Discussion Topic #4: Type 1 Diabetes & Acid/Base Homeostasis

Acid-Base Homeostasis: Type 1 Diabetes Patient Case Study

Part 1: Oregon State University Anatomy & Physiology Course – 26.4: Acid-Base Balance (Links to an external site.)

 (Links to an external site.)

The link above is required reading using Oregon State University’s open source textbook for their Anatomy & Physiology course. This is a supplement to the acid-base regulation lecture discussions in Chapters 13 & 14 of our course. 

The key here is that you have two systems, respiratory and renal, working together to address situations where acid/base homeostasis is disturbed.

Part 2: Clinical Case Study – Diabetic ketoacidosis 

Read the case summary below and then answer the questions that follow.

Case: During your shift in the ER, a 21-year old noncompliant male with a history of type I (insulin-dependent) diabetes mellitus was found in a coma. Your triage assessment and the lab testing revealed the following:

• Hyperglycemia: High blood glucose.
• High urine glucose.
• High urine ketones and serum ketones.
• Low serum bicarbonate <12 mEq/L.
• Exaggerated respiration.
• Breath has acetone odor.
• Hypotensive: blood pressure was 90/60 mm Hg.
• Tachycardia: Pulse weak and rapid (120 bpm).

Based on your understanding of both the respiratory and renal regulation of blood pH, answer the following:

1. Is this patient experiencing respiratory or metabolic acidosis? 
2. Based on your answer to #1, discuss the mechanism(s) which led to this complication.
3. The formula below represents the respiratory & renal systems’ regulation of acid-base balance (remember that the enzyme carbonic anhydrase catalyzes the forward reaction between carbon dioxide and water). 

CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃^–

Review this formula and discuss the mechanisms involved in the forward and reverse components of the reaction by answering the following:

1. When CO₂+ H₂O combine to form carbonic acid, discuss the respiratory mechanisms involved to regulate the levels of CO₂
2. Explain why exaggerated respiration (increased ventilation) help to decrease the levels of H⁺ 
3. When carbonic acid dissociates into free H⁺+ HCO₃^– what role do the levels of bicarbonate play in regulating H+ ion levels?
4. Discuss at least (2) of the renal mechanisms used to regulate HCO₃^– 

Discussion Topic #4: Type 1 Diabetes & Acid/Base Homeostasis Answer 

1. Since the patient is suffering from diabetes mellitus, we can initially infer that she has metabolic acidosis. The primary hallmark of which is the decrease in serum bicarbonate levels, thus, the patient indeed has metabolic acidosis.
2. In uncontrolled diabetes mellitus, the body experience insulin deficiency, which causes these mechanisms: