Predictive Value of Capnography for Suspected Diabetic Ketoacidosis in the Emergency Department

Hassan Soleimanpour, MD; Ali Taghizadieh, MD; Mitra Niafar, MD; Farzad Rahmani, MD; Samad EJ Golzari, MD; Robab Mehdizadeh Esfanjani, MSc

Disclosures

Western J Emerg Med. 2013;14(6):590-594. 

In This Article

Abstract and Introduction

Abstract

Introduction:Metabolic acidosis confirmed by arterial blood gas (ABG) analysis is one of the diagnostic criteria for diabetic ketoacidosis (DKA). Given the direct relationship between end-tidal carbon dioxide (ETCO2), arterial carbon dioxide (PaCO2), and metabolic acidosis, measuring ETCO2 may serve as a surrogate for ABG in the assessment of possible DKA. The current study focuses on the predictive value of capnography in diagnosing DKA in patients referring to the emergency department (ED) with increased blood sugar levels and probable diagnosis of DKA.

Methods:In a cross-sectional prospective descriptive-analytic study carried out in an ED, we studied 181 patients older than 18 years old with blood sugar levels of higher than 250 mg/dl and probable DKA. ABG and capnography were obtained from all patients. To determine predictive value, sensitivity, specificity and cut-off points, we developed receiver operating characteristic curves.

Results:Sixty-two of 181 patients suffered from DKA. We observed significant differences between both groups (DKA and non-DKA) regarding age, pH, blood bicarbonate, PaCO2 and ETco2 values (p≤0.001). Finally, capnography values more than 24.5 mmHg could rule out the DKA diagnosis with a sensitivity and specificity of 0.90.

Conclusion:Capnography values greater than 24.5 mmHg accurately allow the exclusion of DKA in ED patients suspected of that diagnosis. Capnography levels lower that 24.5 mmHg were unable to differentiate between DKA and other disease entities. [West J Emerg Med. 2013;14(6):590–594.]

Introduction

Diabetes mellitus, defined by high levels of glucose and impaired carbohydrate and lipid metabolism, is the most common endocrine disorder and includes a wide group of metabolic diseases whose major characteristic is hyperglycemia caused by impaired insulin secretion and/or function.[1] Patients with diabetes mellitus are prone to important and disabling complications. One of the most important complications of the diabetes is diabetic ketoacidosis (DKA).[2] DKA mostly occurs in patients with type I diabetes; however, patients with type II diabetes are also prone to DKA at early ages under stress conditions including trauma, surgery, or infection.[3]

DKA is defined as blood sugar levels ≥250 mg/dl, ketonuria, ketonemia, and metabolic acidosis (pH<7.3 or blood bicarbonate levels <15 meq/dl).[4] Blood sugar measurement can be quickly performed using glucometry devices widely available in emergency departments (ED). Ketones in urine could be assessed rapidly using urine dipsticks. However, measurement of the acid-base levels is more challenging. Commonly, arterial blood gas (ABG), pH, and bicarbonate levels are used to diagnose acidosis and evaluate its severity. Yet, obtaining ABG samples can be a painful and time-consuming procedure.[5] Alternatively, capnography may be used as an alternative, non-invasive and inexpensive (in comparison with ABG) method of assessing ventilatory response to typical metabolic acidosis of DKA.[5–10] In our center, the cost of capnography is 1 United States Dollar (USD) whereas each ABG costs 2.5 USD (1 USD for blood sampling and 1.5 for the analysis). Numerous studies have evaluated the relationship between acidosis and ETCO2, most of which are in the pediatric patients or the patients without DKA.[11–15] In the current study, we aimed to evaluate the relationship between blood bicarbonate and end-tidal carbon dioxide (ETCO2) values and the predictive value of ETCO2 in DKA diagnosis in adult patients with increased blood sugar levels referred to the ED.

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