Differential Diagnosis for Monomorphic Tachycardia in a Hyperglycemic Hyponatremic Patient

• Single Most Likely Diagnosis
  • Diabetic Ketoacidosis (DKA) with dehydration and electrolyte imbalance: This condition is highly likely given the patient's hyperglycemia and hyponatremia. Monomorphic tachycardia can occur due to dehydration, acidosis, and electrolyte disturbances, which are common in DKA.
• Other Likely Diagnoses
  • Hypovolemic shock: Dehydration from hyperglycemia can lead to hypovolemia, causing tachycardia. The hyponatremia could exacerbate the hypovolemic state.
  • Thyroid storm: Although less common, thyroid storm can present with tachycardia, hyperglycemia, and may have associated electrolyte imbalances.
  • Adrenal insufficiency: This condition can cause hypotension, tachycardia, and electrolyte disturbances, including hyponatremia, especially in the context of critical illness.
• Do Not Miss Diagnoses
  • Cardiac arrhythmias (e.g., atrial flutter, paroxysmal supraventricular tachycardia): These conditions can be life-threatening if not promptly recognized and treated. The monomorphic nature of the tachycardia suggests a possible re-entrant tachycardia.
  • Pulmonary embolism: Although not directly related to the metabolic state, pulmonary embolism can cause tachycardia and is a critical diagnosis not to miss due to its high mortality rate if untreated.
  • Sepsis: Infection can lead to a systemic inflammatory response syndrome (SIRS) characterized by tachycardia, among other signs. Sepsis is a life-threatening condition that requires immediate recognition and treatment.
• Rare Diagnoses
  • Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of tachycardia, hypertension, and hyperglycemia due to excessive catecholamine release.
  • Insulinoma: A rare pancreatic tumor that produces excess insulin, potentially leading to hypoglycemia rather than hyperglycemia, but could be considered in the differential for unexplained metabolic disturbances and tachycardia.