Case Study: The Diabetic Crisis - Week 1

Case Presentation

Patient Demographics

Name: Sarah Mitchell
Age: 45 years old
Gender: Female
Medical History: Type 1 Diabetes Mellitus (diagnosed age 12), Hypothyroidism
Current Medications: Insulin glargine 24 units daily, Insulin lispro sliding scale, Levothyroxine 100mcg daily

Chief Complaint

"I've been vomiting for the past two days and I'm so thirsty I can't stop drinking water. My blood sugar has been over 20 mmol/L at home."

History of Present Illness

Sarah is a 45-year-old female with Type 1 diabetes who presents to the Emergency Department with a 2-day history of nausea, vomiting (5-6 times/day), and polydipsia (drinking 5-6 liters of water daily). She reports missing her insulin doses for the past 3 days due to running out of supplies while traveling. She noticed fruity-smelling breath this morning. She denies fever, chest pain, or abdominal pain but reports generalized weakness and dizziness when standing.

Vital Signs & Physical Examination

Vital Signs

Blood Pressure

95/60

mmHg

Heart Rate

118

bpm

Respiratory Rate

28

/min

Temperature

37.2

°C

SpO2

97%

on room air

Blood Glucose

28.4

mmol/L

Physical Examination Findings

General: Alert, oriented, appears acutely unwell, dehydrated mucous membranes
Respiratory: Deep, rapid breathing (Kussmaul respirations), clear lung fields bilaterally, fruity odor on breath
Cardiovascular: Tachycardic, regular rhythm, capillary refill time 3 seconds, weak peripheral pulses
Abdomen: Soft, non-tender, normoactive bowel sounds
Neurological: Alert and oriented x3, no focal deficits
Skin: Dry, poor turgor, no rashes or wounds

Laboratory Results

Test	Result	Reference Range	Status
Blood Glucose	28.4 mmol/L	4.0-7.8 mmol/L	HIGH
HbA1c	11.2%	< 7.0%	HIGH
pH	7.18	7.35-7.45	LOW
pCO2	28 mmHg	35-45 mmHg	LOW
HCO3-	10 mmol/L	22-28 mmol/L	LOW
Ketones (serum)	5.8 mmol/L	< 0.6 mmol/L	HIGH
Anion Gap	22 mmol/L	8-16 mmol/L	HIGH
Sodium	138 mmol/L	135-145 mmol/L	Normal
Potassium	5.1 mmol/L	3.5-5.0 mmol/L	BORDERLINE
Creatinine	145 μmol/L	45-90 μmol/L	HIGH

Clinical Reasoning Questions

1. What is the most likely diagnosis based on Sarah's presentation?

Hyperosmolar Hyperglycemic State (HHS) Hypoglycemic coma Diabetic Ketoacidosis (DKA) Thyroid storm

Correct! Diabetic Ketoacidosis (DKA)

DKA is characterized by the triad of:
• Hyperglycemia (>11 mmol/L) - Sarah's is 28.4 mmol/L
• Metabolic acidosis (pH < 7.30) - Sarah's pH is 7.18
• Ketosis (ketones > 3.0 mmol/L) - Sarah's is 5.8 mmol/L

The presence of fruity breath (acetone), Kussmaul respirations (compensatory hyperventilation for metabolic acidosis), and elevated anion gap (22) further confirm DKA.

2. What bioscience concept explains why Sarah is experiencing deep, rapid breathing (Kussmaul respirations)?

Hypoxemia stimulating peripheral chemoreceptors Metabolic acidosis triggering compensatory respiratory alkalosis via central chemoreceptors Hyperglycemia causing direct stimulation of the respiratory center Ketone bodies acting as respiratory stimulants

Correct! Metabolic acidosis triggering compensatory respiratory alkalosis

The low blood pH (7.18) and low bicarbonate (10 mmol/L) indicate metabolic acidosis. Central chemoreceptors in the medulla oblongata detect the increased H+ concentration and stimulate increased respiratory rate and depth. This compensatory mechanism blows off CO2 (reducing pCO2 to 28 mmHg), which helps raise the pH back toward normal. This is an example of how the respiratory system compensates for metabolic acid-base disturbances.

3. Which cellular mechanism is primarily responsible for the high blood glucose in Type 1 diabetes?

Overproduction of glucagon by alpha cells Insulin resistance at the cellular level Excessive hepatic glycogenolysis Autoimmune destruction of pancreatic beta cells leading to absolute insulin deficiency

Correct! Autoimmune destruction of pancreatic beta cells

Type 1 diabetes is an autoimmune disease where the body's immune system destroys the insulin-producing beta cells in the pancreatic islets of Langerhans. This results in:
• Absolute insulin deficiency (no insulin production)
• Inability to transport glucose into cells via GLUT4 transporters
• Uncontrolled hepatic glucose production (glycogenolysis and gluconeogenesis)
• Hyperglycemia despite high circulating glucose levels

This is fundamentally different from Type 2 diabetes, which involves insulin resistance and relative insulin deficiency.

4. What explains the "fruity" odor on Sarah's breath?

Bacterial breakdown of glucose in the oral cavity Excretion of excess glucose through the lungs Volatile acetone excretion resulting from ketone body metabolism Uremic toxins from elevated creatinine

Correct! Volatile acetone excretion

In the absence of insulin, cells cannot use glucose for energy and switch to fat metabolism (lipolysis). The liver converts fatty acids to ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone) as alternative fuel sources. Acetone is volatile and excreted through the lungs, producing the characteristic "fruity" or nail-polish remover odor. The elevated serum ketones (5.8 mmol/L) confirm this metabolic pathway is active.

5. Which nursing intervention is most important to prevent complications during treatment?

Restrict fluid intake to prevent cerebral edema Monitor serum potassium closely during insulin therapy Administer sodium bicarbonate to correct acidosis rapidly Give large bolus of insulin immediately

Correct! Monitor serum potassium closely

Insulin drives potassium from the extracellular fluid into cells. In DKA, despite total body potassium depletion, serum potassium may be normal or elevated due to acidosis (H+ displaces K+ from cells). As insulin therapy corrects acidosis and drives K+ into cells, serum potassium can drop precipitously, causing life-threatening cardiac arrhythmias. Close monitoring and replacement are essential. Other correct interventions include gradual glucose reduction (not rapid) and fluid resuscitation (not restriction).

Bioscience Integration

Glucose Homeostasis and Feedback Loops

Normal glucose homeostasis relies on a negative feedback loop:

Set point: Blood glucose ~5.5 mmol/L
Sensors: Pancreatic beta cells detect glucose levels
Effectors: Insulin (lowers glucose) and glucagon (raises glucose)

In Type 1 diabetes, the beta cells are destroyed, breaking this feedback loop. Without insulin:

GLUT4 transporters don't move to cell membranes
Glucose cannot enter cells for energy
Cells "starve" despite high blood glucose
The liver continues producing glucose (unregulated gluconeogenesis)

Ketogenesis and Acidosis

When glucose is unavailable, the liver converts fatty acids to ketone bodies:

Acetoacetate and beta-hydroxybutyrate are strong acids
They dissociate, releasing H+ ions into the blood
Bicarbonate (HCO3-) buffers the H+, becoming depleted
Result: Metabolic acidosis with elevated anion gap

The respiratory system compensates by increasing ventilation (Kussmaul respirations) to blow off CO2, raising the pH.

Nursing Implications

Monitor: Blood glucose hourly, electrolytes (especially K+), acid-base status, urine output, neurological status
Interventions: IV fluid resuscitation (0.9% saline initially), insulin infusion (0.1 units/kg/hr), potassium replacement
Complications to watch: Hypoglycemia, hypokalemia, cerebral edema (if glucose drops too rapidly), cardiac arrhythmias
Patient education: Importance of insulin adherence, sick day management, ketone testing, recognizing DKA symptoms

Self-Assessment Questions

Review: Why does Sarah have normal/high serum potassium despite being in DKA?

Think about acid-base chemistry and ion exchange across cell membranes...

Answer: In acidosis, H+ ions enter cells to be buffered. To maintain electrical neutrality, K+ ions exit cells into the extracellular fluid, raising serum potassium. However, total body potassium is actually depleted due to osmotic diuresis. Once insulin treatment begins and acidosis corrects, K+ re-enters cells and serum potassium can drop dangerously low.

Apply: Explain how missing insulin doses for 3 days led to DKA.

Trace the physiological cascade from insulin deficiency to metabolic acidosis...

Answer: Without insulin → cells can't use glucose → blood glucose rises (hyperglycemia) → osmotic diuresis → dehydration. Simultaneously, cells switch to fat metabolism → ketone production → metabolic acidosis. The combination = DKA.

Analyze: Why is aggressive sodium bicarbonate administration NOT recommended in DKA?

Consider the risks of rapid pH correction...

Answer: Rapid correction of acidosis with bicarbonate can cause:
1. Paradoxical CSF acidosis (CO2 crosses blood-brain barrier faster than bicarbonate)
2. Hypokalemia (drives K+ into cells)
3. Impaired oxygen delivery (shifts oxyhemoglobin dissociation curve left)
4. Cerebral edema

Bicarbonate is only considered if pH < 6.9 and hemodynamic instability persists.

The Diabetic Crisis

Learning Objectives