Fixation Errors in Altered Mental Status: When the First Diagnosis Becomes a Trap

In today's post, we will discuss a case that is a textbook example of how easy it is to develop tunnel vision in emergency medicine. “Diabetes means sugar”—this association immediately comes to mind, but is it always sufficient?

The Clinical Scenario

Emergency Medical Services were dispatched to a 26-year-old male found on a park bench in the morning with altered mental status. He was wearing a medical alert bracelet that read, “I have diabetes.”

EMS measured a fingerstick glucose of 26 mg/dL. Following the administration of intravenous glucose, his blood sugar rose to 180 mg/dL. However, the patient remained unconscious (GCS 6). He was transported to the emergency department with a suspected “prolonged hypoglycemic coma.”

In the ED, the patient remained unresponsive. What was missed?

We decided to re-evaluate the patient, performing a full ABCDE assessment, neurological exam, blood work, toxicology screening, and, if indicated, brain imaging. The answers came quickly. During the ABCDE assessment, we immediately noted that the patient’s skin was cool to the touch.

• Exposure (E): Upon undressing the patient, the skin was icy to the touch.

• Core Temperature: 27°C/80.6°F (tympanic temperature).

• Toxicology: Pronounced odor of alcohol; blood ethanol: 1.8 promille (approx. 0.18% BAC).

Final Diagnosis: Severehypothermia (Swiss Stage HT III), complicated by hypoglycemia and alcohol intoxication.

Why Didn't the Patient Wake Up? (Clinical Analysis)

This case is a humbling lesson in physiology. We were dealing with a “deadly trio”: diabetes + alcohol + cold.

1. Hypothermia: When Cold Shuts Down the Brain A core temperature of 27 °C/80.6 °F is life-threatening. According to the Swiss Staging System, this constitutes severe hypothermia.

2. Alcohol: A Treacherous Ally to the Cold In this case, alcohol acted as a catalyst for disaster through two mechanisms:

• Vasodilation: Alcohol dilates blood vessels (creating a false sensation of warmth), which accelerates heat loss. At the same time, it impairs shivering thermogenesis (the body's primary method of heat production).

• Alcohol-Induced Hypoglycemia: Alcohol metabolism in the liver consumes NAD+, which blocks gluconeogenesis. In a patient with depleted glycogen stores (due to a lack of food intake), the liver is unable to produce glucose, while exogenous insulin continues to act unopposed. This is a direct path to severe hypoglycemia.

How Not to Miss the Cause?

If a patient with altered mental status does not respond to standard treatment for a reversible cause, you must broaden your thinking and search for a “second cause.” Use trusted acronyms.

1. AEIOU TIPS This is the most popular mnemonic for differentiating causes of  coma:

• A – Alcohol, Acidosis

• E – Epilepsy, Electrolytes (Na, Ca), Endocrine (thyroid storm/adrenal crisis)

• I – Insulin (hypoglycemia or diabetic ketoacidosis)

• O – Overdose (drugs/narcotics), oxygen (hypoxia)

• U – Uremia

• T – Trauma (head injury), Temperature (hypothermia/heat stroke)

• I – Infection (meningitis, sepsis)

• P – Psychogenic causes, Poisoning (e.g., CO)

• S – Stroke, Shock, SAH (subarachnoid hemorrhage)

2. I WATCH DEATH
A less commonly used but comprehensive acronym for delirium and coma:

• I – Infection

• W – Withdrawal

• A – Acute metabolic disorder

• T – Trauma

• C – CNS pathology

• H – Hypoxia

• D – Deficiencies (vitamin deficiencies, e.g., B1)

• E – Endocrine

• A – Acute vascular

• T – Toxins

• H – Heavy metals

Fixation Errors

Fixation on a diagnosis (anchoring bias) is a common error in emergency medicine and a valuable learning opportunity. Occasionally the most obvious or visible diagnoses prompt us to end the diagnostic process too early. They give us the comfort of a “solved puzzle” and reduce our vigilance. This can happen in many situations; focusing solely on glycemia in a diabetic patient is just one example. Therefore, beware of tunnel vision. If your patient does not improve as expected, continually look for an underlying “second cause.”

Key Takeaways for Your Next Shift

• Tunnel vision kills: Identifying one disease doesn’t rule out another diagnosis.

• If a patient doesn't respond to appropriate treatment, it may be a sign that something has been missed.