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Educational Objectives:

After evaluating this article, participants will be able to:
1. Incorporate strategies for the safe and effective management of DKA in pediatric patients
2. Incorporate the current literature into clinical practice improving the quality of care for pediatric DKA patients
3. Develop strategies for utilizing VBGs in clinical practices

Pediatric DKA management has always been fraught with concern regarding fluid management due to the risk of cerebral edema. While cerebral edema is uncommon, it has devastating complications and is always in the forefront of our management techniques.  In addition, we have been taught to obtain a blood gas to assist with management. Recent articles have shown that a venous blood gas (VBG) is just as helpful as an arterial blood gas, but do we still need both a VBG with electrolytes and a serum chemistry? This journal club will address these questions and help guide our management of children with DKA.


Q. Does the use of bicarbonate therapy contribute to the risk of cerebral edema:

A. This landmark article confirms that children with diabetic ketoacidosis who have low partial pressures of arterial carbon dioxide and high serum urea nitrogen concentrations at presentation and who are treated with bicarbonate are at increased risk for cerebral edema.

Citation: Glaser N, Barnett P, McCaslin I, Nelson D, etal. Risk factors for cerebral edema in children with diabetic ketoacidosis. The Pediatric Emergency Medicine Collaborative Research Committee of the American Academy of Pediatrics. N Engl J Med. 2001 Jan 25;344(4):264-9

METHODS: In this multicenter study, 61 children were identified who had been hospitalized for diabetic ketoacidosis within a 15-year period and in whom cerebral edema had developed. Two additional groups of children with diabetic ketoacidosis but without cerebral edema were also identified: 181 randomly selected children and 174 children matched to those in the cerebral-edema group with respect to age at presentation, onset of diabetes (established vs. newly diagnosed disease), initial serum glucose concentration, and initial venous pH. Using logistic regression we compared the three groups with respect to demographic characteristics and biochemical variables at presentation and compared the matched groups with respect to therapeutic interventions and changes in biochemical values during treatment.

RESULTS: A comparison of the children in the cerebral-edema group with those in the random control group showed that cerebral edema was significantly associated with lower initial partial pressures of arterial carbon dioxide (relative risk of cerebral edema for each decrease of 7.8 mm Hg [representing 1 SD], 3.4; 95 percent confidence interval, 1.9 to 6.3; P<0.001) and higher initial serum urea nitrogen concentrations (relative risk of cerebral edema for each increase of 9 mg per deciliter [3.2 mmol per liter] [representing 1 SD], 1.7; 95 percent confidence interval, 1.2 to 2.5; P=0.003). A comparison of the children with cerebral edema with those in the matched control group also showed that cerebral edema was associated with lower partial pressures of arterial carbon dioxide and higher serum urea nitrogen concentrations. Of the therapeutic variables, only treatment with bicarbonate was associated with cerebral edema, after adjustment for other covariates (relative risk, 4.2; 95 percent confidence interval, 1.5 to 12.1; P=0.008).

CONCLUSIONS: Children with diabetic ketoacidosis who have low partial pressures of arterial carbon dioxide and high serum urea nitrogen concentrations at presentation and who are treated with bicarbonate are at increased risk for cerebral edema



Q. How accurate are VBG electrolytes when compared against standard serum chemistry analysis in the diagnosis of DKA?

A. In this study, Venous Blood Gas (VBG) electrolytes were 97.8% sensitive and 100% specific for the diagnosis of DKA in hyperglycemic patients. These preliminary findings suggest that VBG electrolytes may be used instead of VBG and serum chemistry analysis to assist with the diagnosis of Diabetic ketoacidosis.

Citation: Menchine M, Probst MA, Agy C, Bach D, Arora S. Diagnostic accuracy of venous blood gas electrolytes for identifying diabetic ketoacidosis in the emergency department. Acad Emerg Med. 2011 Oct;18(10):1105-8. doi: 10.1111/j.1553-2712.2011.01158.x. Epub 2011 Sep 26.

OBJECTIVES:  Diagnosing diabetic ketoacidosis (DKA) has traditionally required a venous blood gas (VBG) to obtain serum pH and a serum chemistry panel to obtain electrolyte values. Because newer blood gas analyzers have the ability to report electrolyte values and glucose in addition to pH, this diagnostic process could theoretically be condensed.

However, neither the diagnostic accuracy of the VBG for DKA nor the agreement between the VBG electrolytes and the serum chemistry electrolytes, including sodium, chloride, and bicarbonate, has been evaluated in the context of acute hyperglycemia. The purpose of this study was to assess the accuracy of VBG electrolytes for diagnosing DKA using serum chemistry electrolytes measures as the criterion standard and to describe the correlation between VBG and serum chemistry electrolytes in a sample of hyperglycemic patients seen in the emergency department (ED). Methods:  The authors prospectively identified a convenience sample of ED patients with serum blood glucose ≥ 250 mg/dL and examined their paired VBG and serum chemistry electrolytes. The diagnosis of DKA was made by using American Diabetes Association (ADA) criteria including serum glucose ≥ 250 mg/dL, serum anion gap > 10 mEq/L, bicarbonate ≤ 18 mEq/L, serum pH ≤ 7.30, and presence of ketosis. Serum chemistry electrolyte values were considered to be the criterion standard. Diagnostic test characteristics of VBG electrolytes including sensitivity and specificity were compared against this standard. In addition, correlation coefficients for individual electrolytes and anion gap between VBG and chemistry electrolytes were calculated. Results:  Paired VBG and serum chemistry panels were available for 342 patients, of whom 46 (13.5%) had DKA. The sensitivity and specificity of the VBG electrolytes for diagnosing DKA was 97.8% (95% confidence interval [CI] = 88.5% to 99.9%) and 100% (95% CI = 98.8% to 100%), respectively. One case of DKA was missed by the VBG. Correlation coefficients between VBG and serum chemistry were 0.90, 0.73, 0.94, and 0.81 for sodium, chloride, bicarbonate, and anion gap, respectively.

Q. Does a serum bicarbonate level accurately predict venous pH?

A. In this study, a serum HCO3 18.5 or less predicted a venous pH of less than 7.3 (area under the curve = 0.97; CI, 0.94-0.99; sensitivity, 93%; specificity, 91%), and a serum HCO3 10.5 or less predicted a venous pH of less than 7.1 (area under the curve = 0.97; CI, 0.95-0.99; sensitivity, 97%; specificity, 88%).

Citation: Nadler OA, Finkelstein MJ, Reid SR. How Well Does Serum Bicarbonate Concentration Predict the Venous pH in Children Being Evaluated for Diabetic Ketoacidosis? Pediatr Emerg Care. 2011 Oct;27(10):907-10.

OBJECTIVE: The objective of the study was to determine whether serum bicarbonate (HCO3) concentration can accurately predict venous pH in the evaluation of diabetic ketoacidosis (DKA).

METHODS: A retrospective review of patients who presented to a children’s hospital emergency department and received an International Classification of Diseases, Ninth Revision code related to DKA or diabetes mellitus was performed. To be eligible for inclusion and data abstraction, patients had blood sampled simultaneously for venous blood gas and metabolic panel. A linear regression model was created using pH (dependent variable) and HCO3 (predictor). The diagnostic performance and accuracy of HCO3 to discriminate abnormal pH were evaluated using receiver operating characteristic curve analysis. RESULTS: Three hundred patients met the inclusion criteria. The linear relationship between pH and HCO3 using the Pearson correlation coefficient was found to be R = 0.89 (confidence interval [CI], 0.83-0.95; R = 0.79). Receiver operating characteristic curve analysis that maximized sensitivity and specificity demonstrated that a HCO3 18.5 or less predicts pH less than 7.3 (area under the curve = 0.97; CI, 0.94-0.99; sensitivity, 93%; specificity, 91%), and a HCO3 10.5 or less predicts pH less than 7.1 (area under the curve = 0.97; CI, 0.95-0.99; sensitivity, 97%; specificity, 88%).

CONCLUSIONS: Serum bicarbonate accurately predicts abnormal venous pH in children with DKA. Venous pH determination may not be necessary for all patients being evaluated for DKA

Summary: In a follow up article by Marcin JP etal (. Factors associated with adverse outcomes in children with diabetic ketoacidosis-related cerebral edema .J Pediatr. 2002 Dec;141(6):793-7), the authors confirm that the F=factors associated with poor outcomes in children with DKA include:  greater neurologic depression at the time of diagnosis of cerebral edema, a high initial serum urea nitrogen concentration, and intubation with hyperventilation to a PCO (2) <22 mm Hg. The children at risk for cerebral edema are the ones who present with higher serum blood urea nitrogen levels and are more acidotic at the time of presentation than children in DKA who do not develop DKA.  The use of bicarbonate in these children, I believe, is a reaction to their severity of disease and therefore we should not pull the trigger and randomly administer bicarbonate to these critically ill children.  The better part of valor would be to contact the ICU and endocrinology team who will be managing these patients.

Dr. Ghazala Sharieff is the Division Director at the San Diego Rady Children’s Hospital Emergency Care Center.

 

STEP 3: TAKE THE QUIZ

STEP 4: PROCESS PAYMENT

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