A 40-year-old female presents to the emergency department with complaints
of lower back pain, fever, nausea, vomiting, malaise, chills, syncope, dizzi-
ness, and shortness of breath. Patient states that she has some burning with uri-
nation (dysuria). Her fever was as high as 39.4°C (103°F) at home earlier in
the day. She has a history of non-insulin-dependent diabetes mellitus but
denies any other medical problems. On exam, she is in moderate distress with
a temperature of 38.9°C (102°F) degrees, pulse of 110 beats per minute, res-
piratory rate of 30 breaths per minute, and blood pressure of 70/30 mm Hg.
Her extremities are cool to the touch with thready pulses. Her chest is clear to
auscultation bilaterally, and heart is tachycardic but with regular rhythm. She
has significant costovertebral tenderness on the right side. Her white blood cell
(WBC) count was elevated at 20,000/mm3. The hemoglobin and hematocrit
were normal. Her glucose was moderately elevated at 200 mg/dL, and her
serum bicarbonate level is low. An arterial blood gas demonstrated a pH of
7.28 and parameters consistent with a metabolic acidosis. Her urinalysis
shows an abnormal number of gram-negative rods.
What is the most likely diagnosis?
What is the biochemical mechanism of the metabolic acidosis?