Abstract & Commentary
Source: Ma OJ, et al. Arterial blood gas results rarely influence emergency physician management of patients with suspected diabetic ketoacidosis. Acad Emerg Med 2003;10:836-841.
The primary objective of this prospective observational study was to test the hypothesis that arterial blood gas (ABG) results for patients with diabetic ketoacidosis (DKA) do not influence emergency physicians’ decisions regarding final diagnosis, treatment, and final disposition of patients. An additional aim was to assess the correlation between venous pH and arterial pH values in the emergency department (ED).
Patient inclusion criteria were capillary blood glucose equal to or greater than 200mg/dL; ketonuria; and clinical signs and symptoms of DKA. The protocol dictated that electrolytes, ABGs, and venous pH samples be drawn either simultaneously or within 30 minutes of each other and before intravenous (IV) fluid or insulin administration. Attending emergency physicians indicated planned management and disposition on a standardized form before and after reviewing ABG and venous pH results.
The results of the ABGs changed the emergency physicians’ final diagnosis in two of the 200 cases (1.0%; 95% CI = 0.3-3.6%), altered treatment in seven of 200 cases (3.5%; 95% CI = 1.7-7.1%), and changed the final patient disposition in two of 200 cases (1.0%; 95% CI = 0.3-3.6%). Venous pH correlated well with arterial pH results (r = 0.951) and bias plotting yielded a value of -0.015 (± 0.006 pH units). The authors concluded that ABG results rarely influenced emergency physicians’ decisions on diagnosis, treatment, or disposition in suspected DKA patients.
Commentary by Stephanie B. Abbuhl, MD, FACEP
In truth, one could conclude that neither the ABG nor the venous gas altered the major decision-making in these patients. This should come as no surprise, given that an appropriate interpretation of the anion gap usually is an excellent indicator of the degree of metabolic acidosis and can guide the major decisions in initial management. In addition, there has been mounting evidence that bicarbonate use may be detrimental in DKA regardless of the pH, and therefore, one would not suspect that pH results would have an impact on this potential aspect of treatment. (No one in this study received bicarbonate.) In five of the six cases in which the pH dictated a change in decision-making, the change was in the route of insulin administration (IV to subcuticular, or vice versa). In only two cases was there a change in decision-making based on either the PO2 or the PCO2.
An important caveat in reviewing this study is that only 48 of the 200 suspected DKA patients (24%) actually fulfilled the diagnosis of DKA as defined by the American Diabetes Association (i.e., having a pH of less than 7.30, serum bicarbonate of less than 15 mmol/L, serum glucose greater than 250 mg/dL, ketonuria, and an anion gap of greater than 10 mmol/L2). It appears that most of the patients in this study had mild or early DKA, and this would not necessarily be the group in which either ABG or venous gas data would be expected to offer additional significant information. The study only was powered to detect a 10% difference in management decisions, and so the possibility exists that a larger study might find a greater difference.
Despite these potential limitations, we now have additional evidence to support the management of many DKA patients without ABGs, and often without venous gases. When the emergency physician feels that pH data may change decision-making, a venous gas is the appropriate test unless there are reasons to suspect that precise oxygenation measurement is needed (rarely) or that ventilation may be compromised, usually by coexisting cardiopulmonary illnesses; in those cases, an ABG could be helpful in a small number of patients.
Dr. Abbuhl is Medical Director, Department of Emergency Medicine, The Hospital of the University of Pennsylvania; Associate Professor of Emergency Medicine, University of Pennsylvania School of Medicine, Philadelphia.