Tighter precision target required for lactate testing in patients with lactic acidosis.

BACKGROUND: Allowable analytic errors are generally based on biologic variation in normal, healthy subjects. Some analytes like blood lactate have low concentrations in healthy individuals and resultant allowable variation is large when expressed as a coefficient of variation (CV). In Ricós' compendium of biologic variation, the relative pooled intra-individual lactate variation (si) averages 27% and the desirable imprecision becomes 13.5%. We derived biologic variability (sb) from consecutive patient data and demonstrate that sb of lactate is significantly lower. METHODS: A data repository provided lactate results measured over 18 months in the General Systems intensive care unit (ICU) at the University of Alberta Hospital in Edmonton, Canada. In total 54,000 lactate measurements were made on two point-of-care Radiometer 800 blood gas systems operated by Respiratory Therapy. The standard deviations of duplicates (SDD) were tabulated for the intra-patient lactates that were separated by 0-1, 1-2...up to 16 h. The graphs of SDD vs. time interval were approximately linear; the y-intercept provided by the linear regression represents the sum of sb and short-term analytic variation (sa):y0=(sa²+sb²)½. The short-term sa was determined from imprecisions provided by Radiometer and confirmed with onsite controls. The derivation of sb was performed for multiple patient ranges of lactate. RESULTS: The relative desirable lactate imprecision for patients with lactic acidosis is about half that of normal individuals. CONCLUSIONS: As such, evaluations of lactate measurements must use tighter allowable error limits.

A case of sodium chlorite toxicity managed with concurrent renal replacement therapy and red cell exchange.

INTRODUCTION: Sodium chlorite is a powerful oxidizing agent with multiple commercial applications. We report the presentation and management of a single case of human toxicity of sodium chlorite. CASE REPORT: A 65-year-old man presented to hospital after accidentally ingesting a small amount of a sodium chlorite solution. His principal manifestations were mild methemoglobinemia, severe oxidative hemolysis, disseminated intravascular coagulation, and anuric acute kidney injury. He was managed with intermittent hemodialysis, followed by continuous venovenous hemofiltration for management of acute kidney injury and in an effort to remove free plasma chlorite. Concurrently, he underwent two red cell exchanges, as well as a plasma exchange, to reduce the burden of red cells affected by chlorite. These interventions resulted in the cessation of hemolysis with stabilization of serum hemoglobin and platelets. The patient survived and subsequently recovered normal renal function. DISCUSSION: This is only the second case of sodium chlorite intoxication reported in the medical literature and the first to report the use of renal replacement therapy in combination with red cell exchange in its management.

Nutrition and sepsis.

The effect of nutritional support in critically ill patients with sepsis has received much attention in recent years. However, many of the studies have produced conflicting results. As for all critically ill patients, nutritional support, preferably via the enteral route, should be commenced once initial resuscitation and adequate perfusion pressure is achieved. Where enteral feeding is impossible or not tolerated, parenteral nutrition (either as total or complimentary therapy) may safely be administered. Most positive studies relating to nutritional support and sepsis have been in the setting of sepsis prevention. Thus, the administration of standard nutrition formulas to critically ill patients within 24 h of injury or intensive care unit admission may decrease the incidence of pneumonia. Both arginine-supplemented enteral diets, given in the perioperative period, and glutamine-supplemented parenteral nutrition have been shown to decrease infections in surgical patients. Parenteral fish oil lipid emulsions as well as probiotics given in the perioperative period may also reduce infections in patients undergoing major abdominal operations, such as liver transplantation. There is little support at the present time for the positive effect of specific pharmaconutrients, in particular fish oil, probiotics, or antioxidants, in the setting of established sepsis. More studies are clearly required on larger numbers of more homogeneous groups of patients.

Accuracy of glycemic measurements in the critically ill.

BACKGROUND: Recent evidence emphasizes the importance of maintaining normoglycemia in critically ill patients to reduce morbidity and mortality. Different analytical methods of varying accuracy exist for obtaining and measuring blood glucose in critically ill patients. The purpose of this study was to determine if there were differences in blood glucose values measured by whole blood capillary and arterial samples using three different bedside blood glucose meters and a blood gas analyzer as compared to a reference blood glucose analyzer. METHODS: Sixty subjects were recruited from a university hospital medical/surgical intensive care unit. Matching capillary and arterial samples were analyzed by a clinical blood glucose reference analyzer (YSI, Yellow Springs Instrument, Yellow Springs, OH) and three blood glucose meters (Lifescan [Milpitas, CA] SureStepFlexx, Roche [Indianapolis, IN] Accu-Chek Inform, and Abbott [Alameda, CA] FreeStyle). Additionally, the arterial samples were analyzed by a point-of-care blood gas analyzer (Chiron 865, Bayer, Tarrytown, NY). RESULTS: Data analysis included repeated-measures analysis of variance, Consensus Error Grid analysis, Bland-Altman plots, and numerical estimates of inaccuracy. With capillary samples there were high numbers of errors as compared to the reference instrument. Measurement of blood glucose with arterial samples demonstrates a higher degree of accuracy. With arterial samples, the Abbott FreeStyle blood glucose meter and the blood gas analyzer glucose exhibited the lowest median and mean relative absolute deviation. CONCLUSION: In critically ill adult patients, measurement of blood glucose using arterial samples is recommended. Using arterial blood, the Abbott FreeStyle blood glucose meter and the point-of-care blood gas analyzer (Bayer Chiron 865) were shown to be highly accurate instruments to measure arterial blood glucose.