A comparison between direct and calculated oxygen saturation in intensive care.

We investigated the discrepancy between calculated and spectrophotometrically determined oxygen saturation, and the corresponding effect of this difference on calculated oxygen uptake in 46 arterial-venous sample pairs from 28 critically ill patients. The range of discrepancy between the two methods showed limits of agreement (mean +/- 2SD) of -2.26 to +0.70% for arterial samples, and -5.52 to +4.96% for the corresponding venous samples. The effect of this variation on oxygen uptake showed limits of agreement of -43.2 to 36.0 ml/min when the discrepancy between oxygen uptake, calculated using the direct measure of saturation, was compared to that using the derived value. Multiple regression analysis showed that PCO2, temperature and 2,3 diphosphoglycerate were significantly related to saturation discrepancy with an R-squared value of 0.64 (P < 0.0001) for a subgroup of 25 venous samples. The precision of the PO2 electrode was also found to be a major contributory component to the discrepancies, particularly at venous PO2 values. Thus the use of calculated oxygen saturation may result in clinically significant inaccuracies in the assessment of some oxygen flux variables.

Intensive care treatment of patients with bleeding esophageal varices: results, predictors of mortality, and predictors of the adult respiratory distress syndrome.

OBJECTIVES: To determine the factors predicting mortality from bleeding esophageal varices and to examine the possibility of an association between the development of adult respiratory distress syndrome (ARDS) and the use of ethanolamine oleate as an esophageal variceal sclerosant. DESIGN: Retrospective review. SETTING: ICU in a teaching hospital. PATIENTS: A total of 101 patients with endoscopically confirmed bleeding esophageal varices were admitted on 124 occasions from 1985 to 1990. Mean age was 50 +/- 13.5 (SD) yrs. There were 62 males and 39 females. Using the Child-Pugh classification, 21.8% patients were class A, 38.6% class B, and 39.6% class C. Mean ICU and hospital lengths of stay were 5.4 +/- 5.1 and 19.6 +/- 16.1 days, respectively. Mean Acute Physiology and Chronic Health Evaluation (APACHE II) score on admission was 16.5 +/- 7.6. INTERVENTIONS: Endoscopic variceal sclerotherapy was performed in 99 (79.8%) of 124 ICU admissions in the 101 patients. Esophageal balloon tamponade was performed in 64 (51.6%) and a vasopressin infusion was administered in 47 (37.9%) of the 124 ICU admissions. A variety of factors was studied to find predictors of mortality and the development of ARDS. RESULTS: Forty-eight (48.5%) of the 101 patients died during the hospital stay. Independent predictors of mortality (by stepdown logistic regression) were total volume of ethanolamine oleate injected during sclerotherapy, multiple blood transfusions, Glasgow Coma Scale score, International normalized ratio for prothrombin test, and the presence of circulatory shock on ICU admission. Age, sex, Child-Pugh score, APACHE II score, serum bilirubin, albumin, and creatinine concentrations, use of esophageal balloon tamponade or vasopressin infusion, sepsis, pneumonia, congestive cardiac failure, aspiration, and ARDS were not statistically independent predictors of outcome. There was no difference in the mortality rates for the various causes of liver disease. Pulmonary complications occurred in 44 (43.6%) patients; sepsis occurred in 31 (25%) patients. ARDS developed in 14 patients (11.3% admissions, 13.9% patients). Statistically independent predictors of ARDS were sepsis, low plasma albumin concentration, use of esophageal balloon tamponade, and more than one sclerotherapy session. The volume and type of sclerosant used were not statistically independent predictors. CONCLUSIONS: Outcome is poor for patients with bleeding esophageal varices requiring ICU admission and is related to the severity of liver failure, the degree of blood loss, and failure of therapy to stop the bleeding. The findings do not support an association between the use of the sclerosant ethanolamine and the development of ARDS.

Alterations in anion gap following cardiopulmonary bypass.

OBJECTIVES: To evaluate the changes in the anion gap and their relation to hyperlactatemia and alterations in plasma proteins after cardiopulmonary bypass. DESIGN: Prospective study. SETTING: Cardiothoracic intensive therapy unit. PATIENTS: One hundred eleven consecutive patients after cardiopulmonary bypass. MEASUREMENTS AND MAIN RESULTS: Data were collected before cardiopulmonary bypass and every 6 hrs for 24 hrs after cardiopulmonary bypass. Results were analyzed for the entire cohort and for hyperlactatemic subgroups. The major finding of this study was that the anion gap decreased significantly at all sampling periods relative to precardiopulmonary bypass values, despite the presence of clinically important hyperlactatemia. No correlation between the decrease in plasma protein concentrations and the decrease in anion gap could be demonstrated. CONCLUSIONS: The decrease in anion gap after cardiopulmonary bypass appears to represent a balance between the influences of increased serum chloride and lactate concentrations and reduced plasma protein concentrations. This analysis demonstrates the limitations of the anion gap in the evaluation of a metabolic acidosis after cardiopulmonary bypass.