Objective:To determine if peripheral venous blood gas values for pH, partial pressure of carbon dioxide (PCO2) and the resultant calculated bicarbonate (HCO3) predict arterial values accurately enough to replace them in a clinical setting.Methods:This prospective observational study was performed in a university tertiary care emergency department from June to December 1998. Patients requiring arterial blood gas analysis were enrolled and underwent simultaneous venous blood gas sampling. The following data were prospectively recorded: age, sex, presenting complaint, vital signs, oxygen saturation, sample times, number of attempts and indication for testing. Correlation coefficients and mean differences with 95% confidence intervals (CIs) were calculated for pH,PCO2and HCO3. A survey of 45 academic emergency physicians was performed to determine the minimal clinically important difference for each variable.Results:The 218 subjects ranged in age from 15 to 90 (mean 60.4) years. The 2 blood samples were drawn within 10 minutes of each other for 205 (96%) of the 214 patients for whom data on timing were available. Pearson’s product–moment correlation coefficients between arterial and venous values were as follows: pH, 0.913;PCO2, 0.921; and HCO3, 0.953. The mean differences (and 95% CIs) between arterial and venous samples were as follows: pH, 0.036 (0.030–0.042);PCO2, 6.0 (5.0–7.0) mm Hg; and HCO3, 1.5 (1.3–1.7) mEq/L. The mean differences (± 2 standard deviations) were greater than the minimum clinically important differences identified in the survey.Conclusions:Arterial and venous blood gas samples were strongly correlated, and there were only small differences between them. A survey of emergency physicians suggested that the differences are too large to allow for interchangeability of results; however, venous values may be valid if used in conjunction with a correction factor or for trending purposes.

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Objectives:To determine Canadian emergency physicians’ estimates regarding the safety and efficiency of chest discomfort management in their emergency department (ED), and their attitudes toward and perception of the need for a chest discomfort clinical prediction rule that identifies very low risk patients who are safe to discharge after a brief ED assessment.Methods:300 members of the Canadian Association of Emergency Physicians (CAEP) were randomly selected to receive a confidential mail survey, which invited them to provide information on current disposition of patients with chest discomfort and their opinions regarding the value of a clinical prediction rule to identify patients with chest discomfort who are safe to discharge after a brief (~2 hour) assessment.Results:Of the 300 physicians selected, 288 were eligible for the survey and 235 (82%) responded. Only 5% follow discharged patients to measure safe practice. Overall, 165 (70%) felt the proposed prediction rule would be very useful and 43 (18%) felt it would be useful. Almost all (94%) believed a prediction rule would be useful if it identified patients safe for discharge without increasing the current rate of missed acute myocardial infarction (estimated at 2%). Most respondents (59%) believed that a clinical prediction rule should suggest a course of action, while 30% felt it should convey a probability of disease.Conclusions:Canadian emergency physicians support the concept of a clinical prediction rule for the early discharge of patients with chest discomfort. Most believe that such a rule would be useful if it identified patients who are safe for discharge after a brief assessment, while maintaining current levels of safety. Future research should be aimed at deriving a clinical prediction rule to identify low risk patients who can be safely discharged after a limited emergency department evaluation.

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