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Surveys provide evidence on practice, attitudes, and knowledge. However, conducting good survey research is harder than it looks. The authors aim to provide guidance to both researchers and readers in conducting and interpreting survey research. Like all research, surveys should have clear research question(s) using the smallest possible number of high-quality, essential, survey questions (items) that will interest the target population. Both researchers and readers should put themselves in the position of the respondents. The survey questions should provide reproducible results (reliable), measure what they are supposed to measure (valid), and take less than 10 min to answer. Good survey research reports provide results with valid and reliable answers to the research question with an adequate response rate (at least 40%) and adequate precision (margin of error ideally 5% or less). Possible biases among those who did not respond (nonresponders) must be carefully analyzed and discussed. Quantitative results can be combined with qualitative results in mixed-methods research to provide greater insight. [ABSTRACT FROM AUTHOR]

BACKGROUND: In an incidental finding, during a study of plasma chemistry after crystalloid infusion, participants reported subjective cognitive changes, particularly slower thinking, after saline but not Hartmann's (Ringer's lactate) solution. The authors tested the hypothesis that saline infusion would produce greater adverse cognitive changes than Plasmalyte infusion. METHODS: The authors conducted a randomized, cross-over, multiple blinded study of healthy adult volunteers. On separate days, participants received 30 ml/kg over 1 h of either 0.9% saline or Plasmalyte with the order randomly allocated. Plasma chemistry was tested on venous samples. As part of a battery of cognitive tests our primary endpoint was the reaction time index after infusion. RESULTS: The authors studied 25 participants. Plasma chloride was greater after saline than after Plasmalyte: mean difference 5.4 mM (95% CI, 4.1-6.6 mM; P < 0.001). Saline was also associated with greater metabolic acidosis: base-excess 2.5 mM more negative (95% CI, 1.9-3.0 mM more negative; P < 0.001). There was no evidence of a difference in the reaction time index between the two interventions: mean reaction time index 394 ms (SD, 72) after saline versus 385 ms (SD, 55) after Plasmalyte. Difference: saline 9 ms slower (95% CI, 30 ms slower to 12 ms faster; P = 0.39). There were minimal differences in the other cognitive and mood tests. CONCLUSIONS: Despite expected differences in plasma chemistry, the authors found that measures of cognition did not differ after infusions of Plasmalyte or saline. [ABSTRACT FROM AUTHOR]

The article comments on the paper "Contribution of various metabolites to the "unmeasured " anions in critically ill patients with metabolic acidosis," by M. Moviat and colleagues. According to the author, the paper highlights that clinical researchers have greater access to sophisticated analytic techniques. The author notes the study finds that a quantitative analysis of plasma levels of amino acids, uric acid, and metabolic organic acids could account for 8% of the estimated strong ion gap.

Purpose of Review: To outline perioperative risk factors for postoperative mortality in older patients, the relationship of these factors with long-term mortality, and to examine possible strategies to reduce mortality., Recent Findings: For patients aged 70 years and over 30-day mortality is about 6%, whereas 20% are likely to have at least one complication during their hospital stay. The mortality risk increases by 10% for every year after age 70. Mortality is also strongly associated with preoperative status and postoperative complications, particularly systemic inflammation and renal impairment. Unplanned postoperative intensive care unit admission is an important predictor for mortality. Requirement for postoperative vasopressors or inotropes is associated with 50% mortality in patients aged 80 years or more. Early postoperative complications are likely to be associated with an increased long-term (a year or more later) mortality. Strategies such as critical care outreach may decrease both 30-day and long-term mortality., Summary: Strategies are needed to prevent, or at least adequately manage, complications in elderly patients. Agreed international definitions for risks and complications can help in assessing risks and benefits.

Background: We tested the hypothesis that the difference between indirect and direct sodium assays would be related to the plasma albumin concentration. Further, we proposed that differences between indirect and direct chloride assays might be explained by interference from other plasma constituents, particularly bicarbonate, and possibly albumin., Methods: We studied 300 critically ill patients at the time of admission to the intensive care unit (ICU) and compared each patient's plasma sodium and chloride measurements from a central laboratory assay (indirect electrode) and an ICU blood gas machine assay (direct electrode)., Results: The central laboratory sodium measurement was, on average, 2.1 mmol/L more than the ICU assay, limits of agreement 1.8-2.4 mmol/L greater, P < 0.001. The central laboratory chloride measurement was, on average, 1 mmol/L less than the ICU assay (limits of agreement 1.3-0.7 mmol/L less, P < 0.001). All correlations between the assay differences and plasma constituents were weak except for a moderately strong correlation between differences in sodium measurements and albumin. The difference in plasma sodium concentration between the assays (central laboratory - ICU) increased as the plasma concentration albumin decreased (difference = 6.2-0.16 albumin (g/L); P < 0.001, r = -0.46, r(2) = 0.22)., Conclusions: The central laboratory and ICUs assays are analytically, statistically, and clinically different for both sodium and chloride. Unless taken into account, the differences could be large enough in hypoalbuminemic populations (such as critically ill patients) to affect clinical diagnosis and decision making.

Decreases in plasma bicarbonate are associated with hyperchloremic acidosis and lactic acidosis. According to the Stewart approach to acid-base physiology, the strong-ion difference regulates plasma bicarbonate, with chloride and lactate being the only strong anions routinely measured in clinical chemistry. We hypothesized that the plasma strong-ion difference, both with and without lactate, would have a stronger association with plasma bicarbonate than plasma chloride alone would have with bicarbonate. We used plasma acid-base data from 300 critically ill patients. The correlation with bicarbonate became progressively weaker (P < 0.001): all measured strong ions, r = 0.60; measured strong ions without lactate, r = 0.42; chloride alone, r = -0.27. In a subgroup of 26 patients with traditional hyperchloremic acidosis (base excess < -2 mmol/L and anion gap <17 mmol/L), the measured strong-ion difference (without lactate) had a stronger correlation (P < 0.001) with bicarbonate than chloride had: r = 0.85 versus r = -0.60. We conclude that hyperchloremic acidosis and lactic acidosis are strong-ion acidoses. Hyperchloremia should be viewed relative to the plasma strong cations. A practical conclusion is that both managing and preventing acid-base disorders with IV fluid therapy involves manipulating each of the plasma strong ions, particularly sodium and chloride.

Purpose of Review: For 20 years, an alternative view of the universe has been available for acid-base physiology. The Stewart approach emphasizes mathematically independent and dependent variables. With the Stewart approach bicarbonate and hydrogen ions are dependent variables that represent the effects rather than the causes of acid-base derangements. Neither bicarbonate nor pH can be regulated directly; rather they are controlled by the independent variables. In plasma there are three independent variables: the partial pressure of carbon dioxide, strong ion difference, and weak acids. In plasma, sodium and chloride are the principal strong ions, and albumin is the principal weak acid. Critically ill patients often have changes in these variables., Recent Findings: Recent studies have examined various aspects of the Stewart approach, including the effects of buffers and haemofiltration as well as bedside assessment of a patient's acid-base status. While sodium bicarbonate increases the strong ion difference by increasing plasma sodium, tris-hydroxymethyl aminomethane acts by increasing plasma weak base concentration and weak cations. Several studies support correcting the anion gap for changes in albumin (and even phosphate). One study raises a cautionary note on the poor agreement between central laboratory and point-of-care measurements of important biochemical variables, including plasma sodium and chloride., Summary: The Stewart approach to acid-base physiology continues to develop as a comprehensive method to diagnose and manage acid-base disorders.