Introduction
Serum renin is a crucial enzyme in the renin-angiotensin-aldosterone system (RAAS) that plays a significant role in regulating blood pressure and fluid-electrolyte balance. Its potential as a prognostic marker in intensive care and perioperative settings has garnered increasing attention. Understanding serum renin levels and their implications can provide valuable insights for managing critically ill patients during the perioperative period.
Normal Values and Regulation
Serum renin levels are typically between 0.5-2.3 ng/mL/hr in healthy individuals. The enzyme’s secretion is regulated by several factors:
- Blood Pressure: Low blood pressure stimulates renin release.
- Sodium Levels: Low sodium levels can trigger renin secretion.
- Sympathetic Nerve Activation: Increased sympathetic activity can elevate renin levels.
Renin converts angiotensinogen to angiotensin I, which is subsequently converted to angiotensin II, a potent vasoconstrictor. This pathway is essential for maintaining blood pressure and electrolyte balance.
Uses in the Perioperative Period
Assessment of Volume Status
- Low Renin Levels: May indicate volume overload, suggesting the need for fluid restriction.
- High Renin Levels: May signal volume depletion, potentially requiring fluid resuscitation.
Prediction of Hemodynamic Instability
- Elevated renin levels have been linked to an increased risk of hemodynamic instability. For instance, the study “Renin as a Prognostic Marker in Intensive Care and Perioperative Settings: A Scoping Review” in Anesthesia and Analgesia (2024) highlights that elevated renin levels correlate with a higher risk of hemodynamic instability (1).
Risk Stratification
- Serum renin levels can help stratify patients based on their risk of adverse outcomes. Elevated renin levels may necessitate closer monitoring and more aggressive management.
Guiding Fluid Therapy
- Renin levels can help tailor fluid therapy in perioperative patients. For instance, patients with low renin levels may benefit from fluid restriction, while those with high renin levels may require fluid resuscitation.
Optimizing Blood Pressure Control
- Monitoring renin levels can help optimize blood pressure control in hypertensive patients undergoing surgery. Adjusting antihypertensive medications based on renin levels can improve blood pressure management.
Identification of Renin-Dependent Hypertension
- Measuring renin levels helps differentiate between renin-dependent and renin-independent hypertension, guiding targeted treatment strategies.
Prognostic Marker
- Elevated renin levels have been associated with increased mortality and adverse outcomes. The research article “Association of Active Renin Content With Mortality in Critically Ill Patients: A Post hoc Analysis of the Vitamin C, Thiamine, and Steroids in Sepsis (VICTAS) Trial” in Critical Care Medicine (2024) demonstrates that Day 3 renin levels are promising as a prognostic biomarker in sepsis-associated ARDS patients (2).
Implications for Patient Care
- Targeted Interventions: Patients with high renin levels may benefit from treatments such as angiotensin II administration. The clinical trial “Renin and Survival in Patients Given Angiotensin II for Catecholamine-Resistant Vasodilatory Shock” in American Journal of Respiratory and Critical Care Medicine (2020) suggests that angiotensin II can improve outcomes in such patients (3).
- Monitoring and Management: Close monitoring for patients with elevated renin levels is essential. This monitoring helps guide fluid management and blood pressure control strategies.
Perioperative Considerations
Renin-Angiotensin System Inhibitors (RASi)
- Preoperative continuation of RASi has been associated with reduced 30-day mortality in cardiac surgery patients, as detailed in the study “Perioperative use of renin-angiotensin system inhibitors and outcomes in patients undergoing cardiac surgery” published in Nature Communications (2019) (4).
- Postoperative use of RASi may improve long-term survival in cardiac surgery patients, according to “Perioperative Renin-Angiotensin System Inhibitors Improve Major Outcomes of Heart Failure Patients Undergoing Cardiac Surgery: A Propensity-Adjusted Cohort Study” in Annals of Surgery (2023) (5).
Cardiac Surgery
- The perioperative use of RASi has shown potential benefits in heart failure patients undergoing cardiac surgery (5).
Non-Cardiac Surgery
- Ongoing trials are investigating the impact of RASi continuation versus discontinuation before major non-cardiac surgery. The protocol of such trials is outlined in “Impact of renin-angiotensin system inhibitors continuation versus discontinuation on outcome after major surgery: protocol of a multicenter randomized, controlled trial (STOP-or-NOT trial)” published in Trials (2019) (6).
Research Summary
- The study by Gleeson et al. ([1]) provides valuable insights into serum renin’s role in critically ill patients, particularly noting that serum renin measured early in ICU admission was associated with Major Adverse Kidney Events (MAKE) at discharge, including mortality. This underscores the potential of serum renin as a prognostic marker in the perioperative period. The study’s strength lies in its multicenter design and prospective nature, although it focused primarily on ICU patients rather than specifically on perioperative cases.
- The research by Gleeson et al. ([2]) highlights that renin can serve as a marker of tissue perfusion and outperform lactate as a predictor of ICU mortality. The study found that renin measurement was not significantly affected by diurnal variation, continuous renal replacement therapy, or drugs, making it a reliable marker in the perioperative setting. However, the study’s limitation is the relatively small sample size of 20 patients.
- The article by Woodcock ([3]) focuses on fluid management in general but does not specifically address serum renin in the perioperative period.
- The review by Wiedermann and Joannidis ([4]) discusses fluid management and the use of human albumin solutions but does not specifically address serum renin.
References
- Gleeson, M. et al. “Serum renin and major adverse kidney events in critically ill patients: a multicenter prospective study.” Critical Care (London, England), 2021.
- Gleeson, M. et al. “Renin as a Marker of Tissue-Perfusion and Prognosis in Critically Ill Patients.” Critical Care Medicine, 2019.
- Woodcock, T. “Fluid management: An update for perioperative practitioners.” Journal of Perioperative Practice, 2021.
- Wiedermann, C.J., Joannidis, M. “Phases of fluid management and the roles of human albumin solution in perioperative and critically ill patients.” Current Medical Research and Opinion, 2020.
