The arterial blood gas below indicates that the primary acid-base imbalance is:

pH - 7.25

PaCO2 - 20 mm Hg

HCO3- - 10 mEq/L

Select all that apply:

Normal range:

pH = 7.35-7.45

PaCO2 = 36-44 mmHg

HCO3- = 22-26 mEq/L

Choice A Reason:

An increase in HCO3- (bicarbonate) is not typically associated with diarrhea and lower intestinal fluid losses. In fact, the opposite is true. Diarrhea often leads to a loss of bicarbonate, which can result in metabolic acidosis. Therefore, this choice is incorrect.

Choice B Reason:

This is the correct answer. Diarrhea and other lower intestinal fluid losses lead to a decrease in HCO3- levels. The loss of bicarbonate from the body results in a lower pH, contributing to metabolic acidosis. This condition occurs because bicarbonate is a key buffer that helps maintain the acid-base balance in the blood.

Choice C Reason:

An increase in the chance of alkalosis is not typically associated with diarrhea. Alkalosis refers to a condition where the pH of the blood is higher than normal, which can occur due to a loss of hydrogen ions or an increase in bicarbonate. However, diarrhea usually causes a loss of bicarbonate, leading to acidosis rather than alkalosis.

Choice D Reason:

Saying that diarrhea has no effect on the pH of the blood is incorrect. Diarrhea can significantly impact the acid-base balance in the body by causing a loss of bicarbonate, leading to metabolic acidosis. Therefore, this choice is incorrect.

Choice A Reason:

Norepinephrine is a key neurotransmitter released by the sympathetic nervous system during the “fight-or-flight” response. It plays a crucial role in preparing the body to respond to stress by increasing heart rate, blood pressure, and blood flow to muscles, as well as dilating the airways. These physiological changes are essential for coping with acute stress.

Choice B Reason:

Cortisol is a hormone released by the adrenal glands in response to stress, but it is primarily associated with the hypothalamic-pituitary-adrenal (HPA) axis rather than the sympathetic nervous system. While cortisol contributes to the body’s overall stress response by increasing blood sugar levels and suppressing the immune system, it is not the primary mediator of the acute “fight-or-flight” response.

Choice C Reason:

ACTH (adrenocorticotropic hormone) is a hormone produced by the pituitary gland that stimulates the adrenal glands to release cortisol. It is part of the HPA axis and plays a role in the body’s long-term stress response, but it is not directly involved in the immediate activation of the sympathetic nervous system.

Choice D Reason:

Glucagon is a hormone produced by the pancreas that raises blood glucose levels by promoting the breakdown of glycogen to glucose in the liver. While it can be involved in the body’s response to stress by ensuring an adequate supply of glucose, it is not a primary mediator of the acute stress response mediated by the sympathetic nervous system.