From the Research
In a road traffic accident with hypovolemia, the primary hormone secreted in response to decreased blood flow to the kidney is aldosterone, as part of the renin-angiotensin-aldosterone system (RAAS) to maintain blood pressure and restore blood volume. When blood volume decreases due to hemorrhage or fluid loss following trauma, renal perfusion drops, triggering the release of renin, which initiates the RAAS cascade, ultimately leading to the secretion of aldosterone from the adrenal cortex 1. Aldosterone acts on the kidney to promote sodium and water retention, increasing blood volume and blood pressure, which is essential for maintaining organ perfusion during the critical period following trauma with significant blood loss. The most recent and highest quality study on the topic, published in 2023, highlights the crucial role of aldosterone in renal and cardiovascular physiology, particularly in response to changes in dietary sodium intake and its effects on electrolyte and acid-base balance 1.
Key points to consider in this context include:
- The renin-angiotensin-aldosterone system (RAAS) is activated in response to decreased blood volume and renal perfusion.
- Aldosterone secretion is stimulated by angiotensin II, which is converted from angiotensin I by angiotensin-converting enzyme (ACE).
- The primary action of aldosterone is to promote sodium and water retention in the kidney, thereby increasing blood volume and blood pressure.
- The effects of aldosterone are mediated through the activation of mineralocorticoid receptors (MRs) in the distal nephron and collecting duct of the kidney 1.
- While other hormones such as catecholamines and cortisol may also be secreted in response to trauma and hypovolemia, aldosterone plays a critical role in the RAAS cascade and the restoration of blood volume and blood pressure 2, 3.
Given the importance of maintaining blood pressure and restoring blood volume in the context of hypovolemia following a road traffic accident, the secretion of aldosterone is a critical physiological response. Therefore, the correct answer is B. ADH is not the primary hormone, but rather aldosterone, however ADH is also secreted in response to hypovolemia.