrations should be routinely measured in critically ill children to prevent possible intoxications and ensure therapeutic dosing. Corrections using the Sheiner-Tozer equation were unreliable.

Quantitative acid-base physiology using the Stewart model. Does it improve our understanding of what is really wrong?

Traditional theories of acid-base balance are based on the Henderson-Hasselbalch equation to calculate proton concentration. The recent revival of quantitative acid-base physiology using the Stewart model has increased our understanding of complicated acid-base disorders, but has also led to several new controversies. With the help of three patient histories, we show that the Henderson-Hasselbalch equation should be regarded as a simplified version of the more general Stewart model and not as something completely different. Therefore, both models may be useful at the bedside.

Hyperchloraemic metabolic acidosis following open cardiac surgery

AIMS

To describe acid-base derangements in children following open cardiac surgery on cardiopulmonary bypass (CPB), using the Fencl-Stewart strong ion approach.

METHODS

Prospective observational study set in the paediatric intensive care unit (PICU) of a university children's hospital. Arterial blood gas parameters, serum electrolytes, strong ion difference, strong ion gap (SIG), and partitioned base excess (BE) were measured and calculated on admission to PICU.

RESULTS

A total of 97 children, median age 57 months (range 0.03-166), median weight 14 kg (range 2.1-50), were studied. Median CPB time was 80 minutes (range 17-232). Predicted mortality was 2% and there was a single non-survivor. These children showed mild metabolic acidosis (median standard bicarbonate 20.1 mmol/l, BE -5.1 mEq/l) characterised by hyperchloraemia (median corrected Cl 113 mmol/l), and hypoalbuminaemia (median albumin 30 g/l), but no significant excess unmeasured anions or cations (median SIG 0.7 mEq/l). The major determinants of the net BE were the chloride and albumin components (chloride effect -4.8 mEq/l, albumin effect +3.4 mEq/l). Metabolic acidosis occurred in 72 children (74%) but was not associated with increased morbidity. Hyperchloraemia was a causative factor in 53 children (74%) with metabolic acidosis. Three (4%) hyperchloraemic children required adrenaline for inotropic support, compared to eight children (28%) without hyperchloraemia. Hypoalbuminaemia was associated with longer duration of inotropic support and PICU stay.

CONCLUSIONS

In these children with low mortality following open cardiac surgery, hypoalbuminaemia and hyperchloraemia were the predominant acid-base abnormalities. Hyperchloraemia was associated with reduced requirement for adrenaline therapy. It is suggested that hyperchloraemic metabolic acidosis is a benign phenomenon that should not prompt escalation of haemodynamic support. By contrast, hypoalbuminaemia, an alkalinising force, was associated with prolonged requirement for intensive care.

Clinical review: the meaning of acid-base abnormalities in the intensive care unit part I - epidemiology

Acid-base abnormalities are common in critically ill patients. Our ability to describe acid-base disorders must be precise. Small differences in corrections for anion gap, different types of analytical processes, and the basic approach used to diagnose acid-base aberrations can lead to markedly different interpretations and treatment strategies for the same disorder. By applying a quantitive acid-base approach, clinicians are able to account for small changes in ion distribution that may have gone unrecognized with traditional techniques of acid-base analysis. Outcome prediction based on the quantitative approach remains controversial. This is in part due to use of various technologies to measure acid-base variables, administration of fluid or medication that can alter acid-base results, and lack of standardized nomenclature. Without controlling for these factors it is difficult to appreciate the full effect that acid-base disorders have on patient outcomes, ultimately making results of outcome studies hard to compare.

Validation of a method to partition the base deficit in meningococcal sepsis: a retrospective study

Introduction

The base deficit is a useful tool for quantifying total acid–base derangement, but cannot differentiate between various aetiologies. The Stewart–Fencl equations for strong ions and albumin have recently been abbreviated; we hypothesised that the abbreviated equations could be applied to the base deficit, thus partitioning this parameter into three components (the residual being the contribution from unmeasured anions).

Methods

The two abbreviated equations were applied retrospectively to blood gas and chemistry results in 374 samples from a cohort of 60 children with meningococcal septic shock (mean pH 7.31, mean base deficit -7.4 meq/L). Partitioning required the simultaneous measurement of plasma sodium, chloride, albumin and blood gas analysis.

Results

After partitioning for the effect of chloride and albumin, the residual base deficit was closely associated with unmeasured anions derived from the full Stewart–Fencl equations (r² = 0.83, y = 1.99 – 0.87x, standard error of the estimate = 2.29 meq/L). Hypoalbuminaemia was a common finding; partitioning revealed that this produced a relatively consistent alkalinising effect on the base deficit (effect +2.9 ± 2.2 meq/L (mean ± SD)). The chloride effect was variable, producing both acidification and alkalinisation in approximately equal proportions (50% and 43%, respectively); furthermore the magnitude of this effect was substantial in some patients (SD ± 5.0 meq/L).

Conclusion

It is now possible to partition the base deficit at the bedside with enough accuracy to permit clinical use. This provides valuable information on the aetiology of acid–base disturbance when applied to a cohort of children with meningococcal sepsis.

The role of initial monitoring of routine biochemical nutritional markers in critically ill children

AIMS

The objectives of this study were to determine whether abnormal values of routine laboratory parameters at admission predict outcome and changes in anthropometric parameters in critically ill children during intensive care unit (ICU) stay and to discuss the clinical implications of abnormalities.

STUDY DESIGN

This is a prospective descriptive study in a tertiary multidisciplinary pediatric ICU. Serum urea, albumin, triglycerides and magnesium were measured in samples obtained from 105 children (age, 7 days-16 years) within the first 24 h after their admission. The prevalences of abnormalities in these parameters as well as their possible association with outcome (length of stay, days on mechanical ventilation) and changes in nutritional status (changes in S.D. scores for weight, mid upper arm circumference and calf circumference) between admission and discharge were assessed.

RESULTS

Prevalences of hypomagnesemia, hypertriglyceridemia, uremia and hypoalbuminemia were 20%, 25%, 30% and 52%, respectively, with no significant associations between the different disorders. Except for uremia, no significant association was found between abnormalities in biochemical parameters and changes in S.D. scores of anthropometric measurements. Children with uremia showed larger declines in S.D. scores for weight and arm circumference between admission and discharge than children without uremia did. Children with hypertriglyceridemia had longer ventilator dependence (P<.01) and length of stay (P<.001) than children with normal triglyceride levels upon admission had.

CONCLUSIONS

Abnormalities in routine nutritional laboratory parameters were frequently noted in critically ill children at admission. Detection of abnormalities was not predictive of changes in anthropometric parameters during ICU admission but can be important in individualizing nutritional support.

Clinical acid-base pathophysiology: disorders of plasma anion gap

The plasma anion gap is a frequently used parameter in the clinical diagnosis of a variety of conditions. The commonest application of the anion gap is to classify cases of metabolic acidosis into those that do and those that do not leave unmeasured anions in the plasma. While this algorithm is useful in streamlining the diagnostic process, it should not be used solely in this fashion. The anion gap measures the difference between the unmeasured anions and unmeasured cations and thus conveys much more information to the clinician than just quantifying anions of strong acids. In this chapter, the significance of the anion gap is emphasized and several examples are given to illustrate a more analytic approach to using the clinical anion gap; these include disorders of low anion gap, respiratory alkalosis and pyroglutamic acidosis.