A 21-year old brother of a person with insulin-dependent diabetes mellitus experienced increased urination and thirst for 6 weeks, along with a 15 pound weight losss, despitre a normal appetite. Fearing that these symptoms meant he also had developed diabetes mellitus, he did not seek medical attention promptly. However, when he developed nausea and vomiting for 48 hours, followed by a stuporous state, his college roommate insisted on taking him to the emergency room. There, he was found to ne semi-coherent and his mucous membranes and skin were dry. Blood pressure was 84/52 and pulse rate was 120 bpm. He was breathig deeply at a rate of 30 respirations per minute. The remainder of the examination was within normal limits. A urine sample contained a glucose concentration of 5% and tested strongly positive for acetoacetic acid. Plasma glucose was 800 mg/dl. Sodium was 132 mEq/L, bicarbonate was 5 mEq/l. chloride was 104 mEq/L and potassium was 5.8 mEq/L. Blood pH was 7.1, Pco2 was 17 mmHg and PO2 was 95 mmHg. Blood urea nitrogen was 28 mg/dl and plasma creatinine was 1.4 mg/dl. On treatment with insulin, intravenous fluids and potassium, the patient's clinical and biochemical status was restored to normal in 24 hours.
1.What is the cause if this pateint's very high plasma glucose level?
2.What are the mechanisms that elevated plasma glucose?
3.What has replaced bicarbonate in the patient's plasma, and by what mechanism?
4.Why is the blood pressure low and the pulse rate high?
5.What contributed to the pateint's weight loss?
1. The cause of this patient's very high plasma glucose level is uncontrolled diabetes mellitus, specifically diabetic ketoacidosis (DKA).
To determine the cause of the high plasma glucose level, a diagnosis of DKA can be made based on the patient's symptoms of increased urination and thirst, weight loss, and the presence of nausea, vomiting, and a stuporous state. These symptoms, coupled with a high plasma glucose level of 800 mg/dL, strongly indicate DKA as the cause.
2. The mechanisms that contribute to the elevated plasma glucose level in DKA are insulin deficiency and increased production of glucose by the liver.
Insulin is crucial for glucose regulation in the body. In people with diabetes, insulin is either insufficiently produced or ineffective in regulating blood sugar levels. In this case, the patient's brother has insulin-dependent diabetes mellitus, which means his body is not producing enough insulin.
Insufficient insulin leads to increased glucose production by the liver and a decrease in glucose uptake by cells. As a result, glucose accumulates in the bloodstream, leading to a high plasma glucose level.
3. In the patient's plasma, bicarbonate has been replaced by ketone bodies, specifically acetoacetic acid, due to the state of ketoacidosis.
Ketoacidosis occurs when the body cannot properly use glucose for energy, so it starts breaking down fat for an alternative energy source. This breakdown of fat produces ketones, which are acidic byproducts.
As a compensatory mechanism, the body tries to buffer the acidity by using bicarbonate (HCO3-) ions. However, in DKA, the excessive production of ketones overwhelms the body's ability to buffer them, leading to a decrease in plasma bicarbonate levels and an increase in ketone bodies like acetoacetic acid.
4. The low blood pressure and high pulse rate in this patient are a result of several factors associated with DKA.
DKA can cause a state of dehydration due to excessive urination and poor fluid intake. Dehydration leads to a decrease in blood volume, resulting in low blood pressure.
Additionally, the ketone bodies produced in DKA cause an increase in the production of stress hormones such as epinephrine and norepinephrine. These hormones can increase heart rate, leading to a high pulse rate.
5. The patient's weight loss can be attributed to several factors in DKA.
In DKA, the body is unable to use glucose for energy effectively due to insulin deficiency. To compensate for the lack of available glucose, the body starts breaking down fat stores for energy through a process called lipolysis.
The breakdown of fats releases fatty acids that are used for energy production. However, as a result, this leads to the breakdown of body fat stores, resulting in weight loss. Additionally, the loss of fluids due to excessive urination contributes to further weight loss.